Radiobiological considerations; proper radiation doses calculated by LQ-model

For many years, a wide range of dose-rates have been used for brachytherapy, but there has been a move towards high dose-rate (HDR) treatment in Japan. It has been generally believed that late radiation damages should be worse for HDR compared with low dose-rate (LDR) protocol. We report the changing situations of HDR treatment with the clinical and radiobiological considerations using LQ-model. We introduce pulsed brachytherapy which is starting to be used for patients with various kinds of carcinoma, in the expectation of fair treatment result without increasing the late radiation-induced damages using HDR irradiation.