The advantages of employing mixed high energy x-ray and electron beams in radiation therapy.

Abstract

The chief physical problem in using beams of ionizing radiations for the treatment of patients is to secure the maximum dose to the lesion with the minimum dose to the surrounding tissue. The techniques of multiple-field therapy, arc therapy, and rotation therapy have been evolved to overcome as far as possible the poor depth dose characteristics of X-ray beams in the normal energy range. The development of high energy particle accelerators delivering electron beams and X-ray beams with better depth dose characteristics has made possible the treatment of lesions near the surface of the patient with single fields, and at the same time has simplified the treatment of deep-seated lesions. It is the purpose of this article to suggest that there are considerable further advantages to be derived from the use of combinations of high energy electron and X-ray beams in suitable proportions. The measurement of central axis depth dose curves for various field sizes for the X-ray and electron beams produced by the 15 MV electron accelerator installed at St. Bartholomew's Hospital has yielded results similar to those obtained by other workers in this field, notably by Kerst, Kock and Morrison (1943), Skaggs, Almy, Kerst and Lanzl (1948), Skaggs (1949), Schubert (1950), Laughlin, Beattie, Lindsay and Harvey (1951) and Laughlin, Ovadia, Beattie, Henderson, Harvey and Haas (1953). Figure 1 shows the central axis depth dose curves in water for both the electron and X-ray beams from the accelerator.