Physics in Medicine . 9 



job is done when he states, let us say, "that for a length of 2.7 

 centimeters the dose in a certain plane does not fall below 90 

 per cent." Such a statement means little to most medical 

 radiologists, but expressed in the form that ''the 90 per cent 

 isodose surface stretches anteriorly from the lower border of 

 the hyoid bone to the upper border of the cricoid cartilage" 

 instantly brings a look of relief and gratitude. This method 

 of approach implies that the hospital physicist should be in- 

 structed in elementary anatomy, so as to be able to take a more 

 intelligent interest in the parts of the body he helps to treat, 

 as well as to be able to transmit his hard-won information in a 

 more acceptable form to his medical colleagues. The anatomy 

 taught to him should of necessity be of rather a special variety, 

 which we might describe as "geometrical anatomy." Size, 

 shape, and position are of more importance to him than structure 

 or function, which clearly lie outside his province. 



It has usually been thought that too close a reliance on physical 

 methods leads to rigid techniques and standardized dosage, 

 that the individuality of the patient is lost, and that all is sub- 

 ordinated to an inflexible regime. This is a grave error, and 

 the reverse is more nearly true. There can be no doubt that 

 variation of size, condition, and sensitivity from patient to 

 patient is of the utmost importance, but standardization of 

 technique becomes increasingly indefensible as the detailed physi- 

 cal studies provide the necessary information to enable adjust- 

 ment of technique from patient to patient to be made on a 

 rational basis. Physical studies of sufficient range tend towards 

 flexibility rather than standardization. This is an important 

 lesson for both medical man and physicist to learn, and they 

 are more likely to learn together than separately. 



Only the closest personal collaboration of radiologist and 

 physicist, only the daily discussion of common problems, and 

 the realization that the medical man has the final responsibility 

 but the physicist an indispensable interest, can solve the problem 

 of one of the most important applications of science in medicine. 

 The physicist must realize that however fascinating and im- 

 portant his more academic problems, his primary responsibility 



