In Vivo Ultrasonic Parametric Imaging of Carotid Atherosclerotic Plaque by Videodensitometric Technique

Abstract

Extensive experimental and clinical data show that the ultrasonic image conveys information on the biochemical composition of the atherosclerotic plaque, ie, the relative content of lipids (hypoechoic), fibrous tissue (hyperechoic), and calcific deposits (very echogenic with shadowing). A more dishomogeneous echo structure of the plaque is also more often associated with clinically complicated carotid plaques. To date, however, the assessment of plaque density and homogeneity by transcutaneous B-mode imaging remains subjective and qualitative. The aim of this study was to assess whether plaque echodensity and homogeneity might be established on a more objective and quantitative basis by description of the spatial distribution of echo amplitude (referred to as tissue texture) applied to digitized images, obtained with commercially available B-mode transcutaneous imaging systems. A total of 47 B-mode images derived from echotomographic studies in 10 patients were digitized off line. For each region of interest, a set of first-order (mean gray level, standard deviation, skewness, kurtosis: mathematical descriptors of the shape of the frequency distribution of gray-level histogram) and of second-order (entropy, angular moment: mathematical descriptors of the spatial distribution of gray levels within the region of interest) textural parameters were evaluated. The visual, concordant reading by two independent, experienced observers assigned the plaques on the basis of qualitatively assessed echodensity to three groups: "soft" (n = 18), "fibrotic" (n = 20), "calcific" (n = 9). Regarding spatial gray-level distribution, 46 plaques would be separated into "homogenous" (n = 17) and "dishomogeneous" (n = 29). On digitized images, the normalized mean gray level was the most effective first-order textural parameter for distinguishing soft (24.2 +/- 12.4 arbitrary units in a zero to 255 scale) from fibrotic (64.5 +/- 16.4) and calcific plaques (125.3 +/- 24.5), P < 0.01 for all intergroup differences. "Homogeneous" plaques were separated from "heterogeneous" ones on the basis of entropy (5 +/- 1 vs 7.9 +/- 9.7; P < 0.01), whereas the values of angular second moment overlapped (1.542E-3 + 1.334E-3 vs 5.181E-4 +/- 2.5615E-4, P = ns). In conclusion, quantitative texture analysis of ultrasonic images derived from transcutaneous, high-resolution, commercially available B-scan systems is feasible in man and provides a quantitative operator-independent assessment of plaque echodensity and homogeneity.

111 In Platelet Scintigraphy for the Noninvasive Detection of Carotid Plaque Thrombosis

“…32,42 We also found discouraging results in the application of the performed videodensitometric analyses in an attempt to predict plaque histology. Although these analyses are better at the prediction of the presence of "soft," "lipidrich," 34 and therefore possibly vulnerable 15 plaques, and not of thrombosis, this was not the case in our series, with an almost random distribution of blindly measured videodensitometric parameters between fibrolipidic and fibrous plaques. Another consideration is that this technique would still be only indirectly related to the risk of fissuring and thrombosis.…”

“…33 The mean gray level describes the average gray value distribution and allows the objective ultrasonographic assessment of characters described visually as "softness", "fibrosity," and "calcification." 34 In addition, an attempt was made to relate the spatial distribution to dependence among gray levels in an ROI. To quantify the spatial interrelationship of the tonal distribution of echograms, algorithms were applied to an ROI that encompassed the entire plaque (rather than specific, smaller regions within the plaque, as for first-order algorithms).…”

The EGIR-RISC STUDY (The European group for the study of insulin resistance: relationship between insulin sensitivity and cardiovascular disease risk): I. Methodology and Objectives

“…Diastolic frames of CCA, CB and ICA are selected to provide images of the near and far wall intima-media complex. Frames are digitised and analysed by an image analysis system (MIP: Institute of Clinical Physiology, CNR, Pisa, Italy [25]). Lines are drawn along the lumen-intimal and medial-adventitial interfaces, and the IMT is computed as an average of several measurements.…”

Quantitative analysis of ultrasound B-mode images of carotid atherosclerotic plaque: correlation with visual classification and histological examination

“…In a similar study [27], 47 high-quality images were recorded from ten patients and analyzed with four firstorder and two second-order features. Only Mean gray level ( ) and Entropy ( ) distinguished between the classes in echogenicity and structure, respectively.…”