Sung Tae Kim

Inje University Paik Hospital, Sŏul, Seoul, South Korea

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Publications (174)617.86 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Background. In a brain-computer interface for stroke rehabilitation, motor imagery is a preferred means for providing a gateway to an effector action or behavior. However, stroke patients often exhibit failure to comply with motor imagery, and therefore their motor imagery performance is highly variable. Objective. We sought to identify motor cortical areas responsible for motor imagery performance in stroke patients, specifically by using a multivariate pattern analysis of functional magnetic resonance imaging data. Methods. We adopted an imaginary finger tapping task in which motor imagery performance could be monitored for 12 chronic stroke patients with subcortical infarcts and 12 age- and sex-matched healthy controls. We identified the typical activation pattern elicited for motor imagery in healthy controls, as computed over the voxels within each searchlight in the motor cortex. Then we measured the similarity of each individual's activation pattern to the typical activation pattern. Results. In terms of activation levels, the stroke patients showed no activation in the ipsilesional primary motor cortex (M1); in terms of activation patterns, they showed lower similarity to the typical activation pattern in the area than the healthy controls. Furthermore, the stroke patients were better able to perform motor imagery if their activation patterns in the bilateral supplementary motor areas and ipsilesional M1 were close to the typical activation pattern. Conclusions. These findings suggest functional roles of the motor cortical areas for compliance with motor imagery in stroke, which can be applied to the implementation of motor imagery-based brain-computer interface for stroke rehabilitation.
    Neurorehabilitation and neural repair. 07/2014;
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    ABSTRACT: This study aimed to evaluate the ultrasonographic findings for various types of vascular closure devices (VCDs) immediately after the angiographic procedure and at 6-month follow-up.
    Ultrasonography (Seoul, Korea). 07/2014;
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    ABSTRACT: Although a considerable number of patients suffer from cognitive impairments after stroke, the neural mechanism of cognitive recovery has not yet been clarified. Repeated resting-state functional magnetic resonance imaging (fMRI) was used in this study to examine longitudinal changes in the default-mode network (DMN) during the 6 months after stroke, and to investigate the relationship between DMN changes and cognitive recovery. Out of 24 initially recruited right-hemispheric stroke patients, 11 (eight males, mean age 55.7 years) successfully completed the repeated fMRI protocol. Patients underwent three fMRI sessions at 1, 3 and 6 months after stroke. Their DMNs were analysed and compared with those of 11 age-matched healthy subjects (nine males, mean age 56.2 years). Correlations between DMN connectivity and improvement of the cognitive performance scores were also assessed. The stroke patients were found to demonstrate markedly decreased DMN connectivity of the posterior cingulate cortex, precuneus, medial frontal gyrus and inferior parietal lobes at 1 month after stroke. At 3 months after stroke, the DMN connectivity of these brain areas was almost restored, suggesting that the period is critical for neural reorganization. The DMN connectivity of the dorsolateral prefrontal cortex in the contralesional hemisphere showed a significant correlation with cognitive function recovery in stroke patients, and should be considered a compensatory process for overcoming cognitive impairment due to brain lesion. This is the first longitudinal study to demonstrate the changes in DMN during recovery after stroke and the key regions influencing cognitive recovery.
    European Journal of Neuroscience 06/2014; · 3.75 Impact Factor
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    ABSTRACT: Phosphatidylcholine with deoxycholic acid (PC/DA) is widely used to reduce localized fat deposits with mild adverse effects. We previously demonstrated that PC induces lipolysis with mild PMN infiltration, while DA induces adipose tissue damage. Therefore, the aim of this study was to extend our understanding of the pro-inflammatory responses of PC, DA, and PC/DA.
    Life sciences. 05/2014;
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    ABSTRACT: Effective regulation of nanoparticle (NP) uptake facilitates the NP-based therapeutics and diagnostics. Here, we report the use of insulin and 2-deoxyglucose (2-DG) to modulate the cellular uptake of glucose-functionalized quantum dots (Glc-QDs) in C2C12 muscle cells. The cellular uptake of Glc-QDs can be modulated up to almost two-fold under insulin stimulation while be down-regulated in the presence of 2-DG. These results demonstrate the use of secondary regulators to control the cellular uptake of NPs through membrane protein recognition in a specific and fine-tunable fashion.
