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New thyroid models for ICRP pediatric mesh-type reference computational phantoms
염연수,최찬수,신방호,김수현,한혜진,문성호,손가희,김현일,Nguyen Thang Tat,정범선,이세형,김찬형 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12
As part of the ICRP Task Group 103 project, we developed ten thyroid models for the pediatric mesh-type reference computational phantoms (MRCPs). The thyroid is not only a radiosensitive target organ needed for effective dose calculation but an important source region particularly for radioactive iodines. The thyroid models for the pediatric MRCPs were constructed by converting those of the pediatric voxel-type reference computational phantoms (VRCPs) in ICRP Publication 143 to a high-quality mesh format, faithfully maintaining their original topology. At the same time, we improved several anatomical parameters of the thyroid models for the pediatric MRCPs, including the mass, overlying tissue thickness, location, and isthmus dimensions. Absorbed doses to the thyroid for the pediatric MRCPs for photon external exposures were calculated and compared with those of the pediatric VRCPs, finding that the differences between the MRCPs and VRCPs were not significant except for very low energies (<0.03 MeV). Specific absorbed fractions (target ) thyroid) for photon internal exposures were also compared, where significant differences were frequently observed especially for the target organs/tissues close to the thyroid (e.g., a factor of ~1.2e~327 for the thymus as a target) due mainly to anatomical improvement of the MRCP thyroid models.
Iodine-131 S Values for Use in Organ Dose Estimation of Korean Patients in Radioiodine Therapy
염연수,신방호,최찬수,한혜진,김찬형 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.2
In the present study, iodine-131 S values (rT ) thyroid) were calculated for 30 target organs and tissuesusing the most recently developed Korean reference computational phantoms. The calculated S valueswere then compared with those of the International Commission on Radiological Protection (ICRP)reference computational phantoms to investigate the dosimetric impact of the Korean S values againstthose of the ICRP reference phantoms. The results showed significant differences in the S values due tothe different anatomical/morphological characteristics between the Korean and ICRP reference phantoms. Most target organs/tissues showed that the S values of the Korean reference phantoms are lowerthan those of the ICRP reference phantoms, by up to about 4 times (male spleen and female thymus). Exceptionally, three target organs/tissues (gonads, thyroid, and extrathoracic region) showed that the Svalues of the Korean reference phantoms are greater, by 1.5e3.7 times. We expect that the S valuescalculated in the present study will be beneficially used to estimate organ/tissue doses of Korean patientsunder radioiodine therapy
Calculation of Local Skin Doses with ICRP Adult Mesh-type Reference Computational Phantoms
염연수,한혜진,최찬수,Thang Tat Nguyen,이한진,신방호,김찬형,한민철 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.1
Recently, Task Group 103 of the International Commission on Radiological Protection (ICRP) developed new mesh-type reference computational phantoms (MRCPs) for adult males and females in order to address the limitations of the current voxel-type reference phantoms described in ICRP Publication 110 due to their limited voxel resolutions and the nature of the voxel geometry. One of the substantial advantages of the MRCPs over the ICRP-110 reference phantoms is the inclusion of a 50-μm-thick radiosensitive skin basal-cell layer; however, a methodology for calculating the local skin dose (LSD), i.e., the maximum dose to the basal layer averaged over a 1-cm2 area, has yet to be developed. In the present study, a dedicated program for the LSD calculation with the MRCPs was developed based on the mean shift algorithm and the Geant4 Monte Carlo code. The developed program was used to calculate local skin dose coefficients (LSDCs) for electrons and alpha particles, which were then compared with the values given in ICRP Publication 116 that were produced with a simple tissue-equivalent cube model. The results of the present study show that the LSDCs of the MRCPs are generally in good agreement with the ICRP-116 values for alpha particles, but for electrons, significant differences are found at energies higher than 0.15 MeV. The LSDCs of the MRCPs are greater than the ICRP-116 values by as much as ~ 2.7 times at 10 MeV, which is due mainly to the different curvature between realistic MRCPs (i.e., curved) and the simple cube model (i.e., flat).