Hemodynamics in Cerebral Arteries and Aneurysms

Cerebral aneurysms develop in about 4 % of western§populations and involve the risk of rupture. Blood§flow patterns are of interest for understanding the§pathogenesis of the lesions for a specific patient.§Velocity mapping with phase-contrast magnetic§resonance angiography (PC-MRA) is a non-invasive§method for in vivo measurements on blood velocity.§Based on these, a realistic patient-specific computer§model can be generated and the flow field with all§hemodynamic parameters can be simulated. As the§accuracy of the PC-MRA data and subsequent modeling§must be validated, a realistic flow field in a§silicone phantom was investigated. Velocities were§acquired under equal conditions with PC-MRA, laser§Doppler velocimetry (LDV) and computational fluid§dynamics (CFD). The results showed that PC-MRA was§qualitatively, but not quantitatively, similar to LDV§and CFD in straight arteries, while the accuracy of§PC-MRA decreased in regions with complex flow§patterns as present in aneurysms. Thus, it is§appropriate to use PC-MRA as inlet conditions for CFD§to calculate hemodynamic parameters in aneurysms,§rather than to derive them directly from the§measurements.