Volumetric and morphometric analysis of the mastoid process for assessment of sexual dimorphism using cone-beam computed tomography: a pilot study for a new forensic approach

Abstract Background The mastoid process is a compact cranial bone structure, resistant to physical damage since it is inserted into the petrous portion of the temporal bone and therefore protected in the region of the cranial base. Previous studies suggested the assessment of mastoid process to sex estimation in other countries, and knowing the racial miscegenation in the Brazilian population, the present evaluation was necessary. The aim of this study was to evaluate sexual dimorphism in a Brazilian population, using a new methodological proposal in pilot study, by means of analyzing the mastoid process in cone-beam computed tomography (CBCT) and two open-source software. Results CBCT scans of 44 patients (22 females and 22 males) were included, and using ITK-SNAP and 3D Slicer software, five landmarks were applied to both mastoid processes, providing the measurement of nine 3D Euclidean distances, an angular measurement, and volumetric analysis. The intraclass correlation coefficient (ICC) and independent sample t -test ( α = 5%) were used. Stepwise discriminant analysis was performed to predict sex. The ICC ranged from 0.807 to 0.999. Mean values were significantly higher in males, except for distance between the porion and the mastoid incision ( P > 0.05) and the angle between the mastoid processes ( P > 0.05). The distance between right and left mastoid processes showed the greatest accuracy for estimating sex (81.8%). The volume presented 76.1%. In the stepwise, the distance between the porion and the mastoidale, distance between the right and left mastoid processes, and angle between the mastoid processes combined, presenting an accuracy of 80.7%. Conclusions The volumetric and morphometric analysis of mastoid process, based on the proposed method with the use of CBCT and open-source software, is reliable for determining sexual dimorphism in a Brazilian population.