A technique for the estimation of fractional moving blood volume by using three-dimensional power Doppler US

Abstract

PURPOSE: To (a) demonstrate an image-processing method that can automatically measure the power Doppler signal in a three-dimensional ( 3D three-dimensional ) ultrasonographic (US) volume by using the location of organs within the image and (b) compare 3D three-dimensional fractional moving blood volume ( FMBV fractional moving blood volume ) results with commonly used, unstandardized measures of 3D three-dimensional 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 fractional moving blood volume 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 Virtual Organ Computer-aided AnaLysis ; GE Healthcare, Milwaukee, Wis) vascularization flow index ( VFI vascularization flow index ). 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 three-dimensional FMBV fractional moving blood volume value ± standard deviation was 11.78% ± 9.30 (range, 0.012%-44.16%). Mean VFI vascularization flow index was 2.26 ± 0.96 (range, 0.15-6.06). Linear regression of VFI vascularization flow index versus FMBV fractional moving blood volume produced an R(2) value of 0.211 and was significantly different in distribution (P < .001). Intraclass correlation coefficient analysis showed higher FMBV fractional moving blood volume values than VFI vascularization flow index for intra- and interobserver variability; intraobserver values were 0.95 for FMBV fractional moving blood volume (95% confidence interval [ CI confidence interval ]: 0.90, 0.98) versus 0.899 for VFI vascularization flow index (95% CI confidence interval : 0.78, 0.96), and interobserver values were 0.93 for FMBV fractional moving blood volume (95% CI confidence interval : 0.82, 0.97) versus 0.67 for VFI vascularization flow index (95% CI confidence interval : 0.32, 0.86). CONCLUSION: The extension of an existing two-dimensional standardized power Doppler measurement into 3D three-dimensional by using an image-processing technique was shown in an in utero placental study. Three-dimensional FMBV fractional moving blood volume and VFI vascularization flow index produced significantly different results. FMBV fractional moving blood volume performed better than VFI vascularization flow index in repeatability studies. Further studies are needed to assess accuracy against a reference standard.