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A simple way of making stereoscopic chest films
440
TUBERCLiE
[July, 1932
A SIMPLE WAY OF MAKING STEREOSCOPIC CHEST FILMS. ]~y E. ZIMMERLI, M.D.]3asle, M.R.C.S.Eng, Swiss Fed. Dipl., I)~rector of 1%uc~d Sanatorium, ffelwa~.
As the division of adhesions after Jacobaeus is gradually becoming a routine method of m a n y sanatoria, their accurate localisation by stereoscopic pictures attracts more and more attention. Opinions on the value of stereo X-ray films of the chest are still differing; a few authors are enthusiastic, like Diocl6s and Azoulay in F r a n c e or Kremer and L u e d k e in G e r m a n y ; others, again, consider its merits very small (Stephani, Kaestle). Under these circumstances it is comprehensible that sanatoria with limited funds hesitate to buy one of the stereo-apparatuses with which modern industry provides us for some s The photographs which are published here m a y be cut out and examined in an ordinary stereoscope ; it will be found that they give as good a stereoscopic effect as the reproductions at present found in literature. Yet the apparatus by which these have been taken has been improvised at a total cost of ls. 6d. It consists in a sheet of ply-wood with.two hooks to hang it on the frame which takes the cassette, and of an ordinary gauze bandage to tie the patient on this wooden plate. Owing to this fixing of the chest the time between the first and the second exposure becomes irrelevant. All kinds of apparatus on the market and all improvised arrangements that have been recommended in literature are based on the idea that the two exposures should be taken within the time in which the patient can hold his breath. The latest paper on the matter by Stott and Cruikshank again emphasises the importance of minimising the interval. The attached photographs show that this is a mistaken idea, since they are all taken w i t h an average of one or two minutes' i n t e r v a l between the two exposures.
Mainly for economy's sake, for a 5acobaeus operation I have had only one-half of the chest taken. The details of our procedure are as follows : The ply-wood is fixed behind the frame which holds the cassette. Then a strap of lead rubber of the width of half the cassette is hung over the side which is not to be radiographed. Now we let the patient sit behind the wooden plate and bandage him tightly to it with an ordinary surgical dressing. The two exposures are taken with a shift of the tube of 3"5 cm. to the right and to the left of the mid-line respectively, and at a distance of 150 em. After the first exposure the patient is asked to sit quiet, the cassette is turned by 180 ~, the tube is shifted to the other side and the second exposure is taken. I owe the idea of doing only half a film to Mr. P. G. Sutton, M.S.R., of Davos. H e does the two exposures while the patient is lying on a selfmade cassette holder, which allows him to change from one-half of the cassette to the o~her within a second. Sparks and Wood refer to this cassette as the Davos model and also apply the prone position of the patient, but shift the tube at right angles to the ribs.
TUBERCLE.
Jut.Y, 1932. PLATE I.
To illustrate article, " A Simple Way of Making Stereoscopic Chest F i l m s , " by E. ZIM~RLI, l~I.D.Basle, M.R.C.S.Eng., Swiss Fed. Dipl. Face p. 440
July, 1932]
STEREOSCOPIC CHEST F~LMS
441
The prone position would keep the patient sufficiently at rest to allow of a long interval between the two exposures. B u t it has the disadvantage t h a t an effusion is spread in a fiat layer in front of the film and blurs the picture, as Sparks and Wood point out themselves. Moreover, it seems to me that upper adhesions are, in the prone position of the patient, not stretched out in such a way as to afford the best visibility. My experience agrees with that of most other authors (Gilbert, Sparks and Wood, Kremer and Luedke), that in viewing the two films it is preferable to fi~: them up as though one was looking from behind at the patient's chest. The dense shadows of the posterior part of the ribs have naturally more tendency to appear near to the observer, while the weak shadows of the rib cartilages move away. But experience has shown me that it makes no difference to the quality of the picture whether in taking the films the rays actually take the antero-posterior o r the opposite direction. For analysing the fihns we use the stereoscope viewing box of the Siemens firm which has the advantage of having double mirrors on each side, so that the images are not inverted; also even distribution of the light behind the two films and a good fusion of the two images is guaranteed by this apparatus. The photographs