No advantage of time-of-flight magnetic resonance angiography at 3 Tesla compared to 1.5 Tesla in the follow-up after endovascular treatment of cerebral aneurysms

Abstract

Introduction: Long-term follow-up after coil embolization of intracranial aneurysms is mandatory to monitor coil compacting and aneurysm recurrence. Most centers perform one digital subtraction angiography (DSA) on follow-up continuing with time-of-flight magnetic resonance angiography (TOF-MRA). This study explores the diagnostic value of TOF-MRA at 1.5 T versus 3 T compared to DSA. Materials and methods: In 18 patients with 20 aneurysms treated with coil embolization, TOF-MRA at 1.5 and 3 T were performed the day before follow-up DSA, the latter serving as reference. Optimized diagnostic protocols were applied (1.5 T: 0.78×0.55×0.8 mm, voxel size; acquisition time (TA), 6.37 min; 3 T: 0.56×0.45×0.65 mm, voxel size; TA, 3.12 min). Three independent neuroradiologists experienced in neuroendovascular therapy rated the occlusion rate ("complete occlusion" vs. "residual neck" vs. "residual aneurysm") and compared the two methods subjectively. Weighted κ statistics were calculated to assess the level of interobserver agreement. Results: Compared to DSA, TOF-MRA was more sensitive in detecting neck remnants, with a slight advantage at 3 T. Regarding artifact load, there are advantages at 1.5 T. Ratings of the occlusion rate correlated highly between all observers (r>0.85, p<0.001, respectively). Interobserver agreement was high in all cases (k w ≈ 0.8, respectively). Conclusion: TOF-MRA is a reliable tool for follow-up imaging of cerebral aneurysms after endovascular treatment. Our study shows no advantage of TOF-MRA at 3 T over 1.5 T, when comparable measurement protocols are applied. TOF-MRA at 1.5 T therefore provides appropriate information regarding a therapeutic decision. © 2008 The Author(s).