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New Instrument Visualize How Sound Travels Through The Ear

[Estimated read time: 3 minutes]
  • A new technique named Optical Coherence Tomography vibrography can visualize how sound-induced vibrations travel through the ear. 
  • This will help doctors distinguish various middle-ear disorders without performing a surgery. 

The tympanic membrane collects the incoming sound energy and transmits it through the ossicles to the cochlear fluid, which is then converted into neural signals in the inner ear. To diagnose any damage in the middle ear, physicians perform Vibro-acoustic analysis of tympanic membrane and middle ear.

To examine sound-induced vibrations at a particular position in the middle ear, previous techniques used capacitive probes, stroboscopic microscopy, and Mössbauer effect. Whereas modern techniques rely on more sensitive optical interferometric methods like holography and Doppler vibrometry.

Recently, researchers at Massachusetts General Hospital developed a new instrument that can visualize how vibrations (induced by sound) travel through the ear. It offers a detailed view of how the ear gathers and processes sound waves. With further enhancements, the technology — OCT vibrography — can be used to diagnose hearing disorders.

How It Works?

This new device uses an advanced biomedical imaging method known as optical coherence tomography (OCT) to generate high-resolution pictures of tissue microstructures. It precisely images the auditory ossicles in the middle ear (smallest bones in our body), which transform sound waves into mechanical vibrations.

To measure these vibrations, they synchronized the sound of a high-fidelity speaker with an OCT measurement instrument. When the ear receives sound, the bones start moving and the OCT captures these movements. The OCT images are then fed to special algorithms (developed in this study) to accurately measure vibrations in the ear.

Previous techniques are capable of measuring the motion of 30 individual positions on the bones, whereas the new OCT technique can concurrently measure the motion at more than 10,000 locations on the ossicular surface and eardrum.

The authors have tested this technique in chinchilla cadavers: they measured sound-induced eardrum motion and captured a unique mode of ossicular motion at high frequencies. This could help scientists develop new methods for surgeons to fix damaged ears.

Reference: OSA Publishing | doi:10.1364/BOE.9.005489

Although several techniques for detecting middle-ear problems already exist, diagnosing the precise position requires moving the eardrum through a surgery. This technique will help doctors differentiate between multiple middle-ear disorders without performing a surgery and make strategies for further treatment.

Why They Experimented With Chinchilla?

Image credit: Wikimedia Commons

As far as size and sensitivity to various frequencies are concerned, chinchilla’s ears are very much similar to those of humans, thus they are used in most of the hearing researches. In this study, the authors used cadavers because it took nearly 1 minute to perform measurements, during which the heartbeat and breathing of a live chinchilla would likely distort the motion data.

Currently, researchers are trying to figure out whether motion data captured from up to 5 locations, merged with OCT image of the entire middle ear and eardrum, could give enough details to diagnose ear disorders in living animals.

Read: AI Can Detect Irregular Heartbeat With High Accuracy

Soon, researchers will test their system on human cadavers to discover how human ears are different from chinchillas. They will examine new ways of applying this technology in certain clinical applications like diagnosing a specific hearing disorder.

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