Comparison of superb microvascular imaging to conventional color Doppler ultrasonography in depicting renal cortical microvasculature.

PURPOSE: The aim of the study was to compare Superb Microvascular Imaging (SMI) to conventional color Doppler ultrasonography (CDUS) and power Doppler ultrasonography (PDUS) in depicting kidney cortical microvasculature.

METHODS: Using 3.5 MHz curve-linear array ultrasound transducer and manufacturer recommended color Doppler settings (Canon Medical Systems) for KIDNEY sonography, we performed kidney CDUS, PDUS, and SMI in 20 healthy adults (10 man and 10 women, mean age 27 years). Color Doppler signals in all color Doppler images were quantified by counting color pixel intensity, calculating area ratio of color to total region of interest (AR), and measuring distance of cortical end vessel to the kidney capsule. We used one-way analysis of variance (ANOVA) and post-hoc to test the difference in color pixel intensity, AR, and distance of cortical end vessel to the kidney capsule among SMI, CDUS, and PDUS and in all paired groups.

RESULTS: The differences in color pixel intensity, AR, and distance of cortical end vessel to the kidney capsule were significant among CDUS, PDUS, and SMI, as well as in all paired groups (P < 0.001). Color pixel intensity and AR in SMI were significantly higher than CDUS and PDUS (p < 0.001). The distance of cortical end vessel to the kidney capsule in SMI was significantly less than in CDUS and PDUS (p < 0.001). Inter- and intra-observer reliability of quantifying color Doppler images was good (Intraclass correlation coefficient: 0.79-0.92).

CONCLUSION: Our results suggest that SMI seems more sensitive than CDUS and PDUS in depicting kidney cortical microvasculature.