Dynamic contrast-enhanced MR angiography and MR imaging of the carotid artery: high-resolution sequences in different acquisition planes

Abstract

Background and purpose: First-pass contrast-enhanced MR angiography has become the technique of choice for studying the carotid bifurcation, but this method has some limitations. We evaluated the clinical utility of performing 3D contrast-enhanced MR angiography in the axial plane immediately after performing angiography in the coronal plane.

Methods: Cervical carotid arteries of 80 consecutive patients were studied on a 1.5-T MR imager with phased-array coils. Coronal 3D MR angiography was performed after administering a bolus injection of contrast material (20 mL) with automatic triggering. This was immediately followed by an axial acquisition. We measured carotid diameters on the contrast-enhanced MR angiograms as well as on intra-arterial digital subtraction angiograms according to established criteria. We also evaluated original source MR angiograms.

Results: Angiograms obtained in the axial plane correlated better with the intra-arterial digital subtraction angiograms than did the coronal angiograms. When first-pass contrast-enhanced MR angiography was incomplete because of a failure of triggering, the second-phase acquisition provided sufficient image quality. Original source images suffered from ring artifacts, low axial resolution, and a low level of soft-tissue visualization. Axial-based source images showed flow-independent contrast filling to the patent lumen with sufficient visualization of plaque morphology, thickened arterial wall, and surrounding disease processes, such as tumors.

Conclusion: With the addition of a 1-minute second-phase 3D acquisition in a different plane immediately after first-pass contrast-enhanced MR angiography, one can obtain a more accurate depiction of the carotid bifurcation, insurance against failure of triggering, and diagnostic source images.

fig 1.

Correlation between second-phase (axial) 3D MR angiography and IADSA. Twenty carotid arteries in 15 patients were analyzed

fig 2.

Correlation between first-pass (coronal) 3D MR angiography and IADSA. Eighteen carotid arteries in 14 patients were analyzed

fig 3.

Severe stenosis of the left internal carotid artery in a 79-year-old man. A–D, IADSA image (lateral view) (A); partial MIP image of second-phase (axial) 3D contrast-enhanced MR angiogram (B); partial MIP image of the first-pass (coronal) 3D angiogram (C); source image of the second-phase (axial) 3D angiogram (D). Irregular forms of stenosis are well visualized on axial view; however, coronal view fails to show details of the stenotic lesions, mainly because of low spatial resolution in the anteroposterior direction. A source image of second-phase (axial) 3D angiography clearly shows irregular plaque (arrow, D).

fig 4.

Marked thickening of left common carotid wall in a 35-year-old woman with arteritis. A, First-pass (coronal) 3D contrast-enhanced MR angiography shows occlusion of the left common carotid artery (arrow) and the left subclavian artery. The right common and internal carotid arteries are dilated. B, Source image of second-phase (axial) MR angiography shows marked thickening and enhancement of the wall of the common carotid artery (arrows). fig 5. Source image of second-phase (axial) MR angiography shows invasion of the left internal carotid artery by nasopharyngeal carcinoma (arrow)