• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.717-720
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• 2002

The present study is to evaluate the performances of flow velocity and wall shear stress in the stenosed coronary artery using human in vivo hemodynamic Parameters and computer simulation. Initial and follow-up coronary angiographics in the patients with angulated coronary stenosis are performed. Follow-up coronary angiogram demonstrated significant difference in the percent of diameter in the stenosed coronary between two groups ($Group\;1:\;40.3{\%},\;Group\;2:\;25.5{\%}$). Flow-velocity wave obtained from in vivo intracoronary Doppler ultrasound data is used for the boundary condition for the computer simulation. Spatial and temporal variations of flow velocity vector and recirculation area are drawn throughout the selected segment of coronary models. The WSS of pre- and post-intracoronary stenting are calculated from three-dimensional computer simulation. Then negative shear stresses area on 3D simulation we noted on the inner wall of the post-stenotic area before stenting. The negative WSS is disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2. The present study suggest that hemodynamic forces exerted by pulsatile coronary circulation termed WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. The local recirculation area which has low or negative WSS, might lead to progression of atherosclerosis.

• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1181-1188
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• 2004

This paper reviews the main aspects of cardiovascular system dynamics with emphasis on modeling hemodynamic characteristics using a lumped parameter approach. Methodological and physiological aspects of the circulation dynamics are summarized with the help of existing mathematical models: The main characteristics of the hemodynamic elements, such as the heart and arterial and venous systems, are first described. Lumped models of micro-circulation and pulmonary circulation are introduced. We also discuss the feedback control of cardiovascular system. The control pathways that participate in feedback mechanisms (baroreceptors and cardiopulmonary receptors) are described to explain the interaction between hemodynamics and autonomic nerve control in the circulation. Based on a set-point model, the computational aspects of reflex control are explained. In final chapter we present the present research trend in this field and discuss the future studies of cardiovascular system modeling.

• Journal of Acupuncture Research
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• 제21권5호
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• pp.241-248
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• 2004

Objectives : The purpose of this study is to examine the hemodynamic characteristics of pulse point. Methods : The computational analysis algorithms of arterial tree system was derived. In order to investigate the effect of internal organ on the pulse point, the diameter of celiac artery was reduced by half. Results : The sensitivity of flow change at the Inyoung(Renying) is better than that of the Chongu(Cunkou). but the Inyoung was worse than the Chongu in the point of the left and right symmetry. The pressure changes at the Inyoung and the Chongu were in the similar range. Conclusions : It was found from the result that the Chongu shows the more symmetrical hemodynamic characteristics than the Inyoung.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.529-532
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• 2001

The purposes of the present study are to investigate hemodynamic characteristics and to define shear-sensitive remodeling in the stenosed coronary models. Two models for the compensatory remodelling used for this research are a pre-stenotic dilation and a post-stenotic dilation models for the computer simulation. The peak wall shear stress on the post-stenotic model is higher than that of the pre-stenotic model. Two recirculation zones are generated in the pre-stenotic model, and the zones in the pre-stenotic model are smaller than those in the post-stenotic model. Variation of the wall shear stress in the pre-stenotic model is lower than that in the post-stenotic model. In computer simulation with the post-stenotic model, higher temporal and spatial shear fluctuation and stress suggested shear-sensitive remodeling. Shear-sensitive remodeling may be associated with the increased risk of plaque rupture, the underlying cause of acute coronary syndromes, and sudden cardiac death.

• 대한기계학회논문집B
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• 제34권10호
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• pp.893-899
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• 2010

박동유동조건에서 관상동맥 내의 유동특성과 혈류역학적 인자 분포를 선행연구에서 수행하여 혈류역학이 관상동맥 내의 협착현상과 연관관계가 있음을 밝혔다. 동맥경화증의 호발부위인 관상동맥 분지부에서 혈류역학적 변수를 분석하여 동맥경화증의 발생기전을 규명하는 것이 본 연구의 목적이다. 동맥경화증에 의한 협착현상은 혈액과 혈관벽 사이의 생화학 반응뿐 아니라 유동박리나 벽전단응력과 같은 혈류역학적 인자와도 관계 있음을 확인하였다. 관상동맥 분지부의 분지각이 증가할수록 분지부 단면에서의 재순환영역의 크기가 증가하고 교란유동이 발생하게 된다. 이 재순환영역이 관상동맥에서 동맥경화의 시작점으로 의심되는 영역이라 할 수 있다.

