Virtual Reality Visualization Of Cfd Simulated Blood Flow In Cerebral Aneurysms Treated With Flow Diverter Stents

Simple Summary Cerebral aneurysm is one of the brain diseases with high mortality and morbidity rates when an abnormal dilation of a vessel occurs and, in severe conditions, ruptured, and blood flows into the space around the brain. A flow diverting stent is one of the devices that has been developed to treat brain aneurysms by diverting the blood flow away from the aneurysm sac. Several important considerations need to be taken into account in stent positioning inside the artery. Computational fluid dynamics is a useful tool in predicting the devices' efficacy and post-treatment complications but the obtained data need to be visualized in an interactive environment for non-fluid-dynamics experts. We found that virtual reality provides a fully immersive interactive environment for the analysis of blood flow variations in the presence of flow diverters. Therefore, we developed a method to convert the numerical data to three-dimensional objects in virtual reality environments usable for both neurosurgeons and patients. Cerebral neurosurgeons could make easier decisions about selecting the treatment devices, and patients could walk inside their virtual treated aneurysm, reducing their anxiety and making their pre-treatment consulting process more efficient. Virtual reality (VR) has the potential to be a powerful tool for the visualization of simulated blood flow in cerebral aneurysms. This paper presents our study aimed at developing the VR visualization of computational fluid dynamics (CFD) simulations of cerebral aneurysms treated with flow-diverting (FD) stents. First, a spherical sidewall aneurysm located at a simplified internal carotid artery was considered for investigating the impact of stent deployment and positioning on the corresponding spatially time-varying blood flow behavior. The three-dimensional unsteady blood flow over a cardiac cycle was simulated numerically using the finite volume method, and the distributions of hemodynamic parameters inside the aneurysm sac, and on its wall, were presented with and without stent cases. Two stent positions, with and without a gap between the artery wall and stent, were considered to show the influence of correct stent position on aneurysm treatment. Second, a straightforward workflow was developed to import, process, and visualize the CFD analysis data in a VR environment by using open-source software with a high resolution. The Unity3D engine was used for displaying the processed animations in a VR environment operated on a head-mounted display (HMD). The refining process of each frame of time-varying CFD data was automated. The animated flow elements rendered in the VR environment were velocity vectors, velocity contours, streamlines, particle traces, and point clouds. CFD results showed that proper stenting facilitates thrombosis and occlusion of the aneurysm by modification of the flow patterns, which leads to lower inflow jet velocities into the aneurysm, longer turnover time, lower aneurysm-averaged kinetic energy, and lower wall shear stress. Additionally, the results indicated that a gap between the stent and the parent artery may lead to undesirable hemodynamic alterations. The VR visualization illustrated that the recognition of the potential in danger regions of aneurysms and the evaluation of the performance of FD stents in aneurysm treatment can be conducted without the need for several slices through the parent artery and aneurysm, as is required for traditional postprocessing methods.Through VR visualization, the details of the simulation results become readily available by navigating in the 3D animated flow elements using a high-degree-of-freedom headset.