Method for spot urine normalization by 40K in a radiation emergency.

In this study, to assess the internal radiation dose in radiation emergencies, the variability of spot urine normalization methods is studied using 40K measurement results. The mean creatinine concentration and the mean 40K activity concentration in the spot urine samples studied were 139 mg dL-1 and 106 Bq kg-1, respectively. The results indicate that the 40K activity concentration method can be used to complement the method used for normalizing the creatinine concentration in spot urine in a radiological emergency.

Validation of the whole-body counting measurement in a radiation emergency.

Whole-body measurement can provide fast and accurate results in radiation emergencies. The whole-body counting method needs to be validated to guarantee the reliability and accuracy of the measurement. This study provides data related to the validation of the whole-body measurement using the stand-up type whole-body counter. Several parameters, including the sensitivity, accuracy, uncertainty, were considered for validation. The results indicate that the method of whole-body measurement is reliable for assessment of internal contamination.

Uncertainty quantification of bioassay functions for the internal dosimetry of radioiodine.

Bioassay functions, which are provided by the International Commission on Radiological Protection, are used to estimate the intake activity of radionuclides; however, they include considerable uncertainties in terms of the internal dosimetry for a particular individual. During a practical internal dose assessment, the uncertainty in the bioassay function is generally not introduced because of the difficulty in quantification. Therefore, to clarify the existence of uncertainty in the bioassay function and provide dosimetrists with an insight into this uncertainty, this study attempted to quantify the uncertainty in the thyroid retention function used for radioiodine exposure. The uncertainty was quantified using a probabilistic estimation of the thyroid retention function through the propagation of the distribution of biokinetic parameters by the Monte Carlo simulation technique. The uncertainties in the thyroid retention function, expressed in terms of the scattering factor, were in the ranges of 1.55-1.60 and 1.40-1.50 for within 24 h and after 24 h, respectively. In addition, the thyroid retention function within 24 h was compared with actual measurement data to confirm the uncertainty due to the use of first-order kinetics in the biokinetic model calculation. Significantly higher thyroid uptakes (by a factor of 1.9) were observed in the actual measurements. This study indicates that consideration of the uncertainty in the thyroid retention function can avoid a significant over- and under-estimation of the internal dose, particularly when a high dose is predicted.

Evaluation of performance characteristics of portal monitor for radiation emergency.

For evaluating the counting efficiency of a portal monitor, we use a137Cs radiation point source (1 µCi) to subsequently establish it effective measurable area. Through simulation, we estimate the appropriate distance from potentially contaminated individuals in the scanning queue to the monitoring individual. When this distance is over 10 m, the counting efficiency was below 0.01%. We find that the triage can be applied to roughly 180 individuals per hour during mass casualties.

Non-coplanar VMAT plans for lung SABR to reduce dose to the heart: a planning study.

OBJECTIVE: This study aimed to compare the plan quality of non-coplanar partial arc (NPA) volumetric modulated arc therapy (VMAT) to that of coplanar partial arc (CPA) VMAT for stereotactic ablative radiotherapy (SABR) for lung cancer. METHODS: A total of 20 patients treated for lung cancer with the SABR VMAT technique and whose lung tumors were close to the heart were retrospectively selected for this study. For the CPA VMAT, three coplanar half arcs were used while two coplanar half arcs and one noncoplanar arc rotating 315°-45° with couch rotations of 315° ± 5° were used for the NPA VMAT. For each patient, identical CT image sets and identical structures were used for both the CPA and NPA VMAT plans. Dose-volumetric parameters of each plan were analyzed. RESULTS: For the planning target volume and both lungs, no statistically significant differences between the CPA and NPA VMAT plans were observed in general. For the heart, average values of D0.1cc of the CPA and NPA VMAT plans were 29.42 ± 13.37 and 21.71 ± 9.20 Gy, respectively (p < 0.001). For whole body, the mean dose and the gradient index of the CPA VMAT plans were 1.2 ± 0.5 Gy and 4.356 ± 0.608 while those of the NPA VMAT plans were 1.1 ± 0.5 Gy and 4.111 ± 0.480, respectively (both with p < 0.001). CONCLUSION: The NPA VMAT proposed in this study showed more favorable plan quality than the CPA VMAT plans for lung SABR with tumors located close to the heart. ADVANCES IN KNOWLEDGE: For lung SABR, NPA VMAT can reduce doses to the heart as well as whole-body irradiation.

ANALYSIS OF THE RADIOLOGICAL SAFETY CONTROL LEVEL VERSUS THE EXPOSURE OF RADIATION WORKERS IN SOUTH KOREA FROM 2008-17.

