BioPhotonics spoke with Kazunori Serita, an associate professor in the Graduate School of Information, Production and Systems at Waseda University in Japan. Serita was part of a research team that used terahertz imaging to visualize the cochlea of mice with a high degree of spatial resolution, as described in Optica. Their use of terahertz imaging could potentially enable new methods of hearing loss diagnosis. What made you want to use terahertz imaging, as opposed to other modalities that are used for structural details, such as optical coherence tomography? The sample we’re working with, the cochlea, is surrounded by bone. With optical methods, there’s a lot of scattering, so it is hard to see deep inside. X-rays can penetrate and show internal structures, but they come with radiation exposure risks. On the other hand, terahertz waves can pass through bone and allow us see the inside, and since the radiation impact is minimal, I thought they could be used more safely. This project began when Takeshi Fujita, an ENT doctor at Kobe University, Japan, and one of my coauthors, came to me with a challenge: how to nondestructively observe the inside of the cochlea. Terahertz imaging was already one of the ideas on the table, but conventional methods did not have the sensitivity we needed. Then, I thought the terahertz imaging technique I had been working on might be able to solve the problem. It looks like the instrumentation you used was an optical crystal (gallium arsenide) as well as a femtosecond laser. What challenges remain in putting this into a medical instrument that can be used in a clinical setting? There are probably two major challenges. The first is making the system more compact. The current setup is large, so we cannot really use it as is. It will need to be redesigned to be much smaller. Fortunately, a fiber laser is the light source, which is known for its potential to be compact, so I think we can do it. The second challenge is the power of the terahertz waves. For actual use in medical settings, we would need a bit more power. That means we will likely need to look into other optical crystals besides the gallium arsenide that was used this time. Time-of-flight data was collected that showed structural differences that were identified with an imaging algorithm. Assuming a clinician had extracted such data, how could this theoretically benefit a patient from a treatment perspective? It might be difficult to use this terahertz technology for actual treatment. But it could potentially be used for on-site diagnosis of sensorineural hearing loss. In many cases, this type of hearing loss is caused by damage to the cochlea, but there hasn’t been a safe, high-resolution way to observe the inside of the cochlea in living patients. Until now, the only option has been to remove the cochlea after death and physically break it open to see inside. If we can safely diagnose the condition in vivo, this could become a valuable tool for identifying the disease.