^ THf \ O LIBRARIES Z ITEALTE Digitized by the Internet Archive in 2010 with funding from Open Knowledge Commons http://www.archive.org/details/unitedstatesarmOOunit UNITED STATES ARMY X-RAY MANUAL UNITED STATES ARMY X^RAY MANUAL. r AUTHORIZED BY THE SURGEON-GENERAL OF THE ARMY Prepared under the Direction of the Division of Roentgenology [219 illustrations] NEW YORK PAUL B. HOEBER 67 69 EAST 59TH STREET I918 Copyright, 1918 ByPAULB.HOEBER Published, October, 1918 L\ \ O X)^.Cf< orVnc^YV_ .\ (_LO^ f I u Printed in the United States of America CONTEXTS Introduction 13 1. X-Ray Physics . 15 2. Laboratory Experiments 133 3. New Apparatus 149 4. Standard Positions . 188 5. Dangers and Protection 194 6. Fluoroscopy 202 7. Localization 209 8. Bones and Joints 292 9. Sinuses and Mastoids 346 10. Teeth and Maxillae , 357 11. Thoracic Viscera 369 12. Urinary Tract . 419 13. Gastro-Intestinal Tract 434 14. IMeasurement of X-Ray Dose 463 15. Cutaneous X-Ray Therapy 469 16. Synoptical Table of Contents . 487 17. Index .... . 493 LIST OF ILLUSTRATIONS FIG. PAGE 22 25 26 29 33 33 34 36 1. Generator on open circuit ...... 2. Simple electric circuit ...... 3. Current-time curve of a simple a.-e. circuit 4. Regular gas containing tube ..... 5. Coolidge cathode construction ..... 6. Coolidge tube ........ 7. Wiring diagram for Coolidge filament transformer . 8. Eadiator type of Coolidge tube .... 9. Current and voltage curve for self -rectifying Coolidge tube ......... 10. Variation of size of shadows of small objects with a wide focus tube ........ 11. Current-voltage lines of Coolidge tube for fixed filament temperatures ........ 12. Relation between kilovolts and spark gap . 13. Protection from surge by use of a lamp ... 14. Consumption of voltage by primary of x-ray transformer and series resistance ...... 15. Rheostat construction and connections 16. Theoretical chart line ...... 17. Wiring diagram of autotransformer .... 18. Relation of x-ray production on rheostat and autotrans former control ....... 19. Partial ''chart" of a particular machine with rheostat control ......... 20. Partial ' ' chart ' ' of the same transformer using autotrans former control ....... 21. Wiring of ''polarity" switch ..... 22. Principle of polarity indicator ..... 23. Principle of rotary converter ..... 24. Relation between d.-c. voltage supplied and a.-c. voltage delivered ........ 25. Secondary circuit for four arm rectifier 26. Secondary circuit for two arm rectifier 27. Secondary circuit for disc type of rectifier 28. Relation between an electric current and its resulting magnetic field ....... 29. Arrangement for constant resistance between filament transformer and Coolidge filament 30. The path of negative charge from line through spark gap, tube and milliammeter » . . . . 7 37 39 43 46 48 50 51 53 54 56 59 60 61 62 63 65 65 66 73 74 8 LIST OF ILLUSTRATIONS FIG. PAGE 31. Simple primary circuit, rheostat control .... 76 32. Addition of reversing switch (polarity changer) 33. Magnetic control-switch added 34. Time switch added 35. Multiple primary taps added 36. Autotransformer instead of multiple primary taps . 37. Fundamental diagram of x-ray machines . 38. Use of a lamp in trouble hunting .... 39. Softening and raising connections on Snook hydrogen tube 40. Storage battery charging ...... 41. Emergency rheostat for control of primary of x-ray trans- former ......... 42. Emergency use of 10 ampere fuse wire 43. Valve tube 44. Vacuum tube oscilloscope ...... 45. Operation of induction coil with mercury interrupter 46. Operation of induction coil with electrolytic interrupter 47. Centrifugal jet mercury interrupter .... 48. ''Eotax" interrupter . . . . 49. Oscillogram — induction coil current with a gas mercury interrupter ........ 50. Oscillograms — induction coil currents with Wehnelt in- terrupter ........ 51. The relation between exposure and density of a photo- graphic plate ........ 52. Finding speed factor of intensifying screen 53. Viewing box ........ 54. Simple arrangement of light for developing 55. A convenient darkroom arrangement .... 56. Wooden developing tank 57. Simple ventilator for darkroom 58. Eecord and report form for x-ray examination . 59. Diagram of connections of instruction unit 60. Machine used for instruction purposes 61. Effect of scattering on undercutting of image . 62. Standard U. S. Army x-ray table (Base Hospital type) 63. Standard U. S. Army x-ray table (Portable unit type) 64. Framework of standard army x-ray table and operating pull switch ........ 65. Details of tube box, cradle and shutter 66. Mounting of standard type tube in army x-ray table 67. Tube box and mount for radiator type tube 68. Screen-carrying mechanism ..... 69. Method of handling screen and shutter 70. Measurement target-screen distance, standard screen car- rier ......... 71. Method of centering tube in box .... 72. United States Army portable x-ray unit complete LIST OF ILLUSTRATIONS 9 FIG. PAGE 73. Wiring diagram for United States Army portable x-ray unit 168 74. Instrument box for portable unit, front view . . .172 75. Instrument box for portable unit showing instruments, high tension terminals, and openings for connections . 174 76. Connections for red lamp over the fluoroscopic table, when used with portable or bedside unit . . . . . 177 77. United States Army bedside unit . . . . .178 78. Position of parts when using the bedside unit for chest examination at the bedside . . . . . .180 79. Eotary converter used for d.-c. operation of the bedside unit 181 80. Wiring diagram of connections, United States Army bed- side unit for 110-220 volt d.c. or 110 volt a.c. ' . .182 81. Wiring diagram of connections United States Army bed- side unit for 220 volts a.c 183 82. Position for (a) clavicle (b) shoulder joint . . . 188 83. Position for elbow, lateral view ...... 189 84. Position for elbow, anteroposterior view .... 189 85. Position for wrist, anteroposterior view .... 189 86. Position for wrist, lateral view 189 87. Position for hip joint, anteroposterior view . . . 190 88. Position for knee, anteroposterior view .... 191 89. Position for knee, lateral view 191 90. Position for ankle, anteroposterior view .... 191 91. Position for ankle, lateral view 191 92. Position for foot, anteroposterior view .... 192 93. Position for foot, lateral view ...... 192 94. Position for posterior portion of os calcis .... 192 95. Eesuscitation from electric shock ..... 200 96. Dessane's fluoroscope attached to the head ready for ex- amination ......... 203 97. Dessane's fluoroscope elevated to the top of the head after the fluoroscopic examination ...... 204 98. Method of distinguishing between skin marks and denot- ing depth of foreign body from skin marker . . . 211 99. Apparatus for Method A 220 100. Principle of Metliod A 221 101. Successive appearances on fluoroscopic screen in Metliod A 223 102. Euled celluloid sheet to indicate equality of displacement of two shadows in Method B 225 103. Parallax localizer 226 104. Principle of parallax metliod . . . ... 227 105. Apparatus for Method B ...... . 228 106. Principle of single tube shift method .... 231 107. Wall meter or indicator for tube shift method . . 232 108. Apparatus for Method C . 235 109. Use of double slider caliper in measuring target-screen distance — Method C 237 10 LIST OF ILLUSTRATIONS FICJ. PAGE 110. Principle of profondometer strip . » . - . 239 111. Hirtz compass „ 242 112. Schematic drawing of Hirtz compass with legs adjusted at zero points and resting on a plane .... 24:3 113. Arms and indicator of Hirtz compass, same position but with legs elevated on blocks ...... 244 114. Schematic drawing of Hirtz compass set up on skin of patient 245 115. Hirtz compass in position . . . o , . . 246 116. Eeason for shift of leg of compass from zero point . 247 117. Accessory apparatus for fluoroscopic work with Hirtz compass .......... 248 118. Method of using fluoroscopic adapter wdth Hirtz compass. 251 119. Setting arms and legs of Hirtz compass directly from fluoroscopic adapter ....... 253 120. Detail of holder for direct setting of Hirtz compass . . 255 121. Direct setting of Hirtz compass. Compass and holder in position 257 122. Centering of tube above plate holder on cassette with small cross wires, photographic method, Hirtz compass 259 123. Skin markers, plate holder and tube holder in position for photographic method, Hirtz compass . . . 260 124. Schematic representation of plate, cross wire marker and tube focus positions for radiographic use of Hirtz com- pass 262 125. Construction for finding foot points 262 126. Complete chart for setting feet of Hirtz compass . . 264 127. Equipment supplied for use with Hirtz compass . . 267 128. Apparatus for Method F 268 129. Use of MetJiod F with a perforated screen .... 269 130. Set of localization accessories supplied in the regular army outfit ......... 271 131. Intermittent control. Eoentgenologist w-ith fluoroscope, raised ready to lower it and proceed with examination . 273 132. Intermittent control. Surgeon and roentgenologist work- ing simultaneously ........ 273 133. Head rest for use with the eye localizer .... 279 134. Sweet eye localizer ........ 280 135. Position for first exposure in localization of projectiles in the eye .......... 283 136. specimen plate of projectile in the eye illustrating the method of measurement ....... 284 137. Second exposure for localization of projectiles in the eye . 285 138. Schematic drawing of localizing chart illustrating the method of obtaining measurements .... 286 139. Chart used in eye localization ...... 287 140. Position for examination of frontal region of skull . . 307 141. Position for examination of temporoparietal region of skull 308 LIST OF ILLUSTRATIONS 11 FIG. PAGE 142. Position for examination of posterior (occipital) region of skull 309 143. Position for examination of basilar region of skull . . 311 144. Positions for examination of spine ..... 314 145. Spine examination, anteroposterior position for upper cer- vical vertebra' ......... 316 146. Spine examination, anteroposterior position for lower cer- vical vertebra? . . . . . . . .317 147. Spine examination, lateral position for examination of cer- vical vertebnie ........ 317 148. Spine examination, anteroposterior position for thoracic vertebra? ......... 318 149. Spine examination, position for lateral examination of thoracic vertebrae . . . . . . . .319 150. Spine examination, anteroposterior position for upper lumbar region . . . . . . . .319 151. Spine examination, lateral position for lumbar vertebrae . 321 152. Spine examination, anteroposterior position for lower lumbar vertebrae . . . . . . . .321 153 and 154. Position for mastoid examination .... 347 155. Schematic drawing illustrating correct angle for postero- anterior accessory sinus examination .... 349 156. Position for postero-anterior examination of accessory sinuses .......... 350 157 and 158. Position for lateral examination of accessory sinuses 351 159. Position for examination of sphenoid sinus . . . 353 160. Position of patient, film and tube for exposure of upper molar region . . . . . . . . .358 161. Adjustment for exposure of upper bicuspids, canine and lateral incisor ......... 358 162. Adjustment for exposure of lower molars .... 359 163. Adjustment for exposing "ower bicuspids, canine, and lateral incisor . . 359 164. Normal teeth except for unerupted canine . . . . 360 165. Localized areas of destruction of alveolar margin . . 361 166. Sarcoma of mandible ........ 362 167. Acute abscess 362 168 Multiple chronic abscesses ....... 363 169. Advanced pyorrhoea 364 170. Abscesses, involving unerupted teeth .... 366 171. Adjustment for exposure of anterior portion of upper jaw .......... 366 172. Adjustment for exposure of anterior portion of mandible 367 173. Adjustment for exposure of posterior two-thirds of man- dible, the articulation of the jaw, and the zygoma . 367 174. Adjustment for exposure of upper jaw . . . . 368 175. First oblique position for chest ...... 370 176. Second oblique position ....... 370 177. Third oblique position 371 12 LIST OF ILLUSTRATIONS FIG. 178. Fourth oblique position .... 179. Dorsoventral (postero-anterior) position for chest 180. Lateral recumbent position for chest 181. Normal heart (orthodiagram) 182. Mitral insufJficiency 183. Pure mitral stenosis . 184. Aortic insufficiency 185. Atheroma of the aorta 186. Drop heart .... 187. Large pericardial effusion . 188. Chest plate made for examination of the heart 189. Type of tracing furnished clinician with report 190. Planimeter 191. Examination of upper half of urinary tract 192. Position for upper half of urinary tract . 193. Position for lower half of urinary tract 194. Position for bladder and prostate 195. General view" of patient on table 196. Diverticulum of esophagus 197. Benign stricture of esophagus . 198. Carcinoma of esophagus at level of bifurcation of trachea 199. Cardiospasm; note marked dilatation of esophagu 200. Penetrating ulcer on lesser curvature of stomach 201. Excavating ulcer of lesser curvature 202. Marked dilatation of stomach due to obstruction at py- lorus ........ 203. Large carcinoma of stomach .... 204. Carcinoma of stomach, moderate size 205. Duodenal ulcer, showing defect in duodenal bulb 206. Mucous colitis shown by stringy shadow of the barium 207. Diverticulitis of colon 208. Carcinoma of ascending colon . 209. Carcinoma of hepatic flexure 210. Carcinoma of cecum .... 211. Dyschezia; note dilatation of rectum 212. Angulation at duodenojejunal junction 213. Appendix ...... 214. Incompetency of ileocecal valve . 215 Gall-stones ...... 216. Dosage curve for various spark gaps . 217 and 218. Five areas and angles of incidence of rays 219. After depilation by Adamson method INTRODUCTION THIS manual has been prepared under the direction of the Surgeon General of the Army to serve as a guide to roentgenologists who are doing the x-ray work in our military hospitals, and as a textbook for instruction in mili- tary roentgenology. It will supersede the small U. S. Army X-Ray Manual which was hurriedly prepared at the beginning of the war to facilitate the instruction of the many inexperienced men who, of necessity, had to be trained to do x-ray work. The manual is not intended to be a complete treatise on roentgenology, but in the portion devoted to x-ray diag- nosis the aim has been to state as concisely and clearly as possible the facts that have been established by ex- perience, and to avoid all controversial points. There is, of course, no clear line of demarcation between military roentgenology and roentgenology^ of civil practice. It is the same art, but practiced under different circum- stances and, sometimes, with an entirely different type of apparatus. The principal aim in the preparation of this manual and in the courses of instruction carried on by the Medical Department has been to familiarize the already experienced roentgenologist with the apparatus with which he is to work, and to give him additional instruction along any lines in which he may be deficient. The need for a large number of roentgenologists, however, has rendered it necessary to train for this work physicians who have had little or no previous experience and, for this reason, it has been necessary to cover in the manual practically all phases of roentgenology. 13 14 INTRODUCTION The parts of the manual devoted to the localization of foreign bodies and to a description of new apparatus deserve special attention. The localization of foreign bodies occupies most of the roentgenologist's time in the forward hospitals, and he must thoroughly master the methods described. The new apparatus described in Chapter III has been developed either just preceding or subse- quent to the entry of our country into the war. It differs in many respects from the apparatus in use in civil hos- pitals. Some of this new apparatus, such as the port- able and the bedside unit, have certain limitations. These must be recognized and must not be exceeded. It should not be concluded, however, that because there are certain limitations the apparatus is of little value. For instance, the maximum current to be obtained from the bedside ap- paratus is five milliamperes, but this low milliamperage is rendered very effective by the constant and properly selected voltage and the quality of the plates resulting from the fine focus of the special type of Coolidge tube employed. For bedside work in many of our large hospi- tals this apparatus has been found invaluable. The great importance of the x-ray in military surgery and medicine has been established so that the roentgenolo- gist has a position of much responsibility. He must re- member, however, that his work is valuable only in so far as he assists the physician or surgeon in arriving at cor- rect conclusions, and that this can be accomplished only by mutual cooperation. The roentgenologist does his part by presenting to the surgeon accurate findings carefully recorded in a usable form. After he gains the confidence of the surgeon in the accuracy of his work and the sound- ness of his judgment, the exercise of a little tact will alwaj^s make it possible for him to secure full cooperation and thus give to the x-ray examination its maximum value. UNITED STATES ARMY X-RAY MANUAL X-RAY PHYSICS Introduction. — The following brief notes on the phys- ical aspects of the apparatus likely to be used in military roentgenology have been written with the hope that their study might enable the roentgenologist to prepare for service in less time and be better able to utilize the appara- tus with which he is compelled to work. AYith the belief that brief reasons as to why things are done are good guides in operation, rather more explanation of fundamen- tal principles has been given than is usually included. X-Rays. — The roentgen or x-rays are produced by an el ectri c current in a glass-walled vacuum tube. Such a^ current is due to the projection of minute ele ctric part icles (e lectron s) from one metal terminal, the cathod e, to an- other metal terminal, the anode or target. The x-rays ori ginate at the point of impact of the el ectro ns on the target and travel out fromtheir origin i n all d irections exi^t where, dense material obstructs o r preven ts thei£ pass age. When passing through bodies made up of various parts differing in density, some of the rays that enter the denser portions are permanently cut out and a new distribution of intensity in the beam results. The presence of x-rays must be determined by some of ^^ ^ 16 U. S. ARMY X-RAY MANUAL the effects they produce when acting on ^materia l bodies. These actions are : 1. Effect on the emulsion of a photographic plate. 2. Excitation of light in certain crystals (fluorescence). 3. Rendering gases conducting to electricity (ioniza- tion). 4. Stimulating or destructive action on living cells (biolog ical action). ^ Ti^ first, second, and fourth of these are of fundamental value in the medical and surgical^ uses of the rays. The , - third has been very useful in the stud y of the radi ation. ^ ■^^<<^^^\iese rays do not excite vision on reaching the retina \of the eye, but are capable of originating light in cer- A uniform beam, falling on a piece of covered with such crystals, would cause uni- rr^^ -^form illumination. If regions of_unequal material den- L^..J' sity^^have_ been traversed by the beam before reaching '***'***^'^he^screen (fluproscope), such dense portions will show as areas of lesser brightness or^^ as we say, will cast shad- . ow^ Injbhe same way, a photographic plate or film suffi^ ciently acted upon by such rays will, on development^give areas of unequal blackening, marki ng out the projections^ of volumesin^e body whose densities differ from those__^ ''^^l^j^;- surrounding them. On the flio^roscopic screen7dense bodies •^ '/ -^shQw as dark areas; in a photographic negHive, they show i^^ />-*uUc-*^^ i and^out of material bodies, except where the a toms t hem- rci^. > selves cause__scattering. They cayinot be directed by mir- rors or lenses for purposes of optical focus or^ concentra- tion, as is done with light. The slight amount of regular reflection by the uniformly spaced atoms in crystals is too smalPto be of any importance to the roentgenologist. Velocity. — The rays travel out from the target at the same velocity as light or electric waves. Energy. — The actual energy involved in an x-ray beam is small compared with that expended in getting it started ; only a few parts in a thousand of the energy supplied is converted into x-rays. Scattering. — X^^ra^ are scattered in pas,sing_through matter exactly as light is scattered in turbid wate r, fog, 18 U. S. ARMY X-RAY MANUAL paraffin, etc. Only a part of a beam is thus scattered, the remainder passing straight through or being absorbed. Scattering confuses shadows on screen or plate in a very troublesome way. Passage Through Matter. — When rays p ass through m a- terial, the substance is call ed transparent to the radia- tion. If^litt le or no radiation get s jthrough, we say the material is opaque_to this radiation. The terms transpar- ent and opaque_refer to the action of the material with reference to a specific type of radia tion. If one arranges a YSLviety of substances of like thickness in the order of increasing density, their opacity to x-rays will be nearly in the same order. But this will vary somewhat according to the quality of the x-ray beam considered. That portion of the incident radiation neither transmitted nor scat- tered is changed into heat or, as we say, absorbed in the material. We then say that absorbing power increases with the density of the absorber. This absorbing power is best expressed as the fraction of the rays absorbed by a definite thickness of material. Thus, if 1 cm. of water should reduce a particular radiation so that the emerging beam is half as effective as the entering one, we might say this radiation has a half value layer of 1 cm. of water. Two centimeters of water would transmit only 25 per cent of the incident beam or that reaching the surface proximal to the tube. it f^i/YjU^ The quality of short wave length and high penetration i^J^j'can be secured only by means of high voltage operation. /'^'V, (See penetration, p. 46.) i h ^ Electrons. — The modern concept of atoms involves the Hr €»^*^ idea of their general electrical constitution. From any ^^j^a^'^ dXQTii there may be abstracted one or more small negative i^>wt.i2i^harges, all precise ly alike, whose properties are in -no wise X-RAY PHYSICS 19 dependent on the at om froi n which they conie,^nd all are. quite capable of existence by themselves without jthe pres- ence oT the remainde r of the atom. These little bodies have been variously named as corpuscles, cathode ra^^s, beta rays, electric-ions, etc. The common designation of elec- tron is derived from the latter. A n ele ctron i s able to respond to electric force and to ac quire velocity und er such fo rce act ion. When in motion, they show al l the charac- teristics of an e l ectric curr ent. The m ain ph ysical ^features of elect rons ^ arej_ 1. Their_ _fixed and_ definite_^egativ^ charge. 2. Their extremely small mass a nd volum e. 3. The extreme speed they m ay acquir e. Production of X-Rays. — Roentgen or x-rays originate in any region where the velocity of electrons is suddenly changed. In the radio-active breakdown of atoms, this change is a sudden acquisition of velocity, and the gam- ma rays are produced. In x-ray tubes, the high-speed electron is stopped in its flight by the interposition of a target metal of high atomic Aveight placed in its path, and x-rays result from a loss of velocity. T he pr oblem of x-ray production for our purpose, then, resolves itselT into four parts._ 1. The separation of electrons from atoms. 2. Giving them high speed. 3. Concentrating them on a small area. 4. Stopping them with sufficient suddenness. The first of these is accomplished in one of two ways. In the tu bes containing a small amou7it__ ot^as, electrons a re secured in pai l^bg - hi gh electric fiel d, b ut to a much g rgeater ext ent b v the disrup tion of atoms du e^ to the m ov- ing electrons and by the x-rays themselves. In the more 20 TJ. S. ARMY X-RAY MANUAL ^^<£^. recent hot cathode tube (C ^olidge ), el ectrons are set free * ii^^^yy^f rom the atoms in a tungsten wire by t he action of heat. iii*i«^^In the former, the number of available electrons is rather '■^^L ^hard to control, while in the hot cathode tube this offers ^ou/tuiJ^ difficulty. In o^r^£^to sec ure high speed_ (one-half to o ne-th iji^ the velocity of light) a high voltagemust be avai lable , ana -fclTe electro ns must a ll be urged towar d the same s mall area in order to get sharp s hadows 7"""The^ co ncen t^atTon on the target is secured by proper design of the elec- trodes and their ^ pro per position in the tube. In all cas es the path to_^be^ followed must be quite freeof gas in order to avoid obs truct ion. " The choice of metal as a barrier is of great importance, and only a few elements satisfy the conditions. Every fast-moving electron has so me m echanical energy and this g oes mainly in to heat by i mpact ; the re resu lts a^reat rise in temperature at the _p oint of e lectron concentration . As radiographs and fluoroscopic images arepurely shadow effects,^a source of radiation sfartingjrom a point is very desirable^. This high concentration of heat will melt any target material at high power operation. Only metals of high melting points can be utilized, such as platinum, tungsten, osmium, and iridium. Of these the first two are in common use, the tungsten to a great extent during recentyears. Hi^ atomic we ight is also de s irable, a nd fortunately this goes with high melting points in the a^oye metals. General Instructions and Precautions. — 1. Excessive ex- posure to x-rays results in serious injury to the skin. Such injury does not manifest itself at once but may develop some weeks later. To a degree, the action is cumulative, so that a single dose, in itself too small for X-RAY PHYSICS 21 injury, may, when frequently repeated, be harmful. Read carefully the notes as to protection, page 19i. AVhile it is unwise to be over timid, it is much easier to prevent an injury than to cure it. 2. X-ray apparatus is expensive, and not only is it costly in money to repair damage, but even more impor- tant is loss of service from breakdown. Do not try to see how much current you can pass through a tube or how long a spark the transformer will give. Do not imagine that a tungsten target cannot be melted j it can, and very quickly. 3. Acquire the habit of observing whether high ten- sion wires are sufficiently far from patient, assistants, etc., before you close the operating switch. 4. Make all tests of tubes, etc., on low power, when possible, and do not make unnecessary speed your ambi- tion. AYhen through work, throw all controls to low power. 5. Never test out a tube when the patient is in posi- tion. 6. Always see that current is passing through the fila- ment of a Coolidge tube before closing the main trans- former switch. 7. Do not imagine you can make plates of thick parts on very low spark gaps. It cannot be done, but you may get some very unfortunate experience trying it. 8. Remember that any current that passes across the spark gap or leaks from one line to the other along walls, etc., does not help to produce x-rays, although it may in- crease your milliammeter reading. 9. Try to develop a definite order and sequence in the various details of any examination. It will save time and prevent errors. 22 U. S. ARMY X-RAY MANUAL 10. The only safe time to label a plate or film for identification is at the time of exposure. 11. Don't imagine that so and so's good plates are due to the particular machine he is using; and don't chase off after every new exposure ''technique" you hear about. The fact that some individuals advocate one after another is ample evidence of their uselessness. Electrical Terms. — Certain terms are used so frequently in all discussion of electrical matters that they are intro- duced at this point for convenience in reference. Charges. — AVhen any physi- cal or chemical action breaks down the connection between an electron and the remainder of the atom, the electron consti- tutes the elementary particle of negative electricity. All nega- tive charges are simply countless numbers of electrons kept awav from the positive portions of the atoms from which they were separated. Generators. — Generators do not create electricity. They take electrons and positive ato- mic remainders apart and push them in opposite directions against their natural tendency to keep and come together. Thus, if G, Fig. 1, represents a generator, A and B metal- lic plates connected to its terminals, A is covered with elec- trons and B with enough positive to neutralize the negative on A, If we call e the negative charge of one electron, and Q the total charge on A, N the number of electrons, then Q equals Ne, where N is an incredibly large number in most cases. Fig. 1. Generator on open circuit. X-RAY PHYSICS 23 Voltage. — Electric charges separated as shown in Fig. 1, show: (1) a mechanical pull on the bodies A and B, (2) a decided tendency to pass between A and B. A voltmeter does not measure electricity but something like a pressure or strain trying to pass a charge between two regions. The Volt. — The volt is the unit in which the tendency of charge to move from one place to another is measured. The electrical tension between the terminals of a special cell (Weston or Cadmium cell) is taken by legal definition as 1.019 volts. Current. — AYhen proper external connections are made to the terminals of a generator there results a transfer of charge. If we could coiint the number of electrons passing on to A per second, say n, we would call 7ie the current passing through G. An electric current may then be regarded as a measure of the number of electrons pass- ing per second. It must be observed that after A and B are charged as highly as is possible for the particular gen- erator, there will be no further current, but the voltage is present. We may have voltage existing and no current, hut never a current without some voltage. The Ampere. — The ampere is the unit of electric cur- rent. It is legally defined as the rate of transfer of electric charge which deposits silver from a special solution at the rate of .001118 grams per second. The unit electric charge is the coulomb. Five amperes, for example, will transfer 40 coulombs in 8 seconds. Resistance. — It requires but little voltage to move a big supply of electrons through some materials, while with others a very great voltage will cause but little electron movement. The former are named conductors; the latter, insulators. Note carefully that the difference is one of 24 U. S. ARMY X-RAY IMANUAL degree, and that perfect insulators do not exist so far as high applied voltage is concerned. Thus, dry, clean glass may be considered an insulator for moderate voltages, but may conduct to a considerable extent at high voltage. The objection offered to the passage of an electric current by any material included in a circuit is called its resist- ance. The Ohm. — The unit of electrical resistance. Legally defined as the resistance of a uniform column of mercury 106.3 cm. long and one square millimeter section at 0° centigrade. Power. — The ability of the electric current to do work is termed its power. The Watt. — The watt is the unit of electrical power. It is the power of a current of 1 ampere in a region where it loses 1 volt. The product, amperes x volts lost = power in watts ; 746 watts are equivalent to one mechanical horse- power, and 1 kilowatt is therefore equal to about 1% horse- power. Derived Units. — The units given above are not of con- venient size in all cases, and some modifications are in common use. The terminal voltage on the tube is high, and it is often expressed in kilovolts (1 kilo volt equals 1000 volts). The current ordinarily used through x-ray tubes is small and is expressed in milliamperes (1 milli- ampere equals y^^ ampere). The power used to oper- ate electrical devices is generally expressed in kilowatts, when the number of watts is large (1 kilowatt equals 1000 watts). One kilowatt maintained for one hour is named a kilowatt-hour. As applied in particular cases, a 4 kw,, 110 volt gen- erator, is a machine that delivers 4000 watts at full load and is designed to operate at 110 volts. The full load "T^Jt ^ X-RAY PHYSICS 25 current would be ^^^-^ = 36.3 amperes. If a machine gives 50 milliamperes at 70 kilovolts, the power delivered is ^Aa^ X 70 X 1000 -= 3500 watts, or 31/^ kw. Measuring Instruments. — The electrical measuring in- struments that may concern the roentgenologist are the ammeter and the voltmeter for low tension circuits, the milliammeter, and the kilovoltmeter for high tension cir- cuits. Most kilovoltmeters are of little real value as they vary with the secondary current. The milliammeter is a most valuable aid to the work. It is often designed for two iq Ohms Q — ^/\A/\/\/v^^^ Fig. 2. Simple electric circuit. ranges. From to 15 ma. on one scale and to 150 ma. on the other is the best for most work. Do not try to draw 150 ma. when the meter is set for a maximum of 15 ma. If the pointer gets bent, due al- lowance must be made in reading. Electric Circuit. — An electric circuit consists of some sort of a generator and a more or less complex conducting path between its terminals. Electricity outside a gener- ator always passes from high to low voltage, and the cur- rent may properly be said to lose voltage en route from one generator terminal to the other. Consider a very simple circuit, Fig. 2, consisting of a generator, G; generator resistance one-tenth ohm, two other 26 U. S. ARMY X-RAY MANUAL resistances as shown. The fundamental law of such a circuit is that if when the switch, S, is open we have, say 220 volts, then for any total resistance, B, we will have a current, on closing S, such that Current x total resistance = 220, or in this case, No. of amperes x (.1 + .9 + 19) = 220 Current, / = 220 = 11 amperes. W The voltage is used up as follows: In the generator 11 x .1 = 1.1 volts Between A and B 11x19 = 209.0 Between B and C 11 x .9 = 9.9 Total 220.0 volts Tig. 3. Current-time curve of a simple a.e. circuit. This relation is true for all circuits, viz., volts lost due to resistance of B ohms when a current of I amperes is flowing = I B. Direct Current (d.c). — When the electron-flow is in only one direction, the current is named direct. Dry cells, storage batteries, static machines, and d.-c. dynamos deliver X-RAY PHYSICS 27 direct current. A current may be intermittent or pulsat- ing, and still be called a direct current. Alternating Current (a.c). — When the electrons flow in one direction for a short time and then the flow de- creases and a reverse flow occurs, we say the current is alternating. A.-c, dynamos are the only sources of true alternating current. Such a current in its simplest form may be pictured by a suitable time-current diagram. In Fig. 3 time is shown as increasing from left to right. Let OC = second 60 Then OC =BD =CE =P^ P^ =-^ second This current takes all its variable values once in 1/60 of a second, and repeats the operation 60 times in one second. It is designated as 60 cycle a. c. If drawn from a 220 volt service, its complete designation is 220 volt — 60 cycle — alternating current of a certain number of amperes. During the times OB, CD, EF, etc., current flows in the opposite sense to that during the times BC, DE, etc. Note that there are two alternations to each cycle, or 120 per second in this case. X-Ray Current-Voltage Requirements. — At present x- ray tubes are used with currents varying approximately between 5 and 100 milliamperes, and at voltage running between 25 and 100 kv., i. e., 25,000 to 100,000 volts. This high voltage requirement cannot be met by simple d.-c. gen- erators. High Voltage. — The requisite voltage is secured by the use of: 28 U. S. ARMY X-RAY MANUAL 1. The so-called static machine (direct but impractical). 2. The periodic interruption of a direct current through one coil, causing high voltage in a neighboring coil (in- duction coil). 3. Using a low voltage alternating current in one coil and getting a high voltage alternating in an adjacent coil (transformer). The second device is still used to some extent, but has largely been displaced by the transformer in recent years. The use of an induction coil or a transformer to in- crease voltage involves two distinct circuits, one connected through some control device to the supply line or genera- tor, and known as the primary circuit ; the other, insulated from the primary and connected to the tube terminals, known as the secondary circuit. The primary always : Is of relatively low voltage. Is a moderately large wire. Carries a current of some amperes. Is reasonably safe to touch. Requires good metallic contacts at all connections. The secondary always: Is high voltage. Is quite a small wire. Carries a current of some milliamperes. Is unpleasant and often dangerous to touch. "Will pass current across loose connections or even through some insulating material. The induction coil and a few transformers have both coils wound on hollow concentric cylinders, the primary within the secondary, and the space inside the primary coil is filled with thin iron sheets or wires. These are named open magnetic circuit devices. Most transformers now in use have the iron in the form X-RAY PHYSICS 29 of a closed rectangle, and the two coils wound so as to slip on the sides of this rectangle. These are known as closed magnetic circuit transformers. The Gas Tube. — While a great variety of special forms of gas containing tubes have been introduced from time to time, the general form shown in Fig. 4 alone has sur- vived for ordinarv use. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Fig. 4. Eegular gas containing tub€. Negative or cathode terminal. Cathode of aluminum. Adjustable connections for softening. Softening material. Sealing off tip. Auxiliary anode. Copper block. Tungsten button. Positive or anode terminal. Anode neck. Cathode neck. Cathode particles. Path of x-rays. A L M, Anterior hemisphere showing fluorescence. 30 U. S. ARMY X-RAY MANUAL The target material has a great influence on the be- havior of the tube and the quality of the rays. The atomic weight must be high, as the fraction of cathode ray energy transformed into x-rays increases with increase of atomic weight. The melting point must be high or the metal will melt at the focus. It should conduct heat well, and must not vaporize readily below its melting point. The follow- ing table gives the approximate data relating to possible metals for this purpose. Taking platinum as a standard radiator: Amount of Metal At. Wt. X-Radiation Melting Pt Platinum 195.2 1. 1760. C. Iridium 193. .98 2300 Osmium 190.9 .97 2700 Tungsten 184. .91 above 3000 Tantalum 181. .90 2900 The essential features of all modern tungsten target gas containing tubes are shown in Fig. 4. Various minor modifications may be seen in tubes from different mak- ers, but each part shown must be present in some form. The cathodes may differ in shape, but only aluminum gives good results and long tube life. The mounting of cathode and target must be firm, and the position in the neck carefully chosen. The adjustable arm (3) is often absent, and a third wire is run to a variable spark gap connecting with the negative terminal of the machine. The auxiliary anode (6) has a great variety of forms; in many water-cooled tubes, and sometimes in others (6) and (10) are interchanged. Numerous special devices for conducting heat away from the target are in use and are X-RAY PHYSICS 31 more or less effective. For treatment or for long fluoro- scopic examination with this type of tube, water cooling is essential, and a good stream of air directed against the glass adjacent to the cathode is also of considerable as- sistance. A satisfactory tube must have a stable position of anode and cathode ; all attempts to use an adjustable cathode have been unsatisfactory. The metal parts must be pre-heated and the tube itself heated during exhaustion. A well made and properly exhausted tube shows a good hemisphere on the anterior portion, and the remainder of the tube should show but little fluorescent light ; a working tube should not be "flashy" or "cranky." AYlien one attempts to operate a moderately hard tube at too low potential, this unstable state may result and either the voltage must be raised or the tube softened. The vacuum must be within fairly well-defined limits, averaging not far from .001 mm. pressure of mercury, and must be in some manner under control, if the life of the tube is of consequence. The tendency of all gas containing tubes on low current is to "harden," i. e., to require more voltage for the same current, or, if the voltage is not changed, the current de- creases. On operation above a certain power peculiar to each tube, the tube softens on account of heating; when this proceeds so far that the tube shows and maintains a purple gloAV marking out the cathode stream, it is useless until repumped. Many devices have been used to soften tubes. The more common are the following: 1. A side tube containing mica, asbestos, etc., and through which a small discharge current may be sent, thereby liberating gas. (No. 4, Fig. 4.) 2. A special target is placed in a side tube to be bom- barded by rays from a small auxiliary cathode. 32 U. S. AR]\IY X-RAY MANUAL 3. A fine palladium tube projects through the walls of the tube; when this is heated by a small flame it allows hydrogen to pass into the bulb. This has been modi- fied by Snook, where the tube is heated by a spark dis- charged from the operating transformer. 4. Heating the entire bulb. (Useless except in an emergency.) 5. A mercury-controlled porous valve allows air to pass slowly into the bulb when the inlet is not covered by the mercury (Heinz-Bauer). 2, 3, and 4 are rarely used in this country, although 3 (osmosis regulators) are sometimes seen outside the more useful Snook form. The Coolidge Tube. — The great difficulty in the opera- tion of the ordinary gas containing tube lies in the ir- regular supply of electrons and the impossibility of control of their development. When operated above very mod- erate power, the trend is always toward larger quantities of electrons and a consequent drop in penetration, unless the current is greatly increased, when a still greater sup- ply is developed, so that there is no automatic self-pro- tection of the tube. Wehnelt found that a platinum ribbon coated with lime would allow of current transfer through a high vacuum at nioderate voltages. Several attempts to use such a cathode for x-ray tubes were unsuccessful, and no modifi- cation of the standard tube appeared until it was found by Richardson and others that electrons were emitted by hot metals. The simplest application of this principle to x-ray de- velopment has been worked out by Dr. W. D. Coolidge in the Research Laboratory of the General Electric Company at Schenectady. In this tube, the cathode is a spiral filament of tungsten wire, A, Fig. 5, heated to a high tern- X-RAY PHYSICS 33 perature by a current from an insulated storage battery, or by a special transformer. The form of electrostatic field needed for focussing' the electron stream is fixed by a small molybdenum cylinder, B, within which the cathode is placed. The target is usually a solid piece of wrought tungsten mounted on a molybdenum rod, around which collars are placed to distrib- ute the heat conducted from the target. Fig. 6 shows the Coolidge tube. Cathode terminal. 1. 2. 3. 4. 5. Fig. 5. Electron focusing" cone, struction. Coolidge cathode con- Solid tungsten target. Mol^^bdenum supporting rod. Anode terminal. In order to operate properly, it was found that the highest possible vacuum must be attained. Not only was the greatest care required in pumping, but the metal Fig. 6. Coolidge tube. parts had to be freed from occluded gas by heating in a vacuum nearly to their melting point. In this tube there is no source of electrons except from the hot filament, and as this supply depends only on the temperature of the filament, the operator has perfect control of the num- ber of available electrons by simply changing the auxiliary 34 U. S. AmiY X-RAY MANUAL current. A small transformer is now generally used to supply low voltage for the filament current. Connections are as shown in Fig. 7. The winding connected to the filament must be well insulated from case and primary winding. The current through the tube cannot be increased after FILF)MBNT ZZO VOLTS Fig. 7. Wiring diagram for step-down transformer to supply cur- rent for filament of Coolidge tube. the supply of electrons is entirely utilized, no matter how much the voltage is raised. This maximum current for each particular filament temperature is named the satura<- tion current, and until this is reached the voltage main- tained between cathode and target may be too low for use. So long as the negative current reaching the tube does not exceed the number of electrons emitted per sec- X-RAY PHYSICS 35 ond multiplied by the charge of each electron, there can be no charge piled up on the electrodes — i. e., no effective terminal voltage. No Inverse. — A further valuable feature of the tube is its inability to transmit inverse so long as the focal spot is not too hot. On account of the increased strain on the glass, when inverse is present, it is well to include a valve tube when operating on a heavy coil. Penetration Limits. — The highest operating voltage on the present tubes is about 100 kv., as measured on a spe- cial electrostatic voltmeter. This refers to ' ' effective ' ' volt- age; the peak voltage is larger than this. No doubt this can be increased by modification of the design, but insulation difficulties and danger of puncture will be increased as higher voltages are used. Such high penetrating rays as may now be reached are not useful in fluoroscopic work or in radiography, partly on account of the enormous amount of scattered radiation developed in the tissues of the body. Such scattered and corpuscular rays may, however, be useful in therapeutic work. Very soft rays may be produced in great abundance if the glass will allow them to pass out. Attempts to use too soft rays in radiographic work are always fraught with grave dan- ger. No Fluorescence in the Glass. — In marked contrast to the usual tube, there is no fluorescence of the glass walls except a slight illumination in the anode neck. Some- times a minute chip in the glass or a slight evolution of tungsten vapor will give a momentary flash of green, but on further operation at moderate power this disappears. The bombardment of the walls of the tube by electrons reflected from the target or scattered from the gas atoms in the gas containing tube is the cause of the fluorescence and of a very considerable amount of soft radiation 36 U. S. ARMY X-RAY MANUAL originating in the glass. As there is in a gas tube as large a supply of positive ions as of negative, continual recom- bination results, and no negative layer can form on the glass walls to prevent bombardment by scattered and re- flected electrons. In the Coolidge tube the absence of posi- tive ions probably allows the accumulation of a negative charge on the glass, and as soon as established this layer repels electrons and the glass is no longer a target. Nev^ Form of Coolidge Tube. — The o rdina ry form, of Coolidge tubejwill opera,te_satisfactorily withou t a re ctifier if the focal spot is at a tenvg eratii re helo w^thait ai w hich i t gives off an apprecia Me nun^er of electrmis. It follows that part of the problem of eliminating the rectifier is keep- TiG. 8. Eadiator type of Coolidge tube. ing the target cool. A new form of tube which will help greatly in this mode of operation has recently been de- veloped by the General Electric Research Laboratory, Fig. 8. The target is a tungsten button set in a heavy copper backing which is continuous with a large copper rod ex- tending out of the tube neck. To this are attached a series of discs acting as radiators. Operated within limits set by the manufacturers, this tube su^jDresses coi^pletely each alternate half wave and may be^ operated direct on a suitable transformer. At present these are designed for 10 ma. at a 5-inch gap for radiographic work, and for 5 ma. at the same gap for continuous duty in fluoroscopy. The wiring diagram then becomes very simple and easily understood. X-RAY PHYSICS 37 In Fig. 9 are shown a current-time curve and a voltage- time curve for the self-rectifying tube. In the latter O A^fJi^^J^ ^ is th e, working jpeak voltage which determines t he tube radiation , and BC^is t he peak vo ltage of the_suppressed wave ^ w hichwpul d giy e the spark gap reading. A transformer sho uld b e used which will not vary its o,A . '^.e.^ >L.*«.^^i^ i.c/7U:e< -,:;;^ 0,^A^t^ A Fig. 9. Current and voltage curve for self -rectifying Coolidge tube. The voltage difference indicated by the excess of BC over OA will depend on design of transformer and control. voyage too much fro m^jjj jjjurrent to that needed to oper- ate_^it properly, sinc^e t_he^,^ltage of the su ppress ed wave is quite decidedly higher thanjhat oft he one ^used, there- by causing spark-over and giving an incorrect idea of the actual working voltage. The value of this arrangement for field work can hardly be overestimated, as there is no heavy and complicated rectifier. Operated from a small gas engine-driven gen- 38 U. S. ARMY X-RAY MANUAL erator, it is ideal for fluoroscopic work and satisfactory for emergency radiography. See U. S. Army Portable Unit, page 167. yj^^tUh Tube Focus. — The x-ra^ys cannot be focussed by any known method, so that the, terin£ fpcal_j)mntj__etc., are mis- -^iL*jl|leading. Electrons can,j3e^ directed by s^uitable cathode ,^ construction so that the greater portion strike a small area tiA, oiTL the^Jarget. The diameter of this area is known as .|5^the ''focus," and it is customary to speak of broad, me- V^ dium, and fine foci. One can hardly state precise limits ^ between these designations, but anything below 3 mm. ' would be extra fine focus ; 3 to 4 mm. fine focus ; 4 to 7 mm. medium focus; and over 7 mm. broad focus. ^,^1^^'^^he size of focus is^foundjDy the use of , a pin-hole cam- \.j< era, "and ^ould be giyep. by the maker. Its size is im- pKJ^^ j)ortafl,t. in two ways : First in relation to the sharpness '/^^^^^^of^jmage on plate or screen ; second, as fixing the jowe r I 'that may be used wftKout 'damage to the target. When an electron stream is maintained at high velocity against the ^,,t,^)T^^ target, there is a rapid rise in temperature which may ^uutkt result m vaporization or fusion of the metah The rate of removal of heat by conduction is increased by broaden- ing th e focal spot^ and the _ amount of jnetal suffering extreme r ise in temp erature ^s increased, so that for two ^ reasons there is less danger of target damage. r^^^^^ ^ The effect on sharpness of image is shown by using an exaggerated diagram as in Fig. 10. F^ Fg are the bound- aries of the focal spot and 1-2 is the object. With the plate in plane A, had the only source been a point, i^^, a sharp shadow PQ would result; had F^ been the only source, then BS would result. The only portion entirely shaded is BQ, and if the object is round, we have a cen- tral white spot with a variable shading out to a diameter PS. If the focal spot were very wide and the object very iA|Me^< X-RAY PHYSICS 39 small a plane B could be found beyond which there would be no white image. The ring PE and QS is narrower the closer the object to the plate, the smaller the focal spot and the greater the target-plate distance. The apparent size of the shadow will vary somewhat with exposure, as regions partly shaded may be under-exposed when the exposure is brief and the true shadow may not appear at all. Fig. 10. Variation of size of shadows of small objects when a wide focus is used close to the plate. Fine focus tubes are not needed in gastro-intestinal work, and should be used in other work with such care that the target does not become pitted. Conditions for Operation. — Two^thingsjnust_be consid- ered in the operation o f x-r ay tubes. The first is a proper supply of electrons as current c arriers, the second a proper electric drive to force these electrons aga inst the targ et. These tw^o must_be_so_related to each oth er that a prope r voltage_ can be m ainta ined when current is actually used. No amount of milliamperage will serve todol^aMograpMc or fluoroscopic work without a proper voltage consumptiooi 40 U. S. ARMY X-EAY MANUAL at the tube. The potential difference or voltage drop across the tube is due to a piling up of positive charges and electrons at the target and cathode respectively and this must be done by the generator. When elect^rons move across from_jcathode to, target^they tejid^t^ relieve the con- ioii4r.>tyf ^estion and, if the generator^^hould fail to maintain t he ^**^i***L^PP^^' the voltage and^charge would disappear. The great- * *^*J^.ZL^^ the number of elej3trons passing across in a given^time, ^he more the terminal voltage will be reduced for a given ability^ of jtlie^ generator to pump a new supply. The current is the charge of one electron multiplied by the num- ber passing per second. Hence the greater the milliamper- age, the greater the power demanded from the generator to maintain voltage and the more the drop in voltage from that shown on open circuit or on small current. When the current increases, irrespective of the type of tube used or the design of the machine, the operating voltage will be reduced unless the rheostat or autotrans- former control is moved to apply more power to the pri- >W' mary. The spark gap on open circuit is no guide to the ^^"^^hility of the transformer or induction coil to keep lip ju^^^i^'^oltage whenj:urreni is drawn. Inasmuch as reduced voltage very much more than off- sets the^ffect of change ^f current_in x-ray production as regards quantity, and likewise decreases the_ability to_ pass through maTerial, tlie proper maintenance of volt- age is the mqs^indisj)ensable_ requisite in^ny x-ray instal- lation. By increasing exposure time nearly all work may hejproperly done at low current, hut no_increase_ of expo- sure time will compensate for too low voltage. The transformer must be designed for the voltage supply on which it is used, and it is very essential that the proper terminal voltage on the transformer primary should be maintained at all times and at all loads. After a machine X-RAY PHYSICS 41 is once installed the operator has no control over these matters. The size of wire required to transmit current from the usual power transformer to the x-ray room will depend on the distance between the two transformers and on the voltage used. To transmit the same power at 110 volts as at 220 will require twice the current. Whenever a given current is passed over a resistance there is a volt- age drop or loss. This loss is greater, the greater the cur- rent and the greater the resistance. When the line resist- ance and the current are known the voltage loss is found by taking their product. A loss of 2 or 3 per cent of the line voltage may be permissible. See line wiring, p. 70. The operator must take care that the current through the tube does not drop the potential too much for the work required. For increased tube current the rheostat or autotransformer setting must be raised accordingly. Gas Tube Characteristics. — The earlier^ type^ofjtube de- pended for iXs_supply of electrons on the breakdown pf the atoms of its gaseojas_atmosphere, whereby the_electrons and the positive remainder of the atom were_separated and driven in^oppo^ite directions. This breakdown or ioniza- tion_may be ^_ae_to^evera_l_caiises : 1. The high electric stress between^ cathode and target. 2. Th^ shooting qf^ectrons through tSe~atmosphere. 3. The passage of x-ra ys th^ugh^heatmosphere. The number of_electrons set freejwill depend onjhe tubeXJJ ^ vai^uum. If too few can be had, the tube is of too high ^-y^-- -■^*- vacuum and is called ''hard." It backs up a very high '**«*< spark gap, and may become ''cranky." If too mu ch g as / -r-^ Js__^resent the^j3ibe__cari^ies so much current '^^^^\_}^-^i\l^rA quit e_ imp osjible_ to keep up voltage. The amount of j free gas in th^ tu be will inc rease as the_^parts_QfJliejtub-e ^ nse_ in^ temperature, since gas 'to^^to^tickjto^a^^^ld 42 U. S. ARMY X-RAY MANUAL surface. Therein often lies^ the_explanation of failure injradiography on^prolon^ed^ exposure. The rate of soJ1;£iiJ,ng of a gas tiibe operated at_a_glven initial current an^ vglta^e^ varies with_jts original ex- haustion and its use afterward. On low power with small eurrent~and high voltage^there is a marked tendency to reduce the amount of free_gas and thus raise^the vacuum. "When this tendency is just balanced by the evolution or release of gas by Jieat the tube runs at a nearly uniform current_and_voltage. On slightly higher power it will soften and the rate of softening will generally be greater with a new tube than in case of a well-seasoned one. ^ 4^~{ Danger in Testing". — It is unwise to t^t a gas^tube at [^T^^^^^^^ the power used in gastrO;^intestinal or other h^avy work, 1^ as ijt is Hkely to ov^^often before a min.ij,mmeter can 1)^ r^ad or s£aj;k gap really ascertained. The usual recourse is Jo^note current and^^ap at low power, and assume that^whjn^this is^rop erly adjusted on, say, button_^X, it will give a proper result on a higher^utton Y. Careful study of these tubes ^ows that this is only approximately the_case, for not only^will tubes vary one from another, baJLjhe same jube will behave differently on different days. No better method has "IBeen suggested, however, so the operator should endeavor to season a tube, if pos- sible, before attempting fast work. 1:, Coolidge Tube Characteristics. — The_electron supply in Uyijr.