Stereologic Investigation of Mastoid Air Cell Geometry: Volume, Surface Area, and Anisotropy

Abstract

Objective: To assess mastoid geometry using computed tomography (CT) scans and design-based stereological methods. Background: The anatomical organization of the mastoid air cell system (MACS) remains debated. Geometrical parameters have previously been determined by automated image-analysis algorithms. Stereology is an alternative approach, which has previously been applied to estimate the volume of the MACS, but has not previously been used to estimate surface area or study anisotropy. Methods: Twenty-three clinical CT scans of aerated temporal bones obtained from various ENT patients were studied. The structural orientation and anisotropy of the MACS was investigated by test-grid rotation and rose plots. Volume, surface area, and surface area-to-volume ratio were estimated with design-based stereology. Results: Anisotropy of the mastoid air cells was demonstrated by a significant difference in surface area estimates between the axial and coronal planes (p = 0.0065). Rose plots illustrated variances in surface area estimates with different grid rotations, and a minimum value in the craniocaudal direction was shown. Sampling in the axial plane provided the least variance due to anisotropy. The mean (±SD) volume and surface area estimates were 5.71 ± 2.98 cm3 and 117 cm2 ± 60 cm2, respectively. A large biological variation was noted. The mean (±SD) surface-to-volume ratio was 20.6 ± 2.8 cm−1. Conclusions: The stereological technique proved to be a robust method for volume and surface area estimation in clinical CT scans. The mastoid air cells constitute an anisotropic cell-system that seems to have a predominant orientation in the craniocaudal direction.

Sex Estimation From Measurements of the Mastoid Triangle and Volume of the Mastoid Air Cell System Using Classical and Machine Learning Methods

“…1,2,7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] In the current study, males also showed higher linear and area measurements than females (P = 0.000). Boyle's law, 3,24 the acoustic method, 25 and radiological methods, including CT scans, [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] have been used to measure MACS volumes (Table 5). Luntz et al 34 reported that male MACS volumes were higher than female values in one of these studies, although there was no statistically significant difference between the sexes.…”

“…8,22,23 To date, research on the volume of the mastoid air cell system (MACS) has mainly focused on clinical purposes. 3,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] Although volume-processed CT images are considered more effective in estimating morphological sex because of their higher variance, 42 no studies in the literature have used MACS volume measurements for direct anthropological or forensic sex estimation purposes.…”