Comparison of Superb Microvascular Imaging and Conventional Doppler Imaging Techniques for Evaluating Placental Microcirculation: A Prospective Study

BACKGROUND: Superb microvascular imaging (SMI) is a new blood flow imaging technique used to evaluate microvascular blood flow. This study evaluated whether SMI was superior to color Doppler flow imaging (CDFI) for evaluating placental microcirculation. MATERIAL/METHODS: This prospective study included pregnant women in their third trimester who were evaluated at General Hospital of Hebei Province from February to June 2017. The distribution of vascular patterns, including pulsatility index (PI), resistance index (RI), S/D, time average velocity (TAV), and vessels per unit area, were evaluated by SMI and CDFI. RESULTS: This study evaluated 110 pregnant women of mean age 29.53 years. SMI and CDFI yielded statistically significant differences in PI (0.76 vs. 0.62), RI (0.71 vs. 0.47), S/D (2.23 vs. 1.71), TAV (14.35 vs. 22.45), and vessels per unit area (0.26 vs. 0.05) (P<0.001 each). The weight of the pregnant women correlated positively with RI (P=0.048) and negatively with vessels per unit area (P=0.040) as determined by SMI. Weeks of gestation correlated negatively correlated with PI (P=0.008), RI (P=0.004), S/D (P=0.015), and vessels per unit area (P=0.014) by CDFI, and positively with RI (P<0.001) and S/D (P=0.001) by SMI. The results of stratified comparisons of CDFI and SMI based on age, weight, and gestational weeks were consistent overall. CONCLUSIONS: SMI, which has a higher rate of placental vascularity, a clearer display of capillaries, a greater sensitivity to low flow, and an advantage in displaying microcirculation of the placenta, can serve as a new and effective method of evaluating placental blood flow.