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Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang Chen Thèse INSA de Lyon, LAI 2005 25
Chapter1
From the problem of colonoscopy to the
solution of robotic colonoscopy
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 26
1 CHAPTER 1 FROM THE PROBLEM OF COLONOSCOPY TO THE SOLUTION OF ROBOTIC
COLONOSCOPY ............................................................................................................................................... 25
1.1 Introduction to the colonoscopy........................................................................................................ 27
1.1.1 Colon Cancer............................................................................................................................. 27
1.1.2 Colorectal cancer screening....................................................................................................... 29
1.1.3 Colonoscopy.............................................................................................................................. 33
1.1.4 Colonoscope.............................................................................................................................. 34
1.1.5 The colonoscopy examination................................................................................................... 37 1.1.6 Drawbacks of conventional colonoscopy .................................................................................................. 38
1.1.6.1 Complexity of the procedure for the surgeon........................................................................ 38
1.1.6.2 The pain and discomfort for the patient ................................................................................ 39
1.2 Overview of current efforts on the automation of colonoscopy (state of the art of robotic
colonoscopy) ................................................................................................................................................. 39
1.2.1 Locomotion mechanism ............................................................................................................ 41 1.2.1.1 Snake-like locomotion .......................................................................................................................... 40
1.2.1.2 Inchworm locomotion mechanism ........................................................................................ 43
1.2.1.3 Autonomous capsules............................................................................................................ 48
1.2.2 Steerable distal end.................................................................................................................... 49
1.2.3 Conclusions ............................................................................................................................... 53
1.3 Conclusions and our solution ............................................................................................................ 54
Gang CHEN Thèse INSA de Lyon, LAI 2005 27
1.1 Introduction to colonoscopy
Colorectal cancer is a major public health problem in many countries. Colorectal cancer
(which includes cancer of the colon, rectum, anus, and appendix) is the second leading deadly
cancer among men and women combined, second only to lung cancer in the United States. In 2005,
104,950 new cases of colorectal cancer will be diagnosed and 56,290 will die of this disease. Other
developed countries, such as France, the United Kingdom, have the same level of incidence. In
China, colon cancer incidence rates have been rapidly increasing in big cities in recent years. The
risk of developing colon cancer is increased for people more than 50 years old, and for those who
have previous incidents of colonic cancer within their family.
However, the great majority of these cancers and deaths could be prevented by applying
existing knowledge about cancer prevention and by wider use of established screening tests.
Screening can prevent many cases of colorectal cancer because most colorectal cancers develop
from adenomatous polyps. Polyps are noncancerous growths in the colon and rectum. Detecting
polyps through screening and removing them can actually prevent cancer from occurring.
Furthermore, being screened at the recommended frequency improves the chance that colorectal
cancers will be detected at an earlier stage [AME2005], when:
• The cancer is more likely to be cured by surgery alone.
• The surgery needed is less extensive, and the recovery from surgery much faster.
1.1.1 Colon Cancer
Colorectal cancer is a cancer that develops in the colon or the rectum. The colon and rectum are
parts of the digestive system, which is also called the gastrointestinal, or GI, system. The digestive system
processes food for energy and rids the body of solid waste.
After food is chewed and swallowed, it travels through the esophagus to the stomach. There it is
partially broken down and sent to the small intestine where digestion continues and most of the nutrients
are absorbed. The small intestine is actually the longest part of the digestive system- about 6 meters long.
Cancer almost never arises in the small intestine.
The small intestine joins the large intestine in the lower right abdomen. The first and longest part
of the large intestine is the colon, a muscular tube about 1.5 meters long with an average diameter of
50mm. Water and mineral nutrients are absorbed from the food matter in the colon. Waste left from this
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process passes into the rectum, the final 15 centimeters of the large intestine, and is then expelled (Figure
1.1).
The colon has 4 sections:
• The first section is called the ascending colon. It begins where the small intestine attaches to the
colon and extends upwards on the right side of a person’s abdomen.
• The second section is called the transverse colon since it crosses the body from the right to the
left side.
• The third section, the descending colon, continues downward on the left side.
• The fourth section is known as the sigmoid colon because of its S-shape. The sigmoid colon
joins the rectum, which in turn joins the anus.
Figure 1.1 Anatomy of the lower digestive system, showing the colon and other organs [NCI ]
Colorectal cancer usually develops slowly over a period of many years. Before a true cancer
develops, it usually begins as a noncancerous polyp which may eventually change into cancer. A polyp is
a growth of tissue that develops on the lining of the colon or rectum. Certain kinds of polyps, called
adenomatous polyps or adenomas, are most likely to become cancers. Once cancer forms in the large
intestine, it eventually can begin to grow through the lining and into the wall of the colon or rectum. The
extent to which a colorectal cancer has spread is described as its stage. Colorectal stages can be classified
as the following according to the seriousness of cancer:
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• Local: Cancers that have grown into the wall of the colon and rectum, but have not extended
through the wall into invade nearby tissues.
• Regional: Cancers that have spread through the wall of the colon or rectum and have invaded
nearby tissue, or that have spread to nearby lymph nodes.
• Distant: Cancers that have spread to other parts of the body, such as the liver and lungs.
1.1.2 Colorectal cancer screening
However, the great majority of these cancers and deaths could be prevented by applying
existing knowledge about cancer prevention and by wider use of established screening tests.
Screening can prevent many cases of colorectal cancer because most colorectal cancers develop
from adenomatous polyps. Polyps are noncancerous growths in the colon and rectum. Detecting
polyps through screening and removing them can reduce mortality both by decreasing incidence
and by detecting a higher proportion of cancers at early, more treatable stages [SMITH 01,
PIGNONE 02]. Therefore the American Cancer Society and the US Preventive Services Task Force
recommend that clinicians routinely provide colorectal cancer screening to all men and women
aged 50 and older. Persons at higher risk, for example those who have previous incidents of colonic
cancer within their family, should begin screening at a younger age and may need to be tested more
frequently.
