Ovarian Volume Measurements in Mice With High-Resolution Ultrasonography

Abstract

Objective. The aim of our study was to evaluate the intraobserver and interobserver variability of ovarian volume measurements in mice with high-resolution 2-dimensional ultrasonography (2DUS) and 3-dimensional ultrasonography (3DUS). Methods. Ovaries of 10 nude mice were visualized with a small-animal ultrasound scanner and a 40-MHz probe. For each ovary, volume was measured 3 times by 2 independent readers using both 2DUS and 3DUS methods. The 2DUS method used a biplane ellipsoid model. The 3DUS method estimated the volume by integrating 10 to 12 parallel image planes of the ovary after semiautomated outlining of the boundaries. For each type of measurement, intraobserver and interobserver standard error of measurement (SEM) values and minimal detectable volume changes were calculated by analysis of variance. Results. Two-dimensional ultrasonography showed much poorer reproducibility, with higher absolute intraobserver and interobserver SEM values (0.50 and 0.61 mm 3 , respectively) than 3DUS (0.20 and 0.35 mm 3 ; P < .01). Relative intraobserver and interobserver SEM values were also much higher for 2DUS (12.20% and 14.88%) than for 3DUS (5.12% and 8.97%; P < .01). The minimal volume changes that could be detected with a 95% confidence level in successive measurements by the same (or different) observers were 33.90% (41.22%) for 2DUS and 14.10% (24.87%) for 3DUS. Conclusions. High-resolution 3DUS can provide a reliable tool for noninvasive, longitudinal ovarian volume measurements in mice. Key words: high-resolution ultrasonography; ovary; small-animal imaging.Received March 22, 2007, 1 Ovarian cancer is rarely diagnosed early, and reliable molecular or clinical markers to identify early changes have not been established. Moreover, prevention strategies that would inhibit early progression of this fatal disease are currently not available.Small-animal models of ovarian cancer have been used extensively in preclinical studies. Historically, most small-animal ovarian cancer research has relied on subcutaneous tumor models. These models allow for external measurements of tumor diameter using calipers to

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