Atherosclerotic Plaque Characterization by MR Imaging

The MR imaging of carotid artery and aortic plaque has undergone significant improvement in the last decade. Early studies utilizing ex vivo specimens and spin echo or fast spin echo imaging, led to the conclusion that T2-weighting was the best single contrast to characterize carotid plaque morphology. On these images, the fibrous plaque appears bright and the lipid core is dark; thrombus can have variable intensity. There can be an overlap in T2w signal intensities among the various plaque components, which can be partially offset by the use of qualitative or multi-spectral analysis of multiple contrast images. With improvements in coil design, sequence design, main field and gradient capabilities, accurate in vivo differentiation and measurement of these various plaque components should be possible in a few years. Carotid and aortic plaque burden can be accurately measured in vivo today; ongoing longitudinal studies should lead to a better understanding of the relationship between plaque burden and the risk of thromboembolic complications, as well as the effect of diet and drug therapy in hyperlipidemic patients. With these developments in place or soon to be available, MR imaging of the diseased carotid artery and aortic wall may prove to be even more important than MR angiography or other current clinical tests.