[Clinical Usefulness of Ultra-short TE MRA for Follow-up Imaging after Cerebral Aneurysm Clipping].

The aims of this study were to elucidate signal pattern of cerebral aneurysm clip in brain magnetic resonance angiography (MRA) using non-contrast enhanced ultra-short echo time (UTE) sequence and to explore effective utilization of this novel technique for patients, who underwent cerebral aneurysm clipping. The clip was embedded in homemade phantom and scanned using UTE sequence. We investigated characteristic features of the artifacts derived from the clip. Besides, we compared the volume of signal loss between conventional time-of-flight (TOF) and UTE-MRA in 50 patients with the cerebral aneurysm clip. In phantom study, the clip was delineated as signal void area fully surrounded by high signal on original images. On reconstructed short-axial views for the clip, four-leaf clover pattern of artifact was observed when clip was arranged orthogonal to the static magnetic field. On the other hand, this artifact disappeared when the clip was arranged in parallel with the static magnetic field. The volume of signal loss in clinical cases was significantly reduced in UTE-MRA (P < 0.05): 1.30, 0.52-2.77 cm3 for TOF; 0.84, 0.28-1.74 cm3 for UTE (median, range). The scan time for UTE-MRA was 2 minutes and 52 seconds. To understand the characteristic feature of the artifacts from the clip could contribute to define vascular structure in image interpretation. Adding UTE-MRA to routine protocol is useful approach for follow-up imaging after cerebral aneurysm clipping with clinically acceptable prolongation of the scan time.