^ the__Coolidge type_of Jiot ^cathode tube i^_due7enferely to the hot t ungsten filainent, as all the gas it is possible to remove has been taken out in pumping. The current car- ried by the tube isjimited by the rate of electron supply and is thus determined sole2x hy the filament current. This maximum tulje curjent at a given_ filament current is ^ly attained a^a sufficiently high voltage and this voltage increases as the filament temperature is raised. When all rtn X-RAY PHYSICS 43 the electrons are being driven across as fast as they are produced, the correspondhig curren^t is named the satura- tion current. After s^uch a cuiTent_ is_ reached Jh^voltage may be_^reatl^increased_ without a rise in tub^current. Fig. 11 shows this characteristic of the tube", quite different from the gas-containing tube where higher applied voltage Fig. 11. Current-voltage lines of Coolidge tube for fixed filament temperatures. Vertical portions are above ''saturation" points. brings increased current. On account of the great increase of tube current resulting from a slight rise in filament current the writer has found it impractical to depend on the filament ammeter as a guide to tube current, especially when using rheostat control. In fact better work is done where no dependence is put on anything except spark gap and tiihe current. -^ . ^ Outflow of Radiation. — As ra diation proceeds from t he Cyt^^ •igin on the target it spreads out and flows through the ^ iix.'^' / origin '^O^-c^ 44 U. S. ARMY X-RAY IMANUAL *^ surfaces of larger and larger spheres. The amount re- ceived in a given time hy ^wy^iixcd area jthen decreases as thQ_distancg^ of the_receiving .surface is greater. This^ decrease always follows the inverse square law. Thus if 100 arbitrary units reach a given area at 10 inches from the target, the same area 20 inches from the target will only get i/4 ^s much in the same time, i. e., 25 units. At 30 inches the same area receives but 1/9 as much or 11 1/9 units. Or to get the same radiation to this area at the increased distances the time must increase as the square of the distance, i. e., if at 15 inches 2 seconds are re- — = 2 X — , at 25 inches 2 X — , at 30 inches 2x /-— jr=2x4 = 8 seconds, etc. Amount of Radiation. — The measurement of x-ray radi- ation has proved a rather difficult matter and need not be fully discussed here. For our purpose the photographic measure is sufficiently accurate and determines the useful- ness of the rays in practice. Whatever the conditions of operation, we might take a time of exposure so as to get the same blackening on two spots on a photographic plate, and then say that the two had the same exposure, when exposure does not mean time of tube action alone. Such a method measures only the effect of rays used in changing the emulsion, not the total beam, the greater portion of which passes through the film. Quality. — Fully as important as the amount of radiation is the quality or distribution of radiation among various wave lengths. Quality determines the ability of the rays to pass through flesh and bone, and was roughly gauged by the use of penetrometers. It depends on the voltage used to drive the current across the space between cathode X-RAY PHYSICS 45 and anode, and is best expressed in terms of voltage or gap. Dependence of Quantity on Electrical Conditions. — It is very important to realize that the amount of radiation as measured by the photographic effect is simply related to the electrical conditions under which a tube is operated. If we let / = Current in milliamperes y = Effective voltage in kv. Then radiation leaves the target at a rate depending on the product of current and the square of the voltage. The amount reaching a given area placed at right angles to the flow and at a distance d from the target and in a time t is measured by — 7^— d^ Thus if 7i, = 40 ma., V^ = 30 kv., cZ = 20 inches, t = 1 second, in one case, and I^ z=z 10 ma., ¥2 = 60 kv., d = 20 inches, t ^1 second in another, then Q^, = 40x30x30x 1/400 = 90 arbitrary units where Q^ = amount of radiation in the first case and §2 = 10x60x60x1/400 = 90 units in the second case. That is, 40 ma. at 30 kv. and 10 ma. at 60 kv. will produce the same quantity of x-rays as measured by photographic effect. However, the radiation produced at 60 kv. is better able to penetrate any piece of matter, and a higher percentage passes through, so that a plate exposed partly to one and partly to the other through a block of material will show much more darkening for the second case, even though, the quantities of radiation generated at the tube are equal. It would darken the plate equally if no body were inter- posed. No matter what amount of current is passed through a tube it is useless for radiographic or fluoroscopic work, unless a voltage able to break down from. 2 to 6 inches 46 U. S. ARMY X-RAY MANUAL For thick parts the of mr between hlunt points is used higher voltage (gap) must be used. The relation of sparking distance (between blunt points) to kilovolts is shown in Fig. 12. The kilovoltage is approxi- mately ten times the gap in inches plus ten. Penetration. — The most characteristic feature of x-rays e IN. 6 - - TTj :"■"■■■:"•"": ■"-;'=: iTrr T I: ::;:: ;= ----:--: :::::"3::: " 4-:; i. ;;;; ;; ^ r „ .irt-+t-- [■: W : ■B :::: :: -.'. :::::::i:::|l + II : ::: ;: TT ::::::::::::::::::: \W :: 1± MMM. i :i w 1 '---^TT ".'.'.'. :: ;::;;-:i--:::;;;ii;:;^? \\ i \l Hi: :: \l ----- \l :::::::::::::::::: Hi! :: ■,--.-- ±Li::^::::::: + :::::i. :: :: ::::::::; ■T- ':: iO 20 60 40 50 60 70 60 90 100 K.V. Pig. 12. Approximate relation between effective kilovolts and spark gap for moderately blunt points. is their ability to pass through material quite opaque to other types of radiation. In all cases there is some absorp- tion, but the rate of absorption or the amount left after passing through any layer of material varies according to the composition of the x-ray beam. The most penetrat- ing rays are produced only at higher voltages. This pene- tration could be accurately defined in the case of a beam of one wave length, but it is quite difficult in the case of an actual complex beam. X-RAY PHYSICS 47 It is essential for the operator to realize that increas- ing the tube voltage will (a) add shorter and more pene- trating rays; (b) increase the quantity of the less pene- trating which were produced at the lower voltage. X-Ray Transformer. — There is no practical means of directly generating an electric current at the voltage needed in the production of useful x-rays, hence it is nec- essary to use a transformer, stepping up low voltage cur- rent to the high voltage required. The transformer consists of two coils of wire around a common iron core. For com- plete insulation of the coils from each other the system is immersed in oil or in wax. If in the latter, it is shipped complete; when oil insulated, the oil is usually shipped separately. In this case, it should be siphoned into the transformer; the inlet side should be raised an inch or so to get complete expulsion of the air. It is well to operate at a low power, allowing sparks to pass across an inch gap for some time to dislodge small air bubbles be- fore putting it into service. Use no oil not furnished for the purpose by a reliable manufacturer; the oil must contain no moisture. Examine the oil level every two months to be sure it fills the tank. An exposed coil is sure to break down by puncture of the insulation. The top of the case should be kept free from oil and dirt. For protection against surges or sudden high tension pulses which are likely to damage the transformer, a resistance should be placed in shunt with the low tension terminals. If this is not provided by the maker, ordinary lamps may be used. Fig. 13. The middle of the secondary is usually connected to the case (grounded) ; this insures a distribution of potential equally above and below the ''earth" potential. Thus, if the terminal voltage is 40,000 volts, then the tendency to 48 U. S. ARMY X-RAY MANUAL pass a spark to any grounded conductor is 20,000 volts. This arrangement avoids in some measure the tendency to discharge to patient, stand, and tube that would result if the full terminal voltage were effective to earth. Care must be taken to keep all contacts on the low volt- age side tight. See that low tension wires are kept as far away from the high tension terminals as possible. If trouble actually occurs, due to short circuit or break inside Fig. 13. Protection from surge by use of a lamp. the transformer, there is no use in trying to repair it, as a rule, unless the trouble is close to the terminals. If there is trouble arising from sparking across between the high tension terminals of the transformer, attaching small spheres will relieve the tension and usually cure the trouble, or insulating barrier plates may be used. Control of the Transformer. — Corresponding to each of the various high tension voltages maintained at the tube terminals, there must be applied a definite voltage across the primary of the transformer. The transformer changes voltage approximately in the ratio of number of turns in the primary to number of turns in the secondary, and X-RAY PHYSICS 49 changes current in the inverse ratio. Thus a particular x-ray transformer might be wound with 500 turns in the secondary for each turn of primary, and it would be said to have a step-up ratio of 500. The secondary volt- age would be 500 times the voltage in the primary and the secondary current 1/500 of that in the primary. A table of the voltages that must be supplied and main- tained at the primary terminals to give various high tension voltages can easily be made in this case. Primary Resultant Spark Gap Applied Voltage H. T. Voltage (approximate) 80 V. 40 kv. 3 in. 90 45 31/2 100 50 4 110 55 41/2 120 60 5 130 65 51/2 140 70 6 150 75 6I/2 160 80 7 220 110 10 liDQO Such primary voltages can be secured from a line sup- ply of 220 volts (a) by the use of a rheostat, (b) by the use of an autotransformer. Rheostat. — The rheostat is an adjustable resistance used to consume a part of the line voltage and leave the proper voltage to be applied at the transformer. Suppose, for instance, it is desired to have 40 ma., at a 5-inch gap delivered to the tube. The primary must be supplied with 120 volts and a current of 40 ma. x 500 = 20 amperes. In this case the rheostat must consume 100 volts from the 220 volt line with a 20 ampere current, Fig. 14. By 50 U. S. ARMY X-RAY MANUAL Ohms law (V = IB) the voltage consumed in the flow of current through a resistance is equal to the product of the current in amperes and the resistance in ohms. There- fore, 100 V ^ 20 X R from which R ^ 5 ohms, hence we would need 5 ohms of the rheostat to get the setting desired. The rheostat consists of coils of resistance wire con- nected end to end, one end of the series being perma- nently connected to one wire of the power line. Re- ^MAMAAMA- H — mvr loX ^ ^ Fig. 14. Diagram showing consumption of voltage by primary of x-ray transformer and series resistance for a particular case. sistance wire is made of some special material of con- siderably higher resistance for the same diameter and length than copper. An adjustable contact is used to join one transformer terminal to any desired point of the rheostat so as to include the required amount of resist- ance in the circuit. Fig. 15 shows the essential parts of a rheostat. The usual numbering makes the power increase as the control lever is moved over to higher numbers. A good rheostat should be of substantial construction, well ven- tilated, and of such current capacity as not to get over- heated under any operating conditions. It should be so X-RAY PHYSICS 51 graded as to give 30 to 70 ma. on a 4-inch to 7-inch gap for radiographic work and from 3 to 5 ma. on a 9 or 10-inch gap for treatment. The use of a rheo- Transformer-^ stat to control tube voltage has the disad- vantage that slight va- riations in tube cur- rent result in serious changes in voltage. To see how different tube currents cause such enormously different voltages on the same control setting, let us first construct a table to give the primary currents corresponding to different tube currents. Each primary current is 500 times the corresponding secondary. Fig. 15. Eheostat construction and connections. Secondary Current Primary Current ma. amps. 10 5 20 10 40 20 60 30 80 40 100 50 Assuming the setting of 5 ohms resistance, let us see how the voltage applied at the transformer varies under different loads. The voltage consumed in the rheostat is V ^ I R, where I is primary current and R is constant at 5 ohms. 52 U. S. ARMY X-RAY MANUAL Secondary Current Primary Current Voltage Consumed in Rheostat Voltage left over to apply at primary Resulting secondary voltage ma. amp. V. 220 V. 110 kv. 10 5 25 195 97 20 10 50 170 85 40 20 100 120 60 60 30 150 70 35 80 40 200 20 10 100 50 250 These figures are represented graphically in Fig. 16. This results in the theoretical chart line corresponding to operation on the particular rheostat control button se- lected. For simplicity, no account has been taken in these figures of line wire resistance, resistance in the windings of the transformer, ''magnetic leakage," and other factors which enter to a greater or less degree. The voltage "regulation" under various loads of a rheostat controlled transformer is poor. On any one con- trol setting the voltage will fall off very rapidly with an increase in current, and rise rapidly with a decrease. In Fig. 16 at 60 kv. and 40 ma. an increase of 8 ma., due to softening of a gas tube during exposure or to fluctua- tion in the filament temperature of a Coolidge tube, will lower the voltage 10 kv., or about an inch of spark gap. The loss in voltage and penetration will have considerably more influence on a plate than the increase in current. Also, if there were a break in the Coolidge filament line, or polarity were wrong, so that no current flowed in the sec- ondary circuit the primary voltage would rise to that of the line with considerable likelihood of sparking to the patient or causing damage to apparatus. Auto Transformer. — To secure better volta^re main- X-RAY PHYSICS 53 tenance under varying loads an autotransformer is often used. It consists of a continuous coil of wire wound around an iron core with taps taken out to control buttons at proper intervals, as shown in Fifr. 17. If alternating cur- 110 WO 30 60 10 60 m so 40 BO BO 10 ^ " k * ^ jL r~ \ Ql ^ L ^ W , 1 • p C ^ J L 5 L^ % c "^ L * ^ ^ ^1 " "^ L 1 . % ^ L ^ ^ ^ . 1 % c " L * . J k_ 1 a s ^ k I \ ^ ■Am s ^\ ^ r — * k ^ . 5 K c ' k " 5 k . -^ iC ^ ^ * . ^ .-_---».»--_»..... .- .... » . MM.. 9^ .... 1^ 10 20 30 40 50 60 70 60 eo 100 Fig. 16. Theoretical chart line plotted from data given in table on page 52. This line shows, for the particular machine and set- ting, the voltage at which various currents will be delivered. rent be applied to the complete winding of such a coil there will be a voltage induced in any part of the winding, bear- ing the same relation to the applied voltage that the num- ber of turns of this part of the winding bears to the num- ber of turns in the whole coil. It is essentially the same as any other transformer, except that primary and secondary 54 U. S. ARMY X-RAY MANUAL are part of the same continuous wire rather than separate winding's, and its action depends on self-induction in a sin- gle coil rather than on mutual induction between two coils. The ratio between the number of turns in the primary and secondary circuits is changed by setting the control lever Fig. 17. Wiring diagram of autotransformer. Notice dead but- tons between the active ones which are numbered. on the various buttons. The autotransformer is used as a control device to reduce the line voltage to that which is applied to the x-ray transformer primary, hence it is a step-down transformer and has fewer turns in the sec- ondary circuit than in the primary. As the control handle is moved to higher readings, more turns are cut into the secondary circuit and higher voltage is applied to the X-RAY PHYSICS 55 primary of the x-ray transformer. Blank or "dead" but- tons arc placed between adjacent live buttons, which differ from each other by a few volts, to prevent a short circuit of this low voltage by the control lever being in contact with two live buttons at one time. The autotransformer is more suitable than a variable ^2**-2#-' ratio step-down transformer, which might be used, since^<^^*i it saves wire and iron, being much smaller for equivalent ^22J^ capacity, and therefore cheaper to build. T he autotran s--fciy .jrah. former principle cannot be ap plie jj^o x-ray a.nd filament trans formers because their ratio is t oo large and jhg^pri- inary^nd secondary ^ustjje insulated from_each^ther. ,zUZo-? The autotransformer, like an ordinary transformer, is j^jLUu^ very efficient and does not change electric energy into ^^'^%jfj*^j^i7^. like the rheostat. The windings are of large copper wir'^Xivtii^ with low ohmic resistance. "Wbenjncr eased current is ^^-^^2^^^ manded fro m an autotrans former, it simply draws mo re ^^^^^^^^^ current from the supply line and delivers the current de-^^^- *^ manded with very little drop m voltage. .cMJU^CSii^ ^^-* **^ When inc xeased currenTis de manded in the tube, it wiTl "'^''^^'^^^ be supplied by an autotransformer with, far less voltage drqpthan is t he case with the rheostat. Fig. 18 shows the behavior of the two devices on a particular machine. Start- ing at 10 ma. and 60 kv., and raising the tube current on a fixed rheostat setting, gives the series of currents and voltages shown by the line AC ; while on a fi^xed autotrans- former setting we have the line AB. Sin ce the q u antity of radiati on (measured pho tographicall y ) in creases as th e current and the square of t he volta ge, we_may comput e the r elative a mount of radiation regardless of penetration. Curve DE shows the rheostat daliyery down__aslowas_use- ful rays are produced ; DF shows the delivery on the auto- transformer up to 60 ma. This form of control is of special value when the fila- 56 U. S. ARMY X-RAY MANUAL ment current of a Coolidge tube is not entirely steady. Thus, if the tube current in the case cited changed from 10 to 15 ma., with a rheostat control, the radiation would be reduced in quantity from 32 to 25 arbitrary units and also would be much less penetrating; while with the auto- transformer the same change would result in an increase KV 10 ZO 30 40 50 60 70 80 90 100 Fig. 18. Relation of x-ray production on two types of control. On rheostat control we have ^C as the voltage-current line. Voltage ordinates at the left. BE, corresponding x-radiation quantity, ord- inates at the right. AB, autotransformer chart line. BF, corre- sponding quantity line. Quantity in arbitrary units. in quantity from 32 to 50 units very slightly less pene- trating than at 10 ma. "Inductance" Taps. — Instead of controlling completely by variation in the applied voltage, in some instances the winding ratio of the x-ray transformer is variable by a dial switch which cuts in more or less turns of the trans- former primary. The lowest ratio of step-up corresponds to the complete primary and, since the secondary winding X-RAY PHYSICS 57 is fixed, to cut out turns of the primary will increase the step-up ratio and give higher secondary voltage. As usual- ly applied, the machine has essentially a rheostat control, with rheostat rather than autotransformer characteristics, and usually more taps are made in the winding than serve a useful purpose. The same principle is conveniently applied in transform- ers built to operate on either 220 or 110 volt mains, half as many primary' turns being used for 110 volts as for 220. The bedside unit uses this principle for 110 volt a.c. and the lower voltage a.c. obtained from the rotary con- verter. In some instances the primary is wound in two sections which are connected in series for 220 volts and in parallel for 110 volts, in the latter case giving carrying capacity for the heavy primary currents as well as the higher step-up ratio. Transformer Chart. — A proper procedure in handling machine and tube is indispensable. Such a method should be adopted as will 1. Save time and tubes. 2. Eender reproduction of results possible. 3. Apply to all machines. 4. Require a minimum amount of instrument reading when operating. 5. Indicate the working range of the machine. The working spark gap, with moderate sized blunt points for a gap, varies from about 3 inches to 6 inches, and currents vary from 5 to 100 milliamperes in fluoroscopic and radiographic work. Any possible combinations on the machine, giving settings outside these limits, are practically useless. On any transformer outfit find first a 5 ma. 6-inch gap setting, then a 40 or 50 ma. 6-inch gap or an 80 ma. 4-inch gap setting. Study no settings outside these limits. In 58 U. S. ARMY X-RAY MANUAXj Fig. 19 take rheostat setting G as an example. Bead the current through the tube when a 6-inch gap just fails to break (25 ma.). Record your setting and the current. Leaving the x-ray transformer control unchanged find the tube current at which a 5-inch gap just fails to break. Do the same for a 4- and for a 3-inch gap. When these readings are plotted to scale, as in Fig. 19, they should /O 20 30 40 50 60 70 80 W /OO HA. Fig. 19. Partial ''chart" of a particular machine with rheostat control. Note that gap change, as tube current increases, is very rapid. On G, for example, we have a 6-inch gap at 25 ma. and only a 5-inch gap at 27.5 ma. or a change of an inch for each 2l^ ma. Compare with Fig. 20. fall nearly on a straight line. If they do not do so, repeat the observations. So long as the power supply is kept at the voltage pre- vailing when this chart was determined the coordinates of a line give all the currents and voltages at any time avail- able on the indicated rheostat setting. H gives the currents at which gaps between 6 and 3 inches are broken on button H. Fig. 20 shows five such lines for a particular machine on autotransformer control. How to Use the Chart. — Using chart, Fig. 19, one needs X-RAY PHYSICS 59 for a particular case 20 ma. at a 4-inch gap. The vertical line through 20 cuts the line marked F at the 4-inch gap. Hence we must use button F. Have spark gap open to seven or eight inches as a safety valve and forget it en- tirely. ]\Iove rheostat lever to F, look at your milliamme- ter, use one hand on transformer primary switch and the other on the Coolidge control. Close transformer switch and bring filament control to a setting, giving 20 milliam- /O 20 30 40 SO 60 70 60 90 ' 100 M.A Fig. 20. Partial ''chart" of the same transformer using auto- transformer control. Note that line marked P shows all useful cur- rents that can be had on this setting: changing from 5 ma. to 50 ma. lowers gap from 5 to 3 inches. peres tube current; there is no need of testing the spark gap. Do not try to read the milliammeter on the throw. Learn to start and set your machine within 10 seconds. On 20 ma. desired, a current of 19 or 21 ma. is close enough for this work. Using chart, Fig. 20, for 45 ma. at a 4-inch gap, go at once to R and proceed as before. A little time spent in making this chart and in using it will reduce time lost and failures. Note that the faster the spark gap falls with 60 U. S. ARMY X-RAY MANUAL increase of tube current the more accurately must the fila- ment current be adjusted and maintained. Synchronous Motors. — A synchronous motor is one that makes either the same number of revolutions per minute as the generator feeding it or a fixed fraction thereof. Thus, if fed by a 60 cycle alternating current, there are 7200 alternations per minute. One alternation is produced when- ever a conductor passes one pole piece of the generator. Thus, a 60 cycle current from an eight-pole machine requires 900 r.p.m (revolu- I tions per minute) t ' Main cn — ,. J^ Main CD IM 1 since 7200 = 8 x 900. For a four-pole ma- ll^ chine we must have 1800 r.p.m., etc. A four-pole motor must then make 1800 r.p.m. for synchronism if on such a circuit, and it must not make 1801 Fig. 21. Wiring of polarity "switch. Or 1799. Since t h e rectifier for a 60 cy- cle current must make a quarter-turn each 1/120 of a sec- ond, the motor must turn at 1800 r.p.m. It must be ob- served that such a motor is designed for a given fre- quency and cannot be expected to work on one greatly different from that intended. Starting. — Many motors require connection to a special starting device in order to bring them up nearly to the required speed before making the running connection. Do not delay too long, and do not throw over the switch too quickly. A little practice will enable you to tell by the sound of the machine when the speed is about right. Polarity Indicator. — Some machines have a field wind- X-RAY PHYSICS 61 ing which ensures the same terminal polarity each time the machine is started. In most machines there is as much chance of a given terminal starting -|- as — . Polarity in- dicators are often used to show which way the rectifier comes into step. Either a primary reversing switch, Fig. 21, is used or the motor switch is opened for an instant and again closed, thus allowing the motor to drop back with mULfiTOR SEGMENT jfEdiermcE Fig. 22. Principle of polarity indicator. Note resistance in series. the chance of changing polarity of the high tension lines. These indicators are devices to indicate direction of cur- rent flow, used in connection with a small low-tension rec- tifier driven by the motor. In Fig. 22 a source of alter- ijating current is obtained from the primary lines ; C is the low tension rectifier, or commutator, fastened on the same shaft as the high tension rectifier, and / is the indicator. The direction of the rectified current through the indi- cator circuit will be one way or the other, depending on how the two rectifiers happen to come into step. The indi- 62 U. S. ARMY X-RAY MANUAL cator itself consists of a movable coil with pointer attached, working against a hair-spring in a permanent magnetic field, and it is very similar in construction to a direct cur- rent voltmeter or ammeter. If the rectified current flows one way through the coil, the needle will be deflected to on side; if the current flows in the reverse direction, the needle will swing to the opposite side. Fig. 23. Principle of rotary converter showing two positions of active coil 180° apart, armature current being always alternating. The indicator is usually of low resistance with an auxil- iary resistance unit included in the circuit to prevent burn- out of the indicator coil. Never connect the indicator with- out this resistance in circuit, and in testing to flnd the proper connections always use a lamp in series with the indicator to prevent burnout, if connection is accidentally made to too high voltage. Rotary Converter. — If the line supply is direct current it must be changed into alternating by means of a rotary X-RAY PHYSICS 63 converter, since the x-ray transformer will operate only when its primary is supplied with alternating current. The operation of the converter is based on the fact that the current flowing through the armature of a direct-current motor is alternating. To simplify explanation, consider the case of a machine having two field poles and a single arma- ture coil. At the left, Fig. 23, are the brushes to which the direct current line is connected, and at the right those from which the alternating current is drawn. The flow of cur- rent through the armature coil in the direction of the ^7? 7\ 7\ 2200.C /A y_A- L\...i54A.t TIME Fig. 24. Eelation between d.c. voltage supplied and a.c. voltage delivered. pointers causes rotation of the coil as indicated, owing to the reaction with the magnetic field between the stationary pole pieces. When the coil has rotated just beyond the ver- tical plane the connection of the rotating commutator seg- ments with the d.-c. feed brushes is reversed, the current through the armature coil is reversed, and rotation is there- by made to continue. Each half revolution of the armature causes a reversal of current through the armature winding and a change in polarity of the two segments. If, now, these segments are continuously connected to the same collector brushes by means of slip rings, the current drawn from these brushes will be alternating current. 64 U. S. ARMY X-RAY MANUAL The direct-current voltage supplied to the rotary con- verter corresponds to the peak voltage of the alternating current wave, and the effective voltage of the alternating current is only about 70 per cent of this, Fig. 24. Thus a converter operating on 220 volts d.c. will deliver only 154 volts a.c. and if 220 volts a.c. are required, it is necessary to step up by means of a special transformer or autotrans- former. Under heavy load the voltage will fall considerably below the 70 per cent, and serious difficulties will arise from trying to use a rotary converter too small for the demands placed upon it. In direct-current x-ray machines the rotary converter drives the rectifying device. In this case, the machine al- ways starts up with the same high tension polarity, and a polarity indicator or polarity switch is unnecessary. If polarity is wrong permanently, interchange the primary lead wires at the transformer or reverse the tube in the stand. In using a rotary converter, one should remember that all the power used passes into the rotary through the d.-c. brushes, and all used by the x-ray transformer passes out from the slip rings. In the a.-e. machine the transformer power does not pass through the motor, so that greater care of brushes, etc., is needed in the d.-c. machine. A considerable proportion of failures of rotaries is due to the breakdown of insulation at the connection of the armature wires to the slip rings. ' ' The Care of Motors ' ' on page 84 applies also to rotary converters. Protection should be made against high tension surges by connecting an incandescent lamp across the a.-c. end, as is done to protect a transformer, Fig. 13. Rectifier. — Two forms of rotating circuit changers are in common use, the cross-arm type and disc type. Both are run by a synchronous motor, and they must be correctly X-RAY PHYSICS 65 placed relative to the motor armature if efficient delivery is to be secured. Fig 25 shows the current path for the four-arm type, Fig. 26 for the two-arm, and Fig. 27 for the disc type. In Fig. 25 when the right hand terminal of the trans- former is -, the flow of negative charge or of electrons is from A-B-tuhe-C-D. If the spindle turns 90° while the polarity of the transformer is reversed, electrons flow from — H V/ I t 7 Rnr u. E A / u. H Tr. Fig. 25. Secondary circuit of ^nook machine. Cross-bar type pectifier — four arms. Fig. 26. Second circuit Waite & Bartlett machine — cross-arm type — two arms. E-F-iube-G-H. In both cases the current takes the same direction through the tube. The disc type is shown in Fig. 27. PQ and RS are two conducting sectors fastened to an insulating disc turned by the motor. Flow is A-B-tuhe-C-D in one case and a quarter turn connects D to B and C to A. Meanwhile the transformer has reversed so that electrons pass from D-B-tube-C-A. In Fig. 25 the cross-arm machine, E and A, C and F, B and G must be well insulated by barriers, or else the shaft must be unduly long. In the disc machine the diameter 66 U. S. ARMY X-RAY MANUAL must be large enough to insure insulation between the shaft and the rim and also to avoid establishing an arc between the fixed sectors along the edge of the disc. Sparking" Troubles. — Dust and moisture may impair the insulation of the barriers or disc. Keep them clean and wipe with a cloth slightly moistened with kerosene. The cross-arm type must be well insulated where the arms pass through the shaft. If a break occurs there, it is not possible to patch it up. Get a new cross-arm. Noise. — If a disc is out of balance or if the bear- ings are worn by lack of lubrication a machine will be noisy. Be sure to keep bearings well oiled. Do not accept a machine poor- ly balanced. Inverse. — Inverse shows by fluorescent rings back of the target in a gas tube and by sparks across gap on low power setting on Coolidge tube. It is caused by recti- fier out of position. It is assumed that the maker will mark the shaft of the cross-arm type or the disc in the other class with reference to the motor shaft so that one can see if slip has taken place and adjust to the proper position. If this has not been done, readjust so that the current is a maximum on a low power setting and with the tube kept constant. This is fairly easy with a Coolidge tube. One accustomed to the appearance of the arcs at the rectifier terminals can set fairly accurately by obser- vation. Fig. 27. Secondary circuit for disc type of rectifier. X-RAY PHYSICS 67 Electro Magnet and Solenoid. — Surrounding a wire while it is carrying an electric current there is always a magnetic field which will deflect a compass needle placed near it into a position as shown in Fig. 28. If now the wire be wound into a coil the magnetic action formerly distributed along the length of the wire is concentrated in the center of the coil, and if a piece of iron be inserted as a core the intensitj^ of the field will be still further in- creased since the iron is much more permeable to magne- \\r • •^i U U U U '"zr* B Fig. 28. Eelation between an electric current and its resulting magnetic field, (a) Cross section of conductor with compass needle in field, (b) Straight portion of a conductor showing current and field, (c) Magnet coil with iron core. Greater strength than the same coil without iron core. tism than air. The coil is a magnet only while current is actually flowing and its magnetic strength is greater the more turns of wire and the greater the current, and de- pends also on the dimensions and quality of the iron core and the design of the magnet as a whole. If the core is fixed and the magnetic action attracts an iron armature, as in some remote control switches, it is called simply an electro-magnet, whereas if the winding is hollow and by its magnetism sucks an iron plunger into the coil, as in the throttle control of the portable unit engine and cer- tain remote control switches, it is called a solenoid. An 68 U. S, ARMY X-RAY MANUAL electro magnetic winding should never be connected on a voltage for which it was not designed, and a winding made for a.c. or d.c. must never be connected to the other type of current supply, as is explained in the next section. Choke Coil. — If an alternating current be applied to an electro magnet there will be a choking effect due to the slow magnetizing of the core and the rapid alternation of the current. Less current will flow than if a corre- sponding voltage of direct current be applied, and the dif- ference will depend on the properties of the magnet and the frequency of alternation. Never expect a magnet de- signed for d.c. to operate satisfactorily on a.c, for it will not let pass sufficient current; and never connect an a.-c. winding to d.-c. lines, since so much current will flow as to most likely burn out the coil immediately. The choke coil is quite generally used instead of a rheostat as a means of control for the Coolidge filament transformer. Variation is secured by moving a piece of iron in or out of the field, the more iron in the field the more choking effect and the dimmer the filament, and the less iron the brighter the filament. Gradation of control is com- plete and there are no sliding contacts to cause trouble. Protection against Surge. — The insulation of the appa- ratus in the primary circuit is sufficient for 220 volts, but not for high tension. If a sudden impulse or surge of elec- tricity is set up in the primary circuit, due to a ground or short circuit of the secondary, or a spark back to the primary, the voltage in the circuit may amount to many times what it normally is. Most of the apparatus in the primary circuit is induc- tively wound (electromagnetic coils with an iron core) and offers so much objection to the passage of a sudden surge that the path of least resistance may be through the insulation of the coils rather than through the com- X-RAY PHYSICS 69 plete winding. "When the insulation is punctured by the momentary pulse of high tension and a spark established, the low voltage is able to maintain this spark and build up a heavy arc, resulting in a burnout. Protection against surges in the primary can be secured by connecting in shunt with the main transformer and motor a protective resistance, as shown in Fig. 13. This resistance is so high that it normally lets pass an insig- nificant amount of current, but in case of a surge the current will go through the resistance rather than break down the insulation, and the apparatus is protected. The protective resistance may be in the form of a car- bon rod, an open winding of fine resistance wire, a resist- ance wire baked into an enameled porcelain shell, or simplest of all, an ordinary incandescent lamp. If the more elaborate devices become broken and cannot be replaced, a lamp should be substituted rather than leave the equip- ment unprotected. If the lamps at hand are not of suf- ficient voltage, they can be connected in series ; two 110-volt bulbs in series are equivalent to a 220-volt bulb. Remote Control Switch. — Machines are frequently equipped with remote control switches or contactors which serve to make and break the heavy primary currents and to permit the use of a small, convenient operating switch. The operating push button or other device makes and breaks a small current in an auxiliary circuit, which is sufficient only to operate the magnetic switch. AYhen the auxiliary cir- cuit is closed, current passes through the magnet of the remote control switch and attracts an iron armature, there- by making contact and closing the main primary circuit. When the auxiliary circuit is opened the magnet ceases to attract the armature and a spring or gravity opens the contacts in the main primary. The timing elements of most timers are delicate devices 70 U. S. ARMY X-RAY MANUAL and not able to make and break the heavy main primary current. They should be connected always in the auxil- iary circuit of a remote control switch, where the current is light and will not cause damage, and they should never be inserted directly in the main primary circuit. Line Wiring-. — The line for x-ray installations should receive more careful attention than has usually been given to such important work. The primary or low tension wiring should contain enough copper to insure that there will be no considerable voltage drop on the line even when the heaviest work is done. If a line from a supply transformer or a generator has a resist- ance of say .3 ohms, and one draws 50 amperes, a loss of .3 X 50 = 15 volts would result. If the original voltage was 100, the total available at the x-ray transformer would be 85 volts. On 220 volt operation this is not so serious, but more reliable operation will be attained if the wire is such that at the highest primary current the line drop does not exceed 3 per cent. When a.-c. lines are used, the transformer from which power is drawn should be of ample capacity, and on d.c. the generator should have a capacity exceeding any esti- mated demand. Connecting a 10 kw. x-ray transformer to a 5 kw. line transformer is poor business. Fuses or circuit breakers should be conveniently placed, and all care should be exercised to avoid short circuiting or grounding the lines. The following table shows the loss in voltage of a primary line for 50 and 100 amperes low tension current, on the assumption of a run of 100 feet between an x-ray transformer and the power transformer, giving 200 feet of line. The terminal voltage to be taken by primary and con- trol is the difference between the line voltage and the loss. Thus, a machine drawing 100 amperes for a short exposure on a 220 volt circuit, using No. 10 wire, will have 220 — X-RAY PHYSICS 71 19.9, or about 200 volts available. On 110 volt operation, 110 — 19.9 ^ 90 volts, making a very decided percentage drop. For this reason, machines using a large primary cur- rent are unsuited for 110 volt operation if rapid work is required. Volts lost Volts lost 200 ft. 50 Amp. 200 ft. 100 Amp. J78 1.5 .98 1.96 1.24 2.4 1.56 3.1 1.97 3.9 2.48 4.9 3.13 6.2 3.94 7.8 4.97 9.9 6.27" 12.5 7.91 15.8 9.97 19.9 To compute the size of wire needed, one must know: (a) the maximum primary current in the x-ray transformer; (b) the distance from the supply transformer (or genera- tor) to the x-ray transformer. The loss in voltage due to line resistance is given by the product of current in amperes hy resistance in ohms of line wire per foot, hy length of supply wires in feet. Thus, on a 220 volt line, if a drop of 6 volts is permis- sible, the line being 200 feet long and the maximum current 60 amperes, then 60 x 200 X Resistance per foot = 6 volts 6 Resistance per foot = — , = .0005 ohms. 60 X 200 Ohms No. per ft. 00 .0000778 .000098 1 .000124 2 .000156 3 .000197 4 .000248 5 .000313 6 .000394 7 .000497 8 .000627 9 .000791 10 .000997 72 U. S. AR]\IY X-RAY MANUAL The smallest permissible wire then is "No. 7." Better use a wire considerably larger to insure the best opera- tion. Hig:h Tension Wiring. — In the use of high power ma- chines, much greater care should be taken in high tension construction than is generally the case. Three points should be carefully considered. These are : First, safety of the patient and operator; second, prevention of loss by leak- age ; third, avoidance of puncture of tubes. While one might get a very unpleasant jolt from an induction coil, yet danger to life is slight as compared with transformers of like voltage. In general, a main- tained voltage of 500 through vital portions of the body is dangerous if a current of 100 ma. or more can be de- livered. A static machine, an induction coil, or a con- denser may give a high initial voltage with a hrief rush of current upon contact or grounding; this is disagreeable but usually harmless. In a power transformer which maintains voltage, the current continues, with possible fatal results. In most, if not all, installations the middle of the secondary coil of the transformer is connected to the iron case or to the ' ' earth ' ' ; the earth is such a large reservoir that its electrical condition may be regarded as constant. The ''ground" need not, and in fact should not, be completed by an actual metallic connection of transformer case to a water or gas pipe. Thus, when working at 60 kv. between the tube terminals, the volt- age between the -\- line and the earth is + 30 kv., and between the — line to earth — 30 kv. This divides the insulation strain on the transformer and reduces danger of sparking to the stand. If one ter- minal of the transformer were grounded, the full voltage would tend to pass current from the other line to any- thing connected to the earth. Thus, there would be a ten- X-RAY PHYSICS 73 inch spark length to stand, floor, water, and gas pipes, etc. AVhen treating at a ten-inch gap the strain is then double that in the other connection, but the line to the grounded side of the transformer is safe to touch. When using metal stands, tables, and protecting screens with the metal screens hetiveen the tube and the patient, they should be well grounded. The patient is then free from induced ''static" FltnMBNT TRfiNeFORMEH Section at 'A' Fig. 29. Arrangement for constant resistance between filament transformer and Coolidge filament. Wire may be used instead of brass tube in the same way. and from any discharge that may occur between the parts of the outfit. When the patient is between the tube and the grounded metal, there is always more danger to the patient, and corresponding care must be used. Aside from the difficulty of preventing spark discharges and arcs, it is of great importance to prevent leakage be- tween all parts having a high potential difference. This leakage is due to high electric stress, rendering the air conducting and giving rise to ''corona." Also, many good insulators when clean and dry become conducting when 74 U. S. ARMY X-RAY MANUAL dusty and moist. High tension wires mounted on ordinary wood or on glass may be expected to leak badly. Surface leakage is less on hard rubber and micanite than on glass. Wiping insulating surfaces with a cloth slightly moistened with kerosene will often greatly reduce leakage over the surface. Corona loss is decreased by reducing the electric stress between the conductor and the surrounding air. This is accomplished by avoid- ing points, sharp edges, and close proximity of conductors of high po- tential difference. High potential overhead lines should be from 24 to 30 or more inches apart. All sharp points and corners should be avoid- ed and small wires, es- pecially if cloth insu- lated, should not be used. Gutta percha cov- ered wire without braid- ed covering is useful where a flexible conductor is needed. For rigid wiring and overhead lines, metal tubing not less than half inch external diameter should be used. This may be mounted by insulating rods attached to the ceiling, or as shown in Fig. 29. The same design can be easily adapted to inter-con- necting rooms by mounting the tubing in the center of a large micanite or porcelain tube and filling the space with a good insulating wax. The insulating tube should be extended 6 to 8 inches from the wall. The rings for tube connection may carry reels if desired. /T\ Fig. 30. The path of negative charge from line through spark gap, tube and milliammeter. X-RAY PHYSICS 75 While line leakage of moderate amount may be toler- ated in fluoroscopic or radiographic work, it may be of great importance in treatment. A milliannneter measures not alone the tube current but all leakage heijond the in- strument itself. Corona between wires, spark gap corona and surface leakage together may give an error of two or three hundred per cent. AVe may avoid this (1) by proper design, (2) by alivaijs connecting the milliammeter beyond the spark gap as shown in Fig. 30. (3) AVhere any doubt arises check by testing with a second milliammeter connected directly to the tube. Tracing Circuits. — The modern transformer x-ray ma- chine is rarely characterized by simplicity of wiring or accessibility of connections. In case of trouble, or where one must connect or set up the machine without expert aid, it is w^ell to learn to trace the circuits and to test out for breaks, etc. While to one unaccustomed to do this, it seems very difficult, a few suggestions may help. There are only two main current paths from one supply line through the ap- paratus to the other line — the motor circuit and the trans- former circuit. In tracing either circuit, follow^ a com- plete metallic path from one supply line through the motor or transformer back to the other supply line. Where paths divide, they must come together again further on, and one must avoid simply chasing around some loop. The main circuit in outline on all resistance controlled machines is shown in Fig. 31. Where no attempt to bring the motor contact into cor- rect phase is made, a reversing switch is provided. Fig. 32. which changes polarity of transformer without disturbing the motor circuit. There may be a special switch to be operated by a small current through a magnet. Fig. 33. A timer connection may be added, as in Fig. 34. Several 76 U. S. ARMY X-RAY MANUAL F M Rh. Fig. 31. Simple primary circuit, rheostat control. Fig. 32. Addition of reversing switch (polarity changer). Fig. 33. Magnetic control-switch added. Fig. 34. Time' switch and foot switch added. X-RAY PHYSICS 77 Fig. 35. Multiple taps ("Inductance taps") added. Fig. 36. Autotransformer instead of multiple primary taps. A. Autotransformer. C. Coolidge filament transformer F. Fuses. F.S. Foot Switch. F.S.S.S. Foot switch safety switch. G. Ground to case of transformer. I. Inductance taps. K.V. Kilovolt meter. M. Main switch. Mot. Motor, O. Operating switch. Pol. Polarity changer. Pol.I. Polarity indicator. Pr. Primary of transformer. Prot. Protective resistance. R. Remote control contactor. Eeg. Filament regulator. Ees. Resistance. Rh. Rheostat. T. Timer, 78 U. S. ARMY X-RAY MANUAL taps (inductances) may be brought out from the primary winding, Fig. 35. There may be a polarity indicator to show the way to place the reversing switch for a given tube connection. An autotransformer may be used as the control device, Fig. 36. The fundamental wiring scheme of all base hospital machines likely to be used is shown in Fig. 37. There are a considerable number of dif- ferences between the various machines but they all con- form more or less to the same general scheme. Different models put out by the same manufacturer may be no more alike than the different makes. Whatever machine be used, to become familiar with the wiring will help to quickly overcome difficulties when they arise. Locating Trouble. — Troubles in x-ray apparatus may be divided into two groups: (a) mechanical; (b) electrical. Under mechanical, we may have worn bearings, worn or broken brushes, slip of rectifier on shaft; warping of wood, thus throwing shaft out of alignment. Care in oiling and keeping apparatus clean and dry will prevent most of these. Under electrical troubles we have: (a) Improper con- nections; (b) break in conducting line; (c) loose connec- tions; (d) failure of insulation. To avoid (a) all wires removed from their connections should be labeled as well as the binding posts, etc., from which they were disconnected. Serious damage may be done if one attempts to operate with improper connections. To find breaks, close switches and use test lamps, as directed in the following pages. When the lamp lights on connecting two points between which the resistance should be low, there must be a poor connection or a break. Loose contacts are likely to cause irregular or intermit- tent action. Failure of insulation may cause current to X-RAY PHYSICS 79 m (um^ 4^ o L~ !- ■-- I- o — o :^ &( o 2 S" l!i ■*^ -~ 'C rt ^ »^ J o c "5 O ^ — S S is ^ ^■^ i g c = S'fi o - -^ <^ ;; O -1-3 ?■ ^ g rt o f-i S I >; 3 s & cc f^ 2 « !=! 80 U. S. ARMY X-RAY MANUAL pass between two wires without going through the proper path. If the fuse in any part of the circuit blows when only moderate power is used, open all switches and look for a short circuit; and if none is found insert a new fuse and test out on low power before attempting to continue work. Beware of the high tension line and terminals when hunting trouble on the primary or motor circuit. 6 Fig. 38. Use of a lamp in trouble hunting. Primary Circuit. — ^When a machine which has been operating fails to work, there must be trouble in either the supply or some part of the circuit insulation or wiring. The low tension side may be easiest tested by using an ordinary incandescent lamp of suitable voltage. Start back of the fuses on the main line, having motor and transformer switches open. Fig. 38. Touch lamp terminal wires (bared ends) to bare wire at 1 and 2. If the line is "alive," a 220 volt lamp will light up to half brightness. Do the same for 2 and 3. Connect 1 to 5, and if lamp fails to light, fuse B is burned out. Or, if switches are closed and the lamp lights when connected to the opposite ends of a fuse, as 2 to 5, the X-RAY PHYSICS 81 fuse must be burned out. Try 2 to 4 and 2 to 6 ; if all these connections give equal brightness to the filament, the trouble must be further along. Close motor starting switch, and if motor does not start connect lamp across motor fuses one at a time. If a fuse is intact, it has so low a resistance that current will not pass through the lamp ; if broken, the full line voltage ap- pears at the break, and the lamp will light. Finally, connect across the motor terminals, and if the lamp lights fully the trouble is inside the motor. Follow the same general procedure in testing the trans- former circuit, but use great care to keep away fro*in the high tension terminals; also, be sure to set rheostat at lowest power. If the lamp lights across the low tension terminals and no spark can be driven across a short gap between the secondary terminals, the trouble is inside the transformer and the chance of its repair by an operator is slight. If a break is near the terminals, it may sometimes be located and repaired ; otherwise it must be sent to a manufacturer. Secondary Circuit. — Outside of a break in the second- ary coil or an arc to the case, the most common trouble in the secondary line is a complete or partial short circuit. This may occur in various ways : 1. In a cross arm machine, the insulation may break down between the cross conductor and the rectifier shaft. 2. In a disc machine, the disc may be dirty or car- bonized, ''shorting" around the periphery or to the motor shaft. 3. A high tension line may be in contact with the tube stand, a wall containing metal lath, the floor, etc. The latter may, of course, be remedied at once by the operator. 82 U. S. ARMY X-RAY MANUAL In case of rectifier trouble, a Coolidge tube may be run directly on the transformer, provided low spark gap and current is used so that the target does not get hot. For fluoroscopic work there is no trouble in doing this, but for radiography time must be allowed between exposures for the target to cool. Care of Tubes. — All tubes are fragile and may easily be d-amaged by fracture. A warm tube must not be placed on a cold support. Keep tubes free from dust and moisture. Do not allow either high tension wire to come within Reducer Raiser _ Fig. 39. Diagram showing softening and raising connections on Snook hydrogen tube, five or six inches of the glass bulb. Always heat the fila- ment of the Coolidge tube before attempting to pass cur- rent through it. Preserve cases or frames in which tubes are received for the return of punctured tubes or those requiring repumping. Use great care in softening gas tubes. Never soften a gas-containing tube with rheostat set for heavy radiography ; use low power. If a tube is too soft, the rays emitted will not pass through the flesh. Bet- ter take more time and soften stepwise, testing after each short passage of current through the softener. To soften the Snook hydrogen tube, pass through the reducer about 15 ma. flve or ten seconds at a time. Re- X-RAY PHYSICS 83 peat if necessary. Do not use more current ; use more time. Always maintain polarity, as shown in Fig. 39. To harden the tube, pass through the raiser about 25 ma. (never more than 30 ma.) twenty seconds at a time. If the tube is excessively soft, disconnect spiral temporarily from -|- terminal of raiser. Connect anode wire to 4" terminal of raiser and cathode to — terminal of raiser. Run three minutes with 22 to 25 ma. Repeat if neces- sary. Replace spiral. Regulate tube before making ex- posure. It should test out at 2-inch gap and about 5 ma. The tube tends to harden a trifle during the first exposure when the tube is cold. To compensate, introduce a little more gas. Operate at 40 ma. for a medium focus tube. It will give much more service than at 45 to 50 ma. A sharp focus should be limited to 20 ma. and the time of exposure doubled. Use a broad focus tube for extremely fast exposures in making stomach and intestinal plates. When a tube is in operation, the heat developed at the target is measured by the current x voltage. If this heat is produced at such a rate that it cannot be dissi- pated by conduction and radiation, the metal at the focal spot may be vaporized or melted and the tube ruined very quickly. It is rarely necessary to do so-called flash or instanta- neous work, and it can only be done at high tube cost. Prop- erly used, a tube is capable of a large amount of work. Do not use intermittent excitation during an exposure. In heavy work, if 60 ma. for four seconds overheats the tube at the gap needed, many operators close the switch for four separate seconds with three intervals of a second or more. The patient must remain at rest for seven seconds. The same exposure may be secured with 40 ma. continu- ously delivered for six seconds. In the latter case the danger of pitting or cracking the target is less and the 84 U. S. ARMY X-RAY MANUAL part need be held immobile for less time. This intermit- tent method has been suggested to overcome the tendency for voltage drop on heating gas tubes while in operation, but the allowable interval is too short to do much good. Care of Motors. — 1. All motors need oil at periods de- pending on the amount of use. Failure to oil may cause the bearings to wear enough to allow the armature to rub on the field supports and ruin the motor. Follow the maker's instructions, if any are given. Do not use too light an oil. An oil like 3 in 1 is good for sewing ma- chines, but must not be used on power motors. Use real machine oil. 2. Most, if not all, motors used on x-ray machines have either slip rings or commutators, or both. Bearing on these are carbon or other conducting brushes. As the tension is low, these must have a good, even contact. Springs are provided to secure this, and if these break or get out of adjustment there will be either intermittent contact or none. The motor then either fails to start or it sparks at these bad contact points and corrodes the metal rings or commutator bars. If only slightly injured, they may be smoothed down by 00 sandpaper (not emery cloth), lubri- cated slightly with paraffin or light oil and rubbed off with a clean cloth. New brushes should be inserted before any serious trouble occurs. Be sure and put them in right, noting carefully how the old ones were placed. 