Mandibular Gonial Angle Measurement with Anatomical Precision in 3D Volume Rendered CT Images

This letter presents a novel, simple, and reproducible method for measuring the gonial angle using open-source imaging software, 3D Slicer. The main research question was whether a standardized three-dimensional (3D) approach could provide a practical and accurate alternative to traditional two-dimensional cephalometric techniques.

High resolution head computed tomography (CT) scans were imported into 3D Slicer (version 5.6.2). The mandible was reconstructed in 3D using volume rendering module. Two three-point planes were defined: one tangential to the mandibular body's lower border and one to the ramus' posterior border. Their angle was calculated using a Python script within 3D Slicer.

The workflow enabled accurate and reproducible 3D gonial angle measurements, providing flexibility for real-time adjustment, repeated calculations, and enhanced anatomical accuracy over traditional methods.

This approach offers a practical, cost-free, and standardized technique with potential applications in orthognathic surgery planning, asymmetry studies, and anthropological analysis of mandible.

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