• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1826-1833
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• 2020

Administration of stable iodine has been considered a best measure to protect the thyroid from internal irradiation by radioiodine intake, and its efficacy on thyroid protection has been quantitatively evaluated in several simulation studies on the basis of simple iodine biokinetic models (i.e., three-compartment model). However, the new iodine biokinetic model adopted by the International Commission on Radiological Protection interprets and expresses the thyroid blocking phenomenon differently. Therefore, in this study, the new model was analyzed in terms of thyroid blocking and implemented to reassess the protective effects and to produce dosimetric data. The biokinetic model calculation was performed using computation modules developed by authors, and the results were compared with those of experimental data and prior simulation studies. The new model predicted protective effects that were generally consistent with those of experimental data, except for those in the range of stable iodine administration -72 h before radioiodine exposure. Additionally, the dosimetric data calculated in this study demonstrates a critical limitation of the three-compartment model in predicting bioassay functions, and indicated that dose assessment 1 d after exposure would result in a similar dose estimate irrespective of the administration time of stable iodine.

• Journal of Radiation Protection and Research
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• 제49권1호
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• pp.1-18
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• 2024

Exponential growth has been observed in nuclear medicine procedures worldwide in the past decades. The considerable increase is attributed to the advance of positron emission tomography and single photon emission computed tomography, as well as the introduction of new radiopharmaceuticals. Although nuclear medicine procedures provide undisputable diagnostic and therapeutic benefits to patients, the substantial increase in radiation exposure to nuclear medicine patients raises concerns about potential adverse health effects and calls for the urgent need to monitor exposure levels. In the current article, model-based internal dosimetry methods were reviewed, focusing on Medical Internal Radiation Dose (MIRD) formalism, biokinetic data, human anatomy models (stylized, voxel, and hybrid computational human phantoms), and energy spectrum data of radionuclides. Key results from many articles on nuclear medicine dosimetry and comparisons of dosimetry quantities based on different types of human anatomy models were summarized. Key characteristics of seven model-based dose calculation tools were tabulated and discussed, including dose quantities, computational human phantoms used for dose calculations, decay data for radionuclides, biokinetic data, and user interface. Lastly, future research needs in nuclear medicine dosimetry were discussed. Model-based internal dosimetry methods were reviewed focusing on MIRD formalism, biokinetic data, human anatomy models, and energy spectrum data of radionuclides. Future research should focus on updating biokinetic data, revising energy transfer quantities for alimentary and gastrointestinal tracts, accounting for body size in nuclear medicine dosimetry, and recalculating dose coefficients based on the latest biokinetic and energy transfer data.

• Journal of Radiation Protection and Research
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• 제46권4호
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• pp.170-177
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• 2021

Background: The International Commission on Radiological Protection is preparing to provide reference dose coefficients for environmental radioiodine intake based on newly developed age-specific biokinetic models. However, the biokinetics of iodine has been reported to be strongly dependent on the dietary intake of stable iodine; for example, the thyroidal uptake of iodine may be substantially lower in iodine-rich regions than in iodine-deficient regions. Therefore, this study attempted to establish a system of age-specific thyroid dose estimation for South Koreans, whose daily iodine intakes are significantly higher than that of the world population. Materials and Methods: Korean age-specific biokinetic parameters and thyroid masses were derived based on the previously developed Korean adult model and the Korean anatomical reference data for adults, respectively. This study complied with the principles used in the development of age-specific biokinetic models for world population and used the ratios of baseline values for each age group relative to the value for adults to derive age-specific values. Results and Discussion: Biokinetic model predictions based on the Korean age-specific parameters showed significant differences in iodine behaviors in the body compared to those predicted using the model for the world population. In particular, the Korean age-specific thyroid dose coefficients for ¹²⁹I and ¹³¹I were considerably lower than those calculated for the world population (25%-76% of the values for the world population). Conclusion: These differences stress the need for Korean-specific internal dose assessments for infants and children, which can be achieved by using the data calculated in this study.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2732-2739
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• 2024

This study developed internal dose coefficients for radioiodine, tailored to the Korean population, by incorporating the Korean biokinetic model along with the Korean S values. The observed differences in dose coefficients for Koreans compared to the International Commission on Radiological Protection (ICRP) reference values noticeably varied depending on physical half-lives of iodine isotopes. For longer-lived isotopes such as I-125 and I-129, significant differences in thyroid dose coefficients were observed, with ratios (Korean/ICRP) from 0.30 to 0.55, indicating that actual doses for Koreans can be considerably lower than those evaluated based on the ICRP data. However, for short-lived iodine isotopes, such as I-131, the thyroid dose coefficients were comparable to the ICRP reference values (ratio = 0.95-0.98). These comparable dose coefficients resulted from the lower thyroidal iodine uptake in the Korean model being almost entirely offset by the higher thyroid self-absorption S values in the Korean phantoms. Additionally, this study delves into the substantial differences in absorbed dose coefficients for non-thyroidal regions and effective dose coefficients, which arose not only from physiological/anatomical variability but also technical differences in phantom design. The use of Korean-specific dose coefficients is advisable particularly in scenarios predicting elevated doses, yielding a more precise and clinically relevant dose assessment.

