Biomedical Engineering Reference
In-Depth Information
Current GI endoscopes can be categorized into two major groups: wired
active endoscopes and wireless passive capsule endoscopes. Much work has been
reported in the former category (Kassin
et al.
2003). Modern fiber-optic based
endoscopy made visualization of the whole stomach, upper small intestine and
colon possible. Unfortunately, the procedures used for the examination, namely
gastroscopy, push enteroscopy and colonoscopy, respectively, cause discomfort
and pain to the patients because they require flexible, relatively bulky cables to
be pushed into the GI tract. These cables are necessary to carry light by fiber-
optic bundles, provide power and transmit video signals. Push enteroscopy in
particular is severely constrained by limitations of how far it can be advanced into
the small intestine. There is always some 15
20 feet of small intestine below the
reach of push enteroscope and above the reach of colonoscope. Despite all the
drawbacks, wired active GI endoscopy is still the most effective and widely used
diagnostic and therapeutic procedure in dealing with diseases of the GI tract.
The wireless passive capsule endoscope is represented by a commercial prod-
uct developed by Given Imaging Ltd (Givenimaging). The capsule contains a
miniature camera for imaging, a wireless transmitter to send out the colored
images of the GI tract to a portable recording device, and is self-powered by
a battery cell without any externally connected wires or cables. The working
principle of the wireless passive capsule endoscope is rather straightforward.
During the examination, the patients just swallow the capsule and the capsule
takes photos and transmits the images to the data recorder outside of the human
body while going through the GI tract from mouth to anus by natural peristalsis,
which takes about 8 to 24 hours.
Wireless capsule endoscopy has been proved to be a convenient, painless and
effective diagnostic procedure, especially for the small intestine. However, the
capsule endoscope depends on the peristalsis for moving passively in the GI tract;
hence they are forced to go forward without the possibility of stopping, turning,
going back or speeding during their journey, which causes a series of limitations
in the diagnosis. Firstly, the long examination time (at least 8 hours) usually
exhausts the battery power before the excretion of the capsule, which results in
that the distal small intestine, where most ileum inflammatory diseases occur, is
unreachable for over 25% of the capsules (Kornbluth
et al.
2004). Secondly, the
passive capsule may miss some interesting spots. Medical reports show that 75%
of the second swallow of the passive capsules have new findings, and 62.5% of the
new findings lead to the change of the final decision Rondonotti 2005. Multiple
swallows may reduce the rate of missing diseases, nevertheless, the cost increases
accordingly.
Next generation of active capsule endoscope, which is equipped with a
locomotion mechanism, would allow interactive endoscopy in a totally controlled
manner, enabling the surgeon to steer the capsule towards the more interesting
pathological areas, with future potential to accomplish other related medical tasks
such as biopsy and drug delivery in situ. An active capsule endoscope is a world-
wide perception shared by the endoscopists and bio-robotic engineers (Kornbluth
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