In this study, we reviewed 181 patients with 230 unruptured cerebral aneurysms who underwent initial coil embolization at a single institution between 2011 and 2021. We excluded 27 patients with occlusion of the mother vessel, 15 patients who underwent flow-diverter implantation, six patients with thrombosed aneurysms, and one patient who was lost during follow-up. We retrospectively analyzed the correlation between neck width, maximum aneurysm size, width, aneurysm volume, 1st VER, and final VER of the cerebral aneurysm and recanalization requiring retreatment. Aneurysm volume was measured using a partially automated three-dimensional workstation (Allura 3D-RA workstation, Philips Medical Systems) from the rotational angiography data. The volume of the coils was defined as π (P/2)2 times the coil length, where p is the diameter of the primary coil. Final and 1st VERs were calculated according to the following equations:
1st VER = (the first coil volume)/(the aneurysm volume) × 100 Final VER = (total volume of all inserted coils)/(aneurysm volume) × 100