Objective-This study evaluates the ability of MRI to quantify all major carotid atherosclerotic plaque components in vivo. Methods and Results-Thirty-one subjects scheduled for carotid endarterectomy were imaged with a 1.5T scanner using time-of-flight-, T1-, proton density-, and T2-weighted images. A total of 214 MR imaging locations were matched to corresponding histology sections. For MRI and histology, area measurements of the major plaque components such as lipid-rich/necrotic core (LR/NC), calcification, loose matrix, and dense (fibrous) tissue were recorded as percentages of the total wall area. Intraclass correlation coefficients (ICCs) were computed to determine intrareader and inter-reader reproducibility. Key Words: atherosclerosis Ⅲ magnetic resonance imaging Ⅲ carotid artery Ⅲ plaque A therosclerosis and its thrombotic complications are the leading cause of morbidity and mortality in industrialized countries. Therefore, the need for new medical therapies and technology to treat and prevent cardiovascular atherosclerotic disease is enormous.Accurate information of atherosclerotic plaque morphology and plaque composition is necessary to identify the "vulnerable plaques" that are likely to cause embolic events. A noninvasive imaging modality that could provide such information would be an invaluable tool in studies of the relationship between plaque composition/morphology and plaque progression/regression. Furthermore, such imaging techniques may be used in clinical trials to monitor the effects of drugs on diseased arteries.B-Mode ultrasonography has been used widely in plaque progression/regression trials that involve either lipidlowering drugs or calcium channel blockers. 1 However, this modality is highly operator dependent, has limited soft tissue contrast, and requires a large number of subjects to detect a significant change in the intima-media thickness. 1 Intravascular ultrasound (IVUS) is used increasingly in atherosclerosis regression/progression trials that study coronary arteries. 2 Although IVUS is highly reproducible 3 and provides tomographic information about the vessel wall, 3 it is an invasive procedure and has limited capacity to discriminate between fibrous and fatty plaques. 4 Recent publications 5-11 have shown that in vivo MRI can identify the main components of the atherosclerotic plaque such as the lipid-rich/necrotic core (LR/NC), calcification, and hemorrhage. In addition, morphological information about the status of the fibrous cap 12 and the American Heart Association (AHA) lesion type 13 can be obtained noninvasively. Moreover, the tomographic orientation of MRI enables the full cross-sectional view of the vessel wall, which can be measured accurately 14 and reproducibly. 15 It has been demonstrated that ex vivo MRI of endarterectomy specimen is able to identify 16 and quantify 17,18 plaque components with high diagnostic accuracy. This study is aimed at evaluating the ability of MRI to quantify all major carotid atherosclerotic plaque components in vivo, using histolog...

Background-Previous studies with contrast-enhanced magnetic resonance imaging (CEMRI) have shown that the fibrous cap (FC) in atherosclerotic carotid plaques enhances with gadolinium-based contrast agents. Conversely, the lipid-rich necrotic core (LR-NC), lacking both vasculature and matrix, shows no or only slight enhancement. The goal of this study was to assess whether CEMRI can be used to accurately measure the dimensions of the intact FC and LR-NC. Methods and Results-Twenty-one patients scheduled for carotid endarterectomy were imaged with a 1.5-T scanner.Precontrast images and CEMRI were obtained. One hundred eight locations with an intact FC were matched between MRI and the excised histology specimens. Quantitative measurements of FC length along the lumen circumference, FC area, and LR-NC area were collected from CEMRI images and histology sections.

Background-Previous studies suggest that erythrocyte membranes from intraplaque hemorrhage into the necrotic core are a source of free cholesterol and may become a driving force in the progression of atherosclerosis. We have shown that MRI can accurately identify carotid intraplaque hemorrhage and precisely measure plaque volume. We tested the hypothesis that hemorrhage into carotid atheroma stimulates plaque progression. Methods and Results-Twenty-nine subjects (14 cases with intraplaque hemorrhage and 15 controls with comparably sized plaques without intraplaque hemorrhage at baseline) underwent serial carotid MRI examination with a multicontrast weighted protocol (T1, T2, proton density, and 3D time of flight) over a period of 18 months.