MRA-based aneurysm occlusion assessment in the early phase after flow diverter treatment: a multicenter retrospective study focusing on the impact of aneurysm diameter

BACKGROUND: Although it is well-known that most aneurysms occlude within 1 year after flow diverter (FD) treatment, the time course to occlusion, especially in the early period, has not been adequately studied. METHODS: This study included patients treated with FDs between April 2018 and December 2024 and underwent at least 3 months of imaging follow-up with MRA. The primary outcome was aneurysm occlusion without rupture during follow-up. Cumulative aneurysm occlusion rates were assessed using repetitive time-of-flight and ultrashort echo-time MRA. Predictors of aneurysm occlusion were analyzed with special interests to patient backgrounds, anatomical factors including aneurysm diameter, and procedural details. RESULTS: This study included 119 patients (male: female ratio, 15:104; mean age, 58 ± 14 years; average diameter, 10.8 mm). During the median follow-up of 12 months, the cumulative occlusion rates at 3, 6, and 12 months were 15%, 48%, and 79%, respectively. Receiver operating characteristic analysis identified the diameter threshold of 10.9 mm to best predict its occlusion, and aneurysms larger than this cutoff showed lower cumulative occlusion rates (P = 0.002 [log-rank test], hazard ratio 0.49 [P = 0.003]). In the multivariable Cox hazard model, an increase in aneurysm diameter (Hazard ratio 0.92, P = 0.002) was a preventive factor for aneurysm occlusion, whereas adjunctive coiling (Hazard ratio 2.05, P = 0.009) significantly promoted the occlusion rate. CONCLUSIONS: In postoperative follow-up using repetitive MRA, larger aneurysms exhibited the trend to occlude slower after FD treatment, whereas adjunctive coiling promoted the time course to aneurysm occlusion. Future prospective studies are warranted to investigate technical factors to further promote aneurysm occlusion. CLINICAL TRIAL NUMBER: UMIN000057450.