Reassessing the Carotid Artery Plaque “Rim Sign” on CTA: A New Analysis with Histopathologic Confirmation

Abstract

<h3>BACKGROUND AND PURPOSE:</h3> The CTA “rim sign” has been proposed as an imaging marker of intraplaque hemorrhage in carotid plaques. This study sought to investigate such findings using histopathologic confirmation. <h3>MATERIALS AND METHODS:</h3> Included patients had CTA neck imaging &lt;1 year before carotid endarterectomy. On imaging, luminal stenosis and the presence of adventitial (&lt;2-mm peripheral) and “bulky” (≥2-mm) calcifications, total plaque thickness, soft-tissue plaque thickness, calcification thickness, and the presence of ulcerations were assessed. The rim sign was defined as the presence of adventitial calcifications with internal soft-tissue plaque of ≥2 mm in maximum thickness. Carotid endarterectomy specimens were assessed for both the presence and the proportional makeup of lipid material, intraplaque hemorrhage, and calcification. <h3>RESULTS:</h3> Sixty-seven patients were included. Twenty-three (34.3%) were women; the average age was 70.4 years. Thirty-eight (57.7%) plaques had a rim sign on imaging, with strong interobserver agreement (κ = 0.85). A lipid core was present in 64 (95.5%) plaques (average, 22.2% proportion of plaque composition); intraplaque hemorrhage was present in 52 (77.6%), making up, on average, 13.7% of the plaque composition. The rim sign was not associated with the presence of intraplaque hemorrhage (<i>P </i>= .11); however, it was associated with a greater proportion of intraplaque hemorrhage in a plaque (<i>P </i>= .049). The sensitivity and specificity of the rim sign for intraplaque hemorrhage were 61.5% and 60.0%, respectively. <h3>CONCLUSIONS:</h3> The rim sign is not associated with the presence of intraplaque hemorrhage on histology. However, it is associated with a higher proportion of hemorrhage within a plaque and therefore may be a biomarker of more severe intraplaque hemorrhage, if present.

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