    Journal of materials chemistry. B, Materials for biology and medicine. 05/2014;
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    ABSTRACT: The purpose of this study was to propose new criteria for differentiating Pittsburgh compound B (PiB)-negative from PiB-positive subcortical vascular dementia (SVaD) using clinical and MRI variables. We measured brain amyloid deposition using PiB-PET in 77 patients with SVaD. All patients met DSM-IV criteria for vascular dementia and had severe white matter hyperintensities on MRI, defined as a cap or band ≥10 mm as well as a deep white matter lesion ≥25 mm. Eleven models were considered to differentiate PiB(-) from PiB(+) SVaD using 4 variables, including age, number of lacunes, medial temporal atrophy (MTA), and APOE ε4. The ideal cutoff values in each of the 11 models were selected using the highest Youden index. A total of 49 of 77 patients (63.6%) tested negative for PiB retention, while 28 (36.4%) tested positive for PiB retention. The ideal model for differentiating PiB(-) from PiB(+) SVaD was as follows: age ≤75 years, ≥5 lacunes, and MTA ≤3, which together yielded an accuracy of 67.5%. When patients meet the DSM-IV criteria for vascular dementia and also have severe white matter hyperintensities, younger age, greater number of lacunes, and lesser MTA, these are predictive of a PiB(-) scan in patients with SVaD. This study provides Class II evidence that the combination of younger age, greater number of lacunes, and lesser MTA identifies patients with SVaD at lower risk of Alzheimer disease pathology.
    Neurology 03/2014; · 8.25 Impact Factor
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    ABSTRACT: Gold nanoparticles provide an attractive and applicable scaffold for delivery of nucleic acids. In this review, we focus on the use of covalent and noncovalent gold nanoparticle conjugates for applications in gene delivery and interfering RNA technologies. We also discuss challenges in nucleic acid delivery, including endosomal entrapment/escape and active delivery/presentation of nucleic acids in the cell.Molecular Therapy (2014); doi:10.1038/mt.2014.30.
    Molecular Therapy 03/2014; · 7.04 Impact Factor
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    ABSTRACT: Repetitive transcranial magnetic stimulation (rTMS) influences the brain temporally beyond the stimulation period and spatially beyond the stimulation site. Application of rTMS over the primary motor cortex (M1) has been shown to lead to plastic changes in interregional connectivity over the motor system as well as alterations in motor performance. With a sequential combination of rTMS over the M1 and functional magnetic resonance imaging (fMRI), we sought changes in the topology of brain networks, and specifically the association of brain topological changes with motor performance changes. In a sham-controlled parallel group experimental design, real or sham rTMS was administered to each 15 healthy subjects without prior motor-related dysfunctions, over the right M1 at a high frequency of 10 Hz. Before and after the intervention, fMRI data were acquired during a sequential finger motor task using the left, non-dominant, hand. Changes in the topology of brain networks was assessed in terms of global and local efficiency, which measures the efficiency in transporting information at global and local scales respectively, provided by graph-theoretical analysis. Greater motor performance changes towards improvements after real rTMS were shown in individuals who exhibited more increases in global efficiency and more decreases in local efficiency. The enhancement of motor performance after rTMS is supposed to be associated with brain topological changes, such that global information exchange is facilitated while local information exchange is restricted.
    Brain connectivity. 02/2014;
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    ABSTRACT: Previous preclinical studies have suggested a close relationship between cerebrovascular disease (CVD) and Alzheimer's disease. However, a direct correlation between CVD and amyloid burden has not yet been shown in humans. If there is a relationship between CVD and amyloid burden, it is possible that the apolipoprotein E4 (APOE4) genotype may have an effect on this relationship because APOE4 is a risk factor for the development of AD. We therefore evaluated the effects of APOE4 on the relationship between white matter hyperintensities (WMH), a marker of CVD, and amyloid burden, measured by 11C-Pittsburgh compound B (PiB) PET. We recruited 53 patients with subcortical vascular cognitive impairments, who had both WMH on MRI and amyloid deposition assessed by PiB PET. Twenty-two of these patients were APOE4 carriers (41.5%). In the APOE4 non-carriers, a significant positive correlation was shown between the volume of WMH and PiB retention (β = 7.0 × 10-3, p = 0.034) while no significant correlation was found in APOE4 carriers (β = -9.0 × 10-3, p = 0.085). Statistical parametric mapping analyses in APOE4 non-carriers showed that WMH were associated with PiB retention in the bilateral medial occipitotemporal gyrus, cuneus, and superior cerebellum. Our results suggested that WMH are correlated with amyloid burden especially in the posterior brain regions in APOE4 non-carriers. However, this correlation was not observed in APOE4 carriers, perhaps because in these subjects the influence of APOE4 overrides the effect of CVD.
