Chapter1 From the problem of colonoscopy to the solution of...

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


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


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


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:


• 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.


• 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


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.

Gang CHEN

Thèse

INS

A d

e Ly

on, LA

I 2005

32

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


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 ]



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



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.



Figure 1.8 Terminology and the characteristics of OLYMPUS colonoscope



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]



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.



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



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.



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



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



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



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



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



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]



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]



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



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.



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



(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



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.



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.

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