• 한국멀티미디어학회논문지
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• 제10권3호
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• pp.316-324
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• 2007

의료영상에서 사용하는 MIP 볼륨 렌더링은 CT나 MR 등의 볼륨데이터에서 시각 광선으로부터 높은 밝기 값을 추출하여 혈관과 뼈와 같은 환자의 조직을 보여주는 볼륨 렌더링 기법이다. 최근 GPU를 MIP 볼륨 렌더링에 사용하여 대용량 의료영상 데이터에 대해서도 속도가 빠른 렌더링이 가능하게 되었다. 볼륨데이터를 여러 각도에서 관찰하면, 일반적으로 시각과 동일한 방향의 텍스쳐 평면과 볼륨 경계평면이 비스듬하게 교차한다. 볼륨데이터의 외부에는 값이 존재하지 않으므로 경계부분에서 공간 주파수가 높게 나타난다. 기존의 MIP 렌더링은 샘플링 간격이 일정하기 때문에 경계부분에서 데이터의 손실이 생겨 알리아싱이 나타나는 문제가 있다. 화질을 개선하기 위해 샘플링 간격을 줄여 슬라이스수를 증가시킬 수 있으나, 이때는 렌더링 수행 시간이 길어지게 된다. 이 논문에서는 기존 렌더링 결과에 볼륨 경계 평면을 추가로 렌더링하는 방법을 제안한다. 이 방법은 주파수가 높은 경계 부분의 샘플링 간격을 줄여 화질을 향상시킨다. 한편 MIP는 샘플링 순서에 무관하므로 추가된 슬라이스는 기존 렌더링 영상을 손실시키지 않는다. 증가된 슬라이스는 경계부분인 여섯 평면에 불과하므로 렌더링 수행시간에는 거의 영향을 주지 않고 화질을 개선할 수 있다.

• 한국정보과학회논문지:시스템및이론
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• 제32권9호
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• pp.457-464
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• 2005

본 논문에서는 임의의 좌표를 기준으로 17가지 접근방식을 지원하는 3차원 메모리 시스템을 제안한다. 제안하는 메모리 시스템은 메모리 모듈 할당 함수와 주소 할당 함수를 토대로 선 접근방식 13가지, 사각형 접근방식 3가지, 육면체 접근방식 1가지 등 모두 17가지 접근방식을 제공한다. 즉, 임의의 좌표에서 임의의 간격을 갖고 17가지 접근방식 중 어떠한 접근방식 내에서도 다수개의 데이타에 동시접근하는 기능을 제공한다. 이를 위해 제안하는 메모리 시스템은 메모리 모듈 선택 회로, 읽기/쓰기를 위한 데이타 라우팅 회로, 주소 계산 및 라우팅 회로들로 구성된다. 본 논문에서 제안하는 메모리 시스템은 응용 프로그램에 따라 쉽게 확장될 수 있으며, 메모리 시스템에 저장된 데이타를 개발자와 프로그래머가 논리적인 3차원 배열로 간주하여 처리할 수 있도록 데이타의 하드웨어 독립성을 지원한다 또한 제안한 메모리 시스템은 다양한 접근방식 내의 다수개의 데이타에 동시접근 할 수 있기 때문에 볼륨 렌더링이나 볼륨 클리핑 등과 같은 다양한 3차원 응용 분야 및 다중해상도를 지원하는 프레임 버퍼를 위한 시스템 구조의 메모리 시스템으로써 적합하다.

• Journal of Korean Neurosurgical Society
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• 제44권6호
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• pp.353-357
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• 2008

Objective : Many vascular neurosurgeons tend to remove bone flap in patients with large aneurysmal intracerebral hematomas (ICH). However, relatively little work has been done regarding the effectiveness of prophylactic decompressive craniectomy in a patient with a large aneurysmal ICH. Methods : Large ICH was defined as hematoma when its volume exceeded 25 mL, ipsilateral to aneurysms. The patients were divided into two groups; aneurysmal subarachnoid hemorrhage (SAH) associated with large ICH, January, 1994 - December, 1999 (Group A, 41 patients), aneurysmal SAH associated with large ICH, January, 2000 - May, 2005 (Group 8, 27 patients). Demographic and clinical variables including age, sex, hypertension, vasospasm, rebleeding, Hunt-Hess grade, aneurysm location, aneurysm size, and outcome were compared between two groups, and also compared between craniotomy and craniectomy patients in Group A. Results : In Group A. 21 of 41 patients underwent prophylactic decompressive craniectomy. In Group 8, only two patients underwent craniectomy. Surgical outcome in Group A (good 23, poor 18) was statistically not different from Group 8 (good 15, poor 12). Surgical outcomes between craniectomy (good 12, poor 9) and craniotomy cases (good 11, poor 9) in Group A were also comparable. Conclusion : We recommend that a craniotomy can be carried out safely without prophylactic craniectomy in patients with a large aneurysmal ICH if intracranial pressure is controllable with hematoma evacuation.

