• 한국동물학회지
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• 제15권3호
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• pp.95-100
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• 1972

回復複製(unscheduled DNA synthesis or repair replication)와 染色體交換 및 分裂活動과의 相關關係를 추구하기 위해 X-線을 處理한 4種의 哺乳動物 細胞를 材料로 回復複製 時期와 線量反應을 調査하였다. 回復複製는 調査한 4種의 細胞에서 모두 일어나고 그 率은 照射線量에 比例하며 細胞 種類에 따라 差가 난다. 그러나 回復複製가 일어나는 時期는 細胞 種類에 관계없이 X-線 照射후 2時間까지 지속되고 있다. 또 回復複製의 相對量은 細胞의 種族染色體數, 分裂活動 및 染色體交換率과 직접적인 관련이 없다. 分裂活動能力과 染色體交換은 다 線量에 比例하나 그 率은 逆比例 관계를 나타낸다.

• 한국의학물리학회지:의학물리
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• 제33권4호
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• pp.158-163
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• 2022

Purpose: We subjected scanning electron microscopic (SEM) images of the active layer of EBT3 film to texture analysis to determine the dose-response curve. Methods: Uncoated Gafchromic EBT3 films were prepared for direct surface SEM scanning. Absorbed doses of 0-20 Gy were delivered to the film's surface using a 6 MV TrueBeam STx photon beam. The film's surface was scanned using a SEM under 100× and 3,000× magnification. Four textural features (Homogeneity, Correlation, Contrast, and Energy) were calculated based on the gray level co-occurrence matrix (GLCM) using the SEM images corresponding to each dose. We used R-square to evaluate the linear relationship between delivered doses and textural features of the film's surface. Results: Correlation resulted in higher linearity and dose-response curve sensitivity than Homogeneity, Contrast, or Energy. The R-square value was 0.964 for correlation using 3,000× magnified SEM images with 9-pixel offsets. Dose verification was used to determine the difference between the prescribed and measured doses for 0, 5, 10, 15, and 20 Gy as 0.09, 1.96, -2.29, 0.17, and 0.08 Gy, respectively. Conclusions: Texture analysis can be used to accurately convert microscopic structural changes to the EBT3 film's surface into absorbed doses. Our proposed method is feasible and may improve the accuracy of film dosimetry used to protect patients from excess radiation exposure.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1807-1816
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• 2020

In this work, a Gaussian Process (Kriging) approach is proposed to provide efficient dose mapping for complex radiation fields using limited number of responses. Given a few response measurements (or simulation data points), the proposed approach can help the analyst in completing a map of the radiation dose field with a 95% confidence interval, efficiently. Two case studies are used to validate the proposed approach. The First case study is based on experimental dose measurements to build the dose map in a radiation field induced by a D-D neutron generator. The second, is a simulation case study where the proposed approach is used to mimic Monte Carlo dose predictions in the radiation field using a limited number of MCNP simulations. Given the low computational cost of constructing Gaussian Process (GP) models, results indicate that the GP model can reasonably map the dose in the radiation field given a limited number of data measurements. Both case studies are performed on the nuclear engineering radiation laboratories at the University of Sharjah.

• Asian Journal of Atmospheric Environment
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• 제12권1호
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• pp.1-16
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• 2018

Ground-level ozone ($O_3$) can be a menace for vegetation, especially in Asia where $O_3$ levels have been dramatically increased over the past decades. To ensure food security and maintain forest ecosystem services, such as nutrient cycling, carbon sequestration and functional diversity of soil biota, in the over-populated Asia, environmental standards are needed. To set proper standards, dose-response relationships should be established from which critical levels are derived. The predictor of the response in the dose-response relationship is an $O_3$ metric that indicates the dose level to which the plant has been exposed. This study aimed to review the relevant scientific literature and summarize the $O_3$ metrics used worldwide to provide insights for Asia. A variety of $O_3$ metrics have been used, for which we discuss their strengths and weaknesses. The most widely used metrics are based only on $O_3$ levels. Such metrics have been adopted by several regulatory agencies in the global. However, they are biologically irrelevant because they ignore the plant physiological capacity. Adopting AOT40 ($O_3$ mixing ratios Accumulated Over the Threshold of $40nmol\;mol^{-1}$) as the default index for setting critical levels in Asia would be a poor policy with severe consequences at national and Pan-Asian level. Asian studies should focus on flux-based $O_3$ metrics to provide relevant bases for developing proper standards. However, given the technical requirements in calculating flux-based $O_3$ metrics, which can be an important limitation in developing countries, no-threshold cumulative exposure indices like AOT0 should always accompany flux-based indices.