Furthermore, being screened at the recommended frequency improves the chance that
colorectal cancers will be detected at an earlier stage [American Cancer Society 2005], when:
• The cancer is more likely to be cured by surgery alone
• The surgery needed is less extensive, and the recovery from surgery much faster.
Several options for colorectal cancer screening are recommended by the American Cancer
Society and other organizations to detect and diagnose colon cancer. These are summarized in
Table 1.1 [AME 2005] and described below.
• Physical exam and history: An exam of the body to check general signs of health, including
checking for signs of disease, such as lumps or anything else that seems unusual. A history of the
patient’s health habits and past illnesses and treatments will also be taken.
• Fecal occult blood test (FOBT): A test to check stool for blood that can only be seen with a
microscope. Small samples of stool are placed on special cards and returned to the doctor or
laboratory for testing.
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• Digital rectal exam: An exam of the rectum. The doctor or nurse inserts a lubricated, gloved
finger into the rectum to feel for lumps or abnormal areas.
• Barium enema: A series of x-rays of the lower gastrointestinal tract. A liquid that contains barium
(a silver-white metallic compound) is put into the rectum. The barium coats the lower
gastrointestinal tract and x-rays are taken, shown in figure 1.2. This procedure is also called a
lower GI series.
Figure 1.2 Barium enema procedure. The patient lies on an x-ray table. Barium liquid is put into the rectum and
flows through the colon [NCI].
• Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps,
abnormal areas, or cancer. A sigmoidoscope (a thin, lighted tube) is inserted through the rectum
into the sigmoid colon. Polyps or tissue samples may be taken for biopsy.
• Colonoscopy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or
cancer. A colonoscope (a thin, lighted tube) is inserted through the rectum into the colon, shown
in figure 1.3. Polyps or tissue samples may be taken for biopsy.
• Biopsy: the removal of cells or tissues so they can be viewed under a microscope to check for
signs of cancer.
• Virtual colonoscopy: A procedure that uses a series of x-rays called computed tomography to
make a series of pictures of the colon. A computer puts the pictures together to create detailed
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images that may show polyps and anything else that seems unusual on the inside surface of the
colon. This test is also called colonography or CT colonography.
Figure 1.3 Colonoscopy. A thin, lighted tube is inserted through the anus and rectum and into the colon to look
for abnormal areas [NCI].
Table 1.1 summarizes the advantages and disadvantages of some main test & diagnostics methods
from several aspects, such as performance, accuracy, complexity and cost. The sigmoidoscopy and digital
rectal exam method only performs the testing of the colon. Other diagnostics methods, such as fecal occult
blood test, barium enema and are effective methods with lowest complexity, but colonoscopy will be
needed if there are some abnormalities. Virtual colonoscopy seems to be an efficient procedure that takes
less time and causes less pain. However, the doctor cannot take tissue samples during VC, so a
conventional colonoscopy must be performed if abnormalities are found. Also, polyps smaller than 10
millimeters in diameter, may not show up on the images.
On the other hand, colonoscopy can detect colon disease of the entire colon, including the large
intestine which other solution are not available, with the highest accuracy. Also, colonoscopy is the only
method that can operate within the colon so that surgeons can undertake treatment of colon. However, the
procedure of colonoscopy is the most complex of all the solutions and the patient needs to take a day off
for the examination. It should be emphasized that, even if it is rare, colonoscopy can cause intestine
perforation, as well as pain and anxiety for the patient. We will describe colonoscopy in details later
because it can provide a systematic therapy as well as a method of examination with the highest
performance results.
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Table 1.1 Com
parison with different test procedures [A
ME 2005]
Cost range
Lowest cost: less than $20
Low to mid cost:$150-$200
mid to high cost: $300-$400
High cost: $400 or more.
Characteristics/ limitations
• Will miss most polyps and some cancers • May produce false-positive test results • Requires dietary limitations before testing • Must be done every year • For greater effectiveness, should be
combined with a flexible sigmoidoscopy every 5 years
• Additional procedures necessary if abnormalities are detected
• Visualize clearly only about one-third of the colon
• Cannot remove polyps • Can miss some small polyps and cancers • Very small risk of bowel tears or bleeding • More effective when combined with
annual fecal occult blood testing • Additional procedures needed if
abnormalities are detected
• Can miss some small polyps and cancers • Full bowel preparation needed • May produce false-positive test results • Additional procedures necessary if
abnormalities are detected
• Can miss small polyps and cancers, although more accurate than flexible sigmoidoscopy. Full bowel preparation needed
• Can be expensive • Usually requires some sedation • Generally requires missing a day of work • Carries potential risk of bowel tears or
infections.
Accuracy in
detecting cancer
and complexity
Intermediate for cancer Lowest complexity
High for up to one-third of the colon
Intermediate complexity
High High complexity
Highest Highest complexity
Performance & advantages
• No bowel preparation • Sampling is done at home • Low cost • Proven effective in
clinical trial • No risk of bowel tears or
infections
• Faily quick, few complications
• Minimal bowel preparation
• Done every 5 years • Minimal discomfort • Does not require a
specialist
• Can usually view entire colon
• Few complications • Done every 5 years No sedation needed
• Can usually view entire colon
• Allows biopsy and removal of polyps
• Done every 10 years Can diagnose other diseases
Test method
Fecal occult Blood test
Flexible sigmoidoscopy
Double-contrast barium enema
Colonoscopy
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1.1.3 Colonoscopy
As described before, colonoscopy allows the physician to look inside entire large intestine, from
the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. Figure
1.4 shows the anatomy of the digestive system. The procedure is used to look for early signs of cancer in
the colon and rectum. The main instrument that is used to look inside the colon is the colonoscope, which
is a long, thin, flexible tube with a CCD video camera and a light on the end. By adjusting the various
controls on the colonoscope, the physician can carefully guide the instrument in any direction to look at
the inside of the colon. A high quality image from the colonoscope that gives a clear, detailed view is
shown on a TV monitor. This procedure also allows other instruments to be passed through the
colonoscope for the purpose of minimally invasive surgery (MIS). They may be used, for example, to
painlessly remove a suspicious-looking growth or to take a biopsy-a small piece for further analysis. In
this way, colonoscopy may help to avoid surgery or to better define what type of surgery may need to be
done.
