Endovascular Coil Embolization of Very Small Intracranial Aneurysms proportion of unruptured aneurysms. MATERIALS AND METHODS Patients Between March 2005 and December 2008, a total of 810 aneurysms were treated by either coil embolization or surgery at our institution. Of the 468 aneurysms treated by surgery, 142 (30%) were very small (≤ 3 mm) and of these, 40 (28%) were ruptured aneurysms. Whereas, of the 342 aneurysms treated by coil embolization, 31 (9%) in 30 patients were very small and five of them were ruptured (16%). Thus, we enrolled these 31 very small aneurysms from the 30 patients for this study. The 30 patients consisted of 11 males (37%) and 19 females (63%) with a mean age of 51.1 years (median, 52 years; range, 28-81 years). The Hunt and Hess (HH) Grade of the five patients who had presented ruptured aneurysms before endovascular treatment included one Grade IV, two Grade II, and two Grade I patients. The other 26 very small aneurysms that were not ruptured were incidentally diagnosed during imaging studies obtained for various other clinical reasons. The locations of the 31 aneurysms included 16 (52%) in the internal carotid artery, four (13%) in the anterior communicating artery, four (13%) in the posterior communicating artery, two (7%) in the internal carotid artery (ICA) bifurcation, two (7%) in the superior cerebel- lar artery, one (3%) in the anterior choroidal artery, one (3%) in the middle cerebral artery, and one (3%) in the basilar tip. The aneurysm locations of this series are summarized in Table 1. Endovascular Coil Embolization All endovascular procedures were performed on biplane angiographic systems (Alulla FD 20/10; Philips Medical Systems, Best, The Netherlands, Integris LCN+; GE, Milwaukee, WI). Rotational angiography, followed by three-dimensional (3D) reconstruction by volume render- ing was performed before the procedure in all cases. Aneurysm size was determined as the maximal diameter on 3D angiography. Coil embolization was performed under general anesthesia. In unruptured aneurysms, 3,000-4,000 units of heparin were administered at the beginning of the procedure, followed by an additional 1,000 units per hour. Heparin was continued intravenously for 24 hours after embolization. Several types of coils were used: Guglielmi detachable coils (GDC; Boston Scientific, Fremont, CA), Trufill-DCS (Cordis, Miami, FL), Microplex (Microvention, Aliso Viejo, CA), and Axium (ev3, Irvine, CA). Korean J Radiol 11(5), Sep/Oct 2010 Seven (23%) wide-neck aneurysms were coiled by using various neck-remodeling techniques. Two wide-neck aneurysms were treated with balloon assistance by HyperForm or HyperGlide (ev3). Four wide-neck aneurysms were coiled with stent assistance by Neuroform (Boston Scientific) and one wide-neck aneurysm was coiled with a combination of balloon and stent. Angiographic Outcome and Complications The immediate angiographic outcome after coiling was classified as an adequate or incomplete aneurysm. An adequate occlusion was defined as no contrast filling in the aneurysmal sac, no matter if there was neck remnant at the end of the procedure. Occlusion was considered as incomplete when contrast filling persisted in the remnant sac. Clinical and MR Angiographic Follow Up Patients treated by coil embolization were usually scheduled for a follow-up visit at the outpatient clinic at 3- 6 weeks after coiling. Follow-up imaging was performed by 3D time-of-flight (TOF) MRA at 6 months, 1 year, 2 years, and 3 years. Some patients underwent a MRA the day the embolization to obtain a baseline. Clinical and MRA follow-up periods varied from six to 39 months and averaged 13.6 months. Neurologic status according to the Glasgow Outcome Scale (GOS) was evaluated at six months and was classified as independent (GOS 4 and 5), dependent (GOS 2 and 3), and death (GOS 1). The 3D TOF-MRA was obtained on a 3.0T Philips Achieva system (Philips Medical systems) with the following 3D parameters: repetition/echo time (TR/TE) 25/3.5 ms; flip angle 25 ; matrix 880 × 450 pixels (voxel size 0.6 × 0.24 × 0.24 mm); field of view (FOV) 250 cm2. Post-processing consisted of maximum intensity projec- tions (MIPs) for 360 around the head in both a left-to- Table 1. Aneurysm Location Location ICA (paraclinoid) ICA bifurcation AcoA AchA MCA PcoA BA tip SCA Total, No. (%) (Ruptured, No.) 16 (52%) 02 (7%) 04 (13%) (3) 01 (3%) (1) 01 (3%) 04 (13%) (1) 01 (3%) 02 (7%) Note. — AchA = anterior choroidal artery, AcoA = anterior communicating artery, BA = basilar artery, ICA = internal carotid artery, MCA = middle cerebral artery, No. = number, PcoA = posterior communicating artery, SCA = superior cerebellar artery 537