The Patient-Specific Model Establishment Of Intracranial Aneurysm Based On CT Angiography Images And Computational Fluid Dynamics Analysis

Objectives: Based on CT angiography image date of clinical patient whosuffered from intracranial aneurysm, a patient-specific rigid model wasestablished to estimate the characteristic of hemodynamic parameters by usingCFD software and reveal the hemodynamic mechanism of the growth andrupture of intracranial aneurysm.Methods: A case of intracranial aneurysm was chosed from clinic, ofwhich the images saved as DICOM format were obtained after CTangiography. A solid model was generated after image segmentation by usinggray threshold, region growth and manual segmentation, image3Dreconstruction using marching cubes algorithm, triangular mesh modeloptimization and then NURBS surface model reconstruction based on rapidsurface reconstruction technical. Mesh the solid in ANSYS ICEM CFD, setfluid properties,initial and boundary conditions and calculate in FLUENT,implement data visualization in ANSYS CFD POST. All these softwares areintegrated in ANSYS Workbench. Finally, some differences can be displayedin different states.Results: A supraclinoid aneurysm model and a modified model by virtualremoval of the aneurysm which represent the pre-aneurysm state wassimulated respectively. The results were analysed from three aspects: differentinlet velocities in steady flow; different models in steady flow and ideallypulsatile flow. The contour plot of WSS and total pressure, velocitystreamline from the inlet and velocity vector on the specific plane wereobained. When the inlet velocity rise which is substitute for the blood pressurein steady flow, the distribution of WSS and tatal pressure became morecomplex. Meanwhile, no change was found in the flow pattern. The area located on the bend of the modified model corresponding to the place of theaneurysm growth was showed by characteristic low WSS. The value of WSSand total pressure were always fluctuate in transient flow, while the maximumappeared at the peak systole. The vortex in the lumen of aneurysm keptmoving during cardiac cycle, swirl intensity reach to the highest at the peaksystole. The flow pattern in transient flow is similar as in steady flow.Conclusion: Using the patient-specific rigid model of intracranialaneurysm based on CT angiography image date in CFD analysis can get morepractical informations about the distribution of hymodynamic parameters andthe flow characteristics, which may contribute to illstrate the pathogenesis ofthe intracranial aneurysm;The characteristic low WSS area located on the bendof vessel may indicate the growth of an aneurysm; Flow pattern may be moredependent on the geometry of the aneurysm and parent artery; In contrast withsteady analysis, transient analysis can show the variation of flow pattern,complex and periodic changes of the WSS and total pressure distribution.Unsteady flow pattern may lead to aneurysm rupture;To illustrate the naturalhistory of intracranial aneurysm, perianeurysmal environment factor should beconsidered besides hymodynamic factor.