A Study Of The Collateral Capacity Of Circle Of Willis Based On CFD Simulation

The Circle of Willis (CoW) is the most important collateral pathway of the cerebral artery, which has the fundamental significance in balancing blood supply between the two cerebral hemispheres, preventing stroke and improving prognosis. Unfortunately, no more than 50% of the general population has a complete CoW. The primary purpose of this paper is to assess the collateral capacity of CoW with anatomical variation in the posterior circulation when unilateral internal carotid artery (ICA) is occluded. Besides, the reconstruction of patient-specific model is based on different imaging modalities when studying the hemodynamics. Therefore, another purpose of this paper is to compare the models derived from different medical imaging technology in modelling of the intracranial aneurysm.In the comparative research,3DRA based model (DM) were treated as the "standard models", CTA based models (CM) and MRA based models (MM) were compared with the "standard model" in morphology, hemodynamics and flow characteristics, respectively. The results demonstrated that both CM and MM had no obvious difference in reproducing the aneurysmal geometry when comparing DM. However, the difference of hemodynamic parameters are relative large. Besides, compared with DM, both of CM and MM have a good agreement in assessing the flow characteristics.Due to the limitation of materials, the study of the collateral capacity was based on idealized models. First of all, eight 3D models were reconstructed based on different anatomical variation in the posterior circulation of CoW. Subsequently, a stenosis with different degrees was simulated in the right ICA, namely 24%,43%,640 and 79%, respectively. Finally, a total of 40 models were performed with computational fluid dynamics simulations. All of the simulations shared the same boundary conditions with static pressure and the volume flow rate (VFR) which were obtained to evaluate their collateral capacity. As for the middle cerebral artery (MCA) and the anterior cerebral artery (ACA), the transitional-type model possessed the best collateral capacity. But for the posterior cerebral artery (PCA), unilateral stenosis of ICA had the weakest influence on the unilateral posterior communicating artery (PCoA) absent model. We also found that the full fetal-type posterior circle of Willis was an utmost dangerous variation which should be paid more attention.The comparison of the patient-specific models derived from different imaging modalities may help the researchers choose medical imaging in the study of hemodynamics. Moreover, this study of the collateral capacity of CoW with anatomical variation in the posterior circulation in coping with unilateral ICA occluded may help neurosurgeons select the best treatment strategy and assess operation risk.