Effect of the wall thickness of the vessel on FFRCT of carotid artery stenosis

Abstract

Fractional flow reserve (FFR) computed from computed tomography angiography (CTA), i.e., FFRCT has been used in the clinic as a noninvasive parameter for functional assessment of coronary artery stenosis. It has also been suggested to be used in the assessment of carotid artery stenosis. The wall thickness of the vessel is an important parameter when establishing a fluid-structure coupling model of carotid stenosis. This work studies the effect of the vessel wall thickness on hemodynamic parameters such as FFRCT in carotid stenosis. Models of carotid stenosis are established based on CTA image data using computer-aided design software. It is assumed that the vessel wall is a linear elastic and isotropic material, and the blood an incompressible Newtonian fluid. Under the pulsating flow condition, ANSYS Transient Structural and CFX are used to simulate the blood flow of fluid-structure coupling in the carotid stenosis model in order to obtain hemodynamic parameters and the corresponding FFRCT. The results show that when the elastic modulus of the vessel wall is fixed, FFRCT will decrease with the increase of the wall thickness. Similarly, FFRCT will decrease with the increase of the elastic modulus when the wall thickness is fixed. The difference in hemodynamic parameters such as FFRCT, however, is relatively small if the stiffness of the two models are close. The results demonstrate that the effect of the vessel wall thickness, especially for a model with small elastic modulus, should be taken into account in using FFRCT for functional assessment of carotid stenosis. Moreover, under the linear elasticity and isotropic material assumptions, the stiffness coefficient may replace the elastic modulus and wall thickness as a parameter reflecting material property of the vessel wall in the carotid stenosis model.