Abstract
Blood-flow patterns and wall shear stress (WSS) are assumed to play a major role in development and rupture of cerebral aneurysms. To date, these hemodynamic aspects have been extensively studied in-vitro using geometric realistic aneurysm models. The purpose of this study was to evaluate the feasibility of in-vivo flow-sensitized 4D MR imaging for the visualization and quantification of intra-aneurismal hemodynamics. 5 cerebral aneurysms, differing in size, shape and location, were examined using flow-sensitized 4D MR imaging at 3T in 3 patients. 3D postprocessing was performed with a dedicated, commercially available, software package combined with an in-house software tool. This included quantification of flow-velocities, visualization of time-resolved 2D vector graphs and 3D particle traces, vortex core localization, and WSS estimations from 3D velocity fields. Flow patterns were analyzed in relation to aneurysm geometry and aspect ratio (aneurysm depth/neck width). Strength, spatial and temporal evolution of vortical flow patterns differed markedly among all aneurysms. Particularly unstable vortical flow was demonstrated in a wide-necked parophthalmic ICA aneurysm (high aspect ratio). Relatively stable vortical flow was observed in aneurysms with lower aspect ratio. Except for a wide-necked cavernous ICA aneurysm (low aspect ratio), WSS was reduced in all aneurysms relative to the parent artery and showed a high spatial variation. In conclusion, in-vivo flow-sensitized 4D MR imaging can be applied to visualize and quantify blood flow patterns and to estimate WSS inside cerebral aneurysms. Flow patterns, distribution of flow velocities, and WSS seem to be determined by the vascular geometry of the aneurysm.