3. Many motors have two sets of connections, one for starting, the other for running. Usually a double throw switch is used and marked for the purpose. Don't close on the running side and wait for something to happen. Don't throw over too quickly. Don't leave switch on start- ing position. 4. Keep motor clean and in as dry a place as circum- stances permit. X-RAY PHYSICS 85 5. If the motor fails to start, open the starting switch and test the fuse on the motor circuit; also be sure the line is ''alive." If power is on and the fuse is intact, go carefully over the wiring to the motor, examine brushes, look at all external wires, and if no break is found it is fairly probable that some internal trouble has developed requiring technical motor knowledge for repair. 6. Be very sure not to connect a motor on a line for which it was not designed, — as an a.-c. motor on a d.-c. line ; or a 220 volt motor on a 110 volt line, or the reverse ; or an a,-c. motor designed for 60 cycles on a 40 cycle line, etc. 7. If an a.-c. motor fails to run at the right speed, do no try to operate tubes with it. 8. It is w^ell to have the field and the armature of an x-ray motor protected from small sparks due to transient surges. Ordinary incandescent lamps in shunt serve very well for this purpose. Most machines have such protection, using either lamps, or special high resistances, or con- densers. Care of Transformers. — The attention of every roent- genologist should be called to the danger to the x-ray trans- former arising from carelessness in operation. There are certain things which should never be done even though they might be done many times without damage. 1. Never operate at high applied voltage when the tube is taking no current, or on an open circuit, especially with rheostat control on high buttons. In this case the effective gap measuring the strain upon the insulation may be very much in excess of what is needed in practice. 2. High tension wires should not come in contact with or close to steam or gas pipes, electric service wires, metal ceilings or walls, metal tube stand, or the x-ray cabinet. Keep them away from things, where they belong. When 86 U. S. ARMY X-RAY MANUAL a discharge occurs from one high tension line to the earth the danger to the insulation of the transformer may be greater than in the case of a discharge between the two lines. 3. In all cases when starting up the machine test out for proper operation on low power and especially be care- ful not to attempt operation of any kind of tube with rectified current of wrong polarity. If, on moderate fila- ment current and a low power setting, no current is drawn through a Coolidge tube, reverse the polarity and again test. After a machine is once up to synchronism it will very rarely change polarity while running, but it may do so in case of a momentary interruption of service or unsatis- factory line conditions. It is wise, whenever lights operat- ing on the same power circuit as the x-ray apparatus be- come dim or are temporarily extinguished, to throw the machine to low power and again test for polarity. 4. Look to the oil level about every two months and record the date on a tag attached to the transformer. If the level is low, add more oil until all the coils are properly covered. Be sure to use transformer oil that has not been open and exposed to dirt and moisture. Wipe oil and dirt off the top of the transformer case. 5. Be sure that the transformer is adequately pro- tected against surges by a suitable type of protective re- sistance. Care of Batteries. — The only type of battery likely to be met in x-ray practice is the storage battery. This is some- times used for portable coil work, and quite often to light the Coolidge filament. Each separate cell of a storage battery adds about two volts to the line. For any given voltage, then, half as many cells must be used as volts are needed. This voltage is independent of the size of the cells. A storage cell does not store electricity; it X-RAY PHYSICS 87 uses electricity to cause a chemical change in its plates, and when it is discharged this chemical change is reversed and electric current flows from the cell. The amount of chemical change on proper charge is in proportion to the charging current and the time of flow, and is estimated in ampere-hours. Thus, a 10 ampere-hour battery will deliver ten amperes for one hour, 1 ampere for ten hours, i/o an ampere for twenty hours, etc. Too rapid charge or discharge should be avoided because of damaging the battery. The storage battery consists of two sets of plates, each containing a salt of lead held in some sort of small lead pockets, the whole being immersed in a solution of sul- phuric acid. In a single cell, all the positive plates are joined together, likewise all the negative, and these sets must not be in contact. The negative of one cell must be joined to the positive of an adjacent one, leaving one -f- and one — for external connection. The ampere- hour capacity depends on the area of -|- and — plates per cell. The following are the main points to be kept in mind when using storage batteries: 1. They must be charged on direct current. 2. The charging rate given by the maker should not be exceeded. 3. The discharge rate allowable should not be exceeded. 4. Loss of electrolyte by evaporation must be replaced by adding distilled water, rain water, or as pure water as can be had. 5. Loss of electrolyte by accidental spilling must be replaced by adding an acid solution of the proper den- sity. 6. In making up an acid solution, never pour water into the acid, but pour acid slowly into the water. 88 U. S. ARMY X-RAY MANUAL 7. Never let the solution get so low as to leave a por- tion of the plates bare. 8. Do not overcharge, nor discharge after the voltage falls below 1.8 volts per cell. 9. Do not let the battery freeze. 10. Do not let the battery stand idle for long periods. If it must be laid up, charge it fully and draw off the solution. For short periods, put a high resistance across its terminals and let it slowly discharge, and charge it up again at intervals. SAAAAAAAAMA B B Fig. 40. Storage battery charging: BB— two cells in series; V- voltmeter: A — ammeter. 11. If overheated by too high current passing m or out, the active material is likely to crumble and fall to the bottom of the cell and cause a short circuit, whereby the battery discharges internally. 12. The discharge voltage falls quite rapidl}^ after a battery is first charged, then more slowly until nearly discharged, then rapidly. "When used on a Coolidge fila- ment, which requires about four amperes, it is well to pass twelve or fifteen amperes through a suitable resistance for three or four minutes to bring the voltage down to the steady state the first time it is used after charging. X-RAY PHYSICS 89 13. A small voltmeter is very useful in charging a bat- tery, and a suitable resistance to bring the line voltage down to that required in charging should always be at hand. Either a voltmeter or a test for acid density may be used to indicate full charge. 14. Do not fail to disconnect the charging line before using on a Coolidge tube. 15. Storage cell terminals are almost sure to corrode; scrape clean when connecting. The charging connections are shown in Fig. 40. If the battery has any charge, it will deflect the voltmeter in the same direction when discharging as when charg- ing. Connect the voltmeter in the right way before start- ing to charge, and it will tell you whether you have con- nected to the charging line correctly. The ammeter may be omitted if one knows that the charging current is neither too large nor too small. Emergency Provisions. — In military x-ray work it is of the utmost importance that apparatus be kept going at all times to meet the demands that are placed upon it. The roentgenologist must keep in mind the human lives de- pendent on him, and he must make every effort to repair, improvise, or do without whatever piece of apparatus may fail in the rush of work. There may be loss of time in securing replacement parts or repair assistance, and during this delay the plant must be maintained in operation. The following are some suggestions for emergencies. Polarity Indicator. — This piece of apparatus may be classed as a luxury, and in case repair cannot readily be made no interruption of sarvice is warranted. With a gas tube, polarity is readily shown by the appearance of the tube. Correct polarity results in a uniform color and inverse in a series of rings. With a Coolidge tube the milliammeter serves as a guide, for no current will flow^ 90 U. S. ARMY X-RAY MANUAL through the tube in the inverse direction. If the meter registers, the polarity is right. Always test on low power to avoid puncturing the tube. Spark gap may be used as an index if the meter also has failed, since on the same control setting the gap will be greater when the tube is not taking current than when it is. In case of burnout of the resistance, sometimes in- cluded in the polarity indicator circuit, an incandescent lamp may often be substituted. Never attempt to connect up without the resistance. MilUammeter. — In working without a milliammeter the appearance of a Coolidge tube gives no idea as to the amount of radiation produced. If the machine is on a steady power line the transformer chart may be used as an accurate means of obtaining a setting of the machine. Suppose a 5-inch gap and 40 ma. is desired, refer to the chart and find which control button must be used. Then, instead of using the chart in the customary way, set the gap for 5 inches and vary the filament temperature until the spark is barely able to break the gap. The milliam- perage will now be right — 40 ma. The appearance of a gas tube is somewhat of a guide to tube current, but if an accurate chart has been made of the machine it is safer to refer to that. At what appears to to be a working setting, measure the spark gap. Then see what current corresponds to this gap on the control button used. In working under uncertain conditions, he sure that the spark gap is as high as it should he. A difference in tube current will affect only the quantity of radiation; a dif- ference in voltage not only changes the quantity but the penetration as well. Timer. — If the timer fails, exposures may be made ac- cording to the second hand of a watch or by counting X-RAY PHYSICS 91 seconds. *'One thousand one, one thousand two, one thou- sand three," etc., is a convenient method, and a little prac- tice will enable one to keep close pace with a stop watch. Remote Control. — In case of failure of the remote con- trol magnet coil or another device in its circuit the custo- mary operating switch will be of no service. It is pos- sible, in some instances, to wire around the remote control switch, or block it closed, and operate from an auxiliary switch in the main circuit, such as a pole-changing switch. Of course, care must be taken to always close the switch the right ivay, otherwise there is great danger of tube breakage and sparking to the patient on inverse polarity. Or, in some cases it would be more convenient to operate by hold- ing the remote control switch closed with a stick during the exposure. Protective Resistance. — If the shunt resistance or con- densers protecting against surges become broken or un- serviceable, do not leave the circuits unprotected, since a more vital element may be damaged. An incandescent lamp of proper size and voltage (usually 220 Y, 16 candle power, carbon filament) connected in shunt as shown in Fig. 13 is very good protection. Motor or Rectifier. — In case of breakage of the rectifier or burnout of the synchronous motor, work may still be done by working on low power and letting the Coolidge tube do its own rectifying. (If the rotary converter fails on a direct current installation and alternating current is not available, nothing can ordinarily be done.) Set the rectifier in position so there will be a minimum of spark- ing distance to the collector brushes, or wire across these gaps. Leave the motor switch open, or in case it must be closed to get current through the main primary and filament primary circuits, disconnect the lead wires to the motor and tape the ends to prevent short circuit. Then, 92 U. S. ARMY X-RAY MANUAL starting an low power, set the tube for a 5-incli working gap and 5 ma. All Coolidge tubes will operate self-rectifying so long as the target does not become hot enough to emit an appreciable number of electrons. Do not work at more than 5 ma. and do not let the target heat to redness, or the tube will no longer rectify, and will very soon be ruined. Spark gap is not a reliable guide to working voltage in a self-rectifying tube, since the inverse voltage is higher than the working voltage. (See page 37.) The excess over working voltage depends on the resistances in circuit and the type of control. To secure a setting of 5-inch working gap and 5 ma., refer to the chart of the machine and set to 5 ma. on the proper control button. Check by seeing that the spark gap is approximately that at which the chart line crosses the vertical axis of the chart. Be sure that the working voltage is what it should be to give rays of adequate penetration. Do all radiographic work either by giving increased time or by using intensifying screens and exposing as with the bedside unit. Autotransformer or Rheostat. — On many machines hav- ing combined control, a failure of one of these elements would merely necessitate leaving it out of circuit and controlling by the other. Broken wires or burned-out coils in a rheostat are easily wired across, but a failure •in an autotransformer is a much more difficult proposi- tion. In case it is necessary to improvise a complete new control, this may be done by building a water rheo- stat. Fill a large wooden pail with water and drop into it a lead or iron plate of about 60 square inches area with wire attached, for an electrode, as in Fig. 41. Suspend securely, and so its immersion may be definitely controlled, a smaller X-RAY PHYSICS 93 snLT SOLUTION piece of metal as the other electrode. Immerse it slightly to correspond to the lowest power setting desired. Test it out, and add ordinary salt slowly, making sure that it is all dissolved, and testing at intervals until the desired low-power setting is reached. Pure water is a very poor conductor of electricity, and the addition of salt lowers the resistance of the solution to the desired amount. Hiorh- er powers will be secured by immersing the upper elec- trode deeper in the so- _^ ^ T ,. , , X CONTROL ELECTfr'ODE lution and loAver pow- ers by withdraw- ing it. It may be noted that in case of failure of both rheostat and auto- transformer on 220 volt machines, as a general rule we may secure rea- sonable operation by applying 110 volt serv- ice directly to the 220 volt connections on the transformer. Then select, when using the Coolidge tube, that current which will give a. 5-inch gap and modify exposures if the current is greater or less than that usually employed. Fuses. — In case the supply of plug or cartridge fuses runs out never ivire across the cut-out block with copper wire. Have an ample supply of 10 ampere fuse wire on hand and include the proper amount of this in the cir- cuit. To fuse for 30 amperes use 3 strands in parallel, for 50 amperes use 5 strands, and so on, Fig. 42. For less than ten amperes the wire may be whittled down to smaller cross section. The leng-th of the fuse wire does not alter LE/9D PLfiTE Fig. 41. Emergency rheostat for control of primary of x-ray trans- former. 94 U. S. ARMY X-RAY MANUAL the current at which it will blow, nor does the voltage of the line on which it is used. The above suggestions cover most of the cases that are likely to occur. The resourcefulness of the roentgenologist is relied upon to cover the others and to keep his plant in operation so long as he has electric power, a transformer, and a tube. With these three essentials and a little in- genuity he should be expected to generate x-rays and do creditable work in an emergency rather than shut down and wait for assistance. Ordering Supplies and Repairs. — Much delay and incon- I] •( • •( h I \oa. 20 R. dOR, 40 R, 50 R Fig. 42. Method of using 10 ampere fuse wire to secure capacity desired. It may be soldered to the brass ends of the burned out fuses. venience will be avoided if care is taken to state explicitly just what is wanted and the exact quantity. The work of the supply depot must be done by people who cannot be familiar with every minute detail of x-ray equipment, and mind readers are scarce. When ordering a machine specify: 1. Type of current, a.c. or d.c. 2. The frequency of cycles, if a.c. 3. The voltage. 4. The power available in kw. 5. Gauge and length of wire needed to connect up. 6. If d.c, always specify a rotary converter and the d.-c. voltage. 7. Be sure to state that the motor, transformer and X-RAY PHYSICS 95 Coolidge filament transformer when used on 154 volts or 70 volts a.c. from a rotary must operate properly. Thus — 220-volt-a.c.-60 cj^cle-lO kw — specifies a definite type of machine. In ordering repair parts state the name of the apparatus, the maker, if known, and either give a drawing or such an exact description or name as to identify the piece re- quired. Sometimes one may return a broken or defective part as a complete identification. In case of supplies be sure to give the amount and any other information that will make your needs clearly un- derstood. Thus an order for "an x-ray screen" is mean- ingless ; one for a "10 x 10 inch Patterson fluoroscopic x-ray screen, mounted with lead glass," is definite. Never fail to give complete address to which goods are to be forwarded. No small part of what we protest against as "red tape" is made necessary by failure of individuals to convey a clear idea of what they desire. When possible confine your requests to those articles specified in the supply tables. Induction Coils. — It sometimes becomes necessary to work for a time, at least, with an induction coil. While not often used in this country one must be prepared to use it if need be abroad. Coil Characteristics. — A good induction coil should be able to give a heavy discharge at a voltage high enough to break a 10- or 12-inch gap. Under no circumstances must a coil be operated at high power long enough to heat the insulation, as the. insulat- ing power is much reduced at high temperatures. Each coil has its own characteristics which determine its best working conditions. These characteristics depend on the primary and secondary resistances, on the amount and 96 U. S. ARMY X-RAY MANUAL quality of iron in the core, on the number of turns in the coil, and on the mode of winding. The most undesirable feature in coil operation for x- ray work is the unavoidable inverse which must be mini- mized in the use of the ordinary tube. The amount of inverse depends on the coil, the interrupter and the tube. A coil having a considerable number of primary turns and but little ''magnetic leakage" gives less trouble with inverse than other types. The direction of secondary current while the primary is increasing is opposite to that during a decrease of primary current. Generally it is possible to reduce pri- mary current at a greater rate than that at which it can be built up. Hence the "break" voltage is usually high- er than that at ' ' make. ' ' The current of higher Fig. 43. Valve tube. i, • r? i • xi, voltage IS useiul m the tube, but the inverse is not only ineffective for ray pro- duction but is a source of positive injury to the ordinary tube. If the make current could be caused to rise slowly enough, the resulting secondary voltage would not force current through the tube. In practice this is not pos- sible, although the voltage giving ''inverse" may be very much smaller than that giving "direct." Valve Tubes. — In order to reduce "inverse" as far as possible, various unsymmetrical tubes, Fig. 43, have been devised ; these offer much greater resistance to discharge in one direction than the other. Such valve tubes are often supplemented by a series of small spark gaps which are readily broken down by the ' ' direct, ' ' but not by the lower voltage "inverse." These devices all reduce the energy X-RAY PHYSICS 97 available for x-ray production. Fig. 44 shows a tube designed to indicate the presence of inverse. If there is no inverse, only one of the metal terminals at the gap cB^^ A Fig. 44. Vacuum tube oscilloscope. ^P, will glow. If both glow to the same extent, inverse cur- rent is present. Fig. 45 shows the wiring diagram for a coil with mer- ■RHEOSTflT MERCURy iNTERRUPTEn Fig. 45, Complete connection for the operation of tube with in- duction coil and mercury interrupter. cury interrupter, condenser, oscilloscope, valve tube, and series spark gap. Note that the milliammeter is next to the tube. When the spark gap is placed between the meter and the tube, leakage across the gap may make the reading 98 U. S. ARMY X-RAY IMANUAL much above the current actually passed through the tube. Interrupters. — The secondary voltage of an induction coil is the result of change of current in the primary. It is evident that we cannot have the primary current grow indefinitely, so we must allow it to decrease and increase alternately. The value of the secondary voltage for a given coil depends entirely on the rate at which the primary current is changed. Thus, if a current of 80 amperes should be reduced to amperes in .02 seconds, the current nc. + - il jfjkSwiTCH Pt. Rb Interrupter Fig. 46. Wiring for induction coil with electrolytic interrupter. has changed at a mean rate of 4000 amperes per second. If it required .04 seconds for the same change, the rate is 2000 amperes per second. The mean secondary voltage is twice as great in the former case as in the latter. As induction coils are intended to operate on an in- terrupted direct current, some device must be used to open and close the circuit. The early interrupters were of the vibrating hammer type, but these have largely been superseded by others much better adapted to x-ray work, -They are still used on small outfits where large power is not drawn. X-RAY PHYSICS 99 The Wehnelt Interrupter. — The AVelmelt interrupter consists of a lead and a platinum electrode immersed in a solution of sulphuric acid. The amount of platinum ex- posed to the solution is usually variable at will. When connected as shown in Fig. 46, the application of sufficient voltage will result in the formation of a non-conducting layer between the solution and the platinum, thus inter- rupting current flow. The layer is very quickly dissipated, reestablishing current onlj^ to be again formed, etc. "When To Motor VTTT ^."^ Fig. 47. Centrifugal jet mercury interrupter. only a small amount of platinum surface is exposed, the number of interruptions per second is high and the cur- rent is small. Greater immersion lowers the number of interruptions and draws more current. Operating Notes. — 1. The solution should contain 30 to 35 per cent pure sulphuric acid. In mixing, be sure to add small amounts of acid to water, allowing the mixture to cool after each amount is added. Never pour water into the acid. 2. Do not use a condenser, as is done with the mechani- cal interrupter. 100 U. S. ARMY X-RAY MANUAL 3. If your point or points are adjustable, use little or no resistance in series with coil and interrupter on a 110 volt circuit. 4. Your coil may not have the correct self-induction for use with a Wehnelt, at least over a wide range of fre- quencies of interruption. If inverse is prominent, try a greater amount of platinum exposed, thereby lowering the frequency of interruption. 5. Do not run too hot, and if. possible enclose inter- rupter in a sound-proof box, or place outside. Fig. 48. **Eotax" interrupter. 6. Be sure that connections are made to the proper terminals. 7. Do not try to operate on alternating current with- out a rectifier. This has been done in a few instances, but is not advised. The Mercury Interrupter. — Various forms of inter- rupters using mercury have been invented, and have some advantages for use with heavy coils. They allow varia- tion in two essential particulars, viz., number of inter- ruptions per second and relative duration of make and break. Two forms are in common use. In the jet type, X-RAY PHYSICS 101 Fig. 47, a centrifugal pump throws small streams of mer- cury against V-shaped iron terminals. The motor speed determines the number of interruptions, and raising or lowering the iron decreases or increases time of flow rela- tive to that of no current. In the Rotax interrupter, Fig. 48, the mercury is thrown into a ring revolving with the case. An insulating disc with a small conducting sector is mounted so that it may be moved to and from the circumference. When in con- tact with the mercury, the disc rotates at a speed depending on the mercury speed and the amount of immersion of the disc. The latter is insulated from the case and is connected to an external binding post. The relative time of current "on" and "off" varies with the immersion of the disc in the mercury. A small amount of paraffin oil is used, forming a ring inside the mercury to prevent oxidation. A better plan, when the apparatus will per- mit, is to use illuminating gas in the case, which reduces contamination of the mercury and enables long periods of operation without refilling. If gas is used, a small burner should be connected to the cavity and kept burning, and the current should never be turned on until this light continues to burn, as severe explosions may result by spark ignition of an air-gas mixture. Recent forms have a safety valve to protect against explosion. A suitable capacity must always he connected to the terminals of interrupters of this type. The amount of this capacity will vary with different inductances of the primary and to some extent with the frequency of the interruption. Operating Notes. — Carefully read and preserve any di- rections furnished by the maker of the interrupter used. If none are at hand, and trouble arises, some one or more of the following may be found to account for it. 102 U. S. ARMY X-RAY MANUAL 1. No current in any position of the disc. Look for poor contacts, either from bad brush on revolving case, loose binding posts, or broken wires. The mercury should be examined to be sure that there is enough and that the oxide does not prevent contact. 2. Very heavy primary current and little or no second- ary current or voltage. Examine capacity to see if it is punctured ; if so, renew at once. If condenser is all right, see if disc is free to turn and is not immersed too far by reason of an overcharge of mercury. 3. Be sure to keep the required amount of oil in the case, as, if there is too little it becomes carbonized by the arc and gives trouble. 4. The mercury must be kept clean. When it is dirty, oxidized, or emulsified with oil, either clean by filtering and washing or put in new mercury. A coil in which a current is changing always develops an active opposition to the alternation of current. On an attempt to increase the current, the coil acts as an op- posing generator, and when current falls the generator action reverses. This action is due to self-induction. The opposing voltage, when we change current at the rate of 1 ampere per second, is an important factor in behavior of the coil, and is named the coefficient of self-induction. On account of self-induction, no really instantaneous change of current can take place, arid the response to variable voltage will depend on this feature of the coil and on the rate at which we attempt to make current changes. Each coil is an individual in this respect, and one should find by trial the conditions under which it op- erates best for each purpose, and then adhere to these conditions. A little time spent in this way will save much time and annoyance later. Tubes for Use with Coils. — The current wave from a X-RAY PHYSICS 103 coil is quite different from that from a transformer. The current consists of a series of short rushes with considerable Fig. 49. Oscillogram — induction coil current with a gas mercury- interrupter. Fig. 50. Oscillograms — induction coil currents with Wehnelt in- terrupter. time between each impulse. Fig. 49 shows the variations of current with time on an induction coil with a good mercury interrupter. Fig. 50, two curves with a AYeh- 104 U. S. ARMY X-RAY MANUAL nelt break. Note the large amount of inverse in the latter. In order that the tube current may not lower the voltage below the required point, it is essential to have gas tubes at relatively high vacuum, or hard. Thus we must have small tube currents. Readings. — Milliampere and spark gap readings are far less reliable guides for radiography when using coils than on transformers. The gap shows peak voltage which maj^ bfe high but transient. As the ordinary milliammeter indi- cates the difference between direct and inverse, one may get reading and yet have the tube operating. Portable Coils. — Portable coil outfits are so varied as to make brief description impossible. Those heretofore in use were largely of the ''Tesla" type. The electric lighting current is stepped up to about 2000 volts by a small step-up transformer, if the supply is from an alternating current line. If the current is direct, the circuit is made and broken by some form of vibrating interrupter, giving much the same effect in the transformer as though an alternating current was used. The 2000 volt current from the secondary of the step-up transformer charges a condenser. The condenser is dis- charged through a few turns of wire wound around the outside of a secondary, consisting of a large number of turns of fine wire. The discharge of the condenser is at an enormous frequency, and high voltages of high fre- quency are generated by the Tesla coil. As the current delivered by the Tesla coil is alternat- ing, a different form of tube must be used from that for other types of x-ray generator, if best results are de- sired. This special tube has a valve arrangement built into it which tends to suppress one wave of the current. Fast Work. — From what has gone before, it is clear that X-RAY PHYSICS 105 the same radiographic density can be secured in a great variety of exposure times. Certainly, for the in- experienced operator high speed is inadvisable. If 3 to 10 seconds would give the most desirable exposure, an error of one second would give a fairly good plate. On power such that i/> second is best, an error of one second in judgment or execution would exceed the latitude of the plate. The conditions for fast work are : 1. Small target-plate distance. 2. Very large current. 3. High voltage. 4. Fast plates or intensifying screens. The disadvantage of the first is distortion and haze of outline, due to size of electron focus; of the second danger of melting the target, and difficulty in setting to proper voltage. AYhen high voltage is used, the even- ing up of penetration, as well as the increase of scattering with high penetration rays, tends to give flat plates. Very fast plates and ordinary plates with screens allow little latitude of exposure. Screens also may register their own dust or surface defects. Photographic Density and Character of Negative. — Considerable objection has been made to the use of photo- graphic plates, films, or paper in the study of this type of radiation. Much of the adverse criticism is well founded, for the following reasons : The unaided eye is a poor judge of comparative absorption of light by a negative; only by means of comparison involving photometric appara- tus can one be fairly sure of correct measurement. If an unexposed or clear portion of a negative transmits an arbi- trary amount of light, Q, an area transmitting 50 per cent or half as much w^ould be said to have an opacity of 2 ; and the logarithm of this opacity would be named the 106 U. S. ARMY X-RAY MANUAL density of this portion of the negative. It has been found that density determined in this way is proportional to the amount of silver reduced per unit plate area. Transmis- sions, opacities, and densities are related as follows : Transmission per cent Opacity 100 (Clear glass) 1 90 10/9 = 1.11 80 10/8 = 1.25 70 10/7 = 1.43 60 10/6 = 1.66 50 10/5 = 2.00 40 10/4 = 2.50 30 10/3 = 3.33 20 10/2 = 5.00 Density D (Log 1 .104 .223 .358 .507 .693 .916 1.203 1.609 0) When the intensity and quality of radiation remain fixed, the expo- sure varies only with the time. Suppose that Kt = E where K de- pends on the nature and intensity of the radia- tion. Plotting E and D, there remains a line ap- proximately as shown in Fig. 51. A portion of this line AB is nearly straight; below A and above B it is curved somewhat, as shown. If AB is produced to cut the density axis at /, 01 is named the inertia of the plate. The portion AB of the plot is the region of proper exposure. Above B the den- / £ Fig. 51. The relation between ex- posure and density of a photographic plate. Below A — underexposure. Be- yond B — overexposure. 01 — inertia of the plate. X-RAY PHYSICS 107 sity fails to increase in proportion to exposure and is the region of over-exposure. In fact, if the exposure is car- ried too far, the density falls off and a reversal may occur. The slope of the line AB or the ratio BM/AM = 7 is named the development factor ; For under-develop- ment T is small and contrast is low. For longer de- velopment, the line swings counter-clockwise on / as a pivot. The point where one should stop is a matter to be governed by experience. In ordinary photography 7 ranges from .8 to 1.3 ; probably no accurate determination can be made of the most desirable conditions until some agreement is reached as to the best quality of negative for specific purposes. The inertia of the plate is not affected by time of de- velopment. A fast plate is one where 01 is small. A plate of great latitude is one where exposure difference for A and B is large. The speed of a plate is determined by the inertia 01 and is expressed in arbitrary sensitometer units. The conditions during development fix, for a given plate, a time beyond which development should not be carried on account of fog. In x-ra y work, the use of hi gh p ene- tration on thick patients tends to fog by cross scatter^ radiation, and this may be noticed long before developer fog becomes troublesome. As a means of measurement, we may utilize different portions of the same plate under different physical condi- tions to learn whether the radiation effects on the various portions are or are not alike. For example, if a canstant voltage is used at constant distance, the exposure varies as the product of current and time — so that 20 ma. for 2 seconds and 40 ma. for 1 second should give equal density with equal development, provided the rise and fall of voltage be alike in the two cases. 108 U. S. ARMY X-RAY MANUAL Certain terms are in common use when negatives are described, and should be understood. Contrast refers to the amount of difference in darken- ing for a small difference of exposure. Thus, if rays pass through bone and flesh, there is a variation in the amount of radiation reaching the plate, due to difference of absorp- tion; when this results in a marked difference in darken- ing, the negative is ' ' contrasty. " Contrast depends on the nature of the plate and the development, and to a great extent on the quality of the radiation used. If the beam is too penetrating, contrast is reduced, for if rays pass through bone and flesh equally well, there would be no contrast. Too ''soft" radiation will fail to get through the denser portion and will give high contrast but poor detail in thick parts. The amount of contrast to be de- sired will vary with the work to be done. A plate showing fine bone detail and contrast may show but little of the soft tissue. Detail refers to the fineness of the marking of light and shade. Thus, a mastoid plate should show minute struc- ture, or lines of light and shade should show sharp grada- tion or density change. Detail depends on: 1. Breadth of tube focal spot. 2. Distance of target from plate. 3. Distance of part to be radiographed from plate. 4. Complete immobilization of patient. 5. Correct exposure and development. Exposure Table. — Many attempts have been made to work out exposure tables such that inexperienced operators can get favorable results. Without doubt the best work is done when spark gap, current, and time are chosen with reference to the individual case in hand, and any operator who cannot improve on the results secured by adhering to any single table is unfit for the work. X-RAY PHYSICS 109 As a general guide in starting work, a uniform rather high gap may be used — say 5 inches, and a uniform tar- get-plate distance — say 20 inches, except for chest, where 28 inches is advised. With all this understood, the average of reports from many sources gives the following table for a patient of about 150 pounds weight and a Seed x-ray plate. Some people prefer a shorter gap for most work [p-a head work excepted], and certainly with the ordinary solid tungsten target, medium focus Coolidge tube, better negatives result from proper exposure on a four-inch gap than on a five-inch one ; this wall require about 50 per cent increase in time of exposure for the same distance and current. Part Time : sec. Head, A-P 12 Head, Lat. 6 Neck 3 Shoulder 31/2 Elbow 11/2 All exposures on 5" gap. Wrist 1 40 ma. 20" distance ex- Kidney 3 5 cept chest, which is at Bladder 3 5 28". Hip joint 5 7 Pelvis 5 7 Knee 2 Ankle 11/2 Lumbar spine 5—6 Teeth (slow film) 4 Teeth (fast film) 11/2 Chest (at 28") 21/9—4 Notes: (a) For parts above average thickness, increase time considerably more than in proportion to increase of thickness. 110 U. S. ARMY X-RAY MANUAL (b) If it is necessary to work at other distances than 20", use the following table of multiply- ing factors: Distance Time factor Distance Time factor 15" .6 21" 1.1 16 .6 22 ' 1.2 17 .7 23 1.3 18 .8 24 1.4 19 .9 25 1.6 20 1.0 For ''Diagnostic plates," reduce time by 14. For doii.- hie coated Eastman films use half the time. With intensifying screens no fixed rule can be given. A reduction factor may be found for the screen used as indicated on pages 112-114. Plates and Films. — Photographic plates and films con- sist of a thin layer of gelatin containing a salt of silver and spread on glass or celluloid. Light and x-rays cause a change in the silver salt such that suitable chemicals, called developers, act on the portions that have received the radiation, changing the silver compound to metallic silver, and thus rendering those portions more or less opaque to light. The opacity produced will depend on the amount of radiant action, on the sensitiveness of the emul- sion, and on the development. Those portions receiving much light or x-rays, when fully developed, may be quite opaque ; other portions may be entirely or nearly trans- parent. After development the plate is washed and placed in a ''fixing" bath which removes the unused silver salt, as shown by the disappearance of the cream color of the emul- sion, rendering the parts not radiated and developed trans- parent. X-RAY PHYSICS 111 All plates sensitive to x-rays are also sensitive to ordi- nary light and hence they must be entirely protected from ordinary white light until finished. The emulsion is an example of unstable chemical struc- ture and may be injured by (1) moisture, (2) high tem- perature, (3) contact with other material, (4) exposure to light or x-rays, (5) bending. Plates should be kept in the original boxes, on edge, in a cool dry room, well pro- tected from x-rays. No more plates should be put up in envelopes than are likely to be used in the next two or three days. Filling Envelopes and Cassettes. — X-ray plates are used either in envelopes or in plate-holders, called cassettes. It is quite essential that in regular work the emulsion side should be toward the patient. To insure this when using envelopes, arrange the envelopes to be filled before darken- ing the room. Put black and yellow envelopes in alterna- tion with the end flaps down, insert plate with emulsion side down, i. e., so that the flap will fold over the hack of the plate ; then insert the flap end first in the yellow envelope with the emulsion down, so that the flap of the outer en- velope also folds over the back. Then place the smooth side of the envelope toward the target. A soft brush is useful to remove dust from plates and cassettes. In using cassettes without screens, put the emulsion side down. This side can be determined by sighting across the surface, as it appears dull as compared with the glass side, or touching the tongue to the extreme corner of the plate — the emulsion side will be slightly sticky. Form the habit of closing partl}^ empty plate boxes at once after filling envelopes or cassettes. Attention is called here to the new double-coated film which is used to considerable extent. In this case there is no difference in the two sides of the film and no at- 112 U. S. ARMY X-RAY MANUAL tention need be paid in placing it in the special holders provided. It should be borne in mind, however, that these films must be handled with great care. Finger prints are much more likely to show and both sides of the emulsion must be protected from moisture and scratches. Great care must also be taken not to wrinkle, bend or twist these films before exposure. For this reason it is undesir- able to attempt to use them in the ordinary black or yellow envelopes usually supplied. They should be used in cas- settes or in the special holder furnished for the purpose. Intensifying Screens. — When u^ing intensifying screens the usual practice in thisj30untry isto all ow the rays t o 'pas&^Jhraiigh tlie_ glass_to the^^mulsion and then to the screen surface. Consequently the^ negative, when^ viewed wi^ the einuls ion side toward^jthe^eye, i^^j^versed 3s_jto right and Jeft as compared with^the usual _glate;^_The screen sjiould be firmly fixed to the^^^^k_of_Jhe_casset^e a nd sh ould be kei)t jcrupiilouslyi clean; wipe off dust ^rth a dean cloth, and never touch the surfacejwiili^wet_or_ greasy fingers. I ns^ cleaned plate with emulsion side up, ^^be sure that the springs press the screen firmly against the plate. On account of the varj^able_x-ray^pacity o f the glass at present in use, screen work witli plates is rather ^uncertain. Be sure to keep screen clean by not letting it g^et^^t, dirt ^ or dusty. It is quite inipossible tojie sure of the sp eed of the vari- ous ^ere^s^ in actual use, inasmuch as this depends on so many conditions, ^such as amountoJ use, and the general care which has been exercised in handling, as welTas their initial speed. " * • In order that the proper exposure may be given it is well to determine the_multiplying factor by which the screen increases the normal speed of the plate. This may b'e" ^ea^lyjdone by the use of a film of proper size in the screen X-RAY PHYSICS 113 holder, expos ed at the same time with one in an ordinary em^elope or container laid ontop_ofthe screen7"~"Tliis en- velope shonld be cr oss^rnrg Twith lines approxi mately I/2 iii£li_ apart, and a heavy sheet of lead placed t o cover a_ll except oi' ie end div ision, bei no;: snre that iirm jccnpies thi^ division. Make a v ei'y br ief exposure at low power and considerable distance, usin^^a_Jimer, if one is available, and leaving the tube, machine, tim^i^ ^and dis tance un- changed; slide the_ sheet of lead back, leaving two divi- sions exposed; and j: £i)eat the exposure. Do this for all of the film and develop both films at the same time and in the same developer."""^* It will be evident that if there were 15 divisions, the one which was exposed first received 15 exposures, the next 14, etc. The last may be numbered 1, the next 2, etc. If it should be found that the film in the envelope, and not affected by the intensifying screen, required 12 of these exposures to give the same blackening as number one, with the intensifjang screen, it is clear that 1/12 of the time required with no screen should be used. This procedure is somewhat more reliable if exposures can be through a rectangular block of paraffin, as the speed of some screens seems to vary considerably according to the filtration which the rays have received before reaching the emulsion. Fig. 52 shows such a pair of films for a particu- lar screen. After the determination of the speed, it should be marked on the cassette so as to be available during use. Care in Handling Plates and Films. — In all cases, plates and films must be kept well protected by lead when in the x-ray room. A good lead-lined box on casters is very use- ful for this purpose, and where much work is done, one for exposed and another for unexposed plates should be pro- 114 U. S. ARMY X-RAY MANUAL vided, or a partition plainly marked ''EXPOSED" and ''UNEXPOSED," dividing a single box may be used. Fig. 52. Gradation due to successive equal exposures with and without intensifying screen, a, without screen, &, with screen. The following cautions may be given to those unfamiliar with darkroom work: 1. Never handle plates or films with wet or greasy fin- X-RAY PHYSICS 115 gers, either before or after exposure. ]\Iarks and streaks are sure to result, even if the emulsion is not destroyed. 2. Learn to handle plates without touching the emulsion side, even with dry lingers. 3. Mix all solutions according to instructions and see that chemicals are actually dissolved. 4. Keep all trays clean, and do not use insufficient or too old developer; stains are hard to remove, and the cost in time and money is excessive if it is attempted. 5. In tray development, be sure that the developer cov- ers the entire plate at once. Tilt the tray slightly on insert- ing the plate, and tilt the tray in several directions to ensure complete wetting of the film as soon as possible. Keep tray in motion during development. 6. Do not examine the plate by removing it from the developer until the minimum time for full development on normal exjDosure has elapsed. 7. Do not try to develop several plates in a tray at one time if they overlap. 8. Wash negatives well on removing from the developer, before placing in the fixing bath. 9. Leave negatives in the fixer for some minutes after they seejii to be fully cleared ; then wash thoroughly, in running water if possible. 10. Do not use the same trays for hypo and for devel- opment. Mark hypo trays and keep them well away from developer. A little hypo in the developer is fatal. 11. Keep negatives in a dust-free atmosphere and in one location and position until dry. 12. When the developer is not in use, keep in tightly closed containers. Glass fruit jars with rubbers are as good as anything for small amounts. L^se a close-fitting float in tank. 13. Don't try all the developing formula you can find ; 116 U. S. ARMY X-RAY MANUAL take one advised for the plate you use, and learn to use it. 14. Don't fix in plain hypo in warm weather. PJates will frill if you do. Tank Development. — In tank development, the plate is placed, while dry, in a special frame or holder and hung vertically in the tank containing the developer. This method is desirable when much work is done. With strong developer, stirring by moving the holders will prevent vertical streaks. Temperature. — The action of the developer varies greatly with changes iii tempe ra ture. Between 60° F. (16° C.) and 70° F. (22° C.) is best. Hot developer works fast and is likely to fog the plate. Cold developer is slow and may not give anything on a normal exposure. Do not cool developer by adding ice or ice water, as this dilutes the solution. When using tanks, cold or ice water may flow or stand around the developer tank until a proper temperature is reached, or put ice in a fruit jar and immerse jar in developer. Concentration. — If more water is added to a normal developer, slower action will result. This is sometimes ad- vised in tank development, and with screen plates, but is not necessary if the developer is stirred occasionally. Plate Defects. — Plates are sometimes defective, due to faults or accidents in manufacture, but in most cases of complaint the trouble is due to improper treatment after leaving the factory. If one is sure of proper exposure, development, fixation and washing, and still finds streaks, spots, bubbles, or bad color, the plates may be blamed. Much trouble is traced to the materials used at present, and in all cases of doubt cheek plates should be made. Defects are not likely to appear on the same region in both negatives. Looking across the negative at any un- evenly illuminated surface will often show whether a spot X-RAY PHYSICS 117 is due to a defect in the glass or to something on the emul- sion surface. Examining Negatives. — When it can be avoided, plates ought not to be examined until dry. If they must be used while wet, care is needed to avoid heating the gela- tin or it will melt and completely ruin the negative. A well-diffused illumination is very desirable ; it should be well under control so as to give a strong light for dark nega- tives and a much weaker one for thin ones. Ground or opa- lescent glass is not needed if a dull white surface is illumi- nated and the plates are viewed by light reflected from it. Fig. 53 shows a useful type of illuminator. Developer Action. — Th e acti on of developer on^ an ex- posed p late is rather a c omplicated matte r. For t he pres- ent purpose we may omit discussion fur ther than to s ay ^ that with any_a^ctive developing agent a su itable am ount of alkali Js indispensable. Do not var y the proportion shown^in reliable^an d tested for mula, at least in routine work. Developm ent at any given depth below the surface of the emulsion can only take place W'hen the active de- veloping solutio n has reached t hat po int in sufficient a mount to ca use the chan ^e_r equi red. Hence, dilute or partly exhausted developer requires more time. Prolonged a ction o f develo;Qer on the emulsion will cause a darkening even with little or no exposure, and to ^strong de veloper wil Fover-de velop t he outerl ayers be fore the dee per ones, a re affected . Plates ex posed t o x-ray s are developable, th rough the entire depth of emulsion, while light onl y af- fects_th e outer layer. Hence, if fog can be avoided, x-ray p lates^ will increase in density" with longer development to a greater extent than will negatives exposed to light The action of ^tassium bromide restrains or delays develop- ment at the surface an'5^ ten^s To keep the ' ' whites ' ' clear. All developers are absorbers of oxygen and are useless when" 118 U. S. AR^IY X-RAY MANUAL X-RAY PHYSICS 119 they no longer absorb this gas. For this reason, they ought to be protected from air when not in use. "Hypo" or Fixing. — The purpose of fixation is the re- moval of all unreduced silver, leaving the small specks of metallic silver suspended in the gelatin film. Any unre- duced silver left in the gelatin will sooner or later discolor and ruin the negative. By using acid and alum, the clear- ing is improved and the film of gelatin hardened. "Hypo" must be thoroughly removed by washing half an hour to one hour in running water, so that hypo crystals will not form in the gelatin, ruining the negative. If the bath is too acid a rash wall appear on the surface of the gela- tin. The acid should be partly neutralized by the addition of sodium carbonate. If the bath appears milky, it gener- ally lacks acid and can be cleared by the addition of acetic acid. Fog. — It is extremely important for every roentgenol- ogist to realize the full effect of fog produced on the nega- tive in development. This fog is the result of chemical action and is alw^ays produced to a certain extent. It is not uniformly distributed over the plate in any case, and is related to a certain extent to the exposure at the points where it shows. It has, always, the effect of blotting out the finer details. In a properly exposed and developed plate these finer details show as light areas against a slight- ly darkened background, as, for example, in the case of a mastoid plate. As soon as fog is produced to such an extent that these clear white lines become smoky, contrast W'ith the slightly darker background and adjacent areas may be entirely lost. Fog will always be produced if the developer is too w^arm, if improperly mixed, or if the time of development is too long. The only way to avoid it for a given plate is to use a proper concentration of the developer, a proper tern- 120 U. S. ARJ\1Y X-RAY MANUAL perature, and such an exposure as will enable complete development to be made before fogging action becomes ef- fective. The roentgenologist should invariably remember that a proper distribution of shadows on his plate or fluoroscopic screen furnishes the only physical basis for diagnostic use of his radiation, and to avoid the necessity of passing upon indefinite and unsatisfactory plates it is just as essential to pay attention to the darkroom conditions as it is to consider proper position and exposure. The diagnoses made on the basis of shadows that are so faint as to be invisible to the majority of observers introduce a very considerable ele- ment of imagination, and are relatively unsafe even for those who claim successful results on such a basis. Developing Formiilae. — Most x-ray operators had been using a hydrochinon-metol developer prior to the shortage of metol. Certain substitutes for metol have been marketed of more or less value. The following formulae have been found fairly good in practice : Hydrochinone — Water (warm) 1 gal. 5 gal. Sodium sulphite (dry) . . 8 oz. 40 oz. Hydrochinone II/2 " IY2 " Sodium carbonate (dry) 8 " -iO '' Pot. bromide 1 dr. 5 dr. Mix in order named. Good for tank development.. Elon-Hydrochinone — (Dissolve these chemicals in order named:) Water 20 oz. Elon 20 grs. Sulphite of soda (dry) 1 oz. Hydrochinone 80 grs. X-RAY PHYSICS • 121 Carbonate of soda (dr^O 1 oz. Potassium bromide 8 grs. Good for tank development. Edinol-Hydrochinone — Solution A Boiling distilled water 32 oz. Sodium sulphite (dry) 6 oz. Edinol 5 dr. Hydrochinone 1 oz. Potassium bromide 6 dr. Solution B Water 32 oz. Potassium carbonate 2 oz. Use one ounce of Solution A, one ounce of Solution B and two ounces of water. Develop 6 to 9 minutes. Good for tray development. Metabisulphite-Hydrochinone. — ^A professional photog- rapher doing considerable x-ray development recommends the following developer as very satisfactory for general work : Mix in order named. Solution A Water 200 oz. Hydrochinone 4 oz. Potassium metabisulphite 10 gr. Potassium bromide 50 grs. Solution B Water 200 oz. Sodium sulphite I14 lbs. Caustic soda 214 oz. These solutions keep well in stock. For use, mix in equal parts. 