At the Massachusetts Institute of Technology, engineers have created an endoscope that’s about as thin as human hair, featuring an optical fiber only 125 microns in diameter. It’s so small that it can be inserted deeper than ever before into the brains of living mice to see individual in situ neurons. While similar endoscopes have existed in the past, they were typically about five or more times wider than the new device. The device can see the neurons firing down to a resolution of about one micron. The new capability certainly has implications for a greater understanding of the functionality of the brain and how neurological diseases develop.
The device uses a a miltimode optical fiber and relies on optogenetics, technique for making brain cells fluoresce in response to being illuminated. The optical fiber transmits beams of different frequency light at the same time and can be made to project a light beam away from its main axis, and so excite neurons that are not in its direct line of sight without having to re-position it.
The light beam can be made to scan the field of view, exciting neurons along the way and seeing what’s happening in that region of the brain. “To achieve scanning fast enough to image neurons firing, we used an optical component known as a digital mirror device (DMD) to quickly move the light spot,” said Shay Ohayon, the developer of the new endoscope. “We developed a technique that allowed us to use the DMD to scan light at speeds up to 20 kilohertz, which is fast enough to see fluorescence from active neurons.”
Photo: The optical fiber microendoscope (upper left) is shown just before it is inserted into tissue. Image Credit: Shay Ohayon, Massachusetts Institute of Technology.
Study in Biomedical Optics Express: Minimally invasive multimode optical fiber microendoscope for deep brain fluorescence imaging…
Via: The Optical Society…