• Clinical Endoscopy
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• 제57권4호
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• pp.501-507
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• 2024

Background/Aims: Polyps greater than 30 mm are classified as "giants". Their endoscopic removal represents a technical challenge. The choice of the endoscopic removal technique is important because it provides a resection sample for precise histopathological staging. This is pivotal for diagnostic, prognostic, and management purposes. Methods: From a retrospective analysis, we obtained a sample of 38 giant polyps. Eighteen polypectomies were performed using the epinephrine volume reduction (EVR) method, nine polypectomies utilized endo-looping or clipping methods, and 11 patients underwent surgery. Results: We obtained en bloc resection with the EVR method in all cases; histology confirmed the correct indication for endoscopic resection in all cases. Moreover, no early or delayed complications were observed, and no patient required hospitalization. Using endo-looping or clipping methods, we observed advanced histology in 1/9 (11.1%) cases, while another patient (1/9, 11.1%) had delayed bleeding. Among patients who underwent surgery, 5/11 (45.5%) were deemed overtreated and three had post-surgical complications. Conclusions: We propose EVR as an alternative technique for giant polyp resection due to its safety, effectiveness, cost-efficiency, and the advantage of avoiding the need to postpone polypectomy to a later time. Further prospective studies might help improve this experience and enhance the technique.

• Journal of Korean Neurosurgical Society
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• 제30권sup1호
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• pp.91-98
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• 2001

Objective : The purpose of this study was to investigate the prognostic factors in patients who suffered an intracerebral hemorrhage(ICH) due to a ruptured middle cerebral artery(MCA) aneurysm. Methods : Among 148 case of ruptured MCA aneurysm, ruptured MCA aneurysm with ICH was compared with ruptured MCA aneurysm alone. According to factors, the prognosis in these two groups was analyzed. Prognosis was evaluated postoperatively by applying Glasgow Outcome Scale(GOS) at discharge. Prognostic factors were evaluated with Chi square test, Mann-Whitney test and ANOVA test with differences being considered significant for value less than 0.05. Results : Ruptured MCA aneurysm alone revealed better consciousness on admission and final outcome than those combined with ICH. Ruptured MCA aneurysm alone showed 74% in H-H grade I, II and 82% in GOS I, II. But ruptured MCA aneurysm with ICH showed 63% in H-H grade IV, V and 52% in GOS IV, V. Age, sex, lesion site, aneurysmal size, temoporary clipping time, interval to operation, operative approach were statistically not significant in prognosis(p>0.05). But H-H grade on admission(p<0.05), complication(esp. cerebral infarction)(p<0.05), preoperative ICH volume and site(p<0.01), preoperative midline shifting(p<0.01), remained ICH volume(p<0.05) showed significance statistically. Conclusion : Prognostic factors are helpful to neurosurgeon to estimate clinical and neurological outcome postoperatively. We suggest that the good prognostic factors in ruptured MCA aneurysm with ICH were good H-H grade on admission, cerebral infarction(-), preoperative ICH volume <25cc, temporal and intrasylvian ICH, preoperative midline shifting <5mm, remained ICH volume <10cc.

• Journal of Korean Neurosurgical Society
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• 제56권5호
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• pp.400-404
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• 2014

Objective : Clip artifacts limit the visualization of intracranial structures in CT scans from patients after aneurysmal clipping with cobalt alloy clips. This study is to analyze the parameters influencing the degree of clip artifacts. Methods : Postoperative CT scans of 60 patients with straight cobalt alloy-clipped aneurysms were analyzed for the maximal diameter of white artifacts and the angle and number of streak artifacts in axial images, and the maximal diameter of artifacts in three-dimensional (3-D) volume-rendered images. The correlation coefficient (CC) was determined between each clip artifact type and the clip blade length and clip orientation to the CT scan (angle a, lateral clip inclination in axial images; angle b, clip gradient to scan plane in lateral scout images). Results : Angle b correlated negatively with white artifacts (r=-0.589, p<0.001) and positively with the angle (r=0.636, p<0.001) and number (r=0.505, p<0.001) of streak artifacts. Artifacts in 3-D images correlated with clip blade length (r=0.454, p=0.004). Multiple linear regression analysis revealed that angle b was the major parameter influencing white artifacts and the angle and number of streak artifacts in axial images (p<0.001), whereas clip blade length was a major factor in 3-D images (p=0.034). Conclusion : Use of a clip orientation perpendicular to the scan gantry angle decreased the amount of white artifacts and allowed better visualization of the clip site.

