MODELING OF FLOW THROUGH THE CIRCLE OF WILLIS AND CEREBRAL VASCULATURE TO ASSESS THE EFFECTS OF CHANGES IN THE PERIPHERAL SMALL CEREBRAL VASCULATURE ON THE INFLOWS

The cerebral hemodynamics through the Circle of Willis (CoW) was modeled by coupling a three-dimensional (3D) Computational Fluid Dynamics (CFD) model of the CoW with a one-dimensional (1D) branching tree model of the peripheral cerebral vasculature. CFD was used to model the 3D transient flow through idealized and patient-specific CoW geometries. A 1D pipe network model was also used to predict the flow through the idealized CoW. The coupled model provided useful insight into the variation of the flow through the CoW as a result of possible physiological and pathological changes (for example associated with 'onset' of Alzheimer's Disease) in the peripheral networks of small cerebral vasculature. A comparison was made between the complete CoW and geometric variations with communicating arteries missing. A CoW inflow ratio showed that vasoconstriction of the peripheral vasculature of the posterior cerebral artery predominantly decreases the flow rate in the vertebral arteries, while vasoconstriction of the peripheral vasculature of the anterior and middle cerebral arteries predominantly decreases the flow rate of the internal carotid arteries. These changes in inflow in arteries that are easily monitored may be used to determine if there is vasoconstriction of the peripheral small cerebral vasculature which may indicate diseased states.