Atherosclerotic plaque at the carotid bifurcation: CT angiographic appearance with histopathologic correlation

BACKGROUND AND PURPOSE: The likelihood that carotid plaque will give rise t o cerebral ischemia probably relates to the degree of arterial stenosis and to plaque morphology, The aim of this study was to assess whether features seen at CT angiography might be used to predict carotid plaque stability b y comparing CT angiograms with histopathologic examinations of the carotid artery bifurcation, METHODS: Nine patients with symptomatic severe carotid stenosis at intraart erial angiography had CT angiography of the carotid bifurcation before caro tid endarterectomy, After endarterectomy, multiple sections of the specimen s through the carotid bifurcation were examined histologically. Plaque char acteristics recorded included the proportion of necrotic/lipid core, presen ce of hemorrhage, extent of fibrosis, ulceration, calcification, inflammato ry cell infiltrate, and fibrous cap thickness. Corresponding CT angiograms were assessed for plaque size, distribution, and radiodensity as well as pr esence of calcific density and ulceration. Histologic findings and CT angio grams were compared. RESULTS: Plaque with a large necrotic/lipid core, which was often hemorrhag ic, was found in 16 of 23 sections, and in 15 of these this histologic appe arance corresponded with patchy or homogeneous low density on CT angiograms . Six of seven predominantly fibrous plaques were of soft-tissue density on CT angiograms. High density consistent with calcification was seen more fr equently on CT angiograms than it was detected histologically, but CT angio graphy depicted plaque ulceration poorly (four ulcers at histology; two fal se-positive and two false-negative findings at CT angiography), CONCLUSION: CT angiography is a promising method for assessing the lumen an d wall of the carotid artery. The apparent correlation between histologic a ppearance and plaque density on CT angiograms has important implications fo r the prediction of plaque stability, even though ulceration is shown incon sistently.