Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures
ICRP Publication 116Ann. ICRP 40(2-5), 2010
N. Petoussi-Henss, W.E. Bolch, K.F. Eckerman, A. Endo, N. Hertel, J. Hunt, M. Pelliccioni, H. Schlattl, M. Zankl
Abstract - This report gives fluence to dose conversion coefficients for both effective dose and organ absorbed doses for various types of external exposures, consistent with the 2007 Recommendations of the ICRP. These coefficients were calculated using the official ICRP/ICRU computational phantoms representing the Reference Adult Male and Reference Adult Female, in conjunction with Monte Carlo codes simulating the transport of radiation within the human body such as EGSnrc, FLUKA, GEANT4, MCNPX, and PHITS.
The incident radiations and energy ranges considered were external beams of mono-energetic photons of 10 keV–10 GeV, electrons and positrons of 50 keV–10 GeV, neutrons of 0.001 eV–10 GeV, protons of 1 MeV–10 GeV, pions (negative/positive) of 1 MeV–200 GeV, muons (negative/positive) of 1 MeV–10 GeV, and helium ions of 1 MeV/u–100 GeV/u.
For the simulations, idealised whole-body irradiation geometries were considered. These included unidirectional broad parallel beams along the antero-posterior, postero-anterior, left lateral and right lateral axes, and 360° rotational directions around the phantoms’ longitudinal axis. Fully isotropic irradiation of the phantoms was also considered.
Simulations were performed specifically for this report by members of the Task Group. For quality assurance purposes, data sets for given radiations and irradiation geometries were generated by different groups using the same reference computational phantoms but different Monte Carlo codes.
From the simulations, the absorbed dose to each organ within the reference phantoms was determined. The fluence to effective dose conversion coefficients were derived from the obtained organ dose conversion coefficients, the radiation weighting factor wR and the tissue weighting factor wT, following the procedure described in ICRP Publication 103.
The operational quantities for photons, neutrons, and electrons continue to provide a good approximation for the conversion coefficients for effective dose for the energy ranges considered in ICRP Publication 74 and ICRU Report 57, but not at the higher energies considered in the present report.
The conversion coefficients obtained for this report represent the ICRP/ICRU reference values. They were established using various original data sets with the application of averaging, smoothing, and fitting techniques. They are partly tabulated in annexes, and fully tabulated in an accompanying CD in ASCII format and Microsoft Excel software.
Separate Monte Carlo simulations were made to determine the absorbed dose to the lens of the eye for incident photons, electrons, and neutrons using a stylised model of the eye. Similarly, localised skin-equivalent dose conversion coefficients for electrons and alpha particles are given as derived by Monte Carlo calculations simulating the transport of a normally incident, parallel beam on a tissue-equivalent slab.
Additionally, photon and neutron dose–response functions are given in this report, defined as the absorbed dose per particle fluence. Their use would compensate for the limited spatial resolution of the voxel geometry, as well as for dose enhancement or dose depression at the microscopic level of the marrow cavities.