1
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El Bakkali J, Doudouh A. Comparison between InterDosi and MCNP in the estimation of photon SAFs on a series of ICRP pediatric voxelized phantoms. Jpn J Radiol 2023; 41:1420-1430. [PMID: 37454023 DOI: 10.1007/s11604-023-01469-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/07/2023] [Indexed: 07/18/2023]
Abstract
In the present work, a new Monte Carlo Geant4 based code called InterDosi 1.0, was used to simulate specific absorbed fractions (SAFs) in the six reference pediatric voxel-based phantoms developed by the International Commission on Radiological Protection (ICRP). The aim of this study was to assess the ability of this code to estimate SAFs in a variety of voxel-based phantoms. A large number of photon SAFs were calculated for pairs of organs corresponding to three sources and 170 target organs/regions. A total of 108 initial photons were uniformly emitted from the source organs with eight discrete energies. In order to speed up the calculation of SAFs, Monte Carlo multithreaded simulations were started on a workstation with 12 threads, and a Geant4 tracking optimization technique was applied that consists in skipping the voxel boundaries when two adjacent voxels share the same material, which seems to reduce the simulation time by an average of approximately 36%. The results showed good agreement with the reference data produced through the MCNP 2.7 code, with average and maximum absolute discrepancies of 0.5% and 7.68%, respectively. We concluded that these results confirm the feasibility of InterDosi code to perform photon internal dosimetry calculations at a voxel level.
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Affiliation(s)
- Jaafar El Bakkali
- Nuclear Medicine Department, Military Hospital Mohammed V, Rabat, Morocco.
- Royal School of Military Health Service, Rabat, Morocco.
| | - Abderrahim Doudouh
- Nuclear Medicine Department, Military Hospital Mohammed V, Rabat, Morocco
- BioPhysics Laboratory, Faculty of Medicine and Pharmacy, UM5, Rabat, Morocco
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2
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Singh PK, Patni HK, Roy R, Akar DK, Sawant PD. 131I dose coefficients for a reference population using age-specific models. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2023; 43:041508. [PMID: 37857280 DOI: 10.1088/1361-6498/ad04ef] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 10/19/2023] [Indexed: 10/21/2023]
Abstract
Age-specific dose coefficients are required to assess internal exposure to the general public. This study utilizes reference age-specific biokinetic models of iodine to estimate the total number of nuclear disintegrations ã(rS,τ) occurring in source regions (rS) during the commitment time (τ). Age-specific S values are estimated for 35 target regions due to131I present in 22rSusing data from 10 paediatric reference computational phantoms (representing five ages for both sexes) published recently by the International Commission of Radiation Protection (ICRP). Monte Carlo transport simulations are performed in FLUKA code. The estimated ã(rS,τ) and S values are then used to compute the committed tissue equivalent dose HT(τ) for 27 radiosensitive tissues and dose coefficients e(τ) for all five ages due to inhalation and ingestion of131I. The derived ã(rS,τ) values in the thyroid source are observed to increase with age due to the increased retention of iodine in the thyroid. S values are found to decrease with age, mainly due to an increase in target masses. Generally, HT(τ) values are observed to decrease with age, indicating the predominant behaviour of S values over ã(rS,τ). On average, ingestion dose coefficients are 63% higher than for inhalation in all ages. The maximum contribution to dose coefficients is from the thyroid, accounting for 96% in the case of newborns and 98%-99% for all other ages. Furthermore, the estimated e(τ) values for the reference population are observed to be lower than previously published reference values from the ICRP. The estimated S, HT(τ) and e(τ) values can be used to improve estimations of internal doses to organs/whole body for members of the public in cases of131I exposure. The estimated dose coefficients can also be interpolated for other ages to accurately evaluate the doses received by the general public during131I therapy or during a radiological emergency.