    Journal of Alzheimer's disease: JAD 02/2014; · 4.17 Impact Factor
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    ABSTRACT: IMPORTANCE Cerebrovascular disease (CVD) and Alzheimer disease are significant causes of cognitive impairment in the elderly. However, few studies have evaluated the relationship between CVD and β-amyloid burden in living humans or their synergistic effects on cognition. Thus, there is a need for better understanding of mild cognitive impairment (MCI) before clinical deterioration begins. OBJECTIVE To determine the synergistic effects of β-amyloid burden and CVD on cognition in patients with subcortical vascular MCI (svMCI). DESIGN, SETTING, AND PARTICIPANTS A cross-sectional study was conducted using a hospital-based sample at a tertiary referral center. We prospectively recruited 95 patients with svMCI; 67 of these individuals participated in the study. Forty-five patients with amnestic MCI (aMCI) were group matched with those with svMCI by the Clinical Dementia Rating Scale Sum of Boxes. MAIN OUTCOMES AND MEASURES We measured β-amyloid burden using positron emission tomography with carbon 11-labeled Pittsburgh Compound B (PiB). Cerebrovascular disease was quantified as white matter hyperintensity volume detected by magnetic resonance imaging fluid-attenuated inversion recovery. Detailed neuropsychological tests were performed to determine the level of patients' cognitive impairment. RESULTS On evaluation, 22 of the svMCI group (33%) and 28 of the aMCI group (62%) were found to be PiB positive. The mean PiB retention ratio was lower in patients with svMCI than in those with aMCI. In svMCI, the PiB retention ratio was associated with cognitive impairments in multiple domains, including language, visuospatial, memory, and frontal executive functions, but was associated only with memory dysfunction in aMCI. A significant interaction between PiB retention ratio and white matter hyperintensity volume was found to affect visuospatial function in patients with svMCI. CONCLUSIONS AND RELEVANCE Most patients with svMCI do not exhibit substantial amyloid burden, and CVD does not increase β-amyloid burden as measured by amyloid imaging. However, in patients with svMCI, amyloid burden and white matter hyperintensity act synergistically to impair visuospatial function. Therefore, our findings highlight the need for accurate biomarkers, including neuroimaging tools, for early diagnosis and the need to relate these biomarkers to cognitive measurements for effective use in the clinical setting.
    JAMA Psychiatry 02/2014; · 12.01 Impact Factor
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    ABSTRACT: Hemangioblastoma is a benign and highly vascular tumor. Complete surgical resection of highly vascular tumor such as hemangioblastoma may be challenging due to excessive bleeding. Preoperative embolization of these lesions may decrease the intraoperative blood loss and facilitate excision. We report three cases of cerebellar hemangioblastomas that were embolized using Onyx.
    Neurointervention. 02/2014; 9(1):45-49.
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    ABSTRACT: Background: A large number of Alzheimer's disease (AD) studies have focused on medial temporal and cortical atrophy, while changes in the basal ganglia or thalamus have received less attention. Objective: The aim of this study was to investigate the existence of progressive topographical shape changes in the basal ganglia (caudate nucleus, putamen, and globus pallidus) and thalamus concurrent with AD disease progression over three years. This study also examined whether declines in volumes of the basal ganglia or thalamus might be responsible for cognitive decline in patients with AD. Methods: Thirty-six patients with early stage AD and 14 normal control subjects were prospectively recruited for this study. All subjects were assessed with neuropsychological tests and MRI at baseline and Years 1 and 3. A longitudinal shape analysis of the basal ganglia and thalamus was performed by employing a boundary surface-based shape analysis method. Results: AD patients exhibited specific regional atrophy in the right caudate nucleus and the bilateral putamen at baseline, and as the disease progressed, regional atrophic changes in the left caudate nucleus were found to conform to a distinct topography after controlling the total brain volume. Volumetric decline of the caudate nucleus and putamen correlated with cognitive decline in frontal function after controlling for age, gender, education, follow-up years, and total brain volume changes. Conclusion: Our findings suggest that shape changes of the basal ganglia occurred regardless of whole brain atrophy as AD progressed and were also responsible for cognitive decline that was observed from the frontal function tests.
