State-vector model for life shortening in mice after brief exposures to low doses of ionizing radiation

Abstract

A model for radiation-induced life shortening caused by late effects is presented. The model is based on the concept that life shortening from late effects is caused mainly by tumors induced by the radiation. The model is kinetic in nature and describes a two-step process that leads to the bipartition of the irradiated population into two groups: (1) those with and (2) those without radiation-induced tumors which cause life shortening. For group (1) it is assumed that the mean survival time is relatively independent of the absorbed radiation dose. For group (2) it is assumed that the mean survival time will be nearly identical to that of an unirradiated control population. Results based on the model are shown to be consistent with presently available data including curvilinear dose- response relationships after single-dose exposure to 300-kVp x-rays, 1-MeV neutrons, or 60-MeV protons; an enhancement in dose effect after fractionated exposure to fission neutrons; and a dose-sparing effect after fractionated exposure to 60Co gamma rays.