Insights from CTA with Comparison to Modalities of Intravascular Ultrasound Imaging

Noninvasive imaging of atherosclerosis by cardiac CT continues to rapidly evolve. A large collection of data has emerged on detection and quantification of coronary plaque in vivo with cardiac CT with comparison to the gold standard of clinical plaque assessment, intravascular ultrasound. Given inherent spatial limitations, although the correlation is significant, the variability and limits of agreement of these measurements are wide. More recently, focus has shifted to detecting plaque stability, or rather high-risk features of plaque, and identifying those “vulnerable” to rupture. This is a concept originated in histopathology and translated clinically into invasive plaque characterization through virtual histology, or IVUS-VH. We will review the literature regarding methods of plaque assessment, as well as plaque progression and outcomes data, in cardiac CT with regard to its correlation with IVUS and IVUS-VH. The potential in cardiac CT lies within the noninvasive detection of coronary artery disease, its ability to help distinguish those plaques and thus, those patients most vulnerable, which ultimately may be utilized for risk stratification, direction of aggressive therapy, and even as a way to evaluate effects of medical therapies.