Activation Analysis of Patients and Establishment of Release Criteria Following Boron Neutron Capture Therapy at Tsing Hua Open-Pool Reactor

Boron neutron capture therapy (BNCT) is a particle therapy that involves the use of boron-containing drugs and neutron irradiation for the treatment of tumors, such as head and neck cancer. Boron atoms accumulated in a tumor capture neutrons through the nuclear reaction, then generating charged particles responsible for the therapeutic action. However, other elements in the patient's tissues or metal implants are activated during the treatment. Therefore, patients emit radiation after receiving BNCT. In this study, to develop release criteria for patients who have received BNCT, patients underwent spectroscopy using calibrated high-purity germanium to identify which elements were activated during the procedure. The ambient dose equivalent rate, H* (10), was measured at the surface of a patient's treatment site and 1 m away from the patient using a plastic dosimeter. This cohort study included 84 patients and was conducted from March 2017 to February 2020. The predominant radionuclides activated during the procedures were 49Ca, 38Cl, and 24Na. According to the International Commission on Radiological Protection Publication 103, the European Commission Radiation Protection No. 194 report, and the United States Nuclear Regulatory Commission Regulatory Guide 8.39, the main criterion for the release of patients following BNCT comprises an ambient dose equivalent rate lower than 10 mu Sv/h at a distance of 1 m from the patient. All of the patients in this study exhibited a rate lower than this limit. The average ambient dose equivalent rate measured at the surfaces of the patients' treatment sites was approximately 30-50 mu Sv/h. The maximum occupational exposure of the BNCT staff from patient-emitted radiation was approximately 20 mu Sv per 20-min treatment course.