Ohta M, Hirabayashi M, Wetzel S, Lylyk P, Wata H, Tsutsumi S, Rüfenacht D A
Section of Neuroradiology, Department of Radiology, Geneva University Hospital, Geneva; Switzerland.
Interv Neuroradiol. 2004 Dec 24;10 Suppl 2(Suppl 2):85-94. doi: 10.1177/15910199040100S216. Epub 2008 May 15.
In addition to providing a skeleton for vessel reconstruction, stent implantation as used for cerebral aneurysm treatment can induce flow redirection, thus reducing vortical flow velocities within the aneurysm cavity. Further, stent characteristics such as strut size, porosity and cell shape influence the changes in intra-aneurysmal flow by analog simulations. The purpose of this computer simulation study was to visualize the flow pattern over the entire neck area of a side wall aneurysm while changing the stent parameters. A 3-D computer model aneurysm was constructed to have a parent artery of 5 mm diameter and an aneurysm of 10 mm diameter. The distance between the midline of main artery and center point of the aneurysm was 6.8 mm, providing a neck length of 5 mm, a width of 3.6 mm, and a neck area of 14 mm 2. The simulations were carried out with a Finite Element Method based flow simulation package. The incompressible Navier-Stokes equation was solved for a steady flow with a mean speed of 290 mm/s, steady viscosity of 3.83 cp, and density of 1.0 g/cm3. Two parallel stent struts (dimensions: 100 mum m 100 mum m 2.0 mm) were introduced into the plane of the aneurysm neck. The fraction of the aneurysm neck cross-section occupied by the stent was 2.83% in all cases. The velocity distribution through the neck of the aneurysm was calculated for three different choices of separation between the struts for each of two orientations of the struts (parallel and perpendicular) relative to the vessel axis. The flow pattern in the aneurysm was composed of an inflow zone at the distal neck and of an outflow zone at the proximal neck. The placement of stent struts at the aneurysm neck resulted in a decrease in the mean speed in the aneurysm. The degree of reduction and the distribution of flow through the neck did depend on the orientation of the stent struts. The struts, when placed parallel or perpendicular to the parent vessel axis affected the mean speed through the aneurysm neck differently.
除了为血管重建提供支架外，用于治疗脑动脉瘤的支架植入可引起血流方向改变，从而降低动脉瘤腔内的涡流速度。此外，支架的特征（如支柱尺寸、孔隙率和单元形状）通过模拟影响动脉瘤内血流的变化。本计算机模拟研究的目的是在改变支架参数的同时，可视化侧壁动脉瘤整个颈部区域的血流模式。构建了一个三维计算机模型动脉瘤，其母动脉直径为5mm，动脉瘤直径为10mm。主动脉中线与动脉瘤中心点之间的距离为6.8mm，颈部长度为5mm，宽度为3.6mm，颈部面积为14mm²。使用基于有限元法的血流模拟软件包进行模拟。求解不可压缩的纳维-斯托克斯方程，以获得平均速度为290mm/s、稳定粘度为3.83cp和密度为1.0g/cm³的稳定血流。将两个平行的支架支柱（尺寸：100μm×100μm×2.0mm）引入动脉瘤颈部平面。在所有情况下，支架占据的动脉瘤颈部横截面比例为2.83%。针对支柱相对于血管轴的两种方向（平行和垂直），在支柱间距的三种不同选择下，计算通过动脉瘤颈部的速度分布。动脉瘤内的血流模式由远端颈部的流入区和近端颈部的流出区组成。在动脉瘤颈部放置支架支柱导致动脉瘤内平均速度降低。降低程度和通过颈部的血流分布确实取决于支架支柱的方向。当支柱平行或垂直于母血管轴放置时，对通过动脉瘤颈部的平均速度影响不同。
