Developing and validating measurement methods combining 6LiF sintered capsule and Mg2SiO4: Tb (TLD-MSO-S) for γ-ray dose evaluation at accelerator-based BNCT system

The radiation emitted from the beam aperture of the boron neutron capture therapy (BNCT) system includes not only neutrons with a wide energy range but also γ-ray, which is an undesirable dose for patients. Therefore, it is necessary to evaluate the γ-ray dose appropriately. Several methods have been proposed to evaluate the γ-ray dose in a neutron field. However, eliminating the influence of neutrons is challenging, and developing a more versatile and highly accurate measurement method is desired. We aimed to validate the γ-ray dose measurement method in a neutron field combining a commercial thermoluminescence dosimeter (TLD) named Mg2SiO4: Tb (TLD-MSO-S) and 6LiF sintered capsule for quality assurance. As a characteristic evaluation, the variation in sensitivity between TLD rods and dose linearity was determined using a medical linear accelerator. Furthermore, the perturbation and contribution of neutron dose were determined by Monte Carlo simulation, and measurements were performed at the accelerator-based BNCT system. We have found that γ-ray dose can be evaluated with an accuracy of and within ±7% between calculated and measured values and ±7% of reproducibility.