Published Online
on May 23, 2005

A more recent version of this article appeared on May 31, 2005

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Submitted on June 8, 2004
Revised on January 25, 2005
Accepted on February 22, 2005

Ultrasound Measurement of the Fibrous Cap in Symptomatic and Asymptomatic Atheromatous Carotid Plaques

Gérald Devuyst MD^*, Patrick Ruchat MD, Theodoros Karapanayiotides MD, Lisa Jonasson MS, Olivier Cuisinaire PhD, Johannes-Alexander Lobrinus MD, Marc Pusztaszeri MD, Askenadios Kalangos MD, Paul-André Despland MD, Jean-Philippe Thiran PhD, and Julien Bogousslavsky MD

From the Department of Neurology (G.D., T.K., P.-A.D., J.B.), Division of Neuropathology (J.-A.L., M.P.), and Department of Cardiovascular Surgery (P.R.), Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland; Signal Processing Institute (L.J., O.C., J.-P.T.), Swiss Federal Institute of Technology, Lausanne, Switzerland; and Department of Cardiovascular Surgery, Geneva University Hospital (A.K.), Geneva, Switzerland.

^* To whom correspondence should be addressed. E-mail: gerald.devuyst{at}chuv.hospvd.ch.

Background--Fibrous cap thickness (FCT) is an important determinant of atheroma stability. We evaluated the feasibility and potential clinical implications of measuring the FCT of internal carotid artery plaques with a new ultrasound system based on boundary detection by dynamic programming.

Methods and Results--We assessed agreement between ultrasound-obtained FCT values and those measured histologically in 20 patients (symptomatic [S]=9, asymptomatic [AS]=11) who underwent carotid endarterectomy for stenosing (>70%) carotid atheromas. We subsequently measured in vivo the FCT of 58 stenosing internal carotid artery plaques (S=22, AS=36) in 54 patients. The accuracy in discriminating symptomatic from asymptomatic plaques was assessed by receiver operating characteristic curves for the minimal, mean, and maximal FCT. Decision FCT thresholds that provided the best correct classification rates were identified. Agreement between ultrasound and histology was excellent, and interobserver variability was small. Ultrasound showed that symptomatic atheromas had thinner fibrous caps (S versus AS, median [95% CI]: minimal FCT=0.42 [0.34 to 0.48] versus 0.50 [0.44 to 0.53] mm, P=0.024; mean FCT=0.58 [0.52 to 0.63] versus 0.79 [0.69 to 0.85] mm, P<0.0001; maximal FCT=0.73 [0.66 to 0.92] versus 1.04 [0.94 to 1.20] mm, P<0.0001). Mean FCT measurement demonstrated the best discriminatory accuracy (area under the curve [95% CI]: minimal 0.74 [0.61 to 0.87]; mean 0.88 [0.79 to 0.97]; maximal 0.82 [0.71 to 0.93]). The decision threshold of 0.65 mm (mean FTC) demonstrated the best correct classification rate (82.8%; positive predictive value 75%, negative predictive value 88.2%).

Conclusions--FCT measurement of carotid atheroma with ultrasound is feasible. Discrimination of symptomatic from asymptomatic plaques with mean FCT values is good. Prospective studies should determine whether this ultrasound marker is reliable.

Key words: ultrasonics • plaque • carotid arteries • atherosclerosis • cerebrovascular disorders

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