Evaluation of the noise-exposed cochlea using synchrotron radiation-based microtomography

Noise-induced hearing loss can be caused by sudden or prolonged exposure to loud noise. Noise exposure is known to contribute to the degeneration of sensory cells, disrupting the conversion of mechanical sound waves into electrical impulses and further their transmission to the brain. To determine the pathophysiological condition of the inner ear cells in animal models, the measurement of the animals' hearing is essential. The follow-up examination of the cochlea is particularly important as it provides information on the cellular morphology changes. Our aim was therefore to investigate the hair cell survival in the inner ear of mice exposed to two high noise levels using synchrotron radiation-based microtomography. Its spatial resolution allows for the reconstruction of three-dimensional images of unstained cochlea at the cellular level. We segmented the basilar membrane via automatic cell segmentation and fast manual cell removal, and determined its length using a one-dimensional Isomap embedding. After extracting its middle region and image slices aligned with it, surviving inner and outer hair cell locations were semi-automatically determined and then manually corrected using the ImageJ plugin PointPicker. These results were compared with the confocal microscopy data. The data collected provides meaningful information about healthy and damaged hair cells in the adult cochlea.