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In YN, Kim HI, Park JS, Kang C, You Y, Min JH, Lee D, Lee IH, Jeong HS, Lee BK, Lee JK. Association between quantitative analysis of cerebral edema using CT imaging and neurological outcomes in cardiac arrest survivors. Am J Emerg Med 2024; 78:22-28. [PMID: 38181542 DOI: 10.1016/j.ajem.2023.12.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 12/10/2023] [Accepted: 12/22/2023] [Indexed: 01/07/2024] Open
Abstract
BACKGROUND To determine if the density distribution proportion of Hounsfield unit (HUdp) in head computed tomography (HCT) images can be used to quantitatively measure cerebral edema in survivors of out-of-hospital cardiac arrest (OHCA). METHODS This retrospective observational study included adult comatose OHCA survivors who underwent HCT within 6 h (first) and 72-96 h (second), all performed using the same CT scanner. Semi-automated quantitative analysis was used to identify differences in HUdp at specific HU ranges across the intracranial component based on neurological outcome. Cerebral edema was defined as the increased displacement of the sum of HUdp values (ΔHUdp) at a specific range between two HCT scans. Poor neurological outcome was defined as cerebral performance categories 3-5 at 6 months after OHCA. RESULTS Twenty-three (42%) out of 55 patients had poor neurological outcome. Significant HUdp differences were observed between good and poor neurological outcomes in the second HCT scan at HU = 1-14, 23-35, and 39-56 (all P < 0.05). Only the ΔHUdp = 23-35 range showed a significant increase and correlation in the poor neurological outcome group (4.90 vs. -0.72, P < 0.001) with the sum of decreases in the other two ranges (r = 0.97, P < 0.001). Multivariate logistic regression analysis demonstrated a significant association between ΔHUdp = 23-35 range and poor neurological outcomes (adjusted OR, 1.12; 95% CI: 1.02-1.24; P = 0.02). CONCLUSION In this cohort study, the increased displacement in ΔHUdp = 23-35 range is independently associated with poor neurological outcome and provides a quantitative assessment of cerebral edema formation in OHCA survivors.
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Affiliation(s)
- Yong Nam In
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Sejong Hospital, Daejoen, Republic of Korea
| | - Ho Il Kim
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Jung Soo Park
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea.
| | - Changshin Kang
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea
| | - Yeonho You
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea
| | - Jin Hong Min
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Sejong Hospital, Daejoen, Republic of Korea
| | - Dongyoung Lee
- Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea
| | - In Ho Lee
- Department of Radiology, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Hye Seon Jeong
- Department of Neurology, Chungnam National University Hospital, 266, Munhwa-ro, Jung-gu, Daejeon, Republic of Korea
| | - Byung Kook Lee
- Department of Emergency Medicine, Chonnam National University Medical School, Chonnam National Univesity Hospital, Gwangju, Republic of Korea
| | - Jae Kwang Lee
- Department of Emergency Medicine, Konyang University Hospital, College of Medicine, Republic of Korea
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Nam In Y, Ho Lee I, Soo Park J, Mi Kim Data Acquisition D, You Data Acquisition Y, Hong Min J, Jeong W, Jun Ahn H, Kang C, Kook Lee B. Delayed head CT in out-of-hospital cardiac arrest survivors: Does this improve predictive performance of neurological outcome? Resuscitation 2022; 172:1-8. [PMID: 35026330 DOI: 10.1016/j.resuscitation.2022.01.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 01/04/2022] [Accepted: 01/04/2022] [Indexed: 01/27/2023]
Abstract
BACKGROUND We compared the ability of head computed tomography (HCT) and MRI, respectively, obtained before or after target temperature management to predict neurologic outcomes in out-of-hospital cardiac arrest (OHCA) survivors. METHODS This retrospective study included adult comatose OHCA survivors who underwent neuroimaging scans within 6 h (first HCT) or 72-96 h (second HCT and MRI) after the return of spontaneous circulation (ROSC). We calculated the gray-white matter ratio (GWR), hypoxic-ischemic brain injury presence (loss of boundary at the basal ganglia level [LOB at BG], sulcal effacement at the centrum semiovale [SE at CS], and pseudo-SAH sign), and the overall score based on MRI findings (a total score of 21 brain regions individually scored according to the degree of signal abnormality). RESULTS Overall, 78 patients were included in this analysis, of whom 45 (58%) showed poor outcomes. The second HCT scan showed greater prognostic performance than the first HCT scan for GWR (area under curve 0.92 vs. 0.70), LOB at BG (0.93 vs. 0.65), SE at CS (0.89 vs. 0.64), and pseudo-SAH sign (0.75 vs. 0.51). The overall score on MRI (0.99) showed the highest prognostic performance. However, on the second HCT scan, the combination of GWR and LOB at BG showed prognostic performance (0.96) comparable to the overall score on MRI (P=0.12); the corresponding sensitivity and specificity values were 85.7% and 100%. CONCLUSIONS Overall score on MRI and the combination of GWR and LOB at BG findings on second HCT scans may help predict poor outcomes in OHCA survivors.
