Carotid and Vertebral Artery Dissection: Elliptical Centric Contrast-enhanced MR Angiography
Background and Purpose: Contrast-enhanced MR angiography (CEMRA) has undergone considerable development in the past several years. Recently, a CEMRA technique was developed using elliptical centric view-ordering. The purpose of this study was to evaluate elliptical centric CEMRA of carotid and vertebral artery dissection. Methods: A retrospective review of CEMRAs in 422 consecutive patients was performed. MR angiography was performed using a volume neck coil or a dedicated neurovascular coil. The CEMRA utilized a 22 x 15 cm field of view (FOV) coronal slab, 44 sections, repetition time of 6.6 msec, echo time 1.4 msec, 45° flip angle, 256 x 168 (due to 3/4 phase FOV) matrix with a scan time of 54 seconds. The reconstruction used zero-filling in all three directions yielding 88 1.4 mm thick sections with 0.7 mm overlap and a 512 x 336 matrix. The actual voxel size was 0.76 (X) x 0.89 (Y) x 1.4 mm, yielding a voxel volume of 0.97 mm3 before zero-filling. Zero-filling improved resolution and yielded an effective voxel volume of approximately 0.35 mm3. Triggering of the CEMRA was performed with MR fluoroscopy or following a timing sequence. 20–25 cc of gadolinium was injected with a power injector at a rate of 3 cc per second followed by 30 cc of saline at a rate of 2 cc per second. Results: Of the 422 patients, 239 had acute or recent symptoms of TIA or ischemic stroke. Of this group, 32 patients had a carotid artery (22) or a vertebral artery (10) dissection. Eleven patients had a pseudoaneurysm detected at the site of the dissection. Recanalization of a previously occluded artery and a resolution of a pseudoaneurysm were demonstrated in one patient, respectively. In one patient, the CEMRA appeared normal, however, a subtle irregularity consistent with a vertebral artery dissection was demonstrated on a conventional angiogram two days following the MR angiogram. Conclusions: Contrast-enhanced elliptical centric MR angiography offers high resolution, venous-suppressed images of the carotid and vertebral arteries. This technique offers promise for noninvasive evaluation and follow-up of carotid and vertebral artery dissections.