• Journal of Preventive Medicine and Public Health
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• 제29권1호
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• pp.27-41
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• 1996

This study described methods to predict human health risk associated with exposure to environmental carcinogens using animal bioassay data. Also, biological assumption for various dose-response models were reviewed. To illustrate the process of risk estimate using relevant dose-response models such as Log-normal, Mantel-Bryan, Weibull and Multistage model, we used four animal carcinogenesis bioassy data of chloroform and chloroform concentrations of tap water measured in large cities of Korea from 1987 to 1995. As a result, in the case of using average concentration in exposure data and 95% upper boud unit risk of Multistge model, excess cancer risk(RISK I) was about $1.9\times10^{-6}$, in the case of using probability distribution of cumulative exposure data and unit risks, those risks(RISK II) which were simulated by Monte-Carlo analysis were about $2.4\times10^{-6}\;and\;7.9\times10^{-5}$ at 50 and 95 percentile, respectively. Therefore risk estimated by Monte-Carlo analysis using probability distribution of input variables may be more conservative.

• Safety and Health at Work
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• 제9권3호
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• pp.290-295
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• 2018

Background: There is little information on the dose-response relationship between exposure to occupational carcinogenic agents and mesothelioma. This study aimed to investigate this association as well as the existence of agents other than asbestos that might cause mesothelioma. Methods: The Swedish component of the Nordic Occupational Cancer (NOCCA) study consists of 6.78 million individuals with detailed information on occupation. Mesothelioma diagnoses recorded in 1961-2009 were identified through linkage to the Swedish Cancer Registry. We determined cumulative exposure, time of first exposure, and maximum exposure intensity by linking data on occupation to the Swedish NOCCA job-exposure matrix, which includes 29 carcinogenic agents and corresponding exposure for 283 occupations. To assess the risk of mesothelioma, we used conditional logistic regression models to estimate hazard ratios and 95% confidence intervals. Results: 2,757 mesothelioma cases were identified in males, including 1,416 who were exposed to asbestos. Univariate analyses showed not only a significant excess risk for maximum exposure intensity, with a hazard ratio of 4.81 at exposure levels 1.25-2.0 fb/ml but also a clear dose-response effect for cumulative exposure with a 30-, 40-, and 50-year latency time. No convincing excess risk was revealed for any of the other carcinogenic agents included in the Swedish NOCCA job-exposure matrix. Conclusion: When considering asbestos exposure, past exposure, even for short periods, might be enough to cause mesothelioma of the pleura later in life.

• Journal of Radiation Protection and Research
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• 제23권1호
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• pp.17-23
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• 1998

자주달개비 4430 클론에 있어서 $^{252}Cf$ 중성자에 의해 유발되는 유전자 돌연변이의 선량반응 관계를 확립함과 동시에 TSH 분홍돌연변이를 유발함에 있어서 X-선에 대비한 중성자의 생물학적 효과비를 산출하였다. 돌연변이의 분석은 공시재료의 방사선조사 후 4주 이상 이뤄졌으며 최대변이율을 보이는 조사후 6일부터 13일까지의 분석결과로부터 돌연변이빈도를 산출하였다 가용한 실험범위 내에서 중성자 선량의 증가에 따라 돌연변이빈도의 선형적 증가 양상을 나타내었다. X-선에 비교하여 산출한 중성자의 RBE값은 3.1에서 6.8의 범위를 보였으며 이러한 값은 일반적으로 인지되고 있는 중성자의 RBE값에 비해 상당히 낮은 값이다.

