• Journal of Radiation Protection and Research
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• 제30권3호
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• pp.113-119
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• 2005

전산화단층촬영(Computed Tomography, CT)은 높은 품질의 인체 단층 영상을 제공하지만 기존의 진단 X선 촬영에 비해 상당히 높은 선량을 환자에게 부여한다. 더욱이 CT 촬영의 수요는 계속적인 증가추세를 보이고 있어 CT 촬영 환자의 선량에 대한 관심이 높아지고 있다. 이에 본 연구에서는 물리적 실측 팬텀과 열형광 선량계를 이용하여 CT 촬영으로 인한 환자의 피폭 선량을 측정을 통해 평가해 보았다. 촬영방식을 기존의 축방향 스캔과 현재 주류를 이루고 있는 나선형 스캔으로 구분하여 선량 측정을 수행하였으며 그 결과 환자의 유효선량이 각각 17.78mSv, 10.01mSv으로 평가되었다. 또한 나선형 스캔 시 환자 선량의 감축 정도는 pitch에 의존한다는 기존의 연구결과를 재확인할 수 있었다. 본 연구에서 사용한 실측 기법은 CT 기술 발전에 기인한 촬영 프로토콜의 변화가 있는 경우 환자 선량 재평가에 응용할 수 있다.

• Journal of Radiation Protection and Research
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• 제43권2호
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• pp.75-84
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• 2018

Background: Gamma-ray spectrometry helps in radiation shielding problems and different applications of radioisotopes. Experimental arrangements including broad beam geometries are widely used. The aim is to investigate and evaluate the ${\gamma}-ray$ spectra via attenuation by environmental materials. Materials and Methods: The photo peak to nominated parts in the ${\gamma}-ray$ spectra and the attenuation coefficients ${\mu}_b/{\rho}$ from broad beam geometries are measured for the materials water, soil, sand and cement at the energies 0.662, 1.25, and 1.332 MeV with a $3{^{\prime}^{\prime}}{\times}3{^{\prime}^{\prime}}$ NaI(Tl) detector. Results and Discussion: The ${\gamma}-ray$ spectra vary according to changes in the effective atomic number $Z_{eff}$ of the attenuator, the photon energy and the solid angle. The peak to total ratios are the most sensitive parts to variations in the experimental conditions and overturn in the region 0.663 MeV to 1.332 MeV. This is indicated as inversion trend. The results are discussed in view of $Z_{eff}$ and the experimental conditions. The intensity build-up is larger at the lower energy and larger scattering angles in agreement with Klein-Nishina formula and other results. The build-up factor B is$${\sim_=}$$1 at high ${\gamma}-energies$ and small scattering angles. Conclusion: The sensitivity to material characteristics decrease gradually from peak: to total, to Compton valley, to Compton plateau ratios. Rigorous collimation is necessary at small energies. Cement, of the largest $Z_{eff}$, is characterized by the maximum broad beam mass attenuation coefficients ${\mu}_b/{\rho}$. The obtained results provide information to decide for the suitable experimental set-up based on aim of the work.

• Journal of Radiation Protection and Research
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• 제41권3호
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• pp.206-210
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• 2016

Background: Ionizing radiation causes cellular damage and death through the direct damage and/or indirectly the production of ROS, which induces oxidative stress. This study was designed to evaluate the in vivo radioprotective effects of a bio-active material coated fabric (BMCF) against ${\gamma}$-irradiation-induced cellular damage in Sprague-Dawley (SD) rats. Materials and Methods: Healthy male SD rats wore bio-active material coated (concentrations in 10% and 30%) fabric for 7 days after 3 Gy of ${\gamma}$-irradiation. Radioprotective effects were evaluated by performing various biochemical assays including spleen and thymus index, WBC count, hepatic damage marker enzymes [aspartate transaminase (AST) and alanine transaminase (ALT)] in plasma, liver antioxidant enzymes, and mitochondrial activity in muscle. Results and Discussions: Exposure to ${\gamma}$-irradiation resulted in hepatocellular and immune systemic damage. Gamma-irradiation induced decreases in antioxidant enzymes. However, wearing the BMCF-30% decreased significantly AST and ALT activities in plasma. Furthermore, wearing the BMCF-30% increased SOD (superoxide dismutase) and mitochondrial activity. Conclusion: These results suggest that wearing BMCF offers effective radioprotection against ${\gamma}$-irradiation-induced cellular damage in SD rats.

