Complementary value of cardiac FDG PET and CT for the characterization of atherosclerotic disease

For decades, the identification of significant luminal narrowing has been the hallmark to characterize the presence and extent of coronary artery disease. However, it is now known that characterizations of systemic atherosclerosis burden and inflammation, as well as the local quality of plaque composition and morphology, allow better characterization of coronary artery disease and thus may allow improved prediction of adverse cardiovascular events. Plaque characterized histologically as a thin-cap fibroatheroma (ie, an atheroma with a thin fibrous cap, an underlying lipid-rich necrotic core, and inflammatory activity) has been recognized as representing vulnerable or high-risk plaque. Positron emission tomography (PET) and cardiac computed tomography (CT) are noninvasive modalities that provide metabolic (PET) and morphologic (CT) information about atherosclerotic plaque. PET allows the quantification of the uptake of fluorine 18 fluorodeoxyglucose (FDG) within the arterial wall, which provides a measure of macrophage activity within atheromatous plaque. Coronary CT allows the depiction of plaque morphology and composition. Thus, integrated imaging with PET and CT (PET/CT) permits coregistration of FDG activity with the presence and morphology of plaque and may lead to improved characterization of vulnerable plaque or vulnerable patients, or both. This review details the methods and principles of cardiac FDG PET and coronary CT and provides an overview of the research, with an emphasis on the identification and characterization of vulnerable plaque.