which are reproduced in this paper have been done in a very simple way. The two original films are photographed on one single plate of an ordinary camera. Care must be taken that the dextrograph is hung up on the left side and the 1oevograph on the right. If only a part of the whole film is to be taken, as in the examples which are reproduced here, then the two films have to be fixed so near to each other t h a t they will overlap. One then has to place a black sheet over one-half of the viewing box while the first film is taken on the other half. Then the camera is left umnoved, the black paper is put in place of the first fihn and the second film is exposed on the place where the paper was at first. The distance between the two films when being photographed is, within reasonable limits, of no importance. The eyes seem to have a great tendency to perceive in a stereoscopic way and easily compensate what is insafftcient in the geometric relation. I have tried to increase the stereoscopic effect by placing an empty plywood box of 50 cm. depth between the patient and the film. A series of such exposures gave no good results. The impression of solidity is not improved, whereas the sharpness of the image suffers. Judging the merits of stereoscopic X-ray examination on the whole, it must be said before all that the individual capability of a person for viewing solidity varies greatly, and that this factor is of m u c h more importance t h a n a great accuracy in applying the physical principles of the method. I n any case, most people have to look for a short while at a stereo X-ray before getting the stereoscopic effect. But there are people who will never get it. Parallax is only one reason that makes us perceive solidity and, probably, not the most important one. This may be realised from the mere fact that in closing one eye we see the room hardly flatter t h a n with both eyes. The geometric perspective of things around us, their
442
TUB~RCr.~
[July, 1932
fading away in the distance--what has been termed the air perspective-the distribution of shade and light on the objects and their covering one another to our view, are important factors, every one of them. I n stereoradiography all these are absent. So is also the one which is perhaps more essential than any other, viz., our own experience which has taught us since childhood that we are surrounded by three-dimensional objects and which has made us used forcibly to visualize them as such (Helmholtz). Considering all this it really seems surprising that we can get such good stereoscopic effects in X-ray work where the parallactic difference of the two objects alone can be realised. :For localising adhesions before a pneumolysis the raethod has, so far, never failed me, and I should not like to do the operation without having previously seen the stereograph. On the other hand I have, on m a n y occasions, not been able to satisfy myself as to the true nature of an annular shadow with any degree of certainty. I f the ordi,~ary film is ~ot conclusive as to there bei~g a cavity or no cavity, then the stereogra2Jh is not conclusive. On the other hand the localisation of a cavity is sometimes possible by this method ; but the value of this knowledge cannot, of course, be compared with that of an accurate localisation of an adhesion which has to be severed. CONCLUSIONS.
(1) I t is not necessary that the two exposures of a stereoscopic X-ray film should be made during the same " holding " of b r e a t h ; instead of this I find it sufficient to fix the sitting patient in position and then do the two exposures with an interval of one or more minutes. (2) F o r the reason stated above stereo-radiograms can be done with any ordinary X-ray apparatus which allows the tube to be shifted sideways. (3) A simple means of fixing the patient during the interval between the two exposures consists of a piece of ply-wood attached behind the cassette and a surgical bandage to tie the sitting patient to it. REFERENCES. [i] DiocL/~s and AZOULAY. " Les Indications des Techniques Radiologiques, &c.," Rev. Tuberc., 1931, 12, 957. [2] GILBERT, M. " La Radiographie St6r~oscopique &e.," Journ. de tTadiologie, 1926, t{}, 313. [3] I~AESTLE. " R5ntgenol. Beitrag zur Kenntnis der Tub. in den Lungen," MzTnch. reed. Woch., 1921, 68, 1617. [4] KREMER,W., and LUEDKE,W. RJn~genstereoskopie bei Lungenkrankheiten. Tuberkulose.Bibl., Nr. a0, 1931, ]3arth. [5] SPARKS, S. V., and WOOD, F. " Loealisation of Pleural Adhesions," Brit. Journ. of ~adiol., 1931, 4,592. [6] STEPHA~I,J. " La Tuberculose Pulmonar. Vue aux Rayons X.," Payor, Paris, 1928, 9.3. [7] STOTm, L. B. and CRUIeKSHAN~:, D . B . " The Stereoscopy of X-ray Shadows," Tubercle, 1931, 12, 239.