• Journal of Microbiology and Biotechnology
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• 제30권4호
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• pp.533-539
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• 2020

A quantitative real-time polymerase chain reaction (QPCR) was applied to estimate biokinetic coefficients of Clostridium cadaveris and Clostridium sporogenes, which utilize protein as carbon source. Experimental data on changes in peptone concentration and 16S rRNA gene copy numbers of C. cadaveris and C. sporogenes were fitted to model. The fourth-order Runge-Kutta approximation with non-linear least squares analysis was employed to solve the ordinary differential equations to estimate biokinetic coefficients. The maximum specific growth rate (μ_max), half-saturation concentration (K_s), growth yield (Y), and decay coefficient (K_d) of C. cadaveris and C.sporogenes were 0.73 ± 0.05 and 1.35 ± 0.32 h^-1, 6.07 ± 1.52 and 5.67 ± 1.53 g/l, 2.25 ± 0.75 × 10¹⁰ and 7.92 ± 3.71 × 10⁹ copies/g, 0.002 ± 0.003 and 0.002 ± 0.001 h^-1, respectively. The theoretical specific growth rate of C. sporogenes always exceeded that of C. cadaveris at peptone concentration higher than 3.62 g/l. When the influent peptone concentration was 5.0 g/l, the concentration of C.cadaveris gradually decreased to the steady value of 2.9 × 10¹⁰ copies/ml at 4 h Hydraulic retention time (HRT), which indicates a 67.1% reduction of the initial population, but the wash out occurred at HRTs of 1.9 and 3.2 h. The 16S rRNA gene copy numbers of C. sporogenes gradually decreased to steady values ranging from 1.1 × 10¹⁰ to 2.9 × 10¹⁰ copies/ml. C. sporogenes species was predicted to wash out at an HRT of 1.6 h.

• Journal of Radiation Protection and Research
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• 제28권1호
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• pp.43-50
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• 2003

본 연구는 호흡을 통해 우라늄을 만성 또는 급성섭취한 경우 생물분석 결과의 해석을 통해 예탁유효선량을 평가하는 실질적인 방법을 기술하고 있다. 인체에서의 우라늄 거동의 해석을 위해 인체의 장기를 ICRP에서 권고하는 소화기 모델, 호흡기 모델 그리고 생체역동학적 모델에 따라 일련의 수학적 격실로 구성하였다. Birchall의 알고리듬을 이용하여 각 격실에서의 균형방정식의 해석적인 해를 얻었으며 우라늄의 소변 배설함수와 폐 잔류함수를 획득하였다. 소변 중 우라늄 농도와 폐 계수기로 측정된 폐 부하량에 각각 배설 및 잔류함수를 적용하여 섭취모드에 따른 초기 섭취량 또는 총 섭취량을 계산하였다. 예탁유효선량은 ICRP 78에서 제공하는 선량 환산계수를 계산된 섭취량에 적용함으로써 평가된다.

• 공업화학
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• 제10권3호
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• pp.349-353
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• 1999

