Rupture risk assessment of human intracranial aneurysms: Morphological and hemodynamic characterization
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This study was aimed at identifying both morphological and hemodynamic parameters that can effectively characterize a human intracranial aneurysm (IA) that is prone to rupture and separate it from aneurysms that are likely to remain unruptured. Among the patients who suffer from a sub- arachnoid hemorrhage (bleeding resulting from rupture of an intracranial aneurysm) 50% die from the initial hemorrhage and 20-25% are maimed. The study was inspired by the fact that only 1% of all aneurysms will, in fact, rupture and that the treatment of such aneurysms also entail considerable risk to the person affected. Thus, effective methods to separate the rupture prone aneurysms from the others will spare many patients the ordeal of a surgical procedure while identifying the aneurysms that need aggressive treatment. The first part of the study was to identify relevant morphological metrics. For 45 patients with terminal or sidewall saccular IAs (25 unruptured, 20 ruptured), 3D geometries were evaluated for a range of morphological parameters. Detailed statistical analyses of the metrics were performed and Size Ratio and Aneurysm Angle were identified as promising new morphological metrics for IA rupture risk assessment. The second part of the study was aimed at further elucidating the role that Size Ratio plays in governing intra-aneurysmal hemodynamics. Low WSS and complex flow patterns with multiple vortices have been previously demonstrated as characteristic of ruptured IAs. This study found that, higher Size Ratio, irrespective of absolute aneurysm size or vessel diameter, gives rise to characteristic flow patterns observed in ruptured IA. This indicates that Size Ratio, not aneurysm size, more closely captures IA hemodynamics, and may thus better predict rupture risk.