Evaluation of fetal regional cerebral blood perfusion using power Doppler ultrasound and the estimation of fractional moving blood volume

Objective: To standardize the evaluation of regional fetal brain blood perfusion, using power Doppler ultrasound (PDU) to estimate the fractional moving blood volume (FMBV) and to evaluate the reproducibility of this estimation. Methods: Brain blood perfusion was evaluated in 35 normally grown fetuses at 28-30 weeks of gestation, using PDU. The following cerebral regions were included in the PDU color box: anterior sagittal, complete sagittal, basal ganglia, and cerebellar. Ten consecutive good-quality images of each anatomical plane were recorded and the delimitation of the region of interest (ROI) was performed off-line. FMBV was quantified in the ROI of all images and the mean considered as the final value. Differences between regions, variability, reproducibility and agreement between observers were assessed. Results: Power Doppler images of the described anatomical planes were obtained in all cases, regardless of fetal position. The median time for the acquisition of the images was 7 (range 4-12) min. Mean (range) FMBV values were: anterior sagittal, 16.5 (10.7-22.8)%, inter-patient coefficient of variation (CV) 0.22; complete sagittal, 13.5 (8.8-16.1)%, CV 0.27; basal ganglia, 18.3 (10.7-27.6)%, CV 0.27; and cerebellar, 6.6 (3.0-11.0)%, CV 0.38. There were statistically significant differences in FMBV between cerebellar and complete sagittal ROIs with the frontal and basal ganglia regions. Reproducibility analyses showed an intraclass correlation coefficient of 0.91 (95% CI 0.67-0.97) and an interclass correlation coefficient of 0.87 (95% CI 0.70-0.94). Interobserver agreement showed a mean difference between observers of -0.2 (SD 2.7) with 95% limits of agreement -5.6 to 5.2. Conclusions: When the regions of interest are well defined, the FMBV estimate offers a method to quantify blood flow perfusion in different fetal cerebral areas. There appear to be regional differences in FMBV within the fetal brain.