Publications by authors named "Sanghyup Lee"

10 Publications

  • Page 1 of 1

Contrast-enhanced MRI T1 Mapping for Quantitative Evaluation of Putative Dynamic Glymphatic Activity in the Human Brain in Sleep-Wake States.

Radiology 2021 Jun 22:203784. Epub 2021 Jun 22.

From the Departments of Radiology (S.L., R.E.Y., S.H.C., J.Y.L., I.H., K.M.K., T.J.Y., J.H.K., C.H.S.) and Clinical Pharmacology and Therapeutics (K.Y.H.), Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehangno, Jongno-gu, Seoul 03080, Republic of Korea; Center for Nanoparticle Research, Institute for Basic Science, Seoul, Republic of Korea (S.H.C.); School of Chemical and Biological Engineering (S.H.C.) and Department of Electrical and Computer Engineering (S.J., J.L.), Seoul National University, Seoul, Republic of Korea; and Department of Biomedical Engineering, Hankuk University of Foreign Studies, Yongin-si, Republic of Korea (S.H.O.).

Background Evaluation of the glymphatic system with intrathecal contrast material injection has limited clinical use. Purpose To investigate the feasibility of using serial intravenous contrast-enhanced T1 mapping in the quantitative evaluation of putative dynamic glymphatic activity in various brain regions and to demonstrate the effect of sleep on glymphatic activity in humans. Materials and Methods In this prospective study from May 2019 to February 2020, 25 healthy participants (mean age, 25 years ± 2 [standard deviation]; 15 men) underwent two cycles of MRI (day and night cycles). For each cycle, T1 maps were acquired at baseline and 0.5, 1, 1.5, 2, and 12 hours after intravenous contrast material injection. For the night cycle, participants had a normal night of sleep between 2 and 12 hours. The time () to reach the minimum T1 value (T1), the absolute difference between baseline T1 and T1 (peak ΔT1), and the slope between two measurements at 2 and 12 hours (slope) were determined from T1 value-time curves in cerebral gray matter (GM), cerebral white matter (WM), cerebellar GM, cerebellar WM, and putamen. Mixed-model analysis of variance (ANOVA), Friedman test, and repeated-measures ANOVA were used to assess the effect of sleep on slope and to compare and peak ΔT1 among different regions. Results The slope increased from the day to night cycles in cerebral GM, cerebellar GM, and putamen (geometric mean ratio [night/day] = 1.4 [95% CI: 1.2, 1.7], 1.3 [95% CI: 1.1, 1.4], and 2.4 [95% CI: 1.6, 3.6], respectively; = .001, < .001, and < .001, respectively). Median values were 0.5 hour in cerebral and cerebellar GM and putamen for both cycles. Cerebellar GM had the highest mean peak ΔT1, followed by cerebral GM and putamen in both day (159 msec ± 6, 99 msec ± 4, and 62 msec ± 5, respectively) and night (152 msec ± 6, 104 msec ± 6, and 58 msec ± 4, respectively) cycles. Conclusion Clearance of a gadolinium-based contrast agent was greater after sleep compared with daytime wakefulness. These results suggest that sleep was associated with greater glymphatic clearance compared with wakefulness. © RSNA, 2021 . See also the editorial by Anzai and Minoshima in this issue.
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http://dx.doi.org/10.1148/radiol.2021203784DOI Listing
June 2021

Effectiveness of radiologist training in improving reader agreement for Lung-RADS 4X categorization.

Eur Radiol 2021 Apr 21. Epub 2021 Apr 21.

National Cancer Center, Goyang, South Korea.

Objectives: To identify the agreement on Lung CT Screening Reporting and Data System 4X categorization between radiologists and an expert-adjudicated reference standard and to investigate whether training led to improvement of the agreement measures and diagnostic potential for lung cancer.

Methods: Category 4 nodules in the Korean Lung Cancer Screening Project were identified retrospectively, and each 4X nodule was matched with one 4A or 4B nodule. An expert panel re-evaluated the categories and determined the reference standard. Nineteen radiologists were asked to determine the presence of CT features of malignancy and 4X categorization for each nodule. A review was performed in two sessions, and training material was given after session 1. Agreement on 4X categorization between radiologists and the expert-adjudicated reference standard and agreement between radiologist-assessed 4X categorization and lung cancer diagnosis were evaluated.

