A Geant4-based simulation of an accelerator's head used for intensity modulated radiation therapy

We present a Geant4-based simulation, this Monte Carlo program has been developed in order to simulate the absorbed dose distribution given by a medical linac used for intensity modulated radiation therapy (IMRT). The linac geometry was input into the Monte Carlo code using the accelerator's manufacturer's specifications. We made assumptions about some parameters such as the energy and the electron radial distributions that were assumed to be Gaussian in shape. The capability of the program in evaluating dose distribution has been verified by comparison with measurements in water phantom; the comparisons were performed for percent depth dose (PDD) and for flatness at 15, 50 and 100 mm depth for various field size, for a 6 MV electron beam. The source-surface distance (SSD) was 100 cm. We show the comparisons between simulation results and experimental measurements and the software architecture.