Contents

214

SECTION I

GENERAL SURGERY

CHAPTER VIII

LOCALIZATION AND EXTRACTION OF FOREIGN BODIES UNDER X-RAY CONTROL

LOCALIZATION

EARLY HISTORY AND LITERATURE
In reviewing the methods of localizing foreign bodies, one is immediately impressed with the fact that the publications of the year 1896 set forth the principles at the foundation of most of the localizing methods of today. This year saw the publication of Buguet and Gascar,¹ setting forth the classical formula:

Depth equals FORMULA when a represents the distance the tube is shifted: b the distance of shift of the shadow of the projectile; and h the height of the screen or plate from the focus of the tube. Early in this same year Thompson,² in America, and Imbert and Bertin,³ in France, proposed stereoscopy in connection with X-ray localization. The method of making two exposures at right angles, the so-called method of right-angled planes, was proposed by White, Goodspeed, and Leonard.⁴
The following year marked the publication of Mackenzie Davidson and Hedley,⁵ on the triangulation method, visualizing in space the position of the foreign body by means of crossed threads, and the method of Gerard ⁶ and Levy-Dorn⁷ which utilized the same principle of triangulation, but without the cross-thread visualization. Stechow wrote further on the method of making two exposures at right angles.⁸ Exner described a method combining a ring localizer with the triangulation principle, and later used the parallax principle.⁹ The parallax principle was also used by Levy-Dorn.⁷ Rémy and Contremoulins¹⁰ described an elaborate apparatus which was apparently the forerunner of the Hertz compass as used today.
In 1898, in addition to other methods, Marize used four small adhesive disks of lead;¹¹ two be placed at the points on the skin where the vertical ray passing through the foreign body entered and left the part; the other two were placed in a similar manner at right angles (or nearly so) to the plane of the first two. The intersection of the two diameters joining these four points gives the location of the foreign body.
Galeazzi ¹² was apparently the first to publish description of the “pierced screen” the ordinary fluoroscopic screen with a small hole drilled through it and the lead glass cover, sufficiently large for the insertion of a small rod for estimating the depth from the screen surface to the skin in those locations where it was not possible to bring the screen in actual contact with the part understudy. He also employed the triangulation method with single tube shift, and added a direct-reading scale, obviating the necessity of calculations.

215

Sechehaye,¹³ in January of this year, published a review of the literature on the subject and was able to summarize 32 methods and authors.

The writer, in 1918, published a brief history of the development of foreign body localization by means of the X rays, with a bibliography containing more than 200 references.¹⁴        
The more than 200 methods referred to in this review were really susceptible of classification under a few of the methods described in the first two years of the roentgen era. Few of the methods later published were anything more than rediscoveries or minor modifications of essential principles already discussed and used.

The Hertz compass, though first used in 1907, was not referred to in literature until 1914.¹⁵ Telephone probes and other localizers working on the magnet principle were innovations appearing shortly before the opening of hostilities in 1914.¹⁶ The most complete work on the subject of foreign body localization was written by Ombredanne and Ledoux-Lebardc.¹⁷ Delherm and Rousset,¹⁸ and Nogier ¹⁹ also wrote booklets on the subject.

The United States Army X-ray Manual was finally adopted as the working manual of the United States Army Medical Department, and in it a large section was given over to localizations.²⁰ An effort was made to select the more valuable methods and to standardize the necessary instruments and the technique for their operation under the methods selected. It was exceedingly difficult for those who had not actually participated in forward area surgery under battle conditions to realize how simple, direct, and quick the localizing methods had to be. It was soon recognized that any method involving the use of plate or film records was unsuitable because of the time and labor necessary to make the localization, and it soon transpired that the medical officers actually doing localization work in forward hospitals exhibited a marked tendency to employ very simple methods capable of being used without accessory instruments other than the fluoroscopic apparatus itself.

METHODS

Though civil surgery affords relatively infrequent opportunity for the surgeon or the radiologist to put to actual test the methods of localization which are to be found in every textbook on radiology, the World War afforded an extraordinary multiplicity of occasions for studying foreign body cases, and enforced a careful analysis and modification of the more than 200 procedures which were described in the medical press early in the war.

Some of the procedures described are complex, some are simple; some require complicated apparatus or special instruments, while others may be carried out with any of the ordinary types of X-ray equipment; some required the aid of radiographic plates, while others are screen methods quickly performed and affording an instant answer to the surgeon's query as to the presence or situation of the offending foreign substance. Out of the war have arisen systematized localizing procedures, with standardized apparatus especially adapted to the expeditious handling of large numbers of wounded men. Some of the standardized types of apparatus developed for military work are already being used in our civil hospitals, and the general trend of manufacture

216

of X-ray equipment is toward the simpler instruments developed during the war.

It is the purpose to set forth briefly herein only those methods most readily learned and carried out with a minimum of accessory instruments. Explanations of geometrical propositions, for lack of space, are reduced to a minimum. Any reader interested in the details of such mathematical propositions will find discussions in the various excellent treatises on localization which have been prepared by the medical departments of the various allied armies, already referred to.

Magnets, vibrators, and telephone probes have been variously recommended by military surgeons but they are limited in their usefulness. Magnets, for instance, are applicable only to the localization and extraction of such metallic foreign bodies as are responsive to magnetic attraction, whereas the radiologic method should discover all metallic foreign bodies (with the possible exception of aluminum), besides many nonmetallic substances. The radiologic method as a part of the surgical procedure lends itself admirably to helping the surgeon during the extraction of any foreign body, whereas the magnet and vibrator methods above referred to have the same limitations in respect to nonmagnetizable substances.

The person undertaking a localization should not confine himself to an estimation of the depth of the foreign body, but should acquire all possible information afforded by an X-ray study of the case. For the best results it is essential that the radiologic work be done by a physician, or, better still, the surgeon should be familiar with the radiologic procedures involved in foreign body localization; indeed, there is such temptation for the surgeon himself to go ahead with the radiologic part of the extraction procedures that unless he has a thorough technical knowledge of the subject he is likely to harm himself through inadvertent overexposure to the rays. These dangers will not be discussed here as they are fully described in numerous textbooks.

Localizations are usually accomplished by fluoroscopic methods, although there is no objection to radiographic methods other than that they involve more time and expense and are not so informing as the screen methods. Stereoscopic radiograms are more valuable than single plates.        
A localization should afford the following information: (1) Anatomical data, showing the relation of the foreign body to neighboring structures, such as a trochanter, a condyle, or some other well-known bony point, to a muscle; or to an artificial opaque marker affixed to the skin. The condition of any injured hones should be carefully recorded. (2) Mathematical data as to the depth of the foreign body in relation to marks or markers on the skin. (3) Directions which will guide the surgeon to the foreign body.  This guidance is frequently afforded by the fluoroscope through observations made during the removal of the foreign body.
           
The following localizing methods are considered herein: (1) Rotation of the part; study of the movements of the shadows of the projectile or other foreign body in relation to neighboring opaque structures or skin markers. (2) The “nearest point" method. (3) The parallax method, which is often combined with the nearest point method. (4) The orthodiagraphic method, which is

217

also often combined with the nearest point method. (5) The method of right-angled planes (four-point survey). (6) The multiple diameters method.(7) The single-shift triangulation method, with which may be included the stereoscopic method. (8) The double-shift fixed-angle methods. (9) Harpooning methods, combined with reconstruction of the part by the aid of a cross-section anatomical atlas.

There are numerous other methods which might be described, but these mentioned above are all very simple, easily learned, quickly performed, and accurate to within a half centimeter, without the aid of plates. There is no reason why one or more radiograms of the part should not be made if the surgeon so desires, especially if he has not been present at the X-ray localization. If such plates are made, they should be stereoscopic plates.

APPARATUS REQUIRED

In addition to the usual current-generating apparatus of any type supplying at milliampere or more, a tube of sufficient hardness and a horizontal ^a or vertical fluoroscope installed in a room capable of being completely darkened, the following items of equipment are necessary: A ruler; a localizing rod or wooden stick the size and length of an ordinary lead pencil, with a metal ring, approximately 2 cm. in diameter, screwed into one end, and an ordinary screw with a

FIG. 109.- Palpator made from a small wooden rod, with a screw and a screw eye

well-rounded head in the other; grease pencils, such as are used for marking on glass or chinaware; suitable skin-marking ink; an aniline dye may be used, or the Finzi ink; ^b a cross-section anatomy, that published for Professor Symington, being highly satisfactory.²¹

The foregoing accessory articles permit the performance of most of the localizing procedures listed and described in this article, but the following inexpensive and simple accessories are often very useful: Large calipers, such as obstetrical calipers; a foot-switch for controlling the current through the X-ray tube; better still, a combination switch, controlling both the overhead light and the tube current; strips of flexible metal, such as composition tin, 1.5

 ^a 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 provided with a double shutter giving a diamond-shaped opening 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 carriage mounted on the table rails, and provision is made for a movement parallel to the table, for rotation about a vertical 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 horizontal 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 fixing in position the scales and other pieces of apparatus which it is desired to use on the fluoroscopic screen.
^bThe writer prefers an ordinary indelible pencil which makes a semipermanent mark on the moistened skin. For war surgery the indelible pencil would hardly satisfy the need, but in civil practice it will usually do very well.

218

or 2 cm. in width, and of appropriate lengths for surrounding an arm, a leg, or the torso, and hinged together in pairs; a cannula and trocar, and a supply of fine piano wire cut into lengths somewhat longer than the trocar.

CENTERING THE TUBE

Accuracy in localization work requires an exactly centered X-ray tube. Some of the French manufacturers supply a special device for centering the tube. Among the numerous groups of rays given off in the active hemisphere of an X-ray tube is one to which the term "normal ray" has been applied. It will be recalled that in geometry a line normal to a second line is one perpendicular to it, making with it two right angles. In radiology, therefore, the term

FIG. 110.- Showing the positions of shadow of plumb bob on fluorescent screen when X-ray tube is properly centered, and when off center

normal ray is applied to that group of rays perpendicular to the long axis of the tube. Unless the tube is carefully centered beneath the diaphragm in such a way that when the diaphragm is closed down to a small opening the normal ray will pass through it, there will be a resulting error in the localization calculations.