1^2 U. S. ARMY X-RAY MANUAL Fixing" Bath Formulae. — An acid hypo fixing bath may be prepared as follows: Water 64 oz. Hypo 16 oz. When fully dissolved add the following hardening solu- tion: Water 5 oz. Sulphite of soda 1 oz. Acetic acid (28% pure) 3 oz. Powdered alum 1 oz. If preferred, 1 ounce of citric acid may be substituted for acetic. This bath may be made up at any time in advance and may be used so long as it retains its strength, or is not sufficiently discolored hy developer carried into it to stain the negatives. Chrome Alum Fixing Bath. — This bath has good keep- ing qualities, fixes clean and remains clear after long con- tinued use. A Pure water 96 oz. Hypo 2 lbs. Sulphite of soda 2 oz. B Pure water 32 oz. Chrome alum 2 oz. Sulphuric acid, C. P % oz. Mix chemicals in order named. When dissolved, slowly pour B into A while stirring rap- idly. Notes on Fixing^. — Hypo is cheaper than spoiled plates. Use plenty and renew often. Wash all plates very thor- oughly to remove hypo. X-RAY PHYSICS 123 Do not strengthen an old weak hypo bath. Throw it away and make a new one. It may fix, but it is sure to spoil plates sooner or later. Failure to wash off developer will quickly spoil a fixing bath. Stained plates are usually due to one or more of the fol- lowing causes: Too warm developer. Too long development of under-exposed plates. Exhausted hypo bath. Lack of acidity of the hypo bath. Reducing Dense Negatives — Solution No. 1 Water 16 oz. Potassium f erricyanide 1 oz. Solution No. 2 Water 16 oz. Hypo 1 oz. Place plate in Solution No. 2 sufficient to cover it, then add a small quantity of No. 1, and watch it carefully. If it reduces too slow^ly, add more of No. 1. If only too dense in places, apply the solution carefully with a brush or tuft of cotton. Wash in running water at least a half hour after re- ducing. Note. — Make negative properly and avoid reduction. Darkroom. — The first consideration in a darkroom is the complete exclusion of ordinary light. All windows, cracks, knot holes, key holes, etc., must be stopped by opaque ma- terial. If possible, an entrance by corridor or winding way should be used. If a door is used it should fasten on the inside, so that no one can open it at an inopportune time. 124 U. S. ARMY X-RAY MANUAL The usual emulsion on x-ray plates is quite insensitive to red or orange-red light. A very small intensity of blue or white light will ruin a plate. The quality of light, not the amount, is what must be considered, and enough of a safe light may be used to see clearly what one is doing without danger of fogging a plate, if the operator is not too slow. The inner walls of the room should be painted red or orange, not black. A ruby 20-watt lamp, four or five feet above the working shelf with a translu- cent shade below it covered with postoffice paper, will give a diffuse illumination of the room very desirable for Fig. 54. Simple arrangement of light for developing. The slide contains a white and a ruby glass with yellow (P.O.) paper between. A clear lamp is used. work. Test the light by placing an opaque object on a small plate. Expose on the shelf for two minutes and develop full time ; if not fogged, the light is safe for that make of plate. If one desires to time development by look- ing through the plate, an arrangement as shown in Fig. 54 or one as sold by some dealers is desirable. By using a flexible cord, the lamp in Fig. 54 may be hung outside after the box is opened and serve as the source to be used when no plates are exposed to light. Arrangement. — Darkrooms may be quite elaborate and yet be very inconvenient. A simple arrangement for a small outfit is shown in Fig. 55. No doors are needed in this case. Fixing bath and supplies are to be kept apart from de- X-RAY PHYSICS 125 veloper and developing supplies. A plain open shelf is used in filling envelopes, etc. Cassettes, intensifying screens, and envelopes may be kept in suitable compartments below. Plates in small amounts may be kept in compartments above this shelf. An inexpensive arrangement serving all HYPO. INLET ^DEV. FIXING SUP PUBS SINK to o I DEVBLOP/NO SUPPLIES •30- PLATBS BELOW- CASSETTES AND ENVELOPES BELOW- DRYING RACK FAN PLATE LOAD- ING SHELF IN y-30- Fig. 55. A convenient darkroom arrangement. needs is shown in Fig. 56 for holding developer tank, fixing^ tank, and also serving as a washing tank. For a perma- nent installation the tank may be lead-lined, but for a semipermanent wooden tank a heavy coating of water and chemical-proof paint will suffice. In warm weather, use ice to cool bath, and do not dilute developer. Ventilation. — Good ventilation is essential in a dark- room, not alone to increase the efficiency of the operator, 126 XL S. ARMY X-RAY MANUAL but because a close, musty atmosphere is bad for the sensi- tive emulsion. When a new room is designed, the matter is quite simple, but when any old closet is regarded as good HYPO INLET D^V£L0P£R] Fig. 56. Wooden tank to permit circulation of water around de- veloper and fixer, provides for rinsing and washing films or plates at same temperature throughout. enough for a darkroom it is quite a different matter. The important point to be kept in mind is that air must be let Bracket Fig. 57. Simple ventilator for darkroom. All inner surfaces to be painted red or black. in and out, but light must be excluded. Where an electric fan can be used, it is easy to accomplish this result. Fig. 57 shows one way. The fan is placed in a box, open at each X-RAY PHYSICS 127 end, inserted through the wall. A second box is placed inside the room, as shown, and all surfaces are painted a flat black. Air has free passage, and light is entirely excluded. A similar arrangement can be used in a window, either with or without the fan. Humidity. — Basement darkrooms are often very damp in summer and very hot in winter. The best work cannot be expected under these conditions. If such must be used, it is best to keep unused plates elsewhere. Care of Utensils. — ^Absolute cleanliness is essential in darkroom work. Trays not in use are best kept filled with water. Be sure that no acid gets into the developer. Do not use developer or fixing tanks painted inside with any kind of water-proof paint. Supplies. — Be careful to keep all containers labeled, so that no mistakes are likely to be made. Keep hypo and acids away from developer material. Keep chemicals pro- tected from moisture. Remember that twice the weight of crystals must be used as in case of ' ' dry ' ' materials. Marking Negatives. — "Where a large amount of radio- graphic work is done, a well-organized record system is indispensable. In all cases the record should show in some way on the negative, and that record must be put on hefore the plate is developed. Lead numbers may be used, and if this is done the number used and the name of the patient must he entered on a suitable card or hook at the time the exposure is made. If numbers are not used, a slip showing the name of the patient must be attached to the cassette or envelope, and the darkroom operator should always write the name with a soft pencil on one corner of the emulsion hefore development. In using double-coated film care should be taken to mark right and left, as one cannot tell how the film was placed. 128 U. S. ARMY X-RAY MANUAL The X-Ray Negative. — The conditions which determine the distribution of shadows on an x-ray negative are ex- tremely complex and vary with the physical condition, age, and weight of the patient even without any reference to pathological conditions. If there were no material between the target and the photographic emulsion, there would result, upon exposurt and development, simply a uniform blackening of the plate. The introduction of material in the path of the radiation between the target and the plate results in absorption and scattering^ with the result that portions of the emulsion are protected from the radiation, the resulting shadow showing as a white or lighter area by transmitted light through the negative. The amount of radiation failing to reach any area of the plate as compared with that reaching the surface of the obstructing body depends upon two things: first upon the relative physical density of the material traversed as compared with its immediate surroundings and, second, upon the distance in this material of greater or lesser density actually traversed by the rays. As an illustration, the shadow cast by a thin, flat bone, placed with its surface parallel to the plate will show little contrast as compared with the shadow of the surrounding flesh, whereas, if placed on edge, increasing the path traversed in the bone, there will be marked contrast. In traversing the human body radiation passes through an aggregate made up of portions of decidedly different densities. Each of these portions absorbs the radiation in an amount depending both on its density and thick- ness. When we further take into account the physical nature of the action of the photographic plate and the different absorbability of the radiation under different conditions of tube, we may easily recognize the reason for the variety of negatives which it is possible to secure of X-RAY PHYSICS 129 the same anatomical region. Inasmuch as our diagnostic information must be acquired from a study of these areas, we must not forget that pathological conditions are liable to be inferred if based upon doubtful or imperfect data, and while Ave can not at present lay down complete rules for the guidance of the roentgenologist it is undoubtedly true that for each individual area there is a combination of factors of exposure, penetration, development, and position, that would give the best diagnostic plate. Consider the effect of varying (1) the quality of the x-ray beam, (2) the time of exposure when making a negative of any particular region. Assuming that we have proper development of the plate after exposure, we may note that if the tube has a small equivalent gap the major- ity of the radiation will be absorbed completely by even thin and non-dense portions of the patient, and that the exposure in order to have any effect on the plate must be prolonged. For example, in the case of the hand, such a tube with proper exposure may bring out wrinkles or folds in the flesh, finger nails, and a very slight infiltra- tion in the soft tissues, and only by prolonged exposure can even a moderate definition of bones be observed. When this is done the parts of the negative covered by soft tissue are greatly overexposed. If the spark gap is too small nothing but a shadow of the hand such as would be cast by ordinary light will be observed. As we change the spark gap with a suitable time of exposure we can secure quite different qualities of negative and, with a moderate gap and exposure, fair details in the bone and the soft tissue may be observed, but, with longer exposure, portions of the plate beneath the thinner or softer regions still become overexposed, giving, on de- velopment, complete blackness without details. At the same time the outlines of the thicker portions and of the 130 U. S. ARMY X-RAY MANUAL bones may stand out very clearly, giving almost the ap- pearance of a skeleton. If the spark gap is made too high the radiation reach- ing the plate may be only modified to a slightly greater extent by the bones than by the soft tissue, and we get a characteristic plate, lacking in contrast, which is generally described by the term ''flat." In an extreme case, nearly all of the radiation might pass through the body with only a trifling amount of absorption, and there would be no differentiation with reference to density and thickness upon the plate. Consequently, while no complete guide can be given, the general effect of increased spark gap is to reduce the contrast, and the general effect of increased exposure with moderate gap is to obliterate the details in the soft tissue or thin portions with an increase in the visibility of the shadows cast by the denser or thicker portions. If, for example, one desires a study of the thoracic vertebrae, one must expect that portions of the plate receiving radiation through the air-filled lungs will be greatly overexposed and will indicate no shadows. With a softer tube, details of the spine and ribs will be less obvious, while the linear markings in the chest are rendered visible. It naturally follows that tube condi- tion and exposure should be adapted to bring out the information desired. Mention may also be made of the fact that the overexposed and denser regions may fre- quently give valuable information if viewed with a suffi- ciently strong source of light, while a thin negative, or those portions in which the shadows are faint and the total blackening slight, are best observed in weak light. Inference as to pathology can only be safely made when due account is taken of the variation in the shadows due to normal variation in human anatomy and the procedure followed in making the negative. X-RAY PHYSICS 131 o O Form 651 Medical Department, U. S. Army (Revised July 19, 1917) CLINICAL RECORD RADIOGRAPHIC REPORT Station. Date From To 191 Information requested:. Clinical diagnosis: ., U. S. Army. Laboratory X-ray findings: ., 191 PLATE NUMBER SIZE PART DISPOSITION , U. S. Army. SURNAME OF PATIENT CHRISTIAN NAME RANK COMPANY REGIMENT OR STAFF CORPS Fig. 58. Eeeord and report form for x-ray examination (actual size 3% ins. x 8 ins.). 132 U. S. ARMY X-EAY MANUAL Records. — The importance of the correct recording of all information obtained by means of the x-ray cannot be overestimated. Of equal or greater importance is the establishment of the identity of the patient examined with the x-ray findings. Furthermore, the identity of the side examined should be verified in every case. That the x-ray findings are brought to the attention of the attending surgeon is essential. An actual conference between the surgeon and the roentgenologist is very desir- able in order that each may have the advantage of the other's personal opinion. Each plate should, therefore, be marked for identifica- tion by means of opaque markers and the corresponding information immediately recorded on the blanks provided for this purpose. Form 551 Medical Department, U. S. Army (Revised July 19, 1917), will be used for this purpose. Fig". 58. In all cases a duplicate of this report should be retained. LABORATORY EXPERIMENTS Laboratory Instruction in Preparation for Roentgenol- ogy. — The following experiments are part of a series used in the laboratory course. They were easier of execution in the laboratory in which they were devised, and results were more conclusive, on account of having a very good high tension voltmeter so that tube voltage measurements could be accurately and quickly made. The objects of such experiments are: 1. To give practice in quickly adjusting machine and tubes to any desired current and voltage. 2. To impress on the mind of the student the relation of the fundamental factors — voltage, current, distance and time — to the nature of image desired. 3. To assure the operator that results are reproduci- ble if conditions are right. 4. To show some of the pitfalls usually encountered and to avoid having to acquire experience on the living patient. While at first such experiments may seem very time- consuming, experience has shown that the skill and con- fidence acquired will much more than repay it in a com- paratively short time. New students, and even those of some experience, are likely to have trouble in handling the apparatus if it has many unusual details. They should, therefore, read such paragraphs of the manual as deal with the elementary principles, before starting experimental work. 133 134 U. S. ARMY X-RAY IMANUAL The Coolidge tube is used in these experiments on account of its easy adjustment. Experience indicates that when taking the same current at the same voltage all tubes give very much the same density of negatives, so that ex- posures learned on the Coolidge tube apply to the gas tube in so far as the conditions can be made the same. Experience in the training of a considerable number of students has clearly shown that the handling of x-ray apparatus cannot he learned by seeing some one else do it. Only when the students have repeatedly carried on the actual manipulations themselves, time after time, can they be depended upon under working pressure. Much time is lost in not knowing just what exposures should be given and the test plates described are excellent checks on accu- racy and rapidity. The student should be well drilled in quickly setting the tube and control for definite readings. In the study of plates as well as in the technical work the student should do absolutely individual and independ- ent work. Instruction Unit. — A small instruction unit has been devised to clearly set forth the basic principles of the large x-ray machines and to avoid unnecessarily tieing up ex- pensive equipment for elementary instruction purposes. This machine is composed of only the customary elements and these are arranged on an ordinary pine table so that all parts and all wires are completely in view and readily accessible. For instruction purposes high power is un- necessary, and a small transformer is ample for the pur- pose. With the transformer used, loads up to 5-inch gap, 30 ma., may be safely drawn for test plate and other experimental work. The autotransformer, rheostat, fila- ment transformer, timer, etc., are standard parts as used on the large machines, so that the student may become familiar with their function and operation. LABORATORY EXPERIMENTS 135 It is intended to have the machine as simple as it is possible to make it, and to this end the various circuits are distinguished from each other by the color of wire used. Thus, the main primary circuit is black, the motor circuit is blue, the Coolidge filament primary is red, and the remote control circuit is green. Even to a beginning student the circuits stand out separate and distinct, and the machine appears organized and rational rather than fsr| \^ Main Primary Circuit Auto- trans: SO Fig. 59. Diagram of connections of instruction unit. a hopeless maze of wiring. Fig. 59 shows the diagram of connections and Fig. 60 shows the machine itself. Su- perfluous parts have been eliminated and the features shown are so fundamental that each student should be able to wire up the complete machine as part of his labora- tory work. Aside from giving a knowledge of the electrical elements of x-ray machines, the unit is used to give considerable practice in setting for any desired tube voltage and milli- amperage, in operating when failure of some non-essential 136 U. S. ARMY X-RAY MANUAL element occurs, and in studying the physical properties of the x-rays. Test Plates. — The quantitative measurement of x-ray radiation has proved a difficult matter, but for our pur- FiG. 60. Machine used for instruction purposes. All parts and wiring are openly displayed. pose the photographic effect is sufficiently accurate and determines the usefulness of the rays in practice. We cannot readily compare the radiation received on two spots of unequal density. Under any conditions of operation, however, if two portions of a photographic plate subjected to radiation and given the same develop- LABORATORY EXPERIMENTS 137 ment have equivalent blackening: we may say that the two parts received the same quantity of photographically effective radiation per unit area, or that they had the same exposure, in which case exposure does not mean time alone. If a spot exposed 1 second and a spot exposed 2 sec- onds are of equal darkness, then we can say that the first spot was subjected to radiation twice as intense as the second, for it took only half as long to give equal effect. The spots should not be heavily overexposed or over-developed, for it is in the medium gray tones that distinctions in density are most accurately and easily made. A 5 X 7 plate is cased in the usual envelope or in a light-tight plate holder. The student's name, laboratory number and the number of the experiment should be written on the emulsion side of the plate with soft lead pencil when loading. A 5 x 7 lead plate with ten 1- inch holes is used to protect the body of the plate from radiation and all holes except the one spot to be ex- posed are covered with sheet lead. Expose the test spots in proper sec[uence down the two rows of holes, and place a small metallic marker on spot No. 1 during exposure to identif}^ it later. In using a timer do not vary its settings, as the scales are rarely calibrated with sufficient accuracy. Keep the timer set at 0.1 second and repeat the exposure the re- quired number of times. If the machine is not equipped with a timer capable of conveniently repeating 1/10 sec- ond exposures, time with a stop watch or by counting to full seconds instead of tenths. Increase considerably the target-plate distance in this case, if possible. Do not develop test plates too far. Stop as soon as 138 U. S. ARMY X-RAY MANUAL spots Nos. 1 to 5 show fairly well on the back of the plate. If the settings have been carefully made and ex- posures accurately timed, spots Nos. 1 to 5 should be ap- proximately equal in density and Nos. 6 to 10 should run successively darker or lighter as the case may be. "When the finished plates are dry the spots should be numbered and all exposure data written on the emulsion side of the plate with pen and ink. The plate should then be turned in for inspection and credit. Before commencing work read and understand the gen- eral instructions and precautions on page 20. Distance-Time Relation— Inverse Square Law. Test Plate 1. — The x-rays travel out from the electron impact point on the target in straight lines, so that the amount in a cone of a given angle is spread over an in- creasing base area as we recede from the tube. A plate of fixed size intercepts more radiation in a given time when close to the source. If we move a plate to double its origi- nal distance from the target, the radiation received per sec- ond on a given area will be only 14 as great; at ten times the distance, 1/100 as great. In order to secure the same radiation effect, the time of reception must be increased four-fold in the first case and one hundred fold in the latter. For constant tube current and voltage the plate black- ening will be unchanged if we keep ^— con- distance ^ stant for all exposures. Set for 10 ma. at a 3-inch spark gap and expose spots as shown below. Or the bedside unit may be used, ex- posing seconds instead of tenths. LABORATORY EXPERIMENTS 139 Spot Spot Xo. Distance Time No. Distance Time 1 10 in. .1 sec. 6 10 in. . .1 sec 2 20" .4 " 7 20" .1 " 3 30" .9 " 8 30" .1 " 4 40" 1.6 " 9 40" .1 " 5 50" 2.5 " 10 50" .1 " In the first row of spots we have compensated for the change in distance b}^ a proper corresponding change in time, so these spots will have the same density. In the second row we have made no such compensation and the spots will not be equally dark. The target-plate dis- tances ordinarily used in radiographic work vary from 15 to 36 inches. The sharpness of the radiograph increases with greater distance, but longer time is required. As- suming that 1 second is the correct exposure for a given object at 20 inches, plot a curve on cross section paper showing time required at various distances up to 36 inches to give the same density of plate. Current-Time Relation. Test Plate 2. — The x-ray energy on a given plate area per unit time when the voltage is constant and the target- plate distance is fixed, increases in direct proportion to the current. Thus, we get the same radiation in half the time when using 50 ma. as when using 25 ma. Or, for equal photographic effect the product of milliamperes and sec- onds must remain constant. To test this law expose a test plate as follows : Voltage constant at a 4-inch gap. Target-plate distance constant at 30 inches. 140 U. S. AR]\1Y X-RAY MANUAL 5pot ; Current Time Spot Current Tim 1 5 nia. 1.2 sec. 6 5 ma. 1.2 se 2 10 '' .6 '^ 7 10 '' 1.2 '' 3 15 '' .4 '' 8 15 ^^ 1.2 '' 4 20 '' .3 " 9 20 '' 1.2 '' 5 30 '' .2 '^ 10 30 '' 1.2 ^' Notice that we have compensated by a decrease in time for the increase in current in the first row and that the second row is uncompensated. Voltage-Time Relation. Test Plate 3. — The radiation leaving a given target as registered by a photographic plate is not fixed by the amount of current alone, but varies greatly with the drop in voltage through the tube. In fact, it increases very nearly in proportion to the square of the voltage. This means that on doubling the voltage, all other factors re- maining unchanged, we get four times the photographi- cally effective radiation per second and would then need but one-fourth the exposure time. "With an electrostatic high tension voltmeter it is easy to read voltage directly, but this instrument is not ordi- narily available. The so-called primary "kilovoltmeters" with which many machines are equipped are not reliable indicators of secondary voltage, as they do not read the same for the same secondary voltage under different loads on the transformer. Parallel sparking distance between blunt points is our best available guide to tube voltage. The relation between spark length and kilovolts is shown in Fig. 12. It may be considered as reasonably true that LABORATORY EXPERIMENTS 141 under average conditions the kilovoltage is ten times the spark in inches plus ten, i. e., 3-inch gap = 40 kv. ; 5V2-inch gap =: 65 kv., etc. Exposures are to be made as follows: Current constant at 5 ma. Distance constant at 25 inches. Spot Gap Time Spot Gap Time 1 2'' (30 kv.) 1.6 sec. 6 2'' (30 kv.; ) 1.6 sec 2 3" (40 " ) .9 " 7 3" (40 " ] ) 1.6 " 3 4'' (50 " )■ Q^^ Shutter Sliqhtlj opened fife- Fig. 71. (a) Correct position of shadow of plumb bob. Tube properly centered. (b) Projection of plumb bob on fluorescent screen, incorrect posi- tion. screen is down close to the table with the carrier locked against longitudinal motion and against rotation, raise the screen by the vertical movement of the carrier and see whether it retains its symmetrical position. An idea of the amount by which the tube needs to be shifted may be ob- tained in this way. It is also suggested that, if the tube needs to be moved in the direction in which the holder slides out of the box, one can slide the holder itself out and test for correctness, NEW APPARATUS 167 measure the distance, and finally shift the tube the same amount. The U. S. Army Portable X-Ray Unit. — By the coopera- tion of various manufacturers a semi-portable outfit has been developed which may be used in mobile units. The unit is shown in Fig. 72 and diagramatically in Fig. 73. The important features of the outfit are the portable power plant, the self-rectifying Coolidge tube, and the Fig. 72. United States Army portable x-ray unit complete. special table. Having the complete generating equipment, it is admirably adapted to service in strange territory where the electrical supply is not suitable for standard ma- chines or is likely to fail because of war conditions. The gasoline engine is direct-connected to a generator which supplies power for the x-ray and filament trans- formers (a.c.) and a small amount of current (d.c.) for the control circuit. The primary circuit requires no con- trol resistance, regulation for the two working settings being made by shifting the throttle by means of the d.-c. 168 U. S. AR]\IY X-RAY MANUAL XRflY TUBE FlLFIMENT THRNSFORMER C0MI)E/\f5EH BLRCK Fig. /3. Wiring diagram for United States Army portable x-ray unit. Dotted lines show connections for those machines having spe- cial control. In other cases these wires are omitted. NEW APPARATUS 169 control circuit, changing the speed and thereby the voltage of the generator. The secondary circuit contains no rec- tifying device since the tube allows only each alternate half wave to pass. (See page 36 for a description of the tube.) Fluoroscopic work is done at 5 ma. and all radiographic work at 10 ma. The maximum operating gap is about 5 inches, but may be reduced if desired by control of the machine speed. Owing to the drop in line voltage upon closing the operat- ing switch, it is necessary to secure a uniform filament cur- rent by inserting a ''booster" in the primary circuits of the two transformers. This is merely a small transformer, which by carrying the main transformer primary current adds enough voltage to the filament transformer primary to compensate for the drop of voltage in the line. Engine.* — The engine must be firmly fastened to a solid base by means of lag bolts or by some other convenient method. All fuel must be strained when filling tank, as impurities of any kind are certain to clog fuel pipes. Use a good grade of medium oil and always make sure that the crank case is well filled before starting engine. To start the engine, turn the fly-wheel rapidly by means of the crank, immediately remove crank and then press starting button and cut off air by means of lever on mixing valve body. When the engine has run for a few seconds, advance air adjustment lever to the point where the engine runs regularly and with the leanest possible mixture. A little practice will enable the operator to do this very quickly. This adjustment will vary with climatic condi- tions and the kind and grade of fuel used. It will be found to be slightly different when the engine has warmed up from what it was when the engine was started. * See also "Delco" circular on model 9011, furnished by the manu- facturer. 170 U. S. ARI\IY X-RAY MANUAL If the engine does not start, a few simple tests may determine the cause. Go carefully over all wiring and be sure that all electrical connections are tight and clean. Test to make sure that starting battery is not exhausted. Examine the spark plug carefully and if the porcelain is broken or cracked, replace plug with a new one if possible. Hold the spark plug connecter about y^ inch away from spark plug terminal and turn fly-wheel over several times by means of the crank and see if a good spark is obtained in this manner. If not, the plug may be greasy or dirty; remove and clean thoroughly with gasoline and adjust the distance between the points to about 1/32 of an inch, or until a dime can be just passed between them. Next, look at timer contacts to see that they are properly adjusted and are making good contact every time they close. If necessary, clean these contacts with a piece of fine sand paper. To adjust the distance between the points turn the engine over until the points open to their full extent. In this position a dime should just slip between the points. If necessary, adjust them by turning the contact screw in or out until the proper distance is obtained. Next, examine commutator and brushes. The commuta- tor may be dirty or greasy. It should never be allowed to remain in this condition, if the generator is to operate at maximum efficiency. Hold a piece of clean cloth soaked in a little kerosene against the commutator while the engine is running. Never use oil other than kerosene on com- mutator and always wipe dry with a piece of clean cloth afterwards. Examine brushes to see that they are in good condition and are making good contact. To test your fuel line, fill the priming cup from a small oil can with gasoline, and crank. If the engine will run when using gasoline from the can, and will not run other- NEW APPARATUS 171 wise, it indicates that fuel connections are loose or that the fuel hole in mixing valve bod}^ is clogged. Be sure there is no water in the gasoline tank. The fuel hole in mixing valve body or line may be cleaned out by blowing through it or by means of a fine wire. These few tests will usually locate the trouble. Now look at the cable leads which are all stamped wdth a corresponding number on the engine switch board. Be sure that they are properly con- nected to both engine and transformer unit. The amount of gasoline on continuous fluoroscopic work will be about 1 gallon per hour. On intermittent work, as is usually the actual case, a gallon w^ill last about 3^ hours. Note. — It may be noted that the wdring diagram as in- dicated for the portable unit has three wires to the voltage control, and that the x-ra}^ switch has to open and close a circuit, on the left, through this coil and, on the right, through the x-ray transformer. This arrangement w^as made in order to speed up the engine promptly when put under load, but it has been found unnecessary^ In some of the earlier machines, and perhaps in the later ones, this connection may be absent. When this is the case the wiring will be somewhat simpler, since the number of connections will be reduced and a slight change of design of the box may be possible. The Transformer Unit. — The x-ray transformer unit contains the apparatus needed to transform and control the currents necessary for energizing the radiator type Coolidge tube used with these outfits. It consists of the following parts: (Figs. 7-1 and 75.) The x-ray transformer (1) transforms the low tension alternating current from the gasoline engine generator unit into suitable high tension current. The filament transformer (2) supplies the low tension current for heating the filament of the x-ray tube. 172 U. S. ARMY X-RAY MANUAL The booster transformer (3) keeps the filament of the x-ray tube constant. The filament control (4) varies the amount of current Fig. 74. Instrument box for portable unit, front view. passing through the x-ray tube. A small knob will be found projecting from the side of this regulator — this is to open and close the circuit through the primary of the NEW APPARATUS 173 filament transformer. When pushed in it is closed, as it should ordinarily remain. The engine rheostat (5) serves as a means for controlling the speed of the gasoline engine. Moving the contact to- ward the front of the box increases the speed of the engine and thus raises the voltage of the generator. The x-ray switch (6) opens or closes the circuit to the primary of the x-ray transformer and to the auxiliary throt- tle control. The voltmeter (7) measures the voltage of the generator. The milliammeter (8) measures the amount of current passing through the x-ray tube. The main terminal board (9), whose five terminals pro- ject from rear side of the case, provides a means for con- necting the x-ray transformer unit to the gasoline engine generator unit by means of the cable. The pull switch terminal board (10) is, as the name indi- cates, for the purpose of attaching a pull switch to the apparatus. The split lugs at the end of the switch cable are to be inserted into the sockets in this terminal board to connect the pull switch in circuit. These connections put the pull switch in parallel with the x-ray switch and per- mit the closure of the circuit by either independent of the other. After the engine and x-ray table are set up, place the x-ray transformer unit in position, close to the end of the table and so that the high tension outlets are equally spaced between the legs of the table. This is very im- portant and should not be forgotten. Unlock the box, raise the lid to an angle of about 45° from horizontal, and slide the cover of the box slowly to the left until the two hinge sections have been disengaged one from the other. The cover can now be removed from the box. 174 U. S. ARMY X-RAY MANUAL Pull out the two door bolts. The door in front can now be let down so that work can be done readily in the in- terior of the box. This door should be kept open at all times when the unit is in operation to avoid damage by corona, etc. Push the split terminal lugs at one end of the cable into FiG. 75. Instrument box for portable unit showing instruments, high tension terminals, and openings for connections. the sockets on main terminal board. These lugs are of dif- ferent sizes so that they will only fit one way in the termi- nal board, and no mistake should be made. Connect the numbered lugs at the other end of the cable to the corre- spondingly m'arked connection posts on the switch board of the engine. Connect pull switch, if one is to be used, by inserting the split lugs on the switch cable in the sockets in the pull switch terminal board. The high tension terminals (11) and (12) will be found NEW APPARATUS 175 held in place in the cover by means of a clamp device. These terminals should be removed and screwed into the sockets. These sockets and terminals- are provided with different sized threads at their ends so that the terminals can only fit into their proper socket. The high tension terminal (11), provided with the spring hook terminal, screws into the single socket. The remaining terminals (12) can be screwed one into each of the remaining sockets. Attach the cord from the positive terminal to the posi- tive terminal of the tube box and the cords from the two negative terminals to the two binding posts on the nega- tive terminal of the tube box. Open the x-ray switch, the pull switch, and the line switch on the board of the engine ; move the sliding con- tact of the engine-rheostat as close to the hinge side of the box as it will go. Start the engine and close the switch on the switch board of that unit. The filament of the tube should now be incandescent. Slowly move the contact on the engine rheostat toward the front of the box. The voltmeter should indicate higher and higher voltage. Con- tinue until the voltmeter indicates about 160 volts. For radiographic work, having adjusted the engine speed by means of the engine rheostat until the voltmeter reads 160 volts, set the filament control at 1.9, close the x-ray sw^itch and readjust the engine rheostat and filament control until the milliammeter reads 10 ma., when the volt- meter should read from 110 to 115 volts. Now open x-ray switch and read the voltage generated at no load, leaving the rheostat set in the 10 ma. position. Hereafter, whenever radiographic work is to be done, sim- ply adjust the engine rheostat until the voltmeter indicates the voltage thus found. To obtain the operating point for fluoroscopic work, viz., 176 U. S. ARMY X-RAY ]\IANUAL 5 ma. at from. 110 to 115 voltmeter reading, reduce the speed of the engine by means of the engine rheostat until the milliammeter indicates 5 ma. Upon examination of the voltmeter, it will be found to read from 110 to 115 volts. Open the x-ray switch and read the voltage gen- erated at no load, leaving the engine rheostat set at 5 ma. point. Hereafter, whenever fluoroscopic work is to be done, ad- just the engine rheostat until the voltmeter again reads the voltage thus found. In order to save fuel and wear and tear on the engine, it may be advisable to run the latter on reduced speed, except when making a radiograph, or during a fluoroscopic examination, or when it is desirable to use red room lamps designed for this unit. For this reason an adjustable stop is provided on the engine rheostat. This stop is set to bring the engine to proper speed for the work in hand, so that during the interval between making radiographs or fluoro- scopic examinations, the engine speed can be reduced and reset for the next operation by merely running the contact against the adjustable stop. This x-ray transformer unit should, as far as possible, be kept dry inside and out, and should be kept covered with a tarpaulin when not in use. Care should be taken to prevent sudden jarring and rough handling generally, to minimize the danger of putting meters, etc., out of adjust- ment. The filament control must be adjusted carefully to give the proper current and primary voltage, and once adjusted it will stay fixed. Make sure the filam.ent is lighted be- fore throwing on power : this may easily be forgotten with an enclosed tube. Should a spark pass in the secondary circuit when -the operating switch is closed, it may be due to a temporary NEW APPARATUS 177 surge. Unless an ''arc" results, do not open the operating switch. Keep secondary wires well apart and well away from other objects to prevent corona and leakage. It is a good plan to connect the frame of the table to any con- venient ''ground." Red Light for Fluoroscopic Room. — The generator may readily serve to give the reduced red light needed in fluoro- scopic work. Fig. 76 shows how this is done ; and either a ROOM LICiHT HIGH TENSION TO TUBE TRANSFORMER BOOSTED PRiriPiRy Fig. 76. Connections for red lamp over the fluoroscopic table, when used with portable unit. high voltage ruby lamp or two 16 candle power, 110 volt ruby lamps in series are required. Do not connect in ex- cept as shown and do not attempt to load the generator up with additional lights or apparatus. Pulling the string switch alternates x-ray excitation and darkroom illumina- tion. The extension cord and light connect onto the box at 13, Fig. 75. Limitations. — This instrument w^ll do the work for which it is designed, but must not be abused. Do not use the radiator type Coolidge tube on large installations or interrupterless transformers. It is not furnished for this purpose. It should only be used for radiographs at 10 178 U. S. ARMY X-RAY MANUAL Fig. 77. United States Army bedside unit, complete for alternat- ing current operation; double throw switch to be drawn to the right, loose connections below for rotary converter in using direct current. ma. for a maximum exposure not exceeding 45 sec. with two minute intervals between. For fluoroscopic work it may be operated continuously, long enough for all practi- cal necessities, at 5 ma. Do not attempt to use this tube at NEW APPARATUS 179 other than these settings. Never attempt to operate the tube without the radiator. The U. S. Army Bedside X-Ray Unit. — The unit shown in Fig. 77 was designed to permit x-ray examination in wards to be made with a minimum of disturbance of the patient. Many cases of fracture and other bone lesions, as well as various chest conditions, need such examina- tions. Pressure on the main x-ray outfit is often reduced and time saved by using such a unit. This unit consists of a combined cabinet and tube stand, a radiator type Coolidge tube, special lead glass shield, and a transformer and control apparatus. The latter are enclosed in the cabinet. Transformer. — The transformer (1) is designed to operate on alternating current of any ordinary frequency, if properly connected for the supply voltage available. Since the same primary circuit supplies power for both filament lighting and x-ray operation only one switch needs to be opened or closed. Tiibe. — The radiator type of tube (2) with a special molded lead glass shield is used exclusively on these units. The tube will operate continuously with 5 ma. at a voltage sufiicient for fluoroscopic work. T 111)6 Stand. — The tube stand (3) is counterbalanced and permits placing the tube in any desired position. It was made with a long horizontal extension to allow work over the top of a bed. The position of the tube during a fluoroscopic examination should be controlled by a prop- erly trained assistant. See Fig. 78. Limitation of Tube Current. — This outfit was not de- signed to permit variation by the operator of either cur- rent or voltage. The power limit was fixed by the usual fuse capacity of interior wiring for lighting purposes. More power would tend to blow fuses and thus interfere 180 U. S. ARMY X-RAY MANUAL with other uses of these circuits as well as delay the x-ray work. It gives a g'ood average result when two conditions are met: (1) a tube current of 5 ma.; (2) a proper low tension voltage applied to the transformer terminals. Service Conditions. — The user may find it necessary to operate on any one of the following supply systems. Fig. 78. Positions of parts when using the bedside unit with simple vertical fluoroscope for chest examination at the bedside. 1. 110 volt — alternating current. 2. 220 volt — alternating current. 3. 110 volt — direct current. 4. 220 volt — direct current. Operation. — To operate this unit the first thing that it is absolutely necessary to know is whether alternating or direct current is supplied and at what voltage. Where any NEW APPARATUS 181 question exists as to this point, no attempt should be made tc operate until all doubts are settled. This unit will operate satisfactorily on 110 volt alternat- ing current with no accessories. If the supply is 110 volt direct current, a rotary converter must be used. Fig. 79. This is connected by cables which will be found properly connected to the switch in the cabinet. Two leads are to Fig. 79. Eotary converter used for direct current operation. U. S. Army bedside x-ray unit. be connected to the binding posts on the rotary marked d.c, and the remaining two to the a.-c. terminals of the rotary. No mistake should be made, as these cables are plainly marked. On 220 volt, direct current, this unit may still be used, but a 220 volt rotary will be required. The rotary converter for 220 volts is mounted on a wooden base and has a suitable series resistance. This rotary is designed and adjusted to give 110 volts a.c. at the collector rings under load. ^4=^ TJ^ftNSFORMEn M ,r ^x ^ r(9 LINE FU6E '^ r 3= ,^^"7^ ^ 70 OFBRRTING SWITCH TO FOOT ew/TCH TiOWFY CON\/BRTOR Fig. 80. Wiring diagram for connections, United States Army bedside unit for 110-220 volt, d.c. or 110 volt a.c. 182 NEW APPARATUS 183 X-Ray Transformer. — The x-ray transformer has three bmding posts numbered 1, 2, and 3. One and three are used in all cases except for 110 volt direct-current opera- i^UTO JBRNSF ORMEFi ■ftC DC' n □ r~c h- Z20 VOLTS ftC L TO mrmy TO OPEnflTlNG SWITCH TO FOOT SWITCH Fig. 81. Wiring diagram for connections, United States Army bed- side unit for 220 volts a.-c. circuit. tion, for which numbers 1 and 2 are used. When the wire is removed from part three it should be taped so as not to make an accidental contact. Fig. 80 shows in full lines the connection for 110 volt d.c, 220 d.c. and 110 a.c. The switch must be closed on d.c. for both direct-current volt- 184 U. S. ARMY X-RAY MANUAL ages, and on the a.c. side for both voltages of alternating current. If the current is 220 alternating a special autotransformer is required. The one that is supplied has three wires marked 1, 2, and 3. To connect up for this voltage (Fig, 81) transfer the line wires to terminals 1 and 3 of the auto- transformer and connect 1 of the x-ray transformer to 2 of the autotransformer and 3 of the x-ray transformer to 3 of autotransformer. Tube. — The radiator type Coolidge tube will be used exclusively on these outfits and little or no adjustment can or will be left to the operator. This tube does not require a rectifier of any description and will safely carry 5 ma, for an indefinite time. For radiographic work it is advis- able to use intensifying screens. To Adjust the Tube — 1. Remove radiator after loosening screw at the end. 2. Carefully place the two halves of the lead glass shield (4) over the tube and fasten together by means of the screws. Do not turn screws tight or a broken shield is sure to result. 3. Turn the tube so that the center of the target is in line with the opening in the shield (5). 4. Push the cork wedges, which are supplied, in around the target end of tube first, then in around cathode end so as to hold tube firmly in this position. Replace radia- tor. If this screw does not turn easily, hold the tube by the radiator and not by the glass. Never attempt to operate this tube without the radiator in place. "When placing the tube in the holder be sure that the shield containing the tube is clamped in the holder (6) and not the tube ends. To adjust the aluminum filter, which it is necessary to use at all times, loosen the two screws that hold the shield together each side of the opening, place the NEW APPARATUS 185 aluminum filter in position and retighten screws, always re- membering tliat glass will break if fastened too tight. The diaphragm with the round hole will cover an area 5 inches in diameter at 20 inches target-screen distance, and the square opening an area 14: inches square at the same tar- get-screen distance. A strip of lead foil may be attached by adhesive tape over the crack between the two halves of the lead glass shield. After everything else is ready connect with your source of current and make sure that you throw the two-way switch to the correct side. Both ends are marked and there can be no excuse for not doing this right. After throwing this switch, watch the milliammeter. If it goes to more than 5 ma., adjust the resistance wire on the top of the terminal inside the cabinet, increasing the amount included between binding posts; if less than 5 ma., reduce the amount so included until the milliammeter reads between 4i^ and 5 ma. This apparatus, operated as directed, will do the work for which it was designed. The operator should not at- tempt any adjustments other than those described. All others have been attended to by the designers and makers. It is intended that intensifying screens should be used with this unit for all radiographic work, unless immobili- zation is easily accomplished. Care in Moving. — The tube holder permits of placing the tube as shown in Fig. 77, so that when moving in a ward there is less danger of collision between the tube and other objects. Always move carefully as the tube is frag- ile. "When the holder is extended the cabinet is less stable, and even more care must be taken. AYhen moving up or down stairs always remove the tube and clamp. Exposure. — The exposure recpiired with this outfit will depend on conditions as to film or plate, and on whether 186 V. S. ARMY X-RAY MANUAL an intensifying- screen is used and its speed. If one is accustomed to using 40 ma. at about a 5-inch gap, with the same conditions as to distance and plate or film, the time of exposure is to be multiplied by eight. Using an inten- sifying screen will reduce this exposure an amount depend- ing on the multiplying power of the screen used. A good screen will reduce the, exposure time to from 1/10 to 1/15 of that required with no screen, when a plate or a single- coated film is used. If a double-coated film is supplied, the time without screens is reduced to %. For double-coated film and single screen, the time is further reduced, under good con- ditions, to about 1/25 or 1/30 of that for single coating and no screen. An excellent chest negative of a man of average size has been made with the following settings: Target-plate distance — 28 inches. Current — 5 ma. Eastman double-coated film. Edwards screen (single). Exposure time — 1 sec. A little care and practice will enable one to do a large amount of work at a minimum of disturbance or discom- fort to the patient and with quite reasonable exposure times. Accessory Apparatus. — Hand fluoroscope 5x7, the usual type for examination of extremities. Fluoroscope for chest examination with special support. See Fig. 78. This can be folded and disassembled for mov- ing from place to place. Reducing goggles are furnished to enable the operator to find his way around a lighted room and then proceed at once to do reasonably good fluoroscopic work. These con- tain a red and a green celluloid disc; for a fairly dark NEW APPARATUS 187 room the red alone may serve, for a brightly lighted room both are inserted. Just before bringing the fluoroscope in position, close the eyes, raise the goggles to rest on the forehead, and open the eyes only after the fluoroscope is in position. Reverse these steps when the examination is completed. Fluoroscopic Unit. — ^For the most successful and con- venient fluoroscopy the operator should have control over both screen brightness and the penetration of the rays. A unit embodying these control features and of correct ca- pacity for operation with the self -rectifying Coolidge tube has been devised and is in limited use in connection with the horizontal and vertical fluoroscope, although not offi- cially adopted and regularly supplied by the government. The transformer is about the same size as that used in the bedside unit but differs in having entirely separate high tension and filament transformers in the same case, rather than two secondary windings energized by the same pri- mary as has the bedside unit. The primary of the high ten- sion transformer and the primary of the Coolidge filament transformer may be separately controlled by turning two knobs on the control cabinet, giving various tube currents and voltages with a much simpler adjustment than here- tofore in use. This unit serves, in those instances where it is installed, to remove the fluoroscopic work from the large standard machine and thereby increase the capacity of the x-ray room without the addition of another high power outfit. It can be run from 110 volts a.c, from 220 volts a.c. by means of a small autotransformer, or from 110 or 220 volts d.c. with a suitable rotary converter. A wiring diagram is supplied with the machine. STANDARD POSITIONS It has been the endeavor, in the following series of pho- tographic reproductions of the various parts of the body, to illustrate what seem the simplest and most reliable methods of securing x-ray plates of these various parts, which are of most value in determining both the normal and the pathological structure. Fig. 82. Position: (a) clavicle (b) shoulder joint. The necessity for a thorough knowledge of normal x-ray shadows is too apparent to need further discussion here. No amount of study and observation of pathological or abnormal conditions will be of value unless the individual has first acquired a true concept of the normal. In order 188 Fig. 83. Elbow, lateral view. Fig. 84, Elbow, anteroposte- rior view. Fig. 85. Wrist, anteroposte- FiG. 86. Wrist, lateral view, rior view. 189 190 U. S. ARMY X-RAY MANUAL to obtain such a concept some method must be followed which will give the least amount of variation in the ap- parent size, shape, and relation of the parts examined when attempting to reproduce the same results in the same or different patients. This is essentially the funda- FlG. 87. Hip joint, anteroposterior view. mental principle of all x-ray interpretation. It has been found by roentgenologists that this can only be accom- plished by establishing standard relations between the source of the rays, the sensitive plate and the part to be examined. This is what is meant when speaking of the standard positions for the different parts of the body. It must be constantly borne in mind that even a slight change STANDARD POSITIONS 191 m Fig. 88. Knee, antero- FiG. 89. Knee, lateral view, posterior view. Fig. 90. Ankle, antero- posterior view. Fig. 91. Ankle, lateral view (mark- er over internal malleolus). 192 U. S. ARMY X-RAY MANUAL Fig. 92. F o o t, anteroposterior view. Fig. 93. Foot, lateral view, mark- er over first metatarsal. Fig. 92 Fig. 94. Position for demonstration of the posterior portion of OS calcis; arrow indicates the direction of the rays. STANDARD POSITIONS 193 in the relative positions of the targ-et, plate, and part may result in some distortion which might render the plate of doubtful value in any endeavor to determine the abnormal by its comparison with the normal. While ex- perience has shown that the best results are obtained by adhering to these positions, it must be remembered that often they must be modified to meet the need of individual cases. Several illustrations of standard positions which are not shown elsewhere in the manual are here grouped to- gether. These are the only parts of the bod}^ which the x-ray manipulator should be allowed to examine. All other ex- aminations require the personal attention of the roent- genologist. DANGERS AND PROTECTION Dangers from the X-Rays. — The danger to the skin of operator and. patient requires careful consideration in order to avoid serious injury. It is customary to speak of a dose that will cause a slight temporary redness of the skin as an erythema dose. This dose undoubtedly varies considerably according to the age of the patient and to the judgment of the observer as to the extent of redness U^hich may be called ''slight." The skin dose will depend on the following factors : 1. Tar get-skin distanc e. Spark gap (voltag e). Current through the t ube. T ime or duration of exposure. Nature _ and thicknes s o f filter use d. While complete agreement as to what will give an ery- thema dose can hardly be expected, all will agree that the dose will increase with the duration of exposure, with the current and with the spark gap ; and will decrease as dis- tance between target and skin is increased and as thicker filters are used. It is convenient in this connection to combine the tube current in ma. and the time in minutes, and speak of milliampere minutes, but it must he clearly understood that the nuniber of milliampere minutes allowable varies with the spark gap. Working at a target-skin distan ce of 20 inch es and a 5-inch gap, 45 milliampere minutes may be safely allowed DANGERS AND PROTECTION 195 if n o filter is "used. For general saf ety^a filter of 1 mm. -f *'*'^* ^ of aluminum is advised, and the^_an_inerease_of ab out 40 ^ ^^^ £er cent may be allowed — or about 60 ma. minutes m ay be taken as a safe total to be received by the skin at this gap and target-skin distance. Thus, at 5 ma. — 5-inch gap — 20 inches — 1 mm. al., a total of twelve minutes may be used on one skin area for fluoroscopic examination, if no radiograph is to he taken. If 20 ma. minutes at a 5-inch gap were used in fluoro- scopy there remains only 40 ma. minutes for radiographic work. If 40 ma. is used and 10 seconds is required for a negative, only 6 plates could be safely made. On this account it is wise to make fluoroscopic examinations as brief as is consistent with good work and to use intensify- ing screens in serial radiography. A very im po rtant point t o remember is th at when using a smaller gap, alt hough th e a mount of radiatio n reaching the skin is less for the same current, the ex posure re quired in radiographic work is v ery much longer. To get the "same plate density at lower gaps, the skin risk is greater. Many cases of dermatitis ar e due to prolonged or re- p eateH exposure with too small a back-up gap for the work in hand. Be sure that unfiltered rays along t he axis of the tub e, w hich do n ot TTaveto pass through the lead glass bowl, do not^each the patient. When an erythema dose is reached orapproached^_an interval of three weeks should elapse before again expos- ing! Exposure beyond an erythema dose may be justified when circumstances arise of an unusual nature. But the surgeon or attending physician should be warned by the roentgenologist before such a risk is to be taken. Protection of the Operator from the X-Rays. — The ele- 196 U. S. AR:\IY X-RAY IMANUAL ment of increase in the work time makes care in the protec- tion of the operator of extreme importance. Two things are clear in this matter : First, that effects are cumulative ; second, that evidence of injury may develop late. Since the demands of the art fix the amount of radiation for specific purposes, the operator can do only three things for self- protection. 1. Increase the distance f rom the target to a ny part of his body. 2. I nterpo se ab sorbing material between hi mself and the tu be. 3. Reduc e the t ime devoted to the w ork. The first of these is applicable in radiographic work only, as in fluoroscopy he must work at close range. The third can have only limited application in a military hos- pital during war, so the second is the practical method. The following suggestions are offered in the hope that they may be applied : 1. That in all Radi ographic a nd treatment work no direct rays be allowed to reach the operator's body without passing through at least 1/ 16 inch of le ad where lead ca n be used. Lead__ ^ass shou ld have an absorption equivalent to 1/32 inch of lead. ^ 2. That in addition to this lead protection, the opera- tor keep several feet from the tube in treatment and heavy radiography. 3. That in using either a vertical or a horizontal flu- oroscope, a careful test be made to ensure that no direct rays come through bad joints, holes in lead, or other un- protected openings. 4. That the fluoroscopic screen be protected with lead glass at least equivalent to 1/32 inch of lead. 5. That the lead glass and sheet lead on the frame over- lap at least % inch. DANGERS AND PROTECTION 197 6. That the diaphragm never be opened or moved so as to send part of the beam past the screen, and 1 nun. of aluminum be used as a filter in all cases. 