Cellular repair after X or gamma irradiation determined for several “gross” criteria on animals and patients

Abstract

The shape of survival curves for several mammalian cell types has been studied by assessing the “recovered dose” (early recovery) for different sizes of the fractions. The following “gross” end-points have been used: skin reactions and intestinal death in mice, tumour regression, gross skin and mucosal reactions in patients. The increase of dose necessary to attain the chosen biological effect has been determined when a single irradiation dose D s is split into two equal doses 2 D i or when N fractions ( N × D s ) are “split” into 2 N equal “subfractions” ( N × 2 D i ); i is the interval between the two “subfractions” D i and the overall treatment time is kept constant. From the data obtained conclusions are drawn about the shape of cell survival curves in the low dose region and some implications for fast neutron therapy are discussed.