Contrast-enhanced 3D MR DSA of the carotid artery bifurcation: preliminary study of comparison with unenhanced 2D and 3D time-of-flight MR angiography.

Purpose: To compare the delineation of stenosis at the carotid artery bifurcation on three-dimensional (3D) magnetic resonance (MR) digital subtraction angiographic (DSA) images with that on two-dimensional (2D) and 3D time-of-flight (TOF) MR angiographic images.
Materials and Methods: Twenty-six patients with 29 carotid artery bifurcations and symptoms of cerebral ischemia underwent 3D MR DSA. A time-resolved series was generated with 3D MR DSA after the bolus injection of gadodiamide. The resolution for a carotid artery examination was 0.4 x 0.4 x 1.0 mm, with volumes reconstructed at 4.5-second intervals. The 3D MR DSA images were compared with contemporaneously acquired unenhanced 2D and 3D TOF images. Two observers ranked the 2D and 3D TOF MR angiographic and 3D MR DSA images according to the following: (a) stenosis delineation, (b) internal carotid artery delineation, (c) intravascular signal intensity, and (d) diagnostic confidence.
Results: The mean ranking for diagnostic confidence was 1.10 (1 = best technique, 3 = worst technique) for 3D MR DSA. Compared with the pooled 2D TOF and 3D TOF ranks, the 3D MR DSA rank was significantly better (P < .01). Similar levels of statistical significance were found for the other criteria.
Conclusion: Three-dimensional MR DSA improves the delineation of carotid arterial stenosis by virtually eliminating saturation effects and reducing intravoxel dephasing. Surface morphology and nearly occluded vessels ("string sign") were easily identified. Confidence in identifying carotid arterial occlusions was also very high with this technique.