ICRP Publication 143: Paediatric Reference Computational Phantoms

Abstract

Abstract–This publication describes the development and intended use of a series of 10 computational phantoms representing Reference Male and Female at birth (newborn), 1 year, 5 years, 10 years, and 15 years of age, as defined in ICRP Publication 89. These phantoms have been formally adopted by the International Commission on Radiological Protection (ICRP) for use within ICRP Committee 2 in the development of age-dependent dose coefficients following the 2007 Recommendations (ICRP Publication 103). They are presented in this publication in the very same voxelised structures and tissue identification (ID) numbers as given in ICRP Publication 110 for the adult reference computational phantoms. These paediatric phantoms have been used by Task Group 90 of ICRP Committee 2 in the development of age-dependent dose coefficients representing external exposures to contaminated air, water, and soil. They have also been used by Task Group 95 of ICRP Committee 2 in the development of age-dependent specific absorbed fractions (SAFs) for internally emitted photons, electrons, alpha particles, and neutrons, in a manner similar to the SAF values for the adult given in ICRP Publication 133. These age-dependent SAF values are currently being utilised by Task Group 96 in the preparation of age-dependent dose coefficients for radionuclide ingestion and inhalation as part of the forthcoming Environmental Intakes of Radionuclides publication series which will update the dose coefficients of ICRP Publications 56, 67, 71, and 72. Section 1 summarises the main reasons for constructing these phantoms – voxel phantoms that comply with the reference anatomical characteristics of the nonadult reference individuals presented in ICRP Publication 89. Section 2 reviews the body size/shape and organ-specific specifications of the ICRP paediatric reference phantoms. Section 3 presents, in detail, the methods of their construction, which includes nine steps in their development: (1) selection of computed tomographic (CT) data; (2) segmentation of those CT images; (3) body contour and organ modelling via non-uniform rational basis spline (NURBS)/polygon mesh (PM) surfaces; (4) adjustments of outer body contour to match total body mass; (5) adjustments of individual organ values to match reference masses; (6) subdivision of the skeletal tissues; (7) voxelisation of the NURBS/PM surfaces; (8) voxel retagging for lymphatic nodes and skeletal muscle; and (9) further modifications to bring the series of paediatric phantoms into a structure identical to that originally established for the adult phantoms of ICRP Publication 110. Section 4 follows with a description of the ICRP paediatric reference phantoms, including their main characteristics, skeletal source/target regions, regional blood distribution, and phantom limitations. The publication is supported by a series of annexes. Annex A provides details on tissue ID numbers, tissue media, mass densities, and organ locations by both coordinate position and voxel count. Annex B provides a complete list of the various agedependent and gender-dependent tissue media, their phantom masses, and elemental compositions. Annexes C and D provide a listing of all source and target regions, respectively, needed for internal as well as external dosimetric applications. Annexes E and F provide depth distributions and organ pair distance distributions, respectively, in a manner similar to that provided in ICRP Publication 110 for the adult phantoms. Annex G provides cross-sectional images – sagittal, coronal, and transverse planes. Finally, Annex H gives a description of the electronic files available for download and use of each of the 10 paediatric reference computational phantoms.