• Journal of Korean Neurosurgical Society
• /
• 제58권3호
• /
• pp.175-183
• /
• 2015

Objective : Intracranial ruptured vertebral artery dissecting aneurysms (VADAns) are associated with high morbidity and mortality when left untreated due to the high likelihood of rebleeding. The present study aimed to establish an endovascular therapeutic strategy that focuses specifically on the angioarchitecture of ruptured VADAns. Methods : Twenty-three patients with ruptured VADAn received endovascular treatment (EVT) over 7 years. The patient group included 14 women (60.9%) and 9 men (39.1%) between the ages of 39 and 72 years (mean age 54.2 years). Clinical data and radiologic findings were retrospectively analyzed. Results : Four patients had aneurysms on the dominant vertebral artery. Fourteen (61%) aneurysms were located distal to the posterior inferior cerebellar artery (PICA). Six (26%) patients had an extracranial origin of the PICA on the ruptured VA, and 2 patients (9%) had bilateral VADAns. Eighteen patients (78%) were treated with internal coil trapping. Two patients (9%) required an adjunctive bypass procedure. Seven patients (30%) required stent-supported endovascular procedures. Two patients experienced intra-procedural rupture during EVT, one of which was associated with a focal medullary infarction. Two patients (9%) exhibited recanalization of the VADAn during follow-up, which required additional coiling. No recurrent hemorrhage was observed during the follow-up period. Conclusion : EVT of ruptured VADAns based on angioarchitecture is a feasible and effective armamentarium to prevent fatal hemorrhage recurrence with an acceptable low risk of procedural complications. Clinical outcomes depend mainly on the pre-procedural clinical state of the patient. Radiologic follow-up is necessary to prevent hemorrhage recurrence after EVT.

• Journal of Korean Neurosurgical Society
• /
• 제63권4호
• /
• pp.470-476
• /
• 2020

Objective : The objective of this study was to develop a score to predict patients with acute ischemic stroke (AIS) who will not benefit from endovascular treatment (EVT) using computed tomographic angiography (CTA) parameters. Methods : The CTA-ABC score was developed from 3 scales previously described in the literature: the Alberta Stroke Program Early CT Score (0-5 points, 3; 6-10 points, 0), the clot burden score (0-3 points, 1; 4-10 points, 0), and the leptomeningeal Collateral score (0-1 points, 2; 2-3 points, 0). We evaluated the predictive value of CTA parameters associated with symptomatic intracranial hemorrhage (sICH) or malignant middle cerebral artery infarction (MMCAI) after EVT and developed the score using logistic regression coefficients. The score was then validated. Performance of the score was tested with an area under the receiver operating characteristic curve (AUC-ROC). Results : The derivation cohort consisted of 115 and the validation cohort consisted of 40 AIS patients. The AUC-ROC was 0.97 (95% confidence interval [CI], 0.94-0.99; p<0.001) in the derivation cohort. The proportions of patients with sICH and/or MMCAI in the derivation cohort were 96%, 73%, 6%, and 0% for scores of 6, 5, 1, and 0 points, respectively. In the validation group, the proportions were similar (90%, 100%, 0%, and 0%, respectively) with an AUC-ROC of 0.96 (95% CI, 0.90-1.00; p<0.001). Conclusion : Our CTA-ABC score reliably assessed risk for sICH and/or MMCAI in patients with AIS who underwent EVT. It can support clinical decision-making, especially when the need for EVT is uncertain.

• Journal of Cerebrovascular and Endovascular Neurosurgery
• /
• 제25권3호
• /
• pp.333-339
• /
• 2023

Aortic dissection is one of the causes of acute ischemic stroke. Endovascular recanalization therapy (EVT) has emerged as an essential treatment for acute ischemic stroke due to large artery occlusion. However, it is rarely performed in the situation of hidden aortic dissection (AD). Two patients presented to the emergency room with focal neurologic deficits. The first patient was diagnosed with right internal carotid artery (ICA) occlusion. Angiography revealed that the ICA was occluded by the dissection flap. After a stent deployment in the proximal ICA, the antegrade flow was restored. The patient was diagnosed with AD on chest computed tomography (CT) after EVT. For the second patient, intraarterial thrombectomy was performed to treat left middle cerebral artery occlusion. AD was first detected on echocardiography, which was performed after EVT. Herein, we report successful endovascular recanalization therapy performed in two patients with acute ischemic stroke in the situation of undiagnosed aortic dissection. We also reviewed previous case reports and relevant literature.