One may determine when the tube is centered by the following means: When the military type of table is not available, the screen is locked in position above the tube box and a plumb bob attached to a metal marker, such as a lead ball, is affixed by adhesive plaster to the underside of the screen somewhere near its center (fig. 110). The opening in the diaphragm is reduced to about 1 cm. and the tube box moved until the pencil of rays emitted through the small opening casts the shadow of the plumb bob and the metal marker on

219

the screen. If the two shadows do not coincide, the tube is not correctly centered, and alterations in its position should be made and compared until the two shadows coincide.

An ordinary tin cup or a glass tumbler may be placed accurately over the small opening in the diaphragm, care being taken to see that the cup or tumbler is on a level support, and that the opening in the diaphragm comes as near as possible to the center of the cup. Then the diaphragm is opened so that the shadow of the whole cup shows. One may judge by the symmetry of this shadow whether or not the tube is properly centered (fig. 111).

With the table supplied by the United States Government during the war, the diamond-shaped opening of the shutter is reduced to about 1 cm. The tube box is locked in position and the screen moved so that the perforation in its center will coincide with the center of the projection of the small

FIG. 111.- Screen appearance of a tumbler with the tube properly centered and not properly centered

diagonal opening of the shutter. The carrier is locked against longitudinal motion and against rotation, and the screen raised by the vertical movement of the carrier. If the perforation does not retain its symmetrical position the tube needs shifting until this condition obtains.

It is important that this process of centering the tube be carried out each time a localization is attempted, unless a number of localizations are planned for the same day.

MARKING THE SKIN

For marking the skin in relation to foreign bodies, especially where there is only occasional need for localization work, the ordinary indelible pencil, dipped in water or used on the moistened skin, is quite satisfactory. This mark is not obliterated by painting the skin with tincture of iodine. If a black mark is desired, which dries quickly and which will withstand scrubbing, the Finzi formula is useful: Pyrogallic acid, 1 gm.; acetone, 10 c.c.; liquid chloride of iron, 4 c.c.; wood alcohol q. s. ad., 20 c.c.

This ink, when made up fresh about once in 10 days, makes a black mark and dries quickly. It is best applied with a sharp stick or a fine brush. If allowed to dry thoroughly the mark will resist alcohol, show through an iodine stain, and persist from two to seven days.

220

In emergency cases a persisting mark can be made with a stick of silver nitrate on the skin moistened with a few drops of photographic developer. A match or toothpick dipped in a 10 or 20 percent solution of silver nitrate will serve the same purpose without the irritation of the skin which sometimes results from the use of the silver nitrate stick. An aqueous solution of brilliant green has also been suggested for marking the skin.

The method of marking will vary with the case. If multiple foreign bodies are present, it is sufficient to mark such of them as can be located by the " nearest point" method with a dot surrounded by a circle, the dot indicating the nearest point. In cases of a single foreign body it is well to make as many marks as may be helpful to the surgeon; for instance, one mark perpendicularly over the foreign body recording its depth, with two horizontal marks on either side of the part in the plane in which the foreign body lies.

It is also highly important that the localization be carried out and the marks placed upon the skin in the position which the patient is likely to occupy while undergoing operation. Hence, when it is feasible, the surgeon or his assistant should be consulted as to the probable method and site of surgical approach. It should be stated as an axiom that in all localization work the patient should be carefully placed in the operative position before one begins to make the localizing marks.

TECHNIQUE

One of the first steps in the localization of a foreign body, after determining its presence, is an estimation of its approximate position--whether it lies in front of or behind a certain bone or other anatomical landmark, whether it lies within the substances of a great muscle, etc. This is termed the anatomical localization, and it often suffices to enable the surgeon to perform the extraction.

Extraction of the foreign body is often one of the lesser considerations in dealing with a gunshot or other emergency case. The proper toilet of the wound, the removal of clothing and other foreign materials which may be carried into the part by the projectile or foreign body, as well as attention to damaged bone, nerve, or other tissue, are of paramount importance, and in many instances the extraction of the offending foreign body comes in for secondary consideration. Along with the data for localization the radiologist should supply all information possible regarding injury to bone, dislocations, blood or pus accumulations, gas infections, and other conditions relating to the wound.

ANATOMICAL LOCALIZATION

From the surgical standpoint, it may be stated that it is more important for the surgeon to be informed of the anatomical situation of a foreign body than of the mathematical distance it lies perpendicularly below a given point on the skin. For example, the surgeon is more interested in knowing that a foreign body has penetrated the pleura than that it lies 4.5 cm. below a certain point on the back when the patient is lying prone; and whether a projectile recorded as being 7 cm. beneath a point just below the vertebra prominens is intrapleural or lies within the substance of the body of the last cervical or the first dorsal vertebra. In order to give this information it is essential that the

221

radiologist should possess an accurate knowledge of anatomy. It is here that the cross-section anatomies may lend considerable aid, though sometimes anatomical conditions vary in individual cases on account of unusual accumulations of fat and because of varying build in different individuals.

The anatomical location can often be determined by requiring the patient to carry out some active movements, or the radiologist can himself move the part and observe the changing relations of the foreign body during these maneuvers. The movements of the shadow during the contraction of muscular masses are significant. For instance, a foreign body in the forearm which exhibits considerable displacement when the patient closes his fist manifestly lies in one of the flexor muscles; if it ascends on flexion of the thumb and remains stationary during movements of the other fingers, it obviously lies in the flexor muscle of the thumb.

Foreign bodies in the region of the eye may be more exactly localized by causing the patient to open and close the eyes, to rotate the eyeball, and to carry out other movements which bring into play the individual eye muscles. A method of localization of foreign bodies in the eye will be considered later in this discussion. By having the patient protrude the tongue, open and shut the mouth, perform movements of deglutition, swallow a capsule containing bismuth, etc., one is able to determine the relative anatomical position of a foreign body in the face or neck.

For differentiation between intra-and extra-thoracic foreign bodies, it is usually sufficient to cause the patient to practice several deep inhalations and exhalations. During inspiration the lung is displaced from above downward, while the thoracic cage is displaced in a contrary sense. Lateral or oblique fluoroscopy of the chest is very important, especially when the patient's diaphragm is immovable. Unless rather definite and extensive movement of a foreign body in the lower half of the chest can be determined during respiratory movements (save when the diaphragm is motionless), it should not be considered to be intrapulmonary: in the upper part of the thorax intrapulmonary foreign bodies may exhibit very little respiratory movement, and in the middle of the lung on either side they may be quite stationary. As intrapulmonary and hilus calcifications have caused many errors in the study of intrathoracic foreign bodies, it is well to have stereoscopic plates made in all doubtful cases. The pulsation imparted to intrathoracic foreign bodies by the heart or great vessels, especially to those lying near the midline, may occasionally cause great difficulty in exact localization.

Foreign bodies lying within the pericardium are usually movable and gravitate to the most dependent point possible when the patient changes his position; in old cases, intrapericardial foreign bodies may be attached to the wall of the pericardium and render the diagnosis more difficult.

Projectiles lying near the diaphragm, but just above it, should be easily localized, provided one views the patient from a sufficient number of angles. Intraabdominal, subdiaphragmatic foreign bodies are not so easily localized, Stein and Stewart ²² have recommended the introduction of oxygen or some other gas into the peritoneal cavity, so that by changing the posture of the patient it is possible to separate the subdiaphragmatic structures from the

222

diaphragm itself. Many cases of wounds with intraabdominal projectiles will have developed sufficient gas in the peritoneal cavity to make the introduction of oxygen unnecessary. Careful palpation of the abdomen, inflation of the colon or stomach in selected cases, the use of the Trendelenburg position, etc., will usually be sufficient without an induced pneumoperitoneum. Viallet and Tanton²³ have called attention to the possibility in certain cases, especially in wounds of the urinary bladder, of localizing a foreign body inside a hollow organ if, by localizing alternately from the anterior and the posterior aspect of the torso, results are obtained which disagree as regards the total thickness of the subject and are notably less. This is due to the displacement of the projectile from one position to the other.

In considering foreign bodies in relation to the vertebral column, attention should be drawn to the great value of stereoscopic plates and to lateral radioscopy

FIG. 112.- Screen appearance of an intracranial foreign body

and radiography of the spine, too little practiced by the average radiologist. Lateral radiography of the spine is generally considered impossible without extraordinary apparatus; on the contrary, the average type of portable apparatus will suffice to make excellent radiograms if intensifying screens are used. Even the sacrum can be radiographed laterally in this manner.

Foreign bodies in the pelvis should be localized with ease provided one makes stereoscopic radiograms. In occasional cases it may be possible to gain more information concerning a foreign body located in or near the rectum if an assistant makes intrarectal manipulations at the moment of the X-ray examination.

In wounds of the head it is sometimes possible for the casual X-ray observation to be very misleading. This is demonstrated in Figures 112 and 113.In Figure 112 a typical intracranial projectile is shown in the frontal and lateral

223

projection. Figure 113 represents the actual position of a projectile which is extracranial and lies within the soft tissues of the temporal region, but which with the usual frontal and lateral X-ray projection appears to be intracranial. This error would hardly occur during a fluoroscopic localization, but it would been entirely possible with a radiographic procedure and the possibility should be duly noted.

FIG. 113- Screen appearance which might lead to an erroneous diagnosis of intracranial foreign body.

In a routine examination the patient is first placed on the horizontal fluoroscope and a brief fluoroscopic survey made to determine the presence of a foreign body. Of course, one may deal with foreign particles too small to be seen with the fluoroscopic screen, but except in the eve and a few other similar critical locations, a metallic foreign body too small to be seen with the fluoroscope

224

usually does not require extraction. When the eyes are properly prepared by a preliminary stay in a darkened room one may see on the screen the shadow of such small substances as a common pin or a bird shot in the cecum or a fairly small foreign body in the eye. In civil practice one or more radiograms will be made in nearly every foreign body case. In France more than 5,000 wounded men passed through the X-ray department of a certain unit without a single plate being made, all the localizations being done by the screen method.

