Gordon N. Stevenson

Three-Dimensional Power Doppler Ultrasonography for Diagnosing Abnormally Invasive Placenta and Quantifying the Risk.

OBJECTIVE: To test an objective ultrasound marker for diagnosing the presence and severity of abnormally invasive placenta. METHODS: Women at risk of abnormally invasive placenta underwent a three-dimensional power Doppler ultrasound scan. The volumes were examined offline by a blinded observer. The largest area of confluent three-dimensional power Doppler signal (Area of Confluence [Acon], cm2) at the uteroplacental interface was measured and compared in women subsequently diagnosed with abnormally invasive placenta and women in a control group who did not have abnormally invasive placenta. Receiver operating characteristic curves were plotted for prediction of abnormally invasive placenta and abnormally invasive placenta requiring cesarean hysterectomy. RESULTS: Ninety-three women were recruited. Results were available for 89. Abnormally invasive placenta was clinically diagnosed in 42 women; 36 required hysterectomy and had abnormally invasive placenta confirmed histopathologically. Median and interquartile range for Acon was greater for abnormally invasive placenta (44.2 [31.4–61.7] cm2) compared with women in the control group (4.5 cm2 [2.9–6.6], P<.001) and even greater in the 36 requiring hysterectomy (46.6 cm2 [37.2–72.6], P<.001). Acon rose with histopathologic diagnosis: focal accreta (32.2 cm2 [17.2–57.3]), accreta (59.6 cm2 [40.1–89.9]), and percreta (46.6 cm2 [37.5–71.5]; P<.001 analysis of variance for linear trend). Receiver operating characteristic analysis for prediction of abnormally invasive placenta revealed that with an Acon of 12.4 cm2 or greater, 100% sensitivity (95% confidence interval [CI] 91.6–100) could be obtained with 92% specificity (95% CI 79.6–97.6); area under the curve is 0.99 (95% CI 0.94–1.0). For prediction of abnormally invasive placenta requiring hysterectomy, 100% sensitivity (95% CI 90.3–100) can be obtained with an Acon of 17.4 cm2 or greater with 87% specificity (95% CI 74.7–94.5; area under the curve 0.98 [0.93–1.0]). CONCLUSION: The marker Acon provides a quantitative means for diagnosing abnormally invasive placenta and assessing severity. If further validated, subjectivity could be eliminated from the diagnosis of abnormally invasive placenta. LEVEL OF EVIDENCE: II

Influence of power Doppler gain setting on Virtual Organ Computer-aided AnaLysis indices in vivo: can use of the individual sub-noise gain level optimize information?

To demonstrate the influence of gain setting on the calculated Virtual Organ Computer‐aided AnaLysis (VOCAL™) three‐dimensional (3D) indices and define a point, the sub‐noise gain (SNG), at which maximum information is available without noise artifact.

Monitoring of Cerebrovascular Reactivity for Determination of Optimal Blood Pressure in Preterm Infants

OBJECTIVE To define levels of mean arterial blood pressure (MABP) where cerebrovascular reactivity is strongest in preterm infants (ie, optimal MABP, or MABPOPT) and correlate deviations from MABPOPT with mortality and intraventricular hemorrhage (IVH). STUDY DESIGN A total of 60 preterm infants born at median gestational age 26 ± 2 weeks (23 ± 2 to 32 ± 1) with indwelling arterial catheter were studied at a median 34 hours (range 5-228) of age. Tissue oxygenation heart rate (HR) reactivity index, which estimates cerebrovascular reactivity, was calculated as the moving correlation coefficient between slow waves of tissue oxygenation index, measured with near-infrared spectroscopy, and HR. MABPOPT was defined by dividing MABP into 2-mm Hg bins and averaging the tissue oxygenation HR reactivity index within those bins. A measurement of divergence from MABPOPT was calculated as the absolute difference between mean MABP and mean MABPOPT. RESULTS Individual MABPOPT was defined in 81% of the patients. A measurement of divergence from MABPOPT was greater in those patients who died (mean 4.2 mm Hg; 95% CI 3.33-4.96) compared with those who survived (mean 2.1 mm Hg; 95% CI 1.64-2.56), P = .013. Patients who had MABP lower than MABPOPT by 4 mm Hg or more had a greater rate of mortality (40%) than those with MABP close to or above MABPOPT (13%), P = .049. Patients with MABP greater than MABPOPT by 4 mm Hg had greater IVH scores, P = .042. CONCLUSIONS Continuous monitoring of cerebrovascular reactivity allows the determination of MABPOPT in preterm neonates. Significant deviation below MABPOPT was observed in infants who died. Deviation of MABP above optimal level was observed in infants who developed more severe IVH.

