Development of a dose distribution shifter to fit inside the collimator of a Boron Neutron Capture Therapy irradiation system to treat superficial tumours

The Kansai BNCT Medical Center has a cyclotron based epithermal neutron source for clinical Boron Neutron Capture Therapy. system accelerates proton to an energy of 30 MeV which strikes beryllium target producing fast neutrons are moderated down use. While studies in the past have shown be highly effective malignant melanoma skin, apply superficial lesions using this it is necessary shift thermal distribution so that maximum dose occurs near surface. A shifter was designed fit inside collimator further moderate increase surface and reduce underlying normal tissue. Pure polyethylene selected, Monte Carlo simulation performed determine optimum thickness slab. Compared with original beam, increased flux at skin by approximately 4 times. measured simulated central axis depth off were found good agreement. 2 cm thick water equivalent bolus, 26% obtained, would treatment time 29%. DDS safe, simple tool tumours if initially beam requires moderation maximise tissue