Photoneutron Source for In-Hospital BNCT Treatment: feasibility study

Some recent studies in Italy have focused on the possibility of exploiting clinical high energy electron linear accelerators, normally used in photon radiotherapy, as photo-neutrons source for in-hospital neutron medical applications. In-Hospital photo-neutron radiotherapy extends the possibilities of Boron Neutron Capture Therapy (BNCT) to external treatment of diffused tumors when other methods are not possible or not adequate. By proper material and geometry optimization, interesting fluence rates of thermalized neutrons can be made available, with minimized fast neutron and gamma backgrounds, for a fractionated type of BNCT devoted to external treatment of some specific tumors. A photoneutron converter made by high Z materials, shaped to produce a thermal beam inside an irradiation cavity and easy to install or remov could be a suitable facility for radiotherapy treatment. A first prototype has been built after a feasibility study on Beam Shaping Assembly using MCNPGN simulation code and it has been tested at some hospital high energy medical LINAC facilities. In this paper the preliminary experimental results of neutron fluence rate and neutron spectra produced by the photoconverter prototype are compared to the simulations.