Implementazione di modelli radiobiologici per un sistema di piani?cazione di trattamento con fasci di ioni

An important aspect in the field of advanced radiotherapy with ions beams is the implementation of a Treatment Planning System (TPS) which includes the evaluation of the biological effects of these particles. The most used radiobiological models in this field are the Local Effect Model (LEM), developed by the GSI biophysics group, and the Microdosimetric Kinetic Model (MKM)adopted at NIRS. In this work we present a comparison of these models with experimental radiobiological data taken from Furusawa et al. (2000). The data includes survival curves of CHO, V79, HSG, XRS irradiated with ions with 1 < Z < 10. In these comparison the MKM shows a better agreement with the experimental data. However a limit of the standard implementation of the MKM is found in the evaluation of the Linear Quadratic beta parameter that is approximated with the beta of the x-rays survivals. We extended the MKM in order to obtain a more rigorous beta value including the influence of the non-Poissonian fluctuations. We also include in the model the effects of the variability of the cell nuclei cross section for a given cell line. The upgraded model is included in the radiobiological evaluation in the TPS for carbon ion beams that is in development by INFN (Istituto Nazionale di Fisica Nucleare).