【作者】 卢海涛；

【导师】 刘建民； 许奕； 洪波； 赵文元； 黄清海； 王盛章；

【作者基本信息】 第二军医大学 ， 外科学， 2010， 博士

【摘要】 目的：颅内动脉瘤破裂是引起蛛网膜下腔出血的最常见原因,而蛛网膜下腔出血具有非常高的病死率和病残率,因此对动脉瘤的病因学及治疗机制研究具有非常重要意义。尽管目前仍不明确动脉瘤的发生和生长的机理,血流动力学因素被普遍认为在动脉瘤病理发展过程中起重要作用。我们对颅内动脉瘤进行血流动力学数值模拟并获取血流动力学参数,分析血流动力学因素在颅内动脉瘤发生及介入治疗后复发中的作用,判断引起动脉瘤发生与介入治疗后复发的特定血流动力学因素,为动脉瘤的临床预防、治疗提供理论依据。方法：首先,借助计算流体力学有限元方法软件建立研究动脉瘤的数值模型,分别研究在动脉瘤发生之前该节段载瘤动脉以及动脉瘤发生后相应部位的血流动力学特征,获取血流动力学的各种参数。对比描述不同区域血流动力学参数特点,分析血流动力学因素在颅内动脉瘤发生、生长的作用。具体如下：获取颅内29例后交通动脉瘤患者的脑血管三维旋转造影资料,初步剪切、加工后,经3DMAX软件转换、定标,再通过GEOMAGIC软件进一步切割、截取和光滑处理,将去除动脉瘤的载瘤血管作为动脉瘤发生前的原始状态,所得结果在ANSYS ICEM中建立有限元网格,在一定的假设前提下,用ANSYS CFX配置边界条件后并进行计算,得出载瘤血管的壁面切应力、壁面压力、流线、血流速度等多种血流动力学研究参数。其次,筛选出经过致密栓塞后造影复查证实复发的10例动脉瘤,与致密栓塞后未复发的10例形态学近似的动脉瘤进行配对。对于用同样的方法处理后的动脉瘤进行数值模型建立并进行血流动力学分析,获得相应的血流动力学参数。比较两组病例载瘤动脉的血流动力学相关参数并统计学分析。结果：根据研究结果可以分析和计算颅内动脉瘤的多种血液动力学参数,包括：壁面切应力、壁面压力、流线及流场基本特征、速度血流、动脉瘤内血流方式、射入流宽度、冲击域位置及大小。从而可以更直观清晰的认识颅内动脉瘤的血液动力学特点。为了找出影响动脉瘤发生的血流动力学因素,在上述各项参数中进行比较和分析。对在动脉发生之前的载瘤动脉不同节段壁面剪应力比较：近端血管平均WSS为7.38±3.82Pa,远端血管平均为7.19±3.14Pa,原动脉瘤区平均为10.05±5.39Pa。原动脉瘤区平均WSS要明显高于远端血管和近端血管,两两比较的统计分析有统计学差异。载瘤动脉不同节段之间比较壁面压力,结果近端血管平均压力为1301.27±1512.86Pa,远端血管平均为1087.33±1230.37Pa,原动脉瘤区平均为1343.19±1487.61Pa,尽管原动脉瘤区平均压力要高于远、近端血管,但仅原动脉瘤区与远侧血管之间存在统计学差别。载瘤动脉不同节段之间比较血流速度,近端血管平均流速为0.61±0.38m／s,远端血管平均流速为0.56±0.32m／s,原动脉瘤区平均流速为0.57±0.32m／s。两两比较,差别均无统计学意义。动脉瘤发生前、后各项血流动力学参数比较,仅壁面剪应力存在统计学显著性差异,发生前壁面剪应力要高于发生后的壁面剪应力。介入治疗后随访时复发动脉瘤和未复发动脉瘤配对后,比较瘤颈远、近端和瘤颈中心区域的WSS,结果均无统计学意义。在未复发动脉瘤的不同部位之间壁面剪应力比较,同样无统计学意义。然而在复发组中不同部位壁面剪应力比较：瘤颈近侧剪应力平均为6.01±6.27Pa,瘤颈远侧剪应力平均为7.34±6.31Pa,瘤颈中心剪应力平均为5.36±6.46Pa。三者中瘤颈远侧平均剪应力为最高。统计分析：瘤颈口的远、近端两两比较及瘤颈中心与瘤颈远侧两两比较WSS有统计差别,而瘤颈中心与近侧比较WSS无统计学差别。在复发组中不同部位壁面压力比较：瘤颈近侧压力平均为854.09±1120.98Pa,瘤颈远侧压力平均为851.88±1137.39Pa,瘤颈中心压力平均为862.03±1056.14Pa,但各部位壁面压力比较无统计学意义。复发组中不同部位血流速度比较,各部位速度差异亦无统计学意义。配对样本的复发与未复发两组射入流宽度无统计学差异。而冲击域大小存在统计学差异,复发组的冲击域要小于未复发组。结论：利用计算流体力学数值模拟方法,可很好的反映颅内动脉瘤血流动力学特点,获取血流动力学各种参数。颅内动脉瘤的发生与产生前的该血管节段(载瘤动脉)血液动力学特征有关。载瘤血管不同节段的壁面剪应力分布存在差异,高的壁面剪应力可能诱发动脉瘤。介入治疗后当载瘤动脉存在明显壁面剪应力分布不均匀和具有较小冲击域时,动脉瘤容易复发。更多还原

