Inclusion of thin target and source regions in alimentary and respiratory tract systems of mesh-type ICRP adult reference phantoms.

It is not feasible to define very small or complex organs and tissues in the current voxel-type adult reference computational phantoms of the International Commission on Radiological Protection (ICRP), which limit dose coefficients for weakly penetrating radiations. To address the problem, the ICRP is converting the voxel-type reference phantoms into mesh-type phantoms. In the present study, as a part of the conversion project, the micrometer-thick target and source regions in the alimentary and respiratory tract systems as described in ICRP Publications 100 and 66 were included in the mesh-type ICRP reference adult male and female phantoms.

Development of skeletal system for mesh-type ICRP reference adult phantoms.

The reference adult computational phantoms of the international commission on radiological protection (ICRP) described in Publication 110 are voxel-type computational phantoms based on whole-body computed tomography (CT) images of adult male and female patients. The voxel resolutions of these phantoms are in the order of a few millimeters and smaller tissues such as the eye lens, the skin, and the walls of some organs cannot be properly defined in the phantoms, resulting in limitations in dose coefficient calculations for weakly penetrating radiations. In order to address the limitations of the ICRP-110 phantoms, an ICRP Task Group has been recently formulated and the voxel phantoms are now being converted to a high-quality mesh format.

New small-intestine modeling method for surface-based computational human phantoms.

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 method for the construction of SI models based on the Monte Carlo approach.

Incorporation of detailed eye model into polygon-mesh versions of ICRP-110 reference phantoms.

The dose coefficients for the eye lens reported in ICRP 2010 Publication 116 were calculated using both a stylized model and the ICRP-110 reference phantoms, according to the type of radiation, energy, and irradiation geometry. To maintain consistency of lens dose assessment, in the present study we incorporated the ICRP-116 detailed eye model into the converted polygon-mesh (PM) version of the ICRP-110 reference phantoms. After the incorporation, the dose coefficients for the eye lens were calculated and compared with those of the ICRP-116 data.

Internal dosimetry for intake of 18FDG using spot urine sample.

In nuclear medicine, workers handle unsealed radioactive materials. Among the materials, (18)FDG is the most widely used in PET/CT technique. Because of the short half-life of (18)F, it is very challenging to monitor internal exposure of nuclear medicine workers using in vitro bioassay.

Estimation of external radiation dose to caregivers of patients treated with radioiodine after thyroidectomy.

Due to the remarkable increase in thyroid cancer cases, the number of patients treated with radioiodine (I) shows a sharply increasing trend in recent years. Accordingly, radiation exposure of other people, particularly caregivers or comforters, after release of patients from hospitals is getting more attention than ever. In the present study, empirical equations are proposed for estimation of doses to caregivers.

Radiological protection issues arising during and after the Fukushima nuclear reactor accident.

Following the Fukushima accident, the International Commission on Radiological Protection (ICRP) convened a task group to compile lessons learned from the nuclear reactor accident at the Fukushima Daiichi nuclear power plant in Japan, with respect to the ICRP system of radiological protection. In this memorandum the members of the task group express their personal views on issues arising during and after the accident, without explicit endorsement of or approval by the ICRP. While the affected people were largely protected against radiation exposure and no one incurred a lethal dose of radiation (or a dose sufficiently large to cause radiation sickness), many radiological protection questions were raised.

Groundshine dose-rate conversion factors of soil contaminated to different depths.

For assessment of external doses from the ground contaminated with radionuclides, the dose-rate conversion factors (DCFs) prescribed in FGR (Federal Guidance Report) 12 have been used. Recently, significant changes were made by International Commission on Radiological Protection in dosimetric models and parameters, which include use of Reference Phantoms and revised tissue-weighting factors, as well as the updated decay data of radionuclides. The DCFs for effective and equivalent doses due to groundshine from contaminated soil were re-calculated by taking the changes into account.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion.

Measurements and prediction of the ambient dose rate from patient receiving radioiodine administration after thyroid ablation.

Empirical equations were proposed for the prediction of the ambient dose equivalent rates from patients administered with radioiodine for the treatment of thyroid cancers. Ambient dose equivalent rates were measured for 59 patients who received high-dose (131)I treatment after thyroid ablation at different times after the administration. An ion chamber was used to measure the dose equivalent rates at 1 m away from the body and on contact to the thyroid of the patients.

