Effects of Dose-rate on the Radiation Response of Rat Skin

Abstract

Skin reactions and late deformities after irradiation of the feet of anaesthetized rats with 7 MeV electrons have been measured for dose-rates between 200 rads/min and 500 krads/min. For dose-rates up to 70 krads/min, there was no alteration in the effectiveness of the radiation, which implies that there is not a rapid form of repair of sub-lethal damage in rat skin. However, when the dose-rate was increased to 500 krads/min, there was a marked decrease in effectiveness. This observation was not made when the feet were anoxic, which implies that there is oxygen depletion at the high dose-rate. For irradiation at 500 krads/min, given in aerobic conditions, the ‘break-away’ point occurred at about 2000 rads, above which the response of the skin was similar to that when it was made anoxic. It was concluded from this observation that the sensitive cells were at a pO₂ of 5–10 mm Hg.