The role of the circle of Willis in internal carotid artery stenosis and anatomical variations: a computational study based on a patient-specific three-dimensional model

Abstract

BackgroundThe aim of this study is to provide better insights into the cerebral perfusion patterns and collateral mechanism of the circle of Willis (CoW) under anatomical and pathological variations.MethodsIn the current study, a patient-specific three-dimensional computational model of the CoW was reconstructed based on the computed tomography (CT) images. The Carreau model was applied to simulate the non-Newtonian property of blood. Flow distributions in five common anatomical variations coexisting with different degrees of stenosis in the right internal carotid artery (RICA) were investigated to obtain detailed flow information.ResultsWith the development of stenosis in unilateral internal carotid artery (ICA), the cerebral blood supply decreased when the degree of stenosis increased. The blood supply of the ipsilateral middle cerebral artery (MCA) was most affected by the stenosis of ICA. The anterior communicating artery (ACoA) and ipsilateral posterior communicating artery (PCoA) functioned as the important collateral circulation channels when unilateral stenosis occurred. The blood flow of the anterior circulation and the total cerebral blood flow (CBF) reached to the minimum in the configuration of the contralateral proximal anterior cerebral artery (A1) absence coexisting with unilateral ICA stenosis.ConclusionsCommunicating arteries provided important collateral channels in the complete CoW when stenosis in unilateral ICA occurred. The cross-flow in the ACoA is a sensitive indicator of the morphological change of the ICA. The collateral function of the PCoA on the affected side will not be fully activated until a severe stenosis occurred in unilateral ICA. The absence of unilateral A1 coexisting with the stenosis in the contralateral ICA could be the most dangerous configuration in terms of the total cerebral blood supply. The findings of this study would enhance the understanding of the collateral mechanism of the CoW under different anatomical variations.

State-of-the-Art Computational Models of Circle of Willis With Physiological Applications: A Review

“…An idealized model could be a simple one based on limited geometric parameters [47], a local 3D geometry coupled with 0D artery tree at inlet and outlets [48], or a structure rebuilt from the in-vitro model [49,50]. More patient-specifically, some idealized models were reconstructed from the central lines extracted from the clinical imaging of intracranial arteries [51][52][53] or an intact arterial structure starting from the aorta [5], or derived from changing the topology of CoW reconstructed from patientspecific CT images [54]. In-vivo geometric models were reconstructed exactly from the patient-specific imaging data.…”

Impacts of Internal Carotid Artery Revascularization on Flow in Anterior Communicating Artery Aneurysm: A Preliminary Multiscale Numerical Investigation

“…The ACoAA is a vital collateral pathway of the circle of Willis as well as a preferential site of the IA [42]. Inter-hemispheric blood flow through the ACoAA and the reversed blood supply in the ACA-A1 provided critical collateral blood supply to the anterior cerebral circulation when unilateral ICA stenosis occurred [24,43]. Our previous studies have shown that in the situation of PCoA absence, the collateral flow in ACoAA changes non-linearly with the unilateral ICA stenosis degree due to the collateral mechanism [24,25].…”

“…Inter-hemispheric blood flow through the ACoAA and the reversed blood supply in the ACA-A1 provided critical collateral blood supply to the anterior cerebral circulation when unilateral ICA stenosis occurred [24,43]. Our previous studies have shown that in the situation of PCoA absence, the collateral flow in ACoAA changes non-linearly with the unilateral ICA stenosis degree due to the collateral mechanism [24,25]. Therefore, instead of considering the region of UIAs alone in the computational domain [44][45][46], modeling the whole anterior circulation would be more appropriate to provide better insight into the hemodynamics change in ACoAA during ICA revascularization.…”

“…In literature, both steady and pulsatile volumetric flow rates were usually defined as inlet BC [47]. Although the steady-state simulations were regarded as a quick alternative to transient simulations in the previous study [24,48], their incapability of providing temporal hemodynamic parameters limited their applications. Hence, transient simulations were adopted in this study, and the physiological volumetric ICA flow profiles from a 4D-MRI of a healthy patient were imposed at the afferents of the non-stenotic post-operative computational model.…”

“…ACoAA accounts for nearly 25% of IAs [23]. Moreover, the unilateral ICA stenosis could drastically influence the local hemodynamics characteristics in the ACoAA [24,25]. Thus, the understanding of hemodynamics consequences of ICA revascularization on ACoAA would benefit the management of patients concurrent ACoAA and unilateral stenosis.…”