Figure 1.4 The anatomy of the digestive system [JACKSON ]
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1.1.4 Colonoscope
A flexible colonoscope is a special kind of endoscope which is used to detect colon cancer.
Now, these colonoscopes come in two types. The original purely fiberoptic instrument has a flexible
bundle of glass fibers that collects the lighted image at one end and transfers the image to the eye
piece (figure 1.5).
Figure 1.5 Fiberoscope photo with the intervention tool
The colonoscope also includes extra channels for infusing or withdrawing liquid or gas and for
passing instruments for electrosurgery, cautery, and for cutting and grasping. The use of such devices
has enabled viewing and treatment within the colon to be achieved without major surgery in some
cases. Figure 1.6 shows these accessories for colonoscope.
Figure 1.6 The accessory tools for an effective operation: the left is the video and the right is connection to
lighting source
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In the last thirty years, new technologies of imagery have encouraged the evolution of the
endoscope and its performances. It is necessary, however, to note that endoscopic tools did not carry
out honest evolutions from a mechanical point of view. Indeed, the guiding principle of the
movements of this tool has always remained the same one.
Although current colonoscopy systems are well designed, carefully manufactured, use state of
the art instruments, and represent the result of a continuous product evolution, they are conceptually
still the same devices introduced about 30 years ago with the same movement principle.
The mobility of the fibroscope is implemented by a cable-driven system which is actuated by two
knobs (figure 1.7a), which make it possible for the distal end to perform movements in two orthogonal
directions (figure 1.7b). The combination of these movements makes the instrument bend in all the
directions (360°) in a 3-D space. Most of the current colonoscopes have the capability to bend 160°.
(a.) (b)
Figure 1.7 The control of the colonoscope and its bending
The newer video endoscopes use a tiny, optically sensitive computer chip at the end.
Electronic signals are then transmitted up the scope to a computer which displays the image on a large
video screen.
Since Olympus is the provider of the colonoscopy system for the Hospital Edouard Herriot de
Lyon, our medical partner of the project, we will present the terminology and the characteristics of
OLYMPUS colonoscope in Figure.1.8. There are four main parts: the connector, the universal cord,
the handle and the introduction sheath.
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Figure 1.8 Terminology and the characteristics of OLYMPUS colonoscope
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1.1.5 The colonoscopy examination
Before the examination, the colon must be completely empty for the colonoscopy to be
thorough and safe. For the procedure, pain medication and a mild sedative are given to the patient for
comfort and relaxation during the exam. The physician will insert a colonoscope into the rectum and
slowly guide it into the entire colon. By using the image transmitted from the camera at the distal end,
the physician can carefully examine the lining of the colon, figure 1.8a shows the video of the colon.
This is done by rotating the knobs to make the scope bend, so that the physician can move it around
the curves of the colon. The scope also blow air into the colon, which inflates the colon and helps the
physician see better.
If anything abnormal is seen in the colon, like a polyp or inflamed tissue, the physician can
remove all or part of it using tiny instruments passed through the scope (figure. 1.8b). That biopsy is
then used for further analysis. If there is bleeding in the colon, the physician can pass a laser, heater
probe, or electrical probe, or can inject special medicine through the scope and use it to stop the
bleeding.
It should be emphasized that, although they are uncommon, bleeding and puncture of the
colon are possible complications of colonoscopy.
Colonoscopy takes 30 to 60 minutes. The sedative and pain medicine should keep the patient
from feeling much discomfort during the exam. Following the procedure, the patient will need to
remain at the colonoscopy facility for 1 to 2 hours until the sedative wears off.
(a) (b)
Figure 1.9 (a) is the photo of the colon from the examination; (b) the biopsy operation [JACKSON]
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1.1.6 Drawbacks of conventional colonoscopy
In the late 1960s, the colonoscope was first used for diagnosis and treatment of colon cancer
without the need for open surgery. Although it was developed nearly 40 years ago, colonoscopy is still
a skill which requires motivation, determination and dexterity. It has benefited humans in many
aspects a few decades ago. However, there is still room for further improvement. The drawbacks can
be classified as two aspects: the complexity of the procedure and the pain and discomfort of the
patient.
1.1.6.1 Complexity of the procedure for the surgeon
In order to perform a colonoscopy, the physician needs to insert a flexible tube about 1.6
meters in length into the patient for the purpose of observation, analysis and diagnosis. The
colonoscope is advanced by a variety of “in-and-out” maneuvers of the physician’s hands,
accompanied with pulling, wriggling, jiggling, shaking and torquing action to “accordion” the colon
on the colonoscope. During this procedure, there is also another important movement- the steering of
the distal end around the many bends of the colon. It requires many years of practice and training.
During the operation, the lumen may disappear from the surgeon’s sight, leading to a “red-out” when
the tip is against the colonic wall, or worse a “white-out,” when the tip stretches the colon wall. When
this happens, an inexperienced endoscopist may be disorientated and have difficulty looking for the
lumen. Perforation of colon may occur.
Furthermore, abrupt movements of the scope may result in tearing of the inner wall of the
colon, which may in turn lead to excessive bleeding. The present colonoscope also requires the
physician to hold the control device with one hand leaving only one hand to push or pull the insertion
tube. Too much torquing of the insertion tube may result in loops, which may complicate matters
further (figure 1.10). However, this rarely occurs in reality. Besides being cumbersome, holding up the
control device for prolonged periods of time is tiring for the physician.
