👂 Journey of Sound to the Brain by NIH
How do people figure out all of this? The anatomy of the middle ear, the area behind the eardrum, has traditionally been studied by sectioning of tissue, a technique called histology. This technique has a risk of deformation and does not allow the dynamic study of the sound transmission. This is where CT comes in.
Traditional micro-CT has eliminated the risk of deformation, but it isn't fast enough to observe how sound is transmitted from the eardrum to the inner ear. Dynamic observation of the middle ear requires brighter and more coherent X-rays.
Schmeltz et al. at Paul Scherrer Institute, Swiss Light Source, used synchrotron-based phase-contrast microtomography and post-gating algorithm to resolve the fast micromotions of the middle ear structure at 128 Hz. They used ex-vivo fresh-frozen human temporal bones. The results are beautiful. The 3D renderings they produced from this study show the micron-level movement of the tiny bones (malleus, incus, and stapes) you saw in the NIH video. This time, these are not computer graphics but actual CT data.
This study was recently published in Communications Biology: Schmeltz, M., Ivanovic, A., Schlepütz, C.M. et al. The human middle ear in motion: 3D visualization and quantification using dynamic synchrotron-based X-ray imaging. Commun Biol 7, 157 (2024). https://doi.org/10.1038/s42003-023-05738-6
👓 Read the article