Vascular inflammation is a key factor in both the pathogenesis and outcome of atherosclerosis. 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising tool for identifying and quantifying vascular inflammation within atherosclerotic plaques.cardiac multidetector-row CT can provide measurements of coronary artery calcium (CAC), the degree of stenosis, and the characteristics of plaque including its potential vulnerability. Therefore, the purpose of the investigators study is to compare the usefulness of 18 FDG-PET and MDCT in assessing the vascular inflammatory status and vulnerability.