Response of jejunal mucosa to fractionated doses of neutrons or γ-rays

Abstract The RBE n + γ/γ of fast neutrons produced by the 9 Be( d,n ) 9 B reaction ( E d = 50 MeV) relative to 60 Co γ-rays for killing of jejunal crypt stem cells has been measured over a wide range of doses beginning at 400 rad of γ-rays, and extending to doses as high as 1600 rad. Dose-equivalent values for recovery as a function of the size of the dose-per-fraction have been measured. When γ-ray doses up to about 400 rad are given, about 60% of the dose is “recovered”. With neutron doses of 100–200 rad, the recovered dose amounts to only about 13% of the given dose.