24-01-2013, 04:37 PM
Wireless Robotic Capsule Endoscopy: State-of-the-Art and Challenges
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Abstract
This paper surveys the state-of-the-art in wireless
capsule endoscopy in terms of commercially available products
and prototypes currently under development in research labs
worldwide. Challenges facing us in designing and manufacturing
active wireless capsule endoscopes are outlined, together with
gotential methods to tackle them.
intestine endoscopy and colonoscopy, respectively, cause
discomfort and pain to the patients because they require
flexible, relatively bulky cables to be pushed into the intestine.
These cables are necessary to light by fiber-optic
bundles, provide power and transmit video Smallintestine
endoscoov in oarticular is\severelv constrained bv
Index Terms ? Wireless capsule endoscope, active capsule
endoscope, robotic medical devices, micro medical devices
INTRODUCTION
Diseases of the Gastrointestinal (GI) tract, such as stomach
and colon cancers and ulcerative colitis, are common in most
countries. According to a publication of the Hong Kong
Cancer Registry in March 2003 [I], the cancer caseload in
Hong Kong has been increasing. The number of new cancer
cases was over 21,000 in the year 2000, of which GI tract
related cancers of the colon, rectum and stomach ranked
number 2, 5 and 7, respectively. Cancer is the leading cause of
death in Hong Kong, accounting for over one third of all
deaths. In 2000, 6,943 men and 4,279 women died of cancer.
GI tract related cancers of the colon, stomach, and rectum
ranked number 3,4, and 5 causes of cancer death, accounting
for 18% of the total cancer deaths in Hong Kong in 2000.
Most GI related cancers can be cured if they are detected
at. their early stages. There are several methods to detect
diseases of the GI tract without applying intrusive devices into
the human body, such as stool test, double-contrast barium
enema and more recently genetic analysis just among many
others. However, conventional GI endoscopy is irreplaceable
because it enables diagnosis based on analysis of real images
and biopsy samples. Many research institutions and industries
have embarked on the effort to improve conventional GI
endoscopy procedures. Pbee et al [2][3] presented thorough
surveys of the related results. Current GI endoscopes can he
categorized into two major groups: wired active endoscopes
and wireless passive capsule endoscopes. Much work has
been reported in the former categoly [2]-[7]. Modem fiberoptic
based endoscopy made visualization of the whole
stomach, upper small intestine and colon possible. The
procedures used to examine them, namely gastroscopy, small-
I
problems of discomfort and limitations of how f&
enteroscopes can be advanced into the small-intestine. There
is always some 15-20 feet of small intestine below the reach
of the gastroscope and small-intestine endoscope and above
the reach of the colonscope that can not be examined by using
conventional endoscopes. Even CT scan and MRI are not
useful in this circumstance. A procedure using X-rays, called
small bowel series, can be performed after drinking a chalky
solution of barium, which has a limited accuracy since X-rays
are still only shadow pictures and do not view the object itself
like a camera. Despite all the drawbacks, wired active GI
endoscopy is still the most effective and widely used
diagnostic procedure in detecting diseases of the GI tract.
In the second category of wireless passive capsule
endoscopes, the state-of-the-art is represented by a
commercial wireless capsule endoscope product, the M2A
capsule [8][9], developed by an Israeli company, Given
Imaging Ltd. The M2A capsule is equipped with a tiny CMOS
camera, a wireless transmitter to send out the images, and a
battery cell to power the device. The M2A capsule is
completely passive and it moves with the natural peristaltic
movement of the human GI system. Similar designs of
wireless passive capsule endoscopes to the M2A capsule were
reported by F. Gong et a1 [lo] and H.J. Park et a1 [Ill. FS
System Lab Company of Japan is in the process of developing
its own Ouper-micro capsule endoscope? code named Norika
[12]. Its design prototypes are published on its website. The
working principle of the wireless passive capsule endoscopes
is rather straightforward. During the examination, the patient
swallows the device and it takes about 8 to 24 hours for the
device to go through the human G1 system from the mouth to
anus, while it transmits out images of the patient's GI tract
wirelessly. Being a passive device easy and safe to use, it is
impossible to control the position and orientation of the
endoscope and it is thus possible to miss some interested
spots, at about 30%.
MAJORW ORK IN WIRELESS CAPSULE ENDOSCOPE
I-Optical dome; 2-Lens holder; 3-Lens; 4-White LEDs;
5-CMOS imager; 6-Battery; 7-Transmitter; 8-Antenna
The invention of fibre-optic endoscopy [I31 made
visualization of the GI tract possible. Since then various
endoscopic devices have been invented and applied to patients
[2]-[7]. The procedures of endoscope based examinations
cause discomfort because they require flexible, bulky cables
to he pushed into the bowel - these cables cany light by fibreoptic
bundles, power and video signals. Small-howel
endoscopy in particular is constrained by problems of
discomfort and limitations of how far they can he advanced
into the small bowel. There is a clinical need for improved
methods of examining the small bowel and colon, especially
in patients with GI bleeding. The invention of the transistor
made it possible to design swallowable electronic radio
telemetry capsules for the study of GI physiological
parameters. These capsules were first reported in the 1950s
and were used to measure temperature [14], pressure [14][15],
and pH [15][16]. Recent advances in CCD and CMOS image
sensors, ASIC design and white LED devices make it possible
to develop a new type of radiotelemetry capsule endoscopes
[8]-[IO], which are small enough to he swallowed (Ilmm by
27mm) and has no extemal wires, fibre-optic bundles, or
cables.
Given Imaging developed the passive wireless M2A
capsule endoscope [S][9], as shown in Figures 1 and 2. It is a
non-invasive diagnostic device for use in the GI tract. Natural
peristalsis moves the M2A capsule smoothly and painlessly
throughout the GI tract, transmitting color video images as it
passes. The procedure is ambulatory, allowing patients to
continue daily activities throughout the endoscopic
examination. The M2A capsule endoscopy closes the
diagnostic gap by enabling physicians to directly view the
entire small intestine, which can assist physicians in the
diagnosis and treatment of GI diseases. The problem with this
wonderful product is that it is completely passive and it needs
8 to 24 hours or more to go through the procedure. Since the
movement of the capsule is not controlled, missing diagnosis
is possible and extended observation of interested spots along
the GI tract is impossible, with some 30% missing rate