• Journal of Radiation Protection and Research
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• 제28권2호
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• pp.127-135
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• 2003

The primary contributors to the total occupational radiation exposure in operating nuclear power plants are operation and maintenance activities doting refueling outages. The Advanced Power Reactor 1400 (APR1400) includes a number of design improvements and plans to utilize advanced maintenance methods and robotics to minimize the annual collective dose. The major radiation exposure reduction features implemented in APR1400 are a permanent refueling pool seal, quick opening transfer tube blind flange, improved hydrogen peroxide injection at shutdown, improved permanent steam generator work platforms, and more effective temporary shielding. The estimated average annual occupational radiation exposure for APR1400 based on the reference plant experience and an engineering judgment is determined to be in the order of 0.4 man-Sv, which is well within the design goal of 1 man-Sv. The basis of this average annual occupational radiation exposure estimation is an eighteen (18) month fuel cycle with maintenance performed to steam generators and reactor coolant pumps during refueling outage. The outage duration is assumed to be 28 days. The outage work is to be performed on a 24 hour per day basis, seven (7) days a week with overlapping twelve (12) hour work shifts. The occupational radiation exposure for APR1400 is also determined by an alternate method which consists of estimating radiation exposures expected for the major activities during the refueling outage. The major outage activities that cause the majority of the total radiation exposure during refueling outage such as fuel handling, reactor coolant pump maintenance, steam generator inspection and maintenance, reactor vessel head area maintenance, decontamination, and ICI & instrumentation maintenance activities are evaluated at a task level. The calculated value using this method is in close agreement with the value of 0.4 man-Sv, that has been determined based on the experience aid engineering judgement. Therefore, with the As Low As Reasonably Achievable (ALARA) advanced design features incorporated in the design, APR1400 design is to meet its design goal with sufficient margin, that is, more than a factor of two (2), if operated on art eighteen (18) month fuel cycle.

• Journal of Radiation Protection and Research
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• 제42권4호
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• pp.177-188
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• 2017

Background: Radiation-induced pneumonitis and pulmonary fibrosis are common dose-limiting complications in patients receiving radiotherapy for lung, breast, and lymphoid cancers. In this study, we investigated the characteristics of effective immune cells related to pneumonitis and fibrosis after irradiation. Materials and Methods: After anesthesia, the whole thorax of C57BL/6 mice was irradiated at 14 Gy. The lung tissue and bronchoalveolar lavage fluid were collected at defined time points post-irradiation for the determination of histological and immunohistochemical analysis and inflammatory cell population infiltrated into the lung. Results and Discussion: Whole thoracic irradiation increased the deposition of extracellular matrix (ECM), lung weight, and pleural effusions, which started to die from 4 months later. At 4 months after irradiation, the numbers of macrophages and lymphocytes as well as neutrophils were increased dramatically in the lung. Interestingly, the macrophages that were recruited into the lung after irradiation had an enlarged foamy morphology. In addition, the expressions of chemokines (CCL-2, CCL-3, CXCL-10) for the attraction of macrophages and T cells were higher in the lung of irradiated mice. The high expressions of these chemokines were sustained up to 6 months following irradiation. In thoracic irradiated mice, infiltrated macrophages into the lung had the high levels of Mac-3 antigens on their surface and upregulated the hallmarks of alternatively activated macrophages such as arginase-1 and CD206. Furthermore, the levels of IL-4 and IL-13 were higher in a BAL fluid of irradiated mice. Conclusion: All results show that thoracic irradiation induces to infiltrate various inflammation-related immune cells, especially alternatively activated macrophages, through enhancing the expression of chemokines, suggesting that alternatively activated macrophages are most likely important for leading to pulmonary fibrosis.

• 한국해양공학회지
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• 제32권6호
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• pp.485-491
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• 2018

Because of the increase in coastal erosion problems, many studies have been conducted to prevent coastline retreat by developing low-cost, highly effective countermeasures. We developed the artificial coral reefs (ACRs) method as part of this research trend. To verify its coastal protection performance, we carried out performance tests on its wave attenuation and beach sand capture ability, which are the key barometers for this newly developed technology. In this study, three different types of methods, including natural beach, TTP, and ACRs, were used to determine the coastal protection efficiency under both ordinary and storm wave conditions. Based on the results of this study, ACRs were found to have the best wave attenuation performance and captured more than 20% of the total erosion area. This means the ACR method can be applied as a reliable countermeasure to protect a coastal zone.

• 한국지형학회지
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• 제25권4호
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• pp.37-47
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• 2018

Coastal sand dunes have been regarded as natural defenses to protect hinterland from disasters such as storm surge and typhoons. However, many dunes are not well-deserved in South Korea because of imprudent land development or inappropriate measures after coastal erosion. Lately, beach nourishment and dune reinforcement are emphasized as the effective and environmentally sustainable solution for the coastal protection. They are regarded good strategies to keep landscapes for a time, with little side effects. However, there is little knowledge on the construction methods including proper design and time plans for the best results.In addition, the effects of dune reinforcement in the field should be tested.In thisstudy, we performed sand filling in an eroded dune scarp and surveyed topographic changes in the beach-dune system, which is located along Dasa-ri coast, Chungnam Province, South Korea. Using a network RTK-GPS and drone-based aerial photographs, we analyzed the temporal and spatial changes in the area, before and after the reinforcement. As a result, the dune reinforcement seems to be helpful to mitigates the coastal erosion and to prevent the coastline retreat at least for one year.