7. That in horizontal fluoroscopy some protection be given for rays scattered at right angles to the patient's body. 8. That the operator study his working conditions so as to secure the results required in the minimum time. Under no circumstances should an operator use any part of his body for fluoroscopic demonstration, nor should he hold any plate or dental film in position during exposure. It should be understood that the final responsibility for protection, both of the patient and the operator, rests on the roentgenologist himself, and after his apparatus is installed he should not neglect to test for gross leaks and insufficient protection. The fluoroscopic screen in a well-darkened room will help to find where danger may lurk but gives no idea of the amount of radiation involved in the indicated direc- tions. According to the work of Pfahler and others, on a 5-inch gap the number of milliampere-minutes required with un- filtered radiation for a full erythema dose at 20 inches, allowing no factor of safety, will be about 60. This means that without filter, 5 ma., at a 5-inch gap, 20 inches tar- get-skin distance, 12 minutes will almost certainly give a skin inflammation. A test of the danger may be made as follows : take a few dental films, number them, and place in the position occu- pied by the operator's body when at work, but attached to his clothing. After he has worked for some time, de- velop these films and note their general density. Then using the above data, 5 ma. at 20-inch target-plate distance and a 5-inch gap, expose a series of films for defi- 198 U. S. ARMY X-RAY ]\IANUAL nite fractions of the time required for an erythema dose. These fractions must be small and care must be taken to develop these films exactly as the test films were devel- oped. In this way it is possible to determine the time the operator must work to approximate an erythema dose. Probably % such a dose per month would not have any serious effect. Electrical Dangers. — In the use of high-power x-ray ap- paratus, care must be taken to avoid discharge from high tension lines to earth through the body of either patient or operator. Fatal results may follow, and in any event the nervous shock to the patient may be serious. Danger arises from sparks followed by an arc discharge from the high voltage line to the body, thence to earth. To get such a discharge, we must have : 1. Grounding of patient or contact with badly insu- lated grounding material. 2. So short an air distance from some part of the high tension system as will allow a break over spark. A single spark, while disconcerting, is not dangerous to life, but it serves to pave the way for a heavy discharge from the line if the supply is maintained. On static ma- chines and most induction coils, body connection so re- duces the line voltage as to preclude any fatal amount of current ; but with the modern high power transformer it is a difif^erent matter. The danger of an initial spark-over to the body is solely a matter of line to skin distance and voltage from line to earth. When a tube is taking current, the voltage from either line to earth is less than it would be on the same control setting if no current were passing. Hence, failure of the tube to take current at any time tends to cause discharge to the patient. The following are the com- mon ways in which this may happen : DANGERS AND PROTECTION 199 1. Failure to complete high tension connection. 2. ''Cranky" gas-tube. 3. Failure to light Coolidge filament before turning on high tension. 4. Break or disconnection of Coolidge filament circuit while running. 5. Attempting to pass current through Coolidge tube in wrong direction. Another cause for spark-over is the high tension surge often caused on closing the primary switch of the trans- former. Keep all high tension lines at least twice as far from any portion of the patient as the working spark gap. Thus, if using an equivalent gap of 6 inches, allow no wire closer than 12 inches. A grounded metal or con- ducting screen heticeen the high tension lines and the pa- tient is complete protection for the patient ; thus, a hori- zontal fiuoroscope with a grounded frame is safe with the tube below; but when the patient is between the high tension line and a grounded metal or conducting table, danger is greatly increased. Type of Control. — Much has been said of the relative danger with various controls. Simply stated it amounts to this : the rise in voltage when the tube fails to take current is very much greater on a resistance control (See Figs. 19 and 20), so that the chance of an initial spark is greater; but after such a spark, the chance of a fol- lowing arc is reduced by reason of resistance in the pri- mary circuit. With autotransformer control, or operation without re- sistance — i. e., with rheostat all out — the rise in voltage on open circuit is less; but if an arc is started, it is very dangerous. A quick-acting, over-load primary break is very desirable. 200 U. S. ARMY X-RAY MANUAL Resuscitation from Electric Shock or Asphyxiation. — The prone pressure method of artificial respiration, de- vised by Prof. Schaefer, of Edinburgh, has been advocated as the most effective method by the United States Bureau of Mines' Committee. This method can be used with oxygen inhalator. It should always be used immediately to resuscitate asphyxiated persons and kept up continu- ously until approved mechanical resuscitating devices are Fig. 95. Eesuscitation from electric shock. Above — Expiration, pressure on. Below — Inspiration, pressure off. brought to the scene and adjusted on the patient. Heart stimulant should be given as frequently as necessary. This system can be used in cases of electric shock, after the victim has been removed from the live conductor, in cases of gas poisoning or asphyxiation from any cause. Artificial respiration should he hegun promptly, as life persists only a few minutes after hreatliing stops. Quickly feel with your finger in the victim's mouth and throat and remove any foreign body (tobacco, false teeth, etc.), then begin artificial respiration at once. Do not stop to loosen patient's clothing; every moment is precious. DANGERS AND PROTECTION 201 Lay the subject on his belly, with arms extended as straight forward as possible, and with face to one side, so that the nose and mouth are free for breathing. Draw forward the subject's tongue. Do not permit bystanders to crowd around and shut off the air. Kneel, straddling the subject's thighs and facing his head; rest the palms of your hands on the loins wdth thumbs nearly touching and with fingers spread over the lower ribs. Fig. 95. With arms held straight, swing forw^ard slowly, so that the weight of your body is gradually brought to bear upon the subject. This operation, which should take two or three seconds, must not be violent, lest internal organs be injured. The air is thus forced out of the lungs. Now immediately swing backward so as to remove the pressure, but leave your hands in place. The air thus enters the lungs. After two seconds swing forward ag'ain, repeating this operation twelve to fifteen times to a minute, a complete respiration every four or five seconds. While this is be- ing done, an assistant should loosen any tight clothing about subject's neck, chest or waist. Continue artificial respiration (if necessary) two hours or longer, without interruption, until natural breathing is restored. Even when natural breathing begins, care- fully watch that it continues. If it stops, begin artificial respiration again. Keep subject warm by applying a proper covering or artificial heat, hot water bags, etc. Do not give stimulants or liquids by mouth until sub- ject is fully conscious. FLUOROSCOPY Definition. — Fluoroscopy is the method of making studies of opaque objects by means of the x-rays and the fluorescent screen. It depends upon the fact that under the influence of the x-rays certain substances become highly fluorescent. The fluorescent screen consists primar- ily of a thin layer of this fluorescent substance spread upon cardboard. This cardboard or fluorescent screen in turn should be covered, by lead glass having an absorbing capacity equivalent to 1/32 inch of lead, and mounted in a frame. To this frame there should be attached con- venient handles, and these handles should be so arranged that the hands will be protected from stray raj^s during the examination. "When not working in a well-darkened room the screen must be covered by a hood so as to shut out other light. This hood is usually arranged in a pyramidal form. The depth of this pyramid must be at least the average focal distance for the eyes. A fluoroscope for use in a lighted room has been de- scribed by Dr. Dessane (Gallot et Cie),^ Figs. 96 and 97. A spring attached across the hinge line will hold the fluoro- scope down in its working position, or when tilted over it will be held by the same spring in position on top of the head. Apparatus. — If the apparatus is to be used solely for fluoroscopic work the exciting outfit needs to be capable ^Described by L. Ombredanne et E. Ledoux-Lebard, ''Localization et Extraction des Projectiles," Libraries de L'Academie de Medi- cine, Paris. 202 FLUOROSCOPY 203 of producing no more than 5 to 10 milliamperes with a voltage corresponding to from 3-ineh to 6-inch parallel spark gap. A coil run by a mechanical interrupter will give very satisfactory x-ray light for fluoroscopic work. The great bulk of fluoroscopic work in military hospitals will be done in the horizontal position. It will be the po- sition most desirable for the localization of foreign bodies, Fig. 96. Dessane's fluoroscope attached to the liead ready for ex- amination. the study and manipulation of fractures and of the stom- ach and intestines. An outfit for vertical fluoroscopy is also desirable in military work. Its greatest use will be in the study of cavities containing fluid, such as cavities in the lungs, ac- cumulations of fluid in the pleura or the study of opaque fluids placed in the stomach and intestines to render them opaque and visible. In this vertical position one can often obtain the upper level of fluid and make an absolute diag- nosis of a condition that, when studied in the horizontal position, would give less evidence leading to a correct diao^nosis. 204 U. S. ARMY X-RAY MANUAL Operating" Switch. — This switch should be adjusted: (1) so that the operator need not continuously stand on one leg; (2) so that it will accurately and quickly close or open the primary circuit; (3) and so that it will turn on and off the ruby light which is used for general lighting of the fluoroscopic room. (See page 177.) The Darkroom, Importance of Absolute Darkness. — Too Fig. 97. Dessane's fluoroscope elevated to the top of the head after the fliioroscopic examination has been made permitting the operator to see by ordinary light without losing the sensibility of the retina because of a ruby glass which automatically drops in front of the eyes as the fluoroscope is elevated. much emphasis cannot be laid upon the necessity of ab- solute darkness, especially if an open screen is to be used. The success in attaining absolute darkness will de- pend in great part upon the ingenuity of the operator. Black cloth or black paper is a cheap way of rendering cracks and light fissures dark. To cover windows and other openings, double black curtains running in grooves will be found the most satisfactory. Unless the room be absolutely dark the object under study will be dim in out- line and in many instances not even visible. Lack of at- FLUOROSCOPY 205 tention, therefore, to this detail may result in a prolonga- tion of the tiuoroscopic study, waste of time, injury to the patient and operator, nervous annoyance and very often absolute failure in the ultimate object of the work. If the room cannot be darkened, one must use the hooded screen or work at night. Ventilation of the Fluoroscopic Room. — See ventilation of developing room, page 125. Time Required for Sensitizing the Retina. — This will vary with the individual, and particularly with regard to the age of the individual, for the young can respond to this test more quickly than older people. In general, one should be in the dark for 10 to 15 minutes before beginning fluoroscopic study. If one begins in less time than this, there is likely to be unnecessary exposure of patient and operator, and inefficient and unsatisfactory results obtained. The Light for the Darkroom. — In general a ruby light is recommended on the theory that the retina becomes fatigued by the ruby light and is therefore more easily capable of appreciating the greenish white light of the fluorescent screen. It is most important, however, that so far as possible the dim lighting of the room should be well diffused. Conditions for Fluoroscopy. — It must be clearly recog- nized that the illumination on the fluoroscopic screen is entirely of local origin and that the relative luminosity is low. For this reason it is absolutely necessary, in order to observe the details on the screen — that is, the differ- ences in illumination — to exclude light of every kind which does not originate in the excited portion of the fluorescent material. The visihility of a shadow on the screen increases with the difference of illumination be- tween the shadow and its immediately adjacent brighter 206 U. S. ARMY X-RAY MANUAL surroundings, and decreases with the general illumina- tion of the screen. As a parallel we may mention the case of lantern slide projection, where line drawings, heavy markings, and things of great contrast and reasonable size may be projected satisfactorily in a moderately lighted room with a comparatively low power lantern. But when finer details are to be seen and more difficult gradations to be identified, it is desirable to increase to some extent the candle power of the projector and to exclude light from every source, such as windows, doors, etc., which has not passed through the optical system to produce the image. This principle is of even greater importance in fluoro- scopic work because the small crystals excited to fluo- rescence emit light in every direction and always tend to illuminate portions of the screen which may have re- ceived no x-rays, so that we get a local cross-fire of true light spreading along the screen, reducing to a great ex- tent the visibility of shadows. Screens will differ in this respect to some extent according to the size of crystals used and the smoothness of the surface. On account of this diminution of detail, owing to the nature of the screen, it becomes of increasing importance to secure as sharp shadows as possible by the use of a fine focus tube and by working at a suitable screen distance. It should again be mentioned that the degree of con- trast, irrespective of the illumination, is controlled ex- clusively, for a given target-screen distance, by the equiva- lent spark gap of the working tube. The contrast will be higher the less penetrating the radiation, and, therefore, the lower the spark gap consistent with proper illumina- tion. At a given spark gap the only effect of increasing mil- liamperage through the tube is to increase the average il- lumination on the screen, so that contrast must be con- FLUOROSCOPY 207 trolled by spark gap, and brightness alone may be in part controlled by variation of the tube current. The effect of scattering is even more disastrous in fluoroscopic work with thick patients than it is in radiographic processes. As regards the preparation of the retina for fluoroscopic work, undoubtedly the ideal is to have the roentgenologist remain in total darkness for 10 minutes before starting work, and to remain in as nearly complete darkness as is possible continuously during the period of fluoroscopic examinations. It is, however, often necessary to make a fluoroscopic examination in the ward or operating room. Of various eye screening methods which have been sug- gested, the most generally recommended is undoubtedly the bonnet fluoroscope, which will be provided for use in our operating rooms. For work in the wards there will be supplied a type of automobile goggle in which celluloid instead of glass will be used. For comparatively dark weather, or when working in the evening with artificial light, the red cel- luloid will probably be sufficient, but for ward work when there is bright sunlight it is desirable to reduce the in- tensity still further. The operator can then insert the green celluloid piece back of the red, so obtaining an intensity and quality of light reasonably well suited to the purpose. As celluloid is not breakable, and the goggles can be fitted close to the eye it seems to serve the purpose reasonably well. In working with the surgeon it is absolutely necessary that one party keeps his eyes in condition for the best fluoroscopic vision. However commendable the desire on the part of the surgeon to see for himself, he should clearly understand that his selection of surgery as a voca- tion has not modified his optical organs so that he can see without taking the same precautions in fluoroscopic work 208 U. S. ARMY X-RAY MANUAL as are prescribed for the x-ray operator. It, perhaps, ought also to be mentioned that for a person who is par- tially green blind fluoroscopy with the ordinary screens is quite impossible, and men having this visual defect ought not to attempt work in this field. Summarizing, we may say that fluoroscopy demands (1) control of both voltage and current in a tube wherever possible, (2) a fine focus tube, (3) as small a diaphragm as possible, (4) a good screen, and (5) eyes sensitive to screen light by preparation in the darkroom, or near dark- room, for a sufficient period to insure good vision. Note that one accustomed to using eye glasses for read- ing should not remove them when doing fluoroscopic work, as the necessity for elear vision is even greater than in other cases. If these conditions are attained with reasonable care, many things can be determined with the fluoroscope much more quickly than with plates, and the information se- cured will be as accurate. The x-ray operator should read carefully the chapter on protection, and must assume re- sponsibility for his own safety. LOCALIZATION General Considerations. — In order that this important work may be done expeditiously and with the desired de- gree of accuracy, it will be quite important for the roentgenologist to consider the matter from the stand- point of the greatest service for the minimum effort, and with the fullest consideration for the patient. AYhere the work is largely fluoroscopic the roentgenolo- gist must insist on having a properly darkened room and be allowed to remain therein in order to keep his eyes in proper condition for his work. It is intended that the patient should be prepared outside of this room, being placed upon the stretcher top of the x-ray table, and that the necessary examination which precedes the work of the roentgenologist should be done in daylight and all neces- sary information for his guidance transmitted to him in some convenient form. Before any patient is placed in position he should see that the apparatus is in satis- factory working condition, that the accessories necessary for the localization he intends to make are conveniently at hand, nor should he fail to train his assistants during slack periods in order that they may act promptly and ef- ficiently. After the patient is placed on the table it is desirable to bring the affected part which is to be examined some- where within the middle third of the movement of the tube box. A rapid, but nevertheless careful, survey should 20Q 210 U. S. ARMY X-RAY ]\IANUAL be made of the regions at some distance from the point of entrance and emergence of the projectile, as it is well known that projectiles often follow tortuous paths, and are at considerable distances from the point of entry, and very often split into fragments, each of which may take lodg- ment in points remote from the main path. Having located the projectile whose presence is sought, it will often be found that by use of parallax, on moving the tube slightly, one can readily determine whether the projectile is above or below certain bony landmarks, and sometimes a slight manipulation of muscle will indi- cate position with reference to important soft tissues. In the discussion of methods of localization following, an effort has been made to think out and test out in the laboratory the necessary steps, in order that no essential feature may be omitted, and that the minimum of time should be required in completion of the operation. It is not intended that such instruction should be blindly fol- lowed or that the roentgenologist should be prevented from developing a procedure which his experience proves ef- ficient or desirable, but it is hoped that the steps, as laid out, will furnish a working guide for the beginner, and may be suggestive in the hands of the more experienced roentgenologist. Care in Marking and Recording. — Inasmuch as confer- ence between the surgeon and the roentgenologist is likely to be the exception rather than the rule in military radi- ology, great care must be taken in recording observations. In addition to the written report, we must, in the case of multiple foreign bodies, identify each skin mark and the corresponding depth. This may be done in either of two ways : One may number each dot on the skin and write a depth number beside it. There is some danger in this case of confusing the depth of the projectile with the LOCALIZATION 211 localization number. The following is suggested as an alternative : Place around each skin mark an indicating symbol that also appears on the record, as indicated in Fig. 98. The numbers signify that 8 cm. below the dot in the circle there is a projectile ; 3 cm. below the dot in the square there is another ; and so forth. Reports. — Reports may be made in part on anatomical charts, if these are available. The written portions should be brief, but exact and explicit. © B ^ A h X Qcm 3cm 1-kcm ^cm 6 cm 10 cm Fig. 98. Method of distinguishing between skin marks and de- noting depth of foreign body from skin marker. They should include : 1. The designating sj^mbol and the depth, corrected for screen position. 2. The approximate position of the patient when examined. 3. Anatomical information. 4. Approximate size of projectile. 5. Condition of injured bones. For marking the skin in connection with localization operations, it has been found that the Finzi ink meets a majority of the tests better than any of the others tested. The formula of this ink is as follows: Pyrogallic acid 1.0 gm. Acetone 10.0 cc. Liquid chloride of iron 2.0 cc. Wood alcohol q.s. ad 20.0 cc. 212 U. S. ARMY X-RAY MANUAL This ink is rather thin; it can be used with a pen, but is not very satisfactory in this respect. It makes a black mark and dries in from thirty to forty-five seconds, de- pending on the amount used. It will smudge slightly during the first fifteen minutes after applying, but leaves a permanent mark. The color carries from gray to intense black according to the amount used. It is visible for forty- eight hours to a week, depending on whether it is sub- jected to rubbing in contact with solid objects or with clothing, etc. It can be seen through iodine stain and re- sists alcohol. The standard skin inker will make from ten to twenty successive marks without replenishing. With proper care as to the amount to be taken on the wick, this ink will be found to give satisfaction in use. Too much ink will cause the mark to run into the sur- rounding skin crevices, and the center of the mark will not be easily gauged. Too little ink will not make a suffi- ciently black or permanent mark. Standard Methods. — Experience in military service during the present war has served to emphasize the im- portance of rapid and reasonably accurate methods for the localization of foreign bodies. The ordinary prac- tice of roentgenology, as a rule, has little to do with this phase of the subject. In civil practice methods could be used which required a considerable amount of time, and it was usually possible to consult with the surgeon and to repeat observations to an extent quite impossible in the present emergency. The localization of small projectiles in the eye had been developed in quite a satisfactory man- ner and no distinct improvement therein has been at- tempted. During the war abroad a variety of methods and appliances have been used and the choice of method has been left largely to the individual operator, since circum- LOCALIZATION 213 stances prevented systematic attention to either mechanical equipment or special training. According to the reports received from several excellent surgeons in active service at the front, it would be desir- able, and may even be regarded as necessary, that all of the injured should have the benefit of an x-ray examina- tion; since it has been found that there are many cases where foreign bodies split off after entry, or are in such unexpected or peculiar positions that they can hardly be successfully handled without the evidence available from such an examination. In order to work on such an extensive scale it is neces- sary to consider very carefully the relation of x-ray work to surgery, and to analyze the methods which are to be employed with reference to simplicity and certainty, and to pay particular attention to the reports and information needed by the surgeon in order to facilitate his work. In this connection it may be remarked that there is a distinc- tion between the x-ray requirements in evacuation hospi- tals and base hospitals. In the former, speed is essential and simple apparatus must suffice. In the latter, a more complete equipment would be expected. It may be well to recognize that time will not permit the use of plates or films in the evacuation hospitals, and dependence must be put almost entirely upon fluoroscopic work. Consequently, all arrangements in hospitals near the front must conform to the conditions imposed by fluoroscopy. As regards the methods that have been selected, it is not claimed that they are original, and no effort has been made to get any universal or entirely new procedure. After consideration of many methods it has been deemed wise to limit selection to those that best meet certain re- quirements. Among the desirable features more or less well met by various methods we may mention : 214 U. S. ARMY X-RAY MANUAL 1. The aj)paratus required should be simple. 2. The manipulation should not require an undue amount of skill. 3. The time required should be a minimum consistent with reasonable accuracy. 4. All operations likely to lead to error must be ex- cluded. 5. The comfort of the patient should be considered. It must also be remembered that the operator is an es- sential part of the localizing apparatus. It is therefore necessary to devise methods which will relieve the operator of computation and thus reduce the chances of error, espe- cially when an enormous amount of work is to be done under trying conditions. Among the operations giving opportunity for error even in ordinarily competent hands we may note : 1. Reading of fine scales. 2. Reading any scale in bad light. 3. Making arithmetical computations, 4. Drawing diagrams. 5. Changing from bright light to read scales and back to fluoroscopic work. Attention has therefore been directed to such acces- sory devices and organization of steps as would tend to eliminate these contributing sources of error. In limiting the number of methods for which provision is made there is no intention of denying that others may be equally useful and accurate, and it is no criticism of the methods or their advocates that they have not been se- lected. It was deemed more desirable to have a few methods for which careful provision had been made and in which men could be well drilled, but it is entirely optional with the roentgenologist which method he will use in any given case. It would be impossible to provide apparatus for all LOCALIZATION 215 the methods that might have been proposed or advocated. Reference to the standard methods has been made by letters instead of by the names of those responsible for their development. This is not done with any idea of de- tracting from the credit of the authors or of indicating novelty, since no claim of priority is made or desired, but simply because descriptions vary in the literature and might be quite confusing to the reader who tries to follow directions that do not apply to our apparatus. Before discussing the various methods in detail, it may well be pointed out that refined mathematical accuracy is not generally a requisite for good service in this connec- tion. As was remarked by Lieutenant Colonel James T. Case, Senior Consultant in Roentgenology of the Ameri- can Expeditionary Forces, "This war is not being fought with bird shot, and a localization, as a rule, to i/^ cm. will be entirely satisfactory." In a few cases — such as bodies in the eye, or where a small foreign body is in a particu- larly dangerous and troublesome place — greater accuracy may be required, but it is necessary for the surgeon to keep in mind the fact that because of the incision and the introduction of retractors there may result a considerable displacement of the projectile and it is often difficult to connect its position with displaced skin marks. It may also be remarked that in the majority of cases a definite ana- tomical localization should be given by experienced and well-trained roentgenologists, which in many cases may be of greater value than a simple depth determination. AYhether or not this is well done will determine to a con- siderable extent the value of the x-ray service, and every opportunity should be given the roentgenologist to ascer- tain the landmarks used in surgery and to adapt his work to the requirements of the surgeon using his data. The various localization methods may be divided into two 216 U. S. ARMY X-RAY MANUAL distinct groups. In the first of these a mark is made upon the skin and the distance of the projectile from this mark is determined. It is generally assumed that the skin mark was made at the place of emergence of the beam which formed a shadow of the projectile and that the tube focus was adjusted vertically beneath the projectile. A vertical line drawn later through the skin point can only strike the projectile if the body of the patient is placed in the same position on the operating table as it occupied during the x-ray examination, and careful distinction must be made between a vertical line so described and a line per- pendicular to the surface of the skin at the marked point. The amount by which the surgeon may miss the projectile by failure to get a correct sight line increases materially with increased depth of the projectile and with decreased dimensions, and some idea of the size of the body sought should always be given. Much greater care will surely be needed in the localization of the smaller bodies. In the other group of methods some material guide is given to the surgeon to assist him during operation. As a rule these require more time, both on the part of the roentgenologist and of the surgeon's assistants. They are naturally better adapted to the work done in the perma- nent or base hospitals. After receiving reports from both surgeons and roent- genologists abroad, and after conference with Lieutenant Colonel James T. Case, at which appliances and methods were carefully considered, it was decided by the Surgeon General's Office to adopt and provide apparatus for the following methods: A. Two wire, double tube shift method. B. Parallax method. C. Tube shift method with mechanical triangulation. LOCALIZATION 217 D. Profondometer. E. Hirtz compass with accessory devices. F. Cannula and trochar with harpoon. It happens that the first three of these are simple depth measurements, although B may give more than one depth, whereas the last three may be used to give more or less definite guidance to the surgeon during operation. It is assumed that the majority of the work will be done with the standard x-ray table by fluoroscopic methods and with the tube below the table. The tube box is movable in two directions as in the usual trochoscope and is pro- vided with a double shutter giving a diamond-shaped open- ing with the diagonals parallel and perpendicular to the length of the table and also with an adjustable slit, under separate control, parallel to the length of the table. The tube box runs freely and may be locked in any position against both lateral and longitudinal movement, and is also provided with a simple means for fixing the amount of tube shift for a particular purpose or for measuring any shift from a fixed position. The fluoroscopic screen is carried by a ball-bearing car- riage mounted on the table rails, and provision is made for a movement parallel to the table, for rotation about a ver- tical axis and, also, for a vertical shift. Each of these movements may be prevented by a suitable, convenient lock. The fluoroscopic screens are perforated with a small hole through which a marking device may be inserted to mark the skin in the vertical ray. When this ray is spoken of it is assumed that the table will be substantially in a hori- zontal position and that a line joining the target with the center of the diaphragm will be perpendicular to the plane in which the tube may move. The opening in the screen also serves a very convenient purpose in temporarily fix- 218 U. S. ARMY X-RAY MANUAL ing in position the scales and other pieces of apparatus which it is desired to use on the fluoroscopic screen. Definitions — Central Bay. — The ray passing through the center of the limiting diaphragm, which, when the tube is fixed with reference to the diaphragm holder, will change its direc- tion with each tilt or movement of the tube and its mount- ing. Vertical Ray. — The central ray when the tube is beneath the table, and the target is so adjusted that the line joining the focal spot of the target with the center of the dia- phragm opening is vertical. Note. — There has been a good deal of discussion with reference to the correction for depth on account of the thickness of the glass over the fluoroscopic screen. As outlined in this manual, there is only one case where this correction is of any importance or even applies. In Methods A and C it should be remembered that the eye of the operator is directed at the shadow on the screen and that the distance measured on the lead glass in Methods A and C represents a length on the screen itself so that when the screen is in contact with the marked point on the skin we may, in Methods A and C, ignore the glass thick- ness. In case, by reason of curvature of the body, the hori- zontal screen cannot be brought in contact with the skin mark, it will be necessary to allow for the distance between the screen and the skin, and this may be a very decided cor- rection. The simplest way in which this may be done is undoubtedly to push the graduated marking device which is used with the perforation in the screen through to con- tact with the skin, grasp it at the surface of the screen with the thumb and foreflnger and immediately on with- drawal read and record the distance from the glass surface LOCALIZATION 219 to the skin. This would give a clei)th, not below the screen, but below the top of the lead glass. Since this glass is generally about one-half centimeter thick it will suffice to use one-half centimeter or one division less than is actually measured as a subtractive correction. In Method E, when the Hirtz compass is used fluoro- scopically, care must be taken to add to the depth meas- urement of the projectile the thickness of the lead glass, if the method of determining marker depths through the hole in the screen is used. In other words, in the Hirtz compass, the four depths must all be measured from the same plane, although this is not the plane of the arms when the compass is set up. Method A. — Probably the most generally used fluoro- scopic method is that designated in our work as Method A. This method was proposed since the beginning of the war by Professor Strohl of the French Roentgenological Serv- ice. It is extremely rapid, reasonably accurate, and, as it requires a minimum of manipulation, it is likely to be the method of preference for work in the evacuation hospitals. In this, as in the other methods here described, it is as- sumed that the standard apparatus adopted by the x-ray division of the army will be used. The apparatus supplied for the standard equipment in- cludes a substantial brass frame, carrying two wires firmly attached across two opposite corners and protected by a thin sheet of aluminum, Fig. 99. These wires move with, the tube box and, when the diamond-shaped shutter is wide open, they would cast shadows upon the fluorescent screen. These shadows, of course, move with the tube box. After bringing the shadow of the projectile to the center of the fluoroscopic screen, and marking the skin through the opening provided, the operator places in position a small celluloid scale with two sliders. He then shifts the tube 220 U. S. ARMY X-RAY MANUAL until the shadow of one of the wires carried by the box coincides with the now displaced shadow of the projectile, and adjusts one of the sliders to mark this position ; then, ■J 2- . 1 2 S 4 5 ^ 7 8 9 10 l"} 18 13 14 15 16 17 18 1920 'I 'l ' I'l' I 'ITI'I'l'iTI' I TF 21 28 23 2425 2627 888© 30 3i 32533435 56 -r-r-i-t-r i-r' ;-■!•- VT-i- FiG. 99. Apparatus for Method A consisting of cross wire holder, double slider, and special rule. shifting in the opposite direction, and leaving the first slider and the center of the device fixed, the shadow of the other wire is brought to coincidence with that of the LOCALIZATION 221 projectile, and the second slider fixed accordingly. The distance between tliese two markers is in a definite pro- portion to the distance from the fluoroscopic screen to the projectile in question, and by means of a properly designed scale the depth in centimeters and fractions of a centi- ^J ^F fi =- Screen , . CJ A \B C \Af , V-r-/ vi~7 Vt""/ r, Fo L -^D Pz Pi Fig. 100. Principle of the Method A above. Simple slider for measurement of the distance between the two images shown below diagram. meter can be read directly. In case the central point of the screen is not in contact with the skin, where a mark is made, it will be necessary to correct for the distance between the skin and the screen. This is not necessary when the point marked is actually in contact with the hori- zontal screen. 222 U. S. ARMY X-RAY IMANUAL On account of its extreme simplicity and the fact that only a single measurement has to be made, and that the target-screen distance need not be known, this method has been placed first in order of preference. The principle of method A is illustrated by Fig. 100, which shows a vertical section through the foreign body P, and the target focus Fq. B is the foot of a perpendicular from Fq on the line AC. A and C are the two metal wires rigidly attached to the tube box and equidistant from B. Let Pq be the shadow of P by the vertical ray. If we shift the target parallel to the screen and to the left, both A and C being fixed to the box, they must move with it and at a certain point F^, Cj_ and P will fall on the same line, and the shadow of C in the position Oj will coincide with that of P at Pi- Likewise, shifting the target to the right will bring A^, Fo and P into the same straight line, FJt^P^. Since F^P^ is parallel to F^C, F.P, " '' " F,A, and P,P, '' " ''AC, the triangles FqAC and PPJ'2 are similar. Consequently PJ> = depth of P below P^ = d, is in the same proportion to P1P2 as BFq is to AC. Or we may write, Depth of projectile Height of B above F^ Image shift Distance between A and C The latter ratio is constant and is fixed in the set-up on the regular army x-ray table. Hence d = image shift multiplied by a constant, k, that is d = P^P^ X k. It we read P1P2 in centimeters and multiply by k, d will be found in centimeters. The special sliding markers, described above, are shown LOCALIZATION 223 in Figs 99 and 100. The center pin drops into the hole in the lead glass and prevents slipping. To avoid multiplication a special scale is provided. The distance, P^Pz, read on this scale gives the required depth. This scale is not a centimeter scale, hut the readings give m Fig. 101. Successive appearances on fluoroscopic screen in Met- hod A. (1) Shadow of projectile with small diaphram at central point of scheen. (2) Rectangular diaphragm replaced by slit open- ing shadow of wires at right and left. (3) Tube has been shifted to the left, bringng shadow of projectile and right hand wire to coinci- dence. (4) Reversed shift of tube, bringing left wire and projectile shadow to coincidence. depth in centimeters and fractions thereof for a proper height adjustment of the tube. Fig. 101 shows screen shadows in steps of this method. In (1) is seen shadows in central ray; (2) shows open slit and shadows of wires; (3) shows coincidence of shadow and right hand wire, and (4) points for measurement. Operating Instructions for Method A — 1. Make a general survey of the region to be examined, noting the number and approximate position of the pro- 224 U. S. ARMY X-RAY MANUAL jectiles, and the condition of tlie bones as to fracture or projectile injury, dislocations, etc. 2. Bring- the shadow of the projectile which is to be lo- calized, using a small shutter opening, upon the perfora- tion in the screen, and lower the screen until it is in con- tact with the body. 3. Using- the special skin marker, mark the skin carefully throug-h the perforation, and observe whether the skin point is in contact with or at some distance from the un- der side of the screen. If the latter, immediately note the correction needed. 4. Open the diamond-shaped shutter fully, and close the slit to a convenient width. 5. Insert the pin of the small celluloid double sHder in the perforation in the screen, the screen to be locked against all movement. Shift the tube to the right or left, watching the shadows of the cross wire, which is initially seen at the extreme edge of the slit opening, until these shadows become coincident. Leave the tube at rest, and adjust the inner edge of the slider to coincidence with the shadow. Reverse the shift of the tube, and do the same for the second slider. 6. Remove the slider attachment, and, by means of the special boxwood scale provided, read the distance between the inner edges of the two sliders, and record this reading as depth in centimeters. 7. Identify this skin mark, provided more than one lo- calization is to be made, and immediately enter everything on the record. Method B. — This method utilizes the optical principle of parallax and may be carried out with extremely simple apparatus, although a more elaborate device has been provided. If one observes the shadow of a projectile upon LOCALIZATION 225 the fluoroscopic screen, while the tube is movinf? and the projectile is ver}^ close to the screen, the shadow movement for a given tube shift will be very slight and the farther the body is removed from the screen the greater will be the extent of the shadow motion. If we adjust a suitable opaque body outside of the patient until its shadow moves the same distance for a definite tube shift as was moved by the shadow of the projectile for the same tube dis- placement, the auxiliary body must then be as far from the screen as the projectile whose depth is sought. In the case of a projectile in the abdomen, so far from the lateral boundary of the body as to preclude simul- taneous observation of the indicator shad- ow and that of the projectile, the a d- justment of the latter may be made after the patient has been Fig. 102. Ruled celluloid sheet to in- . dicate equality of displacement of two removed, provided shado^vs in Method B. the screen has been locked against vertical motion so as to remain at the same distance from the target as before. Generally, however, the indicator may be moved up and down in a plane, passing through the projectile and perpendicular to the axis of the body, close enough to the patient to permit free motion and allow both shadows to be seen at once. By means of parallel lines ruled on a transparent piece of celluloid. Fig. 102, it is fairly easy to ascertain when equality of motion of the two shadows is secured. In the more complete apparatus furnished for this work, Fig. 103, it is possible to mark the skin at the entrance and emergence point of the vertical ray and also along a con- tinuation of the rod carrying the special indicator. This 226 U. S. AR]\IY X-RAY IMANUAL really gives three independent depths with some corre- sponding: advantage to the snrgeon. The principle of this method is shown in Fig. lO-i, where FqFq represents the vertical ray, P '^ *' foreign body, B '' "an auxiliary body opaque to the rays and adjustable at will. The shadows of P and B are shown as though they were EiG. 1U3. Schematic drawing of parallax localizer. in the plane of the paper, but this is not the actual case, as B will be quite outside this plane. If, now, the target is moved toward the left to P^, the shadows appear at P' and B' , and P^B' is greater than PqP^ if B is farther from the screen than P. By raising or lowering B a position may be found where, on shifting the tube, the shadow of B and P move at the same rate. Then B and P are the same distance below the screen. The ruled sheet of celluloid, Fig. 102, is a convenience in making sure that P and B move the same amount when a convenient tube shift is made LOCALIZATION 227 Apparatus. — The apparatus may consist essentially of the following- parts: Fig. 103. A base of suitable size carries a vertical post, V. Sliding on this post are two rods at right angles to it that may be adjusted vertically at will. The upper of these is not ad- mz Scr-een m'P / // / / / / / / / / / / / =^ / / / / / / Fig. 104. Principle of parallax metliod. Auxiliary body, B, be- low P and distal from the screen shows greater shadow displacement to B, justable laterally, so tbat the ring, "R, is at a fixed distance from the upright, T. The other rod carries a ball, B. This may be perforated to permit of a projecting skin marker. B may be shifted in two directions at will. "When adjusted so that its shadow moves at the same rate as that of P, when the tube is shifted, the distance be- 228 U. S. ARMY X-RAY MANUAL tween the rods, d, is the depth of P below the ring, E. This is true independently of the screen position. By using three scales, D, H, and V, we may find the dis- tance from the skin to P in three directions, viz., PR, PB and PC. In all cases d and h should be observed and B Fig. 105. Apparatus for Metliod B. and B marked. If the opening in the base, C, is used in centering, BC and PB are at 90°. The parallax method may be utilized with either im- provised apparatus or with the more complete instrument. In using the latter the operator must bear in mind the fact that the accuracy of this instrument will depend to a considerable extent upon the care with which it is used. For example, if either of the horizontal projecting arms becomes bent the readings will be in error, as it is as- LOCALIZATION 229 sumed that they are strictly parallel and that both are perpendicular to the vertical support rod. The equipment supplied for use in Method B is shown in Fig. 105. Operation of Method B — 1. Make a general survey as previously directed. 2. Place the parallax instrument in position so that the vertical ray through the projectile falls on the center of the ring. This ring is to be concentric with the one around the opening in the base of the instrument. Have B drawn back out of the way when placing the instrument. 3. Lower the ring to contact with the skin and bring the screen down as low as the part examined will permit. 4. Move rod B forward as near the skin as free vertical motion will allow, and so place the fluoroscopic screen, if possible, as to allow the shadow of P and that of the end of B to show on the screen. 5. Place the piece of celluloid, ruled with lines three centimeters apart, so that one of these lines passes through the shadows of both P and B. 6. Shift the tube until the shadow of P falls on another of the ruled lines, clamp the tube in position, and then alter the height of B until its shadow falls on the same line as that of P. Do not try to follow the motion of both shadows at once. 7. Check your setting after clamping B in position by shifting the tube back, and see whether both shadows fall on the same ruled line as before. 8. Push B forward to contact with the skin, and mark by the projecting marker passing through B. 9. Carefully remove the instrument, being sure that both horizontal rods are clamped in position, and read the three scales indicating two vertical depths and one hori- zontal. Record these with the same additional data as in Method A. 230 U. S. ARIMY X-RAY INIANUAL In using the parallax instrument as described, the depth indicated is from the ring R, which always must be brouglit down to the skin quite irrespective of the position of the fluoroscopic screen. Simpler Method of Operation. — In many cases one may utilize a simple substitution method as follows: Having the shadow in the vertical ray and having marked the skin, shift the tube until the shadow of P has moved a convenient distance on the screen. Lock the tube box in position and register the new shadow position with the edge of a small piece of lead laid on the screen. Lock the screen against vertical motion and to the rail. It can then be swung to one side, the patient moved out of the range of the vertical ray, and the screen swung back to its former position, as determined by use of a small shut- ter opening. The shutter may then be opened, the marker passed through the perforation in the screen, and adjusted so that the shadow of its lower end reaches the previously placed marker on the screen. Its projection below the screen is the depth sought. In using the method of parallax it may be inconvenient or impossible to get a good view of the shadow of the pro- jectile and of the adjustable body at the same time. It should be remembered that if the shift of the image has been measured, as in the method just described, the patient may be removed without vertical displacement of the screen, and the auxiliary body as B may be adjusted to give the displacement of shadow for the same tube shift, but, in this case, the depth in a horizontal direction can- not be determined. Method 0. — The single tube shift method with triangu- lation has appeared in a great variety of forms. Some of these involve the drawing of diagrams and the use of algebraic computation. In many cases the apparatus was LOCALIZATION 231 desiofiiod to work at a fixed tube-screen distance, which has certain disadvantages. The principle of the method is shown in Fig. 106. Let F^y be the target in such a position that the vertical ray at right angles to the plane of the tube movement P P Fig. 106. Principle of single tube shift method. projects the shadow of the foreign body, P, on the hole in the screen. Shifting the tube to F^^, there will result an image shift to Pi, and the triangles PqP^P and F^F^P are similar. Also F^QP-^ is similar to each. Therefore P^Q PP. -or PPo = PoPx X P^Q P,P, - -^ — -^^- " F,Q i. e., depth of foreign body = image shift x target-screen distance divided by sum of tube shift and image shift. Where no auxiliary apparatus is supplied, one must 232 U. S. ARMY X-RAY IMANUAL B Fig. 107. Wall meter or indicator for tube shift method, also showing method of using adjustable double slider caliper. LOCALIZATION 233 measure the various lengths by a scale and make a numeri- cal computation. This may be made easier by the use of special devices. 1. A fixed tube shift of 10 or 15 cm. may be used or an image shift of an exact number of centimeters. 2. A fixed target-screen distance may be used. This is not, however, alwaj-s convenient. 3. The exact set-up of Fig. 106 may be reproduced by use of a device shown in Fig. 107, which may be supplied in case of a desire to use this method. This device consists of two straight bars, A and B, at right angles to each other. B carries an adjustable slider, R. A carries two sliders, E and G. E is not moved after one adjustment unless a new table is used. The slider, G, has notches, 1, 2, etc., 1 cm. apart, and a slider, P^, wdth a latch engaging these notches. A scale, >8^, with its zero point at the upper end is carried by G. A lug at II is in line with the zero of G. If, now, DR = tube shift, GH = target-screen distance, P-^O = image shift, then a straight line, P^D, will cross the scale, >S^, at the depth of the foreign body below the screen. The instru- ment should be fastened to the wall in a convenient place and the measurements needed should be made by a caliper, thus avoiding any reading of scales except the final depth. If in the particular case illustrated, the image shift is 4 cm. and the zero point of scale, S, is set above H an amount equal to the target-screen distance, and DH is the tube shift for an image shift of 4 cm., a string drawn as indicated will cross the scale at a point P. The scale read- ing at this point is the depth sought. "When using the standard table the slider, E, is ad- justed so that a length measured on the screen-carrier 234 U. S. ARMY X-RAY MANUAL support will show how much above E we must place G in order that GH may represent the target-screen distance. It will be observed that this instrument serves to repro- duce tube and image positions as actually observed by the roentgenologist ; i. e., one vertical ray in which the skin is marked, and one oblique ray whose intersection with the former corresponds to the distance of the projectile from the screen. An accessory device is also supplied, consisting of a strip of celluloid with a pin centering in the perforation of the screen, and having centimeter divisions clearly marked both ways from the center; making it quite easy to secure an exact number of centimeters displacement. There is a considerable advantage in making the distance the image is shifted a definite number of centimeters, and measuring the tube shift, since the relative error in meas- uring the small length of image shift is greater than that in measuring the long tube shift. "When supplied with the accessories indicated above, this method becomes as expeditious as others, and is as accu- rate as any of the depth methods. In the single tube shift method there are various pro- cedures which may be used. They all require essentially the same data, namely, (1) tube shift, (2) image shift, (3) target-screen distance. If these distances are measured to scale in centimeters, it is possible to compute the end re- sult. The apparatus supplied for this method includes a scale whereby a definite image shift may be made, if that is de- sired by the operator. There is also a provision for a definite tube shift of either 10 or 15 cm. on the standard table and for the measurement of any tube shift, if the operator desires to make the shift of the image a definite amount — the procedure generally advised. LOCALIZATION 235 Fig. 108. Apparatus for Metliod C. 236 U. S. ARMY X-RAY MANUAL The complete equipment, including the reproducing de- vice or wall meter and accessories, is shown in Fig. 108. Specific Instructions for Method C — 1. Proceed as in other cases with regard to bringing the shadow in the vertical ray to the center of the screen or on the perforation, and mark the skin as usual. 2. Place the small celluloid centimeter scale in position on the screen, so that its length is approximately parallel to the rails of the table. Bring the ring lock, on the rail outside of the carriage, against the projecting stop on the right-hand side, while the tube is in first position. Shift the tube to the left, watching the shadow of the projectile on the scale until it has moved the largest number of full centimeters permitted by full opening of the diaphragm (a narrow slit may be used to sharpen the image), and lock the tube carriage in this position. 3. Having the slider, E, on arm A of the instrument, previously set according to instructions on page 163, place the outside of the end piece of the caliper, C, against the right angle projection on the tube carriage, and slide the inner of the two movable projectors out until it comes in contact with the fixed ring on the table. Then place the fixed projector of the caliper at the top of the tube of the screen carrier, and bring the outside movable piece up to contact with the sliding sleeve, Fig. 109. 4] Move the slider on G, Fig. 107, the number of centi- meters by which the image was shifted — as four in the fig- ure. Place the inner movable clip of the caliper against H and move the slider E on B io contact with the fixed end and lock in position. Place the fixed end of the caliper on the top of E and bring G down to contact with the outer slider. A string drawn across, as indicated in the figure, gives the depth of the projectile below the fluoroscopic screen. LOCALIZATION 237 5. In case the screen was not in contact with the skin at the point of marking, determine the correction by the usual means. Fig. 109. Use of double slider caliper in measuring target-screen distance — localization^ MetJiod C. If this instrument is used as directed it will be observed that there are no scales to read before the end result and no computations. It is essential that the position of E be determined for the apparatus used and firmly fixed. 