Micro-endoscope

Engineers are always finding ways to make devices smaller and more efficient, and medical technology is no exception. According to a new study published in the journal Optics Express, Stanford University engineers have created a high-resolution endoscope as thin as a human hair with a resolution four times better than previous devices of similar design.

Surgeons typically use endoscopes to look inside a body cavity or organ through a natural opening, such as the mouth during a bronchoscopy. This micro-endoscope sets a new standard for high-resolution, minimally invasive bio-imaging and could lead to new methods for studying the brain and detecting cancer, in addition to making routine colonoscopies less of a pain.

According to a Stanford press release, “the prototype can resolve objects about 2.5 microns in size, and a resolution of 0.3 microns is easily within reach. A micron is one thousandth of a millimeter. By comparison, today's high-resolution endoscopes can resolve objects only to about 10 microns. The naked eye can see objects down to about 125 microns.”

“I'd say the main thing distinguishing our endoscope from other endoscopes is that we achieve microscopic resolution,” said lead author Joseph Kahn, a professor of electrical engineering at the Stanford School of Engineering, in an interview with Healthline. “It can be used to look at very small features, such as cells, inside the body, and may [eliminate] the need to remove cells using a biopsy needle and look at them under a conventional microscope.”

The Origin of an Idea

Kahn began studying endoscopic technology two years ago with fellow Stanford electrical engineer Olav Solgaard.

"Olav wanted to know if it would it be possible to send light through a single, hair-thin fiber, form a bright spot inside the body, and scan it to record images of living tissue," Kahn said in a press release.

But figuring out how to create a tiny, high-resolution scope wasn't easy. The team's first challenge was that of multimode fibers, through which light travels via many different paths, known as modes.

While light is very good at conveying complex information through such fibers, it can get scrambled beyond recognition along the way. So, Kahn and his graduate student, Reza Nasiri Mahalati, used a special light modulator, or miniature liquid crystal display (LCD), to unscramble the light.

Mahalati's breakthrough solution was based on the seminal work in magnetic resonance imaging (MRI) done by another Stanford electrical engineer, John Pauly, who had used random sampling to dramatically speed up image recording in MRIs.

"Mahalati said, 'Why not use random patterns of light to speed up imaging through multimode fiber?' and that was it. We were on our way," Kahn said. "The record-setting micro-endoscope was born."

A Working Prototype

While Kahn and his colleagues have managed to create a working prototype of their ultra-thin endoscope, at the moment, the fiber must remain rigid. Because bending a multimode fiber scrambles the image, the fiber must be placed inside a thin needle to keep it straight while it's inserted into the body.

Rigid endoscopes are common in many surgeries, but they often require relatively thick, rod-shaped lenses to yield clear images. Flexible endoscopes, on the other hand—the kind used in colonoscopies—are usually made up of bundles of tens of thousands of fibers, each relaying a single pixel of the image. Both types of endoscopes are larger and less sensitive than Kahn's model.

Though he's excited about his next-generation technology, Kahn said he doesn’t know how long it will be until the micro-endoscope reaches the O.R. 

“I think the technology could be developed into a field-ready form within a couple of years, so it probably could be used in research in that time frame,” he said. “I have no idea how long it would take to get approval to use it in human clinical applications.”

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