If you've been to a routine eye exam at the optometrist's office, chances are you've had to place your chin and forehead up close to a bioimaging device.
It's known as optical coherence tomography (OCT), and it's widely used in eye clinics around the world. OCT uses light waves to take high-resolution, cross-sectional images of the retina in a non-invasive manner.
These images can be essential for diagnosing and monitoring eye conditions.
In any bioimaging—either retinal or in-vivo imaging that takes place inside the human body—devices must be quite small and compact to produce high-quality images.
However, mechanical aspects of OCT devices, like spinning mirrors, can increase the chance of device failure.
Researchers at the University of Colorado Boulder have developed a new bioimaging device that can operate with significantly lower power and in an entirely non-mechanical way. It could one day improve detecting eye and even heart conditions.
In a recent study published in Optics Express, the team of engineers created a device that uses a process called electrowetting to change the surface shape of a liquid to perform optical functions.
"We are really excited about using one of our devices, in particular for retinal imaging," said lead author Samuel Gilinsky, a recent PhD graduate in electrical engineering. "This could be a critical technique for in-vivo imaging for inside our bodies."
By creating a device that doesn't use scanning mirrors, the technique requires less electrical power than other devices used for OCT and bioimaging.
"The benefits of non-mechanical scanning is that you eliminate the need to physically move objects in your device, which reduces any sources of mechanical failure and increases the overall longevity of the device itself," Gilinsky said.
Gilinsky noted the need for these OCT systems to be compact, lightweight and, most importantly, safe for use for the human body.
Other members of the research team included Juliet Gopinath, professor of electrical engineering; Shu-Wei Huang, associate professor of electrical engineering; Victor Bright, professor of mechanical engineering; PhD graduates Jan Bartos and Eduardo Miscles; and PhD student Jonathan Musgrave.
"Our work presents an opportunity where we can hopefully detect health conditions earlier and improve the lives of people," said Gopinath.
Where zebrafish meets the eye
To test the device's ability to perform biomedical imaging, the researchers turned to a surprising aquatic animal: zebrafish.
Zebrafish have been used in OCT research because the structure of their eyes is fairly similar to the structure of the human eye. For the study, the researchers focused on identifying where the cornea, iris and retina was from the zebrafish.
To conduct in-vivo or other bioimaging, scientists need to be able to identify the structure of the samples of interest, such as the eye or organs inside the body. The two benchmarks that the group hoped to achieve were 10 micron in axial resolution and then around 5 microns in lateral resolution, all smaller than the width of a human hair.
"The interesting result was that we were able to actually delineate the cornea and iris in our images," said Gilinsky. "We were able to meet the resolution targets we aimed for, which was exciting."
Being able to test this bioimaging device can open new doors for mapping aspects of the retina that can be essential for diagnosing potential eye conditions like age-related macular degeneration and glaucoma.
Additionally, Gilinsky said, the new bioimaging technique could help in delineating actual human coronary features that would be important in diagnosing heart diseasethe leading cause of death in the United States.
With the research team's expertise in microscopy systems, they are hopeful to create endoscopes that could revolutionize bioimaging technology.
"There is a growing push to make endoscopes as small in diameter and flexible as possible to cause as little discomfort as possible," he said. "By using our components, we can maintain a very small-scale optical system compared to a mechanical scanner that can help OCT technologies."
The project was funded by the Office of Naval Research, National Institutes of Health and the National Science Foundation.
