Review of Accelerator-based Boron Neutron Capture Therapy Machines

Accelerator-based BNCT (Boron Neutron Capture Therapy) facilities are being studied, developed and constructed at many laboratories and hospitals, especially in Japan. In order to provide sufficient neutron flux in the epi-thermal energy region (0.5 ~ 10 keV), an intense proton beam accelerated with a cyclotron, linear accelerator (linac) or DC accelerator up to 2.5 ~ 30 MeV is directed to lithium or beryllium targets to produce neutrons. The neutrons produced have an energy ranging from several hundred keV ~ 28 MeV, depending on the primary proton beam energy and target material, this neutron energy must be degraded to the epithermal region with a moderator system. The boron delivery drug system, patient treatment and radiation exposure planning can be the same as with conventional reactor-based BNCT. In this paper I will review the various possible technology choices being made by current projects in Japan.