First human trial of tethered capsule endoscope
Deaths from esophageal cancer are often preventable. Before full-blown cancer develops, a noticeable change occurs in the esophageal lining, a condition known as Barrett’s esophagus. At this stage, the tumor is highly treatable, but once it progresses, less than 15 percent of patients survive. Often, traditional endoscopy is not employed until it is too late because it requires expensive anesthesia, owing to difficulty swallowing the 9-mm-diameter tube.
In contrast, a novel procedure developed at the University of Washington in Seattle called tethered capsule endoscopy uses a 1.4-mm-diameter tube with a swallowable capsule on one end and, therefore, does not require anesthesia. The tethered procedure also has advantages compared with a related technique called wireless capsule endoscopy.
Engineers recorded these images of the human esophagus with a tethered capsule endoscope. Reprinted with permission of IEEE Transactions on Biomedical Engineering.
In wireless capsule endoscopy, a patient swallows a small pill-shaped camera that moves through the digestive tract, wirelessly transmitting images to a remote recorder. However, it provides only random views of the esophagus because the doctor cannot control the camera, and it costs even more than the traditional procedure, in part because the $400 camera is discarded after use. In contrast, tethered capsule endoscopy enables control of the capsule, and the capsule and tether potentially are reusable.
To scan the esophagus, a piezoelectric tube within the capsule rotates and moves an optical fiber back and forth. The fiber serves as a conduit for the combined light from red, blue and green laser diodes attached at the other end. Light backscattered from the esophageal tissue is collected within the capsule by six multimode optical fibers that surround the scanner compartment. The backscattered light ultimately travels to photomultiplier tubes in a console outside the patient’s body, which also contains the laser diodes.
Using software, these data are then displayed as a full-color two-dimensional video of the esophagus or as a mosaic of stills. The researchers said that side-by-side comparison of these stills could be useful for radiological evaluation and patient consultation.
The device records images of the esophagus at 30 Hz with 500-line video resolution or 50-μm for stills, according to team leader Eric J. Seibel. Depending on scanner movement, it also can record with 1000-line resolution at 15 Hz or at 60 Hz with 250-line resolution, for example. The engineers have tested the device in a live pig and now in a human. Seibel swallowed the capsule and reported that he felt no discomfort. These experiments are detailed in the March 2008 issue of IEEE Transactions on Biomedical Engineering.
The researchers are discussing its commercialization. They point out that the device is compatible with narrow-band, hyperspectral and fluorescence imaging. The next step is to produce it inexpensively.
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