主動脈剝離(Aortic dissection)和動脈粥樣硬化(atherosclerosis)為常見高致死率的心臟疾病，形成這些病變的關鍵因素係因主動脈內複雜的血流動力因素(hemodynamics)對血管壁面所產生的壓力與異常剪應力所引起的，所以了解心血管的循環系統內流場的分布情形為重要的課題。本研究藉由核磁共振影像(Phase-Contrast Magnetic Resonance Imaging, PC-MRI)，獲得一般正常人的主動脈弓外型，並利用數篇相關的文獻作為計算的邊界條件，再利用計算流體力學軟體ACE+®基於三維、暫態、不可壓縮牛頓流體以及流固耦合模型進行理論分析。再將求解所得的血流動力因素如壁面剪應力(Wall Shear stress, WSS)、壓力、血流脈波傳導速度(Pulse Wave Velocity, PWV)以及壁面剪應力震盪值(Oscillatory WSS Index, OSI)與上述主動脈的疾病做討論，並且與尚未加入流固耦合模型的結果做比較。預測的結果顯示主動脈剝離以及動脈粥樣硬化的發展成因與壁面剪應力的最大值和最小值的位置有關聯。除此之外，亦發現考慮流固耦合之後的結果使得壁面剪應力比尚未加入流固耦合模型的結果在幾個特殊的時間點下有明顯下降的趨勢。最後我們將用在PC-MRI計算血流脈波傳導速度的技術應用在CFD的結果上，此為一新的應用方法，並可以間接證明本研究模型的壁面順應性與真實人體相符。

Aortic dissection and atherosclerosis are highly fatal diseases. Complicated hemodynamics is closely related to the development of aortic dissection and atherosclerosis; therefore, it is important to better understand the flowfield in the cardiovascular circulatory system of a human body. In this research, the test model was imitated from the true geometry of a normal human thoracic aorta scanned by the phase-contrast magnetic resonance imaging (PC-MRI) technique. The interaction of blood flow with vessel wall dynamics in a thoracic aorta model was studied using a coupled fluid-structure analysis built in the computational fluid dynamic (CFD) code ACE+® to determine flow characteristics of the three-dimensional, pulsatile, incompressible and Newtonian fluid in the thoracic aorta. The distributions of wall shear stress (WSS) and oscillatory WSS index (OSI) were resolved to examine their connections to the aortic disorders. The predictions indicate the preferential development of the early aortic dissection and atherosclerosis in the areas of either maxima or minima of WSS, which may properly lead to a useful biological significance. In consistency with similar findings reported in previous studies, the numerical results suggest that simulations which consider the fluid structure interaction (FSI) effect can predict relatively lower WSSs linking with deformation of the vessel wall in some particular times during a cardiac cycle. Instead of implementing a typical PC-MRI technique to measure the aortic pulse wave velocity (PWV), we also presented an innovative application of using the FSI approach to resolve the PWV for assessment of wall compliance in a thoracic aorta model.

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