Characteristics measurement of JRR-4 neutron beam facility; Accuracy estimation of BNCT dose calculation after change of reflector

Horiguchi, Hironori; Nakamura, Takemi  ; Motohashi, Jun ; Kashimura, Takanori; Ichimura, Shigeju; Sasajima, Fumio

Clinical trials of boron neutron capture therapy (BNCT) for malignant brain tumors and head and neck cancers have been performed at the research reactor JRR-4. BNCT is a kind of radiation therapy using a nuclear reaction with thermal neutrons and boron (B) elements administered to a patient. The design specifications of all types of reflector elements were changed due to a trouble of a reflector element in JRR-4. In the production of the new reflector elements, they were designed with the influence for the neutron beam facility by the analytical calculation. After the installation of the new reflector elements, the performance of the neutron beam facility was verified by measurement such as a free air experiment and a water phantom experiment. The calculation error used in the treatment planning for BNCT can be estimated by comparing the results of our calculation with the corresponding experimental data.