238 U. S. ARMY X-RAY INIANUAL All of the second group of methods require somewhat different manipulation and an added amount of data which may give the surgeon rather more definite indications and assist him materially in many cases. Method D. — This method has been described by Major Joseph M. Flint in The Military Surgeon of March, 1917, and while the method is not new in principle it had not been generally used heretofore, as apparatus for its ap- plication was rarely available. It consists essentially in securing three lines of sight through the body, each of which is to pass through the projectile. The points where the rays enter and emerge in establishing these lines are plainly marked on the skin. Two pieces of flexible metal, such as a composition of tin, are hinged together in the middle and placed around the body in the plane of the skin marks and made to conform to the shape of the body. The strip is marked, showing the distance that one un- hinged end overlaps the other, and the skin marks are transferred to this metal band. Carefully removing the latter from the body, it may be laid down on a card or a sheet of paper, and by bringing the overlapping end to its original position a tracing with a pencil will show the outline of the body in the plane of examination. The skin mark positions are then transferred to the diagram and we have an approximate duplicate of the shape of the body and the locations of the external skin markings. If, on this diagram, Fig. 110, one numbers the skin marks in series, 1, 2, 3, 4, 5. and 6^ and joins 1 and 4, 2 and 5, and 3 and 6, and if the work has been strictly ac- curate, that is, if the sight lines were properly established, and if the shape of the body did not change by change of position when the band was put on, supposing the band has been properly formed and not distorted afterwards, these three lines will intersect in a point; practically they LOCALIZATIOX 239 are likely to form a small triangle, but with an excellent chance of the projectile being located in this small area. If one now identifies the cliagTam, so formed, with a cross section anatomy for the same region of the body, definite anatomical inlormation as to the position of the projec- tile and the relative position of muscles or organs likeh^ to be encountered in its removal is gained. It is also possible to use two short bands at right angles Meial Strop^ Hinge of Mehl Sfra^ Fig. 110, Principle of profondometer strip. to each other, that may be made to conform to the body at a desired point, and to mount an indicating rod for use during operation. The value of this method will depend to a considerable extent upon the care exercised in forming and handling the strip and in properly adjusting it to the cross section anatomy. It is suggested that in many cases at least one of the skin marks might well have definite relation to some anatomical landmark, so that there could be little opportu- nity for a rotation of the band with reference to the ana- tomical chart. This will be especially true of portions 240 U. S. ARMY X-RAY MANUAL where the cross section is nearly a circle. It should also be observed that the accuracy of this method increases when the three sight lines are made to differ materially in di- rection. In some cases this would be a difficult matter, as in the case of a seriously wounded patient, or one for whom change of position on the x-ray table is painful. It is advised in every case that three lines of sight be determined, marking six skin points, and for this purpose the parallax localizer furnished in the army outfit will be found very valuable, as it permits of marking the skin on the under side with the same degree of certainty as on top. It may be noted also that the method here described eliminates the necessity of using more than one distinctive skin mark, and it would do no harm, when using this method with a parallax localizer as a marking device, if at least one depth were determined as a check upon the accuracy of adjustment of the profondometer band. Those who are especially interested will find articles by Major Flint giving more details with reference to this method in The Military Surgeon of March, 1917, and the Annals of Surgery for August, 1917. Specific Instructions for Method D. — It would be rather difficult to give definite directions for the use of the profondometer, because no explicit measurements are made by the roentgenologist. It will, perhaps, suffice to point out wherein difficulties or inaccuracies are likely to result. 1. It should be mentioned that the six points represent- ing the entrance and emergence points of the x-ray beams used, should, if possible, be well spaced round the body; in other words the angles between the diametral lines should be as large as possible. 2. Great care must be taken in the matter of forming the metallic strip to fit the body in the plane of the skin marks and to insure that it is removed without distortion. If time LOCALIZATION 241 permits it ini<2:lit be wise to check by a second attempt. 3. Care should be taken to properly orient the diagram secured in this way with the cross section anatomy chart and, to facilitate this, it might be well to identify one of the skin points with reference to the immediately under- lying anatomy. Method E. — There have been devised both before and during the war a very considerable number of mechanical indicators or compasses to be used during the operation as a surgical guide to better utilize information acquired by the x-ra}^ examination. Of these, the one devised by Dr. Hirtz of the French Roentgenological Service has been most generalh' approved by roentgenologists and surgeons. As originally proposed, this instrument was intended to be used in connection with radiographic work, whereby a permanent record could be made for the later setting of the compass, provided the identifying skin marks were not obliterated. On account of the very considerable time necessary to prepare a negative for examination and meas- urement, it has been found desirable in many cases to operate the compass by data secured from fluoroscopic ex- amination, which is much more expeditious and, in many cases, will serve fully as well. The essential feature of the Hirtz compass is the pos- sibility of adjustment of the movable legs that support the instrument, so that when resting on fixed marks on the body of the patient the foreign body will be at the center of a sphere, a meridian arc of which is carried by the com- pass. This arc is capable of adjustment in any position about a central axis. An indicating rod passes through a slider attached to the movable arc in such a way as to co- incide in all positions with a radius of the sphere, and whether it actually reaches the center or not it is always directed toward that point. If its movement to the center 242 U. S. AR.AIY X-RAY :\rAXrAL of the sphere is obstructed by tlie body of the patient, the amount it lacks of reaching the center will be tlie depth of the projectile in the direction indicated by the pointer. The value of the compass lies in its wide possibility as a surgical guide, in that it does not confine the attention Fig. 111. Hirtz compass. of the surgeon to a single point marked on the skin, with a possible uncertainty as to the direction in which he should proceed in order to reach the projectile, but gives him a wide latitude of approach and explicit information as to depth in a direction of his own selection. The compass is shown in Fig. Ill and schematically in Fig. 112. Three metal arms respectively labeled 1, 2, and 3 in clockwise rotation are so mounted as to turn freely LOCALIZATION 243 upon a central pivot and have their upper surfaces all in a single plane. Each of these arms carries a slider, whicli may be adjusted to any position along tlie length of the arm. Each slider has an adjustable leg at right angles to the plane of the arms, that may be held in any position by a small thumb screw. These legs are graduated and the zero point is not at either end of the legs, but a few centi- meters below the upper portion, which terminates in a small knob. The center post about which the arms ro- FiG. 112. Schematic drawing of Hirtz compass with legs adjusted at zero points and resting on a plane. tate has a hole at right angles to the plane of the arms and is also shaped to carry the curved metal arc, A (Fig. 112). The hole in the slider on arc, A, carrying the indi- cating rod, can be made to coincide with the opening through the center post. ATlien the three legs are set at zero, ciuite irrespective of the position of the slider on the arms or of their angular position, and the compass stands on a plane surface, the in- dicating rod, passed through the slider on arc. A, will touch the supporting plane at the center of the sphere of which A is a meridian arc. A friction clip on the indicat- ing rod may be adjusted in contact with the slider on A, 244 U. S. ARMY X-RAY ]\rANTIAL and the distance from the lower end of this clip to the pointed end of the indicator will be the radius of the sphere of which A is an arc. Fig. 113 shows the compass with the legs shifted so that they no longer stand on the base plane, and, in fact, are at quite different heights; but the arc, A, and the arms of the compass have not heen displaced, so that the pointer still reaches the center point, P, in this plane. Fig. 114 shows the compass actually set upon the body of Fig. 113. Arms and indicator of Hirtz compass. Same position as in Fig. 112, but with legs elevated on blocks whose tops might correspond to skin markers. a patient, its legs resting on three skin marks, M, N, and Oj and with the indicating rod pointing toward the pro- jectile, but failing to reach, it because of contact with the skin of the patient at ^S'. The depth, of the projectile in this particular direction is indicated in Fig. 114 by d. If, now, the indicating rod is placed in the slider carried by the arc, A, the rod touches the skin at a different point, 8% and the distance between the friction clamp on the rod and the upper surface of the slider on the arc, A, will be the depth of the foreign body along the direction indi- cated by the dotted line. It is evident from the construe- LOCALIZATION 245 tion that the surgeon may place the arc, A, in any po- sition throughout :3()()°, and the slider at any position from the center to the extreme end of the arc, and still have the indicating rod i)oint to the foreign hody and show its depth from the point of contact with the skin. Fig. 115 shows the compass in position on the patient at operation. The exact amount which each leg of the compass must be shifted from its zero point in order to stand on the marker Fig. 114. Schematic drawing of Hirtz compass set up on skin of patient. to which it belongs and yet have the indicating rod in the proper position is easiest seen in Fig. 116, in which only a single leg of the compass is shown ; but the same will apply to each of the legs in turn. Imagine a plane, paral- lel to the plane of the three arms of the compass, to be drawn through the projectile. The leg attached at arm number one, standing on the marker, M, would, if it could pass down to this plane, intersect the plane at the point, E, and, under these circumstances, the indicator passing through the central post of the instrument would touch the skin at S, vertically above P. If the distance from the 246 U. S. AR]\IY X-RAY IMANUAL plane, from which measurements are made, to the lower plane, containing the projectile, is measured and, like- wise, the distance J/J/', it is seen that the amount by which this particular leg is raised from its zero point, where it would be set if it reached the point, E, will be the difference between the depth of the foreign body and Fig. 115. Hirtz compass in position. the depth of the marker from any plane of measurement, for example, that of the fluoroscopic screen or a photo- graphic plate. The fluoroscopic screen may be placed in any position parallel to the base plane, EP, and the differ- ence, ME, would be quite independent of the height of the plane from which all measurements are made. This may be summarized by saying that each rod is to be shifted from its zero point an amount equal to the dif- ference between the depth of the projectile below the flu- LOCALIZxVTIOX 247 oroscopic screen, or other plane of reference, and the depth of the skin mark upon which this particular leg would stand, measured from the same plane. It is absolutely essential in the use of the compass to adopt a systematic procedure, so that the arm to carry the leg is identified with the depth measurement of its own skin point. The data necessary to properly adjust the compass may now be stated by reference to Figs. 112 and 116. The indicating rod in the central position and the three legs Fig. 116. Eeason for shift of leg of compass from zero point by the amount stated. of the compass mark out, in any plane parallel to the base plane of Fig. 112, four points of definite position in the plane. Any vertical shift of the legs will still allow them to retain their position in lines passing through the points, E, F, G and P. The point G, Fig. 112, is then in a ver- tical line passing through the marker, M, and the data necessary to set the compass must give the position in a plane of these four points and, in addition to this, must give the depth from a fixed plane, parallel to the base plane, EFG, of the three markers on the skin of the patient and of the projectile within the patient's body. Whether this data is to be found by a photographic or a fluoroscopic 248 U. S. AR]\rY X-RAY MANUAL process is immaterial, as the steps in its use will be iden- tical. When a fluoroscopic method is to be used, an auxiliary device may be found of considerable aid in rapidly and accurately securing the requisite data. Such a device is > ^ l\ Fig. 117. Accessory apparatus for fluoroscopic work with Hirtz compass. (a) Auxiliary compass, pedestal support and three markers with friction clips. (b) Hirtz compass mounted with the three legs at different levels, so that a pointer reaches white spot on the base plane at the center of the sphere of which the curved arc is a part. shown at A, Fig. 117, and consists of three arms, each with a slider very similar to the original compass. In fact the latter may be used with rather less convenience, by re- moving arc. A, and allowing the indicating rod to project a short distance below the center, with the legs tempora- rily removed. The auxiliary compass has its arms num- LOCALIZATION 249 bered in tlie same way as the original Ilirtz compass and has a projecting- pin which fits the perforation in the screen. One of the arms is rigidly attached to a ring concentric with the axis of rotation about the pin, while tl:e other two are movable, but may be clamped by thumb r.uts to the ring. It is evident that placing the perfora- tion in the screen in the vertical ray passing through the projectile definitel}^ fixes the position of the center jDost. If, then, each marker in turn is brought into the vertical ray and the arm and slider adjusted so that the hole in the slider matches such a projection of each marker, the three openings in the sliders and the central pin fix the four points which it is necessary to obtain. It then remains to determine the depth of the projectile, for which one of the methods. A, B, or C should be employed and also to determine the distance from the screen to the opaque markers. When using the fluoroscopic method, the latter depth can be very readily determined by simply passing a suitable measuring rod through the perforated screen, which has been brought into the vertical ray passing througb the marker. This depth is to be recorded and accurately identified with the arm carrying the slider corresponding to that particular skin marker. In order to facilitate this measurement a set of three measuring rods with friction clips, differing slightly in shape, are pro- vided. As soon as these four depths and the four marks in the plane of the screen have been determined, the work of the roentgenologist is completed, provided he has made sure that the skin marks are plainly visible. The adjust- ment of the compass may then be carried out by an assist- ant to either the roentgenologist or the surgeon, after which the instrument can be sterilized and is ready for the sur- geon's use. 250 U. S. AR:\rY X-RAY MANUAL Fluoroscopic Method With Auxiliary Compass — 1. Find the shadow of the projectile, Pq, on the screen, and reduce the size of the diaphragm, keeping the shadow in the center of the illuminated area. 2. Adjust the screen so that the opening at the center of the screen coincides with the center of the shadow ; lock screen carriage in this position for all except vertical travel. 3. Mark the skin through the opening by use of the special marker provided. 4. Determine the depth of the projectile by either Method A or C. 5. Raise the screen and attach three metallic markers (preferably three small w^ashers) to the skin at suitable points, and mark the skin at each point selected. Choose skin points with care to ensure: a. No interference with probable incision. b. Proper stability of the compass. c. As firm foot points as possible. 6. Lower the screen near to or touching the skin, with the central hole still in the vertical ray through the pro- jectile, and insert the pin of the auxiliary compass in the hole. Be sure that the screen is locked in position. Bring arm marked 1 to point toward the operator's right and loosen thumb nuts on arms 2 and 3. 7. Shift the tube to bring the right-hand marker in the vertical ray (leaving screen locked), and adjust the slider on arm number one so that its opening coincides with the projection of the marker, Fig. 118. If washers are used the round opening is easily identified. 8. Do the same with each of the other two markers, ensuring that number (1) does not move when adjusting the others (a small clamp Avill aid in this) and lock each LOCALIZATION 251 -* ""i- -*^ Fig. 11>'. Method of using fluoroscopic adapter -n-ith Hirtz com- pass. arm. The central pin and the three sliders then give the positions for the arms and sliders of the compass. 9. Kemove the auxiliary compass and determine the 252 U. S. ARMY X-RAY MANUAL deptli of M, N, and below the upper surface of the glass on the screen. For the depths of 31, N, and use the small rods provided with friction sliders and make the measure- ment by passing the rod through the perforation in the screen, which, for this purpose, is to be brought vertically over each marker in turn. If the friction clips are then pushed down until they touch the glass and are properly adjusted as to friction, the distance from the clips to the end of the rod will indicate the depth desired. These slid- ing clips are shaped to correspond to the projecting blocks on the sliders of the auxiliary compass, and care must be taken to use them in their proper places, so that there is a complete identification of the compass slider and the depth of the marker corresponding. Form the habit of using these in a definite order, during these depth meas- urements, to minimize chances of error. If no further fluoroscopic work is to be done these depths may be deter- mined in daylight. Otherwise use the vertical ray from the tube. Setting" the Hirtz Compass — A. By Use of the Auxiliary Compass — ■ 1. Remove the arc and the indicator rod; lower the three legs until the upper (rounded) ends project one to two centimeters. 2. Lay the auxiliary compass on a flat surface with the center pin upward. Invert the Hirtz compass and place the central hole on the pin of the auxiliary. Unlock wing- nut at center of compass, thus releasing the arms ; bring arm number 1 and its slider to such a position that on loosening leg number 1, it will drop into hole of the number 1 slider of the auxiliary. Tighten set screws of slider and of leg number 1. Fig. 119. Proceed in the same manner with arms, sliders and legs numbers 2 and 3. Tighten wing- nut at center of Hirtz compass, thus locking compass arms. LOCALIZATION 253 3. If pedestal support is provided, set the lock sleeve on the vertical rod, so that, when the pedestal stands on a flat surface, and the Ilirtz compass is placed thereon, Fig. 119. letting arms and legs of Hirtz compass directly from the auxiliary compass. with the pedestal rod through the central hole of the compass, it will be supported in such a position that the legs will drop to their zero points when loosened, leaving the compass supported on the pedestal. 4. Shift each leg an amount equal to the difference be- 254 U. S. ARMY X-RAY MANUAL tween the depth of the projectile and the depth of the skm marker on which each individual leg is to stand. (Leg number 1 stands on skin marker number 1, etc.) Tighten each leg, replace compass arc and indicating rod, the latter with lock sleeve properly set, and the compass is ready for sterilization and use by the surgeon. Note. — This subtraction can conveniently be made by laying off on paper the distance from the top of the lead glass on the screen to P, then, placing auxiliary rod num- ber 1 with its sleeve indicating the skin depth for marker one, mark this distance on the line previously made, and reset the sleeve to the length remaining on the projectile depth line. It is recommended that even if the compass is to be immediately set direct from the auxiliary a record of the data necessary for setting be made and retained until after the operation. B. From the Diagram of Data — 1. The auxiliary, having been set to mark shadows on the screen, is placed on a plain sheet of paper with center pin down. Indicate with a pen the spot on the paper where the pin touches and mark it Pq (being directly over the projectile) — a small drawing board with a hole in the center, in which the pin may be inserted through the record paper, may be helpful. Indicate the locations of the holes in sliders 1, 2, and 3, thus giving their relations to Pq/ identify each by number and write opposite each the depth in centimeters to the skin below the fluoroscopic screen. The depth of Pq below screen must be similarly indicated. 2. Take the Hirtz compass with indicating rod inserted in central hole, and set point of indicating rod on Pq of diagram. Loosen wing-nut at compass center, thus releas- ing arms; bring leg number 1 to stand on mark number 1 of diagram. Proceed identically with legs numbers 2 and LOCALIZATION 255 3; then, with indicating rod and the three legs accurately on the proper points of diagram, tighten wing-nut to lock compass. Tighten all set screws. 3. Place the compass on pedestal support and proceed as indicated in paragraph 4 above. The instrument is now ready for sterilization and use by the surgeon. Care must be taken to avoid handling the compass in any manner that would displace any of the settings. In case of deferred operation, the four skin marks should be tattooed, or they must be renewed with sufficient frequency to insure their identification at time of operation. If metal washers are used, they may be A ^ c r :!ifSlsSii!i^>!^SSiSSiSiiiSSS^i)i^^ Fig. 120. Detail of holder for direct setting of Hirtz compass. sterilized and attached at the time of the operation; they serve very well to hold the compass legs on their proper skin points. Direct Setting of the Hirtz Compass. — Several devices for holding the Hirtz compass in order to make a direct adjustment of the foot points and leg heights on the pa- tient have been proposed. This method possesses two dis- tinct advantages: (1) it may be done quite expeditiously; (2) it indicates clearly to the operator how the compass is going to stand on the patient when in use. Its dis- advantages are: (1) the necessity of considerable illumi- nation in the fluoroscopic room when placing the compass ; (2) danger of movement of the patient between localiza- tion and final adjustment; (3) need for the compass both in the fluoroscopic room and in the operating room. 256 U. S. ARMY X-RAY MANUAL In order to adapt this method to the standard table, the design shown in Fig. 120 has been developed. This con- sists of a tube fitting into the socket of the screen carrier, holding a square sliding rod with an end socket taking the hub of the compass. The collar. A, on the tube has a V-shaped projection in- tended to fit a notch in the carrier socket so as to prevent rotation from a definitely determined position. The fundamental principles in this method are the align- ment of the central axis of the compass with the vertical ray through the projectile, and the bringing of the com- pass to the proper height so that the top of the slider on the arc, when in its central position, is at a distance from the projectile equal to the radius of the arc. In order to secure the former, the holder should enable us to readily make the plane of the arms level. Then, the compass should be allowed to move up or down in a vertical direction without rotation. "When the indicator is placed in the central position and the compass is properly placed on the patient, the radius mark on the pointer will be as far above the arc slider, through which the pointer is inserted, as the measured depth of the projectile along the vertical ray. While rigidly held in this position the arms and legs may be adjusted at will to support the compass in this position. Fig. 121. Care must be taken to ensure : 1. That the patient does not move between the locali- zation and the completion of the adjustment. 2. That the pointer is raised from its zero the correct distance. 3. That all parts of the compass are locked before re- moval from the body. The holder must be adjusted before it is used the first time as follows : LOCALIZATION 257 I p i lini Fig. 121. Direct setting of Hirtz compass. Compass and holder in position. 1. Remove screen-holding rod from the horizontal socket and insert holder. 2. Remove arc from the compass, insert hub in the 258 U. S. ARMY X-RAY :\rANUAL holder, and place two of the arms close together so that the line of the holder bisects the angle between them. Then lock the center arm clamp. 3. riace a small level on the two arms perpendicular to the holder rod, and rotate rod until this shows level, then clamp by socket set-screws. 4. ]\Iake a scratch mark where the ''Y" on the ring comes in contact with the socket. 5. Remove the holder and file a small notch with a triangular file to take the ''Y" on the collar. 6. Test out as to level, when the holder is replaced in the socket with the ''Y" engaging the notch. If not quite correct, loosen the set screws at the end where the square rod enters, rotate to level, and fasten firmly. The above needs to be done only once and the procedure for use is then quite simple. 1. Remove arc from the compass and insert in the holder, fastening with the thumb nut, B. 2. Set the sliding clamp on the indicator rod at the ring mark, i. e., so that the distance from the lower end of the slider to the pointed end of the indicator is the radius of the arc. 3. Insert indicator in the compass holder and raise until the distance from the top of the brass holder to the lower end of the sliding clamp is the projectile depth below the skin mark. Fasten by nut, C. 4. Raise the legs of the compass and adjust the holder until the lower end of the pointer rests on the skin mark. Lock carrier in position. 5. Place arms and feet as desired so that the latter rest on as firm skin points as possible, and clamp all parts of the compass. 6. Raise compass slightly by the vertical movement of the carrier, mark skin points for the feet, and identify them LOCALIZATION 259 Fig. 122. Centering of tube above plate holder on cassette with small cross wires, photographic method, Hirtz compass. 260 U. S. ARMY X-RAY IMANUAL clearly. This method is much more convenient than to mark the skin first and then adjust the compass to fit the marks. Fig. 123. Skin markers, plate holder and tube holder in position for photographic method, Hirtz compass. 7. Remove compass, read and record height settings of legs, then record position of foot points, and center for resetting the compass later if it should be necessary. LOCALIZATION 261 8. For use in the operating room the compass may be sterilized by a flame. Use of the Hirtz Compass with Plates. — AVhen it is de- sired to establish the data necessary for the use of the compass with photographic plates or films, it is necessary that two exposures be made from two different target posi- tions, either upon a single plate, or upon two separate plates or Alms, without movement of the patient or skin markers. The latter method is usually preferred. There is furnished for this w^ork a small, flat square of celluloid into w^hich are inserted two small steel wires form- ing a right-angled cross. The celluloid has tw^o holes punched in diagonally opposite corners, through which a tape may be passed, and this is to be tied around the tun- nel plate changer so as to fix the desired centering mark, when two plates or two films are to be used. Fig. 122 shows how^ the tube is centered, using a plumb line to secure exact position. This must be done before the patient is placed in position; and care must be taken not to disturb the adjustment. Fig. 123 shows the tube, patient, and markers in po- sition for one of these exposures. Do not forget to at- tach to the plate tunnel the marking device or to use the three metallic markers in contact with the patient's skin at points properly chosen and marked for identification. The principle of the method is shown in Fig. 124'. A small marker, X, is placed approximately at the center of the plate, if one plate is to be used, or on top of the plate changing tunnel, if two plates are to be exposed. Let CX be a perpendicular erected to the plane of the plate at the point X and extending upward a distance of 60 centime- ters. Let F^ Fo be positions of the focus in a line parallel to the plane of the plate at the level C, and assume that CFi and CF2 are each three centimeters in length. Sup- 262 U. S. ARMY X-RAY MANUAL pose that M is one of the markers on the patient's body. When an exposure is made with the target at 1\, the shadow of M will fall on tlie plate at M^ and, when an ex- posure is made from the position Fo, the corresponding shadow will be M^. Had the exposure been continuous during the motion of the target from F^ to F^, there would have been found on the plate a straight line of shad- fz C f^ <;? \ It !\ ^ / I / } vi^-^-a^f; ;^^Q.^.j^2CA7^Pl , Megatm A// Mz Fig. 124. Schematic representation of plate, cross wire marker and tube focus positions for radiographic use of Hirtz compass. Fig. 125. Construction for finding one of the foot points M. from the shadows of a corresponding marker as shown at M-^ and M^ and the shadow of the cross marker, X. ows connecting M^ and M^. If we drop perpendiculars from the two focal positions to the plane of the plate, in- tersecting it at the points F\ F\, we see that F\ F\ M^ is a plane perpendicular to the plate and passes through M^, and the trace of this plane upon the plate is F\ 31^. In the same way a plane passed through F., F\ Mo will be perpendicular to the plate and its trace will be F\ M^. It follows from geometry that the intersecting line of these two planes, MM^, will be a line passing through the point LOCALIZATION 263 31 and perpendicular to the plate. Consequently 3/o is the foot point of this marker on the plate to be used in the compass adjustment. Also the lines M^ 31^, F\ F\ and F^ F^ are parallel. Fig. 125 shows part of a developed negative upon which there appears a shadow at M^, a shadow at J/2 and a single image of the marker on the plate — a single image, since its motion is zero or nearly so. the marker being almost in contact with the plate itself. If one joins il/j and 3L^ by a straight line and then draws through the center of the cross a line parallel to 31^ 31^ and measures a three centimeter length on this line through X in each direction from the center of the cross, the points so determined will be F\ and F\ of Fig. 124. Cross connection between the ends of these lines, that is F\ 31^ and F\ 31^ then defi- nitely locates the point 31 which will be the foot point sought. The length of the line 31^ M^, will clearly decrease as 31 is placed nearer the plate, and increase as it is raised. For the definite 60 centimeter target-plate distance and 6 cen- timeter tube shift there corresponds one height 3131^ for one image shift 31^ 31 2. These relative values are shown in Table I in which all measurements are given in centi- meters or tenths of centimeters. Fig. 126 shows a full construction and necessary record derived from the photographic plate used in setting the compass. This data is used exactly as was that derived from fluoroscopic examination. It will require a considerable amount of skill and judg- ment to so place the markers on the patient's skin as to give reliable readings and at the same time furnish proper support for the compass when used at operation. Espe- cially one must insure that the shadows of all the markers fall on the photographic plate. It is also clearly undesir- 264 U. S. ARMY X-RAY MANUAL able to have the lines whose crossings are to indicate foot points for the compass setting too nearly parallel, as in that case a slight error in their location may bring a de- cidedly large shift in the position of foot points. Trans- parent celluloid scales are sometimes furnished, which assist somewhat in determining whether the shadow of the markers will fall on the plate. Operation — 1. Knowing approximately, by previous fluoroscopic or other examination, the position of the projectile whose PLftTE Fig. 126. Complete chart for setting feet of Hirtz compass. localization is sought, select a plate changer of proper size, attach the cross, and place on the table in the posi- tion in which it is to be used. 2. By means of the plumb bob furnished, adjust the tube stand so that the central position of the target shall be vertically over the metallic cross, and be sure that the distance CX, Fig. 124, is 60 cm. Adjust stops to allow the tube to move 3 cm. in each direction from the central point. 3. Place the patient on the tunnel plate changer, taking LOCALIZATION 265 care that the cross, plate changer, and tube are not dis- placed in the process. Or, if the tube holder is rotated, fix stop for its exact return. 4. ]\Iake sure that the tube is three centimeters from its center point and insert a plate. 5. Place the three skin markers in the desired position. The balls as furnished with the apparatus may be used, or small metallic markers, preferably V-shaped, may be attached to the patient's skin with small pieces of ad- hesive. 6. ]\Iake the exposure needed. 7. Remove the first plate, shift the tube and make the second exposure. Do not attempt to get the data from the plate or film until it is dry. If it is once scratched or smeared, it will be impossible later to get good meas- urement. If the exposures are to be made on a single plate, be sure not to overexpose. "WHien using two plates, the image of the cross is used to superimpose the plates and to transfer the data to the record sheet. 8. Make the record described above, locating the foot points and the center points. 9. Eead J/^ M^, A^ Ao, 0^ 0, and Fi P, in centimeters and fractions, enter these on the record under column marked spread, and enter under height the corresponding number in the table on page 266. Thus: Spread Height Shift M^ M^ 1.5 12 6.6 Pi P2— 3A 3^ Ai A, 2.1 15.5 3.1 Pi P.— Ai A^ Oi Ol 3.6 22.5 -3.9 P^ P^—O^ Oo_ Pi P2 2.7 18.6 The equipment supplied for use in Method E is shown in Fig. 127. 266 U. S. ARMY X-RAY MANUAL Table Focus Plate Distance 60 Tube Shift 6^ Spreading Height Spreading Height Spreading Height .1 1.0 1.75 13.55 3.4 21.7 .15 1.45 1.8 13.85 3.45 21.9 .2 1.95 1.85 14.15 3.5 22.1 .25 2.4 1.9 14.45 3.55 22.3 .3 2.85 1.95 14.7 3.6 22.5 .35 3.3 2.0 15.0 3.65 22.7 A 3.75 2.05 15.3 3.7 22.9 .45 4.2 2.1 15.55 3.75 23.05 ,5 4.6 2.15 15.85 3.8 23.25 .55 5.05 2.2 16.1 3.85 23.45 .6 5.45 2.25 16.35 3.9 23.65 .65 5.85 2.3 16.65 3.95 23.8 .7 6.25 2.35 16.9 4.0 24.0 .75 6.65 2.4 17.15 4.05 24.2 .8 7.05 2.45 17.4 4.1 24.35 .85 7.45 2.5 17.65 4.15 24.55 .9 7.85 2.55 17.9 4.2 24.7 .9,5 8.2 2.6 18.15 4.25 24.9 1.0 8.55 2.65 18.4 4.3 25.05 1.05 8.95 2.7 18.6 4.35 25.2 1.1 9.3 2.75 18.85 4.4 25.4 1.15 9.65 2.8 19.1 4.45 25.55 1.2 10.0 2.85 19.3 4.5 25.7 1.25 10.35 2.9 19.55 4.55 25.85 1.3 10.7 2.95 19.8 4.6 26.05 1.35 11.0 3.0 20.0 4.65 26.2 1.4 11.35 3.05 20.2 4.7 26.35 1.45 11.7 3.1 20.45 4.75 26.5 1.5 12.0 3.15 20.65 4.8 26.65 1.55 12.3 3.2 20.85 4.85 26.8 1.6 12.65 3.25 21.1 4.9 26.95 1.65 12.95 3.3 21.3 4.95 27.1 1.7 13.25 3.35 21.5 5.0 27.25 LOCALIZATION 267 Method F. — This metliod is one that has been known under various designations and attributed to a variety of authors. It may be described as the method of direct ap- proach through the skin and tissue to the foreign body, under fluoroscopic guidance ; or, according to the apparatus used, as the method of caniuda and trochar. While the Fig. 127. Equipment supplied for use Trith Hirtz compass. method has been advocated by some excellent surgeons and has naturally given good results in many cases, it is re- garded by the Service as the least desirable of the methods adopted and it is urgently advised that it should never be used excepting in the hands of an operator who will either work under the direct supervision of a competent surgeon or anatomist, or who has acquired that degree of anatomi- 268 U. S. ARMY X-RAY MANUAL cal knoAvledge and surgical judo-ment which would permit of its use without danger to the patient. The illustrations in various publications showing the in- ;J Fig, 128. Apparatus for Method F. troduction of the instruments at an angle with the line of sight should be completely forgotten, as this method is bound to result in a considerable mutilation of the tissue before one is likely to come in contact with the projectile. LOCALIZATION 269 Pig. 129. Use of Method F with a perforated screen. In using the standard army outfit, Fig. 128. one should bring the target vertically beneath the projectile, stop down the diaphragm to a moderate size, and lock the screen against all excepting vertical motion, with the'cen- 270 U. S. ARMY X-RAY MANUAL tral perforation in the vertical ray passing through the projectile. Then insert the cannula and trochar through the perforation in the screen and, after puncturing the skin with the sharp pointed instrument, replace this by the obturator and press slowly and carefully down in a strictly vertical direction, until either contact with the projectile is felt or vision at two slight angles indicates that contact has been made, Fig. 129. After this, remove the trochar and pass the hooked piano wire or harpoon through the cannula, being sure that it passes beyond the end of the tube and that it is not withdrawn on removal of the cannula. While inserting the cannula it will best be held by use of a strong pair of forceps. These may lie flat upon the fluoroscopic screen and, in this way, the keeping of the cannula in a vertical position will be somewhat easier. The wire which has been inserted may, if one desires, be cut off a short distance, 14 inch, above the skin, or it may be bent down close to the skin and, knowing the length of the original wire, the amount projecting gives the surgeon a definite idea of depth. In the case of this method of localization but little in the way of explicit direction can be given, but it must be understood that the operator should know the line of approach with reference to possibility of bony obstruction and of dangerous proximity of vital organs, before he un- dertakes the work. Also he should invariably work with the instrument in line with the vertical ray, and not at- tempt to insert the instrument at an angle with this line. Use the sharp point only to puncture the skin and replace immediately by the obturator or blunt point, which may be inserted with far less danger of rupturing the blood ves- sels. LOCALIZATION 271 272 U. S. ARMY X-RAY ]\IANUAL Fig. 130 shows the complete set of accessories for locali- zation, as supplied and grouped according to the designat- ing letters. Fluoroscopic Assistance During Operation. — Several methods have been proposed for the utilization of the fluor- oscope at the time of operation, especially where the mobility of the projectile in the tissue and the uncertainty of its position are such as to delay, unduly, the work of the surgeon. The methods so far proposed may be grouped as follows under four heads: 1. The x-ray work may be done in the surgical operat- ing room, thus requiring the surgeon to operate in special light, which mny be extinguished when he desires to exam- ine fluoroscopically. 2. The patient may be returned to the x-ray room when the surgeon requires further information. 3. The roentgenologist may be called to the operating room for temporary assistance in pointing out the position of the projectile. 4. The operation may be performed with special forceps while using the fluoroscopic light as a guide. Each of these propositions has its own difficulties and merits. The objections to the first are the bad fluoroscopic conditions which would be likely to prevail and the fact that the x-ray apparatus would be operated at low efficiency, being necessarily delayed by the surgical operation. In the second, the transfer of the patient back to the x-ray room, provided a suitable stretcher top is used, may, of course, be accomplished, but it involves moving the pa- tient back again for operation and the possible displace- ment of parts during the transfer. The objection usually raised to number three is the re- quirement of x-ray apparatus in the operating room and the possible danger from sparks igniting an ether-air mix- LOCALIZATION 273 Fig. 131. Intermittent control. Eoentgenologist with flu- oroseope raised ready to lower it and proceed with examination. Fig. 132. Intermittent control. Surgeon and roentgenologist "working simultaneously. 274 U. S. ARMY X-RAY IMANUAL ture. The latter can be avoided eitlier by making the x-ray apparatus spark proof or by avoiding tliese fumes from the anesthetic in tlie room. The roentgenologist must be supplied with a bonnet fluoroscope which auto- matically screens the eyes by suitably colored glasses when he seeks to find his way about a lighted room, and is auto- matically lifted or removed, when the fluoroscope comes into position. In this case the process can perhaps be illustrated best by Figs. 131 and 132, showing also the type of indicator used by the roentgenologist and the surgeon. It is under- stood that the roentgenologist working above the sterile sheet can give an approximate indication, after which the surgeon, using a sterile pointer below the sheet, may, under fluoroscopic guidance by the roentgenologist, insert his indicator until contact is attained, after which the op- eration may proceed as before. The fourth method is essentially one for the expert and will probably be of more value when a practical stereoflu- oroscope is provided. The following extract from the report of the Senior Con- sultant in Roentgenology of the American Expeditionary Forces in France indicates the preparation which will be made for this class of work. "The ordinary base hospital or portable table regularly furnished by the X-Ray Division of the Surgeon General's Department of the Army will serve admirably for this type of surgery, either operating with the bonnet fluoro- scope in the usual bright light of the operating room, or by artificial light of suitable color in the fluoroscopic room of the x-ray department, with proper arrangements for con- veniently extinguishing the artificial light and turning on the current going to the x-ray tube. An order has been placed for a hundred extra base hospital tables without the LOCALIZATION 275 screen support, to be issued to operating rooms for this very purpose, our anticipation being that the bonnet method will be far more popular than the open screen method. We have acquired in France a small supply of collapsible operating tables with aluminum tops, also designed for this special type of radio-surgical work. Lacking any of these tables, the roentgenologist will be able to improvise a suitable equipment by combining the bedside outfit with an ordinary stretcher, resting on the regular stretcher sup- ports wdiich will be available in the field. "It is anticipated that the usual arrangement will be a base hospital table (without screen support) with over- head wire connections from the neighboring x-ray room, or there may be provided a special bedside unit without a tube stand with the tube under the table. ' ' For operations in the usual light of the operating room, there will be needed a bonnet fluoroscope, so arranged that when the roentgenologist is not actually working with the x-ray his accommodation will be preserved by means of dark glasses, automatically dropped before his eyes when the hood of the bonnet fluoroscope is turned up ; a special metal pointer (mdicateur) for the roentgenologist, one for the surgeon; and a forceps for projectile extraction of spe- cial design to protect the hands of the surgeon from the x-rays. A foot switch will be a help, but, in the absence of one, an assistant can turn the current on or off at will. Both hands of the roentgenologist must be free, so that he may be able to work." The following paragraph and table are taken from an ar- ticle by J. Metcalf and Keys-Wells in the Lancet of May 27, 1916. Depth of Anatomical Landmarks Beneath the Skin. — Surgeons will find the table given below of value in de- termining the exact position of a foreign body in relation 276 U. S. ARMY X-RAY MANUAL to points on the skeleton. In their article published in con- nection with this table, the authors state that the surgeon often experiences many difficulties when operating for the removal of a foreign body even after the roentgenologist has made an accurate localization. Previous to the war, the surgeon studied the ultimate depth of his operation only with regard to certain surrounding anatomical land- marks, and not in terms of centimeters or inches beneath a point on the skin. If the roentgenologist reports a projectile as being 4.5 cm. from a point on the skin of the back overlying the transverse process of the 12th dorsal vertebra, the surgeon has little knowledge as to where this depth will lead him. If, however, the surgeon knows that the average depth of this structure is less than 4 cm. from the skin, he appreciates the fact that the projectile must lie in or just anterior to the transverse process. The objection is, of course, that individuals vary greatly in thickness of various parts, but the authors call attention to the fact that the soldier is selected after rigid exam- ination and, as a result, the extremely thin and extremely obese are not present. TABLE^ HEAD: LATERALLY DEPTH OF ANATOMICAL Incision POSITION Just above zygoma 2.5 cm. to sphenosquamosal suture Just below zygoma 4 cm. to sphenoidal bone To coronoid process or condyle of mandible 2 . 5 cm. NECK: ANTEROPOSTERIORLY Through center of larynx 5 cm. to body of vertebra 3 cm. to side of center of larynx 4 cm. to transverse process of cervical vertebra 3 cm. to side of center of larynx 7.5 cm. total depth of neck Through middle line of trachea just below cricoid 4 cm. to body of vertebra 3 cm. to side of center of trachea 4 cm. to transverse process of ver- tebra From center of suprasternal notch 3 cm. to posterior border of manu- brium 'Depths were given in inches in the original table, but have here been converted into centimeters. LOCALIZATION 277 NECK: LATERALLY From center of middle of neck. From center of middle of neck. From just below tip of mastoid process CHEST: SUPERIORLY From a point midway between root of neck and tip of acromion From a point midway between internal and external extremities and just behind posterior border of the clavicle DEPTH OF ANATOMICAL POSITION 4 cm. to transverse process of vertebra 6 cm. to body of vertebra 6 cm. to body of 1st cervical 5 cm. to apex of pleura, downwards 5 cm. to apex of pleura, downwards CHEST: ANTERIORLY From center of lower border of clavicle back- wards to subscapular fossa just clear of ribs From a point just over tip of coracoid to sub- scapular fossa backwards From a point 2 . 5 cm. external to sternoc4avi- cular joint just below clavicle From a point 2 . 5 cm. external to sternoclavi- cular joint just below clavicle From a point 5 cm. external to sternoclavi- cular joint just below clavicle backwards_ From a point 5 cm. external to sternoclavi- cular joint just below clavicle backwards From a point 5 cm. below center of clavicle 7.5 cm. 7.5 cm. 3 . 5 cm. to 1st rib 2 cm. to pleura 3 cm. to 1st rib 4 5 cm. to pleura 5 cm. to pleura CHEST: POSTERIORLY To supraspinous fossa To intraspinous fossa To transverse process of 7th cervical vertebra To pleura level of 7th cervical vertebra To anterior level of body of 7th cervical To transverse process of 12th dorsal vertebra To pleura level of 12th dorsal vertebra To anterior level of body of 12th dorsal vertebra 2.5 cm. 2 cm. 4 cm. 5 cm. 7.5 cm. 3 . 5 cm. 5 cm. 8.5 cm. ABDOMEN: THICKNESS OF WALL FROM FRONT 1 cm. to either side of middle line just above umbilicus 2.5 cm. 1 cm. to either side of middle line just below umbilicus 3 cm. Just internal to anterior superior spine to iliac fossa 7.5 cm. Midway between anterior superior spine and pubic crest to front of acetabulum 5 cm. ABDOMEN: THICKNESS OF WALL FROM SIDE On level of tip of 12th rib in line upwards from anterior superior spine 2 . 5 cm. ABDOMEN: THICKNESS OF WALL FROM BACK To transverse process 3d lumbar 4 . 5 cm. To anterior level of body of 3d lumbar 11 cm. To anterior level of psoas muscle 13 cm. 278 U. S. ARMY X-RAY MANUAL HIP AND THIGH FROM FRONT DEPTH OF ANATOMICAL POSITION 8 cm. below anterior superior spine to head of femur G cm. 8 cm. below anterior superior spine to neok of femur 5-7 cm. 15 cm. below anterior superior spine (level of lesser trochanter) to front of femur 4 cm. To greater trochanter 11 cm. To lesser trochanter 9 cm. Brim of pelvis 2 . 5 cm. in front of sacroiliac syn- chondrosis 9 . 5 cm. To anterior inferior spine 3 cm. To spine of ischium 12.5 To ischial tuberosity 13 cm. To anterior surface of line of junction of ascending ramus of ischium and descend- ing of pubis 7 cm. HIP AND THIGH FROM BACK To ischial tuberosity 6 cm. To spine of sacrum on level of posterior superior spines of ilia 3 cm. To sacral groove 5 cm. To head of femur 5 cm. To greater trochanter 9 cm. To lesser trochanter _ 7.5 cm. To brim of pelvis 25 cm. in front of sacroiliac synchondrosis _ 10 cm. To anterior inferior spine 15 cm. To spine of ischium 5 cm. To posterior surface of junction of ascending ramus of ischium and descending ramus of pubis 11 cm. Eye Localization. — In the case of foreign bodies in the eye very accurate localization is necessary, as knowledge of the exact position of the foreign body may mean the saving of an eye or the preservation of vision. The simple Sweet-Bowen apparatus consists of two gen- eral parts : the base or head-rest, as illustrated in Fig. 133, and the localizer, as shown in outline drawing, Fig. 134. The head-rest base is composed of the following parts : 1. A plate-slide tunnel, so constructed as to protect one-half of a 5 x 7 photographic plate while the other half is being exposed, and to protect the exposed half while the second exposure is being made. 2. Four rubber-tipped legs to raise the tunnel so that LOCALIZATION 279 it will act as a pillow to hold the patient's head level when lying on his side. 3. A plate-holder having a slide that will protect the plate from the ordinary light, but offer no resistance to the x-ray. Fig. 133. Head rest for use with the eye localizer. 4. An arm or handle attached to the plate-holding slide to enable the operator to shift the plate the correct dis- tance for each exposure, and to withdraw the same when both exposures have been made. 5. A pneumatic cushion for the comfort of the patient. 6. A double clamp to hold the patient's head and to prevent any horizontal movement. 280 IJ. S. ARIMY X-KAY IMANUAL 7. A single vertical clamp to press the head downward upon the pneumatic cushion. The localizer consists of: 1. A heavy metal base. Fig. 134. 2. An upright standard, B, to support the localizer and ^^^ ,/* JfS \ f/o B2 Fig. 134. Sweet eye localizer. permit the same to be adjusted and held firmly at any desired height. 3. The indicator-ball D with its needle-supporting stem D^, which, when properly adjusted to the center of an eye, will cast its shadow on the photographic plate and s^rve as a landmark to indicate the center of the cornea. 4. The metal tip E, of stem E"^ is made cone-shaped, so as to more easily differentiate its shadow from that of ball T>. These indicators are permanently adjusted a LOCALIZATION 281 known distance apart (15 millimeters), and the base of the localizer is provided with two holes exactly 15 millimeters from center to center, which should be employed to verify this adjustment in case of doubt. AVhen an x-ray plate is made of them obliquely, adjusted to an eye as above stated and as indicated in "front view" on the chart, we are enabled by their shadows to definitely locate the source and course of the rays of light (in relation to the chart) that caused the shadows. Also, the position of any foreign body that may show on the same plate can very easily be determined by the position of its shadow in relation to that of the ball and cone, because the exact position of the latter with reference to the chart is known and indi- cated (front view). 5. Tube C^^ and notch F'^^ are sights similar to those used on a rifle, with which the operator can accurately align the center of the cornea of the afflicted eye with ball D and its supporting step Z)-. F^^ is a spring trig- ger which presses upwards against pin F'^^. F° is the end of the rod to which the indicator-ball and cone D and E are attached by bracket F, the whole being supported by passing through tube C°. Spring F^"^ being attached to stationary tube C° by means of bracket C^ rod F^ with bracket F^ can be pressed forward until pin F^^ is engaged by notch F^^. 6. By loosening set-screw (7* the bracket C can be raised or lowered until ball D with its supporting stem D^ is in exact alignment with the center of the cornea of the af- fected eye, and the screw is then tightened. 