ROTATION OF THE PART

The presence and general locality of the foreign body having been determined, it is easy by rotation of the member or part to determine the relative depth of the foreign body in relation to bony landmarks or other opaque structures or markers. The shadows which move in the direction in which the part is rotated (figs. 114 and 115) will be found to lie between the axis of rotation of the part and the fluorescent screen; in other words, nearest the screen or nearest the upper surface of the part. On the other hand, if the shadow of the foreign body is displaced in the opposite direction to that in which the part is rotated, the foreign body will be found to lie between the axis of rotation of the part and the tube; in other words, nearest the inferior surface of the part or member. This is illustrated in Figure 114 (after Nogier) where projectile P¹ is located near the upper surface, and P ² near the lower surface of the limb. When the part is rotated to the right, in the direction of the arrow a, naturally the shadow of projectile P¹ toward the left. P¹ therefore lies above the axis of rotation of the part and P ² between the axis of rotation of the part and the tube.

FIG.114.- Method of rotation of the part.  (Nogier)

NEAREST-POINT METHOD

After the above-described method of rotation has enabled one to form an opinion as to the general situation of the projectile, the next step is to palpate the part containing the projectile and at the same time to observe on the screen the results of the palpation. One will not employ the unprotected fingers for the purpose, but rather the localizing rod (fig. 109) or any suitable pointer. By the movements of the foreign body under pressure upon the soft tissues surrounding

225

it and by the amount of pressure required, one may estimate very accurately the point upon the skin which is nearest to the foreign body, and by simultaneous rotation of the part the depth at which the foreign body lies. In utilizing the palpating rod, one should turn the part until the position is found in which the shadow of the projectile or foreign body will be as near as possible to the surface. This done, the part is explored by touching it with the extremity of the palpating rod while making light vibrating movements. The nearer the end of the palpator to the " nearest point " the more will the foreign body move with these slow vibrating movements. When the movements transmitted by the palpator show the maximum mobility of the foreign body, this point on the skin should be marked as indicating the shortest possible distance from the foreign body to the skin.

This method is, of course, best adapted to the foreign bodies which are relatively superficial, as in the soft tissues of the arms, legs, neck, axilla, and buttocks; but it is a fact that fully one-half the foreign bodies may be included

FIG. 115.- Method of rotation of the part

in this class. It is also frequently of value in demonstrating that a foreign body is within a joint, or that a foreign body can not be displaced by pressure, suggesting that it may be embedded in very firm deep tissue or in bones.

The nearest point having been marked, the depth of the foreign body is next determined by one of the following methods.

PARALLAX METHOD

This method is based upon the experimental fact that two opaque markers placed at an equal distance from the screen will, when the tube is moved, cast upon the screen two shadows whose range of movement is equal; that is, whatever may be the displacement of the tube, objects lying in a plane parallel to the screen will project their shadow upon the screen in parallel lines. In Figure 116, for instance, T¹ and T ² represent two positions of the tube; P, the projectile; L, the palpating rod held against the part at the same level as the projectile; P¹ and P ^2, the shadows of the projectile with the tube at T ¹ and T ², respectively; and L¹ and L ², the shadows on the screen of the end of the palpating rod under the same circumstances. The line L¹ and L² represents the excursion of the

226

FIG. 116.– Diagrammatic representation of the parallax method.

shadow of the palpator as the tube is moved back and forth from T¹ to T ²; and the line P ¹ P², the excursion of the shadow of the projectile P. It is obvious that when the foreign body P and the end of the palpating rod L are at an equal distance from the tube, the excursion of their respective shadows will be equal and the lines L¹ L² and P¹ P ² will be equal. When the foreign body is nearer the tube than the palpating rod, the excursion of the shadow of the foreign body will be greater than that of the shadow of the palpator; on the contrary, when the palpator is in a plane nearer the tube, the excursion of its shadow will be greater than the excursion of the shadow of the foreign body.

This maneuver is carried out as follows: The end of the palpating rod is placed against the part as near as possible to the foreign body and in what

FIG. 117.- Screen appearance during different steps of the parallax method

227

seems to be the plane of the foreign body, and both shadows are brought to the edge of the shadow of the opened diaphragm. The tube is then deliberately moved in such a way as to cause the shadows to travel to the other edge of the open diaphragm. In Figure 117, a, the foreign body shadow lags behind the shadow of the palpator in reaching the mark, therefore the palpator is in a plane deeper than that of the projectile. If one raises the palpator slightly in order to correct the error (fig. 117, b) and moves the tube just enough to bring both shadows again to the edge of the diaphragm, the tube is shifted in the contrary direction, causing the two shadows to return to the first position. This time the shadow of the projectile travels faster than the palpator, and it is evident that the position of the palpator was overcorrected and brought nearer the surface than the foreign body. Once more a correction is made, as shown in Figure 9, c, and now, when the tube is shifted, both shadows arrive at the other edge of the diaphragm simultaneously. The screen is then removed and a horizontal mark placed upon the skin at the level of the palpator point. From this it is easy to deduce the distance at which the foreign body lies from the surface of the part. The procedure may be repeated on the other side of the part if it be an arm, leg, head, or neck.

FIG. 118.- Schematic drawing of parallax localizer. V, Upright; R, ring; B, ball; P, foreign body; C, opening in base

This method is also valuable in connection with fluoroscopic screen control of foreign body extractions carried out during operation, for it permits the radiologist to tell the surgeon whether the end of the seizing forceps lying in the wound is above or below the foreign body to be extracted.

Figure 118 is a schematic drawing showing the parallax localizer provided for the United States Army Medical Department. Figure 119 is a photograph of the apparatus itself.
            
 FIG. 119.- Apparatus shown in Figure 118

228

ORTHODIAGRAPHIC METHOD

Another simple means of ascertaining the exact distance from the foreign body to the nearest point on the skin is the orthodiagraphic method (fig. 120). The part is rotated until the shadow of the foreign body P and the marker upon the nearest point P¹ lie in the same plane. With the part held in this position, the tube is shifted until the shadow of the foreign body lies in the middle of the illuminated field upon the screen. The diaphragm is then narrowed down to the smallest possible opening which will illuminate a field upon the screen larger than the foreign body, the screen being held in a horizontal position parallel to the table and perpendicular to the central ray. The shadow of the foreign body is then brought to the center of the small illuminated field upon the screen at a and a mark made upon the screen at this point with a grease pencil. The screen being held rigidly still, the tube is shifted until the small illuminated field shows as its center the marker upon the skin at a¹.

The distance aa ^l is equivalent to the distance PP ¹, the depth of the foreign body from the nearest point upon the skin.

METHOD OF RIGHT-ANGLED PLANES

Another simple method of localizing the foreign body is the four-point survey or the method of right-angled planes (fig. 121). This method is applicable only to those parts which can be rotated, unless a special instrument for fluoroscopy in both the vertical and lateral position is available. Special apparatus has been designed for simultaneous fluoroscopy of a part in two directions at right angles to each other.

We first pass the normal ray through the projectile P in the direction aa ^l, and by means of the ring marker the point of exit and the point of entry of the vertical ray are marked on the skin (fig. 122). The part is then rotated through approximately 90º, when for a second time the normal ray is made to passthrough the projectile, now in the direction bb ¹, and these two points again ascertained by means of the ring marker and indicated upon the skin. The

FIG. 120.- Orthodiagraphic method of localization

FIG. 121.- Measurement in two directions (right angled planes)

229

localization of the foreign body is thus definitely determined at the crossing of the two axes, and with the aid of a cross-section anatomical atlas one may reconstruct the part and the position of the foreign body. One may rotate the tube instead of the part if the apparatus permits it. It is not essential that the two planes of observation be at right angles; the crossing of any two axes through the foreign body will indicate its position.

This method is slightly less accurate than the multiple diameters or six-point survey.

MULTIPLE DIAMETERS METHOD

The multiple diameters method consist simply in securing several lines of sight through the body, each of which is made to pass through the projectile. The point of entry and the point of exit of the normal rays used in establishing these lines are plainly marked upon the skin. It is, of course, essential that a small diaphgram opening be employed in these methods.

FIG. 122.- Screen appearance of, and method of using, the ring localizer

FIG. 123.- Malleable band, and the six-point survey methods

 The method of multiple diameters combined with the use of the strips of malleable metal, as employed by several authors, was as follows: ²⁰

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. Note is made of the distance that one unhinged end overlaps the other, and the skin marks are transferred to this metal band. After 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 pencil tracing will show the outline of the body in the plane of examination. The skin mark positions are then transferred to the diagram so as to make an approximate duplicate of the shape of the body and the location of the external skin markings.

If, on this diagram (fig. 123), 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

230

strictly accurate--that is, if the sight lines were properly established-if the shape of the body did not alter by change of position when the band was puton, if the band was properly formed and not distorted afterwards these three lines will intersect at a point; as a rule they are likely to form a small triangle, but with an excellent chance of the projectile being located in this small area. If one now compares the diagram, so formed, with a cross section anatomy for the same region of the body, definite anatomical information as to the position of the projectile and the relative position of muscles or organs likely to been countered in its removal is gained.

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 a definite relation to some anatomical landmark, so that there could be little opportunity for a rotation of the band with reference to the anatomical chart. This will be especially true of portions 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 direction. In some cases, this would be a difficult matter, as with a seriously wounded patient, or one for whom change of position on the X-ray table would be painful.

Lacking malleable metal strips one may make a cardboard cutout conforming to the contour of the part, and transfer to this cutout the skin marks indicating the points of entry and exit of the lines of sight above referred to. This cardboard is not, however, so easily sterilized and taken into the operating room as a guide for the surgeon.

