Recommended citation
ICRP, 2010. Conversion Coefficients for
Radiological Protection Quantities for External Radiation Exposures.
ICRP Publication 116, Ann. ICRP 40(2-5).
Authors on behalf of ICRP
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.
© 2011 Published by Elsevier Ltd.
Keywords: External radiation; Conversion coefficients; Effective dose; Skeletal dosimetry .
AUTHORS ON BEHALF OF EHALF OF ICRP N. PETOUSSI-HENSS, W.E. BOLCH, K.F. ECKERMAN, A. ENDO, N. HERTEL, J. HUNT, M. PELLICCIONI ELLICCIONI, H. SCHLATTL CHLATTL, M. ZANKL
References
ICRP, 1996. Conversion coefficients for use in radiological protection against external radiation. ICRP Publication 74. Ann. ICRP 26(3/4).
ICRP, 2002. Basic anatomical and physiological data for use in radiological protection: reference values. ICRP Publication 89. Ann. ICRP 32(3/4).
ICRP, 2007. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37(2–4). I
ICRP, 2009. Adult reference computational phantoms. ICRP Publication 110. Ann. ICRP 39(2).
ICRU, 1998. Conversion Coefficients for use in Radiological Protection Against External Radiation. ICRU Report 57. International Commission on Radiation Units and Measurements, Bethesda, MD.
Key Points
This report presents reference conversion coefficients for effective dose and organ absorbed doses for various types of external exposures, calculated following the 2007 Recommendations of the International Commission on Radiological Protection (ICRP, 2007).
The phantoms used for the calculations were the official computational models of ICRP (2009) representing Reference Male and Reference Female (ICRP, 2002, 2007). These reference computational models are based on computed tomographic data of real people, and hence are digital three-dimensional representations of human anatomy.
The radiations 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. These energies are kinetic energies.
Unlike the work reported previously in ICRP Publication 74 (ICRP, 1996) and ICRU Report 57 (ICRU, 1998), in which published values of conversion coefficients were used to establish reference values, the organ dose conversion coefficients given here were calculated 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 radiation transport codes, such as EGSnrc, FLUKA, GEANT4, MCNPX, and PHITS.
The conversion coefficients tabulated in 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.
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 (ICRP, 1996) and ICRU Report 57 (ICRU, 1998), but they do not extend to the higher energies considered in the present report.
References
ICRP, 1996. Conversion coefficients for use in radiological protection against external radiation. ICRP Publication 74. Ann. ICRP 26(3/4).
ICRP, 2002. Basic anatomical and physiological data for use in radiological protection: reference values. ICRP Publication 89. Ann. ICRP 32(3/4). 13
ICRP, 2007. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37(2–4). ICRP, 2009. Adult reference computational phantoms. ICRP Publication 110. Ann. ICRP 39(2).
ICRU, 1998. Conversion Coefficients for use in Radiological Protection Against External Radiation. ICRU Report 57. International Commission on Radiation Units and Measurements, Bethesda, MD.
Executive Summary
(a) The purpose of this report is to present fluence to dose conversion coefficients for effective dose and organ absorbed doses for various types of external exposures, consistent with the 2007 Recommendations of the ICRP (ICRP, 2007). For this purpose, the official ICRP/ICRU computational models (ICRP, 2009) representing Reference Male and Reference Female (ICRP, 2002) were used, in conjunction with Monte Carlo codes simulating the transport of radiation within the human body. The ICRP/ICRU reference computational phantoms are hereafter referred to as the ‘reference phantoms’.
(b) The externally incident radiations and kinetic 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.
(c) In order to calculate the dose conversion coefficients, simulations were performed to evaluate the absorbed dose to each organ within the reference phantoms using the following well-established Monte Carlo codes: EGSnrc (Kawrakow et al., 2009), MCNPX (Waters, 2002; Pelowitz, 2008), PHITS (Iwase et al., 2002; Niita et al., 2006, 2010), FLUKA (Fassò et al., 2005; Battistoni et al., 2006), and GEANT4 (GEANT4, 2006a,b). The fluence to effective dose conversion coefficients were then derived from the organ dose conversion coefficients, the radiation weighting factor wR and the tissue weighting factor wT following the procedure described in ICRP Publication 103 (ICRP, 2007).
(d) 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.
(e) The organ absorbed dose conversion coefficients were calculated specifically for this report by members of the Task Group. For quality assurance purposes, selected data sets for given radiations and irradiation geometries were generated by different members of the DOCAL Task Group using the same reference computational phantoms but different Monte Carlo codes. Reference values were then determined from the individual data through a procedure that included averaging, smoothing, and data fitting where necessary. The resultant data sets are the ICRP/ICRU reference values intended for use in radiological protection control, and thus they are fixed by convention and are not subject to uncertainties. They are hereafter referred to as ‘reference values’.
(f) 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, allowing for a more detailed representation of the eye than afforded by the ICRP/ICRU voxel phantoms due to the limitations on eye structure voxel resolution (ICRP, 2009).
