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Real-time Measurement System for Evaluation of the Carotid Intima-Media Thickness With a Robust Edge Operator

Institute of Clinical Physiology, National Research Council, Pisa, Italy (F.F., V.G., E.B., M.D.); Department of Internal Medicine, University of Pisa, Pisa, Italy (G.G., L.G.); and Esaote SpA, Genoa, Italy (M.D.).

Address correspondence to Francesco Faita, PhD, Institute of Clinical Physiology, National Research Council, Via G. Moruzzi 1, 56124 Pisa, Italy. E-mail: f.faita{at}ifc.cnr.it

Objective. The purpose of this report is to describe an automatic real-time system for evaluation of the carotid intima-media thickness (CIMT) characterized by 3 main features: minimal interobserver and intraobserver variability, real-time capabilities, and great robustness against noise. Methods. One hundred fifty carotid B-mode ultrasound images were used to validate the system. Two skilled operators were involved in the analysis. Agreement with the gold standard, defined as the mean of 2 manual measurements of a skilled operator, and the interobserver and intraobserver variability were quantitatively evaluated by regression analysis and Bland-Altman statistics. Results. The automatic measure of the CIMT showed a mean bias ± SD of 0.001 ± 0.035 mm toward the manual measurement. The intraobserver variability, evaluated with Bland-Altman plots, showed a bias that was not significantly different from 0, whereas the SD of the differences was greater in the manual analysis (0.038 mm) than in the automatic analysis (0.006 mm). For interobserver variability, the automatic measurement had a bias that was not significantly different from 0, with a satisfactory SD of the differences (0.01 mm), whereas in the manual measurement, a little bias was present (0.012 mm), and the SD of the differences was noticeably greater (0.044 mm). Conclusions. The CIMT has been accepted as a noninvasive marker of early vascular alteration. At present, the manual approach is largely used to estimate CIMT values. However, that method is highly operator dependent and time-consuming. For these reasons, we developed a new system for the CIMT measurement that conjugates precision with real-time analysis, thus providing considerable advantages in clinical practice.

Key Words: carotid artery • edge detection • intima-media thickness • real-time ultrasound imaging • thickness measurement

Abbreviations: ANG, angle • AUTO, automatic • CI, confidence interval • CIMT, carotid intima-media thickness • COEFF, coefficient • FOAM, first-order absolute moment edge operator • GS, gold standard • GUI, graphical user interface • OP, operator • MAN, manual • MAX, maximum • PX, point • ROI, region of interest • TH, threshold