Monte Carlo Simulation of Photoneutron Dose in Radiotherapy Room as A Function of Gantry Angles

Using bremsstrahlung photon is one of the principal means to treat cancer. Bremsstrahlung photons are created in medical LINAC and the interaction of bremsstrahlung photon with the heavy nuclei that constitute the linac head shielding is the main process of neutron production inside the treatment rooms. The threshold of the neutron production for those materals is about 10 MeV. As the neutron is more dangerous than photon it is important to determine neutron dose during radiotherapy treatment. The neutron distribution depends on some parameters such as gantry angle. In this study neutron dose rate has been simulated as a function of gantry angle.