Analyses of sexual dimorphism of contemporary Japanese using reconstructed three-dimensional CT images--curvature of the best-fit circle of the greater sciatic notch.

We examined various expression methods of sexual dimorphism of the greater sciatic notch (GSN) of the pelvis in contemporary Japanese residents by analyzing the three-dimensional (3D) images reconstructed by multi-slice computed tomography (CT) data, using image-processing and measurement software. Mean error of anthropological measurement values between two skeletonized pelves and their reconstructed 3D-CT images was 1.4%. A spline curve was set along the edge of the GSN of reconstructed pelvic 3D-CT images. Then a best-fit circle for subsets of the spline curve, 5-60mm in length and passing through the deepest point (inflection point) of the GSN, was created, and the radius of the circle (curvature radius) and its ratio to the maximum pelvic height (curvature quotient) were computed. In analysis of images reconstructed from CT data of 180 individuals (male: 91, female: 89), sexes were correctly identified in with 89.4% of specimens, with a spline curve length of 60mm. Because sexing was possible even in deeper regions of the GSN, which are relatively resistant to postmortem damage, the present method may be useful for practical forensic investigation.