On the upper limit for the energy of epithermal neutrons for Boron Neutron Capture Therapy

The upper limit of the energy for epithermal neutrons is usually fixed to 10 keV based on the experience with spectra from reactors used until now for Boron Neutron Capture Therapy. The future use of accelerators with this therapy will provide different neutron spectra that require a more detailed study of this upper limit. Using our own Monte Carlo neutron transport code, we have calculated figures of merit on the dose depth profile to find this upper limit. Our results indicate that this upper limit could be incremented up to 15–20 keV under these new conditions. •An increase of the upper limit of the energy of epithermal neutrons for BNCT has been proposed.•A fast computer code for evaluating dose depth profiles for BNCT has been introduced.•Useful analytical parametrizations of the different dose components for a standard tissue have been obtained.•Figures of merit for different neutron energies have been calculated and their dependence on the energy has been discussed.