CHANGES IN THE RELATIVE BIOLOGICAL EFFECTIVENESS (RBE) OF A 35 MEV. ELECTRON BEAM AS A FUNCTION OF TISSUE DEPTH

Abstract

Survival curves obtained by in vivo total body irradiation of young CF₁ mice indicate a change in the RBE of 35 mev. electrons as they penetrate through tissue. The results are in agreement with those of Markus and Sticinsky² and with the calculations of Haynes and Dolphin¹ in that they suggest a long plateau region of low LET followed by terminal rise. They indicate a minimal three-fold increase in the terminal portion LET as compared to the plateau region if the log-linear relationship between LET and RBE holds. The relatively large cross-section of the test object may have concealed an even higher RBE peak. Studies using a smaller test object are now in progress.