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AJNR - American Journal of Neuroradiology

Published ahead of print on February 13, 2008
doi: 10.3174/ajnr.A0950

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American Journal of Neuroradiology 29:875-882, May 2008
© 2008 American Society of Neuroradiology

HEAD & NECK

High-Resolution CT Imaging of Carotid Artery Atherosclerotic Plaques

M. Wintermark^a, S.S. Jawadi^f, J.H. Rapp^e, T. Tihan^b, E. Tong^a, D.V. Glidden^c, S. Abedin^f, S. Schaeffer^a, G. Acevedo-Bolton^a, B. Boudignon^d, B. Orwoll^d, X. Pan^e and D. Saloner^a

^a Department of Radiology, Neuroradiology Section, University of California, San Francisco, Calif
^b Department of Pathology, University of California, San Francisco, Calif
^c Department of Epidemiology and Biostatistics, University of California, San Francisco, Calif
^d Division of Endocrinology, University of California, San Francisco, Calif
^e Department of Vascular Surgery, San Francisco Veterans Administration Medical Center, San Francisco, Calif
^f Department of Diagnostic Radiology, University of Missouri-Kansas City School of Medicine, Kansas City, Mo

Please address correspondence to Max Wintermark, MD, Department of Radiology, Neuroradiology Section, University of California San Francisco, 505 Parnassus Ave, Box 0628, San Francisco, CA 94143-0628; e-mail: max.wintermark{at}radiology.ucsf.edu

BACKGROUND AND PURPOSE: Plaque morphologic features have been suggested as a complement to luminal narrowing measurements for assessing the risk of stroke associated with carotid atherosclerotic disease, giving rise to the concept of "vulnerable plaque." The purpose of this study was to evaluate the ability of multidetector-row CT angiography (CTA) to assess the composition and characteristics of carotid artery atherosclerotic plaques with use of histologic examination as the gold standard.

MATERIALS AND METHODS: Eight patients with transient ischemic attacks who underwent carotid CTA and "en bloc" endarterectomy were enrolled in a prospective study. An ex vivo micro-CT study of each endarterectomy specimen was obtained, followed by histologic examination. A systematic comparison of CTA images with histologic sections and micro-CT images was performed to determine the CT attenuation associated with each component of the atherosclerotic plaques. A computer algorithm was subsequently developed that automatically identifies the components of the carotid atherosclerotic plaques, based on the density of each pixel. A neuroradiologist's reading of this computer analysis was compared with the interpretation of the histologic slides by a pathologist with respect to the types and characteristics of the carotid plaques.

RESULTS: There was a 72.6% agreement between CTA and histologic examination in carotid plaque characterization. CTA showed perfect concordance for calcifications. A significant overlap between densities associated with lipid-rich necrotic core, connective tissue, and hemorrhage limited the reliability of individual pixel readings to identify these components. However, CTA showed good correlation with histologic examination for large lipid cores ( = 0.796; P < .001) and large hemorrhages ( = 0.712; P = .102). CTA performed well in detecting ulcerations ( = 0.855) and in measuring the fibrous cap thickness (R² = 0.77; P < .001).

CONCLUSION: The composition of carotid atherosclerotic plaques determined by CTA reflects plaque composition defined by histologic examination.

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