Kerma from neutron-induced spallation in tissue

Spallation kerma factors were calculated for 12C and 16O irradiated with neutrons between 40 and 100 MeV. Spallation kerma arises from secondary charged particles 6<=A<=15 following n-12C and n-16O reactions. The method of calculation was based on existing experimental data for proton-induced reactions, which were used to represent neutron-induced reactions. The most complete set of experimental data was for 16O irradiated at 50, 55, 65 and 75 MeV giving energy spectra for spallation fragments. A Fermi break-up model with a preceeding Monte Carlo pre-equilibrium decay step was used in conjunction with the available experimental data. Kerma from densely-ionizing 16O spallation (A>=6) was calculated to be 28 to 48% of the 1H kerma for tissue irradiated with neutrons between 40 and 100 MeV, respectively. The corresponding 12C spallation kerma was calculated to be approximately 3% of the 1H kerma in this energy range. (Auth.)