Objective To observe the direction of lymph node perfusion and microvascular distribution by high frame rate contrast-enhanced ultrasound combined with microflow enhancement mode

and to evaluate its application value in distinguishing benign and malignant superficial lymph nodes of different sizes. Methods A total of 121 patients admitted to the General Hospital of PLA for superficial abnormal lymph nodes were selected. Conventional frame rate and high frame rate contrast-enhanced ultrasound were performed on the lymph nodes of the above-mentioned patients. After the CEUS was performed

conventional frame rate and high frame rate contrast-enhanced arterial phase images were obtained

and MFE function was activated to play and save dynamic images at 1/2 ~ 1/3 speed. The enhancement uniformity and perfusion direction of benign and malignant lymph nodes of different sizes were analyzed under two contrast frame rates. Results There were significant differences in overall enhancement uniformity between benign and malignant lymph nodes (χ2=14.546 p=0.000). When the maximum diameter of lymph nodes was larger than 2cm

there was significant difference in enhancement uniformity among different size groups (χ2= 9.614p =0.002). For benign lymph nodes

H-CEUS showed a higher proportion of centrifugal fill-in perfusion than C-CEUS (80.7% vs 61.4%;)

the difference was statistically significant (χ2=5.160 p=0.023). For metastatic lymph nodes

H-CEUS also showed a higher percentage of centripetal perfusion than C-CEUS (79.7% vs 62.5%)

with statistical significance (χ2=4.600 p=0.032). ROC curve showed that with the decrease of lymph node volume

the accuracy of H-CEUS diagnosis was improved compared with C-CEUS

especially when the maximum diameter of lymph node was between 0.5 and 1cm

the areas under ROC curve were 0.817 (P=0.001) and 0.669 (P=0.088)

respectively. Conclusion H-CEUS combined with MFE mode can better display the vascular structure and perfusion direction in lymph nodes

so as to accurately reflect the microcirculation difference between benign and malignant lymph nodes. Especially for small lymph nodes

H-CEUS has better diagnostic ability than C-CEUS.