Figure 1.10 loops in the insertion tube in a X-ray.
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Currently, the colonoscopy procedure depends very much on the skill of the surgeon. A more
experienced physician will perform a more thorough, less painful operation in a shorter amount of
time than an inexperienced physician.
A skilled physician will normally have few problems traversing the colonoscope right up to
the caecum of a “normal” colon. However, there will be difficulties traversing the colonoscope
through some “difficult ” colons. This happens when encountering very acute or fixed bends. Further
pushing of the colonoscope at this point will only distend the walls of the distal colon. Distortion of
the colon shape and profile due to previous surgery may add to this problem.
Polyp removal from the colon walls can also cause difficulties. If there are a few polyps
present, the surgeon will have to remove them one at a time. If the polyps are large, the colonoscope
may have to be reinserted to look for the next polyp. Small polyps may often be retrieved with a
polyps trap. A biopsy net may be used to collect polyps and reduce this problem. However, one cannot
then distinguish which location in the colon a particular polyp comes from. It is important for the
physician to know which part of the colon a particular polyps is removed from if subsequent therapy
becomes necessary after histological examination.
1.1.6.2 The pain and discomfort for the patient
During the procedure, the air is filled in to distend the colon for the facility of the introduction
of colonoscope to the colon. This action causes discomfort for the patient and other reasons for the
pain to the patient are perforation and bleeding. Although colonoscopy is a safe procedure, perforation
can sometimes occur. This is a puncture of the colon wall, which could require additional surgery.
Bleeding also happens when a biopsy is performed. Heavy bleeding may result and sometimes this
requires a blood transfusion or reinsertion of the colonoscope to control the bleeding. Furthermore, an
inexperienced physician may cause additional pain by using the wrong technique or too much
unnecessary force. Even an experienced physician many cause pain if the patient is anxious, suffering
from irritable bowel syndrome, or if the colon is fixed by adhesion or disease.
1.2 Overview of current efforts on the automation of colonoscopy
(state of the art of robotic colonoscopy)
As it is analyzed in previous section, colonoscopy is an important procedure for inspection and
treatment of colon cancer, which ranks second among cancer deaths in most of the developed
countries. However medical experts predict that the death toll due to colon cancer could drop by 50%
to 75% with mass screening of the population. Unfortunately, due to the pain and discomfort
experienced by the patient, flexible colonoscopy procedure is very unpopular. Physicians also
complain of the high technical requirements and difficulties involved in introducing long, flexible
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shafts into the patient’s anus [COT 90]. These difficulties are explained in the complicated procedure
described before: the need to insert the traditional colonoscope into the colon which is long and soft
and the difficulty of maneuvering of the distal end without direct control. Thus great efforts have been
made on the automation of colonoscopy which was first proposed in the review [PHEE 97] (also can
be called robotic colonoscopy). By automating colonoscopy with the aid of robots, the problems
mentioned above may be solved efficiently because of the following advantages to this approach:
• Automation removes the need for experience and skills of the operator. This means that a
patient will have the same treatment, in terms of time taken and comfort, regardless of the
physician performing the examination.
• Training of a physician may be reduced to learning treatments for abnormalities found on the
intestinal walls, without the need to perfect the manual skills required to use a conventional
colonoscope.
• With an automated procedure, more operations can be done by one surgeon, since only
diagnostics will be required, thus reducing costs.
• Reduced trauma and discomfort for patients.
• Reduction of postoperative complications and hospitalization.
With the automation of colonoscopy, the skills of the surgeon will no longer be the dependent
factor. Instead, the integration of robot into the colonoscope will make the procedure faster, more
precise and consistent. The surgeon, however, must guide the machine to do its job. It is still the
person who will decide every move the computer makes and who will take over when there are
uncertainties or in case of an emergency.
So far, there are two different kinds of approaches that focus on the design of new medical
instruments for colonoscopy according to the minimally invasive surgery (MIS). The first class aims
to increase the dexterity of the traditional colonoscopy by adding active [IKUTA 88] or passive
[STURGES 91] degrees of freedom to the distal end of the structure. This approach emphasizes the
creation of the new bendable tip to facilitate the insertion through the intestinal bends while the
introduction action is still kept for the physician. In this sense, the approach is called the semi-
autonomous colonoscopy. The other approach aims to drastically change the way the examination is
performed, which is also called autonomous colonoscopy. Instead of inserting the colonoscope into the
colon by the physician, the new design has the ability to propel itself into the whole colon. Although
they differ in their design mechanism, the two classes can be considered using two aspects of an
intervention: locomotion design and design of the steerable distal end, which are the two main actions
during a colon intervention. The following section will look at the related research into robotic
colonoscopy done by researchers in terms of these two aspects.
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Gang CHEN Thèse INSA de Lyon, LAI 2005 41
1.2.1 Locomotion mechanism
For the automated colonoscope, the most important concern is to design a robot that can
propel itself through the whole colon without hurting the colon wall. The human colon is a long
channel of varying shape and diameter, whose walls can be silky smooth at one section or thrown into
turbulent folds in another, yet at some points can be dry and rough. To make matters worse, the layout
of the colon consists of unpredictable flexible 3-D curves and bends, which are nearly impossible to
describe mathematically. To design a robot that can accommodate such variations and propel itself
through the entire organ poses great challenges. [PHEE 97] summarized the following criteria when
building a robotic colonoscope.
• The body of the robot must be flexible enough to conform to the acute bends found in the colon.
Any rigid distances must be kept to a minimum. Generally, the robot’s body surface (excluding
the propulsion mechanism ) must be smooth and well lubricated to reduce friction as it slides
against the colon walls.
• The rigid diameter of the robot should not be greater than 29 mm, which is the smallest average
internal diameter of the colon.