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Affiliation(s)
- Yong Nam In
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Sejong Chungnam National University Hospital, Daejoen, Republic of Korea
| | - In Ho Lee
- Department of Radiology, College of Medicine, Chungnam National University, 266, Munhwa-ro, Jung-gu, Daejeon, Republic of Korea
| | - Jung Soo Park
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea.
| | - Da Mi Kim Data Acquisition
- Department of Radiology, College of Medicine, Chungnam National University, 266, Munhwa-ro, Jung-gu, Daejeon, Republic of Korea
| | | | - Jin Hong Min
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Sejong Chungnam National University Hospital, Daejoen, Republic of Korea
| | - Wonjoon Jeong
- Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea
| | - Hong Jun Ahn
- Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea; Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea
| | - Changshin Kang
- Department of Emergency Medicine, Chungnam National University Hospital, Daejoen, Republic of Korea
| | - Byung Kook Lee
- Department of Emergency Medicine, Chonnam national University Medical School, Chonnam National Univesity Hospital, Gwangju, Republic of Korea
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Oh JH, Choi SP, Zhu JH, Kim SH, Park KN, Youn CS, Oh SH, Kim HJ, Park SH. Differences in the gray-to-white matter ratio according to different computed tomography scanners for outcome prediction in post-cardiac arrest patients receiving target temperature management. PLoS One 2021; 16:e0258480. [PMID: 34648574 PMCID: PMC8516299 DOI: 10.1371/journal.pone.0258480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 09/28/2021] [Indexed: 11/19/2022] Open
Abstract
The gray-to-white matter ratio (GWR) has been used to identify brain damage in comatose patients after cardiac arrest. However, Hounsfield units (HUs), the measurement of brain density on computed tomography (CT) images, may vary depending on the machine type or parameter. Therefore, differences in CT scanners may affect the GWR in post-cardiac arrest patients. We performed a retrospective study on comatose post-cardiac arrest patients who visited the hospital from 2007 to 2017. Two CT, Lightspeed and SOMATOM, scanners were used. Two observers independently measured the HUs of the caudate nucleus, putamen, posterior internal capsule, and corpus callosum using regions of interest. We compared the GWR calculated from the HUs measured at different CT scanners. The analysis of different scanners showed statistically significant differences in the measured HUs and GWR. The HUs and GWR of Lightspeed were measured lower than SOMATOM. The difference between the two CT scanners was also evident in groups divided by neurological prognosis. The area under the curve of the receiver operating characteristic curve to predict poor outcomes of Lightspeed was 0.798, and the cut-off value for 100% specificity was 1.172. The SOMATOM was 0.855, and the cut-off value was 1.269. The difference in scanners affects measurements and performance characteristics of the GWR in post-cardiac arrest patients. Therefore, when applying the results of the GWR study to clinical practice, reference values for each device should be presented, and an integrated plan should be prepared.
