Evaluating How Circle of Willis Topology Affects Embolus Distribution in the Brain

Embolic stroke occurs when fragmented cellular or acellular material (emboli) travels to the brain to occlude an artery. Understanding the transport of emboli across unsteady, pulsatile flow in complex arterial geometries is challenging and influenced by a range of factors, including patient anatomy. The work herein develops the modeling and mechanistic understanding of how embolus transport is affected by the arterial connections at the base of the brain known as the Circle of Willis (CoW). A majority of the human population has an incomplete CoW anatomy, with connections either missing or ill-developed. We employ numerical simulations combining image-based modeling, computational fluid dynamics, discrete particle dynamics, and a sampling based analysis to compare collateral flow through the most prevalent CoW topologies, to determine embolus distribution fractions among vessels in the CoW, and to investigate the role of inertial effects in causing differences in flow and embolus distribution. The computational framework developed enables characterization of the complex interplay of anatomy, hemodynamics, and embolus properties in the context of embolic stroke as well as statistical analysis of embolism risks across common CoW variations.