41 Simulation of the biological effectiveness caused by 65 MeV protons (clinical beam) and carbon-ions

Abstract

Introduction In order to optimize hadron therapy treatments, not only the absorbed dose will be taken in account but the biological consequences on the irradiated cell structures will be considered as well. To achieve that, the relative biological effectiveness (RBE) is estimated to provide the information we need on how cells respond to irradiation. Here we are focusing on a 65 MeV clinical proton beam from the Antoine Lacassagne clinical center in Nice and a 4 MV carbon-ion beam from the Heavy-Ion Medical Accelerator in Chiba (Japan). To predict the said RBE, there are several biophysical models implemented by Monte Carlo codes, some of them already are in use for treatment planifications. Among them, the microkinetic model (MKM) [1] , [2] and the nanOx model are tested in this study. To address this issue, we use the GATE Monte Carlo platform to estimate the biological effectiveness. Methods Are collected survival curves from the cell lines samples according to the linear quadratic model. The cells are irradiated by a reference 250 kVp X-ray beam (delivered by the X-rad 320 X-ray system) a 65 MeV proton beam and a 4MV carbon-ion beam (passive mode), the dose being in a 0 to 10 Gy range. All the beams used to conduct the cell irradiations are entirely emulated with the version 8.0 of the GATE Monte Carlo plateform. The microdosimetric spectrums (or linear energy distribution) are then estimated and implemented to the biophysical models. Results The emulated depth dose distributions and Bragg peaks are verified and consistent with the experimental ionization chamber measurements. The MKM and the NanOx models then predict the biological effectiveness as the said predictions are compared from one model to the other. Conclusions This work lead to the implementation and the validation of the two studied biological models on the GATE simulation plateform. The same methodology will be applicated to more energetic clinical proton and carbon-ion beams.