Errors in the estimation of wall shear stress by maximum Doppler velocity.
Errors in the estimation of wall shear stress by maximum Doppler velocity.
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DOI：
10.1016/j.atherosclerosis.2013.01.026
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发表时间：
2013-04
期刊：
影响因子：
5.3
通讯作者：
Steinman, David A.
中科院分区：
文献类型：
--
作者：
Mynard, Jonathan P.;Wasserman, Bruce A.;Steinman, David A.
关键词：
室壁切应力(WSS)是与血管功能密切相关的重要参数。WSS很难直接测量，通常通过假设完全发展的流动从最大频谱多普勒速度(Vmax)推断出来，这只有在血管又长又直的情况下才有效。有证据表明，即使是名义上笔直的颈总动脉(CCA)中的轻微/局部曲率也会阻止血流的充分发育，出于这一证据，我们研究了速度曲线偏斜对Vmax派生的WSS的影响。作为验证研究的一部分，从基于图像的计算流体动力学(CFD)模拟的CCA中提取了代表不同偏斜程度的速度分布。根据理想化的样本体积计算最大速度，并通过完全开发的(泊松或沃默斯利)速度剖面来估计WSS，以与实际(即CFD得出的)WSS进行比较。对于周期平均的WSS，假设Poiseuille或Wemersley剖面，轻微的速度剖面偏斜导致±25%的误差，而严重的速度剖面偏斜导致的中位数误差为30%(最大55%)。不管Poiseuille偏斜与否，收缩期峰值WSS被低估了约50%；使用Wemersley曲线消除了这一偏差，但仍有±30%的误差。在收缩末期误差最大，此时倾斜最明显。偏斜还引入了较大的周向WSS变化：周向平均值的±60%，最高可达±100%。VMAX导出的WSS可能容易产生与速度轮廓偏斜有关的重大变量误差，并且无法检测到可能的较大的周向WSS变化。在对速度剖面形状进行假设以计算WSS时应谨慎行事，即使在通常被认为又长又直的船舶上也是如此。
Wall shear stress (WSS) is an important parameter with links to vascular (dys)function. Difficult to measure directly, WSS is often inferred from maximum spectral Doppler velocity (Vmax) by assuming fully-developed flow, which is valid only if the vessel is long and straight. Motivated by evidence that even slight/local curvatures in the nominally straight common carotid artery (CCA) prevent flow from fully developing, we investigated the effects of velocity profile skewing on Vmax-derived WSS. Velocity profiles, representing different degrees of skewing, were extracted from the CCA of image-based computational fluid dynamics (CFD) simulations carried out as part of the VALIDATE study. Maximum velocities were calculated from idealized sample volumes and used to estimate WSS via fully-developed (Poiseuille or Womersley) velocity profiles, for comparison with the actual (i.e. CFD-derived) WSS. For cycle-averaged WSS, mild velocity profile skewing caused ±25% errors by assuming Poiseuille or Womersley profiles, while severe skewing caused a median error of 30% (maximum 55%). Peak systolic WSS was underestimated by ~50% irrespective of skewing with Poiseuille; using a Womersley profile removed this bias, but ±30% errors remained. Errors were greatest in late systole, when skewing was most pronounced. Skewing also introduced large circumferential WSS variations: ±60%, and up to ±100%, of the circumferentially averaged value. Vmax-derived WSS may be prone to substantial variable errors related to velocity profile skewing, and cannot detect possibly large circumferential WSS variations. Caution should be exercised when making assumptions about velocity profile shape to calculate WSS, even in vessels usually considered long and straight.
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