Measurement of spiral artery jets: general principles and differences observed in small-for-gestational-age pregnancies

To investigate whether the jets of blood from the mouths of the spiral arteries could be measured reliably, as well as their relationship with the uterine artery (UtA) and any differences in small‐for‐gestational‐age (SGA) pregnancies.

3-D Ultrasound Segmentation of the Placenta Using the Random Walker Algorithm: Reliability and Agreement.

Volumetric segmentation of the placenta using 3-D ultrasound is currently performed clinically to investigate correlation between organ volume and fetal outcome or pathology. Previously, interpolative or semi-automatic contour-based methodologies were used to provide volumetric results. We describe the validation of an original random walker (RW)-based algorithm against manual segmentation and an existing semi-automated method, virtual organ computer-aided analysis (VOCAL), using initialization time, inter- and intra-observer variability of volumetric measurements and quantification accuracy (with respect to manual segmentation) as metrics of success. Both semi-automatic methods require initialization. Therefore, the first experiment compared initialization times. Initialization was timed by one observer using 20 subjects. This revealed significant differences (p < 0.001) in time taken to initialize the VOCAL method compared with the RW method. In the second experiment, 10 subjects were used to analyze intra-/inter-observer variability between two observers. Bland-Altman plots were used to analyze variability combined with intra- and inter-observer variability measured by intra-class correlation coefficients, which were reported for all three methods. Intra-class correlation coefficient values for intra-observer variability were higher for the RW method than for VOCAL, and both were similar to manual segmentation. Inter-observer variability was 0.94 (0.88, 0.97), 0.91 (0.81, 0.95) and 0.80 (0.61, 0.90) for manual, RW and VOCAL, respectively. Finally, a third observer with no prior ultrasound experience was introduced and volumetric differences from manual segmentation were reported. Dice similarity coefficients for observers 1, 2 and 3 were respectively 0.84 ± 0.12, 0.94 ± 0.08 and 0.84 ± 0.11, and the mean was 0.87 ± 0.13. The RW algorithm was found to provide results concordant with those for manual segmentation and to outperform VOCAL in aspects of observer reliability. The training of an additional untrained observer was investigated, and results revealed that with the appropriate initialization protocol, results for observers with varying levels of experience were concordant. We found that with appropriate training, the RW method can be used for fast, repeatable 3-D measurement of placental volume.

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 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.

Use of four-dimensional analysis of power Doppler perfusion indices to demonstrate cardiac cycle pulsatility in fetoplacental flow.

The aim of this study is to quantify fetoplacental cardiac cycle variation in virtual organ computer-aided analysis (VOCAL) power Doppler (PD) indices by novel application of spatio-temporal imaging correlation (STIC). We recruited 25 healthy women (20-34 weeks gestation) with uncomplicated, viable singleton pregnancies with anterior placentae. Three four-dimensional (4-D) STIC PD datasets of the fetoplacental circulation were obtained above the placental cord insertion. The vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) were calculated offline using a standardized spherical sonobiopsy technique for all frames of the cardiac cycle. Clear maximum (systole) and minimum (diastole) values with progressive fluctuation were seen in the majority of datasets (VI 66/75 [88%]; FI 58/75 [77%]; VFI 68/75 [91%]). Variation from mean was: VI ± 3.33% (0.34%-9.69%); VFI ± 3.46% (0.27%-10.02%); FI ± 0.74% (0.14%-1.60%). All indices were significantly higher in systole than diastole (p < 0.001). Mean systolic:diastolic ratios were: VI 1.07 (SD 0.06), FI 1.01 (SD 0.01) and VFI 1.07 (SD 0.06). Intraclass correlation coefficients (ICCs) for the frames ascribed to systole and diastole and to the mean value across the cardiac cycle of the indices (95% confidence interval [CI]) were: systole VI 0.91 (0.83-0.96), FI 0.85 (0.72-0.92), VFI 0.92 (0.85-0.96); diastole VI 0.91 (0.84-0.96), FI 0.84 (0.71-0.92), VFI 0.92 (0.86-0.96); mean VI 0.91 (0.84-0.96), FI 0.84 (0.72-0.92), VFI 0.92 (0.86-0.96). There is clear cardiac cycle variation in VOCAL indices of fetoplacental blood flow, establishing the need to control for phase of the cardiac cycle, and raising the possibility of future 4-D evaluation of vascular flow change or impedance.

