Transport calculations of the influence of physical factors on depth-dose distributions in boron neutron capture therapy.

Distributions of thermal neutron fluence and capture gamma ray absorbed dose rates were evaluated, taking into consideration various physical factors relevant to boron neutron capture therapy. The use of a larger neutron irradiation aperture was associated with an increase in thermal neutron fluence and capture gamma ray absorbed dose rates. Radiation leakage was more significant with smaller phantoms. Attenuation of thermal neutron fluence rates by 10B suggested that there was an optimal 10B concentration (less than 100 PPM) for a given tumour. Deuteration of water allowed better penetration of thermal neutrons with less capture gamma rays and is potentially applicable for the treatment of deep-seated brain tumours.