MONTE CARLO SIMULATION OF 6, 10 AND 18 MV PHOTON BEAM DOSE DISTRIBUTION IN A BRAIN TUMOR

This study aimed to obtain the absorbed dose distribution in a heterogeneous head simulator object where a brain tumor of 2 cm in diameter was located. Materials equivalent to the head and tumor were created. For head and tumor simulation, elemental composition (H, C, N, O, and others) and mass density & rho; respectively were used. X-ray spectra of 6, 10 and 18 MV were used for the exposures, projecting a field of 3x3 cm2 to the tumor, with an isocentric source distance of 100 cm. Monte Carlo simulations were done with PENELOPE v.2008 code. The results show that the maximum dose to the skin is 32 %, 20 % and 14 %, the maximum dose to the skull is 88 %, 74 % and 62 %, and the maximum dose to the tumor is 62 %, 67 % and 73 %, for energies of 6, 10 and 18 MV respectively. The maximum dose received by the skin and skull tissues decreases with increasing energy, while the dose in the tumor increases with increasing energy.