SINGLE-SHIFT TRIANGULATION METHOD

One of the earliest procedures of foreign body localization, as noted above, was that set forth in 1896 by Buguet and Gascar ¹ who applied to foreign body localization the classical
              
formula, depth=  ^bh/_a+b where a represents the distance the tube is shifted; b the distance of the shift of the foreign body shadow; and h the height of the screen or plate from the point of focus of the tube.

The patient is placed upon the couch in the position he will occupy during operation and the screen fixed horizontally above the part and resting on it. The tube is moved about until the foreign body shadow lies in the normal ray, and a mark is placed on the skin at the points of entry and exit of the normal ray. The position of the projectile is further marked upon the lead glass of the fixed screen. On opening the diaphragm the tube is shifted any distance, say10 cm., without disturbing the position of the patient or screen, and the new position of the shadow of the foreign body is marked upon the screen. By measuring the height h from the screen to the point of focus of the tube, the distance a the tube is shifted, and the distance b the shadow of the foreign body was moved, we are able to work out the formula above stated and to arrive at the depth of the foreign body below the screen. In order to determine the exact depth below the skin, it remains only to subtract the distance from the screen to the skin, if the skin and the screen are not in contact. This method

231

may be worked out accurately without arithmetical computation by simply redrawing the procedure to scale.

In civil practice, where only the occasional localization case is encountered, there is no necessity for maintaining a fixed distance between the screen and the focus point, for all these distances and shifts can be easily measured. In war, it will be better to adopt a standard focus-screen distance h (55 or 60 cm.) and a standard tube shift a (10 cm.), and to construct tables by which the depth of the foreign body below the screen can be instantly read from the shadow shift. Many such tables and many graphic devices were published during the war. The device intended for use by medical officers of the United States Army during the late war is illustrated in Figures 125 and 126. For use of this apparatus it is

FIG. 124.- Classical single-shift triangulation method

better to employ: (1) A fixed tube shift of 10 or 15 cm. may be used or tin image shift of an exact number of centimeters. (2) A fixed target-screen distance may be used. This is not, however, always convenient. (3) The exact setup of Figure 124 may be reproduced by use of a device shown in Figure 125, 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, 0, 1, 2, etc., 1 cm. apart, and a slider, P, with a latch engaging these notches. A scale, S, with its zero point at the upper end is carried by G. A lug at H is in line with the zero of G. If, now, DH-tube shift, GH-target-screen distance, P₁O-image shift, then a straight line, P₁D will cross the scale, S, at the depth of the foreign body below the screen. The instrument should

232

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 is the depth sought.        
When using the standard table the slider, E, is adjusted so that a length measured on the screen-carrier 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 reproduce 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 method., also during the tube shift, since the showing method of using adjustable double-slider caliper relative error in measuring 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 accurate as any of the depth methods.

In the single-tube shift method there are various procedures which maybe used. They all require essentially the same data, namely, (1) tube shift,

233

(2) image shift, (3) target-screen distance. If these distances are measured to scale in centimeters, it is possible to compute the end result.

The apparatus supplied for this method includes a scale whereby a definite image shift may be made, if that is desired 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.

FIG. 126.- Apparatus shown in Figure 125

The complete equipment, including the reproducing device or wall meter and accessories, is shown in Figure 126.

The stereoscopic method is really a single-shift triangulation method. During the war the United States Army Medical Department perfected an apparatus devised by the late E. W. Caldwell, of New York, permitting stereoscopic fluoroscopy. This method, of course, requires special apparatus and the instrument is not yet generally upon the market. The stereo radiographic method is the procedure of choice when plates are made. In civil practice it is well to make stereoscopic plates in addition to the ordinary screen localizations.

234

DOUBLE-SHIFT FIXED-ANGLE METHOD

A number of single and double shift fixed-angle methods have been described, all, however, based upon the same principle. The method of Strohl,²⁴ professor of physics at the Sorbonne, is as follows:

At a convenient distance above the tube T (fig. 127), usually on the diaphragm of the tube holder, it is easy to fasten a piece of cardboard or aluminum to which are affixed two bits of straight wire, W² and W³, placed parallel on either side of the midline W¹, so that the distance between the wires will bear a

FIG. 127.-Method of similar triangles (double-shift, fixed-angle method)

fixed relation to the distance O from the cardboard or aluminum sheet to the focus of the tube. In other words, in the triangle TW²W³, the distance W²W³ bears a definite relation to the distance W ¹ T. For convenience, let us say that the two distances are equal and that W²W³ equals W¹T. If desired. a third wire may be added at W¹, coinciding with the normal ray. W²W^l, therefore, equals W³W^I. It is a geometrical fact that the distance between the shadows cast upon the screen by the wires W² and W³ will, under these circumstances, always be equal to the distance from the screen to the focus point of the tube,

235

so long as the screen is held horizontal to the tube. With a small diaphragm opening the tube is brought directly beneath the foreign body P (fig. 127) and the position of the foreign body shadow marked upon the screen at P¹and upon the skin directly underneath. The screen appearance at this moment is shown at a (fig. 128). Two leaves of the diaphragm are then opened widely making as lit and giving the appearance illustrated in Figure 128, b; the tube is then shifted to the left, during which movement the shadow of the right wire W2 will also travel toward the left while the shadow of the projectile will travel toward the right, until a tube position will be reached where the two shadows coincide(fig. 128, c). This point is marked upon the screen with a grease pencil. The

FIG. 128.- Screen appearance at different steps in the double-shift, fixed-angle method

tube is then shifted in the opposite direction until the shadow of the left wire, W³, and of the projectile coincide (fig. 128, d). This point is also marked upon the screen with a grease pencil. According to the law of similar triangles, the distance between the two marks upon the screen equals the distance from the screen to the foreign body; and to estimate the depth of the foreign body it only remains to subtract the distance from the screen to the skin, if the screen itself does not rest directly upon the skin.

The distance between the wires W² and W³ may bear any given relation to the distance from the focus point to the plane in which the wires are fixed. It is only necessary to know this relation in order to estimate the depth of the foreign body by this very rapid and accurate method. It is not necessary to

236

know the focus distance of the screen or the distance of the tube shift. The wires may be placed upon any of the ordinary types of fluoroscopic apparatus without interfering with the routine work; one must only know the ratio of the distance between the wires to their distance from the focus above referred to.

In place of the wires, which are sometimes somewhat hard to see through the denser portions of the body, one may file upon the two leaves of the diaphragm three notches (fig. 129), one directly above the focus of the centered tube, and one on either side of this central point at any given distance. The ratio may be varied, just as in the Strohl method. With the diaphragm closed, one has upon the screen, therefore, three diamond-shaped, illuminated notches (fig. 129); the two outermost notches correspond to the shadow of the two wires shown in Figure 128, b. The tube is shifted in the same manner, first to the left and then to the right until the foreign body shadow is brought to the center of each of the diamonds; these spots are marked upon the screen with a grease pencil, and the distance between them measured and translated into the depth of the foreign body.

During the war the so-called "26-degree method"--the distance from the middle notch to either of the outer notches being half the focus-diaphragm distance-was popular among French radiologists and was widely adopted by

FIG. 129.- Screen appearance after notching the diaphragm leaves for the Roussel method

our own medical officers. With this method, only one shift was made from the central notch to one of the outer notches, and the distance of the shadow shift multiplied by two to determine the depth of the foreign body below the screen.
HARPOON -METHOD

The harpooning method, the insertion of a sterile needle through the tissues to the foreign body, which serve as a guide to the surgeon in removing the projectile, requires no special apparatus not found in any hospital with a fluoroscopic X-ray equipment.

The instruments, the field of operation, and the surgeon's hands must be surgically clean, and a sterile sheet or towel must be held between the operative field and the fluoroscopic screen. By rotation and manipulation of the part the approximate anatomical position of the foreign body is determined as nearly as possible. The needle when introduced will mark out the line of the surgeon's approach; if the track of the needle is likely to pass near vital structures it is of importance that this line be determined in consultation with the surgeon. The path of attack having been determined and the surgeon having marked on the skin approximately where he wishes to make his incision, the part is rotated under the screen so that the skin mark will be vertically over

237

the foreign body. A needle of proper length having been selected, it is seized with forceps and held at such an angle that the fingers of the operator will not be exposed to the rays. Under the fluoroscopic screen, the needle is pushed down upon the foreign body and left in situ.

This method has been modified and improved under the name of the"trocar and cannula method" by various surgeons of the allied armies. It should always be used under the direct supervision of a competent surgeon or of one who has the necessary anatomical knowledge and surgical judgment to use it without danger of infecting the patient or of injuring important struc-tures. In cases with encapsulated foreign bodies the trocar and cannula method is often of great value, but it is not useful as a routine procedure in recent wounds, where the surgeon usually approaches the projectile or foreign body through the path by which it entered.

Under anesthesia, the skin should be punctured with a sharp scalpel, after which the cannula, with the obturator in place, is slowly passed into the tissues until it comes into contact with the projectile as determined by touch or by fluoroscopic observation at varying angles. After contact is secured, the obturator is removed and a piece of piano wire, bent at the lower end in the form of a fishhook, is passed well through the cannula. The latter is then withdrawn, leaving the piano wire hooked into the flesh. If necessary, the external end of the wire may be clipped with forceps or cut off short, and bent down close to the skin. The length of wire introduced beneath the skin indicates to the surgeon the depth of the foreign body. It is very important that the introduction of the needle or trocar should be carried out with the instrument in the line of the normal ray; any attempt to insert it at any angle will result in considerable mutilation of the tissues.

The harpooning method is not only a method of localization, but it is also a method of guidance for the surgeon during the operation of extraction.

HERTZ COMPASS METHOD

The use of the Hertz compass is foremost among the methods which serve to localize, and to guide the surgeon. This is an apparatus of which several types, all similar in principle, were employed during the war. For clinics where there are frequent extractions of foreign bodies from the cranium and from the deeper structures of the shoulders, axillae, lumbar region, pelvis, and buttocks, this instrument can be highly recommended.

