A Tiered 3D CNN Framework for Forensic Sex Estimation from CBCT: Matched Comparison of Full-Skull Volumes and Mandible-Only Masks.
Authors
Affiliations (5)
Affiliations (5)
- College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400030, China.
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
- Chongqing Public Security Bureau, Chongqing 401147, China.
- Key Laboratory of Functional Composite Materials of Guizhou Province, College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China.
- Chongqing Police College, Chongqing 401331, China.
Abstract
Deep learning has advanced automated sex estimation from craniofacial imaging, but differences in cohorts, input representations, and protocols between studies leave the performance gap between full-skull and mandible-only inputs insufficiently quantified. We compared the two inputs under matched conditions using cone-beam computed tomography (CBCT) scans of 353 Chinese Han individuals (102 males and 251 females, aged 6-78 years). From each scan, we derived a full-skull grayscale volume (1283) and an automatically segmented mandibular mask (803). The same lightweight three-dimensional (3D) convolutional neural network (about 572,000 parameters) was trained on each input with identical five-fold cross-validation splits and training protocol. Balanced accuracy (BAcc) was 96.20% ± 3.66% for the full-skull input and 88.67% ± 4.58% for the mandible-only input (paired difference in pooled BAcc, 7.52 percentage points, 95% confidence interval (CI) 4.55-10.50). Mandible-only BAcc was 93.17% ± 2.63% at 19-50 years (n=259), whereas pooled BAcc was 66.67% at ≤17 years and 79.80% above 50 years. In this single-center cohort, the full-skull input performed better overall, and the mandible-only input achieved high accuracy only in adults aged 19-50 years. Applying these subgroup results requires an independent age assessment, and external validation is needed before forensic use.