TUBERCLiE
[July, 1932
A SIMPLE WAY OF MAKING STEREOSCOPIC CHEST FILMS. ]~y E. ZIMMERLI, M.D.]3asle, M.R.C.S.Eng, Swiss Fed. Dipl., I)~rector of 1%uc~d Sanatorium, ffelwa~.
As the division of adhesions after Jacobaeus is gradually becoming a routine method of m a n y sanatoria, their accurate localisation by stereoscopic pictures attracts more and more attention. Opinions on the value of stereo X-ray films of the chest are still differing; a few authors are enthusiastic, like Diocl6s and Azoulay in F r a n c e or Kremer and L u e d k e in G e r m a n y ; others, again, consider its merits very small (Stephani, Kaestle). Under these circumstances it is comprehensible that sanatoria with limited funds hesitate to buy one of the stereo-apparatuses with which modern industry provides us for some s The photographs which are published here m a y be cut out and examined in an ordinary stereoscope ; it will be found that they give as good a stereoscopic effect as the reproductions at present found in literature. Yet the apparatus by which these have been taken has been improvised at a total cost of ls. 6d. It consists in a sheet of ply-wood with.two hooks to hang it on the frame which takes the cassette, and of an ordinary gauze bandage to tie the patient on this wooden plate. Owing to this fixing of the chest the time between the first and the second exposure becomes irrelevant. All kinds of apparatus on the market and all improvised arrangements that have been recommended in literature are based on the idea that the two exposures should be taken within the time in which the patient can hold his breath. The latest paper on the matter by Stott and Cruikshank again emphasises the importance of minimising the interval. The attached photographs show that this is a mistaken idea, since they are all taken w i t h an average of one or two minutes' i n t e r v a l between the two exposures.
Mainly for economy's sake, for a 5acobaeus operation I have had only one-half of the chest taken. The details of our procedure are as follows : The ply-wood is fixed behind the frame which holds the cassette. Then a strap of lead rubber of the width of half the cassette is hung over the side which is not to be radiographed. Now we let the patient sit behind the wooden plate and bandage him tightly to it with an ordinary surgical dressing. The two exposures are taken with a shift of the tube of 3"5 cm. to the right and to the left of the mid-line respectively, and at a distance of 150 em. After the first exposure the patient is asked to sit quiet, the cassette is turned by 180 ~, the tube is shifted to the other side and the second exposure is taken. I owe the idea of doing only half a film to Mr. P. G. Sutton, M.S.R., of Davos. H e does the two exposures while the patient is lying on a selfmade cassette holder, which allows him to change from one-half of the cassette to the o~her within a second. Sparks and Wood refer to this cassette as the Davos model and also apply the prone position of the patient, but shift the tube at right angles to the ribs.
TUBERCLE.
Jut.Y, 1932. PLATE I.
To illustrate article, " A Simple Way of Making Stereoscopic Chest F i l m s , " by E. ZIM~RLI, l~I.D.Basle, M.R.C.S.Eng., Swiss Fed. Dipl. Face p. 440
July, 1932]
STEREOSCOPIC CHEST F~LMS
441
The prone position would keep the patient sufficiently at rest to allow of a long interval between the two exposures. B u t it has the disadvantage t h a t an effusion is spread in a fiat layer in front of the film and blurs the picture, as Sparks and Wood point out themselves. Moreover, it seems to me that upper adhesions are, in the prone position of the patient, not stretched out in such a way as to afford the best visibility. My experience agrees with that of most other authors (Gilbert, Sparks and Wood, Kremer and Luedke), that in viewing the two films it is preferable to fi~: them up as though one was looking from behind at the patient's chest. The dense shadows of the posterior part of the ribs have naturally more tendency to appear near to the observer, while the weak shadows of the rib cartilages move away. But experience has shown me that it makes no difference to the quality of the picture whether in taking the films the rays actually take the antero-posterior o r the opposite direction. For analysing the fihns we use the stereoscope viewing box of the Siemens firm which has the advantage of having double mirrors on each side, so that the images are not inverted; also even distribution of the light behind the two films and a good fusion of the two images is guaranteed by this apparatus. The photographs which are reproduced in this paper have been done in a