Patient-Specific Modeling of Cerebral Aneurysms Hemodynamics: Comparisons of CFD, in vitro, and in vivo 4D Flow MRI

Flow metrics influencing cerebral aneurysm stability can be evaluated using modeling (numerical or experimental) or 4D flow MRI. Modeling has high spatiotemporal resolution but relies on assumptions, e.g. boundary conditions and wall compliance. 4D flow, while measuring velocities in vivo, has limited resolution and dynamic range. Our goal is to use high resolution modeling to detect flow features not resolved by imaging. In vitro 4D flow and CFD studies were conducted in two cerebral aneurysm models constructed from MR data acquired at Northwestern University and UCSF. Patient-specific geometries were generated using 3D printing and silicon casting. The models’ Reynolds and Womersley numbers matched those of the in vivo blood flow. Computations were run using FLUENT solver with boundary conditions obtained from in vivo measurements. Spatial and temporal resolution of CFD was 150 um and 1.5 ms, respectively. Preliminary results did not show a consistent over- or underestimation of the CFD velocities relative to in vivo measurements. Qualitative agreement of the dominant flow features was found across the modalities, however CFD revealed small flow structures in the near-wall regions which in vivo 4D flow could not detect.