Neutron and gamma dose characterization using paired-TLD method in a BNCT treatment facility

Abstract

For complex radiation fields, such as in BNCT, a method is needed to separate the neutron and gamma doses to ensure treatment efficacy and patient safety. To overcome the challenge in a mixed-radiation field, detectors with different neutron-gamma sensitivities are required.  In this study, neutron and gamma doses were measured in the BNCT treatment room using a paired thermoluminescent dosimeter (TLD). The TLD chips are irradiated in the Co-60  facility to obtain the gamma calibration factor. The neutron calibration factor was calculated using the kerma factor (F_n) method, and cadmium covers were used to determine the thermal neutron dose. The paired TLDs are irradiated with 1 MW of power across the treatment room. The spatial map showed that the neutron dose is concentrated near the beam port, while the gamma dose penetrates wider and deeper. The maximum dose in the phantom occurred at 2 cm depth with 52.5 mGy/min and 154.8 mGy/min for thermal neutron and gamma ray, respectively. These results provides a basis for more accurate dose separation and optimization of BNCT treatment planning.