Validação de um modelo computacional de acelerador linear VARIAN CLINAC 2100 utilizando o código EGSnrc para utilização em dosimetria de pequenos campos.

Abstract

In this work, the Monte Carlo Method was used for simulation of radiotherapeutic clinical fields that will later be used for the small fields calibration of radiosurgery. The radiation transport code NRC's Electron Gamma Shower (EGSnrc) and its derivatives, BEAMnrc and DOSXYZnrc, was used for accelerator and water phantom construction and simulation. Three 6 MeV photons beam with dimensionsof 4x4 cm², 10x10 cm² and 20x20 cm² were simulated and their data compared with experimental values obtained in the dosimetry and calibration routine of the real accelerator modeled. The number of histories used was 109and cutoff energies, PCUT = 0.01 MeVand MeV = 0.7 ECUT. The maximum relative uncertainty found in the regions of interest was 4%. The concordance of lateral sizing of the fields remained at levels higher than 98%, while in the worst case, the doses presented concordance greater or equal 96%. Although the inaccuracies detected in the process need to be handled with care, they are inherent to the simulation method employed. This behavior coupled with its values allowed the model could be considered valid for future applications.