• 한국엔터테인먼트산업학회논문지
• /
• 제14권8호
• /
• pp.91-102
• /
• 2020

본 연구는 뮤지컬 노래를 입체적이고 심도 있게 표현할 수 있는 발성기법을 적용하여 학술적 관점으로 분석하기 위함이다. 뮤지컬 노래를 부른다는 것은 단순히 음악적인 부분만으로 완성될 수 없으며, 장면과 인물의 정서 상태 등 다양한 부분의 분석이 수반되어야 한다. 이를 위해 연구의 기준을 극 구조, 가사 분석, 음악 형식 및 다이내믹의 영역까지 다각적으로 분석하였다. 이후 최종적으로 배우가 극과 음악의 정서를 담아 노래를 가장 잘 표현 할 수 있는 에스틸 보이스 트레이닝 시스템발성기법을 탐색하고 적용하였다. 분석에 적용하고자 하는 EVT는 목소리의 여섯 가지의 음색을 <스피치, 쏩/크라이, 팔세토, 트웽, 오페라, 벨팅>으로 구분하였다. 본 연구에서는 6가지 소리 이외에 성대와 후두의 위치까지 적용하여 효과적으로 노래를 표현할 수 있는 방법을 모색하였다. 연구대상은 뮤지컬 <엘리자벳>의 '아무것도'이다. '아무것도'는 주인공 엘리자벳이 부르는 노래로, 고통의 정점에 있는 자신의 모습과 갈등을 표출한다. 이 노래는 음악적으로도 'G#3-Gb5'의 음역대를 소화해야 하므로 다양한 소리 기법과 성구전환 테크닉을 다양하게 적용할 수 있다. 결과적으로 인물의 정서와 노래를 깊이 있게 구현하기 위해서는, 장면과 인물 분석 및 다양한 노래 테크닉이 조화롭게 적용 되어야 완성될 수 있음을 확인하였다.

• Korean Journal of Radiology
• /
• 제21권5호
• /
• pp.582-587
• /
• 2020

Objective: Endovascular thrombectomy (EVT) fails in approximately 20% of anterior circulation large vessel occlusion (AC-LVO). Nonetheless, the factors that affect clinical outcomes of non-recanalized AC-LVO despite EVT are less studied. The purpose of this study was to identify the factors affecting clinical outcomes in non-recanalized AC-LVO patients despite EVT. Materials and Methods: This was a retrospective analysis of clinical and imaging data from 136 consecutive patients who demonstrated recanalization failure (modified thrombolysis in cerebral ischemia [mTICI], 0-2a) despite EVT for AC-LVO. Data were collected in prospectively maintained registries at 16 stroke centers. Collateral status was categorized into good or poor based on the CT angiogram, and the mTICI was categorized as 0-1 or 2a on the final angiogram. Patients with good (modified Rankin Scale [mRS], 0-2) and poor outcomes (mRS, 3-6) were compared in multivariate analysis to evaluate the factors associated with a good outcome. Results: Thirty-five patients (25.7%) had good outcomes. The good outcome group was younger (odds ratio [OR], 0.962; 95% confidence interval [CI], 0.932-0.992; p = 0.015), had a lower incidence of hypertension (OR, 0.380; 95% CI, 0.173-0.839; p = 0.017) and distal internal carotid artery involvement (OR, 0.149; 95% CI, 0.043-0.520; p = 0.003), lower initial National Institute of Health Stroke Scale (NIHSS) (OR, 0.789; 95% CI, 0.713-0.873; p < 0.001) and good collateral status (OR, 13.818; 95% CI, 3.971-48.090; p < 0.001). In multivariate analysis, the initial NIHSS (OR, 0.760; 95% CI, 0.638-0.905; p = 0.002), good collateral status (OR, 14.130; 95% CI, 2.264-88.212; p = 0.005) and mTICI 2a recanalization (OR, 5.636; 95% CI, 1.216-26.119; p = 0.027) remained as independent factors with good outcome in non-recanalized patients. Conclusion: Baseline NIHSS score, good collateral status, and mTICI 2a recanalization remained independently associated with clinical outcome in non-recanalized patients. mTICI 2a recanalization would benefit patients with good collaterals in non-recanalized AC-LVO patients despite EVT.

• 디지털산업정보학회논문지
• /
• 제14권3호
• /
• pp.77-85
• /
• 2018

Multi-User Multiple-Input Multiple-Output (MU-MIMO) is the core technology for improving the channel capacity compared to Single-User MIMO (SU-MIMO) by using multiuser gain and spatial diversity. Key problem for the MU-MIMO is the user selection which is the grouping the users optimally. To solve this problem, we adopt Extreme Value Theory (EVT) at the beginning of the proposed algorithm, which defines a primary user set instead of a single user that has maximum channel power according to a predetermined threshold. Each user in the primary set is then paired with all of the users in the system to define user groups. By comparing these user groups, the group that produces a maximum sum rate can be determined. Through computer simulations, we have found that the proposed method outperforms the conventional technique yielding a sum rate that is 0.81 bps/Hz higher when the transmit signal to noise ratio (SNR) is 30 dB and the total number of users is 100.

