Why the Film Size?

Abstract

THE question proposed may appear of minor significance compared to the many important problems of roentgenology. However, each roentgenologist has, in the course of the activities of his own practice, many times wondered, Why the film size? The physical dimensions of the x-ray film currently manufactured for our purpose appear to have followed the standard sizes used for generations in the photographic industry. Upon investigation, no other reason could be discovered. All have experienced the dissatisfaction of being unable to obtain a demonstration of the entire barium-filled colon on one film, and, on the other hand, it is frequently observed that the lower third of the chest film is useless from a diagnostic standpoint, and, therefore, wasted. The films now in use are occasionally too short for demonstration of the entire urinary tract on one film, presenting difficulty in proper positioning, while at the same time there is considerable waste in the width of the film. The present sizes are poorly adapted to skulls, long bones, etc. Why not a change to closer conformity to anatomy? While perfection is not to be expected, we believe that some stimulus is necessary toward the study of more suitable film dimensions. Mindful of the requisite changes of radiographic equipment (cassettes, hangers, tanks, etc.) which would be involved, we are advancing the following computations for the possible consideration of the various national roentgen societies, in an attempt to initiate a movement which might gradually but eventually lead to obtaining more satisfactory supplies to the advantage of the patient and the roentgenologist. Offhand, one immediately anticipates tremendous changes in equipment but on further thought it may be noted that for a time the only serious difficulties would be for a new size for the colon, about 3 per cent of the work in certain x-ray departments, and which could be avoided by a method to be described later. Those processing systems with insert tanks may be used with little change. Films smaller than those used at present may be continued in service by using frames in cassette-changers and holders. It is with reluctance that any set of sizes is suggested at this time, realizing, as we do, that no set of sizes will ever prove perfect in all cases. For the purpose of instigating further thought on these lines, a table of suggested sizes is offered. In order to secure some basis for computation, an analysis of the diagnostic limits of the usual anatomic roentgen shadows was made in a series of routine adult cases in Kings County Hospital, Brooklyn, N. Y. Chest Mensuration Series A.—Five hundred consecutive adults, with an unselected film-target distance (36 to 72 inches). The axial diameter (vertical diagnostic limit) was taken as the mid-line distance on the film from the level of the upper border of the first dorsal vertebra to the intersection with the transverse diameter, as described in Table I.