Depth-dose evaluation and optimisation of the irradiation facility for boron neutron capture therapy of brain tumours.

Boron neutron capture therapy (BNCT) of brain tumours was investigated using thermal neutrons generated by a middle-power research reactor such as the TRIGA-II. The spatial distributions of neutrons and gamma rays were measured using a head phantom at different collimator apertures. Total depth-dose distributions were deduced from these results and were evaluated. We also obtained an optimum condition in terms of the collimator aperture, the 10B concentration in the tumour and the ratio of 10B concentration in the tumour to that in normal tissue. We found that, under this condition, BNCT using thermal neutrons from the TRIGA-II could be successfully used to treat a deep tumour.