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Affiliation(s)
- Pradeep Kumar Singh
- Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Hemant Kumar Patni
- Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Rahul Roy
- Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Deepak Kumar Akar
- Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Pramilla D Sawant
- Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
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3
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Domal SJ, Correa-Alfonso CM, Paulbeck CJ, Griffin KT, Sato T, Funamoto S, Cullings HM, Egbert SD, Endo A, Hertel NE, Lee C, Bolch WE. Fetal and Maternal Atomic Bomb Survivor Dosimetry Using the J45 Pregnant Female Phantom Series: Considerations of the Kneeling and Lying Posture with Comparisons to the DS02 System. HEALTH PHYSICS 2023; 125:245-259. [PMID: 37358430 DOI: 10.1097/hp.0000000000001710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
ABSTRACT Organ dosimetry data of the atomic bomb survivors and the resulting cancer risk models derived from these data are currently assessed within the DS02 dosimetry system developed through the Joint US-Japan Dosimetry Working Group. In DS02, the anatomical survivor models are limited to three hermaphroditic stylized phantoms-an adult (55 kg), a child (19.8 kg), and an infant (9.7 kg)-that were originally designed for the preceding DS86 dosimetry system. As such, organ doses needed for assessment of in-utero cancer risks to the fetus have continued to rely upon the use of the uterine wall in the adult non-pregnant stylized phantom as the dose surrogate for all fetal organs regardless of gestational age. To address these limitations, the Radiation Effects Research Foundation (RERF) Working Group on Organ Dose (WGOD) has established the J45 (Japan 1945) series of high-resolution voxel phantoms, which were derived from the UF/NCI series of hybrid phantoms and scaled to match mid-1940s Japanese body morphometries. The series includes male and female phantoms-newborn to adult-and four pregnant female phantoms at gestational ages of 8, 15, 25, and 38 wk post-conception. In previous studies, we have reported organ dose differences between those reported by the DS02 system and those computed by the WGOD using 3D Monte Carlo radiation transport simulations of atomic bomb gamma-ray and neutron fields for the J45 phantoms series in their traditional "standing" posture, with some variations in their facing direction relative to the bomb hypocenter. In this present study, we present the J45 pregnant female phantoms in both a "kneeling" and "lying" posture and assess the dosimetric impact of these more anatomically realistic survivor models in comparison to current organ doses given by the DS02 system. For the kneeling phantoms facing the bomb hypocenter, organ doses from bomb source photon spectra were shown to be overestimated by the DS02 system by up to a factor of 1.45 for certain fetal organs and up to a factor of 1.17 for maternal organs. For lying phantoms with their feet in the direction of the hypocenter, fetal organ doses from bomb source photon spectra were underestimated by the DS02 system by factors as low as 0.77, while maternal organ doses were overestimated by up to a factor of 1.38. Organs doses from neutron contributions to the radiation fields exhibited an increasing overestimation by the DS02 stylized phantoms as gestational age increased. These discrepancies are most evident in fetal organs that are more posterior within the mother's womb, such as the fetal brain. Further analysis revealed that comparison of these postures to the original standing posture indicate significant dose differences for both maternal and fetal organ doses depending on the type of irradiation. Results from this study highlight the degree to which the existing DS02 system can differ from organ dosimetry based upon 3D radiation transport simulations using more anatomically realistic models of those survivors exposed during pregnancy.
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Affiliation(s)
- Sean J Domal
- Medical Physics Program, College of Medicine, University of Florida, Gainesville, FL
| | | | - Colin J Paulbeck
- Department of Radiology, Johns Hopkins University, Baltimore, MD
| | | | - Tatsuhiko Sato
- Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokaimura, Japan
| | - Sachiyo Funamoto
- Department of Statistics, Radiation Effects Research Foundation, Hiroshima, Japan
| | - Harry M Cullings
- Department of Statistics, Radiation Effects Research Foundation, Hiroshima, Japan
| | | | - Akira Endo
- Nuclear Science Research Institute, Japan Atomic Energy Agency, Tokaimura, Japan
| | - Nolan E Hertel
- George W. Woodruff School of Mechanical Eng., Georgia Institute of Technology, Atlanta, GA
| | - Choonsik Lee
- National Cancer Institute, National Institutes of Health, Rockville, MD
| | - Wesley E Bolch
- J. Crayton Pruitt Family Department of Biomedical Eng., University of Florida, Gainesville, FL USA
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4
