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-High-resolution MRI has been shown to be capable of identifying plaque constituents, such as the necrotic core and intraplaque hemorrhage, in human carotid atherosclerosis. The purpose of this study was to evaluate differential contrast-weighted images, specifically a multispectral MR technique, to improve the accuracy of identifying the lipid-rich necrotic core and acute intraplaque hemorrhage in vivo. Methods and Results-Eighteen patients scheduled for carotid endarterectomy underwent a preoperative carotid MRI examination in a 1.5-T GE Signa scanner using a protocol that generated 4 contrast weightings (T1, T2, proton density, and 3D time of flight). MR images of the vessel wall were examined for the presence of a lipid-rich necrotic core and/or intraplaque hemorrhage. Ninety cross sections were compared with matched histological sections of the excised specimen in a double-blinded fashion. Overall accuracy (95% CI) of multispectral MRI was 87% (80% to 94%), sensitivity was 85% (78% to 92%), and specificity was 92% (86% to 98%). There was good agreement between MRI and histological findings, with a value of ϭ0.69 (0.53 to 0.85). Conclusions-Multispectral MRI can identify the lipid-rich necrotic core in human carotid atherosclerosis in vivo with high sensitivity and specificity. This MRI technique provides a noninvasive tool to study the pathogenesis and natural history of carotid atherosclerosis. Furthermore, it will permit a direct assessment of the effect of pharmacological therapy, such as aggressive lipid lowering, on plaque lipid composition.

Background-Recent studies demonstrated that in vivo and ex vivo MRI can characterize the components of the carotid atherosclerotic plaque, such as fibrous tissue, lipid/necrotic core, calcium, hemorrhage, and thrombus. The purpose of this study was to determine whether in vivo high-resolution multicontrast MRI could accurately classify human carotid atherosclerotic plaque according to the American Heart Association classification. Methods and Results-Sixty consecutive patients (mean age 70 years; 54 males) scheduled for carotid endarterectomy were imaged with a 1.5-T scanner after informed consent was obtained. A standardized protocol was used to obtain 4 different contrast-weighted images (time of flight and T1-, PD-, and T2-weighted) of the carotid arteries. Best voxel size was 0.25ϫ0.25ϫ1 mm 3 . Carotid plaques were removed intact and processed for histological examination. Both MR images and histological sections were independently reviewed, categorized, and compared. Overall, the classification obtained by MRI and the American Heart Association classifications showed good agreement, with Cohen's (95% CI) of 0.74 (0.67 to 0.82) and weighted of 0.79. The sensitivity and specificity, respectively, of MRI classification were as follows: type I-II lesions, 67% and 100%; type III lesions, 81% and 98%; type IV-V lesions, 84% and 90%; type VI lesions, 82% and 91%; type VII lesions, 80% and 94%; and type VIII lesions, 56% and 100%. Conclusions-In vivo high-resolution multicontrast MRI is capable of classifying intermediate to advanced atherosclerotic lesions in the human carotid artery and is also capable of distinguishing advanced lesions from early and intermediate atherosclerotic plaque.