A consistent set of neutron kerma coefficients from thermal to 150 MeV forbiologically important materials

Neutron cross sections for nonelastic and elastic reactions on a range of e lements have been evaluated for incident energies up to 150 MeV. These cros s sections agree well with experimental cross section data far charged-part icle production as well as neutron and photon production. Therefore they ca n be used to determine kerma coefficients for calculations of energy deposi tion by neutrons in matter. Methods used to evaluate the neutron cross sect ions above 20 MeV, using nuclear model calculations and experimental data, are described. Below 20 MeV, the evaluated cross sections from the ENDF/B-V I library are adopted. Comparisons are shown between the evaluated charged- particle production cross sections and measured data. Kerma coefficients ar e derived from the neutron cross sections, for major isotopes of H, C, N, O , Al, Si, P, Ca, Fe, Cu, W, Pb, and for ICRU-muscle, A-150 tissue-equivalen t plastic, and other compounds important for treatment planning and dosimet ry. Numerous comparisons are made between our kerma coefficients and experi mental kerma coefficient data, to validate our results, and agreement is fo und to be good. An important quantity in neutron dosimetry is the kerma coe fficient ratio of ICRU-muscle to A-150 plastic. When this ratio is calculat ed from our kerma coefficient data, and averaged over the neutron energy sp ectra for higher-energy clinical therapy beams [three p(68)+ Be beams, and a d(48.5) + Be beam], a value of 0.94+-0.03 is obtained. Kerma ratios for w ater to A-150 plastic, and carbon to oxygen, are also compared with measure ments where available. (C) 1999 American Association of Physicists in Medic ine.