• Journal of Radiation Protection and Research
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• 제48권1호
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• pp.15-19
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• 2023

Background: Cone beam computed tomography (CBCT) is a specialized medical equipment and plays a significant role in the diagnosis of oral and maxillofacial diseases and abnormalities; however, it is attributed to risk of exposure of ionizing radiation. The aim of the study was to estimate and determine the amount of scattered radiation dose to the thyroid gland in dental CBCT during maxilla and mandible scan. Materials and Methods: The average scattered radiation dose for i-CAT 17-19 Platinum CBCT (Imaging Sciences International) was measured using a Multi-O-Meter (Unfors Instruments), placed at the patient's neck on the skin surface of the thyroid cartilage, with an exposure parameter of 120 kVp and 37.07 mAs. The surface entrance dose was noted using the Multi-O-Meter, which was placed at the time of the scan at the level of the thyroid gland on the anterior surface of the neck. Results and Discussion: The surface entrance dose to the thyroid from both jaws scans was 191.491±78.486 µGy for 0.25 mm voxel and 26.9 seconds, and 153.670±74.041 µGy from the mandible scan, whereas from the maxilla scan the surface entrance dose was 5.259±10.691 µGy. Conclusion: The surface entrance doses to the thyroid gland from imaging of both the jaws, and also from imaging of the maxilla and mandible alone were within the threshold limit. The surface entrance dose and effective dose in CBCT were dependent on the exposure parameters (kVp and mAs), scan length, and field of view. To further reduce the radiation dose, care should be taken in selecting an appropriate protocol as well as the provision of providing shielding to the thyroid gland.

• Safety and Health at Work
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• 제13권4호
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• pp.394-400
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• 2022

Background: Impacts of exposure are generally monitored and recorded after injuries or illness occur. Yet, absence of conventional after-the-effect impacts (i.e., lagging indicators), tend to focus on physical health and injuries, and fail to inform if workers are not exposed to safety and health hazards. In contrast to lagging indicators, leading indicators are proactive, preventive, and predictive indexes that offer insights how effective safety and health. The present study is to validate an extended Voluntary Protection Programs (VPP) that consists of six leading indicators. Methods: Questionnaires were distributed to 13 organizations (response rate = 93.1%, 1,439 responses) in Taiwan. Cronbach α, multiple linear regression and canonical correlation were used to test the reliability of the extended Voluntary Protection Programs (VPP) which consists of six leading indicators (safe climate, transformational leadership, organizational justice, organizational support, hazard prevention and control, and training). Criteria-related validation strategy was applied to examine relationships of six leading indicators with six criteria (perceived health, burnout, depression, job satisfaction, job performance, and life satisfaction). Results: The results showed that the Cronbach's α of six leading indicators ranged from 0.87 to 0.92. The canonical correlation analysis indicated a positive correlation between the six leading indicators and criteria (1st canonical function: correlation = 0.647, square correlation = 0.419, p < 0.001). Conclusions: The present study validates the extended VPP framework that focuses on promoting safety and physical and mental health. Results further provides applications of the extended VPP framework to promote workers' safety and health.

• Journal of Radiation Protection and Research
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• 제48권3호
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• pp.131-143
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• 2023

Background: This study examined the detection limit of thyroid screening monitoring conducted at the time of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 using a Monte Carlo simulation. Materials and Methods: We calculated the detection limit of a NaI(Tl) survey meter to measure ¹³¹I accumulation in the thyroid gland of children. Mathematical phantoms of 1- and 5-year-old children were developed in the simulation of the Particle and Heavy Ion Transport code System code. Contamination of the body surface with eight radionuclides found after the FDNPP accident was assumed to have been deposited on the neck and shoulder area. Results and Discussion: The detection limit was calculated as a function of ambient dose rate. In the case of 40 Bq/cm² contamination on the body surface of the neck, the present simulations showed that residual thyroid radioactivity corresponding to thyroid dose of 100 mSv can be detected within 21 days after intake at the ambient dose rate of 0.2 µSv/hr and within 11 days in the case of 2.0 µSv/hr. When a time constant of 10 seconds was used at the dose rate of 0.2 µSv/hr, the estimated survey meter output error was 5%. Evaluation of the effect of individual differences in the location of the thyroid gland confirmed that the measured value would decrease by approximately 6% for a height difference of ±1 cm and increase by approximately 65% for a depth of 1 cm. Conclusion: In the event of a nuclear disaster, simple measurements carried out using a NaI(Tl) scintillation survey meter remain effective for assessing ¹³¹I intake. However, it should be noted that the presence of short-half-life radioactive materials on the body surface affects the detection limit.