    Journal of Alzheimer's disease: JAD 01/2014; · 4.17 Impact Factor
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    ABSTRACT: The absence of Discs-large 1 (DLG1), the mouse ortholog of the Drosophila discs-large tumor suppressor, results in congenital hydronephrosis characterized by urinary tract abnormalities, reduced ureteric bud branching, and delayed disconnection of the ureter from the common nephric duct (CND). To define the specific cellular requirements for Dlg1 expression during urogenital development, we used a floxed Dlg1 allele and Pax2-Cre, Pax3-Cre, Six2-Cre, and HoxB7-Cre transgenes to generate cell type-restricted Dlg1 mutants. In addition, we used RetGFP knockin and retinoic acid response element-lacZ transgenic mice to determine the effects of Dlg1 mutation on the respective morphogenetic signaling pathways. Mutation of Dlg1 in urothelium and collecting ducts (via HoxB7-Cre or Pax2-Cre) and in nephron precursors (via Pax2-Cre and Six2-Cre) resulted in no apparent abnormalities in ureteric bud branching or in distal ureter maturation, and no hydronephrosis. Mutation in nephrons, ureteric smooth muscle, and mesenchyme surrounding the lower urinary tract (via the Pax3-Cre transgene) resulted in congenital hydronephrosis accompanied by reduced branching, abnormal distal ureter maturation and insertion, and smooth muscle orientation defects, phenotypes very similar to those in Dlg1 null mice. Dlg1 null mice showed reduced Ret expression and apoptosis during ureter maturation and evidence of reduced retinoic acid signaling in the kidney. Taken together, these results suggest that Dlg1 expression in ureter and CND-associated mesenchymal cells is essential for ensuring distal ureter maturation by facilitating retinoic acid signaling, Ret expression, and apoptosis of the urothelium.
    Developmental Biology 01/2014; · 3.87 Impact Factor
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    ABSTRACT: Self-expanding stents are increasingly used for the treatment of complex intracranial aneurysms. The purpose of this study was to evaluate the usefulness and safety of a self-expanding nitinol stent (Enterprise) in the treatment of wide-necked intracranial aneurysms. This was a retrospective study of 39 patients with 40 wide-necked intracranial aneurysms who were enrolled in a single-center registry of patients treated with the Enterprise between June 2009 and December 2011. Thirty patients were asymptomatic, four had cerebrovascular accident sequelae, and five had suffered subarachnoid hemorrhage. One aneurysm had reopened after prior coil embolization, while 39 had not been treated. Clinical charts, procedural data, and angiographic results, including both immediate post-procedural angiograms and follow-up imaging, were reviewed. The mean neck size of the aneurysms was 5.58 mm (range 3-15.1 mm). Embolization was successful in all patients. There were five procedure-related events. There were no fatalities, but one procedure-related morbidity was noted. The immediate angiographic results included eight complete occlusions (20%), six remnant necks (15%), and 26 remnant sacs (65%). At angiographic follow-up (mean: 11.3 months), out of 18 of the aneurysms treated with stent-assisted coiling, there were 13 (72.2%) complete occlusions, four (22.2%) remnant necks, and one recanalization (5.6%). Stent-assisted coiling using the Enterprise is effective for the treatment of wide-necked intracranial aneurysms. Further angiographic and clinical follow-up investigation will be needed for evaluation of the long-term outcomes.
    Journal of cerebrovascular and endovascular neurosurgery. 12/2013; 15(4):299-306.
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    ABSTRACT: This study aimed to determine the optimal time for tracheostomy by evaluating the benefits and safety of early versus late tracheostomy in spinal cord injury (SCI) patients. We retrospectively reviewed a total of 254 patients with spinal cord injury. Of them, we selected 21 spinal cord injury patients who required tracheostomy due to long-term mechanical ventilation and analyzed their medical records. The patients were categorized into two groups. Early tracheostomy was performed day 1-10 from intubation in 10 patients and the late tracheostomy was performed after day 10 in 11 cases. We also evaluated the duration of mechanical ventilation, stay in the ICU and complications related to tracheostomy, the injury level of and clinical severity. All data was analyzed using SPSS 18.0/WIN. The early tracheostomy offered clear advantages for shortening the total ICU stay (20.8 day vs. 38.0 day, p=0.010). There was also statistically significant reduction in the total length of time on mechanical ventilation (5.2 day vs. 29.2 day, p=0.009). However, the reductions in the incidence of pneumonia (40% vs. 82%) and the length of ICU stay post to tracheostomy (6 day vs. 15 day) were found to be statistically not significant. There were also no statistically significant differences in the injury level and clinical severity between the groups. We concluded that the early tracheostomy (at least 10 days) is beneficial for SCI patients who are likely to require prolonged mechanical ventilation.