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Affiliation(s)
- Jae Hun Oh
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Eunpyeong St. Mary’s Hospital, Seoul, Republic of Korea
| | - Seung Pill Choi
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Eunpyeong St. Mary’s Hospital, Seoul, Republic of Korea
| | - Jong Ho Zhu
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Eunpyeong St. Mary’s Hospital, Seoul, Republic of Korea
| | - Soo Hyun Kim
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Eunpyeong St. Mary’s Hospital, Seoul, Republic of Korea
- * E-mail:
| | - Kyu Nam Park
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Seoul St. Mary’s Hospital, Seoul, Republic of Korea
| | - Chun Song Youn
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Seoul St. Mary’s Hospital, Seoul, Republic of Korea
| | - Sang Hoon Oh
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Seoul St. Mary’s Hospital, Seoul, Republic of Korea
| | - Han Joon Kim
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Seoul St. Mary’s Hospital, Seoul, Republic of Korea
| | - Sang Hyun Park
- Department of Emergency medicine, College of Medicine, The Catholic University of Korea, Yeouido St. Mary’s Hospital, Seoul, Republic of Korea
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Henson T, Rawanduzy C, Salazar M, Sebastian A, Weber H, Al-Mufti F, Mayer SA. Outcome and prognostication after cardiac arrest. Ann N Y Acad Sci 2021; 1508:23-34. [PMID: 34580886 DOI: 10.1111/nyas.14699] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/17/2021] [Accepted: 08/29/2021] [Indexed: 11/27/2022]
Abstract
The outcome after out-of-hospital cardiac arrest has historically been grim at best. The current overall survival rate of patients admitted to a hospital is approximately 10%, making cardiac arrest one of the leading causes of death in the United States. The situation is improving with the incorporation of therapeutic temperature modulation, aggressive prevention of secondary brain injury, and improved access to advanced cardiovascular support, all of which have decreased mortality and allowed for better outcomes. Mortality after cardiac arrest is often the direct result of active withdrawal of life-sustaining therapy based on the perception that neurological recovery is not possible. This reality highlights the importance of providing accurate estimates of neurological prognosis to decision makers when discussing goals of care. The current standard of care for assessing neurological status in patients with hypoxic-ischemic encephalopathy emphasizes a multimodal approach that includes five elements: (1) neurological examination off sedation, (2) continuous electroencephalography, (3) serum neuron-specific enolase levels, (4) magnetic resonance brain imaging, and (5) somatosensory-evoked potential testing. Sophisticated decision support systems that can integrate these clinical, imaging, and biomarker and neurophysiologic data and translate it into meaningful projections of neurological outcome are urgently needed.
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Affiliation(s)
| | | | | | | | - Harli Weber
- New York Medical College, Valhalla, New York
| | - Fawaz Al-Mufti
- Westchester Medical Center, Valhalla, New York.,New York Medical College, Valhalla, New York
| | - Stephan A Mayer
- Westchester Medical Center, Valhalla, New York.,New York Medical College, Valhalla, New York
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5
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Beekman R, Maciel CB, Ormseth CH, Zhou SE, Galluzzo D, Miyares LC, Torres-Lopez VM, Payabvash S, Mak A, Greer DM, Gilmore EJ. Early head CT in post-cardiac arrest patients: A helpful tool or contributor to self-fulfilling prophecy? Resuscitation 2021; 165:68-76. [PMID: 34147572 DOI: 10.1016/j.resuscitation.2021.06.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 05/21/2021] [Accepted: 06/10/2021] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Neuroprognostication guidelines suggest that early head computed tomography (HCT) might be useful in the evaluation of cardiac arrest (CA) patients following return of spontaneous circulation. We aimed to determine the impact of early HCT, performed within the first 6 h following CA, on decision-making following resuscitation. METHODS We identified a cohort of initially unconscious post-CA patients at a tertiary care academic medical center from 2012 to 2017. Variables pertaining to demographics, CA details, post-CA care, including neuroimaging and neurophysiologic testing, were abstracted retrospectively from the electronic medical records. Changes in management resulting from HCT findings were recorded. Blinded board-certified neurointensivists adjudicated HCT findings related to hypoxic-ischemic brain injury (HIBI) burden. The gray-white matter ratio (GWR) was also calculated. RESULTS Of 302 patients, 182 (60.2%) underwent HCT within six hours of CA (early HCT group). Approximately 1 in 4 early HCTs were abnormal (most commonly HIBI changes; 78.7%, n = 37), which resulted in a change in management in nearly half of cases (46.8%, n = 22). The most common changes in management were de-escalation in care [including transition to do not resuscitate status), withholding targeted temperature management, and withdrawal of life sustaining therapy (WLST)]. In cases with radiographic HIBI, mean [standard deviation] GWR was lower (1.20 [0.10] vs 1.30 [0.09], P < 0.001) and progression to brain death was higher (44.4% vs 2.9%; P < 0.001). The inter-rater reliability (IRR) of early HCT to determine presence of HIBI between radiology and three neurointensivists had a wide range (κ 0.13-0.66). CONCLUSION Early HCT identified abnormalities in 25% of cases and frequently influenced therapeutic decisions. Neuroimaging interpretation discrepancies between radiology and neurointensivists are common and agreement on severity of HIBI on early HCT is poor (k 0.11).