As originally proposed, this instrument was intended to be used in connection with radiographic work, whereby a permanent record should 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 measurement, 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 Hertz compass is the possibility 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

238

sphere, a meridian arc of which is carried by the compass. 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 coincide 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 of the sphere is obstructed by the body of the patient, the amount it lacks of reaching the center will be the 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 of

FIG. 130.- Hirtz compass guidance during a surgical operation

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 Figure 131 and schematically in Figure 132. Three metal arms respectively labeled 1, 2, and 3 in clockwise rotation are so mounted as to turn freely upon a central pivot and have their upper surfaces all in a single plane. Each of these arms carries a slider, which may be adjusted to any position along the 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 thumbscrew. These legs are graduated and the zero point is not at either end of the legs, but a few centimeters below the upper portion, which terminates in a small knob. The center post about which

FIG. 131.- Hirtz compass

the arms rotate has a hole at right angles to the plane of the arms and is also shaped to carry the curved metal are, A. (fig. 132.) The hole in the slider on are A, carrying the indicating rod, can be made to coincide with the opening through the center post.

239

When the legs are set at zero, quite irrespective of the position of the slider on the arms or of their angular position, and the compass stands on a plane surface, the indicating 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 indicating rod may be adjusted in contact with the slider on A, 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.

Figure 133 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 been displaced, so that the pointer still reaches the center point, P, in this plane.

Figure 134 shows the compass actually set upon the body of a patient, its legs resting on three skin marks, M, N, and O, and with the indicating rod pointing toward the projectile, 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

FIG. 132.- Schematic drawing of Hirtz compass with legs adjusted at zero points and with legs adjusted at zero points and resting on a plane

FIG. 133 Arms and indicator of Hirtz compass. Same position as in Figure 132, but with legs elevated on blocks whose tops might corrspond to skin markers

is indicated in Figure 134 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, S’, 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 indicated by the dotted line. It is evident from the construction that the surgeon may place the arc, A, in any position throughout 360^?, and the slider at any position from the center to the extreme end of the arc, and still have the indicating rod point to the foreign body and show its depth from the point of contact with the skin. Figure 130 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 to which it belongs and yet have the indicating rod in the proper position is easiest seen in Figure 135, 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, parallel to the plane of the three arms of the compass, to be drawn through the projectile. The leg attached at arm number one

240

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 plane, from which measurements are made, to the lower plane, containing the projectile, is measured and, likewise, the distance MM’, 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 the depth of the marker from any plane of measurement, for example, that of the fluoroscopic screen ora photographic plate. The fluoroscopic screen may be placed in any position parallel to the base plane, EP, and the difference, 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 difference between the depth of the projectile below the fluoroscopic screen, or other plane of reference, and the depth

FIG 134.- Schematic drawing of Hirtz compass set up on skin of patient

FIG. 135.- Reason for shift of leg of compass from zero point by the amount stated

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 of measurement of its own skin point.

The data necessary to properly adjust the compass may now be stated by reference to Figures 132 and 135. The indicating rod in the central position and the three legs of the compass mark out, in any plane parallel to the base plane of Figure 132, 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. Figure 132, is then in a vertical 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, E, F, G, 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 at fluoroscopic process is immaterial. as the steps in its use will be identical.

241

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 shown at A, Figure 136, 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 removing arc, A, and allowing the indicating rod to project a short distance below the center, with the legs temporarily removed. The auxiliary compass has its arms numbered in the same way as the original Hertz 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 the other two are movable, but may be clamped by thumb nuts to the ring. It is evident that placing the perforation in the screen in the vertical ray passing through the projectile definitely fixes the position of the center post. If, then, each marker in turn is brought into

FIG. 136.- 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

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 through 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 provided. As soon as these four depths and the four marks in the plane of the screen have been

242

determined, the work of the roentgenologist is completed, provided he has made sure that the skin marks are plainly visible. The adjustment of the compass may then be carried out by an assistant to either the roentgenologist or the surgeon, after which the instrument can be sterilized and is ready for the surgeons use.

FLUOROSCOPIC METHOD, WITH AUXILIARY COMPASS

Find the shadow of the projectile, Po, on the screen, and reduce the size of the diaphragm, keeping the shadow in the center of the illuminated area. 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. Mark the skin through the opening by use of the special marker provided. Determine the depth of the projectile by either method A. or C. Raise the screen and attach three metallic markers (preferably three small washers) to the skin at suitable points, and mark the skin at each point selected. Choose skin points with care to ensure: No in- terference with probable incision; proper stability of the compass; as firm foot points as possible. Lower the screen near to or touching the skin, with the central hole still in the vertical ray through the projectile, and insert the pin

FIG. 137. - Method of showing fluoroscopic adapter with Hirtz compass

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. Shift the tube to bring the right-hand marker in the vertical ray (leaving screen locked), and adjust the slider on arm No. 1 so that its opening coincides with the projection of the marker, Figure 137. If washers are used the round opening is easily identified. Do the same with each of the other two markers, insuring that No. I does not move when adjusting the others (a small clamp will aid in this) and lock each arm. The central pin and the three sliders then give the positions for the arms and sliders of the compass. Remove the auxiliary compass and determine the depth of M, N, and O below the upper surface of

243

the glass on the screen. For the depths of M, N, and O use the small rods provided with friction sliders and make the measurement 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 sliding 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 measurements, to minimize chances of error. If no further fluoroscopic work is to be done these depths may be determined in daylight. Otherwise use the vertical ray from the tube.

SETTING THE HIRTZ COMPASS

By use of the auxiliary compass.- (1) Remove the arc and the indicator rod; lower the three legs until the upper (rounded) ends project 1 to 2 cm. (2) Lay the auxiliary compass on a flat surface with the center pin upward. Invert the Hertz 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 No. 1 and its slider to such a position that on loosening leg No. 1, it will drop into hole of the No. 1 slider of the auxiliary. Tighten set screws of slider and of leg No. 1 (fig. 138). Proceed in the same manner with arms, sliders, and legs Nos. 2 and 3. Tighten wing nut at center of Hertz compass, thus locking compass arms. (3) If pedestal support is provided

FIG. 138.- Setting arms and legs of Hirtz compass directly from the auxiliary compass

set the lock sleeve on the vertical rod, so that when the pedestal stands on a flat surface, and the Hirtz compass is placed thereon, with the pedestal rod through the central bole 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 between the depth of the projectile and the depth of the skin marker on which each individual leg is to stand. (Leg No. 1 stands on skin marker No. 1, etc.) Tighten each leg,

244

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.^a

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.

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 PO (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 PO; identify each by number and write opposite each the depth in centimeters to the skin below the fluoroscopic screen. The depth of PO below screen must be similarly indicated. (2) Take the Hertz compass with indicating rod inserted in central hole, and set point of indicating rod on PO of diagram. Loosen wing nut at compass center, thus releasing arms; bring leg No. 1 to stand on mark No. 1 of diagram. Proceed identically with legs Nos. 2 and 3; then, with indicating rod and the three legs accurately

FIG. 139.- Detail of holder for direct setting of Hirtz compass

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 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 Hertz compass.- Several devices for holding the Hertz compass in order to make a direct adjustment of the foot points and leg heights on the patient have been proposed. This method possesses two distinct advantages: It may be done quite expeditiously; it indicates clearly to the operator how the compass is going to stand on the patient when in use. Its disadvantages are: The necessity of considerable illumination in the fluoroscopic room when placing the compass; danger of movement of the patient between localization and final adjustment; need for the compass both in the fluoroscopic rooms and in the operating room.

In order to adapt this method to the standard table, the design shown in Figure 139 has been developed. This consists 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.

 ^a 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 No. I with its sleeve indicating the skin depth for marker No. 1, mark this distance on the line previously made, and reset the sleeve to the length remaining on the projectile depth line.

245

The collar, A, on the tube has a V-shaped projection intended 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 alignment of the central axis of the compass with the vertical ray through the projectile, and the bringing of the compass 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. 140.)

Care must be taken to insure that the patient does not move between the localization and the completion of the adjustment; that the pointer is raised from its zero the correct distance; that all parts of the compass are locked before removal from the body.

FIG. 140.- Direct setting of Hirtz compass. Compass and holder in position

The holder must be adjusted before it is used the first time as follows: Remove screen-holding rod from the horizontal socket and insert holder. Remove arc from the compass, insert hub in the 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. Place 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. Make a scratch mark where the V on the ring comes in contact with the socket. Remove the holder and file a small notch with a triangular file to take the V on the collar. Test out as to level, when the holder is replaced in the socket with the V 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.

246

The above steps need to be done only once and the following procedure for use is then quite simple: Remove arc from the compass and insert in the holder, fastening with the thumb nut, B. 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. 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. 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. 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. Raise compass slightly by the vertical move- ment of the carrier, mark skin points for the feet, and identify them clearly. This method is much more convenient than to mark the skin first and then adjust the compass to fit the marks. Remove compass, read and record height settings of legs, then record position of foot points, and center for resting the compass later if it should be necessary. For use in the operating room the compass may be sterilized by a flame.

USE OF THE HERTZ COMPASS WITH PLATES

FIG. 141.- Centering of tube above plate holder on cassette with small cross wires, photographic method, Hirtz compass

When it is desired 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 positions, either upon a single plate, or upon two separate plates or films, without movement of the patient or skill markers. The latter method is usually preferred.

There is furnished for this work a small, flat square of celluloid into which are inserted two small steel wires forming a right-angled cross. The celluloid has two holes punched in diagonally opposite corners, through which a tape may be passed, and this is to be tied around the tunnel plate changer so as to fix the desired centering mark, when two plates or two films are to be used.

247

Figure 141 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.

