Fractional Moving Blood Volume Measurement Using Power Doppler Ultrasound as an Estimation of Fetal Organ Blood Perfusion

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.

Changes in regional fetal cerebral blood flow perfusion in relation to hemodynamic deterioration in severely growth‐restricted fetuses

“…The first is that FMBV is an indirect estimate of tissue blood perfusion. However, the technique has shown a strong correlation with ‘gold standards’ in experimental conditions16 and we have previously shown that brain FMBV can be estimated reliably and consistently in human fetuses17–19. Our results are consistent with those of Dubiel et al 28, who also reported that growth‐restricted fetuses have increased brain power Doppler signals, although these authors did not evaluate FMBV or the existence of regional variations.…”

“…As described previously19, the regions of interest (ROIs) were delimited offline as follows: frontal, in an anterior mid‐sagittal view of the fetal head, delimited anteriorly by the internal wall of the skull, posteriorly by an imaginary line drawn at 90° at the level of the origin of the anterior cerebral artery and parallel to an imaginary line in the front of the face, and inferiorly by the base of the skull (Figure 1a); complete mid‐cerebral, in a mid‐sagittal plane delimited by the complete internal wall of the fetal skull (Figure 1b); basal ganglia in a mid‐parasagittal view, delimited by the head, body and tail of the caudate nucleus and inferiorly by the lenticular nucleus (Figure 1c), and the cerebellum delimited anteriorly by the base of the cerebellar hemispheres, approximately at the level of the junction of the posterior cerebral arteries with the posterior communicating arteries, and posteriorly by the fetal skull (Figure 1d). Pixels containing color PDU data within the ROIs were used for FMBV calculation according to previously described methodology17–19. The mean FMBV from all 10 images was considered as the representative value for each fetus.…”

“…Blood flow perfusion can be estimated using power Doppler ultrasound (PDU) imaging and fractional moving blood volume (FMBV) measurement, which has acceptable reproducibility and shows a high correlation with real blood perfusion changes16. We previously reported the feasibility and reproducibility of FMBV for studying brain regional blood perfusion in human fetuses17, 18. The aim of this study was to evaluate FMBV estimated in different cerebral regions of fetuses with severe IUGR, and to analyze the development of regional blood perfusion patterns at different stages of fetal hemodynamic deterioration.…”

Two‐dimensional and three‐dimensional Doppler assessment of fetal growth restriction with different severity and onset

“…We are aware of the limitations of this study; placental 3D indices generated by the VOCAL histogram could have been affected by several parameters of the machine such as gain, power, pulse repetition frequency, wall motion filter, signal rise, and persistence . Because of its relative simplicity, low intra‐observer and interobserver variability and vast experience, we preferred to use the VOCAL method for estimating the placental blood flow and did not use additional standardization techniques such as the ‘fractional moving blood volumes in which measurement are scaled to the maximum potential detectable amplitude with 100% blood. Also, we could not use transvaginal transducer for minimizing signal attenuation because of the advanced gestational age.…”

Cervical blood perfusion assessed using power Doppler‐derived estimation of fractional moving blood volume: a reproducibility study

“…Each image was rendered and pixels containing color information within the ROI were selected for analysis (Figure 1c). FMBV was calculated according to the methodology described previously, using a double normalization process19 (Figure 1d).…”