Introduction: Atherosclerotic intracranial arterial stenosis (IAS) is a significant cause of ischemic stroke. Despite studies identifying degree-of-stenosis, prior symptoms, and gender as predictors of recurrent stroke or death, the mechanisms of artery-to-artery embolisms and hypoperfusion remain largely unexplored. Particularly, the hemodynamic factors, such as wall shear stress (WSS), local turbulent kinetic energy (TKE), flow velocity and pressure gradients have not been studied.
Methods: We developed a 3D computational model of the cerebrovascular anatomy in regions commonly affected by IAS. The first step was to extract the vascular anatomy from a biplane angiogram using 2D-to-3D reconstruction of semi-automatically delineated vessel branches to obtain the basic geometry of the middle cerebral artery (MCA). Next, lenticulostriates (LSAs) were added, which are beyond the resolution of the angiographically generated model. The model was manipulated to reproduce stenoses of varying degree. A volumetric mesh was then generated with more than 2 million tetrahedral cells and used to evaluate hemodynamic parameters at 0%, 70% and 90% stenosis using the ANSYS: Simulation Technology package.
Results: In the baseline model, flow velocity throughout the MCA was laminar and consistent flow was seen through the lenticulostriates (Figure 1A). Mean velocity was 0.53m/s and WSS and TKE were unremarkable (0.629Pa, 2.3E-4J/kg). In 70% and 90% stenosis models there was elevated velocity (4.7m/s, 3.3m/s) (Figure 1B&C) and WSS (14.42Pa, 27.96Pa) through the stenosis. At 70% stenosis, distal velocity was higher than for 90% (0.445m/s, 0.054m/s). Turbulent flow was present just distal to the 70% stenosis (TKE=0.014J/kg) and within the 90% stenosis (0.014J/kg).
Conclusions: A computerized 3D model of the cerebral vasculature based on patient images can reproduce changes in hemodynamic parameters that could influence the development and progression of IAS. Detailed hemodynamic factors associated with the location, length, degree and morphology of the plaque should be considered in evaluation of patients with IAS.
Patient Care: This research provides a computational model that can be used as a foundation upon which to further investigate the hemodynamic changes of intracranial arterial stenosis and other cerebrovascular disorders
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Understand the hemodynamic changes caused by intracranial arterial stenosis, and 2) Discuss other cerebrovascular pathologies that could be investigated with the use of a computational model