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Three-Dimensional Ultrasonographic Bladder Volume Measurement

Reliability of the Virtual Organ Computer-Aided Analysis Technique Using Different Rotation Steps

Department of Obstetrics and Gynecology (C.S., T.S., H.S.) and Epidemiology Unit (A.G.), Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand.

Address correspondence to Chitkasaem Suwanrath, MD, MMedSci, Department of Obstetrics and Gynecology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, 90110, Thailand. E-mail: schitkas{at}medicine.psu.ac.th

Objective. The purpose of this study was to investigate the reliability of Virtual Organ Computer-Aided Analysis (VOCAL; GE Healthcare, Kretztechnik, Zipf, Austria) using the 4 standard rotation steps to measure the bladder volume with 3-dimensional (3D) ultrasonography. Methods. Using the 4 standard rotation steps of VOCAL, 2 independent observers made 3D volume measurement data sets from the urinary bladder (n = 180). Sets of 30, 20, 12, and 6 planes were obtained from the sequential rotations of 6°, 9°, 15°, and 30°, respectively. The internal contours of the bladders were determined manually. Reliability was evaluated with the intraclass correlation coefficient (ICC), and Bland-Altman plots were generated to examine bias and agreement. One-way analysis of variance was used to compare bladder volume measurements between the angles. P < .05 was considered statistically significant. Results. A high degree of reliability was observed between pairs of different rotation angles (ICC, 0.994–0.999). There was good agreement between all pairs of different rotation angles, with percentages of the mean difference ranging from –0.9% to 1.8%. No significant difference was found for bladder volume measurements by the VOCAL technique with varying rotation steps. Intraobserver and interobserver reliabilities were high (ICC, 0.994–0.998). Conclusions. Urinary bladder volume measurement by the VOCAL technique using different rotation steps is highly reliable. A plane rotation of 30° produces the fastest result.

Key Words: reliability • rotation angle • 3-dimensional ultrasonography • Virtual Organ Computer-Aided Analysis

Abbreviations: ANOVA, analysis of variance • CI, confidence interval • ICC, intraclass correlation coefficient • 3D, 3-dimensional • 3DUS, 3-dimensional ultrasonography • VOCAL, Virtual Organ Computer-Aided Analysis