Introduction: Recent studies have strongly associated intracranial aneurysm growth with increased risk of rupture. To plan more effective monitoring and intervention strategies, it would be beneficial to identify aneurysms which are likely to grow.
Hypothesis: Morphological characteristics at initial diagnosis differ between unruptured intracranial aneurysms that will grow and those that are stable.
Methods: A total of 58 cases of aneurysms in our medical center with follow-up imaging dates in 2015 were selected. All CTA images for the aneurysms were collected, for a total of 250 image sets. Aneurysm 3D geometry was reconstructed and morphological characteristics, including volume, surface area, and non-sphericity index (NSI) were calculated. NSI was calculated as 1 - (18π)1/3 V2/3/S, where V and S represent aneurysm volume and surface area, respectively. Statistical comparisons were made using a two-tailed t-test with an assumption of unequal variance (Welch’s t-test).
Results: Aneurysms were followed for an average of 50.5±50.9 months, with an average of 3.29±2.66 follow-up imaging dates. 9 aneurysms exhibited a size increase (>0.6mm) and the remaining 49 aneurysms did not. Based on their maximum diameter, no significant difference was found between initial aneurysm size between the growth (3.80±1.72 mm) and non-growth (4.26±2.00 mm) groups (p=0.13). Likewise, no significant differences in volume or surface area were found (p=0.33, p=0.36, respectively). However, initial NSI was found to be significantly higher in the growth (0.32±0.11) vs. the non-growth (0.23±0.08) group (p=0.049).
Conclusions: Among aneurysms with similar size, NSI may be useful for identifying aneurysms which are more likely to grow and planning monitoring strategies accordingly. Higher initial NSI in the aneurysms which eventually grew is consistent with previous findings that higher NSI correlates with increased risk of rupture.