In-phantom two-dimensinal thermal neutron distribution for intraoperative boron neutron capture therapy of brain tumours

Yamamoto, Tetsuya*; Matsumura, Akira*; Yamamoto, Kazuyoshi ; Kumada, Hiroaki; Shibata, Yasushi*; Nose, Tadao*

The aim of this study was to determine the in-phantom thermal distribution derived from neutron beams for intraoperative boron neutron capture therapy (IOBNCT). Gold activation wires arranged in a cylindrical water phantom with (void-in phantom) or without (standard phantom) a cylinder styrene form placed inside were irradiated by using the epithermal beam (ENB) and the mixed thermal-epithermal beam (TNB-1) at the JRR-4. The thermal neutron distribution derived from both the ENB and TNB-1 was significantly improved in the void-in-phantom, and a double high dose area was formed lateral to the void. The flattened distribution in the circumference of the void was observed with the combination of ENB and the void-in-phantom. The measurement data suggest that the ENB may provide a clinical advantage in the form of an enhanced and flattened dose delivery to the marginal tissue in which residual and/or microscopically infiltrating tumor.