Centre for Cardiovascular Science, University of Edinburgh, UK.
Int J Numer Method Biomed Eng. 2013 Feb;29(2):165-78. doi: 10.1002/cnm.2535. Epub 2012 Dec 6.
Three inlet boundary condition datasets were derived from phase-contrast MRI: (i) centre line velocity data converted to two-dimensional (2D) velocity profile using Womersley equations (Womersley), (ii) 2D velocity profile with one axial component of velocity (1CV), (iii) 2D velocity profile with three components of velocity (3CV). Computational fluid dynamics was performed using a rigid wall approach with geometry data extracted from the computed tomography dataset. Helical flow was present in the 1CV and 3CV simulations, with more complex patterns for the 3CV case. The Womersley method produced simplified flow patterns with an absence of helical flow. Mean values of quantitative indices (helical flow index, mean wall shear stress, oscillatory index) were compared with the 3CV inlet data. These were lower for both the Womersley inlet data (28%, 71%, 56%) and the 1CV inlet data (9%, 24%, 69%). It was concluded that inlet methods based on centre line velocity, such as might be obtained from Doppler ultrasound, lead to significantly simplified abdominal aortic aneurysm haemodynamics and thus are not recommended. Single velocity component (axial) data from MRI might suffice when general flow characteristics and spatial wall shear stress are required. Ideally 2D MRI velocity profiles with 3-velocity component data are preferred to fully account for helical flow.
从相位对比 MRI 中得到了三个入口边界条件数据集：（i）使用沃默斯利方程（Womersley）将中心线速度数据转换为二维（2D）速度分布的中心线速度数据，（ii）具有一个速度轴向分量的 2D 速度分布（1CV），（iii）具有三个速度分量的 2D 速度分布（3CV）。使用从计算机断层摄影数据集提取的几何数据，通过刚性壁方法进行计算流体动力学。1CV 和 3CV 模拟中存在螺旋流，而 3CV 情况下的流型更复杂。沃默斯利方法产生了简化的流型，没有螺旋流。将定量指标（螺旋流指数、壁面剪切应力平均值、脉动指数）的平均值与 3CV 入口数据进行比较。沃默斯利入口数据（28%、71%、56%）和 1CV 入口数据（9%、24%、69%）的这些值都较低。结论是，基于中心线速度的入口方法，例如可能从多普勒超声获得的方法，导致腹主动脉瘤血液动力学显著简化，因此不建议使用。当需要一般的流动特征和空间壁面剪切应力时，MRI 的单速度分量（轴向）数据可能就足够了。理想情况下，应使用具有 3 个速度分量数据的 2D MRI 速度分布来充分考虑螺旋流。
