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Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures * If the monitoring devices are not designed to measure H 0 (3, X) or H p (3), H 0 (0.07, X) and H p (0.07) may be applied.

Dose coefficients for assessment of internal exposures to radionuclides are radiological protection quantities giving either the organ equivalent dose or effective dose per intake of radionuclide following ingestion or inhalation. In the International Commission on Radiological Protection’s (ICRP) Occupational Intakes of Radionuclides (OIR) publication series, new biokinetic models for distribution of internalised radionuclides in the human body are presented as needed for establishing time-integrated activity within organs of deposition (source regions). This series of publications replaces Publications 30 and 68 (ICRP, 1979, 1980, 1981, 1988, 1994b). In addition, other fundamental data needed for computation of the dose coefficients are radionuclide decay data (energies and yields of emitted radiations), which are given in Publication 107 (ICRP, 2008), and specific absorbed fraction (SAF) values – defined as the fraction of the particle energy emitted in a source tissue region that is deposited in a target tissue region per mass of target tissue. This publication provides the technical basis for SAFs relevant to internalised radionuclide activity in the organs of Reference Adult Male and Reference Adult Female as defined in Publications 89 and 110 (ICRP, 2002, 2009). SAFs are given for uniform distributions of mono-energetic photons, electrons, alpha particles, and fission-spectrum neutrons over a range of relevant energies. Electron SAFs include both collision and radiative components of energy deposition. SAF data are matched to source and target organs of the biokinetic models of the OIR publication series, as well as the Publication 100 (ICRP, 2006) Human Alimentary Tract Model and the Publication 66 (ICRP, 1994a) Human Respiratory Tract Model, the latter as revised within Publication 130 (ICRP, 2015). This publication further outlines the computational methodology and nomenclature for assessment of internal dose in a manner consistent with that used for nuclear medicine applications. Numerical data for particle-specific and energy-dependent SAFs are given in electronic format for numerical coupling to the respiratory tract, alimentary tract, and systemic biokinetic models of the OIR publication series.

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As most readers will already know, the 2007 Recommendations of the International Commission on Radiological Protection (Publication 103; ICRP, 2007) set out the foundations of the current system of radiological protection. Now 13 years old, most international guidance and many national regulations relating to radiological protection are based on Publication 103. An important new feature in the 2007 Recommendations was a change in the way that doses from internal and external sources of ionising radiation were calculated. Previously, relatively simple mathematical models of the human body were used to calculate how energy from exposure to radiation is deposited in the various organs and tissues. With Publication 103 (ICRP, 2007), more sophisticated reference computational phantoms based on medical tomographic images replaced the simpler models. Priority was given to developing reference computational phantoms for the adult male and female, as these are needed to calculate doses related to occupational exposure. These two phantoms, presented in Publication 110 (ICRP, 2009), are based on digitised medical image data of real people whose body height and mass were close to the reference data. The result was voxel (three-dimensional pixel) phantoms consistent with the reference anatomical and physiological parameters for males and females laid out in Publication 89 (ICRP, 2002). The enormity of the effort and specialised skills needed to develop these phantoms may not be immediately obvious. Adjustment of the medical imaging data to match the reference parameters and a suitable posture was painstaking, as was the segmentation of the phantom into individual organs and tissues. These reference phantoms were used to develop the dose coefficients for internal occupational exposure published in the Occupational Intakes of Radionuclides series of publications (ICRP, 2015, 2016, 2017, 2019), and the dose conversion coefficients for external exposures in Publication 116 (ICRP, 2010). The current publication completes the reference computational phantom family, so that doses to non-adults can also be calculated. It is a large family: in addition to the two adult phantoms are 10 computational phantoms representing the Reference Male ß 2020 ICRP. Published by SAGE.