Comparison of the Biological Efficiency of Fast Neutrons and Caesium Gamma-rays on ‘August’ Rats

Abstract

The R. B. E. of fast neutrons compared with caesium gamma-rays is equal to 3 on the lethality of "August" rats, and equal to 4 as measured by the mean weight drop three days after irradiation. The timing of the various reactions appears to be the same in both cases, but death after fast neutron-irradiation is mainly due to intestinal lesions and after caesium gamma-irradiation to bone-marrow lesions. Lethality does not, therefore, seem to be a very satisfactory criterion for comparing the efficiency of fast neutrons with X- or gamma-rays. Any measure in rem derived from a lethality experiment might prove a very misleading guide when applied to accidental or therapeutic neutron-irradiations in men. On the other hand, fast neutrons appear to be an ideal medium for the study of the mechanism of "intestinal irradiation death" and the digestive syndrome after non-lethal doses of radiations.