Abstract:When converting voxel phantoms to a surface format, the small intestine (SI), which is usually not accurately represented in a voxel phantom due to its complex and irregular shape on one hand and the limited voxel resolutions on the other, cannot be directly converted to a high-quality surface model. Currently, stylized pipe models are used instead, but they are strongly influenced by developer's subjectivity, resulting in unacceptable geometric and dosimetric inconsistencies. In this paper, we propose a new m… Show more
“…small intestine, lymphatic nodes, eye, and blood in large vessels), which are very complex and/or small in structure, could not be produced by the conversion process; therefore, they were modelled. The small intestine of each phantom was generated using a dedicated procedure and a computer program developed by Yeom et al (2016a), in which a total of 1000 different models of the small intestine are generated randomly with a Monte Carlo approach, and then the best model is selected considering both geometric and dosimetric similarity with the Publication 110 phantoms (ICRP, 2009). The lymphatic nodes were generated using a similar approach, which was used to generate the lymphatic nodes in the University of Florida and the National Cancer Institute (UF/NCI) adult phantoms (Lee et al, 2013), based on the lymphatic node data in Publication 133 (ICRP, 2016).…”
Committee 2 of the International Commission on Radiological Protection (ICRP) has constructed mesh-type adult reference computational phantoms by converting the voxel-type ICRP Publication 110 adult reference computational phantoms to a high-quality mesh format, and adding those tissues that were below the image resolution of the voxel phantoms and therefore not included in the Publication 110 phantoms. The new mesh phantoms include all the necessary source and target tissues for effective dose calculations, including the 8-40-µm-thick target layers of the alimentary and respiratory tract organs, thereby obviating the need for supplemental organ-specific stylised models (e.g. respiratory airways, alimentary tract organ walls and stem cell layers, lens of the eye, and skin basal layer). To see the impact of the new mesh-type reference phantoms, dose coefficients for some selected external and internal exposures were calculated and compared with the current reference values in ICRP Publications 116 and 133, which were calculated by employing the Publication 110 phantoms and the supplemental stylised models. The new mesh phantoms were also used to calculate dose coefficients for industrial radiography sources near the body, which can be used to estimate the organ doses of the worker who is accidentally exposed by an industrial radiography source; in these calculations, the mesh phantoms were deformed to reflect the size of the worker, and also to evaluate the effect of posture on dose coefficients.
“…small intestine, lymphatic nodes, eye, and blood in large vessels), which are very complex and/or small in structure, could not be produced by the conversion process; therefore, they were modelled. The small intestine of each phantom was generated using a dedicated procedure and a computer program developed by Yeom et al (2016a), in which a total of 1000 different models of the small intestine are generated randomly with a Monte Carlo approach, and then the best model is selected considering both geometric and dosimetric similarity with the Publication 110 phantoms (ICRP, 2009). The lymphatic nodes were generated using a similar approach, which was used to generate the lymphatic nodes in the University of Florida and the National Cancer Institute (UF/NCI) adult phantoms (Lee et al, 2013), based on the lymphatic node data in Publication 133 (ICRP, 2016).…”
Committee 2 of the International Commission on Radiological Protection (ICRP) has constructed mesh-type adult reference computational phantoms by converting the voxel-type ICRP Publication 110 adult reference computational phantoms to a high-quality mesh format, and adding those tissues that were below the image resolution of the voxel phantoms and therefore not included in the Publication 110 phantoms. The new mesh phantoms include all the necessary source and target tissues for effective dose calculations, including the 8-40-µm-thick target layers of the alimentary and respiratory tract organs, thereby obviating the need for supplemental organ-specific stylised models (e.g. respiratory airways, alimentary tract organ walls and stem cell layers, lens of the eye, and skin basal layer). To see the impact of the new mesh-type reference phantoms, dose coefficients for some selected external and internal exposures were calculated and compared with the current reference values in ICRP Publications 116 and 133, which were calculated by employing the Publication 110 phantoms and the supplemental stylised models. The new mesh phantoms were also used to calculate dose coefficients for industrial radiography sources near the body, which can be used to estimate the organ doses of the worker who is accidentally exposed by an industrial radiography source; in these calculations, the mesh phantoms were deformed to reflect the size of the worker, and also to evaluate the effect of posture on dose coefficients.
