Hemodynamics of human carotid artery bifurcations: Computational studies with models reconstructed from magnetic resonance imaging of normal subjects
Hemodynamics of human carotid artery bifurcations: Computational studies with models reconstructed from magnetic resonance imaging of normal subjects
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DOI：
10.1016/s0741-5214(98)70210-1
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发表时间：
1998-07-01
影响因子：
4.3
通讯作者：
Steinman, DA
中科院分区：
文献类型：
--
作者：
Milner, JS;Moore, JA;Steinman, DA
目的：血流动力学，特别是壁剪切应力，在血管疾病的发展和进展中所起的确切作用仍不清楚，这在很大程度上是因为缺乏人体体内研究。尽管对人体壁面剪切应力进行非侵入性成像仍然存在技术挑战，但血管解剖结构可以以足够高的分辨率成像，从而可以重建用于计算血流动力学研究的三维模型。在本文中，我们提出了一个完全无创的磁共振成像（MRI）协议，提供了颈动脉分叉的几何形状和流量，在体内血流动力学可以计算。地图的平均值，振荡和梯度的壁面切应力为两个正常的人受试者，他们的数据进行了比较与那些计算为一个理想化的颈动脉分叉model.Methods：MRI协议的开发，以获得所有必要的图像数据，扫描时间适合患者的研究。利用两名正常志愿者的序列黑血MR图像重建颈动脉分叉腔的三维模型。共同和颈内动脉流速波形确定从MRI相衬速度成像在相同的主题，并用于施加充分发展的速度边界条件的计算模型。结果：2例受试者的活体MRI重建模型在分支角度、球的大小和范围以及三维曲率方面存在明显差异。各种壁面切应力指数的图谱显示，体内模型之间以及体内模型与理想模型之间的模式存在明显的质的差异。二次，螺旋流动模式，主要是由不对称和弯曲的体内几何形状，被发现在确定所产生的壁面剪切应力模式中发挥了关键作用。在体内的流量波形的使用被发现发挥一个小的，但值得注意的作用，在一些壁面剪切应力behavior.Conclusions：传统的“平均”颈动脉分叉模型掩模有趣的血流动力学功能，观察来自正常人受试者的非侵入性成像的现实模型。在体内的壁剪切应力模式的受试者间的变化的观察支持的概念，更确凿的证据，在血管疾病中的作用，血流动力学可能来自这样的个人研究。这里提出的技术，当结合受试者特定的MRT测量颈动脉斑块的厚度和成分，提供了必要的工具，完全无创的，前瞻性的，在体内人体研究的血液动力学和血液动力学与血管疾病的关系。
Purpose: The precise role played by hemodynamics, particularly wall shear stress, in the development and progression of vascular disease remains unclear, in large part because of a lack of in vivo studies with humans. Although technical challenges remain for noninvasively imaging wall shear stresses in humans, vascular anatomy can be imaged with sufficiently high resolution to allo is reconstruction of three-dimensional models for computational hemodynamic studies. Ln this paper we present an entirely noninvasive magnetic resonance imaging (MRI) protocol that provides carotid bifurcation geometry and flow rates from which the in vivo hemodynamics can be computed. Maps of average, oscillatory and gradients of wall shear stress are presented for two normal human subjects, and their data are compared with those computed for an idealized carotid bifurcation model.Methods: An MRI protocol was developed to acquire all necessary image data in scan times suitable for patient studies. Three-dimensional models of the carotid bifurcation lumen were reconstructed from serial black blood MR images of two normal volunteers. Common and internal carotid artery flow rate waveforms were determined from MRI phase-contrast velocity imaging in the same subjects and were used to impose fully developed velocity boundary conditions for the computational model. Subject-specific time-resolved velocities and wall shear stresses were then computed with a finite element-based Navier-Stokes equation solverResults: Models reconstructed from in vivo MRI of two subjects showed obvious differences in branch angle, bulb size and extent, and three-dimensional curvature. Maps of a variety of wall shear stress indices showed obvious qualitative differences in patterns between the in vivo models and between the in vivo models and the idealized model. Secondary, helical flow patterns, induced primarily by the asymmetric and curved in vivo geometries, were found to play a key role in determining the resulting wall shear stress patterns. The use of in vivo flow rate waveforms was found to play a minor but noticeable role in some of the wall shear stress behavior observed.Conclusions: Conventional "averaged" carotid bifurcation models mask interesting hemodynamic features observed in realistic models derived from noninvasive imaging of normal human subjects. Observation of intersubject variations in the in vivo wall shear stress patterns supports the notion that more conclusive evidence regarding the role of hemodynamics in vascular disease may be derived from such individual studies. The techniques presented here, when combined with subject-specific MRT measurements of carotid artery plaque thickness and composition, provide the tools necessary for entirely noninvasive, prospective, in vivo human studies of hemodynamics and the relationship of hemodynamics to vascular disease.