Interdependence of First-coil and Global volume embolization ratios (VERs) calculated by Sim&Size in predicting aneurysm occlusion outcomes

Background Coil embolization is a standard therapeutic approach for intracranial aneurysms. Recurrence risk during follow-up is not negligible, with inadequate packing density identified as a potential risk factor. This study aims to identify patient- and procedure-related factors contributing to recurrence. Methods We retrospectively enrolled consecutive patients with unruptured intracranial aneurysms treated only with coils between January 2021 and December 2022. Aneurysms were included if 3D-rotational angiography and follow-up imaging were available. For each patient, the volume embolization ratio (VER) was computed using Sim&Size ® (Sim&Cure, France) for both the framing coil (First-coil VER) and the entire coiling procedure (Global VER). Patient demographics and aneurysm characteristics were also recorded. Follow-up imaging classified patients into adequate- or inadequate-occlusion groups. Multivariate analyses assessed independent factors associated with recurrence. Results Seventy-nine unruptured aneurysms from 79 patients were included. At follow-up, n = 69 (87%) demonstrated adequate occlusion, defined as modified Raymond-Roy classification I-II. Adequate- and inadequate-occlusion groups differed in First-coil (13.5 ± 5.5% vs 7.1 ± 4.0% respectively, P = .002) and Global VER (24.5 ± 6.8% vs 17.3 ± 5.7% respectively, P = .004). Posterior aneurysm location ( P = .013), aneurysm height ( P = .007), and neck diameter ( P = .018) were significantly associated with recurrence. In multivariate analysis, Global- ( P = .029) and First-coil VER ( P = .025) remained significant risk factors for recurrence, with their interaction term being statistically significant as well ( P = .020). Conclusions First-coil and Global VER computed using Sim&Size ® are predictive of aneurysm occlusion at follow-up. These results highlight the potential value of virtual simulation in optimizing coil packing density to improve mid- to long-term occlusion outcomes.