Draft Report for Consultation: Adult Mesh-type Reference Computational Phantoms
The draft Adult Mesh-type Reference Computational Phantoms is now available for public consultation. We welcome comments from individuals and organisations. The draft document can be downloaded from the ICRP website. Comments must be submitted through the ICRP website no later than December 14, 2018.
Abstract
Following the issuance of new radiological protection recommendations in Publication 103 (ICRP, 2007), the Commission released, in Publication 110 (ICRP, 2009), the adult male and female voxel-type reference computational phantoms to be used for the calculation of the reference dose coefficients for both external and internal exposures. While providing more anatomically realistic representations of internal anatomy than the older stylised phantoms, the voxel phantoms have their limitations, mainly due to voxel resolution, especially with respect to small tissue structures (e.g. lens of the eye) and very thin tissue layers (e.g. stem cell layers in the stomach wall mucosa and intestinal epithelium).
This report describes the construction of the adult mesh-type reference computational phantoms (MRCPs) that are the modelling counterparts of the Publication 110 voxel-type reference computational phantoms. The MRCPs include all source and target regions needed for estimating effective dose, even the μm-thick target regions in the respiratory and alimentary tract, skin, and urinary bladder, thereby obviating the need for supplemental stylised models. The MRCPs can be directly implemented into Monte Carlo particle transport codes for dose calculations, i.e. without voxelisation, fully maintaining the advantages of the mesh geometry.
Dose coefficients (DCs) of organ dose and effective dose and specific absorbed fractions (SAFs) calculated with the MRCPs for some external and internal exposures show that − while some differences were observed for small tissue structures and for weakly penetrating radiation − the MRCPs provide the same or very similar values as the previously published reference DCs and SAFs for most tissues and penetrating radiations; consequently, the DCs for effective dose, i.e. the fundamental protection quantity, were found not to be different. The DCs of Publications 116 (ICRP, 2010) and the SAFs of Publication 133 (ICRP, 2016) thus remain valid.
To demonstrate deformability of the MRCPs in this report, the phantoms were transformed to construct phantoms that represent the 10th and 90th percentiles of body height and weight for the Caucasian population. The constructed non-reference phantoms were then used to calculate DCs for industrial radiography sources near the body, which can be used to estimate organ doses of workers accidentally exposed by these sources, and which reflect the stature of the exposed worker. The MRCPs of this report were also transformed to phantoms that represent different postures (walking, sitting, bending, kneeling, and squatting), which were then used to evaluate variations in the DCs from the traditional up-right standing position.