Pill-sized device provides detailed imaging of oesophageal lining
14 January 2013
Physicians may soon have a new way to screen patients for Barrett's oesophagus, a precancerous condition usually caused by chronic exposure to stomach acid.
Researchers at the Wellman Center for Photomedicine at Massachusetts General Hospital (MGH) have developed an imaging system enclosed in a capsule about the size of a multivitamin pill that creates detailed, microscopic images of the oesophageal wall. The system has several advantages over traditional endoscopy.
"This system gives us a convenient way to screen for Barrett's that doesn't require patient sedation, a specialised setting and equipment, or a physician who has been trained in endoscopy," says Gary Tearney of the Wellman Center and the MGH Pathology Department, corresponding author of the report receiving online publication in Nature Medicine. "By showing the three-dimensional, microscopic structure of the oesophageal lining, it reveals much more detail than can be seen with even high-resolution endoscopy."
The system developed by Tearney and his colleagues involves a capsule containing optical frequency domain imaging (OFDI) technology - a rapidly rotating laser tip emitting a beam of near-infrared light and sensors that record light reflected back from the oesophageal lining. The capsule is attached to a string-like tether that connects to the imaging console and allows a physician or other health professional to control the system.
After the capsule is swallowed by a patient, it is carried down the oesophagus by normal contraction of the surrounding muscles. When the capsule reaches the entrance to the stomach, it can be pulled back up by the tether. OFDI images are taken throughout the capsule's transit down and up the oesophagus.
The researchers tested the system in 13 unsedated participants - six known to have Barrett's oesophagus and seven healthy volunteers. The physicians operating the system were able to image the entire oesophagus in less than a minute, and a procedure involving four passes - two down the oesophagus and two up - could be completed in around six minutes.
A typical endoscopic examination requires that the patient stay in the endoscopy unit for approximately 90 minutes. The detailed microscopic images produced by the OFDI system revealed subsurface structures not easily seen with endoscopy and clearly distinguished the cellular changes that signify Barrett's oesophagus. Study participants who had previously undergone endoscopy indicated they preferred the new procedure.
"The images produced have been some of the best we have seen of the oesophagus," says Tearney. "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 oesophagus, allowing complete microscopic imaging of the entire wall.
"Other methods we have tried can compress the oesophageal lining, making it difficult to obtain accurate, three-dimensional pictures. The capsule device provides additional key diagnostic information by making it possible to see the surface structure in greater detail"