very simple way. The two original films are photographed on one single plate of an ordinary camera. Care must be taken that the dextrograph is hung up on the left side and the 1oevograph on the right. If only a part of the whole film is to be taken, as in the examples which are reproduced here, then the two films have to be fixed so near to each other t h a t they will overlap. One then has to place a black sheet over one-half of the viewing box while the first film is taken on the other half. Then the camera is left umnoved, the black paper is put in place of the first fihn and the second film is exposed on the place where the paper was at first. The distance between the two films when being photographed is, within reasonable limits, of no importance. The eyes seem to have a great tendency to perceive in a stereoscopic way and easily compensate what is insafftcient in the geometric relation. I have tried to increase the stereoscopic effect by placing an empty plywood box of 50 cm. depth between the patient and the film. A series of such exposures gave no good results. The impression of solidity is not improved, whereas the sharpness of the image suffers. Judging the merits of stereoscopic X-ray examination on the whole, it must be said before all that the individual capability of a person for viewing solidity varies greatly, and that this factor is of m u c h more importance t h a n a great accuracy in applying the physical principles of the method. I n any case, most people have to look for a short while at a stereo X-ray before getting the stereoscopic effect. But there are people who will never get it. Parallax is only one reason that makes us perceive solidity and, probably, not the most important one. This may be realised from the mere fact that in closing one eye we see the room hardly flatter t h a n with both eyes. The geometric perspective of things around us, their
442
TUB~RCr.~
[July, 1932
fading away in the distance--what has been termed the air perspective-the distribution of shade and light on the objects and their covering one another to our view, are important factors, every one of them. I n stereoradiography all these are absent. So is also the one which is perhaps more essential than any other, viz., our own experience which has taught us since childhood that we are surrounded by three-dimensional objects and which has made us used forcibly to visualize them as such (Helmholtz). Considering all this it really seems surprising that we can get such good stereoscopic effects in X-ray work where the parallactic difference of the two objects alone can be realised. :For localising adhesions before a pneumolysis the raethod has, so far, never failed me, and I should not like to do the operation without having previously seen the stereograph. On the other hand I have, on m a n y occasions, not been able to satisfy myself as to the true nature of an annular shadow with any degree of certainty. I f the ordi,~ary film is ~ot conclusive as to there bei~g a cavity or no cavity, then the stereogra2Jh is not conclusive. On the other hand the localisation of a cavity is sometimes possible by this method ; but the value of this knowledge cannot, of course, be compared with that of an accurate localisation of an adhesion which has to be severed. CONCLUSIONS.
(1) I t is not necessary that the two exposures of a stereoscopic X-ray film should be made during the same " holding " of b r e a t h ; instead of this I find it sufficient to fix the sitting patient in position and then do the two exposures with an interval of one or more minutes. (2) F o r the reason stated above stereo-radiograms can be done with any ordinary X-ray apparatus which allows the tube to be shifted sideways. (3) A simple means of fixing the patient during the interval between the two exposures consists of a piece of ply-wood attached behind the cassette and a surgical bandage to tie the sitting patient to it. REFERENCES. [i] DiocL/~s and AZOULAY. " Les Indications des Techniques Radiologiques, &c.," Rev. Tuberc., 1931, 12, 957. [2] GILBERT, M. " La Radiographie St6r~oscopique &e.," Journ. de tTadiologie, 1926, t{}, 313. [3] I~AESTLE. " R5ntgenol. Beitrag zur Kenntnis der Tub. in den Lungen," MzTnch. reed. Woch., 1921, 68, 1617. [4] KREMER,W., and LUEDKE,W. RJn~genstereoskopie bei Lungenkrankheiten. Tuberkulose.Bibl., Nr. a0, 1931, ]3arth. [5] SPARKS, S. V., and WOOD, F. " Loealisation of Pleural Adhesions," Brit. Journ. of ~adiol., 1931, 4,592. [6] STEPHA~I,J. " La Tuberculose Pulmonar. Vue aux Rayons X.," Payor, Paris, 1928, 9.3. [7] STOTm, L. B. and CRUIeKSHAN~:, D . B . " The Stereoscopy of X-ray Shadows," Tubercle, 1931, 12, 239.