    Journal of Korean Neurosurgical Society 09/2013; 54(3):220-224. · 0.56 Impact Factor
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    Sung Tae Kim, Hae Woong Jeong, Jeonghwa Seo
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    ABSTRACT: We report our experience using Onyx for embolization of dural arteriovenous fistula (DAVF) under dual lumen balloon catheter flow arrest. Transfemoral cerebral angiography revealed a superior sagittal sinus (SSS) DAVF that was supplied via multiple branches of the external carotid arteries, the right anterior cerebral arteries, and the meningeal branches of the internal carotid artery. There was no anterograde venous drainage through the SSS, and venous drainage was almost retrograde through the medullary and cortical veins. Under general anesthesia, a transvenous approach was utilized to place the microcatheter close to the fistula site. After intravenous embolization with various coils, DAVF was partially occluded; Balloon catheter gained access to the DAVF via the right middle meningeal artery. We injected Onyx through the Scepter C catheter, after which DAVF was nearly completely occluded. Balloon-assisted Onyx embolization is a feasible and effective approach for the management of DAVF.
    Neurointervention. 09/2013; 8(2):110-4.
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    ABSTRACT: Imaging of nanomaterials in biological tissues provides vital information for the development of nanotherapeutics and diagnostics. Multiplexed imaging of different nanoparticles (NPs) greatly reduces costs, the need to use multiple animals, and increases the biodistribution information that can enhance diagnostic applications and accelerate the screening of potential therapeutics. Various approaches have been developed for imaging NPs; however, the readout of existing imaging techniques relies on specific properties of the core material or surface ligands, and these techniques are limited because of the relatively small number of NPs that can be simultaneously measured in a single experiment. Here, we demonstrate the use of laser desorption/ionization mass spectrometry (LDI-MS) in an imaging format to investigate surface chemistry dictated intra-organ distribution of NPs. This new LDI-MS imaging method enables multiplexed imaging of NPs with potentially unlimited readouts and without additional labeling of the NPs. It provides the capability to detect and image attomole levels of NPs with almost no interferences from biomolecules. Using this new imaging approach we find that the intra-organ distributions of same-sized NPs are directly linked to their surface chemistry.
    Journal of the American Chemical Society 08/2013; · 10.68 Impact Factor
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    ABSTRACT: Cerebrovascular disease (CVD) and amyloid burden are the most frequent pathologies in subjects with cognitive impairment. However, the relationship between CVD, amyloid burden, and cognition are largely unknown. We aimed to evaluate whether CVD (lacunes, white matter hyperintensities, and microbleeds) and amyloid burden (Pittsburgh compound B [PiB] retention ratio) contribute to cognitive impairment independently or interactively. We recruited 136 patients with subcortical vascular cognitive impairment who underwent magnetic resonance imaging, PiB-positron emission tomography, and neuropsychological testing. The number of lacunes was associated with memory, frontal dysfunctions, and disease severity. The volume of white matter hyperintensities and the PiB retention ratio were associated only with memory dysfunction. There was no direct correlation between CVD markers and PiB retention ratio except that the number of lacunes was negatively correlated with the PiB retention ratio. In addition, there were no interactive effects of CVD and PiB retention ratio on cognition. Our findings suggest that CVD and amyloid burden contribute independently and not interactively to specific patterns of cognitive dysfunction in patients with subcortical vascular cognitive impairment.
