Senior Science
Medical Technology – Bionics
SECTION 5
Non-invasive and
minimally invasive
medical techniques
SECTION 5
Non-invasive & minimally invasive medical techniques
9.3.5 The use of non-invasive or minimally invasive medical techniques has greatly
reduced risks to patients and has increased our understanding of how the
body works
9.3.5.a
Discuss the terms non-invasive and minimally invasive in relation to medical
techniques
9.3.5.b
Identify non-invasive diagnostic techniques including X-rays, ultrasound,
thermography and magnetic resonance imaging (MRI) and discuss their
importance in diagnostic medicine
9.3.5.c
Describe the advantages of using minimally invasive surgery techniques such
as key hole surgery
9.3.5.i
Identify data sources, gather, process, analyse and present information to
discuss the advantages and disadvantages of non-invasive and minimally
invasive medical techniques
© P Wilkinson 2002-04
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9.3.5.a
Discuss the terms non-invasive and minimally invasive in relation to medical
techniques
Non-invasive and invasive medical techniques
In “Western” medicine, doctors use their sense organs to diagnose illnesses. They look for
various indicators of poor health. Such indicators include: the colour of the skin and tongue,
the smell of a person’s breath, skin temperature, pulse rate and the position of painful areas
on the body. Most people understand that a high body temperature or a pale skin can be an
indicator of sickness. An important skill for a doctor is to interpret the health of the patient
using such indicators.
For thousands of years, diagnosis of disease relied on using external signs to determine the
health of the patient. The inside of the body was a mystery. It is believed that the inner
workings of the human body only began when some doctors began dissecting and studying
stolen corpses. This occurred during the 16th century.
Diagnosis using external signs is a non-invasive medical technique because there is no
penetration of the skin and no damage is done to tissue. Today, diagnosis is aided by a
host of tests and technologies. Medical laboratories can take tests of blood, urine and other
body fluids. In other situations, tissue samples might be taken and examined. All these
diagnostic aids give doctors vital information about the health of the patient with little
inconvenience to the patient. The procedures require no surgery and cause little or no pain.
A powerful tool used in modern diagnosis is the various imaging techniques. They provide
images (pictures) of internal parts of the body. Imaging technologies began with the use of Xrays to identify problems with bones. Today
 X-rays (CAT scans),
 Ultrasound techniques,
 Thermal imaging and
 Magnetic Resonance Imaging (MRI),
are all useful imaging techniques. These techniques are regarded as non-invasive. They
allow the doctor to look inside the patient, without cutting through the skin and without
damaging underlying tissue. Many of these technologies depend on computers to help
create accurate images of the internal workings of the body.
After a doctor makes a diagnosis, treatment can proceed. Treatment may include
prescription of medicine or surgery or a host of other methods. Surgery is branch of medicine
that is concerned with the treatment of injuries, diseases, and other disorders by manual and
instrumental means (operations). Many surgical techniques are highly invasive. They involve
the use of anaesthesia to deaden the pain or even “put the patient to sleep” as well as large
cuts into the person’s body. Skin, tissue, nerves and blood vessels are all damaged
during invasive surgery. Such surgery involves major trauma for the patient, with long
hospital stays and significant risk of wound infection.
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Modern technology has resulted in the development of minimally invasive surgery. In this
case the incisions into the body are very small and involve minimal trauma to the patient - a
typical example is keyhole surgery.
Questions
1. a. Identify two ‘external signs’ that indicate poor health.
b. Explain why one of these external signs is non-invasive.
2. Why would a doctor order a blood or urine test?
3. What is the purpose of imaging technology?
4. Name two ‘imaging’ techniques.
5. Explain why MRI is a non-invasive technique.
6. Define surgery.
7. What happens to a patient during an invasive medical procedure?
8. Consider the following list of medical techniques or procedures
i.
ii.
iii.
iv.
v.
vi.
vii.
Taking a person’s rectal temperature
Taking a blood sample (using a syringe)
Viewing a foetus using ultrasound
Checking a person’s heart rate using a stethoscope.
Using a laser to correct eyesight
Extracting a tooth
Angioplasty
a. Put them in order beginning with least invasive to most invasive.
b. Suggest which of these techniques are non-invasive and which are minimally invasive.
 Put the information into a table (similar to the one shown below).
Non-invasive
Minimally invasive
 Justify your decision to classify particular techniques.
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9.3.5.c
Describe the advantages of using minimally invasive surgery techniques such
as key hole surgery
Minimal Invasive Surgery
Traditional open surgical techniques are being replaced by new technology in which a small
incision is made. This surgery has been termed key-hole surgery because entry into the body
occurs through a very small (key) hole.
