Computational Fluid Dynamic Study Of The Effect Of Flow Diverter Treatment On The PComA-Aneurysmal Hemodynamics

Part One:The Feasibility Study of Modeling Flow Diverters using a Porous Medium ApproachOBJECTIVE:The flow diverter (FD) is a novel device aimed at reconstructing the parent artery and eradicating the aneurysm. Numerical simulations based on virtual FD deployment allow the assessment of the complex nature of aneurismal flow changes before the actual intervention but are demanding on computational resources. Here, we present an alternative strategy of modeling FD effects using a porous medium to reduce demands on time and complexity of the simulation procedure for application in clinical research.MATERIALS AND METHODS:Ten patient-specific aneurysm models were reconstructed from retrospectively collected diagnostic 3D-DSA images. Virtual FDs were deployed (SolidWorks, Meshmixer) and porous medium patches were constructed at the ostium with a research CFD prototype (Siemens Healthcare GmbH). Hemodynamics inside the aneurysm based on these two approaches was calculated (CD-adapco) and resulting changes compared.RESULTS:Both approaches yielded similar results. All the hemodynamic paramiters have no significate differences between two approaches (p-value>0.05). And by Bland-Altman analyzing, all the hemodynamic parameters have agreement between these two methods. Meanwhile, mean wall shear stress (WSS) and mean pressure of the aneurysmal wall correlated significantly (r=0.8, r=1.0, p-value<0.05) as did mean velocity, mean pressure at a region inside the aneurysm, at the ostium and at a cross section containing the main vertex (for velocities r=0.9; for pressures r=1.0, p-value<0.05). The use of porous medium patches reduced simulation times by 57.26%, and simplified the CFD preparation.CONCLUSIONS:Using a porous medium approach yields comparable hemodynamic alterations as direct virtual FD simulations but at the same time greatly reduces modeling complexity and computation time. And proved the feasibility of porous medium approach in CFD simulation.Part Two:Computational Fluid Dynamic Study of the Effect of Flow Diverter Treatment on the PComA-Aneurysmal HemodynamicsOBJECTIVE:Hemodynamic factors are commonly believed to play an important role in the pathogenesis, progression, and rupture of cerebral aneurysms. Endovascular treatment involves the deployment of a flow-diverter (FD) that covers the aneurysm orifice, thereby reducing the blood flow into the aneurysm and mitigating the risk of rupture. But, the effect on side branches caused by placement of FD, and the side branch affect the hemodynamics in the aneurysm all remains unclear. In this study, based on the patient-specific posterior communicating artery aneurysm (PComA-aneurysm) models we aim to compare the hemodynamic changes of PComA and aneurysm before and after FD deployment, and analyse the effect on the FD treatment-inducing-hemodynamic changes caused by have or have not PComA, PComA’s diameter, the place of PComA by using CFD simulations.MATERIALS AND METHODS:Eleven patient-specific PComA-aneurysm models were reconstructed from retrospectively collected diagnostic 3D-DSA images for CFD simulation study.11 aneurysm models without PCom vessel were constructed (Geomagic Studio 9.0, Meshmixer) based on those patient-specific PComA-aneurysm models. Also, moved the location of PCom vessel of 5 PComA-aneurysm models from near the neck of aneurysm to side and top of the aneurysm. Porous medium patches were constructed at the ostium with a research CFD prototype (Siemens Healthcare GmbH). Hemodynamics inside the aneurysm and PCom vessel before and after this porous medium approaches were calculated (CD-adapco) and resulting changes compared.RESULTS:After the FD treatment, the inflow volume, mean velocity in the aneurysm and the mean WSS of aneurysm wall reduced significantly (P=0.003, P=0.003, P=0.003). The mean pressure both inside aneurysm and of aneurysm wall also reduced (P=0.006, P=0.003), but the flow volume in the PCom vessel almost unchanged (P=0.075). Before FD deployment, the PComA aneurysms with PCom vessel have higher inflow volume and lower mean pressure both inside and of aneurysm wall compare with the aneurysm without PComA (P=0.041, P=0.016, P=0.021); there is linear correlation between the diameter and the flow volume of PCom vessel (R2=0.733, P=0.001); both inflow volume and mean pressure inside aneurysm have significant difference among the PComA aneurysm with three different location (P<0.05). After FD have been deployed, the PComA aneurysms with PCom vessel have higher inflow volume, mean velocity in the aneurysm, the mean WSS of aneurysm wall, and lower mean pressure both inside and of aneurysm wall compare with the aneurysm without PComA (P<0.05), also the reduction of mean pressure have significant difference between these two groups (P=0.033, P=0.016); diameter of PCom vessel showed linear correlation with the flow volume of PComA (R2=0.697, P=0.001), and also with the reduction of flow volume inside PComA and mean velocity in the aneurysm (R2=0.539, R2=0.416, P=0.010, P=0.032); among the three groups of different location of PCom vessel (near neck, side and top of aneurysm), the mean WSS and mean pressure of aneurysm wall have significant difference, also the reduction of inflow volume and mean pressure of wall showed difference among them (P<0.05).CONCLUSIONS:This study confirmed that the FD implantation give the protective effect of the altered hemodynamics in the aneurysm while not influence the blood flow in PComA, and the flow volume in PComA is significantly associated with the diameter of PCom vessel. The PComA aneurysm without PCom vessel is more likely to be well treated by FD device than that with PCom vessel. The PComA aneurysm with PComA located near aneurysm neck enjoyed the best hemodynamic change, while top-type PComA aneurysm has the worst. This study provided the theoretical foundation for the future threating the aneurysm with side branch by using FD device.