Comparison of Efficiency in Dose Planning of the Leksell Gamma Knife Perfexion and Model C : Clinical Study

Objective：The purpose of this study was to compare the dose planning between the Leksell Gamma Knife Perfexion (LGK PFX) and the Leksell Gamma Knife C (LGK C) using variable indices. Methods：A total of 100 cases, which were composed of 35 meningiomas, 20 vestibular schwannomas, 35 metastases, and 10 pituitary adenomas, were enrolled in this study. First, these cases were treated with the LGK PFX and then, were re-planned with the LGK C. We compared these two models in terms of the number of shots, the percentage of coverage, the conformity index (CI), Paddick’s conformity index (PCI), the gradient index (GI), and the beam on time. Results：The LGK PFX completely outperformed the LGK C in terms of GI and the LGK PFX tended to have a longer beam on time than that of the LGK C. However, in patients with schwannomas, the LGK PFX outperformed the LGK C in terms of the CI, PCI, and GI, and in patients with pituitary adenomas, the LGK PFX outperformed the LGK C in terms of the percentage of coverage, PCI, and GI with statistical significance. Conclusion：The LGK PFX is an entirely redesigned radiosurgery unit accompanied by the development of software. The LGK PFX is supposed to achieve highly conformal dose prescription consisting of many isocenters with a reasonable treatment time.ope

뇌동맥류 결찰 후 초기 혈관조영술의 임상적 의미와 잔여 뇌동 맥류에 대한 예측인자

의학과Aneurysm remnants after microsurgical clipping have a risk of regrowth and rupture and have not been validated in the era of 3-dimensional angiography. Although computed tomography angiography (CTA) is currently preferred for evaluating aneurysmal clipping results, it cannot completely rule out postoperative remnant occurrence. Furthermore, there is no concrete evidence supporting its superior accuracy to digital subtraction angiography (DSA). Therefore, this study aimed to (1) evaluate the clinical value of angiography in diagnosing remnants, (2) determine the rate of remnants, and (3) identify the predictors for remnants after microsurgical clipping. Between January 2014 and May 2017, 200 aneurysms in 154 patients, treated via microsurgical clipping, were considered eligible for the present study. Among them, 139 aneurysms in 106 patients were finally selected for evaluation. The results of microsurgical clipping were evaluated within 7 days to predict the remnant development risk using DSA based on the classification, and clinical features of the patients and characteristics of treated aneurysms. The rate of aneurysm remnants, including intentional remnants, was 29.5%, and retreatments were needed in 6.5% of such cases. Neck size (cut-off: 5.68 mm; sensitivity, 66.7%; specificity, 96.2%) and maximum diameter (cut-off: 7.03 mm; sensitivity, 66.7%; specificity, 89.2%) of aneurysms were independent predisposing factors for the occurrence of aneurysm remnants that need retreatment (OR: 2.30; p < 0.001; OR: 1.38; p < 0.001, respectively). Postoperative DSA may identify remnants after microsurgical clipping. Aneurysms with larger neck size and maximum diameter have a higher risk of aneurysmal remnants after clipping. 뇌동맥류 결찰 후 발생하는 잔여 뇌동맥류는 재성장과 파열의 위험성이 있으나, 이에 대한 3차원 뇌혈관조영술을 이용한 검증은 제대로 이루어지지 않았다. 본 연구에서는 3차원 뇌혈관조영술을 이용하여 결찰 후 발생하는 잔여 뇌동맥류의 위험인자를 분석하여 뇌혈관조영술의 임상적 의미에 대해 고찰해보고자 한다. 뇌동맥류 결찰을 시행한 후 2주 이내 뇌혈관조영술을 시행한 환자들을 대상으로 하였으며, 환자들의 특성 및 치료한 뇌동맥류의 특성 그리고 수술 후 시행한 3차원 뇌혈관조영술을 토대로한 잔여 뇌동맥류를 분석하였다. 총 106명 환자의 139개의 뇌동맥류를 대상으로 분석하였고, 41개의 뇌동맥류가 잔여 뇌동맥류로 확인되었다. (29.5%) 통계적인 분석을 통해 뇌동맥류의 목 길이 (승산비 2.30)와 최대 직경(승산비 1.38)이 뇌동맥류 결찰 후 치료가 필요한 뇌동맥류 발생의 독립적인 예측인자임을 확인하였다. 본 연구를 통해 뇌동맥류 결찰 후 초기 시행한 혈관조영술이 잔여 뇌동맥류를 진단하는데 유용함을 확인하였으며, 수술 전 뇌동맥류의 목 길이와 최대 직경이 재치료가 필요한 잔여 뇌동맥류 발생의 예측인자임을 알 수 있다.open석

철골 대각선 가새골조의 지진하중하의 동적불안정

학위논문(석사)--서울대학교 대학원 :건축학과,2005.Maste

Prediction of rupture risk in cerebral aneurysms by comparing clinical cases with fluid-structure interaction analyses

Cerebral aneurysms should be treated on the basis of accurate rupture risk prediction. Nowadays, the rupture risk in aneurysms has been estimated using hemodynamic parameters. In this paper, we suggest a new way to predict the rupture risks in cerebral aneurysms by using fluid-structure interaction (FSI) analysis for better decision-making regarding treatment. A patient-specific model was constructed using digital subtraction angiography of 51 cerebral aneurysms. For each model, a thin-walled area (TWA) was first predicted using computational fluid dynamics (CFD), and then the highest equivalent strain in the TWA was calculated with FSI by varying wall thicknesses and mechanical properties. A critical curve was made from 16 FSI results for each patient-specific model to estimate the rupture risk. On average, the equivalent strains of the ruptured aneurysms were higher than those of the unruptured aneurysms. Furthermore, the patterns of critical curves between unruptured and ruptured aneurysms were clearly distinguishable. From the rupture risk evaluation based on the cut-off value, 24 of the 27 unruptured aneurysms and 15 of the 24 ruptured aneurysms were matched with actual-clinical setting cases. The critical curve proposed in the present study could be an effective tool for the prediction of the rupture risk of aneurysm