A validation of computational phantoms from photographic images for patient-tailored whole body counting.

This study attempted to validate a new method for patient-tailored efficiency calibration. Digital calibration with Monte Carlo simulations was used to substitute the lack of precision limitation due to the limited number of experimental phantoms in whole body counting calibration for internal dosimetry. The validity of this approach was examined by comparing the simulation results to the measured values from actual measurements using family BOMAB phantoms.

Use of photographic images to construct voxel phantoms for use in whole-body counting.

Quantification of radioactivity in the body by in vivo bioassay uses counting efficiencies obtained from calibration from a phantom. Usually a standardised BOMAB (Bottle Manikin Absorption) phantom is employed for whole-body counting. The physical size of workers being counted, however, may differ from the calibration phantom, and can be a source of significant errors in dose estimates.

New empirical formula for neutron dose level at the maze entrance of 15 MV medical accelerator facilities.

An easily applicable empirical formula was derived for use in the assessment of the photoneutron dose at the maze entrance of a 15 MV medical accelerator treatment room. The neutron dose equivalent rates around the Varian medical accelerator head calculated with the Monte Carlo code MCNPX were used as the source term in producing the base data. The dose equivalents were validated by measurements with bubble detectors.

Radiological risk assessment for field radiography based on two dimensional Monte Carlo analysis.

Probabilistic risk assessment studies use probability distributions for one or more variables of the risk equation in order to quantitatively characterize the variability and uncertainty. In this study, an advanced technique called the two-dimensional Monte Carlo analysis (2D MCA) is applied to estimation of radiological risk for worker and member of the public in the vicinity of the work place for field radiological system in Korea. The variables of the risk model along with the parameters of these variables are described in terms of probability density functions (PDFs).

Usefulness of the simultaneous bioassay analysis method used for an intake estimation of a radionuclide.

An intake of a radionuclide is estimated based on bioassay measurement data obtained by an in vivo or an in vitro method. Often the intake estimates from one bioassay analysis are considerably different from other results. For better estimates, a simultaneous or combined analysis of measurement data from different bioassay methods is attempted.

Applicability of dose conversion coefficients of ICRP 74 to Asian adult males: Monte Carlo simulation study.

International Commission on Radiological Protection (ICRP) reported comprehensive dose conversion coefficients for adult population, which is exposed to external photon sources in the Publication 74. However, those quantities were calculated from so-called stylized (or mathematical) phantoms composed of simplified mathematical surface equations so that the discrepancy between the phantoms and real human anatomy has been investigated by several authors using Caucasian-based voxel phantoms. To address anatomical and racial limitations of the stylized phantoms, several Asian-based voxel phantoms have been developed by Korean and Japanese investigators, independently.

On the need to revise the arm structure in stylized anthropomorphic phantoms in lateral photon irradiation geometry.

Distributions of radiation absorbed dose within human anatomy have been estimated through Monte Carlo radiation transport techniques implemented for two different classes of computational anthropomorphic phantoms: (1) mathematical equation-based stylized phantoms and (2) tomographic image-based voxel phantoms. Voxel phantoms constructed from tomographic images of real human anatomy have been actively developed since the late 1980s to overcome the anatomical approximations necessary with stylized phantoms, which themselves have been utilized since the mid 1960s. However, revisions of stylized phantoms have also been pursued in parallel to the development of voxel phantoms since voxel phantoms (1) are initially restricted to the individual-specific anatomy of the person originally imaged, (2) must be restructured on an organ-by-organ basis to conform to reference individual anatomy and (3) cannot easily represent very fine anatomical structures and tissue layers that are thinner than the voxel dimensions of the overall phantom.

Development of the two Korean adult tomographic computational phantoms for organ dosimetry.

Following the previously developed Korean tomographic phantom, KORMAN, two additional whole-body tomographic phantoms of Korean adult males were developed from magnetic resonance (MR) and computed tomography (CT) images, respectively. Two healthy male volunteers, whose body dimensions were fairly representative of the average Korean adult male, were recruited and scanned for phantom development. Contiguous whole body MR images were obtained from one subject exclusive of the arms, while whole-body CT images were acquired from the second individual.