• The robot must be capable of compelling itself right up to the caecum for a thorough colonoscopy
examination.
• The propulsion mechanism is preferably arranged at the distal end of the robot, so that its path will
not be restricted by the curves and bends found in the colon.
• Any mechanism used to grip onto the colon walls must be blunt and preferably made of a soft
materiel. Hard objects with sharp edges will easily damage the delicate colon walls.
• The robotic colonoscope must have cavities running through its length to allow optical fibers,
air/water tubing, and surgical tools to pass through to its distal end.
The animal kingdom has provided inspiration in the study of various locomotion techniques. In the
field of robotic colonoscopy, much of the development simulates the way an animal moves: snake,
inchworm and others.
1.2.1.1 Snake-like locomotion
Most snake species move by using their ventral scales, the scales on the undersides of their
bodies, to pull themselves across rough surfaces. They use a serpentine locomotion movement, in
which the body assumes a position of a series of S-shaped horizontal loops and each loop pushes
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against any surface resistance. [IKUTA 88], pioneers in this field, developed an “active endoscope”
that uses Shape Memory Alloy (SMA) in 1988. They made use of the resistance of the SMA in a
feedback control scheme to guide the snake-like robot around obstacles. The SMA tendons were
arranged about a spine so that each section can bend in three dimensions, as shown in Figure 1.11(a).
(a) (b)
Figure 1.11(a) the inner structure of an active endoscope (b) sequence motion in the sponge rubber colon
[IKUTA 88]
The SMA springs were connected mechanically in parallel, but electrically in series. This arrangement
increased the absolute value of electric resistance of the SMA, without any reduction of its
performance. This also eliminated the need for sensors such as potentiometers and encoders. The
driving mechanism of each segment consists of a stainless-steel coil spring, which acts as the main
skeleton at the center of a joint, and a series of SMA coil springs arranged around the joint. In this
model, each segment has one degree of freedom, so that a pair of SMA actuators, which are capable of
antagonistic motion, are arranged in symmetry with respect to the axis. It is this antagonistic activation
of the SMA springs that brings about the required bending motion. The basic design of the active
endoscope model was done by considering its application to a fibersigmoidscope. For this purpose, the
endoscope has enough mechanical compliance to pass through the sigmoid colon. It has a 13mm
diameter, which is comparable with endoscopes in the market of 10 to 20mm. This model has five
sections, comprised of four sections with flexibility in the same direction on a plane and one section of
the tip which can bend orthogonally to this plane just like traditional endocsope. The snake was
operated manually via a joy stick. Figure 1.11b shows the test results in a colon model environment.
The snake robot proved to have a maximum bending angle of 60° at the responding speed high enough
for the purpose.
[STURGE 91 ] proposed an idea of a spine in a floppy state that could slide through an
endoscope and then made rigid so that the endoscope itself can slide over the spine which guides it
around bends and prevents looping. A flexible, tendon-controlled bead-chain device was designed that
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incorporates the “slide motion” scheme to traverse into the colon. The robot consists of two major
parts: one or two “spines” and an endoscope conduit, which is a covering tube for the spine, Figure
1.12.
Figure 1.12 cross-section of endoscope with controllable stiffness spine [STURGES 91]
The spine was made up of a series of a close fitting balls and sockets arrangement, as shown in
figure 1.13a. Initially, the fittings are free to rotate but as the cable that runs along the axis of the spine
is tightened, friction is developed between the fittings and ultimately there is an increase in the
apparent stiffness of the entire chain. To summarize, pulling the cable stiffens the bead chain and
relaxing the cable tension force loosens it. Figure 1.13b shows a stiffened bead chain.
(a) (b)
Figure 1.13(a) Alternating bead-shape sequential chain figure;(b) Bead chain [STURGE 91]
1.2.1.2 Inchworm locomotion mechanism
An inchworm moves by alternately extending and distending sections of its body to produce
peristaltic waves that drive it through the soil. This type of locomotion is particularly suited to
unstructured or even hostile environments where wheels and tracks fail [HIROSE 93]. An inchworm
device would function especially well in a tubular, 3-D terrain. Realizing its potential, various
researchers have developed pipe inspection devices [ANTHIERENS 99, FUKUDA 89 ] based on this
inchworm-type locomotion. In the endoscope field, [FRAZER 79] first adopted the self-propelled
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 44
mechanism to robotic colonoscopy. He filled a patent in 1979 illustrating the robotic sequence. An
endoscope is disclosed having a propulsion mechanism and at least one transmitter at the distal end
transmitting bursts of energy waves (radio frequency or ultrasonic) used for tracking the position of
the distal end through the use of two or more transducers on the anterior or lateral surfaces of a patient.
The propulsion mechanism may consist of two radically expandable bladders separated by an axially
expandable bellows with only the forward bladder attached to the distal end so that by expanding and
contracting them in proper sequence, propulsion of the endoscope is achieved. The most critical factor
was to assure adequate friction to anchor the inflated bladder onto the colon walls so that it becomes
the base for the subsequent bellow’s expansion and deflation.
Figure 1.14 inchworm-based robotic endoscope [SLATKIN 95]
[SLATKIN 95, BURDICK 94] used the similar locomotion technique and developed an
inchworm robotic endoscope that can have many similar sections, as shown in figure 1.14. One
prototype is composed of 3 grippers and 2 extensor actuators with a diameter 22.2 mm and the length
of 183-200 mm at the contacted and stretched state. The grippers are toroidal, inflatable balloons that
are attached onto the outside of each segment. The primary purpose of the grippers is to provide
traction against the wall by expanding radically outward. Extensors are made of rubber bellows which
connect the grippers at its two ends. They extend or retract like pneumatic cylinders when high or low
pressure air is introduced, respectively. For the locomotion control, each actuator, extensor, or gripper
is controlled by its own miniature solenoid valve located within the robot itself. A control bus extends
through the robot, linking all the solenoid valves. This bus is connected to a controller and a
receiver/transmitter that controls the movement of the robot as a whole. Some things to note for this
design are that the bracing action must be strong enough to prevent slipping of the robot for the
operation in the colon. Another noteworthy aspect is that the sequence involved in the inchworm mode
of locomotion can be extensively varied depending on the gripper/extensor configuration. This robotic
endoscope prototype has been tested in the intestine of a pig. The reported experimental results in vivo
were positive, but the authors pointed out that the adhesion was not adequate to provide satisfactory
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 45
traction. Furthermore, since the work environment of endoscope is soft and slippery, the locomotion
efficiency can be a vital problem for the colonoscopy.
