Development of an anatomically accurate cavity model for female pelvic organs based on MRI 3D reconstruction: A...

Previous female pelvic organ models have predominantly been solid models, which do not accurately reflect the true anatomical structure of the human body. To construct anatomically accurate cavity three-dimensional reconstruction models of female pelvic cavity organs based on in vivo human magnetic resonance imaging (MRI). Based on pelvic MRI from 120 patients, we measured organ wall thickness and anatomical variation to obtain population-averaged wall-thickness parameters (mean ± SD). Using these parameters, we constructed a single representative cavity model through segmentation, Non-Uniform Rational B-Spline surface reconstruction, and Boolean operations. This model represents an instance informed by population metrics rather than a voxel-by-voxel composite of all 120 scans. The present study focuses on visceral organ cavities (uterus, vagina, bladder, and rectum) and does not include pelvic body-wall musculature or bony structures. This was combined with Non-Uniform Rational B-Spline surface reconstruction in Ge-omagic Wrap and Boolean operations in SolidWorks to construct 4 major cavity entities: an irregular wall-thickened myometrial cavity with endometrial resection, a cervically enveloped upper semi-closed (lower open vaginal cavity, a semi-closed bladder cavity with an open urethral end, and an open-ended rectal cavity). A standardized wall thickness parameter table (accuracy 0.01 mm) was established through double measurements by 2 independent operators, with final values derived from the mean of measurements. Anatomically characteristic cavity models were generated, forming an assembly that reflects the adjacency relationships of multiple organs. Measurement results of organ wall thickness, bladder wall 1.52 ± 0.28 mm (intraclass correlation coefficient [ICC] = 0.781), vaginal wall 3.97 ± 0.56 mm (ICC = 0.876), rectal wall 1.38 ± 0.19 mm (ICC = 0.824). This study used MRI-derived, population-averaged wall thickness to construct representative cavity models of female pelvic organs. The inputs showed good reproducibility (ICC), but external validation, such as cadaveric comparison or independent imaging, is still needed. These models provide a basis for teaching, preliminary simulations, and future finite-element analyses.