The images acquired using 3D terahertz near-field imaging were used to create 3D reconstructions, allowing visualization of part of the cochlear duct, the spiral structure inside the cochlea.
Images acquired using 3D terahertz near-field imaging were used to create 3D reconstructions, allowing visualization of part of the cochlear duct, the spiral structure inside the cochlea.
A Japanese research team has developed a groundbreaking imaging technique that allows scientists to peer inside the inner ear’s complex structures with unprecedented detail. The development could transform how doctors diagnose and treat hearing disorders.
For the first time, researchers successfully used terahertz waves to visualize the internal architecture of the cochlea—the spiral-shaped organ responsible for translating sound vibrations into neural signals—with micron-level precision and without damaging the delicate structure.
“Although conventional imaging methods often struggle to visualize this organ’s fine details, our 3D terahertz near-field imaging technique allows us to see small structures inside the cochlea without any damage,” explained research team leader Kazunori Serita from Waseda University in Japan.
The cochlea, buried deep within the temporal bone of the skull, has long been difficult to examine. Current imaging technologies like CT scans lack the resolution to capture its intricate internal structures, while methods that provide better detail typically require destroying the sample.
The research, published this week in the journal Optica, demonstrates how terahertz radiation—electromagnetic waves that fall between microwaves and infrared light—offers unique advantages for biological imaging. These waves don’t harm tissue, can penetrate bone, and are sensitive to differences in hydration and cellular structure.
Serita’s interest in the project sparked after discussions with co-author Takeshi Fujita from Kobe University’s Department of Otolaryngology-Head and Neck Surgery.
“That got me thinking—maybe terahertz imaging could help solve these issues,” said Serita. “The big question was whether we could visualize the tiny internal structures of the cochlea without causing any damage.”
Traditional terahertz imaging systems use lenses that focus waves to spots several millimeters across—far too large for examining the cochlea’s minute structures. The team overcame this limitation by generating terahertz waves from a nonlinear optical crystal, creating a light source just 20 microns in diameter.
“Until now, there was no way to observe the internal structure of the cochlea non-destructively with high resolution,” Serita noted.
To validate their approach, the researchers conducted experiments with dried mouse cochleae—one empty and another filled with terahertz-reflecting metal. The clear differences observed between these samples confirmed that the waves were indeed penetrating the cochlear structure.
The team then applied machine learning algorithms to extract structural information from 2D images and successfully created 3D reconstructions showing parts of the cochlear duct’s spiral structure.
Nearly 1.5 billion people worldwide live with hearing loss, according to the World Health Organization, with the number expected to rise as populations age. Earlier and more precise diagnosis could significantly improve treatment outcomes.
“With further development, this technique could lead to a new diagnostic method for ear diseases that have been difficult to diagnose until now,” Serita said. “It has the potential to enable on-site diagnosis of conditions like sensorineural hearing loss and other ear disorders.”
Before clinical applications become possible, several challenges remain. The system must be miniaturized to fit through the ear canal, and stronger terahertz sources must be developed to penetrate deeper structures. The team also plans to test the technique on cochleae in more realistic biological environments, including those filled with lymphatic fluid.
Eventually, the researchers envision incorporating this technology into endoscopes and otoscopes for non-invasive imaging that could transform cochlear diagnostics and potentially aid early cancer detection in various organs.
While questions remain about when this technology might reach clinical settings, its ability to reveal previously hidden structures marks a significant step forward in our understanding of the intricate machinery behind human hearing.
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