Rete middle cerebral artery anomalies: a unifying name, case series, and literature review

OBJECTIVE Rete middle cerebral artery (MCA) is extremely rare and has not been frequently discussed. Rete MCA is a weblike anomaly of the MCA that does not coalesce and forms a prominent, large single branch from the plexiform vessels in the fetal stage. The purpose of this study was to further elucidate the clinical and radiological characteristics of patients with rete MCA. METHODS A total of 2262 cerebral digital subtraction angiography procedures were performed on 1937 patients at the authors&amp;amp;apos; institution from February 2013 to May 2017. Data analysis included age, sex, clinical symptoms, underlying diseases, coexisting cerebral arterial anomalies, and operative methods and findings. RESULTS Rete MCAs were found in 13 patients, and the incidence of this anomaly was 0.67% (13 of 1937) in this study. Of the 13 patients, 3 had hemorrhagic strokes, 6 had ischemic strokes, and 4 had no symptoms. Eight patients underwent conservative treatment, and 5 patients underwent surgical treatment. Rete MCA is considered a congenital disease of the cerebral vasculature with the possibility of an acquired abnormality, such as an aneurysm, caused by hemodynamic stress. Although an epidemiological survey of rete MCA was not conducted, it is assumed that rete MCA has a high prevalence in Asia. Ischemic and hemorrhagic stroke events are fairly common in rete MCA. CONCLUSIONS Clinicians should understand the radiological and clinical features of patients with rete MCA to avoid misdiagnosis and unnecessary treatment. This anomaly should be differentiated from other vascular diseases and patients presenting incidentally should be carefully monitored because of their vulnerability to both hemorrhagic and ischemic strokes

Evaluation of the angiographic outcomes after clipping of intracranial aneurysms: determination of predisposing factors for occurrence of aneurysm remnants

Objectives: Aneurysm remnants after microsurgical clipping have a risk of regrowth and rupture and have not been validated in the era of three-dimensional angiography. Therefore, this study aimed to evaluate the angiographic outcome using three-dimensional rotational images and determine the predictors for remnants after microsurgical clipping. Methods: Between January 2014 and May 2017, 139 aneurysms in 106 patients who were treated with microsurgical clipping, were eligible for this study. For the determination of aneurysm remnants after microsurgical clipping, the angiographic outcomes were evaluated using follow-up digital subtraction angiography within 7 days for unruptured aneurysms or within 2 weeks for ruptured aneurysms. According to the Sindou classification, the aneurysm remnants were dichotomized, and subgroup analysis was performed to identify the predictors of aneurysm remnants after clipping with various imaging parameters and clinical information. Results: The overall rate of aneurysm remnants was 29.5% (41/139), in which retreatments were needed in 6.5% (9/139). The neck size and maximum diameter of aneurysms were independent predisposing factors for the aneurysm remnants that need retreatment (OR: 2.30; p &amp;amp;lt; 0.001; OR: 1.38; p &amp;amp;lt; 0.001, respectively). Conclusions: This study demonstrated a low incidence of aneurysm remnants after microsurgical clipping which need to retreatment. However, selective postoperative angiography could provide us clear information of surgical result and evidence for long-term follow-up for some aneurysms with larger neck size (&amp;amp;gt;5.7 mm) and maximum diameter (&amp;amp;gt;7.1 mm). © 2020, © 2020 Informa UK Limited, trading as Taylor &amp;amp;amp; Francis Group

갈대의 군집 특성에 관한 풍동실험 연구

2

Experimental study on tandem arrangement of multiple flexible cylinders

1

T형 할바흐 자석배열을 이용한 6 자유도 자기부상 평면모터의 설계 및 제어

학위논문(박사) - 한국과학기술원 : 기계공학전공, 2010.2, [ xi, 94 p. ]The smaller, the faster, the cheaper. These are the fundamental goals of the next-generation semiconductor industry. Magnetically levitated planar motors are the only solution to meet these requirements. It can move in six-degrees-of freedom over long range with nano positioning accuracy in vacuum environment. To achieve these goals, we propose, design and control a new type of magnetically levitated planar motor. The proposed planar motor consists of moving magnet array(mover) and multiple coil arrays(stator). The key feature of the the planar motor is to use newly developed T-shape Halbach magnet array. The T-shape Halbach magnet array has several advantages such as higher force, lower force ripple and cost effectiveness compared with previously developed planar motors. These characteristics are very important features to meet the fundamental goals for the next-generation lighography system. High force capability enables fast movement with high control bandwidth, and therefore improves positionig accuracy and product throughput. Low force ripple reduces disturbances, and therefore improves sanning performance. Cost effectiveness, caused by easy-assembly, enables modular manufacturing process of the planar motor. These key featues enable applying the proposed planar motor to the wafer stage of the next-generation lithography system. We present design optimization frameworks in order to maximze force density and minimize force ripple. At first, analytic modeling method based on the Maxwell equation is presented in order to calculate magnetic flux distribution and generated forces. This method predicts six degrees-of-freedom motion of the planar motor at arbitrary position. Secondly, parametric analysis is performed in order to investigate the effect of the design variables on the performances. We can know the correlations between design variables and the performance of the planar motor. Finally, we perform design optimization process in order to find optima...한국과학기술원 : 기계공학전공