A Feasibility Study of Low-Dose Single-Scan Dual-Energy Cone-Beam CT in Many-View Under-Sampling Framework

Lee, Donghyeon,Lee, Jiseoc,Kim, Hyoyi,Lee, Taewon,Soh, Jeongtae,Park, Miran,Kim, Changhwan,Lee, Yeon Ju,Cho, Seungryong IEEE 2017 IEEE transactions on medical imaging Vol.36 No.12

<P>A single-scan dual-energy low-dose cone-beam CT (CBCT) imaging technique that exploits a multi-slit filter is proposed in this paper. The multi-slit filter installed between the x-ray source and the scanned object is reciprocated during a scan. The x-ray beams through the slits would generate relatively low-energy x-ray projection data, while the filtered beams would make high-energy projection data. An iterative image reconstruction algorithm that uses an adaptive-steepest-descent method to minimize image total-variation under the constraint of data fidelity was applied to reconstructing the image from the low-energy projection data. Since the high-energy projection data suffer from a substantially high noise level due to the beam filtration, we have developed a new algorithm that exploits the joint sparsity between the low-and high-energy CT images for image reconstruction of the high-energy CT image. The proposed image reconstruction algorithm uses a gradient magnitude image (GMI) of the low-energy CT image by regularizing the difference of GMIs of the low-and high-energy CT images to be minimized. The feasibility of the proposed technique has been demonstrated by the use of various phantoms in the experimental CBCT setup. Furthermore, based on the proposed dual-energy imaging, a material differentiation was performed and its potential utility has been shown. The proposed imaging technique produced promising results for its potential application to a low-dose single-scan dual-energy CBCT.</P>

Vitamin D Deficiency Is Associated with Rapid Decline in Exercise Capacity in Male Patients with Chronic Obstructive Pulmonary Disease

Kim, Changhwan,Jung, Ji Ye,Kim, Young Sam,Lee, Jae Seung,Rhee, Chin Kook,Lee, Jin Hwa,Lee, Ji-Hyun,Kim, Tae-Hyung,Lim, Seong Yong,Sheen, Seung Soo,Yoo, Kwang Ha,Seo, Joon Beom,Oh, Yeon-Mok,Lee, Sang-D S. Karger AG 2016 Respiration Vol.91 No.5

Graphene–Semiconductor Catalytic Nanodiodes for Quantitative Detection of Hot Electrons Induced by a Chemical Reaction

Lee, Hyosun,Nedrygailov, Ievgen I.,Lee, Young Keun,Lee, Changhwan,Choi, Hongkyw,Choi, Jin Sik,Choi, Choon-Gi,Park, Jeong Young American Chemical Society 2016 NANO LETTERS Vol.16 No.3

<P>Direct detection of hot electrons generated by exothermic surface reactions on nanocatalysts is an effective strategy to obtain insight into electronic excitation during chemical reactions. For this purpose, we fabricated a novel catalytic nanodiode based on a Schottky junction between a single layer of graphene and an n-type TiO2 layer that enables the detection of hot electron flows produced by hydrogen oxidation on Pt nanoparticles. By making a comparative analysis of data obtained from measuring the hot electron current (chemicurrent) and turnover frequency, we demonstrate that graphene's unique electronic structure and extraordinary material properties, including its atomically thin nature and ballistic electron transport, allow improved conductivity at the interface between the catalytic Pt nanoparticles and the support. Thereby, graphene-based nanodiodes offer an effective and facile way to approach the study of chemical energy conversion mechanisms in composite catalysts with carbon-based supports.</P>

Inherently Safer Process Design of Natural Gas Liquefaction Processes through Multiobjective Optimization-Part I. With Inherent Safety Indexes

Lee, Yongseok,Huh, Changhwan,Lee, Won Bo American Chemical Society 2019 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.58 No.10

