As nuclear cardiology has developed a broader conceptual base, moving from classical precepts of systems physiology to molecular and cell biology, there has been increasing interest in the study of the vascula-ture in addition to classical studies that have focused on the myocyte.Experiments in laboratory animals and human beings have used a variety of new biologically relevant targets for imaging the blood vessel wall, such as low-density.. lipoprotein cholesterol, oxidized low-density lipoprotein cholesterol, macrophages, cellular apoptosis, integrins such as avp3, matrix metallopro-teases, and cathepsins.3'9 There has been substantial interest in the macrophage as an imaging target, based on awareness of this cell's fundamental importance in the biology and progression of atherosclerosis.10 Macrophages clearly play an important role in the development of plaque vulnerability and hence are a real risk factor for plaque rupture, erosion, and resultant intravascular thrombosis. Fluorodeoxyglucose (FDG)accumulation within the vessel wall has been shown to correspond to sites of macrophage infiltration.11 Presumably, the augmented metabolic activity of macrophages leads to local FDG uptake sufficient to allow visualization with positron emission tomography (PET).12 In the smaller coronary arteries FDG uptake has been noted with specially designed intravascular catheter-based radiation detectors.13 A large body of data has accumulated concerning the relevance of vascular calcification by computed tomography (CT) to the atherosclerotic process. Visualized vascular calcification generally signifies a more advanced or mature stage of the atherosclerotic process.14
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