【Abstract】 Objective:Cerebral aneurysm rupture is the most common cause of subarachnoid hemorrhage, well known for its very high mortality and mobility. Therefore, the etiology of the aneurysms and the treatment mechanism has great importance.Although how aneurysms initiate and grow is still unclear, hemodynamic factors are thought to be important in the pathogenesis. The aim of this paper is to simulate and obtain related parameters of hemodynamics of intracranial aneurysms. Analyze the effect of hemodynamic factors on origin and growth of intracranial aneurysms. Identification of specific hemodynamic factors responsible for aneurysm initiation and provide theoretic support to clinical prophylaxis and treatment of aneurysm.Methods:First of all, used finite element method with computational fluid dynamics software to establish numerical model of aneurysm, studied the hemodynamic characteristics of parent artery before the initiation of aneurysms and the corresponding parts after aneurysms occurred, acquired hemodynamic parameters. Compared and described the characteristics of different regions and analyzed the effect of hemodynamic factors in the initiation of intracranial aneurysm.The 3DRA image of 29 post-communicating aneurysms were transferred into 3DMAX and GEOMAGIC software for being segmented and smoothed surface data. The surface data was imported into ANSYS CFD in order to create finite element grids. After meshing, we applied ANSYS CFX to create configuration files for fluid field computations and structural mechanics computations respectively, which include the setting of material properties, boundary condition and time step. At last we obtained the hemodynamic parameters including wall shear stress, wall pressure, streamline, and stream velocity. We study the hemodynamic characteristics of parent artery before aneurysm occurrence and the hemodynamics of before and after aneurysms formation respectively. Second, we focused on 10 patients with intravascular aneurysms accepted endovascular treatment and after a period of time aneurysms recurred. To Pairred this group with another similar morphological group which also accepted treatment but not recurred. By the same method we built patient-specific computational models of 20 aneurysms, calculated wall pressure, wall shear stress, blood velocity, inflow jet, and impaction zone. We compared these parameters with statistical analysis. Results:We analyzed hemodynamic characters of the intracranial aneurysm including WSS, wall pressure, streamline, within aneurysmal flow pattern, stream velocity, width of inflow jet, location and size of impaction zone.To identify impact of hemodynamic factors in occurred aneurysm, the above parameters were compared and analyzed. Compare the wall shear stress of the different parts of vessel before aneurysm formed, the average WSS of proximal vessel was 7.38±3.82Pa, the average WSS of distal vessel was 7.19±3.14Pa, the average WSS of the original aneurysm was 10.05±5.39Pa. Original aneurysm area is obviously higher than the distal and proximal blood vessels. Comparisons between groups have statistically difference. Compare the wall pressure of the different parts of vessel, the average WP of proximal vessel was 1301.27±1512.86 Pa, the average WP of distal vessel was 1087.33±1230.37 Pa, the average WP of the original aneurysm was 1343.19±1487.61 Pa. Although the average pressure of the original aneurysm area is higher than the proximal and distal vessels, but only between the original zone and distal vascular has statistical difference. the stream velocity among different parts of parent arteries has no statistical difference. the average stream velocity of proximal vessel was 0.61±0.38m/s, the average stream velocity of distal vessel was 0.56±0.32m/s, the average stream velocity of the original aneurysm was 0.57±0.32m/s. The stream velocity among different parts of parent arteries has no statistical difference. Compare the parameters of before and after aneurysms formation only wall shear stress has significantly statistical difference.Paired the recurred aneurysms and un-recurred aneurysms and compared wall shear stress of different locations. The results have no statistical difference. The same results existed in different locations of un-recurred aneurysms. However, in recurred group compared the wall shear stress in different parts:the average wall shear stress of the proximal part of the ostium was 6.01±6.27Pa,the distal part was 7.34±6.31Pa,the central part was 5.36±6.46Pa.The distal part is highest in three parts. There has statistical difference either between the central and distal part of the ostium or between the proximal and the distal part. In recurred group we compared the wall pressure and stream velocity in different parts. The results has no statistical difference.It was found that in paired samples of recurred aneurysms and unrecurred aneurysms has no statistical difference in the width of inflow jet (P=0.779).But there was statistical difference in the magnitude of impaction zone (P=0.045).Conclusion:The numerical simulation is a reliable method, reflect the hemodynamics of cerebral aneurysm, obtain the varieties parameters of hemodyanmics. The origin of aneurysm has relation with the hemodynamic characteristic of parent artery before the aneurysm formation. There were differences among different parts of vessel. High magnitude of wall shear stress may initiate an intracranial aneurysm. When the parent arteries own obviously uneven distribution of wall shear stress, it can be easily recur. So was the aneurysms has small impaction zone.更多还原