The procedure involves inserting an instrument called an endoscope into the body. These
are small tubes containing a series of lenses and optic fibre bundles. They are fitted with a
light source and small video cameras and range in size from about 2 – 5 millimetres in
diameter. This allows doctors to see internal tissues and organs on a TV monitor. Additional
tiny cuts can be made if surgical instruments such as forceps and scissors are needed in the
procedure.
Diagram of an endoscope
Key hole surgery is a minimally invasive surgical procedure because it requires a much
smaller incision than traditional surgery does. This causes less damage to nerves, muscles,
and skin. As a consequence the benefits include less pain, scarring and recovery time for the
patient (fewer days in hospital), as well as reduced health-care costs. It can be performed
using only local anaesthesia and a mild sedative.
The technique now has many uses. It is used for diagnosis and in a variety of surgeries,
including the repair of cartilage damage to knees, the removal of the gall bladder and in
appendectomy, hysterectomy, repair of hernias, and removal of cancerous tumours.
Questions
9. Describe an endoscope.
10. What is the difference between key hole surgery and traditional surgery?
11. Why would key hole surgery be referred to as a minimally invasive technique?
12. Name three advantages (benefits) of key hole surgery (for the patient).
13. Name five uses of key hole technique.
© P Wilkinson 2002-04
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9.3.5.b
Identify non-invasive diagnostic techniques including X-rays, ultrasound,
thermography and magnetic resonance imaging (MRI) and discuss their
importance in diagnostic medicine
Diagnosis
Health care consists of three main steps:
 Diagnosis
 Treatment and
 Prevention
Diagnosis is the examination of a person to identify the injury or disease. The correct
diagnosis is important for the correct treatment of the injury or disease. A doctor makes a
diagnosis by using a person’s case history, by physical examination and by medical tests.
The case history involves the patient responding to questions about present and past
illnesses, family history of disease, and habits. The physical examination involves such
things as measurement of height and weight, taking blood pressure, listening to the heart and
lungs with a stethoscope. Examining eyes, ears, and mouth, testing hearing and vision may
also be performed in routine physical examinations. Body fluids (blood, urine and spinal
fluids) all reveal important information about disease.
Today, there is an enormous array of medical tests.
techniques that are important in diagnostic medicine.
These include a host of imaging
Questions
14. What is a medical diagnosis?
15. Describe how does a doctor make a diagnosis?
X-Rays
X-rays are high-energy electromagnetic waves with a short wavelength. They have many
similarities to visible light. Light has a lower energy. Because X-rays have high energy they
can penetrate deeply into many substances that do not transmit light. This penetrating power
of X-rays makes them extremely useful in medicine and industry. Pictures of internal parts of
the body are possible because the X-ray radiation passes through the body. The rays are
absorbed more by dense tissue, like bones. The pictures produced are lighter or darker
depending on the type of tissue the rays pass through.
Advantages
In medicine, X-rays are important because they provide pictures of
bones and internal organs of the body. X-rays help doctors detect problems such as
broken bones and lung disease. Dentists use X-ray pictures to reveal cavities. Today X-rays
are the most widely used images in medical diagnosis. This is because they are cheap
and the machines are widely available.
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Disadvantages
Some limitations of using X-ray imaging are that the picture is only twodimensional. Although at times the image is difficult to interpret, many X-ray images show
easily identified problems. Also, they cannot show structures deep within a tissue. X-rays
actually pass through the body. Possibly, the biggest problem with X-rays is that they can
damage, or even destroy, healthy tissue. This makes them very dangerous. Over exposure
to X-rays can cause cancer and skin burns. The amount of exposure to X-rays needs to be
limited.
Activity 1
Obtain several X-rays
a. Observe the images and
b. Describe what can be seen.
Questions
16. What is an X-ray?
17. Why can X-rays be used to obtain pictures of internal parts of the body?
18. What sorts of tissue or problems can be ‘viewed’ by X-rays?
19. Explain why X-rays are important in diagnostic medicine.
20. Explain why X-rays are widely used for diagnosis.
21. What is the biggest problem with the use of X-rays in examining a patient?
22. An X-ray can give a doctor a clearer view of a broken arm. To obtain such a picture, X-ray
radiation passes through a person’s arm. Complete the two sentences below
 An X-ray is a non-invasive technique because ………….
 An X-ray is a minimally invasive technique because …………..
