Placental Pulsatility: Quantitative Assessment of Placental Bed Vasculature by 2-Dimensional Doppler Cine Imaging

Vascular resistance is known to be one of the determinants of pulsatile flow. This study aimed to investigate whether quantitative 2-dimensional Doppler ultrasound can capture and evaluate the pulsatility within the placental bed vasculature.

The placental bed vasculature was imaged by directional power Doppler ultrasound. Ten-second cine clips were recorded by using standardized machine settings. A region of interest with a prominent Doppler signal in the uteroplacental interface was analyzed for the percentage of vascularity to generate a time-vascularity waveform. A vascular pulsatility index representing variation over the cardiac cycle was calculated by the ratio of the systolic-diastolic difference in vascularity to the mean vascularity. The acquisitions were repeated with 6 different pulse repetition frequencies (PRFs) and 3 wall motion filter (WMF) settings to evaluate their impact on the Doppler measurements.

Ten sets of cine clips were analyzed for this study. The pulsatile nature of the vascularity was readily apparent in each cine clip. The measured time-vascularity waveforms showed uniform cyclic variation in vascularity over the cardiac cycle, with systolic vascularity significantly higher than diastolic vascularity at each combination of PRF and WMF (P < .05). A gradual increase in the vascular pulsatility index was observed with an increasing PRF or WMF. Normalization of systolic-to-diastolic measurement provided a stable vascular assessment across the range of PRFs.

Doppler cine clips provide a dynamic representation of the placental bed vasculature and a novel analytic approach to quantitatively evaluating the pulsatility of this critical vascular network. Further work is warranted to explore the reproducibility and clinical potential of this approach.