Abstract TP292: Quantitative assessment of parent artery curvature and aneurysm projection as predictors of aneurysm occlusion after flow diverter treatment

Background: In cerebral aneurysm treatment with flow diverters (FDs), parent artery curvature and aneurysm projection may affect procedural complexity and occlusion outcomes. However, standardized quantitative metrics are lacking. This study aimed to develop and validate an objective measurement method using an angiography workstation and to assess its association with aneurysm occlusion. Methods: We retrospectively analyzed preoperative three-dimensional rotational angiography in patients treated with FDs for unruptured internal carotid artery aneurysms between 2017 and 2024. Using a vessel analysis mode of SmartCT (Philips, Amsterdam), a centerline was automatically generated along the parent artery. Point N was defined at the aneurysm neck, with points P and D located 10 mm proximal and distal to N. The aneurysm tip (T) was the furthest point from N on the aneurysm outline. Two indices were calculated: the curvature ratio (C ratio), defined as 20 mm divided by the 3D linear distance PD, indicating vessel tortuosity; and the projection angle (P angle), defined as angle TNP in the plane containing P and D, indicating aneurysm projection. Two examiners independently measured these indices, with inter-rater reliability assessed in 13 randomly selected cases. Aneurysm occlusion was evaluated at 6 months post-treatment; O’Kelly–Marotta grades C/D were classified as good occlusion and A/B as poor. Results: Forty-nine cases were analyzed (mean age, 64.9 years; mean dome diameter, 12.8 mm; mean neck diameter, 7.6 mm). Inter-rater agreement was excellent for both C ratio (r = 0.99) and P angle (r = 0.93). The C ratio was not significantly associated with occlusion but correlated negatively with neck diameter (r = –0.36; p = 0.01). The P angle was significantly lower in good versus poor occlusion cases (81.1° vs. 127.1°, p < 0.01). Multivariate analysis identified the P angle as an independent predictor of good occlusion (odds ratio, 0.97; p = 0.04). Conclusion: This method enables quantitative assessment of parent artery tortuosity and aneurysm projection. The P angle, in particular, appears to be a useful predictor of 6-month occlusion following FD placement.