The endoscope radically changed medicine; doctors were able to use a tiny camera at the end of a thread-thin wire to look into a patient’s body without major surgery. Engineers at Stanford University have taken the endoscope a step further: they’ve built the thinnest one ever and it see individual cells.
Their needle-thin endoscope has the potential to image single cancer cells and peer into organs where larger endoscopes could do more damage than good, like in the brain. And the super thin endoscope would create a much smaller scar than a laparoscope, the instrument typically used to do knee surgery.
Conventional endoscopes are built with multiple optical fibers, some of which illuminate the area and others which record the image and carry it back to the viewer. The more fibers inside the endoscope, the better the resolution of the image. But more fibers also translates into a bulkier endoscope.
Kahn’s team built a endoscope using just one multimode fiber. Multimode fibers are capable of carrying light along many different paths — in fact, a “mode” is a path that light takes. The team’s idea was to use a single fiber to both illuminate an object as well as carry data from the image. The challenge is the information gets scrambled on the way, since the light is moving along different paths.
To make it work, Kahn’s team built a device called a spatial light modulator. The modulator sent a continuous beam of laser light down the fiber in random paths. Because of the random path, once the light exited the fiber it made a speckled pattern. Some of that light bounced back up the fiber.
A computer program created by Kahn’s team analyzed the speckled pattern returning up the fiber and used that to build an image. Their technique pushed the resolution of the image even further than what they had expected, and enabled them to see object that were sizes of individual cells.
Kahn said in a press release that he sees most of the new applications in imaging, to study in detail cells as they operate inside the body.