Response by Oshida et al to Letter Regarding Article, “Wall Shear Stress and T1 Contrast Ratio Are Associated With Embolic Signals During Carotid Exposure in Endarterectomy”
Response by Oshida et al to Letter Regarding Article, “Wall Shear Stress and T1 Contrast Ratio Are Associated With Embolic Signals During Carotid Exposure in Endarterectomy”
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Oshida 等人对有关文章“壁剪切应力和 T1 对比度与动脉内膜切除术中颈动脉暴露期间的栓塞信号相关”的信件的回应
DOI：
10.1161/strokeaha.118.023441
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发表时间：
2018
期刊：
影响因子：
8.3
通讯作者：
Ogasawara Kuniaki
中科院分区：
文献类型：
--
作者：
Oshida Sotaro;Mori Futoshi;Ogasawara Kuniaki
谢谢你对我们的报告感兴趣。1在解决策略上，使用商业软件对每条狭窄的颈动脉进行网格划分，在边界处创建5层精细棱镜网格的四面体网格。在狭窄模型中，网格平均包含57万个节点和2 27万个四面体和棱柱体单元。在颈总动脉上增加一个直入口延长以获得充分发展的层流。最近的研究表明，计算流体动力学分析的颈动脉狭窄的区域可以通过层流假设进行。2,3接下来，在管腔分割方面，利用术前飞行时间和颈椎区域钆增强三维磁共振血管造影的立体光刻技术生成患者特定的几何形状。已有研究表明，钆增强三维磁共振血管造影显示的颈内动脉（ICA）狭窄程度和长度与动脉导管造影显示的狭窄程度和长度有显著相关性。4对于颈动脉的三维重建，血流量的阈值磁共振值是由一名对其他数据不知情的神经外科医生半自动提取的。颈外动脉直径小于1mm的小分支因不适合层流分析而被排除在分析之外。为了提高组成面三角形的质量，对立体光刻进行了网格化处理。最后，在非稳态情况下，采用Navier-Stokes方程和连续性方程，利用高性能计算系统和有限体积求解器对流量进行了计算流体动力学分析。为了稳定压力和动量计算的收敛性，我们在基于压力的隐式求解器上应用了压力链接方程算法的半隐式方法。在流体领域，得到了三维非定常不可压缩层流场。假设管壁为刚性，管壁处采用无滑移边界条件。血液被认为是一种不可压缩的牛顿流体。老年人的归一化脉冲质量流量波形已被提出。5在之前的研究中，ICA和颈外动脉出口处采用无牵拉边界条件，计算流体动力学分析假设ICA和颈外动脉均为无牵拉边界条件，并通过患者的具体超声数据得到了很好的验证。因此，我们对ICA和颈外动脉应用了无牵拉边界。
Thank for your interest in our report. 1 On solution strategy, each carotid artery with a stenosis was meshed using commercial software to create tetrahedral meshes with 5 layers of finer-prism meshes at the boundary. On average, the meshes comprised 570 000 nodes and 2 270 000 tetrahedral and prismatic elements in the models with stenosis. A straight inlet extension was added to the common carotid artery to obtain fully developed laminar flow. Recent studies have demonstrated that computational fluid dynamics analysis of a carotid artery with an area of stenosis can be performed by assuming laminar flow. 2, 3 Next, on lumen segmentation, patient-specific geometries were generated using stereolithography from preoperative timeof-flight and gadolinium-enhanced 3-dimensional magnetic resonance angiography of the cervical region. A previous study demonstrated that the degree and length of internal carotid artery (ICA) stenosis on gadolinium-enhanced 3-dimensional magnetic resonance angiography correlated significantly with those on angiography with arterial catheterization. 4 For 3-dimensional reconstruction of the carotid arteries, the threshold magnetic resonance value of blood flow was semiautomatically extracted by a neurosurgeon blinded to other data. Small branches with diameters< 1 mm from the external carotid artery were excluded from analysis as unsuitable for analysis of laminar flow. The stereolithography was remeshed to improve the quality of the constituent surface triangles.Finally, on flow rates, computational fluid dynamics analysis was performed using a high-performance computing system and a commercial solver with a finite volume method under the unsteady-state situation and governed by the Navier-Stokes and continuity equations. We applied the Semi-Implicit Method for Pressure-Linked Equation algorithm on a pressure-based solver, that is implicit, to stabilize convergence calculations of pressure and momentum. For the fluid domain, 3-dimensional unsteady incompressible laminar flow fields were obtained. Vessel walls were assumed to be rigid, and no-slip boundary conditions were applied at the walls. Blood was assumed to be an incompressible Newtonian fluid. Normalized pulsatile mass flow rate waveforms of older adults have been presented previously. 5 In a previous study, traction-free boundary conditions were applied at the outlets of the ICA and external carotid artery, and the computational fluid dynamics analysis assumed traction-free boundary conditions for both the ICA and external carotid artery that were well validated by specific ultrasound data of patients. 3 As a result, we applied traction-free boundaries for the ICA and external carotid artery.