Repeatability and reproducibility of fetal cardiac ventricular volume calculations using spatiotemporal image correlation and virtual organ computer-aided analysis

Objective. The objective of this study was to quantify the repeatability and reproducibility of fetal cardiac ventricular volumes obtained using spatiotemporal image correlation (STIC) and Virtual Organ Computer-Aided Analysis (VOCAL; GE Healthcare, Kretztechnik, Zipf, Austria). Methods. A technique was developed to compute ventricular volumes using the subfeature Contour Finder: Trace. Twenty-five normal pregnancies were evaluated for the following: (1) to compare the coefficient of variation (CV) of ventricular volumes obtained using 15° and 30° rotation; (2) to compare the CV between 3 methods of quantifying ventricular volumes: (a) Manual Trace, (b) Inversion Mode, and (c) Contour Finder: Trace; and (3) to determine repeatability by calculating agreement and reliability of ventricular volumes when each STIC was measured twice by 3 observers. Reproducibility was assessed by obtaining 2 STICs from each of 44 normal pregnancies. For each STIC, 2 ventricular volume calculations were performed, and agreement and reliability were evaluated. Additionally, measurement error was examined. Results. (1) Agreement was better with 15° rotation than 30° (15° : 3.6%; 95% confidence interval [CI], 3.0%-4.2%; versus 30° : 7.1%; 95% CI, 5.8%-8.6%; P < .001); (2) ventricular volumes obtained with Contour Finder: Trace had better agreement than those obtained using either Inversion Mode (Contour Finder: Trace: 3.6%; 95% CI, 3.0%-4.2%; versus Inversion Mode: 6.0%; 95% CI, 4.9%-7.2%; P < .001) or Manual Trace (10.5%; 95% CI, 8.7%-12.5%; P < .001); (3) ventricular volumes were repeatable with good agreement and excellent reliability for both intraobserver and interobserver measurements; and (4) ventricular volumes were reproducible with negligible differences in agreement and good reliability. In addition, bias between STIC acquisitions was minimal (<1%; mean percent difference, -0.4%; 95% limits of agreement, -5.4%-5.9%). Conclusions. Fetal echocardiography using STIC and VOCAL allows repeatable and reproducible calculation of ventricular volumes with the subfeature Contour Finder: Trace.