7. The patient is instructed to close his eyes, and the entire instrument with its base is slid forward until in- dicator-ball D presses into the eyelid approximately its thickness. The trigger F^'^ is then depressed to disengage notch F-^ from pin F'^^, when spring F^*^ will cause the rod 282 U. S. ARMY X-RAY MANUAL F^ and indicator-ball D and cone E to rebound exactly ten millimeters, being restricted by knob F'' in slot C^. The subject and localizer are now in correct position for making the two necessary exposures. First Exposure. — Place patient's head, affected eye downward, on the plate-holder base, with inflated cushion in position, as shown in illustration, being careful that the inflated cushion does not extend over the marked lines on the cover — otherwise it will cast a shadow on the photo- graphic plate. If the subject shows a tendency to move about, the hori- zontal clamp, as shown in Fig. 133, must be adjusted to the base of the head and forehead, otherwise the vertical clamp, as shown in illustrations herewith, will be suffi- cient. The double horizontal clamp can be adjusted for either eye by means of its two off-center holes and clamp screws. Place the diaphragmed tube in position so that its cen- tral rays will exactly parallel the front vertical plane of the patient's eye, as shown in Fig. 135. A plate, having previously been placed in the plate-hold- er, is now placed in the tunnel with the outer flange pro- truding, as shown in illustration. This will expose one- half of the plate to the action of the rays, while the other half will be protected for the second exposure. The localizer (Fig. 134) is now placed on the stand in front of the affected eye; its trigger is "set" as already described and, after the indicator-ball has been adjusted to the plane of the cornea, the entire instrument is pushed forward on its base until the ball presses into the patient's closed eyelid approximately its thickness ; the trigger spring is then released and the indicator-ball and cone recede ex- actly 10 millimeters, thereby permitting the patient to open his eyes and wink them in a natural manner. By referring LOCALIZATION 283 to localizer chart you will observe that due allowance of 10 millimeters has been made by placin^^ the indicator- ball and cone just that far from the front plane of the Fig. 135. Position for first exposure in localization of projectiles in the eye. Be certain that the tube is centered accurately over the cone so that both ball and cone will be superimposed. cornea. It should also be borne in mind that the front of the cornea is 10 millimeters in front of the shadow of the indicator-ball, as shown in your negatives. The tube 284: U. S. ARMY X-RAY MANUAL is now centered over the localizing ball and cone so that the shadows of the two will coincide (Fig. 135). Some object, such as a candle or a piece of white paper, that can readily be seen by the patient, should be placed in alignment with the sights of the indicator, but several feet removed therefrom, and the patient should be instructed Fig. 136. Specimen plate of projectile in the eye illustrating the method of measurement. to look constantly at this object while the two exposures are being made. Second Exposure. — The first exposure having been made with the rays perpendicular to the plane of the plate and parallel to the patient's eye, thereby superimposing the shadows of the indicator-ball and cone and their sup- porting stems, as shown in the right-hand half of illustra- tion (Fig. 136) the x-ray tube is then shifted toward the patient's feet four or five inches and tilted so that the indicator-rod points to the ball of the localizer, thereby LOCALIZATION 285 causing the central rays to pass obliquely through the cen- ter of the cornea of the patient's affected eye, as shown in Fig. 137. Second exposure for localization of projectiles in the eye. Notice shift of tube in order to separate the shadows of ball and cone. Be careful not to produce any lateral shift. The tips of ball and cone must be kept in alignment. Fig. 137. The photographic plate must now be shifted by pushing the plate-holder inward, by its handle, as far as it will go, thereby protecting that portion that was acted 286 U. S. ARMY X-RAY MANUAL LOCALIZATION 287 r:3 05 CO O S 288 U. S. ARMY X-RAY MANUAL upon by the rays in the first exposure and bringing its un- exposed half in proper position to receive the rays from the second exposure. In this position the second exposure is made with the rays falling obliquely upon the indicators, thereby separating their shadows, as shown in left half of illustration. It should be remembered that it is not essential that the exposures be made with the tube at any specific dis- tance from the plate, or even that it be the same distance for the two exposures. Neither is it important that the tube be shifted an exact or known distance for the second exposure, as by the use of the charts and Dr. Sweet's method the course of the ray is automatically established. This is shown by the line A-D through P^ and P^ of out- line drawing, Fig. 138. Charting the Plates. — In charting the plates the follow- ing method is pursued: Upon the negative (right-hand half of the illustration) which represents the first exposure, a line is drawn through the horizontal axis of the indicator- ball and cone which are here superimposed, thereby pro- jecting their supporting stems and establishing the visual axis of the eye. Fig. 136. A second line is drawn at right angles to the first through the center of the foreign body's shadow. With a small pair of dividers step the distance from the edge of the indicator-ball to the intersection of the horizontal and vertical lines that you have just drawn. Then step this distance off on the diagram chart, making a dot with a pen, or a very sharp, hard pencil, to repre- sent the exact distance (distance R, Fig. 138). On the vertical line that has been drawn through the shadow of the foreign body (right-hand half of Fig. 136) measure the distance of the foreign body above or below LOCALIZATION 289 the horizontal line and indicate the same on the chart above or below the axis, distance V locating dot F^. Place another dot on the same horizontal plane and draw a line through these two dots, parallel to the axis, project- ing into the front view as shown. Since the position of localizer-ball B, as shown on the chart, side view, is the same as when the first plate was made, the location of the foreign body must be at point F^. We have yet to establish its location to the nasal or tem- poral side. Project a line vertically through point F^ to the 45 degree angle (see Fig. 139), thence horizontally through the horizontal section. Upon the negative (left-hand of illustration) which represents the second or oblique exposure, a line is drawn through the horizontal axis of both the ball and the cone, thereby projecting their supporting stems and establishing the relation of their horizontal planes to that of the foreign body. A third line is drawn at right angles to the first two through the center of the foreign body shadow. With your dividers measure the distance of the shadow of the foreign body above or below the horizontal plane of the shadow of the ball, and mark the same by a dot on the front view of the chart just above or below the center B, as indicated by distance X, because that was the relative position of the indicator ball when it cast the shadow. Measure the distance of the shadow of the foreign body above or below the horizontal plane of the shadow of the cone, and mark the same on the chart at the point above or below C indicated by distance Y because that was the relative position of the indicator cone when it cast the shadow. A line drawn through dots P^ and P^ will represent 290 U. S. AR:\IY X-RAY MANUAL the true course of the rays in the second exposure, and its intersection with the projected line from the side view through the point F^ will be the position of the foreign body when viewed from the front, while a vertical projec- tion through the horizontal section shows the position of the foreign body to the nasal or temporal side at point F. In these eye localizations a source of error is the fact that this is a schematic eye, constructed to correspond to the average eye which is about 24 millimeters in diameter, but this may vary 3 millimeters from the average. Sometimes the variation can be measured with an opthalmoscope and corrections made, but ordinarily the eye is so injured that this is impossible, and we must assume that the eye corresponds to the schematic eye. This error, of course, would interfere only in those cases where the foreign body is located 1 or 2 millimeters inside or outside the sclera. In that event one would not be certain whether the foreign body was within or without the globe of the eye. This point may often be determined in the following manner: Place the patient on his side with the afflicted side next to the plate and center the tube over the eye. Fix the vision of the good eye on a spot in a plane paral- lel to the plate, so placed that the eye is rotated toward the top of the head. Make an exposure of 1/2 the correct amount, then shift the vision to a point well toward the feet, still keeping the head fastened securely in place, and expose for the remainder of the necessary time. If there are two images of the foreign body, it is certain that the foreign body moved with the eye and therefore must be in the globe. It is barely possible for the foreign body to be in an ocular muscle and move, thereby giving two images, but NEAREST POINT METHOD OF LOCALIZATION. (Insert in Manual at Page 291) Owing to the enormous pressure of work on the roent- genologist in an advance hospital during periods of great activity on the front, it is necessary to utilize the simplest and most rapid method of localization that is consistent with working accuracy. One method, not described in the manual, that has met considerable favor in rapid approxi- mate determination of location and depth is the so-called "nearest point" method. This method consists in palpating under fluoroscopic observation the'soft tissue surrounding the projectile. .The instrument used for this palpation is a wooden rod about ten inches long with a wood screw or some similar piece of metal at the end. Under the screen the wood is almost invisible and the only plain shadow is that cast by the metal. By the movement of the projectile under pressure on the tissue surrounding it and the amount of pressure used, the operator is able to judge with fair accuracy as to what point on the skin is nearest the projectile and the depth from that point. Obviously, palpation at a very near point will ordinarily cause much greater movement of the projectile than will palpation at a more remote part of the skin surface. Likewise, palpation will cause greater displacement in the very soft tissues than it will in the more firm. Skill in this method increases with continued use, and a sense of pressure is developed that proves a valuable aid to speed and accuracy. To the beginner with this method it is recommended that he coin])iiie witli palpation the principle of Method B by shifting his tube and observing relative displacements of the projectile and the palpating stick. The nearest point method is applicable to localization of projectiles in the soft tissues of the extremities, the axilla, scrotum, and buttocks, but not to the more vital and less palpable regions of the iiead, thorax, and abdominal cavi- ties. By practice one becomes accustomed to palpating the soft tissues around the foreign body and by what are termed light and deep palpation to determine the depth of the projectile from the nearest point on the skin surface. Even if the foreign body cannot be displaced by pressure with the palpating stick this information is often of great value, showing that the projectile must be in a joint, against the bone, or embedded in deep tissue. This method is, in brief, adapted to localization in the extremities and soft parts of the body, under advance hospital conditions where rapid examination of the patients is a matter of prime importance. LOCALIZATION 291 its position near the exterior and anterior portion of the globe would help differentiate this. In an acute ease where a localizing apparatus is not available, this method may be all that is necessary. BONES AND JOINTS Fractures. — A fracture may be defined as a break in the texture of a bone or, more briefly, as a solution of con- tinuity. The study of fractures with the aid of the x-ray en- ables us to decide : first, whether a fracture is present or absent; second, the number and relation of the broken fragments, so that the best mechanical measures can be selected for replacement. After a retentive dressing has been applied, it is easy to study the results of treat- ment without waiting for the test of healing and restora- tion of function. From a radiographic standpoint fractures may be clas- sified into : first, simple fractures, where the bone is broken in two pieces; second, comminuted fractures, where the bone is broken into many pieces. Simple fractures may be further classified according to the direction of the frac- ture line : first, where the line of cleavage is transverse ; second, oblique; third, longitudinal; fourth, combinations of the preceding varieties. Naturally the comminuted fracture is more common in military service than in civil life. In military service there is to be seen frequently the effect of high-speed bullets upon bones. The difference between high-speed projectiles and small projectiles of low velocity is quite striking. In the former the results simu- late an explosive action evidenced in the marked com- minution and shattering of the osseous tissue. Small lead bullets, as a .22, usually cause only slight injury to bones, 292 BONES AND JOINTS 293 and very often the effect of the contact is seen rather in the deforming of the bullet than in the shattering of the bone. Fractures may be studied by the x-ray either by the fluoroscopic method or by the plate method. Each has its advantages and disadvantages. Fluoroscopic Method. — The advantages of the fluoro- scopic method are, primarily, its convenience and quick- ness of execution, without the delay of waiting for the development of plates. It allows of a rapid survey of the entire body. It is cheap as compared with the cost of a number of plates. Its principal disadvantage lies in the fact that it does not always show clearly the texture of bones, so that fractures of slight displacement are not readily shown. This is especially true in fleshy individuals and in parts of the body where the bones are enveloped in a good deal of soft tissue. Fractures of small bones, as transverse fractures of the scaphoid or longitudinal frac- tures of the head of the radius, may easily escape notice. Impacted fractures also of the lower end of the radius and of the surgical neck of the humerus may be seen so indistinctly on the screen that there may occur a reason- able doubt as to their presence. Plate Method. — The chief advantage of the plate method is that it affords an exact study of the cancellous tissue of the bones. It also gives a permanent record of the case, so that the condition may be observed by others. As in the examination of the gastro-intestinal tract, the greatest amount of information is often best obtained by a combination of the two methods. The determination of the part of. the body to be radio- graphed will naturally depend, first, upon the clinical history, if one can be obtained, and second, upon the usual signs of fracture on physical examination. If a patient 294 U. S. AR]\rY X-RAY IMANUAL can be examined on the fluoroscopic table, the fluoroscope will assist in deciding on the area to be radiographed. It is evident, however, that some types of subperiosteal frac- ture, for example, fractures of the lower end of the fibula, may be present without screen evidence. In radiographic examination of fractures, the adherence to a routine and established type of technique is of con- siderable advantage. One of the most essential points in this technique is the choice of a suitable ray; by this is meant a ray of penetration sufficient to properly display the internal structure of the bone. Such a ray will be given off by a tube having an equivalent spark gap of four to five inches. Next to the choice of the proper penetra- tion will be the estimation of the correct time of exposure. The next factor in the production of suitable plates is immobilization. If attention is not paid to this, the twitch- ing of the wounded muscles and the voluntary attempt on the part of the patient to keep the part quiet will result in muscular tremor which will blur the bone detail. The immobilization can be obtained most easily by weighting the parts above and below the area to be examined by suit- able sand-bags. These sand-bags should not be completely filled. They can then be packed around the limb in order to secure the greatest quiet. If sand-bags are not obtainable, the use of strips of adhesive plaster above and below the examined area will be found useful. AVide bandages passed around the part and then tied on the under surface of the table may also be used. If one is working with the tube above the table, cotton pads or an inflated rubber bag may be placed between the cone of the tube-holder and the af- fected part for compression. It is very important that plates should be labeled at the time of examination. In the hurry of darkroom technique plates are sometimes reversed, so that it is not always pos- BONES AND JOINTS 295 sible to tell at a glance whether the plate is of the right or left leg. Accordingly, with each exposure a lead letter 1\ or a lead letter L should be placed upon the plate to designate which limb is being radiographed. It is of further advantage in lateral plates, especially of the femur, to mark the anterior border with suitable lead letters, so that the relative position of the fragments can be told at a glance. The necessity of doing this arises from the fact that often- times plates are examined when the radiographer is ab- sent, and those observing the plates may not be skilled in their interpretation. AYith the careful labeling of plates serious mistakes may often be avoided. In examining fractures which w^e have reason to sus- pect are comminuted, or which may be complicated with the presence of a foreign body, the value of stereoscopic plates cannot be overestimated. These give a good idea of the true relation of the fragments, and if the foreign body is present, show its position in three planes. Location of Tube. — In considering the examination of special parts of the body, we must consider the technique from two separate standpoints. First, the examination may be conducted with the patient lying upon a table, the tube being placed above the part to be x-rayed and the plate underneath. Second, if the examiner is provided with an apparatus by which the tube is contained in a tube box underneath the table, the rays are then directed from be- low upward. Each method has certain advantages and dis- advantages. The advantage of the first position is that one can see at a glance the relation of the tube to the part to be radiographed, and he is able to make use of the central rays. The advantage of using the central rays is to minimize distortion. AYhile this distortion may have only a comparatively slight importance in plates made of simple fractures, yet in plates of comminuted frac- 296 U. S. ARMY X-RAY MANUAL tures, especially those complicated with foreign bodies, the question of distortion assumes considerable importance. A further advantage of using the tube stand is that in certain parts of the body it is advantageous to employ oblique rays. For example, in radiographing the foot, it is often necessary to employ oblique radiation in order to properly separate the shadows of the metatarsal bones. The degree of obliquity and the angle at which the rays will strike the part examined can be much more easily told by the use of a tube stand than by the use of a box under- neath the table containing the tube. Another great ad- vantage of the ordinary tube stand is that the tube can be shifted so that the rays pass laterally, permitting of lateral exposures of the ankle, knee, femur, and arm with- out disturbance of the patient. In fractures of the femur and knee with plates made at the bedside of the patient, this will oftentimes be a point of great advantage. The disadvantages of this method are, first, the necessity of raising the limb to insert the plate underneath, and, sec- ond, the necessity of protecting the plate from moist dress- ings. This objection can be easily overcome by placing the plate in an aluminum plate-holder. The advantages of working with the tube beneath the table are the fact that the plate can be supported imme- diately above the injured member and that no lifting of the limb while the patient is on the table is necessary. If the tube box below the table is used, it is necessary to have some mechanical pointer attached to the box so that one knows the axis of the central rays. In the making of stereoscopic radiograms many operators prefer the tube above the patient. Most of the types of American ap- paratus are made for radiographing the patient from above downward, while many of the types of the Continental and the English, have the tube below the table. BONES AND JOINTS 297 Position for Exposure. — The illustrations show briefly the positions in which the different parts should be radio- graphed. These positions may be adopted as a routine in the majority of cases, and there is an advantage in follow- ing a routine plan. The individual case may, however, demand a departure, in which case, a safe rule to follow is that the injured part should be as close to the plate as possible and the vertical ray should enter immediately over the center of this area. The comfort of the patient must be kept constantly in mind, and if an arm cannot be completely extended, it is possible to demonstrate lateral displacement of fragments by the anteroposterior exposure even if the elbow is flexed at a right angle. The point to remember is, that it is im- possible even with stereoscopic plates to tell accurately the amount of displacement that may be present in the region of a joint, such as an elbow or knee, if the plates have been made in one direction only. In the case of the spine the best results are obtained by raying a comparatively small area at a time with a medium sized cone. For the lateral view it is almost es- sential that one should use an intensifying screen and remove the tube to a considerable distance from the plate, at least thirty inches. Radiographs Made Through Splints or Casts. — In radio- graphing parts of the body enveloped in splints or casts, there is presented, oftentimes, a difficult problem. For purposes of exact diagnosis it is always best, w^hen possible, to remove any splints or casts. If the examination is made for determining the position after reduction, the dressing should be left on. The length of exposure is to be in- creased so as to compensate for the extra amount of mate- rial which has to be penetrated. Some splint materials, for example, yucca board, contain particles of extra den- 298 U. S. ARMY X-RAY MANUAL sity which, when superimposed on the shadows of the bone, render the detection of subperiosteal fractures difficult. It often occurs that the radiographer has to decide whether callus is present or absent in a limb enveloped in a plaster splint. It can be stated tliat this is oftentimes impossible to be decided, as the varying densities of the folds of plaster induce shadows which may simulate the appear- ance of callus. Sometimes when a limb has a splint on one side only, the rays can be directed so that the shadow of the bone can be wholly or partly isolated from the shadow of the splint. In elbows confined with a right- angle metallic splint, the metal may cast a shadow over the part especially interesting, and here in the interest of exact diagnosis it is best to secure permission to remove the splint. Dry plaster is more easily penetrated by the ray than moist plaster, so that it is always best to x-ray a limb in a plaster cast after the cast has become thor- oughly dry. The position of the fragments of long bones of course can be accurately told even when enveloped in a wet plaster cast, but it is not to be expected that fine detail and the presence or absence of callus can be made out without the removal of the cast. Where the examina- tion has to be made in only one direction the plates should be stereoscopic. Splints, casts, dressings, 'bandages, etc., should never he disturbed by the roentgenologist. If they have to be re- moved, this should be done by, or under the direction of, the surgeon. The Appearance of Callus. — Changes in the periosteal surface appear very early after injury, sometimes being seen after a period of four or five days. These periosteal changes vary in proportion to the amount of displacement. If a fracture is of the subperiosteal type, or if the frag- ments have been accurately coapted, periosteal changes BONES AND JOINTS 299 will be small, and not extend far from the seat of frac- tnre. If the fracture is transverse, with over-riding, or if it is comminuted with displacement, we may find perios- teal changes extending a number of inches away from the seat of injury. We often find, especially in the lower leg, difficulty in telling whether there has been enough repair to allow the patient to walk upon the leg.' Careful inspec- tion of the plate may show nothing but the position of the fragments, without any periosteal change. In these cases, it is difficult to tell from the radiogram alone whether union has taken place. Reports. — In waiting reports of x-ray plates for frac- tures, it is essential to describe first the area shown by the plate with the anatomic parts of the bone examined; second, to give a description of the traumatic pathology shown; third, a statement as to the condition of the bone, or bones, and of the soft parts outside of the area described in the second heading. In the report the manner in which the plate is made should be described so that this can be taken account of in considering the interpretation. For example, if a lateral plate is made, this fact should be men- tioned at the beginning of the description. A description of the traumatic pathology should embrace, first of all, the part of the bone involved; second, the type of fracture, whether transverse, oblique or longitudinal ; third, whether comminution is present and the number and size of the fragments. In all cases the relative position of the frag- ments should be described. If the fracture is complicated by the presence of a foreign body, this should be stated, with the size, shape and position, and its relative position to the bone fragments. Particular attention should 'be paid to the question as to jivhether the fracture line involves joint surfaces. Prog- 300 U. S. ARMY X-RAY MANUAL nosis and treatment are materially affected in this type of injury. If it is doubtful after an examination of all the plates whether a fracture is present or absent, this doubt should be plainly stated and the reasons for it given. If the un- certainty is based on lack of penetration or blurring due to movement, a second exposure should be made. If splints v^ere present at the time of examination, their appearance should be described and special note made as to whether the shadow of the splint complicates the interpretation. Negcative Reports. — If the examination does not reveal the ordinary x-ray evidences of fracture, this should be stated with a definite description of the area shown by the plate. For example, a negative report stating that there is present no fracture of the tibia or fibula should not be made unless the plate shows the entire length of the tibia and fibula. If the limb is rayed in only one direction, note should be made of this and the conclusion should be stated that no disturbance of the outline of the bone is shown in this one view. X-Ray Osteology. — To become proficient in the inter- pretation of plates, constant use should be made of the drawings and descriptions in standard anatomies, supple- mented, if possible, by recourse to the study of the skeleton. Epiphyses. — While in military radiography the question of the appearance of the bones during their development will not often be raised, yet it is best to remember that during the growing period, when the bones are in forma- tion, their appearance may be different from the fully formed adult type. The different standard anatomies give tables under which are described the development of the bones and the age at which the epiphyseal lines become ossified. In the young adult the appearance of the crest of the ilium should be borne in mind, as ossification here BONES AND JOINTS 301 takes place at the age of eighteen to twenty. In cases of doubt as to whether the epiphyseal line is to be differen- tiated from a fracture line, a plate made of the uninjured limb for purposes of comparison is of the utmost impor- tance. Plate Defects. — The interpreter of x-ray plates should be constantly on his guard against confusing plate defects with fracture lines. While it is unusual for such con- fusion to arise, still, scratches upon the plates have been mistaken for solutions of continuity; artefacts due to air bubbles have been confused with foreign bodies. Conclusions to Be Drawn from Plates Influencing Meth- ods of Re-position. — It can be said that some clinicians do not derive from the study of the plates all the information which the plates afford. Here the conference between the experienced roentgenologist and the clinician is of the greatest benefit to the patient. A careful study of the plate, with a full understar ^ Ing of the problems of re-position, will oftentimes obviate the question of operative interfer- ence. Setting of Fractures under the Fluoroscope. — In the reduction of fractures the aid of the fluoroscope during manipulation may be of value. Important precautions are, however, to be observed in this procedure. If the patient is under ether anesthesia, precautions should be taken against the ignition of the ether vapor by electric sparks from the high tension current. The danger of this is in direct proportion to the lack of ventilation in the operating room. If the high tension wires are covered with thick insulating material and loose connections are avoided so that there is no tendency for sparks to occur, the danger is minimized. The operator and his assistant should be protected as completely as possible against radiation. This may be 302 U. S. ARMY X-RAY IMANUAL done by the use of x-ray proof gloves, x-ray proof aprons, suitable lead glass over the fluoroscopic screen, and the use of as small a cone of x-ray light as will enable the ends of the bones to be properly seen. While this method is of great value when properly done, yet one should be slow about drawing inferences as to correct position from fluoroscopic examination in a single direction. Radiographs with Patient in Bed. — It often occurs that in patients whose general condition does not warrant their removal to the radiographic table, the x-ray examination should preferably be made with the patient in his bed. It also happens that after a reduction has been made and extension has been present for a number of hours, it is highly desirable to find out if the fragments are in posi- tion. If the patient is moved to the x-ray room and the extension discontinued, it is obvious that the plates ob- tained may not represent the true condition of the frag- ments as afforded by the treatment in the patient's bed. The standard army bedside unit was designed especially to take care of this class of work without disturbing the patient more than is absolutely necessary. It is, of course, not always possible to make the examination fluoroscopic- ally at the bedside owing to the presence of the bed, which is likely to contain metal. In msmy cases, however, a lateral view may be secured fluoroscopically, and radiographic work can be done from above downward or laterally with- out difficulty. It should be observed that the limitations formerly present on portable apparatus such that heads, hips, etc., could not be successfully radiographed do not apply to this unit. By using the proper exposure, either with or without intensifjdng screens, radiographs of all parts of the body may be successfuly made, provided the part can be immobilized. It will be found that with good intensifvino^ screens and double-coated films the time of BONES AND JOINTS 303 exposure will differ but little from that used with the large machines without screens. Dislocations. — Examinations of the body for the deter- mination as to whether a dislocation is present or absent involve the same general applications of radiography as in the determination of the presence of fractures. The same principles of suitable penetration of the rays, im- mobilization as completely as possible of the part under examination, the employment of the stereoscopic method, and care in the interpretation of the plates obtained possess equal importance. In the detection of dislocations, the fluoroscopic method is of value in dislocations of the larger joints, as the shoulder, the elbow, knee and ankle. Dis- locations of the carpal bones and the metatarsal bones are not usually seen easily with the fluoroscope. The advan- tage of the fluoroscopic method in examination of the large joints, for example, the shoulder, lies in the fact that the position of the tube is easily shifted so that the rays will strike the joint at different angles. An observation of the shoulder joint from one angle may produce a dis- tortion which may be deceiving. In general, it may be said that the central rays should go through the joint surface under examination, and that they should strike the plate at a perpendicular. Oblique radiation, when used, should have its results interpreted very carefully. Reduction of Dislocations with Fluoroscopic Aid. — Re- duction of dislocations under fluoroscopic guidance is es- pecially advantageous; the operator can see constantly the relation of the two articulating surfaces and better plan his attempts at reduction. It is obvious that the same precautions should be observed as in manipulation of fractures under the fluoroscope. In all dislocations of large joints it is best to have stereoscopic plates of the joint, not only to determine the relative positions of the 30i U. S. ARMY X-RAY MANUAL articular surfaces but also to determine their inte^ity. Sprain fractures are a frequent complication of disloca- tions, and, if they can be detected, this knowledge assists materially in making the prognosis. Fluoroscopy vs. Radiography. — In fractures and dislo- cations radiography is the method of choice, since it reveals detail impossible to obtain on the screen and forms a per- manent record. The chief value of the fluoroscopic method, which can demonstrate only gross lesions, lies in its sim- plicity, speed, and comparative inexpensiveness. It is of value in positive diagnosis but is absolutely of no value when the findings are negative. Fracture of the Skull. — The shape of the skull and its elasticity, the close fitting covering of skin, muscle, fascia and periosteum on the outside, and the pressure of the intracranial contents and the dura on the inside, tend to immediately replace and maintain fractures in position. For this reason, we find fractures indicating only slight bony injury, the grave lesion being to the blood vessels, intracranial nerves, dura and brain substance and the secondary conditions arising therefrom; the presence or absence of fracture, in such, cases, fades into insignificance except as a clue to the site of the injury and a guide for surgical procedure. Varying from this class, we have the other extreme ; namely, those having an extensive bony lesion, as in de- pressed or perforating fractures, with or without injury to the underlying structures. In such cases, the location and character of the fracture must be considered. Here the force is consumed in breaking bone at the point of contact, the effect being dependent upon the amount of force, the point of injury and the character of the body producing the fracture. Between the two definite forms above mentioned, there BONES AND JOINTS 305 is much variance in the importance of the bony injury. Fractures of the skull may be divided into those of the vault and those involving the base. In over fifty per cent of the cases examined radiogTaphically there is found a combination of both. Fracture of the vault may be due to direct or indirect violence or it may be an extension from the base. There have been various theories advanced re- lating to these fractures, such as, Aran's theory of irradia- tion, the bursting theory, fractures by contrecoup and the Rawling theory of direct violence. It would seem as though each applied, as a causative factor, to certain classes of fracture of the skull. Experience shows that cases which are able to reach the roentgenologist present a fairly con- stant effect of clirect violence, the point of impact receiv- ing the maximum amount of bony injury ; from this point, we have radiating fracture lines which seek the weaker parts of the skull in the immediate neighborhood. The common fractures of the skull are described as : fissured, comminuted, diastasis of the sutures, depressed and perforated. The frequency with which these fractures are mistaken for various other conditions, especially in cases of coma, calls for a method which will make a rapid and positive diagnosis. On account of the many difficulties which are encountered in the correct diagnosis of head lesions the routine x-ray examination of the skull is of the greatest importance in all head injuries. It offers an actual visual demonstration of the presence or absence of fracture, its location, character and extent. Traumatic skull injuries should have systematic x-ray examination. If such examinations were made in all cases of head injuries, statistics would show a much greater percentage of fractures than at present. In a series of 300 cases in the writer 's experience, twenty per cent showed fracture. 306 U. S. ARMY X-RAY MANUAL When a case of head injury is referred to the roent- genologist for examination, the patient is often in an irri- table, semiconscious or comatose condition. Extreme pa- tience and perseverance are required, and it is even fre- quently necessary to administer a hypodermic of Ma- gendie's solution. It must be borne in mind that the minimum amount of distur'bance and movement is essential. In skull examinations, the patient's head must be abso- lutely fixed and, if possible, all respiratory movement over- come. If the objective symptoms, such as bleeding from the ear, nose or mouth, laceration of the scalp, hematoma or paralysis be present, they are a clue to the possible site of the fracture, and attention is naturally directed toward that area ; this must not mislead one, however, for every examination should cover the frontal, the parietotemporal, the occipital and basilar regions. It should be constantly borne in mind that examination of the skull requires a considerable amount of radiation for each plate taken. On this account it is absolutely neces- sary to use at least one millimeter of aluminum as a filter and to keep in mind the cumulative effect of the exposures and the fact that the areas receiving radiation during the different examinations overlap to some extent. Where the required current of 40 ma. at a 5-inch gap cannot be secured, one should not attempt to do the work at a lower gap, but should maintain the gap at the ex- pense of current. Thus, if one must use 5 ma. instead of 40, still at a 5-inch gap, the time of exposure at the same distance must be eight times as long. For 10 ma. four times as long. The objectionable feature in this procedure is the increased difficulty of immobilization for the longer periods. Frontal Region. — In the examination of the frontal region, we should endeavor to show as much of the vertical BONES AND JOINTS 307 plate of the frontal bone as possible. The patient is placed on the table fiat on the abdomen with face resting on the plate. The glabella should be in contact with the plate. An imaginary line running through the glabella and sym- physis of the jaw should be parallel to the axis of the plate. The head should then be firmly fixed either by clamps or Pig. 140. Position for examination of frontal region of skull. sand-bags, care being taken not to rotate the head during this immobilization. The tube should then be adjusted so that the ray through the center of the diaphragm passes through the center of the glabella. Target-plate distance should be about 22 inches. Fig. 1-iO. A 5-inch spark-gap is used, forty to forty-five milli- amperes and an exposure of about six to eight seconds. In the majority of cases this procedure will give satisfactory plates of the frontal region. 308 U. S. ARMY X-RAY MANUAL If circumstances require the use of the portable table, the fluoroscopic screen should be replaced by the tube holder. Should it be necessary to use the portable outfit with a 5-inch gap and ten milliamperes, the exposure would be about thirty to thirty-five seconds. The bedside unit being limited to 5-inch spark-gap and five milli- FiG. 141. Position for examination of temporoparietal region of skull. amperes, it would be best to use an intensifying screen and a properly modified exposure. Temporoparietal. — In examining the temporoparietal region, we should show that portion of the skull lying between the sagittal suture above, the coronal suture an- teriorly, the lambdoid suture posteriorly and including the entire temporal bone. Both sides of the head must be ex- amined. The patient lies on his side with neck slightly extended, the center of the temporal region resting upon BONES AND JOINTS 309 the plate. The head is raised or lowered until a line ex- tending from the glabella to the symphysis of the lower jaw is parallel with the plate. The tube is adjusted over the center of the temporal region, perpendicular to the plate at a distance of twentij-four inches. The head should be securely clamped or held by a weighted bandage. Fig. 141. Fig. 142. Position for examination of posterior (occipital) region of skull. The same electrical conditions govern the tube as when examining the frontal region, except that it is seldom neces- sary to make the exposure longer than three or four seconds. Posterior Region. — When examining the posterior re- gion, we must bring out with clear detail the entire occipi- tal bone, with the lambdoid sutures like an inverted V above, the mastoids on either side and the foramen mag- num below. The patient lies on his back on the top of the 310 U. S. ARMY X-RAY MANUAL table with the occiput flat down on the plate, the center of the occipital bone being placed in contact with the plate. The head should be slightly flexed so that the central ray (tube tilted 15° toward the feet) enters the forehead just above and between the frontal eminences. If a cone is used, the lower border of the cone should not extend be- low the supraorbital ridges. The head is clamped or held in position by a weighted bandage. Fig. 142. An expo- sure of about nine seconds is made with a tube taking about forty milliamperes and with a gap of five inches. Base Region. — In cases of suspected fracture of the base the vertical technique, as advocated by D. R. Bowen for examination of the sphenoidal sinuses, may be used with slight modification. To carry out this method it is necessary to elevate the shoulders a few inches so that extension of the neck is obtained. The head should be so placed that a line drawn from the glabella to the external auditory meatus is parallel to the plate. The tube is then adjusted so that the central ray through a two-inch opening in a lead diaphragm is centered midway between the midlarynx and the symphysis of the jaw. This central ray will be in a plane about one inch in front of the external auditory meatus. The target should be at a distance of about twenty-two inches from the plate or film. The patient's head must be securely immobilized and clamped if necessary. Fig. 143. With the tube taking forty milliamperes at a 5-inch gap, an exposure of about ten seconds will be required. Having obtained satisfactory plates, it is necessary to have the experience and anatomical knowledge to make the correct interpretation. In reading plates of the base of the skull, beginning behind, we see the foramen magnum and within it the odontoid process of the axis. Just for- BONES AND JOINTS 311 ward of this opening, on either side, the mastoids are dis- tinctly reproduced with the associated shadows of the petrous portion of the temporal bone. Anterior to this is a clear view of the middle fossa. If the chin is not too extended, the anterior fossa can be seen in front of the overlying shadow of the lower jaw. Fractures of the zygo- FiG. 143. Position for examination of basilar region of skuU. matic arch, with, the extent of displacement, are usually beautifully shown in radiograms of the base. In the interpretation of the frontal, lateral and occip- ital regions one must note the suture markings and the normal radiating lines cast by the grooves on the inner table of the skull, which accommodate the meningeal ves- sels ; these grooves spread fan-shaped from an anterior point backward. The shadows cast by the diploic spaces, between 312 U. S. ARMY X-RAY ^MANUAL the inner and outer tables of the skull, are lines extending vertically upward from the base, interlacing at the top and terminating as a rule in an anterior and a posterior lake. They are directly at variance with the shadows rep- resenting the meningeal grooves. Fractures usually show as dark, sharply cut lines of varying width, depending upon the extent of separation ; they may be vertical, horizontal or curved, but seldom directed in the same manner as the blood vessel grooves. In addition, we wish to especially emphasize the value of the stereoscopic examination in these head injuries. It is often difficult in cases of slight depression for the sur- geon to decide whether to interfere or not. The presence or absence of symptoms of intracranial pressure and the actual demonstration of the condition of the inner table of the skull, with the amount of depression, if any, are vital facts which should be considered before a decision is made. Lateral stereoscopic plates aid in tracing the fracture line into the base and locating the termination. In the common penetrating fractures of the vertical plate of the frontal bone and those cases of linear fracture extending into the roof of the orbit, they are of extreme value, as giving the most accurate estimate of the seriousness of the bony injury. Examination of Spine. — On account of the importance and frequency of spinal injuries, some special instruction may be found desirable. The roentgenologist who is un- familiar with the indications of anatomy as shown on the x-ray plate with reference to the spine would do well to review carefully the anatomy and study with considerable care plates made of normal individuals in which the spine is clearly shown. Attention is also called to paragraph on page 320 with reference to certain abnormalities which are of frequent occurrence. BONES AND JOINTS 313 Generally speaking, fluoroscopic examination is of little value in examinations of the spine on account of the thick- ness of tissue and the necessarily small degree of contrast which may be secured. It is frequently, however, of value to use a small screen in the examination of the cervical region. On account of the considerable number of bony projec- tions and spinous processes and the peculiar curvature of the column as a whole, it is frequently difficult to secure plates depicting the vertebra with sufficient accuracy for diagnostic purposes, and unless great care is taken to fol- low a definite procedure, information can hardly be secured by comparison of plates. Fig. 144 shows an outline of the spinal column with its common divisions into cervical, thoracic and lumbar. The lateral view clearly indicates the necessary superposi- tion of shadows, and it can be readily seen how slight modi- fications in position may result in very considerable defor- mation of shadow outline. Possibly the best general rule would be that the central portion of the beam used should be, as near as possible, perpendicular to the spinal column, and in all cases the target must be symmetrically placed over the spine. Attention must also be called to the fact that the patient should be moved and handled as little as possible and al- ways with extreme care, as not only are these spinal injuries likely to be extremely painful, but careless handling is very likely to bring about injury to the cord even if this were not present before examination. Most of the examinations are made in the supine posi- tion, and it is essential to have the plate or film come as nearly as possible in contact with the body so as to avoid distortion and hazing of the shadow by reason of distance of the spine from the plate. In some cases it will be neces- 314 U. S. AR^IY X-RAY MANUAL sary to turn the patient on the side or partially so for lateral examination, in which ease sj^ecial care will be needed. Fig. 144. The normal spine has general divisions into cervical, thoracic and lumbar. The projection lines from targets do not rep- resent standard positions, but simply illustrate the projection, if the central rays are perpendicular to spinal column. The operator can vary opening of cone, size of plate and position so as to bring out special features desired. i^^ractures of the spine may be simple or compound, due to either direct or indirect violence. The most common is the compression fracture of the body of the vertebrae, BONES AND JOINTS 315 which occurs more frequently in the lower thoracic and upper lumbar reg:ions. It may also be seen in the mid- cervicals. In a large percentage of this type of fracture there is an associated dislocation, the displacement in the cervicals being anteroposterior, while the thoracic and lum- bar are more frequently displaced laterally. Transverse or spinous processes may be fractured either by direct violence or by muscular action. This class of injuries is usually caused by forcible bending, as in ex- treme flexion, resulting from a fall. These fractures may involve one or more vertebrae; the bodies are somewhat flattened longitudinally and usually show a wedge-shaped formation. In certain cases there is a true splintering of the bone instead of crushing of the body, and in these cases there is great danger of injury to the cord, due to the action of bony fragments. As a general rule no preparation of the patient is re- quired excepting in the case of the lower thoracic and lumbar vertebrae, in which case a thorough cleansing by cathartic is desirable. It is always well to make stereoscopic plates when in doubt, and in this case some variation in the time of ex- posure of the two plates may be of advantage. The following brief summary of the positions and ex- posures is given and it is suggested that the roentgenologist who has not had experience in this work undertake to make plates in these positions with normal subjects, when time permits, so as to more fully understand the work and be able to carry it out with the least amount of disturbance to the patient. Upper Cervicals.— Fig. 145. The head should be sup- ported by the wooden wedge used in frontal sinus work, or otherwise, the head being semiflexed. The mouth may be held open by a large cork, placed as far back between 316 U. S. ARMY X-RAY MANUAL the molars on one side as possible. Care should be taken to fix the head in position and the central ray should be perpendicular to the plate, passing directly through the open mouth. A distance of 22 inches will be found de- sirable and an approximate exposure, at 40 ma., 5-inch Fig. 145. Spine examination, anteroposterior position for upper cervical vertebras. gap, of from 3 to 5 seconds, with the usual base hospital outfit. Lower Cervicals. — Fig. 146. The ventrodorsal projec- tion of the lower cervicals is best obtained by supporting the plate or film beneath the patient at such an angle as to bring it in contact with the region sought. In this case, also, it will be necessary to fix the head in position to avoid hazing of the plate by movement. Exposure 40 ma., 5-inch gap, 22-inch target-plate distance, 3 to 5 seconds. BONES AND JOINTS 317 Fig. 146. Spine examination, anteroposterior position for lower cervical vertebrae. Fig. 147. Spine examination, lateral position for examination of cervical vertebrae. 318 U. S. ARMY X-RAY MANUAL If a lateral view is desired, the patient should not be turned on his side in the case of injury to the cervical vertebrae, but a plate pressed well down against the shoul- der and properly supported by sand-bags or otherwise may be used. Fig. 147. For a lateral examination it is well to have the shoulders slightly elevated and to be sure that Fig. 148. Spine examination, anteroposterior position for tho- racic vertebrae. the plate covers the region sought. It may be necessary to work at 28 inches, in which case, with 40 ma. and a 5-inch gap, 5 to 7 seconds may be needed. Thoracic Vertebrae. — The thoracic vertebras may be taken on a large plate with a target-plate distance of 28 inches, or by the use of two small plates and two separate exposures. Fig. 148. The latter is generally more satis- BONES AND JOINTS 319 Fig. 149. Spine examination, position for lateral examination of thoracic vertebra. Fig. 150. Spine examination, anteroposterior position for upper lumbar region. Note flexion of knees. 320 U. S. ARMY X-RAY MANUAL factory. With 40 ma., a 5-inch gap, 28-inch target-plate distance, the time required will be from 5 to 8 seconds. The proper plate density requires careful attention, on account of the mass of superimposed material that must be penetrated. The position for lateral examination is shown in Fig. 149, and will generally require somewhat longer exposure than the ventrodorsal, running from 6 to 10 seconds with the same current, gap and distance as before. Upper Lumbar Region. — On account of the considerable curvature of the midlumbars special care should be taken in placing the tube and patient in order to bring out the positions of the vertebrae without overlapping. The pa- tient should lie flat on the back and the knees should be semiflexed in order to bring the spine as close to the plate as possible. The central ray should pass through the 12th thoracic vertebra approximately, and in some cases a cone for compression will be found desirable in order to dimin- ish the path of the rays in the body. Fig. 150. At 40 ma., 5-inch gap, 22 inches will require from 6 to 8 seconds. Positions for other portions of the lower spine are indi- cated in Figs. 151 and 152 and require some practice in order to bring out the features desired. If a lateral is required of the lower spine, it will generally be desirable to use an intensifying screen, and, if this is reasonably fast, the time for the lateral exposure with the screen will not differ materially from that for the anteroposterior when no screen is used. Abnormalities of the Spine. — Before discussing the pa- thological changes in the spine it is well to remember that it is the seat of more abnormalities than any other part of the bony structure. Certain of these abnormali- ties while not pathological in the sense of disease yet may BONES AND JOINTS 321 m :\ -" I -^r ^H D = 1 Y^^ .X g^^_ ^_ ^^ Fig. 151. Spine examination, lateral position for lumbar vertebrae. «^ .-..V. '-'•'•■ t%-- PiG. 152, Spine examination, anteroposterior position for lower humbar vertebrae. 322 U. S. ARMY X-RAY MANUAL produce symptoms. For convenience it is well to con- sider them according to their locations, namely, cervical, dorsal, and lumbosacral. In the cervical region the most common abnormality is the presence of extra ribs. They generally spring from the seventh cervical; may be either unilateral or bilateral, the former being the most common. They frequently pro- duce pain and numbness in the arm and sometimes atrophy of certain muscles. The symptoms usually lead to a diag- nosis of neuritis which, if due to pressure from one of these ribs, will not yield to medical treatment, as removal of the ribs is the only cure. When unilateral the diagnosis is easy, as one will note that the corresponding rib on the opposite side is absent. When there are two cervical ribs the diagnosis is more difficult, as they may be mistaken for the pair of normal first dorsal ribs. This can be deter- mined only by examination of the entire dorsal spine to ascertain whether twelve or thirteen pairs of ribs are pres- ent. If there are thirteen, we know we are dealing with an extra pair of cervical ribs. The seventh cervical ver- tebra, from the radiological appearance, is so similar to the first dorsal that no conclusions can be drawn as to whether the ribs arise from the seventh cervical or first dorsal vertebra. The fact that there may be six cervical vertebrae does not mean that we are dealing with an extra pair of ribs, as the attachment of the ribs is variable. Sometimes they are attached one vertebra too high or one vertebra too low. It is quite common to find six cervical, twelve dorsal and six lumbar vertebrae, or eight cervical, twelve dorsal and four lumbar vertebrae. While these extra ribs nearly always spring from the seventh cervical vertebra, it is well to remember that on very rare occasions they may be attached higher up. BONES AND JOINTS 323 Congenital nonunion of the laminae that form the spinous processes is quite common in the seventh cervical. On account of the narrow space between the laminae this is often mistaken for a fracture. In the dorsal vertebra? we may also have congenital non- union of the laminae, generally confined to the upper two or three. Rudimentary vertebrae, triangular in shape, are sometimes seen inserted between the vertebrae. Since they are triangular in shape and inserted on one side, scoliosis invariably results. This is important, as such a condition will not yield to the ordinary treatment for scoliosis. In the lumbosacral region nearly all of our abnormali- ties are confined to the fifth lumbar and sacrum. Con- genital nonunion of the lamina of the fifth lumbar and top of the sacrum is quite common. In a thousand examina- tions of that region for various conditions this nonunion occurred in over fifteen per cent of the cases. This is dwelt upon because the writer has seen so many cases in which this condition was diagnosed as fracture. Occasion- ally an extra pair of ribs may arise from the first lumbar. Another frequent abnormality is where the fifth lumbar takes on characteristics of the sacrum — the transverse processes on one or both sides become fused with the sacrum and the fifth lumbar becomes integral therewith. When only one side is united symptoms frequently occur. The so-called sacro-iliac subluxation or strain seems to be in reality a ligamentous rather than a bony change. In such conditions one will frequently see one side of the sacrum higher than the other, suggesting a slipping. When the patient is manipulated under anesthesia all symp- toms may disappear, and second examination fails to show that the improvement has resulted from any change in the position of the sacrum. 324 U. S. ARMY X-RAY IMANUAL Great care must be taken in centering the tube to secure a symmetrical position in this examination, and if conclu- sions are to be drawn from a second examination as re- gards the effect of treatment or manipulation, it is of vital importance to reproduce all the factors of position and ex- posure, in order that distortion may not be mistaken for real change in bony structure. It is advised that the tube be centered over the lumbosacral articulation. While many of these cases of indefinite pain and dis- comfort in this region may be due to ligamentous rather than bony changes, it must be borne in mind that we do have at times a slipping of the fifth lumbar vertebra. A lateral view of the fifth lumbar and top of the sacrum may show the body of the fifth lumbar projecting anterior to the top of the sacrum. Pathological Processes in the Spine. — In dealing with the pathological processes incident to the spine we have practically the same changes as seen in the other bones with certain modifications. For convenience of classifica- tion the writer has divided the lesions according to their origin as follows : 1. Joint lesions. Lesions arising from and involving the articulating surfaces. 2. Transitional lesions. Lesions arising from the articu- lating surfaces and involving the body of the vertebrge. 3. Bone lesions. Lesions arising from the body and not involving the articulating surfaces. In class one will fall the various types of arthritis, name- ly, infectious, atrophic and hypertrophic, and the first stage of tuberculosis. In class two we have the destructive stage of tubercu- losis, fractures, and the neuropathic conditions such as Charcot and syringomyelia. In class three we have the new growths and occasionally BONES AND JOINTS 325 osteomyelitis, though this may come under class two, ac- cording to whether the joint is involved or not. Spinal Joint Lesions. — In dealing with class one, the joint infections, certain changes seen in the joints of long bones are not present, that is, we do not see any peri-articular or fluid changes, so our diagnostic points rest entirely upon the cartilaginous destruction and bone production. In the arthritic cases, nontuberculous, we seldom see any narrowing of the joint space, but at the edges of the ver- tebra?, particularly where the lateral ligaments attach, the edge will first become sharpened and then exostoses will form, growing toward the joint space, and finally will unite with the exostoses from the other surface of the joint and produce a true bony ankylosis at that point. This may be so extensive that all the vertebra will become ankylosed. There is no change in the body of the vertebrte. AYe can- not differentiate the various types of arthritis. In the early stages of tuberculosis we get destruction of cartilage and some narrowing of the joint, but the disease proceeds to attack the body of the vertebra and then we get the second class, or the transitional type, where joint and body are involved. Transitional Spinal Lesio7is. — In tuberculosis the anterior portion of the body of the vertebra becomes softened and then from pressure gives way, assuming a characteristic ap- pearance, namely, the body becomes triangular in shape with the apex anterior and the base of the triangle poste- rior. This gives us the characteristic angulation or knuckle, the true tuberculous kyphosis. Tuberculosis is a destructive process, not a bone producer. The three im- portant differential points to remember with this lesion are (1) angulation; (2) deformity, anterior and posterior; (3) practically no bone production. 