Parametric geometry definition and analysis of the human carotid artery bifurcation

Three-dimensional parametric computer aided design (CAD) geometry definitions of the human carotid artery bifurcation are presented for both Y-shaped and tuning-fork models. Drawing on methods largely developed in aerodynamic design, these parametric CAD geometries are deployed within a response surface methodology to systematically map the variation of spatially integrated mean shear stress with the angles of the internal carotid artery (ICA) and the external carotid artery (ECA). Although the absolute values of this shear stress metric agree in some regions of the design space, significant differences exist in the shapes of the response surfaces for the alternative CAD models. The tuning-fork data reveals unexpected results in the location of the lowest value of the metric (at large ICA angles and small ECA angles) and also in the presence of two regions of high metric values - one, unsurprisingly, at large ICA and ECA angles but another exists close to the baseline geometry at the centre of the design space. In contrast, the Y-shaped data is such that a very spiky response surface is produced dominated by changes in the ICA angle. Also, the minimum is located at small ICA and large ECA angles. Finally, evidence is presented for strong recirculation at the outflow of the sinus bulb for small ICA angles that is nonexistent for large ICA angles