Doses to patients from photo-neutrons emitted in a medical linear accelerator

Abstract

Study of doses to patients from emitted photo-neutrons in a medical linear accelerator (Varian 2100C) was carried out. Dose calculation was performed using Monte Carlo Geant4 code. The model was used to calculate the neutron fluence, as a function of the neutron energy inside the treatment room to estimate the effective dose to patients. The ambient dose equivalent versus field size for patients is reported in this study. The ambient dose equivalent using 1×1 cm2 field size, at isocenter and x-ray modes of 20, 18, 15 and 10 MV, was found to be 1.85, 1.79, 0.61, and 0.06 mSv.Gy-1, respectively. The mean energies of emitted photo-neutrons were 0.48, 0.44, 0.40, and 0.16 MeV at x-ray modes, of 20, 18, 15, and 10 MV, respectively. © 2009 Springer-Verlag.