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Kesner AL, Carter LM, Ramos JCO, Lafontaine D, Olguin EA, Brown JL, President B, Jokisch DW, Fisher DR, Bolch WE. MIRD Pamphlet No. 28, Part 1: MIRDcalc-A Software Tool for Medical Internal Radiation Dosimetry. J Nucl Med 2023; 64:1117-1124. [PMID: 37268428 PMCID: PMC10315701 DOI: 10.2967/jnumed.122.264225] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 03/21/2023] [Indexed: 06/04/2023] Open
Abstract
Medical internal radiation dosimetry constitutes a fundamental aspect of diagnosis, treatment, optimization, and safety in nuclear medicine. The MIRD committee of the Society of Nuclear Medicine and Medical Imaging developed a new computational tool to support organ-level and suborgan tissue dosimetry (MIRDcalc, version 1). Based on a standard Excel spreadsheet platform, MIRDcalc provides enhanced capabilities to facilitate radiopharmaceutical internal dosimetry. This new computational tool implements the well-established MIRD schema for internal dosimetry. The spreadsheet incorporates a significantly enhanced database comprising details for 333 radionuclides, 12 phantom reference models (International Commission on Radiological Protection), 81 source regions, and 48 target regions, along with the ability to interpolate between models for patient-specific dosimetry. The software also includes sphere models of various composition for tumor dosimetry. MIRDcalc offers several noteworthy features for organ-level dosimetry, including modeling of blood source regions and dynamic source regions defined by user input, integration of tumor tissues, error propagation, quality control checks, batch processing, and report-preparation capabilities. MIRDcalc implements an immediate, easy-to-use single-screen interface. The MIRDcalc software is available for free download (www.mirdsoft.org) and has been approved by the Society of Nuclear Medicine and Molecular Imaging.
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Affiliation(s)
- Adam L Kesner
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York;
| | - Lukas M Carter
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Juan C Ocampo Ramos
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Daniel Lafontaine
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Edmond A Olguin
- Beth Israel Deaconess Medical Center, Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Justin L Brown
- J. Crayton Pruitt Department of Biomedical Engineering, University of Florida, Gainesville, Florida
| | - Bonnie President
- J. Crayton Pruitt Department of Biomedical Engineering, University of Florida, Gainesville, Florida
| | - Derek W Jokisch
- Department of Physics and Engineering, Francis Marion University, Florence, South Carolina
- Center for Radiation Protection Knowledge, Oak Ridge National Laboratory, Oak Ridge, Tennessee; and
| | - Darrell R Fisher
- University of Washington and Versant Medical Physics and Radiation Safety, Richland, Washington
| | - Wesley E Bolch
- J. Crayton Pruitt Department of Biomedical Engineering, University of Florida, Gainesville, Florida
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5
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Coleman D, Griffin KT, Dewji SA. Stylized versus voxel phantoms: quantification of internal organ chord length distances. Phys Med Biol 2023; 68. [PMID: 36780697 DOI: 10.1088/1361-6560/acbbb6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 02/13/2023] [Indexed: 02/15/2023]
Abstract
Dosimetric calculations, whether for radiation protection or nuclear medicine applications, are greatly influenced by the use of computational models of humans, called anthropomorphic phantoms. As anatomical models of phantoms have evolved and expanded, thus has the need for quantifying differences among each of these representations that yield variations in organ dose coefficients, whether from external radiation sources or internal emitters. This work represents an extension of previous efforts to quantify the differences in organ positioning within the body between a stylized and voxel phantom series. Where prior work focused on the organ depth distribution vis-à-vis the surface of the phantom models, the work described here quantifies the intra-organ and inter-organ distributions through calculation of the mean chord lengths. The revised Oak Ridge National Laboratory stylized phantom series and the University of Florida/National Cancer Institute voxel phantom series including a newborn, 1-, 5-, 10- and 15 year old, and adult phantoms were compared. Organ distances in the stylized phantoms were computed using a ray-tracing technique available through Monte Carlo radiation transport simulations in MCNP6. Organ distances in the voxel phantom were found using phantom matrix manipulation. Quantification of differences in organ chord lengths between the phantom series displayed that the organs of the stylized phantom series are typically situated farther away from one another than within the voxel phantom series. The impact of this work was to characterize the intra-organ and inter-organ distributions to explain the variations in updated internal dose coefficient quantities (i.e. specific absorbed fractions) while providing relevant data defining the spatial and volumetric organ distributions in the phantoms for use in subsequent internal dosimetric computations, with prospective relevance to patient-specific individualized dosimetry, as well as informing machine learning definition of organs using these reference models.
