Effectiveness of continuous low dose-rate gamma-irradiation on rat skin

A skin transplantation technique has been employed for assessment of radiation-induced damage to rat skin. Shrinkage of the area of an irradiated piece of white skin was measured five months after transplantation onto brown F1 hybrid rats. The effectiveness of 137Cs γ rays at a doserate of 85 rads/hour was compared with that of 300 kV X rays applied at 40 rads/minute. Protracted irradiation provides a large sparing effect due to repair of sublethal damage. For a 90 per cent reduction of skin area, the ratio of the doses given at low and high dose-rate, respectively, is 1·8. Comparison of these results with data obtained previously for a rat rhabdomyosarcoma, indicates that protracted irradiation at low dose-rate, when compared with acute irradiations, has a larger sparing effect on skin than on the tumour.