title: 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: BACKGROUND
  The 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.
  
  
  METHODS
  In 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.
  
  
  RESULTS
  With 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.
  
  
  CONCLUSIONS
  Communicating 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.
authors.affiliation: School of Energy and Power Engineering, Xi'an Jiaotong University, 28 Xian Ning West Rd, Xi'an, 710049, Shaanxi, China. zhugy.xjtu@gmail.com.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Zhu
authors.affiliation: School of Energy and Power Engineering, Xi'an Jiaotong University, 28 Xian Ning West Rd, Xi'an, 710049, Shaanxi, China. qyuan@mail.xjtu.edu.cn.
authors.forename: Qi
authors.initials: Q
authors.lastname: Yuan
authors.affiliation: Department of Radiology and Medical Imaging, The First Affiliated Hospital of Xi'an Jiaotong University, 277 Yanta West Road, Xi'an, 710061, Shaanxi, China. yj1118@mail.xjtu.edu.cn.
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.affiliation: School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore, 639798, Singapore. mjhyeo@ntu.edu.sg.
authors.forename: Joon Hock
authors.initials: JH
authors.lastname: Yeo
mesh_terms: D001783:Blood Flow Velocity; D016893:Carotid Stenosis / Q000473:pathology* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D002941:Circle of Willis / Q000473:pathology* / Q000503:physiopathology*; D003198:Computer Simulation; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008955:Models, Cardiovascular; D066230:Patient-Specific Modeling; D012212:Rheology / Q000379:methods