## 1 Introduction
It is noted that the specifications of FD stents such as stent type, mesh porosity, and mesh pore density are other determining factors in the greater device efficacy, which have been considered by researchers using CFD simulations [6; 8; 16]. In addition to the appropriate selection of pore size and density, the device positioning against the parent artery wall remains vital. The dependency of aneurysm occlusion on the space or gap between the flow diverter and the parent artery has been considered using CFD investigations, and the results demonstrate that even a small gap causes the aneurysm to be blocked incomplete and remain permeable longer because of the jet-like blood flow through the gap into the aneurysm sac [10; 16; 17]. All aforementioned studies have indicated that CFD simulations can help to design better devices, and also offer clinicians insight about decision-making, personalize the treatment methods, and provide valuable information to plan stent deployment for the treatment of cerebral aneurysms. CFD is able to produce spatiotemporal results for the millions of elements of the model during an entire cardiac cycle, which are usually viewed at a single time point or time-averaged on standard 2D displays. In addition, people who did not perform the CFD analysis, for example, clinicians who would like to use the CFD data, may not intend to utilize the CFD data while there are other available visualization tools [18]. The simulation data need to be visualized in an appropriate environment to provide direct and intuitive knowledge and insight into the FD-stent treatment and its outcome. Visualization in virtual reality (VR) may be an ideal solution. Using a head-mounted display (headset), in combination with a computer system, a user is able to experience and naturally interact with a digital simulated three-dimensional (3D) digital environment, complete with images, sounds, and other sensations. The user (wearing the headset) is able to see and manipulate (move, rotate, and/or scale) objects of interest in the virtual environment. Stereoscopic 3D visualization in VR has been illustrated as a powerful, low-cost, noninvasive method for visualizing complex biological systems [19]. The CFD analysis data can be displayed in the VR environment to allow physicians to understand the complex flow patterns of blood within cerebral arteries while \"taking a walk\" inside the aneurysm and observing the velocity, pressure, and stress fields [7]. This is not only a useful means for neurosurgeons to assess the risk of stent treatment but is also a stimulating way for the active training of medical students and preparation of patients before their stent treatment (through education to reduce their anxiety). There are a few studies that have presented a workflow to postprocess the CFD results in a VR environment with biomedical applications. For example, an improved replacement heart valve was designed using CFD simulation to overcome time and financial constraints. The output of the simulations displayed in a virtual reality environment also included innovative 3D interfaces for interacting with the data [20]. Additionally, some workflows were developed to display biomedical CFD analysis results in the virtual environment and were tested for blood flow in arteries [21; 22], congenital cardiovascular disease, the Circle of Willis with respect to cerebral aneurysms, the airway for surgical treatment planning [18], and percutaneous coronary intervention [23]. The results from all these studies suggest that VR immersion significantly improves the accuracy of the placement of the simulated medical devices in complex arterial geometries, relative to traditional display methods with no immersion. Considering the extensive applications of CFD for biomedical purposes, the number of CFD-VR studies, especially related to stented aneurysms, is limited.