Original Research n Technical Developments A Technique for the Estimation of Fractional Moving Blood Volume by Using Three-dimensional Power Doppler US

Purpose: To (a) demonstrate an image-processing method that can automatically measure the power Doppler signal in a three-dimensional (3D) ultrasonographic (US) volume by using the location of organs within the image and (b) compare 3D fractional moving blood volume (FMBV) results with commonly used, unstandardized measures of 3D power Doppler by using the human placenta as the organ of interest. Materials and Methods: This is a retrospective study of scans obtained as part of a prospective study of imaging placental biomarkers with US, performed with ethical approval and written informed consent. One hundred forty-three consecutive female patients were examined by using an image-processing technique. Three-dimensional FMBV was measured on the vasculature from the uteroplacental interface to a depth 5 mm into the placenta by using a normalization volume 10 mm outside the uteroplacental interface and compared against the Virtual Organ Computer-aided AnaLysis (VOCAL; GE Healthcare, Milwaukee, Wis) vascularization flow index (VFI). Intra-and interobserver variability was assessed in a subset of 18 volumes. Wilcoxon signed rank test and intraclass correlation coefficients were used to assess measurement repeatability. Results: The mean 3D FMBV value 6 standard deviation was 11.78% 6 9.30 (range, 0.012%-44.16%). Mean VFI was 2.26 6 0.96 (range, 0.15-6.06). Linear regression of VFI versus FMBV produced an R2 value of 0.211 and was significantly different in distribution (P < .001). Intraclass correlation coefficient analysis showed higher FMBV values than VFI for intra-and interobserver variability; intraobserver values were 0.95 for FMBV (95% confidence interval [ CI]: 0.90, 0.98) versus 0.899 for VFI (95% CI: 0.78, 0.96), and interobserver values were 0.93 for FMBV (95% CI: 0.82, 0.97) versus 0.67 for VFI (95% CI: 0.32, 0.86). Conclusion: The extension of an existing two-dimensional standardized power Doppler measurement into 3D by using an imageprocessing technique was shown in an in utero placental study. Three-dimensional FMBV and VFI produced significantly different results. FMBV performed better than VFI in repeatability studies. Further studies are needed to assess accuracy against a reference standard. (C) RSNA, 2014