Correlation between enhanced intensity of atherosclerotic plaque at contrast-enhanced ultrasonography and density of histological neovascularization.

The feasibility of contrast-enhanced ultrasonography in the assessment of atherosclerotic plaque neovascularization and its relation to histological findings were investigated. Abdominal aortic atherosclerotic plaque model was induced in 25 New Zealand white rabbits by a combination of high cholesterol-rich diet and balloon aortic denudation. Standard and contrast-enhanced ultrasonography was performed at the 16th week of the model induction period. The plaques were classified as echogenic plaques or echolucent plaques according to their echogenicity at standard ultrasonography. The maximum thickness of plaque was measured in the longitudinal section. Time intensity curve was used to quantify the enhanced intensity of the plaque. Animals were euthanized and abdominal aortas were harvested for histological staining of CD31 to evaluate the neovascularization density of atherosclerotic plaque. The results showed that the echolucent plaques had higher enhanced intensity during contrastenhanced ultrasonography and higher neovascularization density at CD31 staining than the echogenic plaques. The enhanced intensity of atherosclerotic plaque and its ratio to lumen were well correlated with histological neovascularization density (r=0.75, P<0.001; r=0.68, P<0.001, respectively). However, the maximum thickness of plaque was not correlated with neovascularization density (r=0.235, P=0.081). These findings demonstrated that the enhanced intensity in the plaque and ratio of enhanced intensity to that in the lumen of abdominal aorta may be more accurate in the evaluation of plaque neovascularization than maximum thickness. Our study indicates that contrast-enhanced ultrasonography provides us a reliable method for the evaluation of plaque neovascularization.