In this study, the radiation exposure of workers at workplaces registered and licensed between 2008 and 2017 for the production/sale/use of radioactive isotopes (RI) and radioactive generators (RG) was analysed to evaluate the quality of radiation safety management controls in use. The number of facilities using RIs increased by ~26% from 2008 to 2017 whereas the number of facilities using RGs increased by ~166% over the same period. There were 33 029 radiation workers in all fields in 2008, and the number increased by ~32% to 43 467 by 2017. However, the collective effective dose of radiation received by workers decreased in all industries except for those working in nuclear power plants. In other words, the quality of radiation safety management improved over that same time period due to the systematic, continuous introduction of safety mechanisms by the regulatory authority.

An investigation into internal exposure management needs for nuclear medicine practitioners and temporary visitors through I-131 internal dose assessment: Focusing on large hospitals in South Korea.

PURPOSE: To investigate the internal exposure of nuclear medicine practitioners in South Korea. METHODS: This study selected nuclear medicine practitioners among domestic hospitals and quantitatively measured their degree of internal exposure to radioisotopes, and conducted a dose assessment based on the results. For the dose assessment, 35 nuclear medicine practitioners at seven large hospitals were selected as the measurement subjects, and the measurements were obtained using the thyroid count, total body count, and a urine sample analysis. The internal exposure was measured once every two weeks, and measurements were obtained three to 15 times according to the practitioners. RESULTS: As a result of measuring and analyzing the radionuclides with urine samples, one or more detections above the minimum detectable activity (MDA) was identified in 52 (15%) among all 340 cases for 14 of the practitioners (43%). The committed effective doses were evaluated as have a distribution of zero to 5.4 mSv, and were mostly 1 mSv or less. There were four practitioners exceeding 1 mSv based on the whole-body measurements, whose results from a urine sample analysis and thyroid monitoring all showed exposure of 1 mSv or less. All of the practitioners participated directly in the distribution and handling of radioactive sources, and none of the nurses exceeded 1 mSv. Furthermore, it was noteworthy that, among medical assistants who do not directly handle radioisotopes and are mainly involved in the transport of contaminated patients, there was one person who exceeded the whole-body measurement standard of 1 mSv. CONCLUSIONS: The committed effective dose of most nuclear medicine practitioners who participated in the survey was lower than 1 mSv. However, because the possibility of overexposure under special circumstances cannot be completely excluded, new strict radiation protection rules on the handling of open-source radioisotopes in hospitals are required for non-handling workers.

Establishment of Criteria for Skin Decontamination in a Radiation Emergency.

In the event of a radiological or nuclear emergency, internal or external contamination (or both) by radionuclides can occur. In such cases, removal of the radionuclides from the injured skin is important because such surface contamination may induce skin damage such as deterministic effects at very high skin doses (2 to 3 Gy). In addition, internal contamination will occur due to radionuclide absorption through the injured skin. Previous studies have suggested various decontamination criteria. However, those criteria are impractical in the case of large-scale population monitoring. Here, to identify practical decontamination criteria, the VARSKIN 4.0 software code is used to assess skin doses originating from surface contamination by Co, I, and Cs. In addition, Integrated Modules for Bioassay Assessment dosimetry software is used to assess the effective doses following radionuclide intake through external contamination for the same three radionuclides. The effective dose dependence on the soluble material type is also assessed. In particular, the effective dose due to radionuclide absorption is found to be greater than the skin dose rate due to surface contamination for the same radioactivity levels. Based on the calculation results, decontamination criteria and actions that depend on the effective dose and surface contamination level (Bq cm) for alpha and beta or gamma radiation are suggested. Actions for contaminated injured persons are classified as no action, optional, recommended, or required.

Measurement and Simulation of the Counting Efficiency of a Whole-body Counter Using a BOMAB Phantom Inserted with Rod Sources Containing Mixed Radionuclides.

The examination of internal contamination is important for providing an adequate medical response during a radiological emergency. A whole-body counting system can assess gamma-emitting radionuclides in a human body when monitoring internal contamination. It is necessary to calibrate whole-body counting systems by using a calibration phantom, such as a Bottle Manikin Absorption phantom, to properly assess internal contamination. However, the total weight of the Bottle Manikin Absorber phantom is high, and there can be leakage of radioactive sources, which are disadvantages of using such a phantom. This study proposes a calibration phantom that is designed to overcome these disadvantages. The proposed phantom consists of rod sources that are inserted in each part of the phantom. The counting efficiency of the rod-source-inserted calibration phantom was acquired using a Monte Carlo simulation method, but the results were evaluated by comparing the experimental efficiencies with those of a conventional Bottle Manikin Absorption phantom by using two commercial whole-body counting systems (stand-up type and bed type). The efficiency curve of the rod-source-inserted phantom matched well that of the conventional calibration phantom. The relative deviation between the efficiencies of the conventional Bottle Manikin Absorption phantom and the proposed calibration phantom in both whole-body counting systems was less than 11%, and the total weight of the phantom was also reduced. These results suggest that the proposed phantom can be manipulated more easily and replace the conventional Bottle Manikin Absorption calibration phantom for these two types of whole-body counting systems.

