Radiation field for fission neutron enhanced baron neutron capture therapy employing fast neutron source reactor 'YAYOI'

Boron Neutron Capture Therapy (BNCT) of a localized tumor needs a sufficient thermal neutron flux at the tumor. A surgical operation including ennucleation of the main part of tumor is required for the case of thermal neutron beam from a thermal reactor because of the rapid decrease of the eutron flux in the tissue. Intermediate neutrons with little fast neutron component are only produced by a specifically designed reactor which awaits to be build. In the present paper, a positive use of fast neutron beams in addition to BNCT is proposed for treatment of some kind of localized tumors employing a fission fast neutrons from a fast neutron source reactor ''YAYOI'' of University of Tokyo which is licenced as such. Dose distributions in a water phantom located at a proposed position for two collimator cases were measured and its availability was confirmed as a possible port for therapy. (author)