Figure 142 shows the tube, patient, and markers in position for one of these exposures. One should not forget to attach 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 Figure 143. 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

FIG. 142.- Skin markers, plate holder, and tube holder in position for photographic method, Hirtz compass

erected to the plane of the plate at the point X and extending upward a distance of 60 cm. Let F ₁ F ₂ be positions of the focus in a line parallel to the plane of the plate at the level C, and assume that CF ₁, and CF₂ are each three centimeters in length. Suppose that M is one of the markers on the patient's body. When an exposure is made with the target at F ₁, the shadow of M will fall on the plate at M ₁ and, when an exposure is made from the position F₂, the corresponding shadow will be M₂. Had the exposure been continuous during the motion of the target from F₁. to F₂, there would have been found on the plate a straight line of shadows connecting M₁, and M₂. If we drop perpendiculars from the two

FIG. 143.-Schematic representation of plate, cross-wire marker, ,marker, and tube focus positions for radiographic use Hirtz compass

focal positions to the plane of the plate, intersecting it at the points F'₁F₂, we see that F',F₁M₁ is a plane perpendicular to the plate and passes through M ₁, and the trace of this plane upon the plate is F₁ M ₁.

248

In the same way a plane passed through F₂F'₂M₂ will be perpendicular to the plate and its trace will be F'₂M_2. It follows from geometry that the intersecting line of these two planes, MM_o, will be a line passing through the point M and perpendicular to the plate. Consequently M_o is the foot point of this marker on the plate to be used in the compass adjustment. Also the lines M ₁M ₂, F' ₁,F' ₂ and F ₁ F₂ are parallel.

Figure 144 shows part of a developed negative upon which there appears a shadow at M _l, a shadow at M₂ and a single image of the marker on the plate a single image, since its motion is zero or nearly so, the marker being most in contact with the plate itself. If one joins M _l and M ₂, by a straight line and then draws through the center of the cross a line parallel to M₁ M₂ 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 F₁, and F₂ of Figure 143. Cross connection between the ends of these lines, that is F'₂ M₂ and F'₁, M₁ then definitely locates the point M which will be the foot point sought.

FIG. 144.- Construction for finding one of the foot points M from the shadows of a corresponding marker as shown at M ₁ and M ₂, and the shadow of the cross marker X

FIG. 145.- Complete chart for setting feet of Hirtz compass

The length of the line MM2 will clearly decrease as M is placed nearer the plate, and increases as it is raised. For the definite 60-cm. target-plate distance and 6-cm. tube shift there corresponds one height MM_o for one image shift M₁M₂. These relative values are shown in Table 26 in which all measurements are given in centimeters or tenths of centimeters.

Figure 145 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 judgment 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. These data are used exactly as were those derived from fluoroscopic examination. It will require a considerable amount of skill and judgment 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. Especially one must insure that the shadows of all the markers fall on the photographic plate. It is also clearly undesirable 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 decidedly large shift in the position

249

of foot points. Transparent celluloid scales arc sometimes furnished, which assist somewhat in determining whether the shadow of the markers will fall on the plate.

Knowing approximately, by previous fluoroscopic or other examination, the position of the projectile whose localization is sought, select a plate changer of proper size, attach the cross, and place on the table in the position to which it is to be used.

By means of a plumb bob, 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, Figure 143, is 60 cm. Adjust stops to allow the tube to move 3 cm. in each direction from the central point.

Place the patient on the tunnel plate changer, taking care that the cross, plate changer, and tube are not displaced in the process. Or, if the tube holder is rotated, fix stop for its exact return. Make sure that the tube is three centimeters from its center point and insert a plate. 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 he attached to the patient's skin with small pieces of adhesive. Make the exposure needed. 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 measurement.

FIG. 146.- Equipment supplied for use with Hirtz compass

 If the exposures are to be made on a single plate, be sure not to overexpose. When using two plates, the image of the cross is used to superimpose the plates and to transfer the data to the record sheet.

Make the record described above, locating the foot points and the center points. Read M₁M₂, N₁N₂, O₁O₂, and P₁P₂, in centimeters and fractions, enter these on the record under column marked spread, and enter under height the corresponding number in Table 26. Thus:

CHART

The equipment supplied for use in method E is shown in Figure 146.

250

TABLE 26.- Measurements for use in connection with Hertz compass [Focus plate distance, 60 cm.; tube shift, 6]
   
The advantages of the Hirtz compass in selected cases are numerous. After the sterilized compass has been placed in position, the penetration needle, when brought in contact with the skin, indicates the point where the incision should be made, and the depth and the direction in which the foreign body lies. By means of the rotating device through which the penetration needle is passed, the surgeon can select the point of entry without in any way embarrassing the usefulness of the instrument. The instrument, being sterile, can be re-applied as often as needed during the operation.        
In using the compass, it is important that the skin marks selected for the compass legs should constitute a large triangle and that these marks should not be covered by drapes or towels during the operation. When the compass is being set, the patient should lie in either the prone or the supine position rather than on the side, and at operation exactly the same attitude should be assumed. It is important that the muscles be relaxed as far as possible; otherwise muscular contraction maintained during the X-ray examination is likely to disappear during anesthesia and thus possibly alter the position of the projectile to a considerable degree. Duval ²⁵ cites a case in which a bullet located in the adductors of the thigh shifted eight centimeters when the contracted muscles were relaxed.

DEPTH OF ANATOMICAL LANDMARKS BENEATH THE SKIN

The table given below is of value in determining the exact position of a foreign body in relation to points on the skeleton. In their article published in connection 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.²⁶ Previous to the war, the surgeon studied the ultimate depth of his operation only with regard to certain surrounding anatomical landmarks, 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 trans-verse process of the 12th dorsal vertebra, the surgeon has little knowledge as

251

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 examination and, as a result, the extremely thin and extremely obese are not present.

TABLE 27.- Depth of anatomical landmarks

252

TABLE 27.? Depth of anatomical landmarks?Continued

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 general parts--the base or headrest, as illustrated in Figure 147 and the localizer, as shown in outline drawing, Figure 148. The headrest base is composed of the following parts: A. plate-slide tunnel, so constructed as to protect one-half of a 5 by 7 photographic plate while the other half is being exposed, and to protect the exposed half while the second

FIG. 147.-  Headrest for use with the eye localizer

exposure is being made. Four rubber-tipped legs to raise the tunnel so that it will act as a pillow to hold the patient's head level when lying on his side. A plate holder having a slide that will protect the plate from the ordinary light, but offer no resistance to the X ray. An arm or handle attached to the plate-holding slide to enable the operator to shift the plate the correct distance for each exposure, and to withdraw the same when both exposures have been made. A pneumatic cushion for the comfort of the patient. A double clamp to hold the patient's head and to prevent any horizontal movement. A single vertical clam to press the head downward upon the pneumatic cushion. The localizer consists of a heavy metal base, Figure 148; an upright standard, B, to support the localizer and permit the

253

same to be adjusted and held firmly at any desired height. The indicator ball D, with its needle-supporting item D², which, when properly adjusted to the center of an eye, will cast its shadow on the photographic plate and serve asa landmark to indicate the center of the cornea.

The metal tip E, of stem E² is made cone shaped, so as to more easily differentiate its shadow from that of ball D. These indicators are permanently adjusted a known distance apart (15 mm.), and the base of the localizer is provided with two holes exactly 15 mm. from center to center, which should be employed to verify this adjustment in case of doubt. When 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 flight (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 indicated (front view).

Tube C¹² and notch F¹⁸ 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 D ² F¹⁴ is a spring trigger which presses upwards against pin F.¹³ F⁵ is the end of the rod to which the indicator-ball and cones D

FIG. 148.- Sweet eye localizer

and E are attached by bracket F, the whole being supported by passing through tube C.⁵ Spring F¹⁴ being attached to stationary tube C⁵ by means of bracket C⁷ rod F⁵ with bracket F⁶ can be pressed forward until pin F¹³ is engaged by notch F.¹⁵

By loosening set screw C⁴ the bracket C can be raised or lowered until ball D, with its supporting stem D,² is in exact alignment with the center of the cornea of the affected eye, and the screw is then tightened.

The patient is instructed to close his eyes, and the entire instrument, with its base, is slid forward until indicator ball D presses into the eyelid approximately its thickness. The trigger F¹⁷ is then depressed to disengage notch F¹⁵ from pin F¹³, when spring F¹⁶ will cause the rod F⁵ and indicator-ball D and cone E to rebound exactly 10 mm., being restricted by knob F⁷ in slot C.⁶ 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

254

inflated cushion does not extend over the marked lines on the cover-otherwise it will cast a shadow on the photographic plate.

If the subject shows a tendency to move about, the horizontal clamp, as shown in Figure 147, must be adjusted to the base of the head and forehead, otherwise the vertical clamp, as shown in illustrations herewith, will be sufficient. 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 central rays will exactly parallel the front vertical plane of the patient's eye, as shown in Figure 149.

A plate, having previously been placed in the plate holder, is now placed in the tunnel with the outer flange protruding, 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. 148) 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

FIG. 149.- Position for first exposure in localization of projectiles in the proximately its thickness; eye. Be certain that the tube is centered accurately over the cone so the trigger spring is then that both ball and cone will be superimposed

released and the indicator ball and cone recede exactly 10 mm., thereby permitting the patient to open his eyes and wink them in a natural manner. By referring to localizer chart you will observe that due allowance of 10 mm. has been made by placing the indicator ball and cone just that far from the front plane of the cornea. It should also be borne in mind that the front of the cornea is 10 mm. in front of the shadow of the indicator ball, as shown in your negatives. The tube is now centered over the localizing ball and cone so that the shadows of the two will coincide (fig.149). 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 to look constantly at this object while the two exposures are being made.

255

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 supporting stems, as shown in the right-hand half of illustration (fig.150) 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 causing the central rays to pass obliquely through the center of the cornea of the patient's affected eye, as shown in Figure 151

FIG. 150.- Specimen plate of projectile in the eye, illustrating the method of measurement

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 upon by the rays in the first exposure and bring its unexposed 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 4 the tube at any specific distance from the plate, or even that it be the same distance from the two exposures. Neither is it important that

FIG.151.- 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 second exposure, as by the must he kept in alignment

the tube be shifted an exact or known distance for the second exposure, as by the use of the charts and Sweet's method the course of the ray is automatically established. This is shown by the line A-D through P ¹ and P ² of outline drawing, Figure 152.

