To establish an objective method for assessment of carotid artery lesions depicted on B-mode ultrasonography, semiquantitative findings, analysed and evaluated by computer, were compared with the histological findings of endarterectomy specimens. Seven carotid artery lesions in 5 patients with carotid stenosis were examined preoperatively by B-mode ultrasonography, and these images were incorporated into a computer by a scanner using Adobe Photoshop software. The echogenicity of all pixels included in the lesion and optional areas of both muscle tissue and the vascular lumen was measured, and the mean values and histograms of echogenicity from zero to 255 density levels were determined. Based on the shape of the histogram, the lesions were classified into 3 types: hyperechoic (H) and echolucent (L) types, which showed a monopeak or skewed distribution curve but in which the curve did not reach the abscissa on at least one side, and the mixed (M) type, in which the curve extended near the abscissae on both sides. The H and M types, which have an adjusted mean echogenic value greater than the mean plus 1 standard deviation of muscle tissue, showed calcification or organized hyaline fibrosis. In contrast, the L type showed atheroma consisting of lipid deposition, necrotic tissue, cellular infiltration, and hemorrhage. These findings indicated that the histogram and echogenicity of carotid artery lesions analyzed by a computer could provide objective evaluation comparable to visual subjective assessment of the lesion.