Figure 1.15 Automated colonoscope designed by [WALTER 95]
[WALTER 95], research at the Rochester Institute of Technology, also developed an
automated colonoscope. Similar to Burdick’s robotic endoscope, balloons are used in their design to
grip onto the colon walls. To lengthen and shorten the colonoscope, a push-pull flexible rod is used.
The back-end balloon is connected to the outer sheath of the flexible rod, whereas the front-end
balloon is connected to the inner core of the flexible rod. A pneumatic cylinder is used to drive the
core in and out of the outer sheath. By employing the inchworm method, the robot can be propelled
into the colon, as illustrated in Figure. 1.15.
Since the activation of the extension mechanism is from the proximal end and outside the
patient’s body, extension and retraction motions are more positive and more robust than most of the
earlier mentioned designs. However, due to the presence of relative motion of the push-pull rod with
respect to the colon walls, friction may be of concern. Friction force depends on the area of contact
between the flexible rod and the colon walls. It is also dependent on the degree of curvature through
which the rod is made to bend. Furthermore, buckling may occur at the distal end of the push-pull rod
if the stroke, pushing the front-end balloon forward, is too long.
Instead of using an inflated balloon as the clamping mechanism on the colon walls,
[CARROZZA 96, CARROZZA 97, DARIO 97, 99] utilize another clamping method which uses
suction as the base of generating friction. As reflected in figure 1.16, suction is provided by a number
of small holes disposed along the actuator’s surface. The prototype clamping actuator comprises four
series of eight holes with diameter of 1mm. When a vacuum is introduced, the negative pressure at the
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 46
small holes will cause the clamping actuator to ‘suck’ onto the colon wall thus attaching the micro-
robot. The central module is used for extension. By a sequence of activating the extension and
clamping mechanism, the micro-robot can traverse up the colon using the inchworm method of
locomotion, shown in Figure 1.17.
Figure 1.16 Inchworm robot designed by [DARIO 97 ]
Figure 1.17 sequence of inchworm propulsion steps of the microrobot [CARROZZA 96]
Suction does generate traction onto the colon however undesirable lesions may appear when
the vacuum pressure is increased beyond a certain value. [MENCIASSI 01] improves the gripping
efficiency by introducing a new clamping mechanism which integrates suction and mechanical
clamper. As shown in the figure the clamping mechanism is placed into the colon with its jaws
opened. The vacuum is introduced thus causing the surrounding tissue to collapse into the open jaw.
After which the jaw closes therefore clamping the tissue and hence achieving a positive grasp. A
prototype, as shown in figure.1.18, was developed and a vivo experiment on a pig was conducted. It
was recorded that the robot transversed a distance of 55cm from the anus after which the device was
observed to remain stationary. It demonstrated high stretch length and clamping efficiencies however
the low retraction efficiency affects the overall locomotion performance.
Figure 1.18 robot developed by [MENCIASSI 01]
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 47
On the basis of this model, [KIM 02, 03] in collaboration with IMC, Seoul, Korea, developed an
improved version of the semi-autonomous colonoscope with shape memory alloy steerable and
telescopic tip, complementary metal-oxide-semiconductor (CMOS) camera, light-emitting diode
(LED) illumination system, and very long stroke (about 12cm) (figure 1.19 ). During several in vivo
tests on pigs, this prototype showed the same performance as traditional colonoscope in terms of
distance traveled.
Figure 1.19 Integrated robot for colonoscopy [KIM 02]
[ASARI 00, KUMAR00] proposed a design which was comprised of an extensor module
sandwiched between two clamper modules, as shown in Figure 1.20. A new concept of clamping the
colon wall based on the passive vacuum devices is forwarded in Figure 1.21. Each clamper module is
a closed toroidal balloon with six passive vacuum cups embedded onto its interface to give it a better
grip. The extensor module was designed with three parallel pneumatic bellows which allows both
axial extension as well as bending of the robot’s tip. When the pressure in the three bellows is equal,
the extensor module works as an extensor. Otherwise, it works as a bending tip. When pressured air is
introduced into the clamper module, it inflates thus stretching the colon. When the resultant force
created at the area of contact further restrains enlargement of the clamper, the vacuum cups will be
pushed thus flattening it. In doing so, the air beneath the cups escapes, therefore creating a vacuum,
which in turn generates a positive adhesion. The extensor module will then be activated to either
axially extend or bend or both depending on the requirements.
Figure 1.20 Inchworm robot designed [KUMAR00]
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 48
Figure 1.21 The clamping mechanism of the micro-robot [KUMAR00]
In addition, a path-planning scheme integrating image and tactile sensor information for active
guidance and navigation of the micro-robot in the human colon have been proposed for the purpose of
observation, analysis and diagnosis. The proposed colonoscopy system was tested with physical
models and animal colons. The results of the tests were encouraging, but the author met the same
problems as the other researchers. Since the colon diameter changed at different sections, it made the
clamping to the wall difficult. Therefore, in the locomotion of the proposed device, the efficient
clamping of the colon wall still remains a challenge.