“…(44) The small intestine was not represented precisely in the Publication 110 (ICRP, 2009) phantoms, mainly because its complex tubular structure was not clearly distinguishable in the original cross-sectional CT data and its modelling was limited due to the finite voxel resolution. Accordingly, a dedicated procedure and a computer program were used to generate the small intestine models in the MRCPs (Yeom et al., 2016a). First, a surface frame, entirely enclosing the original small intestine voxel model, was constructed using the alpha-shape algorithm (Edelsbrunner et al., 1983).…”
Section: Conversion Of the Adult Voxel-type Reference Phantoms To mentioning
confidence: 99%
“…The aforementioned procedure was repeated to produce 1000 different small intestine models, with the best model selected considering both its geometric and dosimetric similarity. More detailed information on construction of the small intestine model can be found in Yeom et al. (2016a). Fig.…”
Section: Conversion Of the Adult Voxel-type Reference Phantoms To mentioning
Following the issuance of new radiological protection recommendations in ICRP Publication 103, the Commission released, in ICRP Publication 110, the adult male and female voxel-type reference computational phantoms to be used for calculation of the reference dose coefficients (DCs) 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 publication 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 micrometre-thick target regions in the respiratory and alimentary tract organs, skin, and urinary bladder, assimilating the supplementary stylised models. The MRCPs can be implemented directly into Monte Carlo particle transport codes for dose calculations (i.e. without voxelisation), fully maintaining the advantages of the mesh geometry. DCs of organ dose and effective dose and specific absorbed fractions (SAFs) calculated with the MRCPs for some external and internal exposures show that À while some differences were observed for small tissue structures and for weakly-penetrating radiations À the MRCPs provide the same or very similar values as the previously published reference DCs and SAFs, which were calculated with the Publication 110 reference phantoms and supplementary stylised models, for most tissues and penetrating radiations. Consequently, the DCs for effective dose (i.e. the fundamental protection quantity) were not found to be different. The DCs of ICRP Publication 116 and the SAFs of ICRP Publication 133 thus remain valid.
“…These phantoms are the exact counterparts of the ICRP phantoms and have the advantage that they can model small tissues below the voxel phantom resolution. More information on these phantoms can be found in a forthcoming ICRP publication (ICRP, 2020b) and in Kim et al (2011Kim et al ( , 2016Kim et al ( , 2017, Yeom et al (2013Yeom et al ( , 2016a, and Nguyen et al (2015).…”
This publication presents radionuclide-specific organ and effective doserate coefficients for members of the public resulting from environmental external exposures to radionuclide emissions of both photons and electrons, calculated using computational phantoms representing the International Commission on Radiological Protection's (ICRP) reference newborn, 1-year-old, 5-year-old, 10year-old, 15-year-old, and adult males and females. Environmental radiation fields of monoenergetic photon and electron sources were first computed using the Monte Carlo radiation transport code PHITS for source geometries representing environmental radionuclide exposures including planar sources on and within the ground at different depths (representing radionuclide ground contamination from fallout or naturally occurring terrestrial sources), volumetric sources in air (representing a radioactive cloud), and uniformly distributed sources in simulated contaminated water. For the above geometries, the exposed reference individual is considered to be completely within the radiation field. Organ equivalent dose-rate coefficients for monoenergetic photons and electrons were next computed employing the PHITS code, thus simulating photon and electron interactions within the tissues and organs of the exposed reference individual. For quality assurance purposes, further cross-check calculations were performed using GEANT4, EGSnrc, MCNPX, MCNP6, and the Visible Monte Carlo radiation transport codes. From the monoenergetic values, nuclide-specific effective and organ equivalent dose-rate coefficients were computed for 1252 radionuclides of 97 elements for the above environmental exposures using the nuclear decay data from ICRP Publication 107. The coefficients are given as dose-rates normalised to radionuclide concentrations in environmental media, such as radioactivity concentration (nSv h À1 Bq À1 m 2 or nSv h À1 Bq À1 m 3), and can be renormalised to ambient dose equivalent (Sv Sv À1) or air kerma free in air (Sv Gy À1). The main text provides effective dose-rate coefficients for selected radionuclides; details including age-and sex-dependent organ dose-rate coefficients are provided as an electronic supplement to be downloaded from the ICRP and SAGE websites. The data show that, in general, the smaller the body mass of the 136 Cs, 137 Cs/ 137m Ba) deposited on and in the ground, the difference in effective dose between an adult and an infant is in the range of 30-60%, depending on the radioactivity deposition depth within the soil.
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