Augst A D, Barratt D C, Hughes A D, Thom S A McG, Xu X Y
Department of Chemical Engineering and Chemical Technology, Imperial College London, London, UK.
Proc Inst Mech Eng H. 2003;217(5):393-403. doi: 10.1243/095441103770802568.
Computational fluid dynamics (CFD) flow simulation techniques have the potential to enhance understanding of how haemodynamic factors are involved in atherosclerosis. Recently, three-dimensional ultrasound has emerged as an alternative to other three-dimensional imaging techniques, such as magnetic resonance angiography (MRA). The method can be used to generate accurate vascular geometry suitable for CFD simulations and can be coupled with Doppler ultrasound to provide physiologically realistic flow boundary conditions. However, there are various ways to utilize the flow data acquired, possibly leading to different results regarding both flow and wall shear stress patterns. A disadvantage of three-dimensional ultrasound for imaging the carotid bifurcation has been established as being the scanning limitation of the jawbone position. This may make artificial extensions of the internal and/or external carotid arteries necessary, which in turn may influence the predicted flow patterns. Flow simulations were carried out for three outflow calculation schemes as well as four geometries with different extensions to the carotid daughter vessels. It was found that variation of flow patterns was more strongly influenced by the outflow conditions than by the extensions of the daughter vessels. Consequently, it is recommended that for future CFD simulations of carotid flow using three-dimensional ultrasound data, the outflow boundary conditions should rely on the most accurate measurement available, and flow data recorded in the common and internal carotid are considered more reliable than data from the external carotid. Even though the extended lengths of the daughter vessels have insignificant effects on the predicted haemodynamic parameters, it would be a safer option to extend the internal carotid by approximately three times the diameter of the common carotid artery.
计算流体动力学（CFD）流动模拟技术有潜力加深对血流动力学因素如何参与动脉粥样硬化的理解。最近，三维超声已成为磁共振血管造影（MRA）等其他三维成像技术的替代方法。该方法可用于生成适合CFD模拟的精确血管几何形状，并可与多普勒超声结合以提供生理上逼真的流动边界条件。然而，有多种利用所获取流动数据的方法，这可能导致在流动和壁面剪应力模式方面产生不同结果。三维超声用于颈动脉分叉成像的一个缺点已被确认为是颌骨位置的扫描限制。这可能使得有必要对颈内动脉和/或颈外动脉进行人工延伸，进而可能影响预测的流动模式。针对三种流出计算方案以及四种对颈动脉分支血管有不同延伸的几何形状进行了流动模拟。结果发现，流动模式的变化受流出条件的影响比受分支血管延伸的影响更大。因此，建议在未来使用三维超声数据进行颈动脉血流的CFD模拟时，流出边界条件应依赖于可获得的最准确测量，并且颈总动脉和颈内动脉中记录的流动数据比颈外动脉的数据更可靠。尽管分支血管的延伸长度对预测的血流动力学参数影响不大，但将颈内动脉延伸约颈总动脉直径的三倍是更安全的选择。
