ICRP Publication 155
Specific Absorbed Fractions for Reference Paediatric Individuals
Recommended citation
ICRP, 2023. Specific Absorbed Fractions for Reference Paediatric Individuals. ICRP Publication 155. Ann. ICRP 52(4)
Authors on behalf of ICRP
D.W. Jokisch, W.E. Bolch, B.C. Schwarz, N.E. Martinez, K.F. Eckerman, K. Kim, K.T. Griffin, W.J. Godwin, C. Lee
Abstract - The calculation of doses to organs and tissues of interest due to internally emitting radionuclides requires knowledge of the time-dependent distribution of the radionuclide, its physical decay properties, and the fraction of emitted energy absorbed per mass of the target. The latter property is quantified as the specific absorbed fraction (SAF). This publication provides photon, electron, alpha particle, and neutron (for nuclides undergoing spontaneous fission) SAF values for the suite of reference individuals. The reference individuals are defined largely by information provided in ICRP Publication 89. Some improvements and additional data are provided in this publication which define the reference individual’s source and target region masses used in the Occupational Intake of Radionuclides (OIR) and Dose Coefficients for Intakes of Radionuclides by Members of the Public series of publications. The set of reference individuals includes males and females at 0 (newborn), 1, 5, 10, 15, and 20 (adult) years of age. The reference adult masses and SAFs provided in this publication are identical to those in ICRP Publication 133 and those used in the OIR series of publications. Computation of SAF values involves simulating radiation transport in computational models which represent the geometry of the reference individuals. The reference voxel phantoms of ICRP Publication 143 are used for photon and neutron transport, and most electron transport. Alpha particle transport is not necessary for large tissue regions as the short range allows for an assumption of full energy absorption (absorbed fraction of unity) for self-irradiation geometries. Additional computational models are needed for charged particles in small, overlapping, or interlaced geometries. Stylised models are described and used for electrons and alpha particles in the alimentary and respiratory tract regions. Image-based models are used to compute SAFs for charged particles within the skeleton. This publication is accompanied by an electronic supplement which includes files containing SAFs for each radiation type in each reference individual. The supplement also includes source and target region masses for each reference individual, as well as skeletal dose–response functions for photons incident upon the skeleton.
MAIN POINTS
ICRP, 2023. Specific Absorbed Fractions for Reference Paediatric Individuals. ICRP Publication 155. Ann. ICRP 52(4)
Authors on behalf of ICRP
D.W. Jokisch, W.E. Bolch, B.C. Schwarz, N.E. Martinez, K.F. Eckerman, K. Kim, K.T. Griffin, W.J. Godwin, C. Lee
Abstract - The calculation of doses to organs and tissues of interest due to internally emitting radionuclides requires knowledge of the time-dependent distribution of the radionuclide, its physical decay properties, and the fraction of emitted energy absorbed per mass of the target. The latter property is quantified as the specific absorbed fraction (SAF). This publication provides photon, electron, alpha particle, and neutron (for nuclides undergoing spontaneous fission) SAF values for the suite of reference individuals. The reference individuals are defined largely by information provided in ICRP Publication 89. Some improvements and additional data are provided in this publication which define the reference individual’s source and target region masses used in the Occupational Intake of Radionuclides (OIR) and Dose Coefficients for Intakes of Radionuclides by Members of the Public series of publications. The set of reference individuals includes males and females at 0 (newborn), 1, 5, 10, 15, and 20 (adult) years of age. The reference adult masses and SAFs provided in this publication are identical to those in ICRP Publication 133 and those used in the OIR series of publications. Computation of SAF values involves simulating radiation transport in computational models which represent the geometry of the reference individuals. The reference voxel phantoms of ICRP Publication 143 are used for photon and neutron transport, and most electron transport. Alpha particle transport is not necessary for large tissue regions as the short range allows for an assumption of full energy absorption (absorbed fraction of unity) for self-irradiation geometries. Additional computational models are needed for charged particles in small, overlapping, or interlaced geometries. Stylised models are described and used for electrons and alpha particles in the alimentary and respiratory tract regions. Image-based models are used to compute SAFs for charged particles within the skeleton. This publication is accompanied by an electronic supplement which includes files containing SAFs for each radiation type in each reference individual. The supplement also includes source and target region masses for each reference individual, as well as skeletal dose–response functions for photons incident upon the skeleton.
MAIN POINTS
- Specific absorbed fraction (SAF) values are provided for International Commission on Radiological Protection male and female reference individuals at 0, 1, 5, 10, 15, and 20 years of age for internally emitted photons, electrons, alpha particles, and fission-spectrum neutrons associated with radionuclides which decay by spontaneous fission.
- Source and target region masses for the reference individuals consistent with these SAF values are tabulated and their origins defined.
- SAF values and source and target region masses for the adults are the same as those in Publication 133 (ICRP, 2016a) and utilised in the Occupational Intake of Radionuclides series of publications (ICRP, 2015, 2016b, 2017, 2019, 2022).
- Computational models used to obtain energy absorption data include the reference voxel phantoms of Publication 143 (ICRP, 2020b), stylised models for charged particles in intrarespiratory and intra-alimentary tract geometries, and image-based models for charged particles emitted within the skeleton.
- In forthcoming publications, the reference SAFs presented in this publication will be coupled with the nuclear decay data of Publication 107 (ICRP, 2008b) and the biokinetic models describing temporal distribution of radionuclide activity to calculate reference dose coefficients to members of the public and dose to patients from radiopharmaceuticals.
- In addition to photons, energy-dependent SAFs for electrons and alpha particles are provided, representing a significant improvement in radiation protection dosimetry compared with the non-energy-dependent SAFs in Publication 30 (ICRP, 1979).
