Atherosclerosis/Plaque Imaging with CMR

Editors-in-Chief: Eric A. Osborn, M.D., Ph.D. [mailto:eosborn@bidmc.harvard.edu] and Eli V. Gelfand, M.D. [mailto:egelfand@bidmc.harvard.edu] (Beth Israel Deaconess Medical Center, Harvard Medical School)

Introduction
Cardiovascular magnetic resonance (CMR) plaque imaging allows characterization of the biology of atherosclerotic lesions. Using multiple imaging sequences targeted to specific plaque constituents, the underlying composition of the plaque is determined including markers of remodeling and inflammation that are clinically relevant surrogates of plaque stability. With this technique, ‘vulnerable’ plaques prone to rupture are identified that predispose patients to acute coronary syndromes and stroke.

Pulse sequences

 * Bright blood sequences are used for angiography
 * Black blood sequences are used for vessel wall imaging

Techniques

 * Identification of plaque components requires a multi-contrast approach with three weightings (T1, PD, T2) in black blood imaging and complementary bright blood imaging
 * T1- and PD-weightings provide strong signal from the fibrous matrix and lipid core
 * T2 aides in discriminating certain plaque tissue types but has a lower SNR and poor wall delineation
 * Dynamic contrast enhancement (CE) with gadolinium allows evaluation of neovascularization and the time-dependent diffusion of contrast into the extracellular space
 * Novel contrast media for molecular imaging are being developed (see Molecular imaging and related novel technologies)
 * Resolution: 0.4-0.6mm in-plane, 2-3mm slice thickness

Size
Fig. Simple plaque Fig. Complex plaque
 * Thickness
 * Eccentricity
 * Distribution
 * Proximity of the necrotic core to the lumen

Composition
Fig. Lipid-rich / necrotic core Fig. Dense fibrous cap Fig. Loose fibrous cap Fig. Fresh hemorrhage Fig. Old hemorrhage
 * Lipid-rich / necrotic core
 * Fibrous cap
 * Calcifications
 * Hemorrhage

Biological activity
Fig.  Fig. 
 * Cellular markers of plaque generation
 * Inflammatory reaction at the fibrous cap

Further online resources

 * Patient information about cardiac MR from the American College of Radiology.