<P>Inherent safety approach is the systematic strategy to achieve safety in the chemical plant by avoiding or reducing hazards through designing a safer process at the preliminary design stage. In this study, a new decision making scheme of inherently safer process design will be proposed aiming at simultaneously considering the economic feasibility and process safety through multiobjective optimization via gProms Process builder v.1.1. The optimization employs a sequential quadratic programming (SQP) for the optimal solution of the complex nonlinear programming (NLP) problem. The proposed method uses an inherent safety index of process route index (PRI) as the second objective function which could reflect the accidental situations and assesses the risk of fatality frequency [1/yr] at the optimal points by postcalculation using commercial quantitative risk assessment (QRA) software of SAFETI v.7.2. It is implemented to the natural gas liquefaction processes which clearly show the trade-off relation between two objective functions so that the effectiveness of the proposed method could be verified. Finally, the single-stage mixed refrigerant (SMR) process with TAC of 627 MM$/yr and fatality frequency of 1.28 × 10<SUP>-3</SUP>/yr is determined as the final optimal solution among other possible liquefaction processes studied. Consequently, this proposed approach and associated results could give reasonable guidelines to the designer who wants to decide not only the optimal design conditions but the structure of heat transfer also.</P> [FIG OMISSION]</BR>

Enhancement of Hot Electron Flow in Plasmonic Nanodiodes by Incorporating PbS Quantum Dots

Lee, Changhwan,Choi, Hyekyoung,Nedrygailov, Ievgen I.,Lee, Young Keun,Jeong, Sohee,Park, Jeong Young American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.5

<P>The enhancement, of hot electron generation using plasmonic nanostructures is a promising strategy for developing photovoltaic devices. Here, we show that hot electron flow generated in plasmonic Au/TiO2 nanodiodes by incident light can be amplified when PbS quantum dots are deposited onto the surface of the nanodiodes. The effect is attributed to efficient extraction of hot electrons via a three-dimensional Schottky barrier, thus giving new pathways for hot electron transfer. We also demonstrate a correlation between the photocurrent and Schottky barrier height when using PbS quantum dots with varying size and, ligand treatments that allow us to control the electric properties, (e.g., band gap. and Fermi, level, respectively) of the PbS quantum dots. This simple method introduces a new technique for further improving the power conversion efficiency of thin-film photovoltaic devices.</P>

Laboratory-acquired dengue virus infection by needlestick injury

Changhwan Lee,Eun Jung,Donghyok Kwon,Heun Choi,Jung Wan Park,Geun-Ryang Bae 대한직업환경의학회 2016 대한직업환경의학회지 Vol.28 No.-

Background: Dengue fever is one of the most dominant vector-borne diseases, putting approximately 3.9 billion people at risk worldwide. While it is generally vector-borne, other routes of transmission such as needlestick injury are possible. Laboratory workers can be exposed to dengue virus transcutaneously by needlestick injury. This is the first case, to our knowledge, of dengue virus infection by needlestick injury in a laboratory environment. This paper evaluates the risk and related health concerns of laboratory workers exposed to dengue virus. Case presentation: We evaluated a 30-year-old female laboratory worker exposed to the dengue virus by needlestick injury while conducting virus filtering. During admission, she showed symptoms of fever, nausea, myalgia, and a characteristic maculopapular rash with elevated aspartate aminotransferase (AST) of 235 IU/L and alanine aminotransferase (ALT) of 269 IU/L. She had been diagnosed by a positive nonstructural protein 1 (NS1) antigen (Ag) rapid test one day prior to symptom onset along with positive immunoglobulin M (IgM) enzymelinked immunosorbent assay (ELISA) on the ninth day of symptom onset. Reverse transcription polymerase chain reaction (RT-PCR), also conducted on the ninth day, was negative. After proper symptomatic treatment, she recovered without any sequelae. As a result of thorough epidemiologic investigation, it was determined that she had tried to recap the needle during the virus filtering procedure and a subsequent needlestick injury occurred. Conclusions: In the context of health promotion of laboratory workers, we suggest that the laboratory biosafety manual be revised and reinforced, and related prevention measures be implemented. Furthermore, health authorities and health care providers in Korea should be fully informed of proper dengue fever management.

