A laser-based imaging system enclosed in a capsule about the size of a multivitamin is the creation of researchers at the Wellman Center for Photomedicine at Massachusetts General Hospital (MGH; Boston, MA). Able to create detailed, microscopic images, the device was designed for use in screening patients for Barrett's esophagus, a major precursor to esophageal cancer. It has several advantages over traditional endoscopy.1
The inch-long capsule incorporates optical frequency domain imaging (OFDI) technology, a form of optical coherence tomography (OCT): A quickly rotating laser tip emits near-infrared (NIR) light, while tiny sensors record light reflected back from the esophageal lining. Optical fiber links the capsule to an imaging console, which allows a clinician to control the system.
|This one-inch endomicroscopy capsule, tethered to a console by optical fiber, contains a rotating infrared laser tip along with sensors that record reflected light. (Image courtesy of Michalina Gora, Ph.D., and Kevin Gallagher, Wellman Center for Photomedicine, Massachusetts General Hospital)|
In clinical use, the patient swallows the capsule, which is carried down the esophagus by normal muscle contraction. When the capsule reaches the entrance to the stomach, the clinician can pull it out using the fiber-optic tether. The system records images on the way down and up the esophagus. It enables a screening approach that does not require patient sedation, a specialized setting and equipment, or a physician trained in endoscopy, according to Gary Tearney, professor of pathology at Harvard Medical School and co-inventor of the technology. By highlighting the microscopic structure of the esophageal lining in three dimensions, it also reveals much more detail than even high-resolution endoscopy. Whereas a typical endoscopic examination requires the patient remain in the endoscopy unit for about 90 minutes, in tests with unsedated participants, physicians using the system were able to image the entire esophagus in less than a minute. A procedure involving two passes down the esophagus and two up took about six minutes. The resulting imagery revealed subsurface structures not easily seen with endoscopy that clearly highlighted cellular changes signifying Barrett's esophagus. Patient participants who had previously undergone the standard endoscopic procedure reported a preference for the new procedure.
"An inexpensive, low-risk device could be used to screen larger groups of patients," said study co-author Norman Nishioka, MD, of the Wellman Center and MGH Gastroenterology. He added that close surveillance of patients found to have Barrett's could perhaps prevent the development of esophageal cancer, or allow discovery at an earlier, potentially curable stage. "But we need more studies to see if that hope would be fulfilled."
1. M. J. Gora, Nat. Med., 19, 238–240 (2013); doi:10.1038/nm.3052.