Computational Fluid Dynamic Study Of Blood Flow Dynamics In Rabbit-specific Cerebral Aneurysm Models Treated Solely By Lower Porosity Stent Placement

Part one:Establishment of rabbit-specific numerical intracranial aneurysm model and analysis of hemodynamicsObjective:To establish a numerical model of rabbit-specific aneurysm model based on 3D rotation angiography image and analyze the hemodynamic characters of the aneurysms.Methods:we established histologically simulating human aneurysms by using elastase to digest the right common carotid artery.The 3DRA images of 16 rabbit-specific aneurysm models were transferred into 3 DM AX then GEOMAGIC 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, streamline, velocity profile and pressure profile.Results:We analyzed hemodynamic characters of rabbit-specific aneurysm models including WSS distribution, maximum WSS, streamline, intra-aneurysmal flow pattern, velocity profile, velocity and width of inflow jet, location and size of impaction zone.Conclusion:The hemodynamic characters of rabbit-specific aneurysm model are well consistent with that of the human intracranial aneurysm.Part two:Study of hemodynamic changes induced by virtual placement of the high porocity stent across rabbit-specific aneurysmObjective:The goal was to study the effects of the high porocity stent on aneurysm hemodynamics using computational fluid dynamics.Methods:We obtained the DRA images of 14 rabbit-specific aneurysm models and the Micro-computed tomographic angiography images of the stent samples extracted from rabbits treated by solo stent.computed tomographic angiography images. The geometries of rabbit-specific aneurysm models were reconstructed from the DRA images. The geometry of high porocitystents were reconstructed from the computed tomographic angiography images.To deploy the stent in the aneurysm models, the part geometries of the stents were virtually deformed to fit into the parent vessel lumen across the aneurysm neck. The separately reconstructed aneurysm and stent geometries were merged in a single model in ICEM-CFD and meshed. 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, streamline, velocity profile and pressure profile of both the stented and the unstented aneurysms Some comparisons of the hemodynamic characters of the stented aneurysms with that of the unstented aneurysms including WSS, streamline, intra-aneurysmal flow pattern, velocity profile, velocity and width of inflow jet, location and size of impaction zone were also madeResults:the elevated WSS area was more significantly reduced by stenting,The complex flow pattern observed in the unstented aneurysm was suppressed by stenting.but the pressure on the inner wall of the pressure of the aneurysm was not suppressed by stenting. Stent placement lowered the wall shear stress in the aneurysm, In the stented and unstented aneurysms paring research, there was significant statistic difference in the WSS magnitude on the dome and the distal pouch of the aneurysm between the stented aneurysms group and the unstented aneurysms group (P<0.01),but there was no significant statistic difference in the WSS on the proximal wall near the neck(P=0.13).There was also no significant statistic difference in the pressure on the dome and that on the inner wall of the aneurysm near the proximal and distal pouch of the aneurysm(P>0.01).Conclusion:Aneurysm hemodynamic parameters were significantly modified by placement of low porocity stents.Part three:Comparison of the results of numerical and experimental studies in the stented rabbit-specific aneurysm modelObjective:To investigate the different hemodynamic characters in the healed and the unhealed aneurysms and characterize possible associations with the occlusion of the aneurysms.Methods:We devided the 14 rabbit-specific aneurysm models intotwo groups:the healed group (n=10) and the unhealed group (n=4), according to the follow-up angiography. Some comparisons of the hemodynamic characters of the healed aneurysms with that of the unhealed aneurysms including WSS, pressure were made.Results:In the paring research, There was significant difference between the two groups,although there was no significant statistic difference in the WSS magnitude on the dome and the distal pouch of the aneurysm between the heaed aneurysms group and the unhealed aneurysms group (P>0.01).Conclusion:The computed results are verified by experimental studies.further investigation are needed in this area in larger series.