There are also other locomotion techniques inspired by other animal movements, such as
lizards and ants and octopi. Also, other methods some which are mechanical are studied for
locomotion purposes used during a robotic colonoscopy which can be found in Kassim’s survey
[KASSIM 03].
1.2.1.3 Autonomous capsules
In addition to the locomotion mechanism inspired by the animal movement as described
earlier, the idea of using natural peristalsis has been proposed and autonomous capsules have been
made to perform diagnosis and even therapy of the gastrointestinal tract. With the camera, light
source, transmitter and power supply integrated into a capsule, the patient can swallow and repel it
through natural peristalsis. In this case a pain free endoscopy is possible.
In 1997, [IDDAN 97] patented an idea describing a swallowable capsule, which includes a
miniature camera system, light source and power supply inside a capsule with a transparent front
portion. The capsule is mainly intended to inspect the small intestine. However in 2000, [GONG 00]
developed a capsulated wireless endoscope prototype, which incorporates a miniature charge-coupled
device camera and processor, a microwave transmitter and a halogen light source powered by small
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 49
batteries, as shown in Figure 1.22. High quality color television images have been transmitted using
this wireless endoscope in anaesthetized pigs.
Figure 1.22 Endoscopic capsule from Given Imaging [GIVEN]
An Israeli company Given Imaging [GIVEN] developed the first commercial disposable
capsulated pill named M2A which incorporates a light source, a miniature color video camera battery,
antenna and a radio transmitter figure. Images captured by the camera are transmitted by radio
frequency to an array of sensors worn around the patient’s waist where the signals are recorded
digitally. To use M2A, the patient simply needs to swallow the pill, put the sensor around their waist
and proceed with their daily affairs. After approximately eight hours or after detecting that the capsule
has been excreted, the patient removes the sensor and returns it to the clinic where the images are
downloaded and the doctor examines the video to look for abnormalities. The entire process is painless
and convenient for both the patient and the doctor. A step ahead in this direction has been performed
with another autonomous capsule: the NORIKA3 (RFSystem Lab, Japan), which is able to propel
through the gastrointestinal tract by exploiting the force generated by external electromagnetic fields
which can be tuned by a joystick [NORIKA3 Online]. The capsule incorporates a CCD camera and
some drug-delivery modules for localized therapy. This system doesn’t incorporate on-board
intelligence and is essentially a wireless teleoperated device rather than a reactive and adaptive
system.
1.2.2 Steerable distal end
Traversing a colonoscope from the rectum to the caecum of the colon is only part of the
journey toward automation of colonoscopy. It is important for the distal end of the automated
colonoscope to be able to bend or be steered towards a desired direction. During a traditional
colonoscopy, the medical doctors use the colonoscopic images not only to perform the diagnosis but
also to assist the introduction of the device into the colon and to control its advancement. On the basis
of the endoscopic images, doctors look for the colon lumen position and orient the steerable tip of the
colonoscope in order to follow the right direction. The tip is generally cable actuated and doctors can
drive it by using a knob on the colonoscope handle.
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 50
In order to replicate the traditional colonoscopic procedure, the design of autonomous
steerable distal tip is another important concern for the automation of colonoscopy.
[FUKUDA 94] proposed a shape memory alloy (SMA)-based bending devices with 2 degrees
of freedom which is called as microactive catheter (MAC). The basic structure of the MAC is shown
in Figure 1.23. The MAC is basically made of strips of SMA wires embedded at 120° intervals in a
cylindrical housing made of elastic material. When an electric current is introduced into one of the
SMA wires, it will be heated. In doing so, it will shorten in length, causing the entire MAC to bend
away from its central axis, as shown in figure 1.24. The angle of bend depends on the current carried
by the SMA wires. Thus, by individually controlling the flow of electricity into the three SMA wires,
the MAC can be made to bend in any desired direction at a specific angle. In order to increase the
bending angle, several MACs can be connected serially, and experiments have shown that a bending
angle can attain 80° with three MACs in series.
Figure 1.23 Bending principle of MAC [FUKUDA 94]
By using the same bending principle, [BAILLY 04a] developed a new active catheter for
endovascular aortic aneurysm treatment. The basic element of this catheter is constituted of three
metal bellows disposed 120° apart, providing three degrees of freedom. The bending angle of this
robot is obtained by individually controlling the water pressure in the chamber. With the connection of
several elements in cascade, the prototype of this catheter can obtain the bending angle of more than
90°.
In [MENCIASSI 02], silicone bellows are used to fabricate a bendable tip of the length of
30mm with the same bending mechanism as [FUKUDA 94]. It contains 3 small Shape Memory Alloy
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 51
(SMA) springs with a 120° layout. This configuration allows a 90° bending in three directions (Figure
1.24).
Figure 1.24 Steerable tip with LED illumination and CMOS camera [MENCIASSI 02]
As mentioned in the locomotion section, the extensor module of [ASARI 00, KUMAR00]’s
micro-robot for colonoscopy is comprised of three bellows. When the pressure in the three bellows is
equal, the extensor module works as an extensor. Otherwise, a bending angle can be obtained by
controlling the pressure individually.
Besides developing his robotic endoscope, [BURDICK 94] proposed in his patent an
alternative distal-end design. This design is a modification of one of his robotic endoscope segments
described earlier. The embodiment consists of four distinct inflatable sacs. These sacs, which are
comprised of an elastic material such as latex, are circumferentially located around a central core. This
core contains a high-pressure compressed line, a low-pressure or vacuum-gas return line, and a control
bus. Each sac is inflated or deflated by the action of valves. By controlling the relative pressure
distribution in the sacs, the segments can not only extend but also bend actively. However, the
growing incidence of Latex sensitivity in various populations will preclude the use of this material in
any device that comes in contact with a person.