• Journal of Korean Neurosurgical Society
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• 제51권5호
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• pp.268-271
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• 2012

Objective : To propose grading of intracerebral hemorrhage (ICH) in ruptured middle cerebral artery (MCA) aneurysms, which helps to predict the prognosis more accurately. Methods : From August 2005 to December 2010, 27 cases of emergent hematoma evacuation and aneurysm clipping for MCA aneurysms were done in the author's clinic. Three variables were considered in grading the ICH, which were 1) hematoma volume, 2) diffuse subarachnoid hemorrhage (SAH) that extends to the contralateral sylvian cistern, and 3) the presence of midline shifting from computed tomography findings. For hematoma volume of greater than 25 mL, we assigned 2 points whereas 1 point for less than 25 cc. We also assigned 1 point for the presence of diffuse SAH whereas 0 point for the absence of it. Then, 1 point was assigned for midline shifting of greater than 5 mm whereas 0 point for less than 5 mm. Results : According to the grading system, the numbers of patients from grade 1 to 4 were 4, 6, 8 and 9 respectively and 5, 7, 8, 4 and 3 patients belonged to Glasgow Outcome Scale (GOS) 5 to 1 respectively. It was found that the patients with higher GOS had lower ICH grade which were confirmed to be statistically significant (p<0.01). Preoperative Hunt and Hess grade and absence of midline shifting were the factors to predict favorable outcome. Conclusion : The ICH grading system composed of above three variables was helpful in predicting the patient's outcome more accurately.

• The Korean Journal of Physiology
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• 제28권2호
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• pp.225-231
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• 1994

The present study was undertaken to investigate the role of endogenous nitric oxide in renin release under different physiological conditions. In the first series of experiments, renin release was either inhibited by acute volume-expansion (VE) or stimulated by clipping one renal artery in the rat. VE was induced by intravenous infusion of saline (0.9% NaCl) up to 5% of the body weight over 45 min under thiopental (50 mg/kg, IP) anesthesia. VE caused a decrease of plasma renin concentration (PRC). With $N^G-nitro-L-arginine$ methyl ester $(L-NAME,\;5\;{\mu}g/kg\;per\;min)$ superadded to VE, PRC decreased further. The magnitude of increase in plasma atrial natriuretic peptide levels following VE was not affected by the L-NAME. In two-kidney, one clip rats, L-NAME-supplementation resulted in a decrease, and L-arginine-supplementation an increase of PRC. Plasma atrial natriuretic peptide levels were significantly lower in the L-arginine group than in the control. Blood pressure did not differ among the L-NAME, L-arginine, and control groups. In another series of experiments, the renin response to a blockade of NO synthesis was examined using in vitro preparations from isolated renal cortex. L-NAME significantly increased basal renin release, although it was without effect on the isoproterenol-stimulated release. These findings suggest that endogenous nitric oxide significantly contributes to the renin release. Since many factors may affect the renin release in vivo, an interaction between NO and renin under various pathophysiological states is to be further defined.

• 한국지리정보학회지
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• 제13권2호
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• pp.54-63
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• 2010

2009년 7월 9일부터 14일까지 누적강우 455mm의 집중호우에 의해 제천시 일대에 다수의 토석류 사태가 발생하였다. 토석류 발생에 따른 지형변화를 분석하기 위하여 수치지도와 라이다(LiDAR) 자료를 이용하여 고해상도의 수치고도모델(DEM)을 생성하였다. 라이다측량을 위해서 고해상도의 디지털 카메라와 GPS가 탑재된 3차원 스캐너 시스템 (RIEGLE LMS-Z390i)을 이용하였다. 라이다 스캐닝에 의해 생성된 포인트 자료는 클리핑과 필터링 작업을 거친 후 수치지도에 중첩시켜 토석류 발생 후의 지형의 DEM을 생성한다. 이렇게 토석류 발생 전후의 DEM 비교결과, 토석류 발생에 의한 침식과 퇴적량은 각각 $17,586m^3$, $7,520m^3$으로 평가되었다. 이러한 고해상도 지상라이다시스템을 이용하여 지형변화 관측을 통해 장래 토석류 모델 연구에 기여할 수 있을 것으로 판단되었다.

• Journal of Korean Neurosurgical Society
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• 제39권5호
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• pp.335-339
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• 2006

Objective : The authors present eight cases of immediate post-operative epidural hematomas[EDHs] adjacent to the craniotomy site, describe clinical details of them, and discuss their pathogenesis. Methods : Medical records of eight cases were retrospectively reviewed and their clinical data, operation records, and radiological findings analyzed. Any risk factors of the EDHs were searched. Results : In 5 of 8 cases, adjacent EDHs developed after craniotomies for the surgical removal of brain tumors. Three cases of adjacent EDHs developed after a pterional approach and neck clipping of a ruptured anterior communicating artery aneurysm, a ventriculoperitoneal shunt, and a craniotomy for a post-traumatic EDH, respectively. In all eight cases, brain computed tomography[CT] scans checked immediately or a few hours after the surgery, revealed large EDHs adjacent to the previous craniotomy site, but there was no EDH beneath the previous craniotomy flap. After emergent surgical removal of the EDHs, 7 cases demonstrated good clinical outcomes, with one case yielding a poor result. Conclusion : Rapid drainage of a large volume of cerebrospinal fluid or intra-operative severe brain collapse may separate the dura from the calvarium and cause postoperative EDH adjacent to the previous craniotomy site. A high-pressure suction drain left in the epidural space may contribute to the pathogenesis. After the craniotomy for brain tumors or intracranial aneurysms, when remarkable brain collapse occurs, an immediate postoperative brain CT is mandatory to detect and adequately manage such unexpected events as adjacent EDHs.