Energy Correction Factors for Silicon Semiconductor Dosimeter in Adult-male Phantom for Accurate Measurement of Organ Doses

Abstract

Metal oxide semiconductor field effect transistor (MOSFET) dosimeters are used to measure radiation dose in various medical applications and radiation safety. The advantage of the MOSFET dosimeter is that it is very small and provides practically real-time reading. However, given the fact that it is made mainly of silicon and epoxy, which are not ideally tissue equivalent, the MOSFET dosimeter shows some energy dependence for low-energy photons and will overestimate the energy deposition or absorbed dose in tissue when it is used in a phantom, due to the existence of scattered low-energy photons in the phantom. The present study determined, by Monte Carlo simulations with MCNPX, the relative response of the MOSFET dosimeter to the tissue dose, and thereby the energy correction factors, at various dosimeter locations in the ATOM adult-male phantom, in order to be able to accurately measure organ and tissue doses. The calculated values of relative response were 1.0-1.2 and 1.0-1.1 for 0.662 MeV and 1.25 MeV photons, respectively, which shows that if we do not use appropriate correction factors, the measurement of an organ dose could be overestimated by 10-20%, depending on the measurement condition. The result in study also shows that the energy correction factors are not very sensitive to the detailed energy spectrum of the photon field, and that the energy correction factors determined from the 0.662 MeV and 1.25 MeV photons can be used in the radiation fields in nuclear power plants without significant errors.