[PEIRS 00, 01] designed a miniature manipulator for integration in a self-propelling
colonoscope. The propulsion unit is the same as the inch-worm robot designed in [DARIO 97]. The
manipulator is used to orient a camera and some tools and has two bending degrees of freedom
( ± 40°). It consists of two modules (figure. 1.25) driven by an electromagnetic motor with worm gear
reduction. Each module is 12.4mm in diameter and 20mm long.
Chapte
r 1 F
rom
the p
roble
m o
f colo
nosco
py to
the so
lutio
n o
f robotic co
lonosco
py
Gang CHEN
Thèse
INS
A d
e Ly
on, LA
I 2005
52
Figure 1.25 the structure and implem
entation of the miniature m
anipulator for colonoscopy [PEIRS 00]
Table 1.2 the summ
ary of various robotic colonoscopy system
Contact
with the
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Colonoscope specific features
Rapid and without human
intervention for the navigation
Quick reactivity, but limited
DOF
1 DOF, small size to integrate
other tools, weak bending
angle.
1 DOF, small size to integrate
other tools, weak rotation
angle. Can only take the lower GI
endoscopy
Self-propelled robot, very
flexible as a whole unit, but
3 DOF, small bending angle
3 DOF, small bending angle
and not flexible
Amplitude
55° in all
directions
15° / segment
(12 segments)
± 40° from one
rotation axe
From – 45° to
+60° from one
rotation axe
90° in all
directions
35° maximum
in 3 directions
50° maximum
in 3 directions
Movement
Bend and
stretch
Bend
Bend
Bend
Bend and
stretch
Bend and
stretch
Bend and
stretch
Bend and
stretch
Size
L : 50 mm
φ : 12 mm
L : 48 mm
φ : 15 mm
L : 40 mm
φ : 12.4
mm L : 21 mm
φ : 8.5 mm
φ : 13 mm
L : 30 mm
φ : 18 mm
L : 50 mm
φ : 15 mm
L : 25 mm
φ : 19 mm
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 53
Act
uato
r
Elec
trom
echa
nica
l
Elec
trom
echa
nica
l
Elec
trom
echa
nica
l
Elec
trom
echa
nica
l
SMA
SMA
Elec
trica
l
Pneu
mat
ic
( inc
hwor
m)
[BU
RD
ICK
94]
[PEI
RS
97]
[PEI
RS
00]
[PEI
RS
00]
[IK
UTA
88]
[MEN
C 0
2]
[PEI
RS
01]
[KU
MA
R 0
0]
1.2.3 Conclusions
We have introduced the state of the art of robotic solutions for automation colonoscopy:
locomotion and steering the distal end to the right direction of progression. Table 1.2 summarized the
characters of each robotic colonoscopy system. From the table, we can see that most of the robotic
colonoscopy systems used the inchworm-based locomotion mechanism [PEIRS 00 and 01, DARIO 99,
BURDICK 94 ]. But this movement needs to clamper the colon wall in order to get the advance power
in the colon. Since the colon is soft and flexible and it can move with the colonoscope, this problem is
a great challenge during a real colonoscopy. The first concern is the efficiency of advancement and the
other concern is the possible damage to the colon wall. A plausible solution for these problems is to
apply strong force so that the robot can clamper the colon firmly and can generate the reliable
advancement. However, such a solution will cause pain to the patient. Although [MENCIASSI 01,
KUMAR00] tried to improve the efficiency of clamping, the solution will need to be tested in more
experiments to know its reliability.
Another challenge for the conventional colonoscopy is the adjustment of the distal end to the
right direction for the progression. Also, many researchers [DARIO 99] [BURDICK94][PEIRS 00]
[KUMAR 00] have proposed several design schemes for the bending tip which are integrated into the
whole robotic colonoscopy system. [KUMAR 00] used a vision-based path-planning method to guide
the colonoscope. Thus the procedure can greatly reduce the possibility of contact with the colon wall.
Inspired by the problem of efficiency of navigation and some discussion with surgeons, we have
decided to focus our research on the design of a robotic manipulator which can automatically guide the
introduction of the colonoscope, and not on surgeons during the progression of the colonoscope. This
solution will completely avoid the disadvantage of the self-propelled robotic colonoscope and will
greatly reduce the workload of the surgeon.
Chapter 1 From the problem of colonoscopy to the solution of robotic colonoscopy
Gang CHEN Thèse INSA de Lyon, LAI 2005 54
1.3 Conclusions and our solution
This chapter touches the subject of this thesis from the problem of conventional colonoscopy
to its improvement by using a robotic solution. The first part deals with the problem of conventional
colonoscopy. The current situation of colon cancer in the world has been discussed, and then various
diagnostics and treatment methods are analyzed and compared. Following this, the conventional
colonoscopy has been described in detail as well as the instruments and the examination procedure.
After that, the drawbacks of the conventional colonoscopy have been presented from two aspects: the
complexity of the operation and the pain to the patient.
To facilitate the conventional colonoscopy procedure, a robotic colonoscopy solution has been
proposed in the second part. State of the art robotic colonoscopy systems have been summarized. For
the purpose of inspection and intervention in the colon, the robotic instruments have been studied from
two aspects:
• The autonomous locomotion aspect which makes the robot propel itself in the colon. Here, the
locomotion mode used most is the inch-worm movement which uses the clamper to cling to the
colon wall and then stretches itself by using the pneumatic bellows.
• The bending distal end of colonoscope is in full evolution. Shape Memory Alloy (SMA) actuator,
hydraulic actuators and electromechanical actuators are often presented to improve the bending
performance. The aim is, through adjusting the bending direction, to guide the progression of the
colonoscopy in the colon.
In this thesis, our goal, as described previously, is to design a new bending robotic
manipulator to direct the progression with minimal contact between the instrument and the colon wall.
The following chapters will focus on the state of the art continuum robot, which is a kind of robot
suitable for our application, and our design of a new automatic bending robotic manipulator which will
replace the conventional cable-based distal end by the surgeon.