Analysis of absorbed dose distribution in head phantom in boron neutron capture therapy

The absorbed dose rate from different reactions in a head phantom is investigated. The investigation involves both thermal and non-thermal neutrons. The calculation of absorbed dose rate was achieved by simulating the head by a slab containing a tumor-like volume. It was supposed that the elements constituting the head were H, O, N, C and Na with their natural density. Isotope 10B was introduced artificially with a concentration of 10 ppm in normal tissue and 30 ppm in tumor. The absorbed dose rate from 1H(n, γ)2H, 14N(n, p)14C, 10B(n, α)7Li, proton recoil, 1H(n, γ)2H and all (n, γ) reactions both for thermal and non-thermal neutrons were considered. The major contribution to the total absorbed dose rate at the scalp surface was obtained to be due to the recoil protons (fast neutrons dose), whereas it has the least contribution in the tumor. Apart from the boron dose, the dose resulting from hydrogen capture gamma is the highest value in the tumor compared to those from other reactions.