An important source of disability, particularly in children, is the impairment of sound transmission through the middle ear leading to conductive hearing loss. An improved understanding of the biophysical properties of middle ear structure and function are of considerable international scientific interest because of the ability to directly apply such knowledge to surgical methods of hearing reconstruction. However, detailed investigations of middle ear hearing mechanics have been challenging due to the anatomically small dimensions (the three middle ear bones are the smallest bones in the body) and the middle ear’s location within the confines of the temporal bone.
Over the past 4 years our group has designed and executed an innovative approach to investigate the human middle ear biomechanics by using synchrotron-based X-ray phase contrast imaging (SR X-PCI). This sophisticated imaging method provides ultra-high-resolution (micrometer) imaging quality paired with excellent soft tissue contrast to permit histologic level details of the human ear. Furthermore, we are internationally the first research group to succeed in performing dynamic imaging of the movements of the human ossicular chain using this technique. This newly developed dynamic imaging method unlocks a new pathway by which the mechanics of hearing can be rigorously investigated. With this proposal, divided in four workpackages, we aim to push the resolution of the dynamic SR X-PCI to break new grounds in the understanding of middle ear biomechanics in normal, diseased and reconstructed states.
This research will provide critically important information for otosurgeons, who can use lessons learned to improve outcomes for patients undergoing hearing restoration surgery. In a first step, we will leverage our previously acquired datasets of static SR X-PCI data to build a new ultra-high resolution finite element (FE) model of the human middle ear. We will validate against temporal bone specific data from dynamic SR X-PCI and laser Doppler vibrometry. With a massive increase in resolution and a direct experimental description of material properties we expect to exceed the accuracy of present FE models.
This approach allows us to simulate the dynamic behavior of the middle ear in different conditions (normal, diseased, post-surgical) to inform experiments and surgeons. The second step will combine artificial intelligence modeling and digital volume correlation to automatize the analysis of the large datasets generated by dynamic SR X-PCI. With direct correlation of segmented data, such as the tympanic membrane, it will be possible to depict complex within structure movements. Presently this is not feasible, due to limitations in data-analysis pipelines. Thanks to technical refinements at the Swiss Light Source beamline currently underway, we will push the resolution of dynamic SR X-PCI to a new level. After upgrades to the beamline are complete, we will perform dynamic SR X-PCI on 20 temporal bones under acoustical stimulation at higher frequencies than were previously possible. The higher resolution will permit better descriptions of 3D micromovements at mid to high frequencies. Finally, we explore translational experiments via imaging of the reconstructed ear. With direct experience in otosurgery, our group has developed an onsite minimally invasive endoscopic approach for ossicular chain reconstruction while keeping the tympanic membrane intact.
This approach will allow us to experimentally define the interactions between reconstructive materials and the mechanical efficiency of the human middle ear. In these experiments, we will directly compare autologous grafts to titanium-based implants and use the data to further test and refine our FE model. This novel approach will define previously unidentified factors influencing the hearing results from reconstructive middle ear surgery.
Contact
If you are interested in this research topic and wish to learn more, don’t hesitate to contact us:
Lukas Anschuetz (lukas.anschuetz@chuv.ch)
Changling Li (changling.li@chuv.ch)