Results: The 48 expert-adjudicated 4X nodules and 64 non-4X nodules were evenly distributed in each session. The proportion of category 4X decreased after training (56.4% ± 16.9% vs. 33.4% ± 8.0%; p < 0.001). Cohen's κ indicated poor agreement (0.39 ± 0.16) in session 1, but agreement improved in session 2 (0.47 ± 0.09; p = 0.03). The increase in agreement in session 2 was observed among inexperienced radiologists (p < 0.05), and experienced and inexperienced reviewers exhibited comparable agreement performance in session 2 (p > 0.05). All agreement measures between radiologist-assessed 4X categorization and lung cancer diagnosis increased in session 2 (p < 0.05).

Conclusion: Radiologist training can improve reader agreement on 4X categorization, leading to enhanced diagnostic performance for lung cancer.

Key Points: • Agreement on 4X categorization between radiologists and an expert-adjudicated reference standard was initially poor, but improved significantly after training. • The mean proportion of 4X categorization by 19 radiologists decreased from 56.4% ± 16.9% in session 1 to 33.4% ± 8.0% in session 2. • All agreement measures between the 4X categorization and lung cancer diagnosis increased significantly in session 2, implying that appropriate training and guidance increased the diagnostic potential of category 4X.
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http://dx.doi.org/10.1007/s00330-021-07990-yDOI Listing
April 2021

Evaluation of the Impact of Iterative Reconstruction Algorithms on Computed Tomography Texture Features of the Liver Parenchyma Using the Filtration-Histogram Method.

Korean J Radiol 2019 Apr;20(4):558-568

Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, England, UK.

Objective: To evaluate whether computed tomography (CT) reconstruction algorithms affect the CT texture features of the liver parenchyma.

Materials And Methods: This retrospective study comprised 58 patients (normal liver, n = 34; chronic liver disease [CLD], n = 24) who underwent liver CT scans using a single CT scanner. All CT images were reconstructed using filtered back projection (FBP), hybrid iterative reconstruction (IR) (iDOSE⁴), and model-based IR (IMR). On arterial phase (AP) and portal venous phase (PVP) CT imaging, quantitative texture analysis of the liver parenchyma using a single-slice region of interest was performed at the level of the hepatic hilum using a filtration-histogram statistic-based method with different filter values. Texture features were compared among the three reconstruction methods and between normal livers and those from CLD patients. Additionally, we evaluated the inter- and intra-observer reliability of the CT texture analysis by calculating intraclass correlation coefficients (ICCs).

Results: IR techniques affect various CT texture features of the liver parenchyma. In particular, model-based IR frequently showed significant differences compared to FBP or hybrid IR on both AP and PVP CT imaging. Significant variation in entropy was observed between the three reconstruction algorithms on PVP imaging ( < 0.05). Comparison between normal livers and those from CLD patients revealed that AP images depend more strongly on the reconstruction method used than PVP images. For both inter- and intra-observer reliability, ICCs were acceptable (> 0.75) for CT imaging without filtration.

Conclusion: CT texture features of the liver parenchyma evaluated using the filtration-histogram method were significantly affected by the CT reconstruction algorithm used.
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http://dx.doi.org/10.3348/kjr.2018.0368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6424830PMC
April 2019

Abundant iron and sulfur oxidizers in the stratified sediment of a eutrophic freshwater reservoir with annual cyanobacterial blooms.

Sci Rep 2017 03 7;7:43814. Epub 2017 Mar 7.

Cell Factory Research Centre, Korea Research Institute of Bioscience &Biotechnology (KRIBB), Daejeon 34141, Republic of Korea.

The microbial community in eutrophic freshwater sediment was investigated from a 67-cm-deep sediment core collected from the Daechung Reservoir in South Korea, where cyanobacterial blooms have occurred annually for the past 30 years. The majority of core sediments were characterized by dark-grayish, fine-grained mud with abundant gas-escaped and thinly laminated layers. Intervals of summer and winter seasons were represented by periodic peaks of geochemical profiles of parameters such as grain size and relative carbon mass ratios to various nutrients such as nitrogen, sulfur, and phosphorus. In bacteria, Proteobacteria (66.6%) was the most prevalent phylum, followed by Chloroflexi (8.9%), Bacteroidetes (5.1%), and Spirochaetes (2.6%). Archaea were also abundant, representing approximately half of the total prokaryotes in the sediments. Notably, three Bacteria (Sulfuricurvum, Sideroxydans, and Gallionella) and one Archaea (Thermoplasmata) accounted for 43.4% and 38.4% of the total bacteria and archaea, respectively, implying that iron and sulfur oxidizing microorganisms dominate in this eutrophic freshwater sediment. These results indicate that 1) eutrophic freshwater lakes in monsoon climates undergo a stratified sedimentary process with seasonal and annual variations in geochemical and microbial profiles, and 2) the microbial oxidative metabolism of iron and sulfur is notably active in sediments from a eutrophic lake.
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http://dx.doi.org/10.1038/srep43814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5339789PMC
March 2017

Analysis of Aluminum Dust Cloud Combustion Using Flame Emission Spectroscopy.

