Effect of irradiation history on cell survival in high dose rate implants

Points in tissue receiving the same total dose during an HDR fraction may be subjected to very different dose rate histories over the course of the treatment. Since cell kill depends on dose rate as well as total dose delivered, studies were undertaken to examine the differences in cell survival at points receiving identical HDR doses, with different irradiation histories. A linear quadratic model was used to calculate cell survival at a given total dose, with varying LQ parameters and source activity. Significant differences in survival and a relatively strong dependence on source activity were seen for cells with short repair times