Evaluation of neutron spectra and dose equivalent from a Varian 2100C/D Medical Linear Accelerator: Monte Carlo simulation and a literature review

Abstract

In this study was carried out a review according to experimental and Monte Carlo studies in the literature on the neutron production from 18 MV, Varian 2100C/D linac. The effects of these neutrons were investigated on the total fluence, the energy spectra, and the dose equivalent. These factors were calculated as a function of depth and the radiation field size by simulation of linac head using of MCNPX2.6.0 code. The neutron strength was found equal to 1.23 1012 nGy1.The results showed that with increasing the field size from 5 5 to 40 40 cm2, the neutron fluence and dose equivalent in the water phantom rose to the maximum value for 25 25 cm2 field (3.05 107 ncm2Gy1 and 3.14 mSvGy1 respectively) and then decreased with increasing the field size. According to the results, the magnetite-steel, ordinary, and limonitesteel concrete walls significantly increased the neutron dose equivalent for about 27.4%, 17.2%, and 13.5%, respectively.