X-ray vision of the inner ear: New imaging technology unlocks hidden views of the hearing organ

A Japanese research team has developed a groundbreaking imaging technology that allows scientists to gaze at the complex structures of the inner ear in unprecedented detail. This development can change the doctor’s diagnosis and treatment of hearing impairment.

For the first time, the researchers successfully used Terahertz waves to visualize the internal architecture of the cochlea (spiral-shaped organs responsible for converting sound vibrations into neural signals) and with micron-scale accuracy without damaging the delicate structure.

“While traditional imaging methods often struggle to visualize the details of the organ from it, our 3D Terahertz near-field imaging technology allows us to see small structures inside the cochlea without causing any damage.”

The cochlea buried deep in the temporal bone of the skull has long been difficult to check. Current imaging techniques (such as CT scans) lack solutions to capture their complex internal structures, and methods that provide better details often require corruption of samples.

The study, published this week in the journal Optica, demonstrates how Terahertz radiation, the electromagnetic wave between microwaves and infrared light, provides unique advantages for biological imaging. These waves do not damage tissue, can penetrate bones, and are sensitive to differences in hydration and cellular structure.

Serita’s interest in the project sparked discussions with Takeshi Fujita, co-author of the Department of Otolaryngology and Neck Surgery at Bryant University.

“That made me think about it – maybe Terahertz imaging can help solve these problems,” Cerita said. “The biggest question is whether we can see the tiny internal structure of the cochlea without causing any damage.”

The traditional Terahertz imaging system uses lenses that focus the waves on locations spread a few millimeters – too large to check the minute structure of the cochlea. The team overcomes this limitation by generating Terahertz waves from nonlinear optical crystals, creating a light source with a diameter of 20 microns.

“So far, there is no way to observe the internal structure of the cochlear at high resolution,” Serita noted.

To validate their method, the researchers conducted experiments with dry mouse cochleas – one empty, the other filled with Terahertz reflective metal. The obvious differences observed between these samples confirm that these waves are indeed penetrating the human cochlear structure.

The team then applied a machine learning algorithm to extract structural information from the 2D image and successfully created a 3D reconstruction showing a portion of the cochlear helical structure.

According to the World Health Organization, as the population ages, nearly 1.5 billion people worldwide have lived with hearing loss. Earlier and more accurate diagnosis can significantly improve treatment outcomes.

“With further development, this technology could lead to a new method of diagnosing ear diseases that has not been difficult to diagnose until now,” Serita said. “It has the potential to enable on-site diagnosis of diseases such as sensory hearing loss and other ear diseases.”

Before clinical applications may occur, there are still some challenges. The system must be miniaturized to pass through the ear canal, and a stronger source of Terahertz must be developed to penetrate deeper structures. The team also plans to test the technology on the cochlea in a more realistic biological environment, including the technology filled with lymph.

Ultimately, the researchers envision the incorporation of this technology into endoscopy and otoscopes for non-invasive imaging that could alter the diagnosis of cochlear implants and potentially aid early cancer detection in various organs.

Although there are still questions about when the technology may reach the clinical environment, its ability to reveal previous hidden structures marks an important step in our understanding of the complex machinery behind human hearing.