台灣留學生出席國際會議補助

2009年12月30日星期三

Vascular Fluid-Structure Interaction: Methodology and Application to Cerebral Aneurysms

論文發表人: 徐銘辰 (加州大學聖地牙哥分校結構力學所博士班)

http://usnccm-10.eng.ohio-state.edu/

近年來隨著影像擷取、模型製作、網格產生、計算方法以及視覺化技術的進步,針對特定病患之血流計算模擬也步入成熟階段。當今學界最先進之血管流計算研究為利用對大範圍人體心血管系統之流固耦合模擬,探索心血管疾病肇因進程與血液動力學之聯繫,預測外力介入之結果,並評估電子輔助醫療器具之影響。以上例子包含腹部及腦部之腫瘤模擬,及血管內硬化斑塊之形成與破裂。

本論文針對特定病患中大腦動脈分枝腫瘤進行計算模擬探討。我們提出一流體與固體結構完全耦合之模擬方法,並呈現支持此分析之網格生成技術。此流固耦合計算架構可預測實驗所無法獲得之血液動力數據並進行評估。我們並將其與純流體計算結果做比較,以分析於心血管計算模擬中考慮管壁彈性之重要性。

結果顯示血液與血管壁之交互作用改變了血液動力對管壁之施力。當心臟收縮血液流進腫瘤並衝撞管壁時,考慮管壁彈性將降低腫瘤內壁面剪應力並改變其分布。此結果彰顯了於針對病患之腦腫瘤計算模擬中,流固耦合之重要性。
In recent years patient-specific modeling of blood flow has matured immensely with the emergence of better imaging, modeling, mesh generation, computation and visualization technologies.
State-of-the-art vascular modelings involve fully coupled fluid-structure simulations of large portions of the human cardiovascular system, in an effort to investigate hemodynamic factors influencing the onset and progression of cardiovascular disease, to predict an outcome of an intervention, or to evaluate the effects of electromechanical assist devices. Examples of the first include
abdominal and cerebral aneurysms and formation and rupture of vulnerable plaque.

This work focuses on computation of several patient-specific aneurysm models at the middle cerebral artery (MCA) bifurcation. A fully coupled simulation approach is reviewed and main aspects of mesh generation in support of the fluid-structure analysis are presented.  Quantities of hemodynamic interest, that are unattainable in  experiments, are studied to assess the relevance of fluid-structure  interaction (FSI) modeling as compared to rigid-arterial-wall simulations.

The results show that the interaction between the blood flow and wall deformation changes the hemodynamic forces acting on the arterial wall. When the blood flows straight into the aneurysm and impinges the wall during the systole, the maximum wall shear stress (WSS) at the dome decreases while the effect of the flexible wall is incorporated in the computation. The resulting WSS patterns are altered both qualitatively and quantitatively. Rigid versus flexible wall simulation results reinforce the importance of FSI in the patient-specific modeling of cerebral aneurysms.