Atheromatous plaque: quantitative analysis of the echogenicity of different layers.

INTRODUCTION AND OBJECTIVES Echographic studies of the composition of atheromatous plaque make use of the median gray level, which provides an overall measure of echogenicity. We propose adding an additional dimension to this approach by dividing the lesion into layers and generating a curve that shows the variation in echolucency with depth. METHODS Femoral and carotid plaque in asymptomatic patients was investigated using both the median gray level and new layer METHODS Interobserver variability was assessed for both METHODS Three risk factors were studied: age, gender and smoking status. Differences in echogenicity-depth curves between different groups were assessed using two-way ANOVA. RESULTS The two methods gave similar results for the mean echogenicity of carotid and femoral plaque. Echogenicity increased as a function of depth (r=0.96; P< .001). With the median gray level method, none of the risk factors produced a change in echogenicity. However, with the layer method, the echogenicity of femoral plaque was found to increase with age (P< .001), though gender had no effect. Moreover, the echogenicity of superficial layers was less in smokers than nonsmokers (P< .01). In carotid plaque, echogenicity increased with age (P< .01) and was higher in men (P< .01). The echogenicity of deep plaque was greater in smokers than nonsmokers (P< .05). The reproducibility of the two methods was similar. CONCLUSIONS The layer method was more effective than the median gray level method for identifying the effect of age, sex and smoking status on the echogenicity of atheromatous plaque.