Giant dipole photo-nuclear reactions generated during Linac radiotherapy are
of concern due to the undesirable neutron dose delivered to patients. Nuclear
track methodology provides an estimation of gradients of photo-neutrons
fields in radiotherapy treatments for 18 MV linear accelerators and it revealed
an unexpected behaviour around isocenter. Enhancement effects are observed
on absorbed dose due to both scattered photo-neutrons and ( ,n) reactions.
Thermal neutrons can give a dose boost if the tumour is loaded with 10B and
a new BNCT approach combined with the standard photon field is proposed.