OC36: Liver‐to‐kidney volume ratio by Virtual Organ Computer‐aided AnaLysis (VOCAL)
Andrejz Lysikiewicz, Dev Maulik, Oded Langer, A. Balcer · Ultrasound in Obstetrics and Gynecology · 2007
To evaluate reproducibility of fetal liver-to-kidney volume ratio in assessment of fetal growth restriction using Virtual Organ Computer-aided AnaLysis (VOCAL). Volume scans of 50 pregnant women at gestational ages 18 to 26 weeks were analyzed using 4D-view software to measure fetal liver and kidney volume. Three independent observers measured fetal liver volumes with the horizontal axis centered at the bifurcation of the hepatic vein and fetal kidney volumes at the renal pelvis of the proximal kidney. Six sections with 30° rotations between scanned planes were used. Each observer performed three independent measurements of the fetal liver and kidney volume on each patient. A total of 900 measurements were performed on the volume scans of 50 patients. Observers were unaware of each other's measurement results. Intraobserver variability was determined by coefficient of variation of measurements within individual cases. Similarly, for each case, interobserver variability was calculated as a ratio between mean SD and overall mean of measurements obtained by all observers (overall coefficient of variation). The fetal liver-to-kidney volume ratios fell within a range of 1.16–12.82, with a mean value of 5.05 and SD of 2.93. Intraobserver variability expressed as mean coefficient of variation within individual cases was 0.20 (CI + 0.018 at P = 0.05). Interobserver variability expressed as coefficient of variation between three observers was 0.53 (CI + 0.12 at P = 0.05). Liver-to-kidney ratio VOCAL yielded variability of 0.12 (intraobserver) and 0.21 (interobserver). This index is less gestational age dependent than individual values and therefore more appropriate for assessment of fetal growth.