Investigation of Contrast Retention in PCOM Aneurysms as a Possible Marker for Instability and Rupture

Identification of cerebral aneurysms at risk of destabilization and rupture remains challenging. Although flow stagnation has been recognized as a risk factor, the underlying mechanisms and its predictive power are poorly understood. The purpose was to investigate possible associations between flow stagnation determined from computational fluid dynamics (CFD)-based virtual angiograms and aneurysm instability and rupture. A total of 312 aneurysms at the posterior communicating (PCOM) artery were analyzed with image-based CFD. Virtual angiograms were constructed by simulating contrast injections, and contrast retention metrics were calculated from time density curves of the aneurysm and their parent artery. These metrics were compared between 23 stable and 18 unstable aneurysms from a longitudinal dataset and between 129 unruptured and 142 ruptured aneurysms from a cross-sectional dataset. Aneurysmal contrast retention was significantly larger (p < 0.05) in ruptured compared to unruptured aneurysms as well as when considering only small aneurysms (size < 7 mm). Similar associations were obtained when comparing stable and growing aneurysms. Multivariate analysis showed that aneurysm instability can be forecasted from flow stagnation with good accuracy (AUC = 0.88), while aneurysm rupture with only moderate accuracy (AUC = 0.72) or marginal accuracy for small aneurysms (AUC = 0.66). Mean residence time was identified as a good predictor of aneurysm instability and rupture. Flow stagnation, determined by contrast retention in angiographies (virtual or real), is associated with PCOM aneurysm instability (growth or symptoms development) and can be used to identify aneurysms prone to further growth and potentially rupture. However, aneurysms can also rupture without exhibiting signs of flow stagnation.