262 Applied Biophysics 



for measuring the angle in space of the line joining two points 

 on a patient. This takes the place of an emergent pointer, which, 

 to be of any use, must be really rigid, a difficult mechanical 

 problem at the relevant distances. Instead, the ingoing and 

 outgoing points required are marked and their angle is measured 

 directly and set on the tube. 



X-ray photography at 1,000 kilovolts on patients has served 

 as a further check on arrangements, the films obtained being 

 quite readable, and various bony markings just being visible. 

 The films are slightly improved if 2 millimeters of lead is placed 

 between the patient and the film. This tends to eliminate the 

 scatter. The softer the scatter, the more it obliterates the detail, 

 since the film response is greater for the longer wave lengths. 

 The film should be given 2 r. This technique has been particu- 

 larlv successful in carcinoma of the rectum, where a lead-loaded 

 catheter in the rectum indicates the required features. 



Conclusion 



Even with the limitation that 200 kilovolt techniques have 

 been followed, significant dififerences in favor of million-volt 

 therapy have been found in the treatment of certain cancers, 

 e.g., of maxilla and breast. There are striking differences in 

 carcinoma of the rectum, where, in at least a third of the cases 

 treated at one million volts, disappearance of the growth has 

 occurred, while at 200 kilovolts it is extremely rare for this type 

 of cancer to show any response at all.^ 



Whether the improved clinical results in the types mentioned 

 are directly due to the change in wave length of the bombarding 

 rays, or to the improved and simplified arrangements made 

 possible by the physical properties of these rays, it is impossible 

 to say, as the two effects cannot be separated. However, l)oth 

 the physical and clinical results are such that they lend support 

 to the view that a further increase in voltage to the 5 to 10 

 million-volt range, is likely to give still better clinical results. 



Acknowledgment. — The author wishes to thank Dr. N. S. 

 Finzi, director of the X-ray departments, St. Bartholomew's 



