Neutron capture therapy (BNCT: Boron NCT)

Boron neutron capture therapy (BNCT) is a therapy to selectively kill tumor cells which having incorporated the boron compound, by irradiation of thermal or epithermal neutron with the reaction 10B(n, αγ) 7Li. Due to their range or energy, generated α-, γ- rays and 7Li are suitable for killing the cell (Φ10-15μm) locally. BNCT was first proposed in 1936 in US, Japan started studies in 1968 and is continuing the therapy after 1990, and after 1994, the therapy is performed in US and European countries. Targets are the brain tumors (during surgery), melanoma and parotid cancer in Japan with the 10B concentration of 20-40μg/g, thermal neutron fluence of 1-2 x 1013 n/cm2 and 1-3 hr irradiation. Dose assessments are respectively done before, during and after irradiation with phantom and simulation, with semiconductor or thermoluminescent dosimeter for γ-ray and 197Au activation for neutron and with calculation of relative biological effectiveness (RBE) absorbed dose in Gy. Reactors and accelerators are used for neutron generation. BNCT is the only one radiotherapy of the brain tumor and requires improvements of the boron compound and of irradiation system of the deep body lesion, elucidation of therapeutic effects, and establishment of the fixed procedure. (N.I.)