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

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. 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 (1.5T:0.78 x 0.55 x 0.8 mm, voxel size; acquisition time (TA), 6.37 min; 3T:0.56 x 0.45 x 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. 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 (Kw∼0.8, respectively). 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. (orig.)