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Affiliation(s)
- Rachel Beekman
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States.
| | - Carolina B Maciel
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States; Department of Neurology, UF Health Shands Hospital, University of Florida College of Medicine, Gainesville, FL, 32611, United States
| | - Cora H Ormseth
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States
| | - Sonya E Zhou
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States
| | - Daniela Galluzzo
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States
| | - Laura C Miyares
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States
| | - Victor M Torres-Lopez
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States
| | - Seyedmehdi Payabvash
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06510, United States
| | - Adrian Mak
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06510, United States
| | - David M Greer
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States; Department of Neurology, Boston University School of Medicine, Boston, MA, 02118, United States
| | - Emily J Gilmore
- Department of Neurology, Yale School of Medicine, New Haven, CT, 06510, United States
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6
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Chen S, Lachance BB, Gao L, Jia X. Targeted temperature management and early neuro-prognostication after cardiac arrest. J Cereb Blood Flow Metab 2021; 41:1193-1209. [PMID: 33444088 PMCID: PMC8142127 DOI: 10.1177/0271678x20970059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Targeted temperature management (TTM) is a recommended neuroprotective intervention for coma after out-of-hospital cardiac arrest (OHCA). However, controversies exist concerning the proper implementation and overall efficacy of post-CA TTM, particularly related to optimal timing and depth of TTM and cooling methods. A review of the literature finds that optimizing and individualizing TTM remains an open question requiring further clinical investigation. This paper will summarize the preclinical and clinical trial data to-date, current recommendations, and future directions of this therapy, including new cooling methods under investigation. For now, early induction, maintenance for at least 24 hours, and slow rewarming utilizing endovascular methods may be preferred. Moreover, timely and accurate neuro-prognostication is valuable for guiding ethical and cost-effective management of post-CA coma. Current evidence for early neuro-prognostication after TTM suggests that a combination of initial prediction models, biomarkers, neuroimaging, and electrophysiological methods is the optimal strategy in predicting neurological functional outcomes.
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Affiliation(s)
- Songyu Chen
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Neurosurgery, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Brittany Bolduc Lachance
- Program in Trauma, Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Liang Gao
- Department of Neurosurgery, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiaofeng Jia
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Lee BK, Callaway CW, Coppler PJ, Rittenberger JC. The prognostic performance of brain ventricular characteristic differ according to sex, age, and time after cardiac arrest in comatose out-of-hospital cardiac arrest survivors. Resuscitation 2020; 154:69-76. [DOI: 10.1016/j.resuscitation.2020.05.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 05/20/2020] [Indexed: 12/13/2022]
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You Y, Min JH, Park JS, Cho YC, Jeong WJ, Ahn HJ, Kang C, Lee IH, Kang C, Lee BK, Youn CS. Cerebrospinal Fluid Volume Proportion Using Magnetic Resonance Imaging as a Predictor of Poor Neurological Outcome in Survivors of Out-of-Hospital Cardiac Arrest. Ther Hypothermia Temp Manag 2020; 11:110-116. [PMID: 32380938 DOI: 10.1089/ther.2020.0008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We aimed to investigate the prognostic performance of the proportion of cerebrospinal fluid volume (pCSV) using brain apparent diffusion coefficient-magnetic resonance imaging (ADC-MRI) in cardiac arrest (CA) survivors. This retrospective single-cohort study comprised adult comatose CA survivors who underwent brain MRI and targeted temperature management (TTM) from March 2018 to October 2019. We calculated pCSV (pCSV0 and pCSV72 within 6 and 72 hours after return of spontaneous circulation, respectively) using an automated quantitative analysis program. The difference between pCSV0 and pCSV72 was defined as the pCSVd. Neurologic outcome 3 months after CA was assessed with the Cerebral Performance Category scale and dichotomized as good (1 or 2) or poor (3-5). Of the 73 patients included, 44 (60.3%) had a poor neurological outcome. Patients with poor outcome had significantly lower pCSV at baseline and at 72 hours, and a negative change in pCSV over time. The prognostic performance of pCSV72 and pCSVd was significantly higher compared with pCSV0 (all p < 0.001). The pCSVd showed excellent area under the curve values (0.96; 95% confidence interval 0.85-0.99) and highest sensitivity (95%) at 100% specificity. pCSV on brain ADC-MRI was associated with 3-month neurologic outcome in CA survivors. The pCSVd is a highly predictive and sensitive marker of 3-month poor neurological outcome in CA survivors treated with TTM. Multicenter prospective studies are required to determine the generalizability of these results.
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Affiliation(s)
- Yenho You
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea
| | - Jin Hong Min
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea.,Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Jung Soo Park
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea.,Department of Emergency Medicine, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Yong Chul Cho
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea
| | - Won Joon Jeong
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea
| | - Hong Joon Ahn
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea
| | - Changshin Kang
- Department of Emergency Medicine, Chungnam National University Hospital, Daejeon, Republic of Korea
| | - In Ho Lee
- Department of Radiology, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Chan Kang
- Department of Orthopaedic Surgery, Chungnam National University School of Medicine, Daejeon, Republic of Korea
| | - Byung Kook Lee
- Department of Emergency Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Chun Song Youn
- Department of Emergency Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea
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