• Journal of health informatics and statistics
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• 제41권3호
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• pp.318-323
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• 2016

Objectives: Except the known risk factors for stroke, few studies have identified novel metabolic markers that could effectively detect stroke at an early stage. In this study, we explored the dose-response relationship between serum metabolites and the incidence of stroke. Methods: We studied 213 adults in the Korean Cancer Prevention Study-II (KCPS-II) biobank and estimated dose-response relationship between serum metabolites and stroke (42 cases and 171 controls). Three serum metabolites (Acetylcholine, HexadecylAcetylGlycerol, and 1-acetyl-2-formyl-sn-glycero-3-phosphocholine) were used in this study. The analysis included (1) exploratory nonlinear analysis, (2) estimation of flexion points and slopes at below and above the points. In the model to estimate risk of incidence of stroke, we controlled for conventional risk factors such as age, sex, systolic blood pressure, type 2 diabetes, triglyceride, and smoking status. Results: The relationship between incidence of stroke and log-transformed 1-acetyl-2-formyl-sn-glycero-3-phosphocholine was non-linear with flexion point around intensity score of 8.8, whereas other metabolites, log-transformed Acetylcholine and HexadecylAcetylGlycerol, showed negative linear patterns. Conclusions: The study suggests that metabolic markers are associated with incidence of stroke, particularly, at or above the flexion point. The study result may contribute to developing a novel system for precise stroke prediction.

• Nutrition Research and Practice
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• 제15권3호
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• pp.329-345
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• 2021

BACKGROUD/OBJECTIVES: Evidence has suggested an association between serum vitamin D and metabolic syndrome (MetS), but prospective studies are very limited. The objective was to assess the dose-response association between serum vitamin D concentration and MetS risk using a systematic review and meta-analysis of updated observational studies. MATERIALS/METHODS: Using MEDLINE, PubMed, and Embase, a systematic literature search was conducted through February 2020 and the references of relevant articles were reviewed. A random-effects model was used to estimate the summary odds ratio/relative risk and 95% confidence interval (CI). Heterogeneity among studies was evaluated with I² statistic. In total, 23 observational studies (19 cross-sectional studies, and four cohort studies) were included in the meta-analysis. RESULTS: The pooled estimates (95% CI) for MetS per 25-nmol/L increment in serum vitamin D concentration were 0.80 (95% CI, 0.76-0.84; I² = 53.5) in cross-sectional studies, and 0.85 (95% CI, 0.72-0.98; I² = 85.8) in cohort studies. Similar results were observed, irrespectively of age of study population, study location, MetS criteria, and adjustment factors. There was no publication bias for the dose-response meta-analysis of serum vitamin D concentrations and MetS. CONCLUSIONS: Dose-response meta-analysis demonstrated that a 25-nmol/L increment in the serum vitamin D concentration was associated with 20% and 15% lower risks of MetS in cross-sectional studies and cohort studies, respectively.

• 대한두경부종양학회지
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• 제14권1호
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• pp.61-69
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• 1998

Objectives: The response rate of the radioactive iodine(RI) therapy with low dose was variable. Only a few studies reported the response and complication rate with high dose. The goal of this study was to access the ablation and complication rate after high dose of RI therapy (more than 100mCi) and to evaluate the factors affect the results. Material and Methods: During a period of 12 years, 225 patients received high dose of RI from 100 to 200mCi depending on the RI uptake in the whole body after total thyroidectomy. 100mCi of RI was given to 123 patients for ablation who showed the uptake only in the thyroid bed. 150mCi was given to another 84 patients for ablation who had uptake confined to the neck. The other 21 patients took more than 200mCi of RI because the whole body scan showed distant metastasis. Among these patients, the ablation and the complication rate was investigated. Results: Elevated level of the serum thyroglobulin(Tg) decreased less than 5ng/ml after RI therapy in all patients except two in the first group. The second group showed reduction of the serum Tg in 93%. Eighteen of the 21 patients in the third group are still alive after RI therapy. There were no fatal complications after high dose RI therapy and most of the complications were minimal and transient. The complication rate was not related with the dose of RI, age, sex, DNA flowcytometry, serum thyroglobulin level and the extent of node dissection. Conclusion: We concluded that RI therapy with high dose was very effective for thyroid ablation after operation and it also showed excellent results with minimal complications for treatment of metastatic lesions.