The blog of Xeno, a slightly mad scientist
You can get an X-ray to see your bones, an MRI to see your brain, and a CT scan to see virtually everything else. But getting a glimpse of the gastrointestinal tract (the esophagus, stomach, and intestines) is a little more invasive. Endoscopes have been able to provide doctors with a picture of their patients’ insides, but they have their limitations: For instance, the person performing the endoscopy needs extensive training on guiding the camera down the patient’s throat. It’s also a time-intensive procedure that requires the patient to be sedated.
A group of doctors and engineers working at both Ninepoint Medical and Massachusetts General Hospital developed a new endoscope that gets around these hurdles by thinking small. As reported in a recent study in Nature Medicine, they miniaturized the endoscope to fit the imaging equipment into a clear capsule patients can swallow. One end of the capsule is attached by a 1-mm-wide cable tethered to a console near the patient. When it reaches the stomach, the doctor can reel it back in and take snapshots of the GI tract on its return trip. Michalina Gora, lead author of the study and a research fellow at Massachusetts General Hospital, says that one of her biggest concerns was how patients coped with a long string dangling in their throat. “Sometimes, the procedure triggered a gag reflex in the patient,” she says. “This can be taken care of just by breathing steadily, in and out. It opens up the GI tract’s sphincters and allows the endoscope to pass through.” Overall, patients prefer the swallowable endoscope to the standard version because the scan takes less time (about 5 minutes) and doesn’t require sedation.
Instead of a standard camera to take pictures, the endoscope uses a laser to scan its surroundings. Then its imaging equipment tracks the reflectance of the laser beam as it scans not only the surface of the GI tract, but also cell layers beneath it, producing 3D imagery. “It’s kind of like ultrasound imaging,” says Brett Bouma, a co-author of the study and a professor at Harvard Medical School. “You measure the time it takes for the laser to bounce back, and determine the distance.” Bouma and his colleagues have been able to use their endoscope to identify people with Barrett’s esophagus, a disorder where the lining of the esophagus changes shape because of stomach acid seeping through.
In addition to packing a camera into a capsule, the team also needed to find a way to handle the 100 gigabytes of data their endoscope generates. As new data is collected, old data is simultaneously piped through a hard-drive array and converted into a viewable image. Bouma says that the endoscope’s CPU can generate a real-time display at 20 frames per second, which he describes as “pretty adequate for comfortable viewing.” Eric Seibel, a professor of mechanical engineering at the University of Washington, who is not associated with this project, says the new imaging technology is promising but might encounter some stumbling blocks if it were brought into the clinic. The new endoscope’s pictures can be difficult to interpret because they aren’t the type of pictures doctors are accustomed to; instead, they look more like samples under a microscope. “Clinicians and pathologists have to look at the body in a different way than they’re used to,” he says.
Despite this stumbling block, he has high hopes for the potential of pill-size endoscopes. “Sedation accounts for one-third of the procedure’s cost,” he says. Because the new procedure is cheaper, it can be incorporated into routine physical exams. “You can look for diseases in the very early stages before any symptoms come up.”