    Neurobiology of aging 08/2013; · 5.94 Impact Factor
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    ABSTRACT: Despite the predominant degeneration of subcortical structures, recent studies have suggested the evidence of cortical involvement in multiple system atrophy (MSA). This study aimed to identify the different topographic pattern of cortical thinning in MSA according to clinical subtypes, and the association of cortical thinning with cerebellar atrophy and other disease related metrics. We used cortical thickness analysis in 53 non-demented probable MSA patients (29 with MSA-C, 24 with MSA-P) and 35 healthy subjects and modeled local cortical thickness as a linear association with cerebellar volume and disease related metrics including age, disease duration, cognition and disease severity. We found five clusters (left ventromedial prefrontal, bilateral ventrolateral prefrontal cortex, right parahippocampal and lingual gyrus) exhibiting significant cortical thinning in MSA-C and two clusters (right primary sensory motor and left ventromedial prefrontal cortex) exhibiting a thinning tendency in MSA-P compared with the control group. In correlation analysis, we identified no cluster exhibiting a significant correlation with cerebellar atrophy in both of the MSA groups. However, cortical thickness in right parahippocampalgyrus and left ventrolateral prefrontal cortex showed significant negative correlation with International Cooperative Ataxia Rating Scale subscore of speech disorder in MSA-C group. We identified different topographic distributions of cortical thinning in MSA subtypes. Our study suggests that cortical thinning of MSA occurs independently of cerebellar atrophy as a primary disease process rather than secondary deafferentation.
    Parkinsonism & Related Disorders 07/2013; · 3.27 Impact Factor
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    ABSTRACT: We report a versatile hybrid membrane for sustained release therapeutic delivery systems. Chemically-directed assembly of a hybrid membrane of nanoparticles and dendrimers was integrated with a fluidic delivery device and a refillable drug reservoir, providing continuous sustained release.
    Nanoscale 07/2013; · 6.23 Impact Factor

Publication Stats

1k Citations
617.86 Total Impact Points

Institutions

  • 2014
    • Inje University Paik Hospital
      • Department of Radiology
      Sŏul, Seoul, South Korea
  • 2012–2014
    • Chung-Ang University
      • • College of Pharmacy
      • • School of Chemical Engineering and Materials Science
      Sŏul, Seoul, South Korea
    • University of Massachusetts Amherst
      • Department of Chemistry
      Amherst Center, Massachusetts, United States
    • Kyungpook National University Hospital
      • Department of Pathology
      Sŏul, Seoul, South Korea
    • Kyung Hee University
      • Department of Applied Chemistry
      Seoul, Seoul, South Korea
  • 2007–2014
    • Washington University in St. Louis
      • Department of Obstetrics and Gynecology
      San Luis, Missouri, United States
    • National Fisheries Research and Development Institution
      Sŏul, Seoul, South Korea
    • Inha University
      • Department of Polymer Science and Engineering
      Seoul, Seoul, South Korea
  • 2005–2014
    • Sungkyunkwan University
      • • Department of Physical Medicine and Rehabilitaion
      • • Department of Radiology
      • • Department of Neurology
      • • Samsung Medical Center
      Sŏul, Seoul, South Korea
  • 2013
    • Inje University
      Kŭmhae, South Gyeongsang, South Korea
  • 2011–2013
    • University of Pittsburgh
      • School of Pharmacy
      Pittsburgh, PA, United States
    • National Health Insurance Corporation Ilsan Hospital
      Sŏul, Seoul, South Korea
  • 2010–2013
    • Korea Institute of Construction Technology
      Kōyō, Gyeonggi Province, South Korea
    • Konkuk University Medical Center
      • Department of Neurology
      Changnyeong, South Gyeongsang, South Korea
    • Catholic University of Daegu
      • Department of Physical Therapy
      Hayang, North Gyeongsang, South Korea
    • Samsung Medical Center
      • Department of Neurosurgery
      Seoul, Seoul, South Korea
    • Woosong University
      Onyang, South Chungcheong, South Korea
  • 2004–2011
    • Korea University
      • College of Medicine
      Sŏul, Seoul, South Korea
  • 1997–2011
    • University of Cambridge
      • Department of Chemistry
      Cambridge, ENG, United Kingdom
  • 1995–2010
    • Seoul National University
      • • College of Pharmacy
      • • Division of Chemistry and Molecular Engineering
      Seoul, Seoul, South Korea
  • 2009
    • Yonsei University
      • Department of Prosthodontics
      Seoul, Seoul, South Korea
    • Hyundai Motor Company
      Sŏul, Seoul, South Korea
  • 2008–2009
    • University of Washington Seattle
      • Department of Obstetrics and Gynecology
      Seattle, WA, United States
  • 2004–2009
    • Ulsan University Hospital
      Urusan, Ulsan, South Korea
  • 2006–2008
    • Hanyang University
      • • Department of Biomedical Engineering
      • • College of Medicine
      Ansan, Gyeonggi, South Korea
  • 2004–2005
    • Konyang University Hospital
      Gaigeturi, Jeju, South Korea