BACKGROUND AND PURPOSE:Cerebral aneurysms are preferentially located at arterial curvatures and bifurcations that are exposed to major hemodynamic forces, increasingly implicated in the life cycle of aneurysms. By observing the natural history of aneurysm formation from its preaneurysm state, we aimed to examine the hemodynamic microenvironment related to aneurysm initiation at certain arterial segments later developing an aneurysm.
Aneurysm geometry does have an impact on flow conditions. Aneurysms with a main axis parallel to the parent artery have a tendency to have a jet flow pattern and uneven distribution of unsteady pressure. These aneurysms may have a higher rate of rupture as than those with a main axis perpendicular to the parent artery.
IntroductionAneurysms are dilated sections of blood vessels appearing at various locations of the cardiovascular system. These lesions may appear on the arteries supplying the brain, the cerebral circulation. Aneurysms that rupture on the cerebral arteries cause subarachnoid haemorrhage, a form of stroke, which may lead to the death or permanent disability of the patient. Studies show [1] that approximately 5% of the population develops an aneurysm, but only a fraction of these burst. Unfortunately the knowledge about the initiation, growth and rupture of cerebral aneurysms is limited even though research on the field is intense.It is a widely accepted view that hemodynamics is a key factor in these processes [2]. The studies whose aim is to understand the hemodynamics of cerebral aneurysms are most commonly based on numerical simulations. The flow inside vessels are usually assumed to be laminar, blood is treated as an incompressible, Newtonian liquid. With these assumptions advanced numerical solvers are able to calculate the flow accurately. The uncertainties of the results therefore mostly originate from the geometry, meshing and boundary conditions.Once a patient-specific image is acquired, the effect of slight geometrical uncertainties arising from reconstruction are found to be less dominant. Cebral et al. [3] found the calculated flow to be insensitive to slight geometrical variations. They compared results based on models derived from the same medical images by different persons. With the exception of one case, they found small differences. There the parent artery and the sac touched each other. The small geometrical uncertainties are the results of the image segmentation as it is based on the medical imaging technique. This in itself holds numerous uncertainties, which are beyond the scope of the present paper.Meshing is also a less critical factor. Advanced mesh generation codes that are part of numerical simulation packages are able to generate high quality meshes. These include the appropriate resolution near the vessel wall, which can be efficiently assured using prismatic elements. The effect of these grids on numerical accuracy can be well monitored with the help of mesh studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.