Guang Pu Xue Yu Guang Pu Fen Xi 2015 Sep;35(9):2431-8

In this study, aluminum flame analysis was researched in order to develop a measurement method for high-energy-density metal aluminum dust cloud combustion, and the flame temperature and UV-VIS-IR emission spectra were precisely measured using a spectrometer. Because the micron-sized aluminum flame temperature was higher than 2400 K, Flame temperature was measured by a non-contact optical technique, namely, a modified two-color method using 520 and 640 nm light, as well as by a polychromatic fitting method. These methods were applied experimentally after accurate calibration. The flame temperature was identified to be higher than 2400 K using both methods. By analyzing the emission spectra, we could identify AlO radicals, which occur dominantly in aluminum combustion. This study paves the way for realization of a measurement technique for aluminum dust cloud combustion flames, and it will be applied in the aluminum combustors that are in development for military purposes.
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September 2015

Chemical behavior of different species of phosphorus in coagulation.

Chemosphere 2016 Feb 19;144:2264-9. Epub 2015 Nov 19.

Department of Energy Systems Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 151-744, Republic of Korea. Electronic address:

Phosphorus is one of the elements that have a significant impact on such environmental problems as eutrophication or algal bloom. Phosphorus compounds in water can be hydrolyzed to orthophosphate that is the only form of phosphorus that algae can assimilate. In this study, phosphorus removal in terms of orthophosphate and total phosphorus from wastewater was studied using alum or ferric ions as coagulants. It was observed that alum shows higher phosphorus removal efficiency than ferric ions in the same mole ratio concentrations. The proportion of orthophosphate among total phosphorus did not change significantly during coagulation process when the coagulant concentration is low. However, the proportion becomes gradually decreased as the coagulant concentration increases. Not only the electrolyte concentration difference in solution, but the characteristics of orthophosphate and polyphosphate such as reactivity and ionic size might also cause the differences in the removal rate. Orthophosphate that has greater reactivity than other phosphorus species would be involved in chemical reactions dominantly when large amounts of coagulants are applied. However, the effect of reactivity was diminished due to the large ionic size of polyphosphate and low concentration of electrolyte in low coagulant concentration during the coagulation process.
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http://dx.doi.org/10.1016/j.chemosphere.2015.10.131DOI Listing
February 2016

Oxidizing capacity of periodate activated with iron-based bimetallic nanoparticles.

Environ Sci Technol 2014 Jul 26;48(14):8086-93. Epub 2014 Jun 26.

Center for Water Resource Cycle, Korea Institute of Science and Technology , Seoul 136-791, Korea.

Nanosized zerovalent iron (nFe0) loaded with a secondary metal such as Ni or Cu on its surface was demonstrated to effectively activate periodate (IO4-) and degrade selected organic compounds at neutral pH. The degradation was accompanied by a stoichiometric conversion of IO4- to iodate (IO3-). nFe0 without bimetallic loading led to similar IO4- reduction but no organic degradation, suggesting the production of reactive iodine intermediate only when IO4- is activated by bimetallic nFe0 (e.g., nFe0-Ni and nFe0-Cu). The organic degradation kinetics in the nFe0-Ni(or Cu)/IO4- system was substrate dependent: 4-chlorophenol, phenol, and bisphenol A were effectively degraded, whereas little or no degradation was observed with benzoic acid, carbamazepine, and 2,4,6-trichlorophenol. The substrate specificity, further confirmed by little kinetic inhibition with background organic matter, implies the selective nature of oxidant in the nFe0-Ni(or Cu)/IO4- system. The comparison with the photoactivated IO4- system, in which iodyl radical (IO3•) is a predominant oxidant in the presence of methanol, suggests IO3• also as primary oxidant in the nFe0-Ni(or Cu)/IO4- system.
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http://dx.doi.org/10.1021/es5002902DOI Listing
July 2014

Caulobacter profunda sp. nov., isolated from deep freshwater sediment.

Int J Syst Evol Microbiol 2014 Mar 6;64(Pt 3):762-767. Epub 2013 Nov 6.

Environmental Biotechnology Research Center, Korea Research Institute of Bioscience & Biotechnology, 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.

