BOSTON, Jan. 14, 2013 — Physicians may soon have an easy and painless way to screen the esophagus for precancerous cellular changes, thanks to a pill-size device that provides detailed imaging of the upper gastrointestinal tract.
Developed by researchers at the Wellman Center for Photomedicine at Massachusetts General Hospital (MGH), the system involves a capsule containing optical frequency domain imaging (OFDI) technology — a rapidly rotating laser tip emitting a near-infrared beam of light and sensors that record light reflected back from the esophageal lining. The technique offers several advantages over traditional endoscopy methods for detecting Barrett’s esophagus, a precancerous condition caused by chronic exposure to stomach acid.
The inch-long endomicroscopy capsule contains rotating infrared laser and sensors for recording reflected light. Images courtesy of Michalina J. Gora, PhD, and Kevin A. Gallagher, Wellman Center for Photomedicine, Massachusetts General Hospital.
“This system gives us a convenient way to screen for Barrett’s that doesn’t require patient sedation, a specialized setting and equipment, or a physician who has been trained in endoscopy,” said Dr. Gary Tearney, a pathologist at MGH and co-author of a report that appeared online in Nature Medicine
). “By showing the three-dimensional, microscopic structure of the esophageal lining, it reveals much more detail than can be seen with even high-resolution endoscopy.”
The laser “pill” is attached to a stringlike tether that connects to the imaging console and allows a physician to control the system. After the capsule is swallowed by a patient, normal contractions of the surrounding muscles carry it down the esophagus. When it reaches the stomach entrance, it can be pulled back up by the tether. The OFDI images are taken throughout the capsule’s transit down and up the esophagus.
The researchers tested the system in a group of unsedated participants — six with Barrett’s esophagus and seven healthy volunteers. The physicians operating the system imaged the entire esophagus in less than a minute. A procedure involving four passes — two down the esophagus and two up — could be completed in about six minutes. A typical endoscopic examination requires a patient to stay in the endoscopy unit for about 90 minutes.
Detailed microscopic images produced by the OFDI system revealed subsurface structure not easily seen with endoscopy and clearly distinguished the cellular changes that signify Barrett’s esophagus.
By manipulating the plastic ball attached to the flexible tether (lower, right hand) the system operator can control the position of the endomicroscopy capsule in a patient’s esophagus.
“The images produced have been some of the best we have seen of the esophagus,” said Tearney, a professor of pathology at Harvard Medical School and an MGH Research Scholar. “We originally were concerned that we might miss a lot of data because of the small size of the capsule; but we were surprised to find that, once the pill has been swallowed, it is firmly ‘grasped’ by the esophagus, allowing complete microscopic imaging of the entire wall.”
Other methods tried by the team compressed the esophageal lining, making it difficult to obtain accurate, 3-D images, Tearney said.
Current Barrett’s esophagus diagnostic recommendations rely on endoscopic screenings of men with chronic, frequent heartburn and other gastroesophageal reflux disease symptoms. This new technique, however, could “screen larger groups of patients, with the hope that close surveillance of patients found to have Barrett’s could allow us to prevent esophageal cancer or to discover it at an earlier, potentially curable stage,” said co-author Dr. Norman Nishioka. “But we need more studies to see if that hope would be fulfilled.”
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