256

CHARTING THE PLATES

In charting the plates the following 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 projecting their supporting stems and establishing the visual axis of the eye (fig. 150).

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 represent the exact distance (distance R. fig. 152).

FIG. 152.- Schematic drawing of localizing chart, illustrating the method of obtaining measurements

On the vertical line that has been drawn through the shadow of the foreign body (right-hand half of fig. 150) measure the distance of the foreign body above or below the horizontal line and indicate the same on the chart above or below the axis, distance V locating dot F¹.

Place another dot on the same horizontal plane and draw a line through these two dots, parallel to the axis, projecting 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^l. We have yet to establish its location to the nasal or temporal side.

Project a line vertically through point F¹ to the 450 angle (see fig. 153),thence horizontally through the horizontal section.

257

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 dividers the distance of the shadow of the foreign body above or below the horizontal plane of the shadow of the ball is measured, and the same is marked 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. The distance of the shadow of
       
FIG. 153.- Chart used in eye localization

foreign body above or below the horizontal plane of the shadow of the cone is measured, and the same marked 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^I and P² will represent the true course of the rays in the second exposure, and its intersection with the projected line from the side view through the point F¹ will be the position of the foreign body when viewed from the front, while a vertical projection 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 mm. in diameter, but this may vary 3 mm. from the average.

258

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 cases where the foreign body is located 1 or 2 mm. 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 parallel to the plate, so placed that the eve is rotated toward the top of the head. Make an exposure of one-half the correct amount, then shift the vision to a point well toward the feet, still keeping the head fastened securely in place, and expose 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 its position near the exterior and anterior portion of the globe would help differentiate this.

In an acute case where a localizing apparatus is not available, this method may be all that is necessary.

EXTRACTION

X-ray guidance during surgical operations is indispensable for the expeditious removal of a certain proportion of foreign bodies. It is applicable not only to the extraction of projectiles and other foreign metallic substances, but also for the removal of pathological foreign bodies, such as renal calculi, encountered in civil life. In fact, if there is any question as to the location of an elusive stone or doubt as to whether or not all stones have been removed, it is possible, by means of the fluoroscopic bonnet and portable X-ray equipment, to make an X-ray examination of a kidney which has been lifted out of the wound at operation. This method of screen control is also useful during the injection of opaque fluids into the urinary tract, during the aspiration of intrathoracic accumulations of fluid, and in the control of injection of air, oxygen, and other gas into the pleural or peritoneal cavity, or into the ventricles of the brain.

The method of intermittent fluoroscopic control is more satisfactory for general use in the extraction of metallic foreign bodies than are electro vibrators, telephone probes, or other similar devices, for the reason that a considerable percentage (approximately one-fifth) of the foreign bodies of war are not magnetizable. Fluoroscopic control methods save time, lessen trauma, and conserve the temper of the surgeon.

The requirements for the malleable band, harpoon, and Hirtz compass methods have already been sufficiently referred to in the preceding section.

Two other methods of fluoroscopic control will be described in detail: The method of the open screen in the darkened room, and the bonnet method in the usual light of the operating room.

FIG. 154.- EXTRACTION OF A FOREIGN BODY UNDER FLUOROSCOPIC CONTROL. THE OPEN SCREEN METHOD IN DARKENED ROOM. THE RED LIGHT ABOVE THE TABLE SERVES TO ILLUMINATE THE SURGICAL FIELD IN THE PRELIMINARY STEPS BEFORE THE DIRECT SEARCH FOR THE FOREIGN BODY BEGINS. BY MEANS OF THE FOOT SWITCH THE RED LIGHT IS TURNED OUT AND CURRENT IS TURNED INTO THE X-RAY TUBE BENEATH THE TABLE, AS ILLUSTRATED IN FIGURE 155

FIG. 155. -THIS ILLUSTRATION REPRESENTS THE RADIOLOGICAL STEP OP THE PROCEDURE OP LOCALIZING FOREIGN BODIES UNDER FLUOROSCOPIC CONTROL. THE ROOM IS IN DARKNESS EXCEPT FOR THE FLUORESCENCE PROM THE SCREEN DURING THE ACTUAL X-RAY LOCALIZATION

259

OPEN SCREEN IN DARKENED ROOM

The requirements for this method are the usual fluoroscopic horizontal table; a fluoroscopic screen; a proper overhead red or green light, sufficiently bright, preferably under control of the same foot switch that controls the X-ray current; surgical equipment, including sterile sheets, gloves, gowns, and instruments.

No instruments of special design are needed except a pair of narrow-jawed forceps. A special bullet-seizing forceps or a forceps of the type used for exploration of the gall bladder or common duct is usually satisfactory for grasping the foreign body. The forceps of Wullyamoz are bent at a right angle in such fashion that the prehensible portion of the instrument is held in the line of the vertical ray without exposing the hand of the operator.

If it is not convenient to use the ordinary horizontal fluoroscopic table, any wooden or aluminum topped table will suffice if so constructed that an X-ray tube can be placed beneath it without danger of short-circuiting the current. The modern bedside equipment (fig. 156) is very satisfactory for this purpose. The small Coolidge tube at the tube-holding arm can be turned downward and placed under the table at a point vertically beneath the foreign body when the patient lies in the position for operation. Blankets of black or green cloth draped around the table to the floor will prevent the escape of light into the room,

FIG. 156.- Arrangement of the tube and table for the bonnet method

or a smaller piece of black cloth can be placed directly around the tube for the few moments necessary for the examination. The ordinary horizontal fluoroscope is, of course, already equipped.

In military hospitals in the forward area there is seldom need for the use of the open screen in the darkened room. When this method is required the patient can be carried into the X-ray room and the surgery done there. This method interrupts, of course, the routine work of the X-ray department and hence for forward hospitals the bonnet method, described below, is preferable, as it can be carried out in the operating room. In stationary hospitals, where there is likely to be more time for deliberate work, the writer considers it desirable to provide a special room for extraction of foreign bodies under X-ray control, employing the method of the open screen in the darkened room for a certain percentage of difficult extraction cases.

One may use the ordinary lead-glass covered, fluoroscopic screen: or an old intensifying screen, no longer useful for radiographic work, may be fastened

260

to a piece of lead glass by means of adhesive tape and held by an assistant whose hands are properly protected by leaded rubber gloves. Special tables were constructed during the war supplied with a hinged arm for holding the fluoroscopic screen, so that when the screen was not in use it could be tilted back out of the way of the operator.

For the overhead light one may employ an ordinary incandescent bulb, stained red. This red light may be as brilliant as the surgeon desires. The writer prefers a bluish bulb mounted in a yellow globe, which gives a very agreeable light, much like moonlight. On the other hand, the overhead light in daily use in the fluoroscopic room may be utilized in place of a red light for most of the manipulations; if at any stage of the operation more illumination is required, a headlight may be supplied to the surgeon. Where extractions under X-ray control are frequent, it will be advantageous to provide a special source of overhead light, 5 or 6 feet above the fluroscopic table, so arranged with glass filters that a powerful red light is thrown upon the operative field. If this light is equipped with a rheostat for dimming or intensifying the illumination, it will be all the more serviceable. In the absence of more elaborate equipment, a hand lamp equipped with a red bulb will serve.

Before the operation it is important that both the surgeon and the radiologist spend ten or more minutes in an abscurely lighted room, or with the eyes protected by smoked glasses.

After the patient has been made ready upon the table, and the sterile linen has been arranged as for any aseptic operation, an additional sterile sheet, known in France as the velum, is thrown over the operative field and fastened down by towel clips on the side next to the radiologist, opposite the surgeon. On the side next to the surgeon, the sheet is held at its two corners by sterile forceps in the hands of assistants. These assistants may or may not be dressed for sterile work as the circumstances warrant. The assistants holding the front ends of the velum drop it over the operative field, protecting it from the radiologist and his unsterile screen. Figure 154 shows the operating scene at this moment. The red light is then extinguished and the X ray is turned on (fig. 155). The radiologist adjusts the tube under the table so that only a small spot on the screen, not more than 3 cm. square, will be illuminated, and the foreign body is brought to the center of this spot. The tube is then fixed in position and the radiologist makes pressure against the skin with a sterile pointer at a spot directly over the foreign body.

The surgeon notes the point on the skin thus indicated and, if it is a satisfactory path of approach to the projectile, makes his incision there. The radiologist then steps back. the velum is raised, care being taken not to contaminate its underside, and the surgeon proceeds with the incision and dissection toward the foreign body.

During the dissection, at such times as he wants help, the surgeon holds the end of a forceps directly over the point where he believes the foreign body to lie, and the protecting velum, its underside still sterile, is turned down over the wound, the red light is again extinguished, and the radiologist corrects the position of the surgeon's forceps by directing him to move it to the right or the

261

left, until the correct spot is found. The surgeon has only to work directly downward to come upon the object of his search.

It will be unnecessary in many cases to expose the foreign body completely by dissection; often it is only necessary to determine its approximate anatomical position, especially when it lies in the depth of a muscle. Frequently it will be possible, after making a small skin incision, to extinguish the red light, turn on the X-ray current, and under fluoroscopic guidance insinuate the end of a closed, narrow-jawed, blunt forceps into the tissues until it touches and moves the foreign body. With the X-ray current still on, the jaws of the forceps are separated, the foreign body grasped and extracted. The red light or the ordinary brilliant white light of the room is then turned on, and the remainder of the operation conducted in the usual manner. In some situations it will be possible to turn a jagged projectile so that the extraction forceps will seize it by its sharp or jagged edge or point. A needle may be grasped near one end. One who has not gained experience in this method of extraction can not appreciate the ease with which a foreign body may be secured and removed in this manner. In a series of several hundred extractions performed in this way, the writer has never been longer than 20 minutes, usually much less, from skin puncture to extraction of foreign body, and only twice has he failed to remove the foreign body. Both failures were in cases in which hypodermic needles were broken off deep in tissues too thick to be easily studied with the fluoroscope.