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Affiliation(s)
- D Coleman
- University of Wisconsin-Madison, Department of Medical Physics 1111 Highland Ave Rm 1005, Madison, WI 53705-2275, United States of America
| | - K T Griffin
- National Cancer Institute, Radiation Epidemiology Branch, 9609 Medical Center Drive MSC 9776, Bethesda, MD 20892-2590, United States of America.,Georgia Institute of Technology, Nuclear and Radiological Engineering and Medical Physics Programs, 770 State Street, Atlanta, GA 30332-0405, United States of America
| | - S A Dewji
- Georgia Institute of Technology, Nuclear and Radiological Engineering and Medical Physics Programs, 770 State Street, Atlanta, GA 30332-0405, United States of America
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Ghalbzouri TE, Bardouni TE, Bakkali JE, Satti H, Arectout A, Berriban I, Nouayti A, Yerrou R. Photon-specific absorbed fraction estimates in stylized ORNL and voxelized ICRP adult male phantoms using a new developed Geant4-based code "DoseCalcs": a validation study. Radiol Phys Technol 2022; 15:323-339. [PMID: 36065049 DOI: 10.1007/s12194-022-00672-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 08/12/2022] [Accepted: 08/13/2022] [Indexed: 10/14/2022]
Abstract
When a radiotracer is injected into a patient's body as part of a nuclear medicine investigation, the entire body is exposed to the ionizing radiation emitted, which can cause biological damage. Therefore, it is important to predict the internal radiation dose to properly balance the advantages of radiological examinations. Currently, various Monte Carlo tools, such as MCNP, Geant4, and GATE, are available to estimate internal radiation dosimetry-related quantities, such as S values (S) and specific absorbed fractions (SAF). Such codes make physics easier for physicists who are experienced with computer programming; however, programming and/or simulation inputs remain a time-consuming and intensive task. In this study, we present a newly developed Geant4-based code for internal dosimetry calculations, namely "DoseCalcs". To assess the performance of the geometrical methods and computational capabilities of our developed tool, we used the GDML, TEXT, STL, and C++ methods to model the ORNL adult phantom, and a voxel-based structure to construct the ICRP adult male. SAFs in the ORNL and ICRP adult male phantoms for eight discrete mono-energetic photons with energies ranging from 0.01 to 2 MeV are calculated with DoseCalcs and compared to ORNL and OpenDose reference data. The two phantoms showed good agreement with both references, which indicates the accuracy of DoseCalcs for subsequent use in estimating internal dosimetry quantities using a variety of geometrical methods.
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Affiliation(s)
- Tarik El Ghalbzouri
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco.
| | - Tarek El Bardouni
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco
| | - Jaafar El Bakkali
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco.,Nuclear Medicine Department, Military Hospital Mohammed V, Rabat, Morocco
| | - Hicham Satti
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco
| | - Assia Arectout
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco
| | - Iman Berriban
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco
| | - A Nouayti
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco
| | - Randa Yerrou
- ERSN Laboratory, Physics Department, Faculty of Sciences, University Abdelmalek Essaadi, Tetouan, Morocco
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7
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Isaksson M, Tondel M, Wålinder R, Rääf C. Absorbed dose rate coefficients for 134Cs and 137Cs with steady-state distribution in the human body: S-coefficients revisited. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2021; 41:1213-1227. [PMID: 34634780 DOI: 10.1088/1361-6498/ac2ec4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
In the event of an accidental release of radioactive elements from a nuclear power plant, it has been shown that the radionuclides contributing the most to long-term exposure are134Cs and137Cs. In the case of nuclear power plant fallout, with subsequent intake of radionuclides through the food chain, the internal absorbed dose to target tissues from protracted intake of radionuclides needs to be estimated. Internal contamination from food consumption is not caused by a single intake event; hence, the committed equivalent dose, calculated by a dose coefficient or dose per content function, cannot be easily used to calculate the cumulative absorbed dose to relevant target tissues in the body. In this study, we calculated updated absorbed dose rate coefficients for134Cs and137Cs based on data from the International Commission on Radiological Protection (ICRP) on specific absorbed fractions. The absorbed dose rate coefficients are provided for male and female adult reference phantoms, respectively, assuming a steady-state distribution of Cs that we calculated from the ICRP biokinetic model for Cs. With these coefficients, the absorbed dose to the listed target tissues, separately and to the total body, are related to the number of nuclear transitions (time-integrated activity) in each listed source region. Our new absorbed dose rate coefficients are given for the complete set of target tissues and have not been presented before. They are also provided for aggregated categories of organs to facilitate epidemiological studies.
