Dose Estimation in the THOR BNCT Facility Using Dual-TLD and Scintillator-On-Optical-Fiber (SOF) Methods

Purpose: The radiation field in Boron Neutron Capture Therapy (BNCT) is inherently complex due to the multiple dose compositions, primarily neutrons and gamma rays. Both components contribute to the dose delivered to the patient, making accurate dosimetric characterization essential. Additionally, mapping the spatial dose is important to monitor neutron scattering and resulting gamma distribution within the treatment room. Therefore, a robust passive and active detection method is necessary to accurately characterize the neutron and gamma dose in the treatment room. Methods: In this study, dual thermoluminescent dosimeters (TLDs) and a Scintillator-on-Optical-Fiber (SOF) detector were investigated as complementary methods for dose estimation in the Tsing Hua Open Pool Reactor (THOR) BNCT treatment room. TLD-600 and TLD-700 were used in this study. The dual-TLD method was used to estimate the neutron and gamma dose in the phantom and across the treatment room. Meanwhile, the SOF detector was used for neutron measurement and was calibrated using the dose data acquired through the dual-TLD method. Results: The maximum dose rates in the phantom are 52.5 mGy/min and 154.8 mGy/min for thermal neutron and gamma doses, respectively. The spatial map shows that higher neutron dose rates were constrained at the beam port and decreases laterally. Meanwhile, gamma dose is observed to be significantly higher across the treatment room and has a more forward scatter compared to neutron dose map. The linear correlation between the TLD and SOF measurements confirms that both detectors have comparable response to neutrons. This validates the SOF system as a reliable tool for real-time detection once it is calibrated against the TLD standard. Conclusion: The combined dual-TLD and SOF approach enabled the estimation of the spatial contributions of neutrons and gamma rays in the THOR BNCT treatment room. These findings provide dosimetric information relevant to treatment efficacy, radiation field characterization, and patient safety in BNCT applications