The pathogenesis of cerebral aneurysms is significantly influenced by the local hemodynamic environment; successful treatment must favorably modify this environment to promote thrombotic aneurysm occlusion and healthy arterial remodeling. It has been observed clinically that most cerebral aneurysms arise from areas subjected to increased hemodynamic forces, that is, at the apex of arterial bifurcations or on the curve of tortuous vessels (Fig. 1), rather than along straight vessel segments.27 Geometric parameters, such as aneurysm volume, shape, aspect ratio, and dome-to-neck ratio, have been studied extensively;9,15,25,35 however, little information characterizing the relation of the local vessel and aneurysm geometry to these elevated hemodynamic forces is available.6,19,24
In this study we begin the process of quantifying the poorly understood hemodynamic effects resulting from the complex 3D geometry of the local vessel. The first step undertaken was to quantify the relationship between hemodynamic forces and arterial curvature in an attempt to establish further correlations for the effect of arterial geometry on aneurysm growth and treatment.
Computational fluid dynamics is a computer simulation method that can be used to model the complex in vivo flow field associated with cerebral aneurysms. A time-dependent, space-resolved, 3D flow velocity field in anatomically realistic cerebral aneurysm models can be obtained from CFD simulations. Using the flexibility of CFD, the parameters of fluid dynamics and the blood particle paths can then be directly calculated and visualized. Furthermore, CFD can be used to predict the success or failure of interventional therapies that rely on altering the dynamics of blood flow within the aneurysm sac.
A better understanding of the relationship between the pathophysiological aspects of an aneurysm and its arterial geometry or local hemodynamics is critical to understanding aneurysm growth, predicting the risk of regrowth after treatment, and improving endovascular treatments. Our objective in this study was to examine the effects of local vessel curvature and aneurysm neck size on the hemodynamics of an aneurysm and, using a CFD analysis, to correlate these parameters with aneurysm growth and potential treatment effectiveness.
We thank Balazs Nemes, M.D., Stephen Rudin, Ph.D., and Kenneth Hoffmann, Ph.D., for helpful discussions and critiques of this manuscript.
This study was supported by grants from Toshiba America, the Oishei Foundation, and the Cummings Foundation (L.N.H.)