Evaluation of carotid plaque vulnerability in vivo: Correlation between dynamic contrast-enhanced MRI and MRI-modified AHA classification.

Purpose: To noninvasively monitor carotid plaque vulnerability by exploring the relationship between pharmacokinetic parameters (PPs) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and plaque types based on MRI-modified American Heart Association (AHA) classification, as well as to assess the ability of PPs in discrimination between stable and vulnerable plaques suspected on MRI. Materials and Methods: Of 70 consecutive patients with carotid plaques who volunteered for 3.0T MRI (3D time-of- flight [TOF], T-1-weighted, T-2-weighted, 3D magnetization-prepared rapid acquisition gradient-echo [MP-RAGE] and DCE-MRI), 66 participants were available for analysis. After plaque classification according to MRI-modified AHA Lesion-Type (LT), PPs (K-trans, k(ep), v(e), and v(p)) of DCE-MRI were measured. The Extended Tofts model was used for calculation of PPs. For participants with multiple carotid plaques, the plaque with the worst MRI-modified AHA LT was chosen for analysis. Correlations between PPs and plaque types and the ability of these parameters to distinguish stable and vulnerable plaques suspected on MRI were assessed. Results: Significant positive correlation between K-trans and LT III to VI was found (p=0.532, P < 0.001), as was the correlation between kep and LT III to VI (p=0.409, P < 0.001). Stable and vulnerable plaques suspected on MRI could potentially be distinguished by K-trans (sensitivity 83%, specificity 100%) and k(ep) (sensitivity 77%, specificity 91%). Conclusion: K-trans and k(ep) from DCE-MRI can provide quantitative information to monitor plaque vulnerability in vivo and differentiate vulnerable plaques suspected on MRI from stable ones. These two parameters could be adopted as imaging biomarkers for plaque characterization and risk stratification.