ANALYZING THE ROLE OF MORPHOLOGY ON THE ANEURYSMAL FLOW COMPLEXITY VIA DYNAMIC MODE DECOMPOSITION
PRESENTING AUTHORS FULL NAME: Trung Bao Le
INSTITUTION: North Dakota State University
BACKGROUND/PURPOSE: Flow in brain aneurysms is characterized by the formation of coherent structures. Our previous works (Le et al., J. Biomech. Engr. 2010, Le et al., Annals. Biomed. Engr. 2013) have shown that there exists a formation of a distinct vortex ring inside aneurysm cavity. The existence of this vortex ring can lead to large variabilities in spatial and temporal evolution of the Wall Shear Stress on the distal wall. While the role of pulsatility has been indicated as the decisive factor for this formation, it is not clear how arterial curvature can regulate the evolution of this vortex ring. Our main hypothesis is that the torsion of the parent artery can promote or suppress the evolution of vortex ring in sidewall aneurysms at Internal Carotid Arteries (ICA).
METHOD: Four ICA aneurysm geometries are reconstructed from the patient dataset of Sanford Health (Fargo, North Dakota) using DICOM images. The original (healthy) arterial geometries are reconstructed by virtual removal of aneurysms using the open-source software Meshlab and MeshMixer. We use the sharp-interface immersed boundary method (Ge and Sotiropoulos, JCP, 2007) as the flow solver. Structured meshes with the total number of grid points in the order of 20 millions are generated using the commercial software Gridgen. High resolution simulations are performed under pulsatile condition to compare flow characteristics with and without aneurysm cavity. Dynamic Mode Decomposition is carried out to analyze the dominating flow modes and quantify flow complexity in the two scenarios with and without aneurysm cavity.
RESULTS: The simulations show the formation of complex coherent structures in both aneurysm cavity and the boundary layer of the Internal Carotid Arteries. The interaction of the vortex ring and the boundary layer gives rise to the emergence of a well-mixed region intermittently inside the aneurysmal dome. Our results show a strong impact of tortuousness on flow complexity by mediating the growth of boundary layer.
CONCLUSION: Our results emphasize that tortuousness can be used as a surrogate measure to predict flow complexity. Our results can be used to infer in-vivo measurement modalities such as 4D-Flow MRI and help devise medical intervention given flow characteristics.