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

This paper presents a quantitative comparison of three types of information available for 52 patients scheduled for carotid endarterectomy: subjective classification of the ultrasound images obtained during scanning before op eration, first- and second-order statistical features extracted from region s of the plaque in still ultrasound images from three orthogonal scan plane s and finally a histological analysis of the surgically removed plaque. The quantitative comparison was made with the linear model and with separation of the available data into training and test sets. The comparison of subje ctive classification with features from still ultrasound images revealed an overall agreement of 60% for classification of echogenicity and 70% for cl assification of structure. Comparison of the histologically determined rela tive volume of soft materials with features from the still images revealed a correlation coefficient of r = -0.42 (p = 0.002), for mean echogenicity o f the plaque region. The best performing feature was of second order and de noted Contrast (r = -0.5). Though significant, the latter correlation is pr obably not strong enough to be useful for clinical prediction of relative v olume of soft materials for individual patients. Reasons for this is discus sed in the paper, together with suggestions for improvements.