• Journal of Chest Surgery
• /
• 제56권5호
• /
• pp.362-366
• /
• 2023

The stomach has become the most commonly used site for grafts to replace the esophagus in esophageal cancer surgery because of its good blood supply and ability to enable single-reconstruction anastomosis. However, anastomotic failure is a serious complication after esophageal cancer surgery. Unlike anastomotic leakage due to local ischemia, gastric tube necrosis is a life-threatening condition with a high mortality rate. Gastric tube necrosis involves extensive ischemia due to a decreased blood supply, and an urgent operation is mandatory in most cases. Endoscopic vacuum therapy (EVT) has been used for anastomotic leakage after esophageal surgery. In recent years, it has been successfully used for more extensive disease, including large esophageal perforation as an indication for reoperation. Hence, we report a case of extensive gastric tube necrosis treated by EVT after an Ivor Lewis operation.

• 응용통계연구
• /
• 제20권2호
• /
• pp.291-311
• /
• 2007

전 세계적으로 금융시장에서는 예측할 수 없는 대형 사건들이 지속적으로 일어나고 있으며, 특히 보험시장의 경우에는 대재해성(catastrophe)손실 등을 포함한 극단적 사건에 대한 예측이 날이 갈수록 어려워지고 있는바 극단적 위험관리에 대한 필요성이 증대되고 있다. 극단적 위험관리에 있어 분포의 꼬리영역만을 분리하여 그 정보를 최대로 이용하는 방법이 필요한데, 이러한 문제들을 해결하기 위해 극단치들의 움직임을 모형화 하는 소위 극단치 이론(Extreme Value Theory: EVT)을 이용하는 것이 요구된다. 극단치 이론은 현재 여러 분야에서 활용되고 있는데, 특히 금융시장에서는 극단적 변화가 미치는 영향을 분석하기 위해서 극단치 이론을 이용한 금융위험분석을 실시하고 있다. 본 연구에서는 위험관리에 있어서 극단치 이론의 중요성을 검토하고 보험사의 위험자본에 초점을 맞추어 손실 발생의 극단적 위험을 측정하고 이에 대비한 위험자본의 적정규모를 측정하여 보았다.

• Structural Engineering and Mechanics
• /
• 제74권1호
• /
• pp.55-67
• /
• 2020

The common practice to predict the characteristic structural load effects (LEs) in long reference periods is to employ the extreme value theory (EVT) for building limit distributions. However, most applications ignore that LEs are driven by multiple loading events and thus do not have the identical distribution, a prerequisite for EVT. In this study, we propose the composite extreme value modeling approach using clustering to (a) cluster initial blended samples into finite identical distributed subsamples using the finite mixture model, expectation-maximization algorithm, and the Akaike information criterion; (b) combine limit distributions of subsamples into a composite prediction equation using the generalized Pareto distribution based on a joint threshold. The proposed approach was validated both through numerical examples with known solutions and engineering applications of bridge traffic LEs on a long-span bridge. The results indicate that a joint threshold largely benefits the composite extreme value modeling, many appropriate tail approaching models can be used, and the equation form is simply the sum of the weighted models. In numerical examples, the proposed approach using clustering generated accurate extrema prediction of any reference period compared with the known solutions, whereas the common practice of employing EVT without clustering on the mixture data showed large deviations. Real-world bridge traffic LEs are driven by multi-events and present multipeak distributions, and the proposed approach is more capable of capturing the tendency of tailed LEs than the conventional approach. The proposed approach is expected to have wide applications to general problems such as samples that are driven by multiple events and that do not have the identical distribution.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 학술대회 논문집 정보 및 제어부문
• /
• pp.211-212
• /
• 2008

본 논문에서는 LCD 구동 모들 PCB의 기능 검사를 위한 자동 검사시스템인 EVT(Emulated Vision Tester)를 제안하고 구현하였다. 기존의 대표적인 자동검사 방법으로는 전기적 검사나 영상기반 검사방식이 있으나 전기적 검사만으로는 Timing이 주요한 변수가 되는 LED 장비에서는 검출할 수 없는 구동불량이 존재하며 영상기반 검사는 영상획득에 일관성이 결여되거나 Gray Scale의 구분이 불명확하며 검출결과의 재현성이 떨어진다. EVT 시스템은 Pattern Generator에서 인가된 입력 패턴 신호라 구동모듈을 통한 후 출력되는 디지털 신호를 직접 비교하여 패턴을 검사하고 아날로그 신호 (전압, 저항, 파형)의 이상 여부도 신속 정확하게 검사할 수 있는 H/W적인 방법이다. 높은 검출 신뢰도와 빠른 처리 속도 뿐만 아니라 간결한 시스템 구성으로 원가절감 실현 등 많은 장점을 가진다.