The Gram-stain-negative, aerobic, non-spore-forming, motile, with a single polar flagellum, or non-motile (stalked) and rod-shaped bacteria, DS48-5-2(T) and DS48-6-3, were isolated from a sediment sample collected from a depth of 48 m taken from Daechung Reservoir, Republic of Korea. Comparative 16S rRNA gene sequence studies showed that the two isolates had clear affiliation with Alphaproteobacteria and the closest relatedness to Caulobacter mirabilis FWC 38(T), Caulobacter fusiformis ATCC 15257(T) and Caulobacter daechungensis H-E3-2(T) showing 98.5%, 97.3% and 97.3% 16S rRNA gene sequence similarity, respectively, and 96.1-96.7% similarity to all other species of the genus Caulobacter. The two isolates shared 100 % 16S rRNA gene sequence similarity. The predominant ubiquinone was Q-10. The major fatty acids were summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c), C16:0, C18:0ω7c 11-methyl and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c). The G+C contents of the genomic DNA of strains DS48-5-2(T) and DS48-6-3 were 66.7 mol% and 66.2 mol%, respectively. DNA-DNA hybridization values of strains DS48-5-2(T) and DS48-6-3 with C. mirabilis FWC 38(T), C. fusiformis ATCC 15257(T) and C. daechungensis H-E3-2(T) were 19.3 %-24.4 %. Thus, based on the evidence from polyphasic studies, it is proposed that strains DS48-5-2(T) and DS48-6-3 are representatives of a novel species in the genus Caulobacter, for which the name Caulobacter profunda sp. nov. is proposed. The type strain is DS48-5-2(T) ( = KCTC 32480(T) = JCM 19440(T)).
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http://dx.doi.org/10.1099/ijs.0.057240-0DOI Listing
March 2014

Selective oxidative degradation of organic pollutants by singlet oxygen-mediated photosensitization: tin porphyrin versus C60 aminofullerene systems.

Environ Sci Technol 2012 Sep 14;46(17):9606-13. Epub 2012 Aug 14.

Water Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea.

This study evaluates the potential application of tin porphyrin- and C(60) aminofullerene-derivatized silica (SnP/silica and aminoC(60)/silica) as (1)O(2) generating systems for photochemical degradation of organic pollutants. Photosensitized (1)O(2) production with SnP/silica, which was faster than with aminoC(60)/silica, effectively oxidized a variety of pharmaceuticals. Significant degradation of pharmaceuticals in the presence of the 400-nm UV cutoff filter corroborated visible light activation of both photosensitizers. Whereas the efficacy of aminoC(60)/silica for (1)O(2) production drastically decreased under irradiation with λ > 550 nm, Q-band absorption caused negligible loss of the photosensitizing activity of SnP/silica in the long wavelength region. Faster destruction of phenolates by SnP/silica and aminoC(60)/silica under alkaline pH conditions further implicated (1)O(2) involvement in the oxidative degradation. Direct charge transfer mediated by SnP, which was inferred from nanosecond laser flash photolysis, induced significant degradation of neutral phenols under high power light irradiation. Self-sensitized destruction caused gradual activity loss of SnP/silica in reuse tests unlike aminoC(60)/silica. The kinetic comparison of SnP/silica and TiO(2) photocatalyst in real wastewater effluents showed that photosensitized singlet oxygenation of pharmaceuticals was still efficiently achieved in the presence of background organic matters, while significant interference was observed for photocatalyzed oxidation involving non-selective OH radical.
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http://dx.doi.org/10.1021/es301775kDOI Listing
September 2012

Mobilization and deposition of iron nano and sub-micrometer particles in porous media: a glass micromodel study.

J Hazard Mater 2011 Sep 18;192(3):1466-75. Epub 2011 Jul 18.

School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, 261 Cheomdan-gwagiro, Buk-gu, 500-712 Gwangju, Republic of Korea.

Mobilization and deposition of iron nano and sub-micrometer particles (INSMP) in a porous medium were investigated using a water-saturated glass micromodel. The deposition and detachment of INSMP in the micromodel were visualized by taking serial images and experimentally verified by analysis of breakthrough curves. This first visualization study of INSMP fate showed that there were dense aggregations at the pores as the concentration of INSMP increased. The presence of dissolved humic substances (>1 ppm) significantly reduced deposition of suspended particles and enhanced detachment of the deposited particles. The mobility of INSMP in the presence of Pahokee peat fulvic acid standard II (PPFA) was higher than for Pahokee peat humic acid standard I (PPHA) due to the presence of more aromatic groups and the molecular weight in PPFA. Interfacial energy estimation based on the DLVO theory revealed that the adsorption of humic substances onto the INSMP increased the energy barrier and reduced the depth of secondary minimum between particles. The "affinity transition" in the initial deposition of INSMP within the micromodel was observed in the presence of Pahokee peat humic substances.
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http://dx.doi.org/10.1016/j.jhazmat.2011.06.066DOI Listing
September 2011
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