Numerical investigation of perfusion rates in the circle of Willis in different anatomical variations and ischemic stroke

Abstract

The circle of Willis (CoW) is a set of arteries located in the basis of the brain. Prediction of perfusion rates and hemodynamics in the CoW is necessary to understand the relevant vascular diseases and to prescribe effective treatments. In this paper, the effect of ischemic stroke in the CoW is studied, taking into consideration the anatomical variations of the CoW. Moreover, an analysis on the effect of applied boundary conditions is carried out. To do so, a patient-specific model of the CoW is reconstructed from CT (computed tomography) images. Six different cases of boundary conditions are applied to complete and healthy CoW, and the flow rates are investigated. The proper pressure boundary conditions are then imposed to three other variations of the CoW, and the flow rates are compared. The results reveal that the overall inlet flow rate varies from 1.75% to 7.5% in three variations of healthy CoW. Moreover, the changes in flow rates of outlet and inlet branches are indicated in ischemic stroke by considering a spherical clot in the right middle cerebral artery (RMCA). In this case, the RMCA flow reduced by 88.4%, and the internal carotid artery flow decreased by 53.6%. These changes lead to increased flow rates of other inlets to support the brain; however, the overall inlet flow rate falls by 21.5%.