ABSTRACT
This chapter reviews the variety of factors governing dose-rate and dose fractionation effects at the cellular level, with a particular emphasis on the repair of sublethal radiation damage, and the potential relevance of these factors for radiotherapy. At the present time experimental data on dose fractionation and dose-rate effects as they relate to radiotherapy can be viewed and analyzed within the framework of either model relating to the origin of survival curve shoulders. The repair of sublethal damage during the course of a protracted irradiation is a very important factor governing the dose-rate effect, but it is the only factor. The shape of the acute, high dose-rate, survival curve shoulder would be altered by this component and would limit the dose-rate effect due to repair as discussed by Oliver. Mitchell et al. used plateau phase cultures to reduce the effect of cell cycle redistribution on the dose-rate effect for continuous irradiation.