Protective Effect of Citrus junos (Yuja) Peel and By-product against PM10-induced Lung Damage

Changhwan Lee,Soohak Chung,Sojung Park,Yunsik Kim 한국식품영양과학회 2020 한국식품영양과학회 학술대회발표집 Vol.2020 No.10

Strengthening epidemiologic investigation of infectious diseases in Korea: lessons from the Middle East Respiratory Syndrome outbreak

Changhwan Lee,Moran Ki 한국역학회 2015 Epidemiology and Health Vol.37 No.-

The recent outbreak of Middle East Respiratory Syndrome (MERS) coronavirus infection in Korea resulted in large socioeconomic losses. This provoked the Korean government and the general public to recognize the importance of having a well-established system against infectious diseases. Although epidemiologic investigation is one of the most important aspects of prevention, it has been pointed out that much needs to be improved in Korea. We review here the current status of the Korean epidemiologic service and suggest possible supplementation measures. We examine the current national preventive infrastructure, including human resources such as Epidemic Intelligence Service officers, its governmental management, and related policies. In addition, we describe the practical application of these resources to the recent MERS outbreak and the progress in preventive measures. The spread of MERS demonstrated that the general readiness for emerging infectious diseases in Korea is considerably low. We believe that it is essential to increase society’s investment in disease prevention. Fostering public health personnel, legislating management policies, and establishing research centers for emerging infectious diseases are potential solutions. Evaluating international preventive systems, developing cooperative measures, and initiating improvements are necessary. We evaluated the Korean epidemiologic investigation system and the public preventive measures against infectious diseases in light of the recent MERS outbreak. We suggest that governmental authorities in Korea enforce preventive policies, foster the development of highly qualified personnel, and increase investment in the public health domain of infectious disease prevention.

Sparse-view proton computed tomography using modulated proton beams : Sparse-view proton CT

Lee, Jiseoc,Kim, Changhwan,Min, Byungjun,Kwak, Jungwon,Park, Seyjoon,Lee, Se Byeong,Park, Sungyong,Cho, Seungryong Published for the American Association of Physicis 2015 Medical physics Vol.42 No.2

<P>Proton imaging that uses a modulated proton beam and an intensity detector allows a relatively fast image acquisition compared to the imaging approach based on a trajectory tracking detector. In addition, it requires a relatively simple implementation in a conventional proton therapy equipment. The model of geometric straight ray assumed in conventional computed tomography (CT) image reconstruction is however challenged by multiple-Coulomb scattering and energy straggling in the proton imaging. Radiation dose to the patient is another important issue that has to be taken care of for practical applications. In this work, the authors have investigated iterative image reconstructions after a deconvolution of the sparsely view-sampled data to address these issues in proton CT.</P>

Pre-validation study of alternative developmental toxicity test using mouse embryonic stem cell-derived embryoid bodies

Lee, Jae-Hwan,Park, Seon Young,Ahn, Changhwan,Kim, Cho-Won,Kim, Ji-eun,Jo, Na Rae,Kang, Hee Young,Yoo, Yeong-Min,Jung, Eui-Man,Kim, Eun Mi,Kim, Ki-Suk,Choi, Kyung-Chul,Lee, Sung Duck,Jeung, Eui-Bae Elsevier 2019 Food and chemical toxicology Vol.123 No.-

<P><B>Abstract</B></P> <P>The embryoid body test (EBT) is a developmental toxicity test method that assesses the half inhibitory concentrations of substances in the area of embryoid bodies (EBs), and in the viability of mouse embryonic stem cells (ESCs) and fibroblasts (3T3 cells) following chemical exposure for three and four days, respectively. In the previous study, the EBT showed more advanced than the embryonic stem cell test (EST) from the European Centre for the Validation of Alternative Methods (ECVAM) applying cardiac differentiation of mouse ESCs, because the EBT greatly reduced the exposure time, labor, and amount of materials required, and misclassification of embryotoxic potential. This pre-validation study evaluated the predictive accuracy of the EBT using 26 coded test substances by two steps: intra-laboratory and inter-laboratory reproducibility tests. Since some substances have different embryotoxic potentials at different pregnancy periods, in this study, a new prediction model consisting of non-toxic and toxic classes was used, instead of the existing prediction model assessing embryotoxicants in four classes. The results of the intra- and inter-laboratory tests were highly accurate (above 80%) when substances were classified using the predictive model. In conclusion, EBT can accurately classify various embryotoxicants in a short time with less effort and greater validation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The experiment was conducted to verify the embryo body test (EBT) method. </LI> <LI> Predictive models were created for two classifications (non-toxic and toxic). </LI> <LI> Experimental results showed high accuracy (above 80%). </LI> <LI> EBT can be used to classify embryotoxicants in the short term. </LI> </UL> </P>