| 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. |
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