Measuring Progression of Coronary Atherosclerosis with Computed Tomography: Searching for Clarity Among Shades of Gray

Computed tomography (CT) allows visualization of both calcified and noncalcified atherosclerotic plaque in the entire coronary tree. When assessing an individual patient's risk of cardiac events, direct visualization of coronary plaque has substantial advantages over assessment of surrogate markers or risk factors. Ideally, practitioners would be able to follow progression or regression of coronary disease via quantitative measurements of plaque volume and composition in individual patients. Once this is possible, CT could be used to: (1) make more informed decisions about whether and how aggressively to treat patients at risk for coronary artery disease, and (2) to follow the effects of treatment in patients with known coronary artery disease. At this point in time, coronary calcium scoring is more reproducible than CT angiography for quantifying plaque and also has a much larger body of evidence supporting its ability to predict cardiac events. In this paper we will review the current techniques for quantifying calcified and noncalcified coronary atherosclerosis with cardiac CT, the strengths and limitations of each approach and the data supporting the ability to quantify and follow progression or regression of plaque.