326 U. S. ARMY X-RAY MANUAL In fracture and dislocation of the spine, and they are generally present together, we have destruction of the joint and more or less crushing of the vertebras. The displace- ment is lateral and soon there is marked new bone forma- tion. The three important differential points are (1) angulation; (2) deformity, lateral; (3) new formation of bone. The above applies only to the dorsolumbar region. In the cervical region in fracture and dislocation, the dis- placement is frequently anteroposterior instead of lateral, though both may occur. Besides the fracture-dislocation of the bodies proper, fracture of the transverse processes in the lumbar region is quite common. These not only follow from injury but from violent strains. They are generally easily recognized, as there is always more or less separation of the fragments and the outer end is frequently displaced upward. In the neuropathic conditions, namely, Charcot, there is always the lateral crushing of the joint, and the body is involved with the formation of bony detritus, seldom new bone formation. The three differential points are (1) an- gulation; (2) deformity, lateral; (3) seldom new bone for- mation, bu,t generally bony detritus present. Spinal Bone Lesions. — The most common lesions are the new growths, and the same system of differentiation applies here as in growths of the long bones. When the growth arises from the edge of the vertebra and there is bone pro- duction outside, the condition may simulate fracture and dislocation, but the striking point is that in growths the joint is not involved. In sarcoma and carcinoma a portion of the vertebra may be completely absorbed, but, on account of the density of the growth, crushing of the body takes place slowly and BONES AND JOINTS 327 equally. The body will become narrowed, but the joint spaces will be intact and clearly seen. A vertebra that is much smaller in width with joint spaces intact should always be viewed with the possibility of growth in mind. The characteristic points are (1) no angulation; (2) no displacement; (3) narrowing of body with or without bone production, according to type of tumor. Osteomyelitis is uncommon, though the writer has seen one case of typhoid origin involving both the joint and body. The changes observed were the same as seen in osteomyelitis of the long bones. Lesions of the Long Bones. — In discussing the patho- logical lesions that take place in bones w^e must remem- ber that w^e have three normal constituents to deal with, namely, the medullary canal and its contents, the cortex, and the periosteum. From an x-ray standpoint there are only two pathological changes that take place, namely, bone destruction and bone production. It mat- ters not ^vhat the nature of the lesion is, one or both of these processes are present. It is only by a careful analysis of the character of the destruction and the character of the bone production that w^e are enabled to differentiate these lesions. The most important thing to determine is whether we are dealing with a malignant or a benign condition. If that point can be determined, we have given the surgeon or clinician all the information that is necessary. It is, however, better if we can go further and determine the exact nature of the lesion. In taking up the subject of tumors of bone there are certain well-known manifestations which are fairly char- acteristic of certain lesions. By studying the point of origin and the character of the bone changes we have been led to formulate a rough scheme for the analysis of these 328 U. S. ARMY X-RAY MANUAL various bone tumors. We have taken as a basis four car- dinal points which are as follows: origin of the tumor; presence or absence of bone production; the condition of the cortex ; and, finally, invasion. At first glance it is often impossible to determine all four of these points, but, if we can establish one or two of them, they frequently lead to the correct diagnosis. Discussing these four points, the salient features are as follows : Point of Origin. — By that we mean whether the growth arises in the medullary canal or springs from the cortex or periosteum. If this point can be determined we have established one point of differential diagnosis. All tumors in bone must be either primary or metastatic. We know, for example, since there is no epithelial tissue in bone, that if we have a carcinoma it must enter the bone by means of the lymph vessel with the nutrient artery, and, consequently, the growth must start in the medullary cavity. Therefore, if we can establish the point that the growth does not arise in the medullary cavity, we have ruled out carcinoma. On the other hand, since sarcoma is of connective-tissue origin it can be either primary in the medullary canal or of metastatic origin. We know, too, that enchondromata and bone cysts may also arise from the medullary cavity, so we have to proceed to the other cardinal points to establish a differential diagnosis. Bone Production. — Bone production cannot take place in either carcinoma or in the round-cell, spindle-cell and giant-cell sarcomata. Consequently, if we can establish the point that there is bone production within the tumor, the above-mentioned tumors can be ruled out. That, in turn, will again limit the tumors to osteoma, osteochon- droma, periosteal sarcoma, osteosarcoma, and ossifying BONES AND JOINTS 329 hematoma — the latter arising beneath the periosteum is very frequently mistaken for a malignant growth. Cortex. — For further differentiation we have to proceed to the third cardinal point, namely, the cortex. AYe must determine whether the cortex is present or absent, and, if present, whether it is expanded in a spherical or longi- tudinal manner. Secondly, we must determine whether the growth springs from the cortex or periosteum. If we can definitely establish that a grow^th springs from the cortex or periosteum it must be a bone-producing tumor, and the character of the bone production will definitely aid us in determining the nature of the tumor. The condition of the cortex is also a very important factor. Experience has shown us that benign tumors aris- ing in the medullary canal always take the path of least resistance, that is, they have a tendency to grow up and down the shaft in the medullary canal rather than towards the cortex of the bone. The pressure from the growth, however, causes an expansion of the cortex, but the expan- sion is always spindle-shaped or cj^indrical and the cortex is always intact. On the other hand, in malignant condi- tions the growth is always spherical in nature and extends equally in all directions. The cortex does not offer any interference, and the growth sweeps through and destroys it, so that in this character of growth the cortex is absent, and if a trace of it remains it has not been expanded. There is only one exception to this, and that is the giant-cell sarcoma. As its name implies, it belongs to the sarcoma- tous group, but, on account of the character of the cell, metastasis is almost impossible, so that we are dealing with practically a benign condition. It is a very slow growing tumor, but it grows in a spherical manner, and on account of its slow growth the cortex is expanded in all directions 330 U. S. ARMY X-RAY MANUAL but is not destroyed. The growth, too, is definitely limited in the medullary canal. Invasion. — The fourth point, invasion, is frequently the hardest to determine. If, however, it can be determined, it is the most important of all points. If we can establish defi- nitely that the growth is invasive, by that meaning infiltra- tion into bone and soft tissue, we have in reality determined everything, because malignancy depends upon invasion. After determining these four points it is well then to take up what might be termed the laws of probabilities. By these laws we mean what is most frequently found when the age and the sex of the patient are taken into consideration, and what particular bone is involved. As an example, if the patient is a female, statistics show that carcinomata of the breast and of the pelvic organs are by far the most common. We also know that in carcinomata of the breast metastases occur most frequently in the greater trochanter, the spine, ribs, humeri and the ilia. In carcinoma of the pelvic organs the metastases are generally in the lumbar spine. In the male we know that carcinomata of the lip and tongue and of the genito-urinary organs are most common. With the lip and tongue, if metastases do occur, they take place chiefly in the mandible. In carcinomata of the genito-urinary organs, particularly the prostate, the metastases occur in the pelvis and lumbar spine. Thus we see that knowledge of the sex of the patient is frequently an important aid to diagnosis. A second application of the law of probabilities, namely, the age of the patient, helps us very materially. In the first place, since carcinoma of the bone is a metastatic condition we must always look elsewhere for the primary growth. Then, too, experience has taught us that carci- noma is unusual in the young individual, but is essentially a disease of middle and old age. On the other hand, sar- BONES AND JOINTS 331 coma may occur at any age. In diagnosing a tumor in a young individual, the law of probabilities indicates that it is more likely to be a sarcoma than carcinoma ; in an old individual it may be either a sarcoma or a carcinoma. The particular bone involved when sarcoma is present does not help us because sarcoma may be primary in the bone and, consequently, can form in any bone. The fol- lowing are the chief characteristics of the more common bone tumors : Specific Lesions. — Carcinoma is always medullary in origin and, since it enters by means of the lymph vessels, it must enter the bone with the nutrient artery, that is, at its middle point. Consequently, we may say by the law of probabilities that carcinoma is more apt to be sit- uated in the region where the nutrient artery enters. Since it is epithelial in origin, there is no bone produc- tion within the tumor; it grows equally in all directions, does not expand the cortex but destroys it completely, and shows distinct signs of invasion dow^n in the med- ullary cavity and soft tissues. This tumor occurs in mid- dle and old age. Bound-cell sarcoma is also very malignant and its char- acteristics are identically the same as those of carcinoma. As far as the growth is concerned it cannot be differentiated from carcinoma upon the x-ray plate. In such a growth, to make a differential diagnosis between it and carcinoma, we must again refer to the law of probabilities, namely, sex, age and bones involved. Its situation in the bone itself is of some significance because, while sarcoma may occur in any part of the bone, carcinoma is most frequent near the nutrient arterj^ ; so a tumor at the end of bones, by the law of probabilities, is more apt to be a sarcoma than carcinoma. Spindle-cell sarcoma while malignant is not as much so 332 U. S. ARMY X-RAY MANUAL as round-cell sarcoma. It also destroys equally in all direc- tions ; does not produce any bone ; destroys the cortex, does not expand it; but the growth does not show the same degree of invasion in the medullary canal as the more malignant round-cell sarcoma. Periosteal sarcoma, as its name implies, arises from the periosteum. It produces bone, but the major portion of the bone is laid down in the soft tissues. The shaft of the bone shows but very little destruction. This tumor is so malignant that death ensues before the growth has destroyed the bone to any extent, as most of its growth extends into the soft tissues. The bony production is very typical and characteristic, namely, it is laid down in long stria and is invariably perpendicular to the shaft. Osteosarcoma arises from the cortex of the bone. It is frequently impossible to determine whether it arises from the medullary canal or not. If the growth should start on the inner surface of the cortex next to the medullary canal, since it grows equally in all directions, one might think that it arose from the medullary canal. So the point of origin in some of these cases does not help us, but the fact that there is bone production within the growth is of great significance. The shaft of the bone is somewhat destroyed and there is new bone production, not only within the shaft but, like the periosteal sarcoma, within the soft tissues. This bone, like the periosteal sarcoma, is laid down perpendicular to the shaft, and in osteosarcoma there is generally more bone production than in the periosteal type. The sarcomata may occur at any age. The fact that in both of these malignant conditions the bone is laid down perpendicularly to the shaft is of special significance and will be discussed a little later. The metastases in prostatic carcinoma give the same x-ray signs as the other forms of carcinoma with this ex- BOXES AND JOINTS 333 ception. Since this type of tumor grows very slowly we find production of new bone not within the growth but just at the edge of the growth in the normal bone, in other words, at the point of stimulation. Consequently, this growth seems to be encapsulated in a calcium wall, nature attempting to limit the growth. These metastases are most commonly seen in the pelvic bones, sacrum and lower lumbar vertebrae; and in people of middle or old age. Giant-cell sarcoma develops from the medullary portion of the bone and expands equally in all directions, similar to a malignant grow^th. It is, however, definitely limited; the cortex is expanded but intact. There is no new bone formation. It is generally seen between the ages of twenty and thirty. The growth is usually situated at the end of the bone, and the radius and tibia seem to be the bones most commonly involved. Enchondroma, as its name implies, is cartilaginous in origin and is generally seen before the epiphyses have united. The early recognition is probably due to the fact that fractures take place through this growth quite readily ; the patient comes in for the fracture and the tumor is then discovered. The growth is situated near the ends of the bones in the region of the epiphyseal line, seldom extend- ing beyond this line into the epiphysis proper. It is gen- erally multiple and the growth is cystic in character — one growth may contain several cystlike formations. It extends up and down the shaft; the cortex is expanded in a spindle-shaped manner but intact. There is no new bone formation unless there has been an injury. It may arise either from the medullary portion or the cortex. Any of the long bones in the body may be involved, the phalanges of the hands being probably the most common. These us- ually occur between the ages of seven and fifteen years. A cyst is seen most commonly in the same ages as the 334 U. S. ARMY X-RAY MANUAL enchondroma and, like it, occurs at the ends of the bones in the region of the epiphyseal line. It extends up and down the shaft ; the cortex is expanded in a spindle shape ; the cyst may be lobulated, but is generally one large single cavity; the cortex is intact and the walls of the cyst are sharply defined. Cysts are supposed to be multiple, but in a great number of cases observed by the writer no case of multiple cysts was found. Cysts are generally medullary in origin and occasionally, but rarely, may spring from the cortex. Osteoma arises from the cortex and, as its name implies, is a dense bony tumor. The growth extends out into the soft tissues, the bone being laid down very symmetrically, and has the typical cauliflower appearance. It is fre- quently lobulated, has a very definite outline, and no sign of invasion. These growths are generally multiple at the point of origin, are seen most commonly in the young, and are generally perpendicular to the shaft. The bone in these growths is much denser than the shaft and does not have the same bony structure. Exostoses are sometimes mis- taken for small osteomata. Exostoses, however, have the same character of bone formation as the shaft ; they spring from the shaft at an angle and always point away from the nearest epiphysis. Occasionally one may see such an exostosis with an osteoma forming at the tip. The most common situation for osteomata is around the shoulder and in the neighborhood of the knee joint. Ossifying kematomata, while quite common, are at the same time often mistaken for malignant growths clinically. The x-ray appearance, however, is quite different. This lesion is caused by some trauma to the periosteum which causes the formation of a hemorrhage beneath the perios- teum and it, in turn, is raised up by the hemorrhage. When this first takes place the x-ray appearance does not help BONES AND JOINTS 335 us, as it reveals nothing, but at the end of about three weeks the periosteum wiii lay down new bone and the hemorrhage beneath it will undergo organization with a deposition of calcium salts. The calcium salts, however, are laid down parallel to the bone, and the periosteum, of course, makes a definite border to the growth. In adult life this is most commonly seen in the thigh ; in children it may occur in any bone but only in connection with scurvy. Special attention must be given to the way in which the new bone is laid down in this condition. "We have already spoken of four conditions in which bone has apparently been thrown down in the soft tissues: two malignant con- ditions, periosteal sarcoma and osteosarcoma ; two benign conditions, osteoma and ossifying hematoma. The impor- tant differential point is that in malignant conditions the bone is laid down perpendicular to the shaft and in benign conditions it is laid down parallel to the shaft. Osteitis fibrosa cystica is occasionally seen and can easily be classified as a benign condition by the fact that the bone has become softened and deformities have resulted, particularly^ around the head of the femur. The shaft is expanded cylindrically, the cortex is intact and the bone itself is frequently filled with multiple cystlike formations. It generally occurs in the young adult. Paget' s disease is sometimes mistaken for osteomyelitis. It is seen in the long bones, particularly the tibia and femur, and the cranial bones are also affected. The long bones may be somewhat bowed, there are long longitudinal strise of absorption present and longitudinal areas of in- creased calcium salts. The cortex in places may be thick- ened. The changes in the cranial bones, however, are most characteristic. The head seems to be enlarged, and the x-ray appearance shows that the parietal, frontal and occip- ital bones are very much thickened by knobbylike deposits 336 U. S. ARMY X-RAY MANUAL of bone. In acromegaly the cranial bones are very much thickened ; the head seems to be elongated anteroposteriorly and the lower jaw projects markedly forward. The sella turcica is frequently enlarged and deepened. The bones and soft tissues of the hands and feet are very mu.ch enlarged, and the tufting of the terminal phalanges is materially increased. Brain Tumors. — In speaking of the changes in the cranial bones it is well to mention in this connection some of the characteristic signs of brain tumors. Unfortunately, the x-ray evidence for these tumors is not particularly reliable, as a vast majority of brain tumors are of the same consistency as the brain itself and, consequently, there can be no differentiation between the tumor and the brain. We have to depend entirely upon other signs, and, unfortunately, they are late manifestations of the tumor, namely, erosion of the bone, due to pressure, and engorgement of the vessels — these vessels having a tend-' ency to center at one point, that is, in the growth. This indirect evidence, however, cannot always be relied upon. In tumors of the hypophysis the signs of pressure appear earlier. Since this gland is closely confined in the sella turcica the pressure symptoms, such as erosion and dis- tortion of the bone, appear early. Osteomyelitis. — Care must be taken not to confuse in- flammatory growths of bone with tumors. This is par- ticularly true in osteomyelitis. This disease gives no defi- nite x-ray signs during the early stages (first ten days). Later we find destruction within the bone with the for- mation of sequestra, and the disease extends down the shaft in an irregular manner, but the shaft is never ex- panded. The periosteum may lay down new bone which may give the appearance of expansion, but upon looking at the plate closely we will see that the apparent expan- BONES AND JOINTS 337 sion is clue to the deposition of bone on the outside. When the disease breaks through the cortex it does so in one or two places only and does not destroy the cortex as a whole, as the malignant tumors do. It is sometimes quite difficult to differentiate between simple osteomyelitis and that oc- casioned by lues. It is well to bear in mind that when we have, apparently, an extensive osteomyelitis of the bone, very little swelling of the soft tissues, and very few clini- cal signs, the condition is more apt to be luetic in origin, as the acute simple inflammatory osteomyelitis is generally accompanied by marked clinical signs and marked soft tissue swelling, redness and fever. Periostitis may be a simple inflammatory lesion or luetic in origin. It is sometimes very difficult to differentiate these two conditions. The simple inflammatory periostitis lays down the periosteal bone parallel to the shaft. Luetic periostitis also generally lays down bone parallel to the shaft, but occasionally the new periosteal bone may be laid down perpendicular to the shaft very similar to that seen in certain bony malignancies. In the luetic periostitis, however, the amount of bone is small and closely confined to the shaft, not extending out into the soft tissues, so that a mistake can probably seldom arise. In luetic perios- titis more than one bone is frequently involved, while the simple inflammatory type generally affects only one bone. The cardinal points which have just been given for bone lesions hold only for the long bones and not for the flat bones, as in the flat bones the growth is so frequently atypical. A second important point to remember is, that, if there has been any surgical interference, no conclu- sions can be drawn from the x-ray standpoint, because the diagnosis depends upon bone destruction and bone pro- duction. If there has been trauma or surgical interfer- ence the new bone production may be due entirely to the 338 U. S. ARMY X-RAY MANUAL two latter conditions. Consequently, we may draw false conclusions, since these changes are not due to the tumor itself. Tuberculosis of the joints with direct extension of the disease into the heads of the bone forming the joint has been taken up in the section on arthritis. Tuberculosis of the long bones without the joint involvement is so ex- tremely rare that it does not come within the scope of this manual. Below is a summary of the bone tumors according to the four cardinal points : 1. Origin-Medullary. Sarcoma Carcinoma Bone cysts Enchondroma Giant-cell sarcoma 2. Cortical. Periosteal sarcoma Osteosarcoma Osteom.a Enchondroma Ossifying hematoma Occasionally bone cysts 3. Bone Production. Periosteal sarcoma Osteosarcoma Osteoma Ossifying hematoma Enchondroma and bone cysts (when there has been trauma) 4. Cortex not expanded but destroyed. Sarcoma BONES AND JOINTS 339 Carcinoma Osteosarcoma Periosteal sarcoma 5. Cortex expanded and intact. Enchondroma Bone cysts Giant-cell sarcoma 6. Invasion. All of the malignant tumors show invasion. Arthritis. — A normal joint is composed of three parts, namely, cartilage, synovial membrane and the synovial fluid. There is no free bone in the joint proper; the con- sequence is that in attempting diagnosis of joint condi- tions we do so by means of the changes in one or more of these three parts. We may divide arthritic conditions into two classes. First, the acute, and, second, that large group which we may class as arthritis deformans. Under the first group would come the acute polyarticular rheumatism. This type comes nearer to being a distinct clinical entity than any of the other forms of this disease. The object of this article is not to deal with the clinical symptoms but with the x-ray findings ; consequently, we will confine ourselves entirely to the changes that can be seen upon a plate. In acute polyarticular arthritis the x-ray indications are rather indefinite. AYe find that there is an increased amount of fluid in the joint, and the synovial membrane and periarticular tissues are swollen. There is no de- struction of cartilage, as we can tell by the fact that the joint space is of normal width. The cartilage itself is not visible by means of the x-ray, so w^e have to judge its presence or absence by indirect evidence, namely, the width 340 U. S. ARMY X-RAY IMANUAL between the bony surfaces that compose the joint. Since, in this condition, there is no destruction of cartilage we may expect the joint to come back to its normal condi- tion, and, after the disease has subsided, the x-ray examina- tion will show an absolutely normal joint. When we take up conditions in rheumatoid affections we meet very considerable difficulties. The classifications of the various types under this head are very unsatis- factory, and then, too, these so-called chronic rheumatisms have so many names for the same condition. For example, we see the terms chronic rheumatism, arthritis deformans, rheumatoid arthritis, osteoarthritis and spondylitis used indiscriminately by different individuals and yet meaning the same condition. There is no classification which is ab- solutely satisfactory, but that adopted by Goldthwaite many years ago is, taken as a whole, probably the best. Of course, many men take exception to his classification and do not agree with it as a whole, but its simplicity and the great number of cases which can be classified accord- ing to it makes it seem generally the most useful. He di- vides the chronic arthritis into : 1. The infectious type. This includes tuberculosis, gonorrhea, syphilis, pneumococcic infection and those types of arthritis which have the same clinical manifesta- tions, but where the etiological factor is unknown. 2. Those cases designated as atrophic. 3. The hypertrophic cases. Infectious arthritis, from an x-ray standpoint, presents three different appearances, according to the stage of the disease at the time of examination. For example, in the first stage we have an acutely inflamed joint, and a marked amount of fluid present with periarticular swelling. There is no cartilaginous destruction and consequently no bone destruction. This stage gives the same x-ray appearance BONES AND JOINTS 341 as an acute polyarticular rheumatism or an injury to the joint without fractupe, because in these conditions we also get fluid, periarticular swelling and no cartilaginous changes. In the second stage the disease probably reaches its maximum intensity and, in time, the following changes take place in the joint and bone. In the first place, on account of the disuse of the joint, we begin to get a general- ized atrophy of the bone, the sw^elling has partially disap- peared and the fluid may be partially absorbed. The cartilage is now eroded, as shown by the fact that the joint space is narrowed, but there is no new bone forma- tion. The soft tissues may have even atrophied some- what. Occasionally we may see punched-out areas extend- ing through the cartilage down into the bone. In the third stage, or we may term it the stage of repair, the active infection has disappeared and the patient is beginning to use the joint, consequently, the atrophy is disappearing or will have completely disappeared. The soft tissues are resuming their normal appearance, and, where the cartilage has been destroyed, it is replaced by proliferation of new bone. In other words, w^e get the formation of bony exos- toses. The extent of these exostoses depends entirely upon the severity of the lesion, and in some cases cartilage has been so completely destroyed that we have a true bony anky- losis. This type of infection is seen in all ages of life, that is, from early adult life up to and through old age. Atrophic Arthritis. — Atrophic arthritis is generally seen in early middle age. There is marked atrophy of both soft tissues and bone. The joints are frequently par- tially subluxated, due to the contraction of the tendons, and there is limitation of motion; the latter is not due to bony ankylosis, however, but to fibrous changes and muscle contracture. The x-ray examination shows marked atrophy of the bone. There is extensive absorption of cartilage 342 U. S. ARMY X-RAY MANUAL and its complete destruction in certain areas, but there is apparently no attempt at new bone formation. From this description one can readily see that the atropic arthritis simulates very closely the second stage of infectious ar- thritis. The only differential point is that at no stage in this disease is there any fluid or periarticular swelling, while in the second stage of infectious arthritis one is apt to find a small remaining amount of swelling and fluid. Many clinicians think that atrophic arthritis is not a dis- tinct clinical entity but probably one of the stages in an infectious arthritis. Hypertrophic Arthritis. — Hypertrophic arthritis is a disease almost invariably associated with people of middle life and old age. One rarely sees this type under thirty- five and it is most pronounced in patients in the neighbor- hood of fifty and over. The x-ray examination shows that there is practically no atrophy, in fact, there is condensa- tion of bone so that the bone shadows are even a little denser than normal. When the age of forty-five is reached there is always a certain amount of atrophy in the bone, due to what might be called a senile change. This is com- pletely absent in the hypertrophic type. Besides the con- densation of bone there is a marked formation of exostoses, due to small areas of cartilaginous destruction and marked lipping at the edge of the articulating surfaces. Fre- quently little, bony, loose bodies may be present in the joint (joint mice). There may be ankylosis of the joint, but this is not a true bony ankylosis but simply one due to the mechanical locking of these bony exostoses. This type simulates the third stage or the stage of repair in an infectious arthritis. In hypertrophic arthritis, if the con- densation of bone is absent, it is extremely difficult and, at times, impossible to differentiate between the third stage BOXES AND JOINTS 343 of infectious arthritis and hypertrophic arthritis, particu- lar!}- if the patient is in the neighborhood of fifty. Great care must be taken not to confuse the slight ar- thritic changes which are always present in people over fifty with an acute active process. It has been definitely es- tablished that practically all of us wiien we reach the age of forty-five show small exostoses in and around the joints, and yet there may be no clinical manifestations of an arthritic process. It is particularly in these joints that we get such marked symptoms following a slight injury — symptoms out of proportion to the extent of the injury. In this condition we must remember that the injury has simply lowered the resistance of the joint and has allowed this quiescent arthritis to flare up into an active process, so that the marked clinical manifestations seen in such joints are really the result of the arthritis and not of the trauma. We have mentioned the subdivisions under infectious arthritis where the etiological factor is known. The ques- tion naturally arises, do any of these give such definite x-ray changes that we can actually determine the specific type of the infection with which we are dealing. Unfor- tunately, the majority of them give the same x-ray indi- cation. Some, however, give fairly constant appearances so that they can be readily recognized. In tuherculosis of the joint we have a marked hazing so that the x-ray shadows are very indistinct. In fact, it suggests that we have a very poor plate, but in this same plate one wall note that the bones adjacent to the affected joint come out sharply and distinctly. It is only the joint itself that is hazy and indistinct. This is due entirely to the thickening of the synovial membrane. Upon close in- spection we will find that the bone contour, that is, the bone beneath the cartilage, is very indistinct, irregular and 344 U. S. ARMY X-RAY MANUAL eaten out. In the active process fluid is present and there is marked periarticular thickening. When the disease sub- sides this haziness and indistinctness of the joint disap- pears, but we still have an irregular and eroded joint sur- face, indicating that there has been some destruction of cartilage and slight destruction of the bone beneath. There is very little tendency to new bone formation, and the ankylosis, if present, is generally fibrous in nature. Since these joints when untreated so frequently form sinuses, there is a great chance of having another infection besides the tuberculosis in the joint. It is in these mixed in- fections that we see the marked new bone formation. Gonorrheal arthritis does not give us distinct x-ray ap- pearances. It varies according to the severity of the lesion. In only one joint do we have fairly definite characteristics, namely, the knee joint. In that particular joint, for some reason, the greatest severity of the lesion seems to take place in the cartilages beneath the patella, and early bony ankylosis occurs. In a knee joint in which we find anky- losis between the patella and the femur gonorrheal arthritis must be borne in mind. Exostoses and ankylosis are quite common in this disease. Syphilitic arthritis shows marked periarticular swelling, thickening of the synovial membrane and fluid in the joint. This type does not go on to cartilaginous destruction, con- sequently, when the disease subsides we have a perfectly normal joint. The x-ray appearance is identically the same as that of an acute polyarticular rheumatism. Fortunately, this type is generally accompanied by bone change. While this change is not present in the joint itself at the same time it is fairly characteristic, namely, a small area of periostitis forming just at the point where the cartilage of the joint ceases and the periosteum of the bone begins. This periostitis in conjunction with periarticular swelling BONES AND JOINTS 345 and fluid in the joint is fairly characteristic of a syphilitic lesion. The Charcot Joint must not be confused with this acute syphilitic joint, since the changes in the former are neuro- pathic rather than infectious and are characterized by great destruction of the joint with splitting off of large fragments of bone, which lie free in a swollen joint filled more or less with fluid. In addition, there is marked eburnation of the remaining ends of the bones. Upon glancing at such a joint one is struck by the marked de- gree of disorganization that it has undergone and instinc- tively feels that such a joint could not possibly be used. On the other hand, there is absolutely no atrophy of the bones, indicating that the joint has not been at rest. Joints which undergo any degree of disorganization are always extremely painful and remain at rest. They consequently show marked atrophy, so that when one sees a markedly disorganized joint without any atrophy of the bone at all one should seriously consider the possibility that the con- dition is not an ordinary infection but a Charcot joint. Occasionally, but not frequently, one runs across a joint giving the clinical symptoms of an infectious arthritis, but the x-ray examination shows a rather remarkable condition. There is marked destruction of the cartilage of the joint, slight new bone formation, and a hazy joint, simulating tuberculosis ; but in the joint cavity itself there is a blood clot which has undergone either fibrous or bony change. When such a condition is present it is invariably the result of hemophilia. The remaining forms of infectious arthritis do not give any definite x-ray appearances. The object of this chapter is to give a rough classification. In joint diseases, as in other conditions, the clinical aspect of the case must be taken into consideration in order to arrive at a diagnosis. SINUSES AND MASTOIDS Technique for Mastoids. — It is necessary to make an examination of both mastoids. Tliis may be done on one 8 by 10 plate, by covering one-half of the plate with a thick piece of lead and making one exposure on the un- covered portion, then changing the lead cover to the exposed side and making the second exposure on the side which had previously been covered. It is necessary to compare one mastoid with the other, and placing both on the one plate makes comparison of the two sides much easier than if separate plates are made. The patient lies on a table with the head on a small raised platform, the affected ear next to the plate with the pinna folded forward. There should be a clamp on the platform with adjustable pads to press on the occiput and forehead, but not so as to obstruct a clear view of the mastoid cells. The head is placed so that the sagittal plane will be parallel to the plate. The tube is centered over the head in such a way as to direct the central ray down- wards and forwards toward the opposite ear. An angle of fifteen degrees from behind forward towards the face and fifteen degrees from above downward towards the feet will in the majority of cases be correct. In case the shape of the head is such that the sagittal plane cannot be placed parallel with the plate, without raising the mastoid area above the plate, the angle of the tube must be altered to accommodate it. The central ray should enter the head above and behind the external auditory canal, and emerge at the external auditory meatus next to the platCv 346 SINUSES AND :\rASTOIl)S 347 fee OS cp s o o ~ I—i — cS ho 348 U. S. ARMY X-RAY MANUAL The tube stand should be supplied with a small cone and this brought down with firm pressure on the head. Stereoscopic plates may be made by shifting and tilting the proper distance on each side of the angle. Figs. 153 and 154. Technique for Accessory Sinuses. — In order to obtain a satisfactory postero-anterior image of all the accessory sinuses at one exposure, it is necessary that the rays pass through the head at a certain angle. If this angle is not observed, the petrous portion of the temporal bone obstructs the view of the ethmoids or antrum, or the sinuses are so distorted that the information given is not correct. The proper angle is one which will cause the shadow of the petrous portion to cut across the lower one-third of the orbit and upper one-third of the antrum, leaving the lower two-thirds of the antrum free and also the upper two-thirds of the orbit clear. Fig. 155. The superior portion of the antrum is not so important, as any condition affecting the antrum to the extent of an x-ray diagnosis will involve the inferior portion as well. The possible exception to this is in the case of a fracture involving the lower orbital margin. In this ease the petrous portion must be thrown down into the antrum, or a plate must be made in the vertical position. The position described shows clearly all that is re- quired of the frontals, ethmoids, and antra on a single plate, and the sinuses in their proper relation and size. To obtain this position the principal ray must be directed through the head at an angle of twenty-three degrees from a line extending from the external auditory meatus to the glabella. This angle may be obtained by a pair of dividers or a permanent triangle set at an angle of twenty-three degrees. Fig. 156. SINUSES AND MASTOIDS 349 Fig. 155. Schematic dravv-ing illustrating correct angle for pos- teroanterior accessory sinus examination. The heavy lines indicat- ing projection of petrous portion of temporal bone on to the plate. A, antrum; E, ethmoids; F, frontal; P, petrous; 0, orbit. 350 U. S. ARMY X-RAY IMANUAL The patient is seated before an adjustable stand, or may lie prone on a table. The head rests face downward with the nose and forehead on an inclined plane. The inclina- tion is such as to be comfortable to the patient. The head- FiG. 156. Position for postero-anterior examination of accessory sinuses, head resting on nose and forehead, central ray entering head at angle of 23° from a line from external auditory meatus to glabella. rest shown in the illustration has an angle of twenty degrees. If the patient is sitting, an adjustable rest is necessary to accommodate for the difference in the length of the neck and shape of the head. The tip of the angle finder is placed opposite the glabella, the short arm passing across the external auditory meatus, the long arm extending upwards alongside the cone and SINUSES AND MASTOIDS 351 C3 O '-3 2 ^ '-t^ — , ^ O o o ■^ 'BP 00 -J &€ rt c5 352 U. S. ARMY X-RAY MANUAL representing the direction of the principal ray. The cone is now brought into alignment with the arm of the finder and brought down on the head, making firm pressure. For lateral plates the patient places the side of the head on the platform holder, the head is leveled so that the sagittal plane is parallel to the plate and the tube is centered so that the principal ray passes directly through the frontal sinus. This is to obtain a true representation of the depth of the sinus and the thickness of the anterior wall. The head is clamped firmly in place. Figs. 157 and 158. For vertical examination there are two positions which will give satisfactory views of the sphenoid sinus and the adjoining structure. One, with the patient on his back and the head extended over the table, has been described in another chapter (page 310). The other is obtained by having the patient sit in front of an adjustable stand. The height and angle of the stand is adjusted to suit the height of the patient and to make him comfortable. The chin is extended as far as possible and placed on the plate which rests on the stand. The stand is also adjusted at such an angle that the plate rests against the clavicle. This places the entire neck on the plate, from the point of the chin to the clavicle. The head is leveled and fastened securely in place with clamps. The tube is adjusted over the vertex and centered so that the principal ray passes downwards and backwards through the sphenoids. A straight edge placed alongside the head and passing through the sphenoid and center of the cone will show the point on the plate where the shadow of the sphenoid will be thrown. This must be at a point well posterior to the point of the jaw, but not so far back as to throw the sphenoid completely into the shadow of the larynx. If the sphenoid shadow is thrown at the level SINUSES AND MASTOIDS 353 of the angle of the jaw a good view of the ethmoid and sphenoid regions will be secured, Fig. 159. Fig. 159. Position for examination of sphenoid sinus. Chin rest- ing on plate and extended well forward on plate. The height of table adjusted so that clavicle touches plate, thus bringing entire neck parallel with plate, tube centered over vertex so that central ray will project shadow of sphenoid on plate at about the angle of the jaw. Interpretation of Mastoid Plates. — In case the pinna cannot be folded forward, due allowance must be made for the increased density over the mastoid cells caused by the shadow of the pinna. Postauricular edema will cause a haze over the cells, which must not be mistaken for in- 354 U. S. ARJMY X-RAY MANUAL flammatory exudate. Inspection of the ear before radio- graphic examination will prevent this error, as allowance may be made for the increased density. Furunculosis in the canal is often accompanied by a slight cloudiness of the cells, which must not be mistaken for exudate. The mastoid, being a pneumatic cavity, will show nor- mally as a honeycombed structure with the cell partitions clearly outlined, so that the degree of the involvement will be determined by the sharpness of these partitions. A sim- ple congestion or thin fluid will produce a general haze over the mastoid structure, but the cell walls will be clearly outlined. As the disease progresses and pus accumulates, the degree of obliteration of the cell walls will determine the extent of the disease or the amount of pus. If the con- dition has reached the point of bone destruction the ne- crotic area will show through the white blur of the cell involvement as a dark area. This usually occurs over the line of the tegmen tympani, representing an epidural ab- scess, or over and below the knee of the lateral sinus as a perisinus abscess. This dark area must be distinguished from a large cell in the midst of a group of small cells. This can usually be done by comparison with the opposite mastoid. As a rule the two mastoids are similar in structure. When there is a large or small cell on one side there is usually a cor- responding cell on the opposite side. Then, too, a necrotic area will have hazy edges while a clear cell will be sharply outlined. Complete obliteration of the cell area must be differen- tiated from sclerosis. This is a condition caused by re- placement of the cell structure by dense bone, and the shadow on the plate will therefore be structureless. The area resembles the bone in the rest of the skull, with a clear-cut outline of the sinus showing through. This proc- SINUSES AND MASTOIDS 355 ess can be so extensive as to involve the entire area in- cluding' the region of the antrum, thus showing no detail at any point. A condition may arise in which necrosis has occurred in the sclerotic area, a cholesteotoma. This will show as a dark spot within the sclerotic area. Usually there is a lighter area in the dark portion which represents a mass of debris in the necrotic cavity. In the event of a fracture or injury extending through the mastoid structure stereoplates are necessary. These cases nearly always show mastoid change due to the pres- ence of blood or infected material. In the event of the involvement of both mastoids de- pendence must be placed on the history and clinical evi- dence. The size of the cells plays an important part in the prognosis. A large pneumatic mastoid with large antrum cells is more likely to clear up without operation than one with small cells, as the smaller cells are more apt to clog and stop drainage. ]\Iany cases which have been operated and have not properly cleared up will reveal cells remaining in the mastoid process. These contain granulations which keep up the discharge and prevent healing. In the case of children, it must be remembered that the mastoid cells do not develop until about the age of five years, so that an examination of a child under this age wall give no useful information. Interpretation of Accessory Sinuses. — Here, as in mas- toids, there are pneumatic cavities which in a normal con- dition allow the rays to penetrate readily and produce dark areas on the plate. AVhen pathological material is present the transparency^ is reduced, depending on the extent of the involvement. 856 U. S. ARMY X-RAY MANUAL In the examination of the frontal sinuses a very impor- tant factor to be considered is the depth of the sinus and the thickness of the anterior wall, as viewed on the lateral plate. A sinus with a thick wall will naturally show less transparency than the same sinus with a thin wall. Hence a sinus with a thin wall and containing granulations or thin pus will cast the same transparency as the same sized sinus with a thick wall but clear of pathological material. A deep sinus will normally be more transparent than a shal- low sinus. One must remember that one or both frontal sinuses may be absent. In the case of absence of frontal sinuses, the lateral plate will reveal solid bony detail in the frontal region, while a single frontal will reveal bony detail through the transparent area of the sinus which is present. If both are present a clear area will show on the lateral plate. It is impossible to distinguish between the shadow cast by pus or by dense granulations in the sinuses. The diag- nosis must be made of occlusion of the sinuses by some dense material. The case history will help to a great extent. The ethmoid region must be studied in both the antero- posterior and lateral positions, — the diagnosis resting on the density of the region and the degree of obliteration of the septa. Plates made in the vertical position will indi- cate the affected side and show whether the anterior or posterior cells are involved. The ethmoid cells are sometimes very extensive and show above, behind and below the orbit. In the examination of the maxillary antrum the degree of obliteration of the fine lines of the walls determines the amount of involve- ment, although mucoid material will cause practically no change in the shadow. It may be necessary to puncture the antrum through the nose to clear up the diagnosis between granulations and pus. ix^tf^ TEETH AND MAXILLAE In the study of the teeth dental fihns are more satisfac- tory than plates. Accompanying illustrations will describe the proper adjustments of tube and films or plates. Plates are used when the films cannot be put into the mouth, or when a large area is required to be shown. Placing the Film. — Observe the following hints in placing the films in the mouth. All sharp corners of the wax paper covering must be folded over and softened, and the films themselves will become more soft and pliable by bending (not breaking) them over the end of the finger and thumb so that they will take the curve of the palate or inner surface of the mandible more readily. To pr e- vent gagging, the patient is told to breathe_deeply through the mouth,.wliile_the film is being placed in position. This "^ causes the tongue to be carried far back into the pharynx where it need not be pressed upon. In very troublesome cases s;Q rayin g the galate and pharynx with^camphor wa- ter, in addition to the above precaution, adds greatly to the chance of succe ss. Be sure that the film is far enough into the mouth to include all of the root structure. The position of the film should be carefully noted after the patient's thumb or forefinger is in place to hold the film, since the wax paper moves_ easily on a s urfac e wet with mucus^ and the patient's hold may relax as the operator removes his hand. For the upper teeth no additional ^ . covering over the wax paper is necessary or even desirable, ^2!« and there is no better film holder than the patient 's ,left 1 ;humb for the upper teeth on the right side, and the right 358 U. S. ARMY X-RAY MANUAL TEETH AND MAXILLA 359 y5 « O Jii^ aj =4-1 c3 fn o3 ° ^ rt o 'S E-t 'o >^ (D CQ o , °^s 360 U. S. AR:\IY X-RAY MANUAL ^ o en o Ph cu ri3 bJD Itl O) )-4 O ^ i> So '-' o a Oi ;-( ^H OJ q; r-^ ^ «j tn *M o s s ^ tn •^ o « o 2 O) a; S ■^ ^ -^j o m ^ ^ ^ C^ rr^ a £ ^ Qi ^ rt o ^ •iH rt i» M PJ O O o be as S 4-i 'o ^ ^ X q; o 'o 1) >; -i3 0) Xtl > 13 O IS 'V QJ rH CD ,£3 (P -4-i -M O .G -t^ -M f_f O C3 -(-5 T— i =4-1 s o +2 o u O o 93 P^ o ^ ^ ■^ rC QJ o «o -4-5 rP GO 1—1 qn S X2 03 ^ O J3 d fl 4^ -*-5 pC s a; 5 g e Ik TEETH AND MAXILLA 361 362 U. S. AR]MY X-RAY MANUAL ^T^r ^^^^^ m ^ 1 ^^|j m^ Fig. 166. Sarcoma of mandible involving median incisors and left lateral incisor, probably also beginning involvement of the other teeth shovm. Fig. 167. Acute abscess right upper central and lateral incisors. Note that abscess is not sharply defined. Acute abscesses sometimes do not cast definite shadows. TEETH AND MAXILL.E 363 364 U. S. ARMY X-RAY MANUAL TEETH AND :\rxVXILL.^ 3G5 thumb for those on the left side. The pressure of the thumb must be firm, and the fingers should rest on the opposite side of the face to prevent unintentional motion of the liand. Iii^ll instances the o perato r mu st mold th e ^1^^^ '^-t^/A,^ to the contour^ of the m axilla3 and d enote b}^ the firmness Z;^^^^ ^ of his own pressure how the patient shajl h old i t. ^j^'CCSt^jt For the lower jaw the films should be wrapped in soft tissue paper, such as a paper napkin. This prevents slip- ping and is also more comfortable to the patient. It is X^-t^**^ a bsolut ely essential that the pa tient 's ^ tongue be completely "^^-^A-ite* relaxed in _order tliat ^ the film ma3^ be c arried b ack far "Ln zV«^ enough to^reach well^beyond tl ie third molar, anddeep eliough to reach_j\vell below the apices of the ro ots. Th e palmai' surface of the jjide^^nger of the_opposite_h and is preferred for holding the films agains^the^lowerjteetlL Exposure. — The patient should hold his breath during '7^ o t he actua l exposure whether it is for one second or twenty ^o^^XjS seconds. ^ ^ -CLi^^.^ J^^ The proper an^giejof exposure n iust be det ermin ed by the ' contojir_of the patient^s^maxill^^ and the tooth shadow mjj'f^ should be approximately the same length as_the tooth. f it^^ For angle of exposure see Figs. 160-163. ^ Interpretation. — The x-ray study of the teeth and max- illae is to be considered from the viewpoint of dentistry without injury, and as Avell from the viewpoint of wounds incident to war and, therefore, of surgery. The former has more to do with the general health and efficiency of the soldier, while the latter involves the repair and restoration of these very important parts after injury. The reader is advised to acquaint himself with the structural and regional anatomy of the teeth and max- illae, and also to study some recognized authority on the pathology of these structures. The accompanying illus- trations show practically all of the types of pathological 366 U. S. ARMY X-RAY MANUAL m Fig. 170. Abscesses involving unerupted teeth. Fig. 171. Adjustment for exposure of anterior portion of upper jaw. Note large film held between the teeth. The teeth shadows will be very much foreshortened. TEETH AND MAXILLA 367 ^ o CO o — o -; CO i, — . -t-" - £; o c '^ :^ -^ .2 a- o% bx ;f i g - op OD ^ s ^ O O •1—3 J- .^ _>J o O) o c3 +3 S m S Fh O • -H ^ r; ^H +J -1-3 3 -w ri O fl a ^ V) o «« X! (11 bJD O rt «f-, ,_4 +i -M Si ^ -M f/l ^ ''~^ •^ < c3 fl O^ ^ L^ ^H C rto ^ -^j UL4 ^1 & 368 U. S. ARMY X-RAY MANUAL lesions about which we are herein concerned, except in- juries. Figs. 164 to 170. It is difficult to anticipate the sort of injuries one has to deal with in military surgery, and therefore difficult to give definite instruction in the part taken by the roent- FiG. 174. Adjustment for exposure of upper jaw. genologist. The following illustrations serve to show the proper adjustments for the different parts of the jaw bones, and may be taken as guides in most instances. The object is to have the central rays pass in such a direction that the shadows of the teeth on the near side of the face will not fall in the area that is to be examined. Figs. 171 to 174. THORACIC VISCERA Methods of Examination. — The thoracic viscera may be studied either by tluoroseopy or by radiography. Fluoros- copy is useful for a preliminary orientation, to view the movement of the diaphragm, to study the movement of fluid levels in the pleura and in the lung and to observe the mediastinum in the various oblique positions. It is indispensable in the x-ray study of heart and aortic con- ditions. It is of uncertain value in the recognition of infiltration in the lung as in tuberculosis. For this purpose a plate examination is indispensable. Stereoscopic plates are of value to indicate the depth of a pulmonary lesion ; they will diiferentiate between pul- monary and pleural or extrapulmonary conditions. In tuberculosis, especially, they resolve the shadows into their components and, thus, give a truer idea of the density of the infiltration. Stereoscopy can, however, usually be dis- pensed with, as the data it furnishes does not materially differ in character from that found in a good single plate. A moi'e potent reason for dispensing with it in army work is the additional time and trouble involved and the diffi- culty of obtaining large plates in sufficient number. Time. — The time of a single exposure shoulcj not exceed two seconds. If the current is not sufficient to obtain a proper exposure in that time, the use of an intensifying screen, w^hich must be as nearly perfect and free from grain as possible, is advised. Exposures of less than a second are desirable, but at the present time they are not easily accomplished in the routine work of large hospital 369 370 U. S. ARMY X-RAY MANUAL fj OT O I ;-. Q t-l o ,£2 13 •4^ -2 H fcJO ■^ PH 0) 1"> 13 . r^ -»-> n -|J n n3 -M -P M rt ^ o n ft -M OJ crt QJ n3 CT' •4-^ oa r— H !=l r" a;i ^ O CD ft P=H O ft 73 O ft ■73 ft o T— 1 CO n^ • ^ O) o ^ ^ M 1— 1 o 0; ;x^ '^ O CD t> O THORACIC VISCERA 371 Otj Qi en 02 O .2 ^ +i o =c-g.2^ o 3 S"S o fl S 02 OS ^ 13 IT) Si OS o I-:] ^ «H o 0) O a 3 r-i a m © o 71 X2 •— ^ 3 ,^ -(-3 cr at ^ ^ •" 'A ^ •+J '•$. o j; O o -tJ .""" 4-" o .1-1 cs ^ a OS ■^ =M h o o 1-