Hemodynamics of intracranial saccular aneurysms.

摘要

Cerebral aneurysms result from the abnormal dilatation of one of the large blood vessels that supply the brain. They pose a health risk from the potential for rupture and subsequent bleeding into the brain and/or the subarachnoid space.; The generation, growth and rupture (natural history) of cerebral aneurysms are the result of a complex interplay between pathological processes and mechanical stimuli. The aim of this study is twofold. The first is to investigate the role of the hemodynamic forces in the growth and eventual rupture of intracranial aneurysms, while the second is to conduct a comprehensive analysis of the performance of different endovascular treatment techniques and to determine, from a mechanical point of view, their efficiency in preventing aneurysmal growth and rupture. For this purpose a Digital Particle Image Velocimetry (DPIV) technique is used to measure the pulsatile blood velocity field at the entrance and inside aneurysm silicon models. A programmable pulsatile pump is used to emulate the waveform corresponding to the flow in the carotid artery. In order to reproduce the compliance of the arterial wall, silicone models are made from anatomically correct molds. Since most cerebral aneurysms appear at either curved or bifurcating arteries, the arterial models were chosen to represent these two geometries.; The results of this study show that the presence of the aneurysm and its growth lead to the enhancement of the secondary motions induced in bifurcating and curved vessels, due to the strong, three-dimensional vortex created in the aneurysmal sac. In addition, it has been shown that the inertia imparted to the vortex during systole sustains the rotational motion throughout the whole cardiac cycle. This persistent flow inside the aneurysmal sac prevents the formation of a thrombus that could potentially fill the sac, reducing the mechanical stresses on the arterial wall and, thus, stopping the growth. All the endovascular treatment techniques analyzed in this study have shown to effectively reduce the flow entering the aneurysmal sac, thereby reducing the wall shear stresses acting on the neck of the aneurysm which are believed to be responsible for the aneurysmal growth.