Blood Flow in the Common Carotid Artery With Stenosis

Abstract

This work presents the development of a computational methodology based on ultrasound (US) data and able to simulate the hemodynamics of a carotid bifurcation with stenosis. A semi-automatic lumen segmentation methodology of longitudinal and cross-sectional images is presented. The algorithm, implemented in Matlab is based on the hypoecogenic characteristic of the lumen and allows the lumen contour extraction in 2D B-mode images. Patient-specific Womersley velocity profiles, derived from the pulsatile velocity waveforms obtained by pulsed Doppler images, were considered for the definition of the boundary conditions. An image based computational fluid dynamics model of a middle-aged patient was reconstructed from both segmented transversal and longitudinal US images. The blood flow simulation was performed using the Ansys/Fluent software. Pulsatile conditions of the hemodynamic analysis were validated by the carotid US scan. Hemodynamic analysis was performed based on wall shear stress (WSS) descriptors. High values of time-averaged wall shear stress (TAWSS) were captured within stenosis. Low values of TAWSS where found at the carotid bulb, upstream and downstream stenosis and also at external carotid artery. In these regions the oscillatory shear index (OSI) and the relative residence time (RRT) present high values, in agreement with the fact these hemodynamic descriptors are able to capture abnormal flow conditions witch present an import role in the local development of atherosclerotic plaques. This study shows to be clinically useful in the diagnosis and management of the treatment of carotid stenosis as it is able to show a complex hemodynamic behaviour during the cardiac cycle allowing the correlation between the carotid wall pathophysiology and the local influence in artery hemodynamics.