Evaluation of carotid plaque vulnerability by contrast-enhanced ultrasound and superb microvascular imaging

Objective To observe the plaque surface morphology and neo-vascularization within the plaque using superb microvascular imaging(SMI)and contrast-enhanced ultrasound(CEUS), and to compare the correlation and consistency of the two technologies based on making clinical diagnosis of symptomatic carotid artery plaque as the standard. Methods A total of 92 patients undergoing carotid ultrasonography in Beijing Tiantan Hospital from August 2016 to October 2017 were recruited, including 61 males and 31 females, aged(63.5 ± 7.7)years(range, 42-80 years.A total of 105 plaques were found.According to whether or not to have plaque-induced ipsilateral ischemic symptoms, patients were divided double-blindly into the symptom group and the non-symptom group.The features of plaque(including surface morphology and neo-vascularization)were recorded.The ultrasonographic findings were chi-squarely tested. Results There were statistically significant differences in the surface morphology and enhancement degree of CEUS between carotid artery plaque-induced ischemic symptom group and the non-symptom group(χ2=6.865, P=0.032; χ2=22.494, P<0.001). The SMI-detected surface morphology and neo-vascularization had statistically significant differences between the two groups(χ2=10.367, P=0.006; χ2=8.186, P=0.041). The correlations of plaque surface morphology(r=0.856, P<0.001)and diagnostic consistency(r=0.802, P<0.001)between SMI and CEUS were higher.In the symptom group, SMI-showed plaque fissures and small surface pitting were in 33.9%(20/59)of patients, and CEUS-showed plaque fissures and small surface pitting were in 25.4%(15/59)of patients.And SMI had a better detection rate of slight and irregular appearances on plaque surface.Taking the first grade of the plaque surface as the standard, CEUS showed a sensitivity of 42.4% and specificity of 80.4% for detecting symptomatic plaques, and SMI showed a sensitivity of 54.2% and specificity of 76.1%.The two methods had similar specificity, and SMI had a slightly higher sensitivity than did CEUS.CEUS and SMI had a good correlation of plaque neo-vascularization(r=0.802, P<0.001)and a moderate diagnostic consistency(r=0.539, P<0.001). Taking the enhancement level of 2 as the standard, CEUS showed a sensitivity of 75.8% and specificity of 67.4% for detecting the symptomatic plaque, and SMI showed a sensitivity of 58.6% and specificity of 69.5%.The two methods had similar specificity, and CEUS had a higher sensitivity than did SMI. Conclusions SMI and CEUS have a good consistency for detecting plaque surface morphology.SMI and CEUS are more correlated with plaque-induced symptoms than is two-dimensional ultrasound.The SMI has a higher display rate and repeatability than does CEUS for detecting the small fissures and the surface features of plaques.Compared with SMI-detected neo-vascularization, the degree of CEUS enhancement is more correlated with the symptoms.The specificity of CEUS and SMI is similar, and the sensitivity of CEUS is higher than that of SMI. Key words: Carotid artery thrombosis; Ultrasonography