Characterization of acrylic phantom for use in quality assurance of BNCT beam output procedure.

The accelerator-based boron neutron capture therapy (BNCT) system has been approved for specific cases covered by health insurance, and clinical trials for new cases in Japan are currently being conducted on other systems. Owing to the progress of accelerator-based BNCT, the operation of medical physics must be rendered more efficient. A water phantom is used for the quality assurance (QA) of the BNCT beam output procedure; however, a solid phantom is preferred for routine QA because of its ease of use. Additionally, because water phantoms cannot be readily used in some facilities owing to structural problems, solid phantoms are preferred for unified measurements at different facilities to compare beam outputs. In this study, we perform irradiation tests using an acrylic phantom and verify that an acrylic phantom can be used for QA. The distribution of thermal neutron flux and gamma-ray dose rate inside the acrylic phantom are evaluated through experiments and simulations. The results indicate that the acrylic phantom is suitable for routine QA and for comparing beam outputs among different systems. In the future, the same irradiation tests will be conducted at other facilities.