페놀성 산업폐수중 2,4-dichlorophenol과 2,4-dinitrophenol를 함유한 폐수에 대해서 phenol이 활성슬러지공법에서 이 두 물질의 미생물 분해와 활성슬러지공정에 대한 Eckenfelder 수정모델의 미생물분해계수 (biodegradation kinetic coefficient)에 미치는 영향을 연구실험하였다. 미생물 성장에 필요한 에너지원과 필수영양물질 (base mix. BM)을 함유한 폐수를 분해하고 있는 활성슬러지 시스템에 2,4-dichlorophenol과 2,4-dinitrophenol를 함유한 폐수를 유입시켰을 때 이 활성슬러지 시스템은 서서히 죽어갔고 미생물들이 다 씻겨 나갔다. 반면에 페놀에 먼저 순화되어 있는 활성슬러지 시스템에 2,4-dichlorophenol과 2,4-dichlrophenol을 함유한 폐수를 phenol과 함께 유입하였을 때는 분해가 잘 되었고, 분해효율은 $BOD_5$ 기준으로 91.9%에 달했다. 그리고 phenol, 2,4-dichlorophenol 및 2,4-dinitrophenol의 처리효율은 각각 99.8%, 43.3% 및 62.5%였다. 같은 반응조에 연이어서 유입한 에너지원과 필수 영양물질의 추가공급은 처리효율을 상당히 증가시켜 처리수 중의 phenol, 2,4-dichlorophenol 및 2,4-dinitrophenol 농도를 현저히 감소시켰다. 이러한 효과는 페놀에 의해 순화되어 있는 미생물이 BM의 추가공급으로 활성도가 증가되어 분해효율이 증가되었다고 본다. 페놀에 대한 미생물의 순화과정 없이 실험하였을 때는 정상상태를 유지할 수 없었기 때문에 그 결과로부터는 Eckenfelder 수정모델의 미생물분해계수의 값을 구할 수가 없없다. 순화과정을 거친 경우의 미생물분해계수는 12.44/day이었고, 추가적인 $BM\;47mg/l(BOD_5)$의 첨가에 의해서는 46.91/day로 증가되었다. 이러한 값들은 공정설계시에 설계값으로 사용될 수 있고 다른 벤젠유도체의 미생물분해연구에 기초자료로도 활용 될 수 있을 것이다.

• 방사성폐기물학회지
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• 제2권2호
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• pp.113-124
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• 2004

본 연구에서는 인체 내에서 방사성핵종의 거동에 관하여 국제방사선방호위원회에서 권고한 최근 호흡기 모델, 소화기 모델 및 생체동역학 모델을 사용하여 생물학적분석 자료로부터 섭취량과 예탁유효선량을 평가하기 위한 BIDAS 프로그램을 개발하였다. 프로그램은 생물학적분석 자료를 관리하는 데이터베이스 모듈, 각 방사성 핵종에 대한 예측 생물학적분석 양을 내장하고 있는 모듈, 측정된 생물학적분석 양에 근거하여 급성 및 만성 피폭으로부터 섭취량과 선량을 평가하는 계산모듈 등으로 구성되어 있다. 본 논문은 프로그램의 특성과 검증결과에 대해 기술한다.

• 산업기술연구
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• 제20권A호
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• pp.73-82
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• 2000

This study was implemented to find an optimal model for wastewater treatment processes using PHOENICS(Parabolic, hyperbolic or Elliptic Numerical Integration Code Series) and ASM(Activated Sludge Model). PHOENICS is a general software based upon the laws of physics and chemistry which govern the motion of fluids, the stresses and strains in solids, heat flow, diffusion, and chemical reaction. The wastewater flow and removal efficiency of particle in two phase system of a grit chamber in wastewater treatment plant were analyzed to inquire the predictive aspect of the operational model. ASM was developed for a biokinetic model based upon material balance in complex activated sludge systems, which can demonstrate dynamic and spatial behavior of biological treatment system. This model was applied to aeration tank and settling chamber in Choonchun city, and the modeling result shows dynamic transport in aeration tank. PHOENCS and ASM could be contributed for the optimal operation of wastewater treatment plant.

• Advances in environmental research
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• 제1권1호
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• pp.15-35
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• 2012

Mercury (Hg) is a global environmental pollutant that has been the cause of many public concerns. One particular concern about Hg in aquatic systems is its trophic transfer and biomagnification in food chains. For example, the Hg concentration increases with the increase of food chain level. Fish at the top of food chain can accumulate high concentrations of Hg (especially the toxic form, methylmercury, MeHg), which is then transferred to humans through seafood consumption. Various biological and physiochemical conditions can significantly affect the bioaccumulation of Hg-including both its inorganic (Hg(II)) and organic (MeHg) forms-in fish. There have been numerous measurements of Hg concentrations in marine and freshwater fish worldwide. Many of these studies have attempted to identify the processes leading to variations of Hg concentrations in fish species from different habitats. The development of a biokinetic model over the past decade has helped improve our understanding of the mechanisms underlying the bioaccumulation processes of Hg in aquatic animals. In this review, I will discuss how the biokinetic modeling approach can be used to reveal the interesting biodynamics of Hg in fish, such as the trophic transfer and exposure route of Hg(II) and MeHg, as well as growth enrichment (the increases in Hg concentration with fish size) and biomass dilution (the decreases in Hg concentration with increasing phytoplankton biomass). I will also discuss the relevance of studying the subcellular fates of Hg to predict the Hg bioaccessibility and detoxification in fish. Future challenges will be to understand the inter- and intra-species differences in Hg accumulation and the management/mitigation of Hg pollution in both marine and freshwater fish based on our knowledge of Hg biodynamics.