Geometric and compositional appearance of atheroma in an angiographically normal carotid artery in patients with atherosclerosis

BACKGROUND AND PURPOSE: Arterial remodeling may enable atherosclerotic disease without luminal stenosis. We sought to assess the prevalence and characteristics of atherosclerosis in angiographically normal carotid arteries. MATERIALS AND METHODS: Forty-six arteries with 0% stenosis by MRA were evaluated with multicontrast carotid MR imaging at 3T. For each artery, the percentage wall volume (wall volume/[lumen volume + wall volume] x 100%) and the presence versus absence of an LRNC, calcification, IPH, and fibrous cap rupture were recorded. In addition, the relative size of each plaque component (eg, percentage LRNC = LRNC volume/wall volume x 100%), when present, was calculated. RESULTS: The mean of percentage wall volume in arteries with 0% stenosis was 43.0 ± 6.9% with a range from 31.6% to 60.1%. An LRNC was present in 67.4% (31/46) of arteries, calcification was present in 65.2% (30/46), IPH was present in 8.7% (4/46), and fibrous cap rupture was present in 4.3% (2/46). In arteries with an LRNC (n = 31), the average percentage LRNC volume was 8.8 ± 7.3% with a range from 1.0% to 31.5%. For calcification (n = 30), the mean percentage calcification volume was 3.8 ± 4.2% with a range of 0.1%-17.4%. The mean percentage IPH volume (n = 4) was 2.7 ± 1.7% with a range of 0.5%-4.1%. CONCLUSIONS: These findings indicate that stenosis by MRA may underestimate the presence of carotid atherosclerosis, and they demonstrate the need for improved methods for accurately identifying carotid atherosclerotic plaque severity.