Abstract

Fractional moving blood volume (FMBV) estimated using power Doppler ultrasound (PDU) is a sensitive technique to detect slow blood movement. However, several factors as; depth, attenuation and blood characteristics can affect the PDU signals. The aim of this study was to standardized and validate the FMBV measurement compensating for the factors that can affect the final results, in order to accurate estimate blood movement in a specific region of interest (ROI) of fetal organs as an estimation of blood perfusion. FMBV measurement for the fetal lung blood perfusion was standardized in 29 healthy fetuses at 35-37 weeks of gestation. Clear definition of the ROI in both fetal lungs was proposed. FMBV values were in the range of 27-42% (mean 36.2%) and showed a coefficient of variation of 0.14. No significant differences between the FMBV values obtained from the left and the right lungs, or between cardiac systole and diastole were observed. A phantom experimental study showed good sensitivity for slow blood movement. FMBV was then compared with blood perfusion measurements evaluated with radioactive labeled microspheres (RMS) in the adrenal gland of 5 fetal lambs exposed to severe asphyxia. There was a high correlation between FMBV and RMS (r=0.90, range 0.43-0.99). The reproducibility and agreement analyses showed an intraclass correlation coefficient of 0.92 (95% confidence intervals [CI] 0.78-0.96), and a mean difference between observers of 0.06 (SD, 3.7). Conclusion. The estimation of the fractional moving blood volume measurement using power Doppler ultrasound can be reliable correlated with true fetal organ blood perfusion. FMBV is a reproducible method that can offer valuable information about adaptive fetal blood flow changes in the presence of pregnancy associated complications.

Keywords: Fractional moving blood volume, power Doppler ultrasound, blood perfusion, fetus, validation