Hemodynamic analysis of carotid siphon with unilateral stenosis: Significance of arterial geometry

Geometry of arteries has been considered as an important risk factor for atherosclerosis, because it influences the local hemodynamics. But the effect of the arterial shape on the internal carotid arterial (ICA) stenosis remains unknown. Four subjects with two geometrically different ICAs, diagnosed with unilateral stenosis, were investigated to clarify the association between the ICA shape and the stenosis. Magnetic resonance angiography (MRA) images of the two branches of ICA were acquired from the subject, and reconstructed into 3D models. The bifurcations and taper of the ICAs were removed. The pulsatile flow in the models was computationally simulated to evaluate the effect of the arterial geometry on hemodynamics. Because of the different geometry between the two branches of ICAs, the hemodynamic pattern is obviously different. The wall shear stress gradient (WSSG) and oscillating shear index (OSI) is lower in the left ICA branches, where helical flow is found, because of the large nonplanarity of bends. The difference of the arterial geometry is probably the only reason for the stenosis in this study. Furthermore, the planarity of the carotid siphon is the only geometric factor that is significantly different between the two branches. Consequently, the planarity is considered as the most important geometric factor for stenosis in ICAs.