Preparation of Human Inner Ear Structures for High Resolution Imaging Studies

Introduction of the novel imaging modalities such as optical coherence tomography and scanning laser optical tomography allow the morphological and functional evaluation of the intracochlear structures up to the histological details. The prerequisite of these modalities is the preparation of the membranous labyrinth by removing the dense otic capsule to enhance the optical penetration depth. In the present study, a combination of the chemical decalcification and bone drilling method was explained for the preparation of the human inner ear structures for further studies.
In this study, nine human temporal bones were used and trimmed in cubes containing middle and inner ear structures. The samples were immersed in 5% nitric acid, 20% EDTA, and 10% EDTA solutions, respectively. The samples were brought out and rinsed every 90 minutes, and mechanical removal of the softened bone was performed with surgical drill system until the complete decalcification of the samples was confirmed by X-ray imaging. The prepared samples were evaluated by microcomputed tomography imaging for anatomical distortions caused by the preparation process.
Complete decalcification and preparation of the samples were obtained in average of 10.5 ± 0.5 hours. No obvious morphological changes were observed in microcomputed tomography images, except for fracture of the remnant bony shell at the apex of cochlea in one sample.
The combination of the chemical decalcification and mechanical removal of the softened bone can accelerate the sample preparation for high resolution imaging studies without significant morphological changes.