A comparative analysis of YOLOv8 and nnU-Net v2 based pipelines for sex and age estimation from maxillary sinus morphometry on panoramic radiographs


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OCAK M., Çatak C., Aksoy S., ORHAN K.

International Journal of Legal Medicine, 2026 (SCI-Expanded, Scopus) identifier identifier

Özet

Objective: This study aimed to develop and compare two deep learning-based segmentation–radiomics pipelines — YOLOv8-Hybrid and nnU-Net v2 — for automated sex classification and age estimation from maxillary sinus morphometry on panoramic radiographs. Methods: A balanced dataset of 1,024 panoramic radiographs (512 males, 512 females; age 18–81 years) was collected from Near East University, North Cyprus. Ground truth sinus annotations were generated by an expert oral radiologist and validated through dual-annotator inter-observer reliability assessment (ICC (2,1) = 0.94–0.97). The YOLOv8-Hybrid pipeline employed YOLOv8n-seg coarse segmentation, U-Net boundary refinement, > 120 morphometric and radiomic features, and CatBoost/XGBoost classifiers. The nnU-Net v2 pipeline used auto-configured 2D U-Net segmentation with identical feature extraction and XGBoost prediction. Both pipelines underwent 5-fold cross-validation with patient-level splitting, transfer learning, Bayesian hyperparameter optimization, and SHAP interpretability analysis. Results: nnU-Net v2 achieved statistically significant superiority in sex classification (AUC = 0.927 [95% CI: 0.881–0.964]) over YOLOv8-CatBoost (AUC = 0.893 [0.841–0.938]; DeLong p = 0.024, Cohen’s d = 0.48). Both pipelines demonstrated comparable age estimation performance (MAE ≈ 7.2 years). YOLOv8 showed exceptional consistency (mAP@50 = 98.19%, CV = 0.77%). SHAP analysis identified bilateral area difference as the most determinant feature (sex: 0.42, age: 0.51). External validation on 50 independent images confirmed model generalizability. Conclusions: This study provides the first systematic comparison of YOLOv8 and nnU-Net v2 for forensic maxillary sinus analysis. nnU-Net v2 is recommended for precision-critical forensic reporting, while YOLOv8-Hybrid is suited for high-throughput screening. The > 120 radiomic/morphometric features establish a comprehensive framework for automated biological profiling.