Super tiny scope can peek inside active neurons

"Usually, you have sacrifice either size or image quality. We've been able to achieve both with our microendoscope," says Mark Foster. (Credit: Getty Images)

A new lens-free ultra-miniaturized endoscope, the size of a few human hairs in width, is less bulky than current options and can produce higher quality images.

“Usually, you have sacrifice either size or image quality. We’ve been able to achieve both with our microendoscope,” says corresponding author Mark Foster, an associate professor of electrical and computer engineering at Johns Hopkins University.

Intended for examining neurons firing off in the brains of animals such as mice and rats, an ideal microendoscope should be small to minimize brain tissue damage yet powerful enough to produce a clear image.

Currently, standard microendoscopes are about half a millimeter to a few millimeters in diameter, and require larger, more invasive lenses for better imaging. While lensless microendoscopes exist, the optical fiber within that scans an area pixel by pixel frequently bends and loses imaging ability when moved.

In their new study, researchers created a lens-free ultra-miniaturized microendoscope that, compared to a conventional lens-based microendoscope, increases the amount researchers can see and improves image quality.

The three images on the beads are (A) the letters JHU, (B) a bat shape, (C) an image of cells. They are clear when viewed with the bulk microscope and fuzzy when viewed with the lens-based microendoscope. In images from the lensless microendoscope, the shapes are almost invisible, but the reconstructions of the image data are almost as clear as the bulk microscope.
The image above shows the imaging results from the study. A to C shows beads on a slide, viewed through a bulk microscope. D to F are the beads viewed through a conventional lens-based microendoscope. G to I are images from the new lensless microendoscope, which are purposefully terrible because they provide a lot of information about light that can be used in computational reconstructing to create clearer images, as shown in J to L. (Credit: Johns Hopkins)

The researchers achieved this by using a coded aperture, or a flat grid that randomly blocks light creating a projection in a known pattern akin to randomly poking a piece of aluminum foil and letting light through all of the small holes. This creates a messy image, but one that provides a bounty of information about where the light originates, and that information can be computationally reconstructed into a clearer image. In their experiments, Foster’s team looked at beads in different patterns on a slide.

“For thousands of years, the goal has been to make an image as clear as possible. Now, thanks to computational reconstruction, we can purposefully capture something that looks awful and counterintuitively end up with a clearer final image,” says Foster.

Additionally, the researchers’ microendoscope doesn’t require movement to focus on objects at different depths; they use computational refocusing to determine where the light originated from in three dimensions. This allows the endoscope to be much smaller than a traditional one that requires moving the endoscope around to focus.

Looking forward, the research team will test their microendoscope with fluorescent labeling procedures in which active brain neurons would be tagged and illuminated, to determine how accurately the endoscope can image neural activity.

The findings appear in Science Advances. The National Eye Institute provided funding for the study.

Source: Johns Hopkins University