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Affiliation(s)
- Mats Isaksson
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Martin Tondel
- Occupational and Environmental Medicine, Department of Medical Sciences, University of Uppsala, Uppsala, Sweden
- Occupational and Environmental Medicine, Uppsala University Hospital, Uppsala, Sweden
| | - Robert Wålinder
- Occupational and Environmental Medicine, Department of Medical Sciences, University of Uppsala, Uppsala, Sweden
- Occupational and Environmental Medicine, Uppsala University Hospital, Uppsala, Sweden
| | - Christopher Rääf
- Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden
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8
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Schwarz BC, Godwin WJ, Wayson MB, Dewji SA, Jokisch DW, Lee C, Bolch WE. Specific absorbed fractions for a revised series of the UF/NCI pediatric reference phantoms: internal electron sources. Phys Med Biol 2021; 66:035005. [PMID: 33142278 DOI: 10.1088/1361-6560/abc709] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In both the International Commission on Radiological Protection (ICRP) and Medical Internal Radiation Dose (MIRD) schemata of internal dosimetry, the S-value is defined as the absorbed dose to a target organ per nuclear decay of the radionuclide in a source organ. Its computation requires data on the energies and yields of all radiation emissions from radionuclide decay, the mass of the target organ, and the value of the absorbed fraction-the fraction of particle energy emitted in the source organ that is deposited in the target organ. The specific absorbed fraction (SAF) is given as the ratio of the absorbed fraction and the target mass. Historically, in the early development of both schemata, computational simplifications were made to the absorbed fraction in considering both organ self-dose ([Formula: see text]) and organ cross-dose ([Formula: see text]). In particular, the value of the absorbed fraction was set to unity for all 'non-penetrating' particle emissions (electrons and alpha particles) such that they contributed only to organ self-dose. As radiation transport codes for charged particles became more widely available, it became increasingly possible to abandon this distinction and to explicitly consider the transport of internally emitted electrons in a manner analogous to that for photons. In this present study, we report on an extensive series of electron SAFs computed in a revised series of the UF/NCI pediatric phantoms. A total of 28 electron energies-0-10 MeV-along a logarithmic energy grid are provided in electronic annexes, where 0 keV is associated with limiting values of the SAF. Electron SAFs were computed independently for collisional energy losses (SAFCEL) and radiation energy losses (SAFREL) to the target organ. A methodology was employed in which values of SAFREL were compiled by first assembling organ-specific and electron energy-specific bremsstrahlung x-ray spectra, and then using these x-ray spectra to re-weight a previously established monoenergetic database of photon SAFs for all phantoms and source-target combinations. Age-dependent trends in the electron SAF were demonstrated for the majority of the source-target organ pairs, and were consistent to values given for the ICRP adult phantoms. In selected cases, however, anticipated age-dependent trends were not seen, and were attributed to anatomical differences in relative organ positioning at specific phantom ages. Both the electron SAFs of this study, and the photon SAFs from our companion study, are presently being used by ICRP Committee 2 in its upcoming pediatric extension to ICRP Publication 133.
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Affiliation(s)
- Bryan C Schwarz
- Department of Radiology, University of Florida, Gainesville, FL 32611, United States of America
| | - William J Godwin
- Department of Radiation Oncology, Medical University of South Carolina, Charleston, SC 29407, United States of America
| | - Michael B Wayson
- Baylor Scott & White Health, Dallas, TX 76051, United States of America
| | - Shaheen A Dewji
- Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843, United States of America
| | - Derek W Jokisch
- Department of Physics and Engineering, Francis Marion University, Florence, SC 29502, United States of America.,Center for Radiation Protection Knowledge, Oak Ridge National Laboratory, Oak Ridge, TN 37830, United States of America
| | - Choonsik Lee
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20850, United States of America
| | - Wesley E Bolch
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, United States of America
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