• 한국전산유체공학회지
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• 제16권4호
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• pp.64-71
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• 2011

Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured, a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.161-168
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• 2011

Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.

• 대한의용생체공학회:의공학회지
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• 제22권6호
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• pp.535-542
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• 2001

스텐트를 이용한 동맥류 색전술은 방추형 동맥류 등 목이 넓은 광경동맥류의 치료에 최근 사용되고 있다. 동맥류 내부의 혈류유동은 혈전의 형성 및 동맥류 폐색에 중요한 역할을 하므로 스텐트의 삽입으로 인한 동맥류 내부 혈류 유동의 변화를 고찰하기 위하여 광색성 염료를 이용한 유동가시화 방법을 사용하였다. 제작된 방추형 동맥류 모델에 대해 맥동 유동시 동맥류 벽 다섯 위치에서 유동장의 정성적 관탈 및 벽 전단변형률의 측정이 수행되었다. 스텐트의 삽입은 동맥류 내부의 유동을 감소시켰으며 동맥류 내부의 느린 와류유동이 감속후기가지 지속되었다. 또한 스텐트가 삽입된 모델은 스텐트가 없는 모델에 비하여 벽 전단변형률이 감소하였으며. OSI는 증가하였다 이러한 혈류유동의 변화는 혈전의 형성 및 내막거식증대가 일어나기 쉬운 혈류역학적 환경을 제공한다. 따라서 스텐트의 삽입으로 인한 동맥류 내부의 혈류 유동은 혈전의 형성 및 동맥류 폐색을 촉진하도록 변화함을 알 수 있었다..

• Journal of Korean Neurosurgical Society
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• 제60권5호
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• pp.504-510
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• 2017

Objective : To investigate the morphological and hemodynamic parameters associated with middle cerebral artery (MCA) bifurcation aneurysm rupture. Methods : A retrospective study of 67 consecutive patients was carried out based on 3D digital subtraction angiography data. Morphological and hemodynamic parameters including aneurysm size parameters (dome width, height, and perpendicular height), longest dimension from the aneurysm neck to the dome tip, neck width, aneurysm area, aspect ratio, Longest dimension from the aneurysm neck to the dome tip (Dmax) to dome width, and height-width, Bottleneck factor, as well as wall shear stress (WSS), low WSS area (LSA), percentage of LSA (LSA%) and energy loss (EL) were estimated. Parameters between ruptured and un-ruptured groups were analyzed. Receiver operating characteristics were generated to check prediction performance of all significant variables. Results : Sixty-seven patients with MCA bifurcation aneurysm were included (31 unruptured, 36 ruptured). Dmax (p=0.008) was greater in ruptured group than that in un-ruptured group. D/W (p<0.001) and the percentage of the low WSS area ($0.09{\pm}0.13$ vs. $0.01{\pm}0.03$, p<0.001) were also greater in the ruptured group. Moreover, the EL in ruptured group was higher than that in unruptured group ($6.39{\pm}5.04$ vs. $1.53{\pm}0.86$, p<0.001). Multivariate regression analysis suggested D/W and EL were significant predictors of rupture of MCA bifurcation aneurysms. Correlation analyses revealed the D/W value was positively associated with the EL (R=0.442, p<0.01). Conclusion : D/W and EL might be the most two favorable factors to predict rupture risk of MCA bifurcation aneurysms.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2941-2946
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• 2007

A model of the cardiovascular system coupling cell, hemodynamics and autonomic nervecontrol function is proposed for analyzing heart mechanics. We developed a comprehensive cardiovascular model with multi-physics and multi-scale characteristics that simulates the physiological events from membrane excitation of a cardiac cell to contraction of the human heart and systemic blood circulation and ultimately to autonomic nerve control. Using this model, we delineatedthe cellular mechanism of heart contractility mediated by nerve control function. To verify the integrated method, we simulated a 10% hemorrhage, which involves cardiac cell mechanics, circulatory hemodynamics, and nerve control function. The computed and experimental results were compared. Using this methodology, the state of cardiac contractility, influenced by diverse properties such as the afterload and nerve control systems, is easily assessed in an integrated manner.