Volume assessment of the normal female cervix with MR imaging: Comparison of the segmentation technique and two geometric formulas

Rationale and Objectives. The purpose of this study was to determine the volume of the normal female cervix and to determine the geometric formula that yields the best estimate. Materials and Methods. Magnetic resonance images of the pelvis in 30 young women were reviewed retrospectively. The volume of the cervix was estimated by using the formulas for an ellipse and a cylinder. Manual labeling and segmentation of the cervix were also performed, and the volume was calculated on the basis of the number and size of the voxels. Comparison of these methods was then performed by using a two-tailed Student t test. Results. No statistically significant difference was found (P = .7) between the volume calculated with the segmentation technique (25.3 mL) and that estimated with the formula for a cylinder (24.8 mL). A statistically significant difference (P < .05) was found between the volume calculated with the segmentation technique and that estimated with the formula for an ellipse (16.4 mL). Conclusion. The normal volume of the cervix in this population of young women was approximately 25 mL. The volume of the cervix should be estimated with the formula for a cylinder.