Geometric versus hemodynamic indexes for rupture-destined aneurysms: a retrospective cohort and a repeated-measures study

Abstract Background and purpose A proper stratification of intracranial aneurysms (IA) is critical in identifying rupture-destined aneurysms (RDA) and unruptured intracranial aneurysms (UIA). We aimed to determine the utility of geometric and hemodynamic indexes in differentiating RDA and UIA, and to examine the characteristics of natural evolutionary changes of UIA. Methods RDA was defined as having subsequent subarachnoid hemorrhage (SAH), and UIA was examined using follow-up time-of-flight magnetic resonance angiography (TOF-MRA). In addition to geometric indexes such as aspect or size ratio, aneurysmal signal intensity gradient (SIG), an in-vivo approximated wall shear stress (WSS) from TOF-MRA, was measured. The difference (delta) between the maximum and minimum values of SIG in an aneurysm compared to parent arterial values was designated as the delta-SIG ratio. Results This study analyzed 20 RDA in 20 patients and 45 UIA in 41 patients with follow-up TOF-MRA. While geometric indexes did not show significant differences between the RDA and UIA, the delta-SIG ratio was significantly higher in the RDA than in the UIA (1.5±0.6 vs. 1.1±0.3, P=0.032). The delta-SIG ratio showed a significantly higher area under the receiver operating characteristics curve for SAH than the size ratio (0.72 [95% confidence interval (CI), 0.58–0.87] vs. 0.56 [95% CI, 0.41–0.72], P=0.033). The longitudinal re-examination of TOF-MRA in the UIA group showed evidence of aneurysmal growth with hemodynamic stability. Conclusions The delta-SIG ratio showed significantly higher discriminatory results between RDA and UIA compared to geometric indexes. Aneurysmal rupture risk should be assessed by considering both geometric and hemodynamic information. This study was registered on ClinicalTrials.gov ( NCT05450939 ).