Volumetric evaluation of temporal bone structures in the cases with bilateral tinnitus: clinical and morphometrical study

Geometric Atlas of the Middle Ear and Paranasal Sinuses for Robotic Applications

In otolaryngologic surgery, more and more robots are being studied to meet the clinical needs of operating rooms. However, to help design and optimize these robots, the workspace must be precisely defined taking into account patient variability. The aim of this work is to define a geometric atlas of the middle ear and paranasal sinuses for endoscopic robotic applications. Scans of several patients of different ages and sexes were used to determine the average size of these workspaces, which are linked by the similar use of endoscopes in surgery.

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

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 cm and 117 cm ± 60 cm, respectively. A large biological variation was noted. The mean (±SD) surface-to-volume ratio was 20.6 ± 2.8 cm.

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.