Comparison of CT-Derived Prostate Volume Measurements Using Three-Dimensional Segmentation and the Ellipsoid Formula in Intact Male Dogs

Abstract

This retrospective study compared prostate volumes obtained from computed tomography images using three-dimensional segmentation and the ellipsoid formula. Archived CT examinations of eight intact male dogs with radiological findings consistent with prostatic hyperplasia were included. The prostate was manually delineated on consecutive transverse images using 3D Slicer, and segmentation-based volume was calculated automatically. Prostatic length, height, and width were measured, and ellipsoid volume was calculated using the formula V = H × W × L × 0.523. Paired measurements were compared using the Wilcoxon signed-rank test. The relationship and agreement between the methods were evaluated using linear regression and Bland–Altman analyses, respectively. Mean prostate volume was 16.57 ± 11.20 cm³ with three-dimensional segmentation and 16.35 ± 14.63 cm³ with the ellipsoid formula. No significant difference was found between the methods (P = 0.945). A positive linear association was observed between segmentation- and ellipsoid-derived volumes (R = 0.970; R² = 0.942; P < 0.001). Bland–Altman analysis showed a mean difference of −0.224 cm³, with 95% limits of agreement ranging from −9.291 to 8.843 cm³. Although the ellipsoid formula produced a group mean close to that obtained by three-dimensional segmentation, the relatively wide limits of agreement indicated variability between the methods at the individual-case level. These preliminary findings should be confirmed in larger canine populations before the methods are considered interchangeable.