ASSESSMENT OF BODY POTASSIUM LEVEL BY GENDER AND AGE IN KOREAN ADULT GROUP.

Most internal radiation dose resulting from natural radionuclides is due to radon and radioactive potassium. Total body potassium (TBK) in human body may vary by ethnic group, gender and age. The objective of this study was to measure TBK and body potassium concentration in Korean subjects. Body potassium concentrations of the subjects were measured with a whole-body counter for 283 adult males and 181 adult females. Average TBK value and body potassium level were 111.2 g and 1.5 g kg-1 for males, while for females they were 71.7 g and 1.4 g kg-1. TBK increased with increasing body weight. Body potassium level per body weight was inversely proportional to age in both genders. The annual effective doses due to 40K in the human body of Korean population were calculated to be 0.15 and 0.13 mSv for males and females, respectively.

Effective dose evaluation of NORM-added consumer products using Monte Carlo simulations and the ICRP computational human phantoms.

The aim of this study is to evaluate the potential hazard of naturally occurring radioactive material (NORM) added consumer products. Using the Monte Carlo method, the radioactive products were simulated with ICRP reference phantom and the organ doses were calculated with the usage scenario. Finally, the annual effective doses were evaluated as lower than the public dose limit of 1mSv y(-1) for 44 products. It was demonstrated that NORM-added consumer products could be quantitatively assessed for the safety regulation.

Screening of alpha- and beta-emitting radionuclides using liquid scintillation counting and monitoring procedures in radiation emergencies.

Urine gross alpha and beta activity analysis was conducted, and an internal contamination screening method was adopted to monitor visitors to Japan after the Fukushima accident. In particular, spot urine samples were used to evaluate internal contamination for 16 mo, and a total of 90 people participated in gross alpha and beta emitter screening. An ultra-low-background liquid scintillation counter was used for measurement, and optimal pulse shape analysis values were determined by measuring alpha- and beta-emitting certified reference materials. Moreover, linearity and reproducibility were assessed to validate the adopted methods, and international intercomparison was conducted using synthetic urine samples by measuring alpha- and beta-emitting radionuclides in multi-contaminated samples. Here, the measurement results of visitors to Japan are discussed, and a screening procedure is established for gross alpha and beta activity analysis during radiation emergencies.

32P measurement and dose conversion factor evaluation of activated human hair by criticality accident.

In order to conduct dose assessment of victims in criticality accidents, a method of fast neutron capture-activated (32)P measurement of hair in which samples are treated by a chemical and analytical procedure that takes 9 h and measurement is conducted by liquid scintillation counting is presented. To validate this measurement method, hair samples spiked with a (32)P reference source were measured and the results analysed and the optimal sample mass and detection efficiency were determined. To verify the correlation between (32)P-specific activity and absorbed dose for spectra with two neutron mean energies, samples collected from three normal individuals were irradiated at various neutron energies and irradiation times using the MC50 Cyclotron of the Korea Institute of Radiological and Medical Sciences. The (32)P-specific activity trend of the irradiated hair agreed well with the absorbed doses. Based on the results, dose conversion factors, which were 0.67 ± 0.15 and 0.59 ± 0.06 Gy (Bq g(-1))(-1) at neutron mean energies of 2.33 and 5.36 MeV, respectively, were calculated as a guide for medical treatment of criticality accident victims.

Radioactive contamination monitoring for the Korean public following Fukushima nuclear accident.

On March 11, 2011, as a result of the Great East Japan Earthquake, severe damage to the Fukushima nuclear power plant caused the release of radioactive materials. We conducted radioactive contamination monitoring for Korean residents in Japan and Korean travelers to East Japan after the accident. More than 800 members of the Korean public were surveyed for personal monitoring. Measured levels of external and internal contamination were within the screening levels for each monitoring method.

Evaluation of sodium activation distribution in the PMMA water phantom after fast neutron irradiation.

(24)Na produced by the neutron activation of stable sodium in the body is commonly used to assess neutron doses after criticality accidents. However, the (24)Na distribution is not uniform owing to the interaction with the human body. In this study, we experimentally evaluated the (24)Na distribution in a PMMA water phantom and 60 polyethylene vials. The vials were analyzed to evaluate the sodium activation distribution in the PMMA water phantom by employing a correction factor.