Protection of both the patient and the operator from an overexposure of X-rays is of first importance. It goes without saying that the usual lead lining of the X-ray tube holder protects the patient and the operator from all rays except those illuminating the spot upon the fluoroscopic screen. This field of radiation should be kept as small as possible and nothing but the forceps of the operator should ever enter it while the current is on; sufficiently long forceps should be employed to keep the hands out of the direct rays. Protection of the patient and additional security for the operator is afforded by placing over the tube a filter of at least 2 mm. of aluminum, and by reducing to a minimum the time required for the X-ray observations. Onlookers not directly interested should not prolong the operation by participating in the screen work. The method is entirely safe if reasonable care is taken to minimize the time of X-ray observations. If the eyes have been properly prepared by a preliminary stay in obscurity, 1 or 2 milliamperes of current will suffice. A foot switch is essential. The X-ray current should be off every second the observer's eyes are not intent studying the screen. During early experiences, the X-ray current may be turned on and off twenty or thirty times during the operation; but after the first few cases the extraction will be accomplished during a very few moments.

BONNET METHOD

The bonnet procedure has the advantage over the foregoing method that it can be carried out in the operating room in the usual light by which the surgeon operates.

The requirements are an ordinary fluoroscopic horizontal table, or a makeshift; a fluoroscopic bonnet; and a sighting needle or pointer sufficiently

262

long to permit the hand holding it to remain outside of the zone of active X rays.

The United States Army bedside unit, which is now being adapted to general practice, affords a very convenient instrument for taking the X-ray apparatus to the operating room, providing the surgeon does not wish to take his patient to the X-ray room. An ordinary massage or nonmetallic table or a stretcher will serve the purpose. The tube-holding arm and tube of the bedside unit is placed under the table, approximately under the foreign body when the patient is in the position for operation. No effort need be made to hide the glow of the X-ray tube, as this type of X-ray operation can be carried on in the most brilliant light needed for operating purposes.

A fluoroscopic bonnet, or, in its absence, a hand fluoroscope of the ordinary type, will be needed. In the latter instance, it will be necessary to provide the radiologist with a pair of smoked spectacles. The bonnet fluoroscope, especially Dessane's, is much simpler and more convenient. As soon as the radiologist finishes his observation, the lower part of the bonnet is turned up and held in this position by springs, while a shutter of smoked glass comes down automatically in front of his eyes (fig. 156). The position of the hood thus lifted eases the weight and materially lessens the inconvenience of its use. The screen in this form of fluoroscope measures 13 by 18 cm., an area much larger than the illuminated field should ever be. For a pointer or sighting device, an ordinary urethral sound or a long forceps may be used, if a special localizing pointer is not provided.

The radiologist must put on the bonnet or a pair of smoked glasses 12 or 15 minutes before be will be needed, unless he is already engaged in fluoroscopic work, so that when called he has only to don the bonnet and step to the operating room.

For anesthesia in these cases, when a local anesthetic is not suitable, nitrous oxide gas is preferable since it is nonexplosive. The danger of an explosion of either vapor, however, has, in the writer's opinion, been considerably overestimated. Ile has seen only one case and in this no harm at all was done as the flame was instantly smothered. The danger, of course, is greater with the open drop method than with some form of rebreathing anesthetic device. The Ombrédanne anesthetic mask is very satisfactory for this purpose.

After the patient has been made ready for operation in the position in which the localization was done, the protective sterile velum is placed over him in the manner already described. When the surgeon is ready, the radiologist indicates through the sterile velum, by means of a pointer, the exact spot on the skin which lies vertically above the foreign body. While he holds the pointer in place the velum is lifted on the side next the surgeon, who places the end of a sterile forceps on the skin in the position shown by the radiologist's pointer. The bonnet and velum are lifted out of the way, the surgeon notes carefully the point indicated on the skin and cuts down vertically upon it to find the foreign body. If he does not find it at the depth he supposes to be correct, he ties the bleeding points in order to clear the field of haemostats, and asks to be shown again the spot where the vertical ray corresponding to the projectile passes through the wound. This takes but a moment on the part of

263

the radiologist and is done as often as required. The surgeon places his sterile pointer in the wound as nearly as possible above the exact center of the image of the foreign body. Correction of the position of the surgeon's forceps is made by telling him to move to the left, right, front, or back, until the correct location has been found. After the extraction procedure has been completed it will be advisable to make still another observation to insure that the whole of the foreign body has been removed.

This method will rarely fail except in badly planned operations where an insurmountable difficulty of an anatomical or physiological nature has been overlooked, or where through some accident it will be necessary to terminate the operation suddenly.

In the case of recent wounds, the surgeon will often prefer to conduct his search through the already existing wound rather than to cut down vertically upon the foreign body. Here again the bonnet will afford valuable control. especially if the tube beneath the table is susceptible of movement.

The bonnet method is particularly helpful in cases of old encapsulated projectiles or foreign bodies. By using a very small diaphragm aperture the radiologist employs the bundle of rays perpendicular to the plane of the table. When the foreign body is brought into the line of this ray and the point marked upon the skin perpendicularly over the ray, the surgeon knows if he dissects vertically downward he can not fail to find the foreign body. Ledoux-Lebard and Ombrédanne have demonstrated the special value of this method in cases of intra-osseous projectiles.

REFERENCES

(1) Buguet, Abel and Gascar: Détermination a l'aide des rayons X de la profondeur ou la siége d'un corps étranger dans les tissus. Comptes rendus hebdomadaires des séances de l'academic des sciences, Paris, March 30, 1896, cii, 786.
(2) Thompson, Elihu: Electrical Review, May, 1896.
(3) Imbert, A., and Bertin-Sans, H.: Photographies stéréoscopiques obtenues avec les rayons X. Comptes rend us hebdomadaires des séances de l'academie des sciences, Paris March 30, 1896, cii, 786.
(4) White, J. William, Goodspeed, Arthur W., and Leonard, Charles L.: Cases Illustrative of the Practical Application of the Roentgen Rays in Surgery. American Journal of the Medical Sciences, Philadelphia, 1896, n. s. cxii, No. 2, 125.
(5) Davidson, James Mackenzie, and Hedley, W. S.: A Method of Precise Localization and Measurement by Means of Roentgen Rays. Lancet, London, October 16,1897, i, 1001.
(6) Gérard (Method described by Vilain and Maffei): Procédé Géometrique de détermination des corps étrangers inclus dans les tissus. Clinique, Bruxelles, May 13, 1897, xi, 297.
(7) Levy-Dorn, Max: Ueber Methoden die Lage innerer Theile mittelst Roentgenstrahlen zu bestimmen Verhandlungen der duetschen Gesellschaft fur Chirurgie, 36th Congress, Berlin, April 22, 1897, 50.
(8) Stechow: Ueber die Verwendlung der Roentgenstrahlen bei der Armée im Frieden und im Kriege. Comptes rendus du xii Congres International de médecine, Moscou, August 19-26, 1897, v, sect. 10, Military Medicine, 128.
(9) Exner, S.: Eine Vorrichtung zur Bestimmung von Lage und Grosse eines Fremdkorpers mittelst der Roentgenstrahlen. Wiener klinische Wochenschrift, Vienna, January 7, 1897, x, 1.
(10) Remy, Ch., and Contremoulins: Nouveau perfectionnement des applications chirurgicales des rayons X. Bulletin de l'académie de médecine, Paris, March 30, 1897, xxxvii, 354.
(11) Morize: Stir un nouveau procédé détermination de la position des corps étrangers par la radiographie. Presse médicale, Paris, February 12, 1898, vi, 66.
(12) Galeazzi, R.: Ueber die Lagebestimmung von Fremdkorpen vermittelst Roentgen- strahlen. Zentralblatt fur Chirurgie, Leipzig, 1899, xxvi, No. 18, 529.
(13) Sechichaye: Étude sur la localisation des corps étrangers au moyen des rayons Roentgen. Bȃle et Genève, Georg et Compagnie, 1899.
(14) Case, James T.: History of Foreign Body Localization. American Journal of Roentgenology, New York, 1918, v, No. 3, 113.
(15) Hirtz, E.: Méthode radiographique et appareil simple pour la localisation précise et la recherche des corps étrangers. Bulletins et mémories de la societe de chirurgie de Paris, March 25, 1914, xl, 373.
(16) Henrard, Étienne: L'état actuel du radiodiagnostic des corps étrangers. Bulletins et mémoires de la societe de radiologie médicale de France, Paris, 1914, vi, No. 53, 82.
(17) Ombrédanne et Ledoux-Lebard: Localisation et extraction des projectiles. Paris, Masson et cie, 1917.
(18) Delherm, Louis, and Rousset, J.: Le répérage des projectiles. Paris, A. Maloine et fils, 1918.
(19) Nogier, T.: Localisation et extraction des projectiles de guerre. Lyon, 1918.
(20) United States Army X-Ray Manual. New York, Paul B. Hoeber, 1918, 209-291.
(21) Symington, Johnson: Cross Section Anatomy.
(22) Stein, Arthur, and Stewart, Wm. H.: Roentgen Examination of the Abdominal Organs Following Oxygen Inflation of the Peritoneal Cavity. Annals of Surgery, Philadelphia, 1919, lxx, No. 1, 95.
(23) Viallet and Tanton, J.: Plaie pénétrante de la fesse gauche avec perforation de la vessie par éclat de grenade. Retention intravesicale du projectile. Ablation. Bulletins et mémoires de la Société de chirurgie de Paris, 1916, xlii, 2836.
(24) Strohl, A.: Procédé simple pour localiser rapidement les projectiles par la radioscopie. Journal de radiologie et d'electrologie, Paris, 1916, ii, No. 3, 173.
(25) Duval, Pierre: Technique opératoire de l'extraction des projectiles sous la direction du compas de Hirtz. Revue de Chirurgie, Paris, 1916, ii, No. 1, 1.
(26) Metcalfe, James, and Keys-Wells, Ernest M.: The Anatomical Position of Localized Foreign Bodies. Lancet, London, May 27, 1916, i, 1978.