核医学与放射治疗

Comparison of the LQ and WAM Models on the Fractionation Effect in Radiation Therapy and Animal Experiments

Abstract

Masako Bando, Yosuke Onoue, Yuichi Tsunoyama, Kazuyo Suzuki, Yasutaka Takanishi, Joe Sato, Yuichiro Manabe, Takahiro Wada and Hiroshi Toki

The Linear Quadratic model (LQM) is an extended version of the linear non threshold (LNT) model, which has been used for quantitative description of radiation protection, radiation therapy and animal experiments for long time. However, the LQM encounters serious pitfalls, especially for the case of the fractionation irradiation. We propose the 'Whack a Mole' (WAM) model as a post LQM framework of the radiation and risk estimation, which includes cell exclusion effect. By introducing the time dependence, the WAM model explicitly includes not only the total dose but also the dose rate dependence. We show various important results of the WAM model for the dose rate dependence, the fractional irradiation effect, and the spontaneous decrease effect on mutation frequency. As an application of the WAM model, we apply the WAM model to the mega mouse experimental data taking into account the delay time of mating after irradiation.