(g) Part of the work of the Task Group involved skeletal dosimetry and the determination of dose–response functions (DRFs) for photons and neutrons. The use of DRFs would compensate for the limited spatial resolution of the voxel geometry of the phantoms, which does not allow the exact fine structure of trabecular spongiosa to be resolved, as well as for the dose enhancement of photo-electrons and the dose depression of recoil protons as they are produced in the bone trabeculae and marrow cavities, respectively, by incident photons and neutrons. However, for the estimation of absorbed doses in the skeletal tissues employed in this report, a simplified method of skeletal dosimetry was applied: absorbed dose to active marrow and endosteum were taken conservatively as the absorbed dose to spongiosa in each individual bone site, and skeletal-averaged absorbed doses to these tissues were taken as the mass weighted average of the regional spongiosa absorbed dose. For the sake of consistency, this method was applied for all particles. It is noted that for incident charged particles, there are no significant mechanisms for dose enhancement or dose depression, and thus skeletal response functions for externally incident particles other than photons and neutrons are not provided in this report.
(h) The conversion coefficients for the adult male and female reference computational phantoms are compared with their corresponding values given in reports of a Joint ICRP/ICRU Task Group, published as ICRP Publication 74 (ICRP, 1996) and ICRU Report 57 (ICRU, 1998). Contributing factors for any differences between these sets of conversion coefficients are discussed in terms of both the changes in phantoms employed for the simulations, and changes in both radiation and tissue weighting factors seen between the recommendations given in ICRP Publication 60 (ICRP, 1991) and those given in ICRP Publication 103 (ICRP, 2007). One of the issues addressed by the Task Group was the extent to which the operational quantities, as currently defined, adequately represent the protection quantities and provide a satisfactory basis for most measurements for radiological protection against external radiation.
(i) For that purpose, ratios of the effective dose to the operational quantities given in ICRP Publication 74 (ICRP, 1996) are plotted for photons (10 keV–10 MeV), electrons (2–10 MeV), and neutrons (0.001 eV–200 MeV). It is concluded in this report that, ambient dose equivalent, H*(10), continues to provide a reasonable assessment of the effective dose under charged-particle equilibrium for photons. For electrons, H*(10) gives a reasonable estimate of the effective dose up to 10 MeV. For neutrons, H*(10) overestimates the effective dose or gives a reasonable approximation of this quantity up to ~40 MeV.
(j) Chapter 1 provides an introduction, and Chapter 2 gives a brief description of the quantities used in radiation protection for external dosimetry, as currently defined.
(k) Chapter 3 describes the main aspects of the simulations. It includes a brief summary of the ICRP voxel computational phantoms employed in the calculations and graphical displays of the irradiation geometries considered. The features of the various Monte Carlo codes are also briefly described. The method of skeletal and skin dosimetry employed for this report is highlighted.
(l) Chapter 4 briefly presents the calculation parameters employed and a short analysis of the obtained organ and effective dose conversion coefficients. Existing differences between the male and female sets of coefficients are highlighted, and some comparisons with the data of ICRP Publication 74 (ICRP, 1996) are presented and discussed.
(m) Chapter 5 compares effective dose with H*(10) and Hp(10). Furthermore, dose to the lens of the eye vs personal dose equivalent Hp(3) and directional dose equivalent H0 (3) is also presented. As recommended data are not available for all of these operational quantities, additional comparisons are made using data reported in the literature following the release of ICRP Publication 74 (ICRP, 1996).
(n) Annex A gives the reference conversion coefficients for the effective dose for all particles and irradiation geometries.
(o) Annexes B and C present reference fluence to absorbed dose conversion coefficients for photons and neutrons, respectively, for those organs for which tissue weighting factors are assigned in ICRP Publication 103 (ICRP, 2007) (red bone marrow, colon, lungs, stomach, breast, stomach wall, gonads, bladder wall, liver, oesophagus, thyroid, endosteum, brain, salivary glands, and skin), as well as for the remainder tissues. The organ absorbed dose conversion coefficients are given separately for the adult male and female models.
(p) Full tables for all particles and organs mentioned above, and for the 14 tissues comprising the remainder tissues (adrenals, extrathoracic region, gall bladder, heart, kidneys, lymphatic nodes, muscle, oral mucosa, pancreas, prostate, small intestine, spleen, thymus, and uterus), are provided in the CD ROM accompanying this report.
(q) Annexes D and E present photon and neutron DRFs, respectively. These functions, when convolved with the scoring of energy-dependent photon or neutron fluence within the spongiosa and medullary cavities of the reference voxel phantoms, permit more refined estimates of active marrow and endosteum dose on a bone-specific basis, and within energy ranges in which secondary charged-particle equilibrium is not fully established at the microscopic level of the marrow cavities. Annex D also provides values of µen/q ratios and dose enhancement factors for red bone marrow and endosteum as needed when applying the three-factor method of skeletal dosimetry (see Section D.2 of Annex D).
(r) Annex F describes the simulations for assessing the absorbed dose to the lens of the eye for photons, electrons, and neutrons, as calculated using a stylised model of the head and eye, for some irradiation geometries.
(s) Annex G discusses the special considerations for skin dosimetry as relevant to stochastic effects and tissue reactions, and gives localised skin-equivalent dose conversion coefficients for electrons and alpha particles.
(t) Annex H gives fluence to effective dose conversion coefficients for an additional geometry (superior hemisphere semi-isotropic irradiation) approximating the conditions typically seen in aircraft crew dosimetry.
(u) Annex I briefly describes the methods used to define the reference data of dose conversion coefficients from the original calculated data sets determined by different Monte Carlo codes.
(v) Finally, Annex J provides a user guide for the CD ROM accompanying this report.
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