PHOTONEUTRON AND CAPTURE GAMMA DOSE CALCULATIONS FOR A RADIOTHERAPY ROOM MADE OF HIGH DENSITY CONCRETE

Abstract

Neutron and capture gamma ray dose equivalent along the maze and entrance door of a radiation therapy room made of high density concrete was calculated using analytical and Monte Carlo methods. The room geometry and the 18 MV photon beam of a Varian 2100C/D linac were simulated using MCNPX MC code. Four analytical methods including Kersey, French, McCall, and Wu-McGinley methods were used in the current study. Average difference of 13-30% was seen between analytical and MC methods along the maze for photoneutron calculations. The difference between Wu-McGinley and MC methods was about 17% for capture gamma ray calculations. It was concluded that the analytical methods overestimate both neutron and capture gamma ray dose equivalents compared to MC. Moreover, it was shown that the analytical methods can be used as conservative estimators for neutron and capture gamma calculations.