Numerous studies assess intracranial aneurysm rupture risk based on morphological and hemodynamic parameter analysis in addition to clinical information such as aneurysm localization, age, and sex. However, intracranial aneurysms mostly occur with a saccular shape located either lateral to the parent artery or at a bifurcation. In contrast, fusiform intracranial aneurysms (FIAs), i.e., aneurysms with a non-saccular, dilated form, occur in approximately 3–13% of all cases and therefore have not yet been as thoroughly studied. To improve the understanding of FIA hemodynamics, this pilot study contains morphological analyses and image-based blood flow simulations in three patient-specific cases. For a precise and realistic comparison to the pre-pathological state, each dilation was manually removed and the time-dependent blood flow simulations were repeated. Additionally, a validated fast virtual stenting approach was applied to evaluate the effect of virtual endovascular flow-diverter deployment focusing on relevant hemodynamic quantities. For two of the three patients, post-interventional information was available and included in the analysis. The results of this numerical pilot study indicate that complex flow structures, i.e., helical flow phenomena and the presence of high oscillating flow features, predominantly occur in FIAs with morphologically differing appearances. Due to the investigation of the individual healthy states, the original flow environment could be restored which serves as a reference for the virtual treatment target. It was shown that the realistic deployment led to a considerable stabilization of the individual hemodynamics in all cases. Furthermore, a quantification of the stent-induced therapy effect became feasible for the treating physician. The results of the morphological and hemodynamic analyses in this pilot study show that virtual stenting can be used in FIAs to quantify the effect of the planned endovascular treatment.

Purpose The treatment of intracranial arteriovenous malformations (AVM) is challenging due to their complex anatomy. For this vessel pathology, arteries are directly linked to veins without a capillary bed in between. For endovascular treatment, embolization is carried out, where the arteries that supply the AVM are consecutively blocked. A virtual embolization could support the medical expert in treatment planning. Method We designed and implemented an immersive VR application that allows the visualization of the simulated blood flow by displaying millions of particles. Furthermore, the user can interactively block or unblock arteries that supply the AVM and analyze the altered blood flow based on pre-computed simulations. Results In a pilot study, the application was successfully adapted to three patient-specific cases. We performed a qualitative evaluation with two experienced neuroradiologist who regularly conduct AVM embolizations. The feature of virtually blocking or unblocking feeders was rated highly beneficial, and a desire for the inclusion of quantitative information was formulated. Conclusion The presented application allows for virtual embolization and interactive blood flow visualization in an immersive virtual reality environment. It could serve as useful addition for treatment planning and education in clinical practice, supporting the understanding of AVM topology as well as understanding the influence of the AVM’s feeding arteries.

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For hemodynamic simulations of intracranial aneurysms boundary conditions (BC) are required. In most cases, these are not patient-specific and thus do not reflect the real flow conditions in the patient. This study investigates the influence of patient-specific inflow BC on intra-aneurysmal hemodynamics. The focus lies on gender and age variations of the patients. To asses the impact, four different inflow curves representing the velocity profile of the inflow over one cardiac cycle is modeled. These four inflow BC are varied in the simulations of each aneurysm from selected subgroups. From the results of the simulations, the hemodynamic parameters are determined for each inflow BC and the percent differences between inflow BC are determined. The results show that the hemodynamic parameters are not robust to varying inflow BC. It can be seen that age has more influence on the hemodynamic parameters than gender. This study demonstrates the dependence of valid hemodynamic parameters on realistic inflow BC. Thus, if available, patient-specific inflow curves are recommended.

aneurysms and to purpose workflow for classification and significance Materials and Methods This was a cross-sectional, retrospective study conducted on 650 patients referred for cerebral DSA at our institution from January 2020 to February 2021. DSA images were analyzed by two interventional neuroradiologists with several years of experience in neurointervention to determine the final configuration of the circle of Willis, normal variants, and the presence of vascular anomalies. Results Arterial fenestrations were found in 0.75% of patients, with the vertebrobasilar system as common location ( 0.46% ). The remaining fenestrations were located at the basilar artery apex (0.1%), anterior communicating artery (0.1%), and distal anterior cerebral artery A2-A3 segment (0.1%). The prevalence of an azygos anterior cerebral artery was 1%. Bihemispheric anterior cerebral artery was found in 6%, hypoplastic A1 segment in 7.7%, and congenital absence of A1 segment in 0.4% of patients. Fetal origin of the posterior cerebral artery was found in 12% of cases. Hypoplastic vertebral artery, right, left, or terminating as posterior inferior cerebellar artery was observed in 1.4% of patients. Trifurcation is more common at the middle cerebral artery junction observed in 1.7% of cases. Accessory middle cerebral artery were seen in 0.15% of cases. Duplications were common in superior cerebellar artery (0.7% cases) and in basilar artery in 0.31% of cases. All kinds of persistent carotid-basilar anastomosis were present in our series including persistent trigeminal artery in 0.3% cases. Persistent internal carotid anastomosis as aberrant intratympanic course of ICA in 0.15% of cases. Others include meningolacrimal and meningo-ophthalmic variants in 0.46% cases. In 0.3% of cases, the dorsal ophthalmic artery was arising from the cavernous segment. 12.6% of aneurysms were associated with intracranial variants and anomalies. Conclusion Knowledge of such variants and anomalies is crucial to differentiate them from pathologies, to understand the etiology of certain pathologies directly related to variants, and to depict the changes in collateral circulation in patients with variants. Detection of variants may lead to the discovery of cerebrovascular diseases especially aneurysms, and may also affect planning of endovascular or neurosurgical interventions. This study is intended to serve as a guide for daily use in clinical practice. Disclosures S. Ahmad: None.