Inapplicability of fractional moving blood volume technique to standardize Virtual Organ Computer-aided AnaLysis indices for quantified three-dimensional power Doppler.

To determine whether the technique of fractional moving blood volume (FMBV) is applicable to Virtual Organ Computer‐aided AnaLysis II (VOCAL II™)‐based indices to quantify three‐dimensional power Doppler ultrasound (3D‐PDU) by investigating the effect of gain level on the indices measured at a possible reference point for standardization.

OP10.09: A novel semi‐automated (SA) technique for 3D ultrasound measurement of placental volume

Objectives: 3D power Doppler angiography (3DPD) is used to quantify the vascularity of an organ. Analysis of a stored dataset can be reliable but few studies have considered the reliability of data acquisition. Our aim was to investigate the intraand interobserver reproducibility of serial acquisition of 3DPD data of the whole placenta from women at 12 and 20 weeks gestation. We hypothesised a high level of agreement would exist. Methods: 20 low risk women with an uncomplicated, viable singleton pregnancy were scanned (Voluson 730 Expert) at two gestational age groups: 12+0 to 13+6 and 19+0 to 21+6 weeks. 3DPD whole placental datasets were acquired by two observers: the 1st made two acquisitions and the 2nd a single acquisition resulting in 3 datasets per patient and 120 overall. These were analysed by a single observer who used VOCAL (A plane, 9 degree steps) to define the VI, FI and VFI. The reliability of these measurements was assessed by intraclass correlation coefficients (ICC + 95% CI) and Bland-Altman plots. The presence of systematic bias within and between observers was also analysed. Results: Mean BMI was 24 (SD 5) in each group. Interobserver ICC was highest for the VI 0.81 (0.59–0.92) and VFI 0.76 (0.48–0.90). ICC for FI showed only moderate correlation at 0.55 (0.18–0.79). Bland Altman plots showed the FI to be the most reliable vascular index however at ±15% (expressed as a % of the mean) and ±17% at 12 weeks and ±9% and ±10% at 20 weeks for intraobserver and interobserver differences respectively. Intraand inter-observer differences were greater for VI at ±40% and ±70% respectively at 20 weeks. There was no bias between datasets. Conclusions: This study demonstrates that 3D can be used to reliably acquire power Doppler data from the whole placenta at 12 and 20 weeks gestation. Previous studies had only addressed the reliability of data analysis. Prospective studies are now required to identify if 3DPD is sensitive enough to identify patients with early-onset placental dysfunction.

Automatic 3D ultrasound segmentation of the first trimester placenta using deep learning

Placental volume measured with 3D ultrasound in the first trimester has been shown to be correlated to adverse pregnancy outcomes. This could potentially be used as a screening test to predict the “at risk” pregnancy. However, manual segmentation whilst previously shown to be accurate and repeatable is very time consuming and semi-automated methods still require operator input. To generate a screening tool, fully automated placental segmentation is required. In this work, a deep convolutional neural network (cNN), DeepMedic, was trained using the output of the semi-automated Random Walker method as ground truth. 300 3D ultrasound scans of first trimester placentas were used to train, validate and test the cNN. Compared against the semi-automated segmentation, resultant median (1st Quartile, 3rd Quartile) Dice Similarity Coefficient was 0.73 (0.66, 0.76). The median (1st Quartile, 3rd Quartile) Hausdorff distance was 27 mm (18 mm, 36 mm). We present the first attempt at using a deep cNN for segmentation of 3D ultrasound of the placenta. This work shows that feasible results compared to ground truth were obtained that could form the basis of a fully automatic segmentation method.