23. Identify two limitations of using X-rays for diagnosis.
24. Explain why it is relatively easy it is to interpret an X-ray
X-rays and CAT scans
The use of computers has greatly improved imaging technologies. These new technologies
can now produce cross-sectional images. Unfortunately, compared to traditional X-ray
images CAT scan technology is quite expensive. They also require more skill and
training to interpret the images.
A CAT (computerized axial tomography) scan uses X-rays to produce an image. A thin ray of
X-rays is passed through the body at various positions. The rays that pass through the body
are measured and the information is sent to a computer. The computer analyses the data
and cross sectional images are produced. The images produced are much clearer than
normal X-ray films. A series of CAT scan images allows the changes in organs as they work,
to be viewed (for example the flow of blood through blood vessels can be viewed).
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Activity 2
Observe some pictures made from CAT scans.
Describe the difference between a cross-section image of a CAT scan and the image
produced by an X-ray.
Questions
25. Outline some advantages of a CAT scan compared to a traditional X-ray?
26. Outline some disadvantages of a CAT scan compared to a traditional X-ray?
Ultrasound
Ultrasound is sound with frequencies in a range too high for humans to hear. This is
generally regarded above a frequency of 20,000Hz (gycles per second – Hertz). Scientists
have developed a diagnostic and therapeutic technique using ultrasound.
Ultrasound devices work because ultrasound is easily reflected. The ultrasound device is
used to transmit sound and receive echoes. A jelly-like substance is smeared on the skin in
order to improve the acoustics. In the body various tissues reflect the sound. A computer
processes the resulting pattern of sound reflection. A moving image can be produced on a
screen or on photographic film.
Diagnostic Applications Air, bone, and other calcified tissues, absorb nearly all the
ultrasound beam, so this technique is of no use in determining conditions of the bones or
lungs. However, as fluid conducts the ultrasound well, it is a useful technique for examining
structures that are fluid filled.
Ultrasound can be used to examine the arteries, the heart, the pancreas, the urinary tract, the
ovaries, the veins, the brain; and the spinal cord. When ultrasound is used to examine the
heart, it is known as an echocardiography. Echocardiography is used to study heart disease,
coronary artery disease, tumours of the heart, and other heart disorders.
Use of Ultrasound in Pregnancy
The best-known application of ultrasound is the
examination of the foetus during pregnancy. Unlike X-rays, ultrasound is completely safe
during pregnancy, with no risk to either mother or baby. It is also non-invasive, accurate and
a cost-effective investigation of the foetus. It is used to monitor the growth, development, and
well being of the foetus, and can be used to check the due date. The size of the foetus’ head
can be measured to estimate its age. It can be used to detect foetal abnormalities such as
spina bifida, or severe congenital heart disease; where in each case early diagnosis allows
treatment to be given during the rest of pregnancy and at birth.
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Questions
27. What is an ultrasound?
28. Explain how ultrasound imaging works.
29. Name a tissue that cannot be examined by ultrasound.
30. Name three internal structures that can be examined by ultrasound.
31. Name three advantages of using ultrasound as a diagnostic technique.
32. What type of radiation passes through the body during an examination by ultrasound?
33. Explain why ultrasound is a non-invasive technique (refer back to previous information).
MAGNETIC RESONANCE IMAGING (MRI)
One of the newest, most expensive, yet most powerful types of imaging is MRI (Magnetic
Resonance Imaging).
The Basic Idea
A MRI machine uses the water in the body, a powerful magnetic field and
bursts of radio waves to create an image. The machine itself looks like a tunnel passing
through a large cube. The cube in a typical system might be 2 metres tall by 2 metres wide
by 3 metres long (although new models are rapidly shrinking). The patient goes into the
tunnel head or feet first, depending on the examination needed.
The MRI scanner can pick out a very small point inside the patient’s body and ask it,
essentially, “what type of tissue are you?” The point might be a cube that is half a millimetre
on each side. The MRI system goes through the patient’s body point by point, building up a
2-D or 3-D map of tissue types. A powerful computer then joins all of this information to
create 2-D images of 3-D models. MRI provides images of extraordinary detail compared to
any other imaging process.
Advantages and Disadvantages
Why would a doctor order a MRI? Because the only
way to see inside your body any better is to cut you open. MRI is ideal for:

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Visualizing blood flow in virtually any part of the body. This allows images of the arterial
system in the body, but not the tissue around it.
Diagnosing MS (multiple sclerosis)
Diagnosing tumours of the pituitary gland and brain
Diagnosing infections in the brain, spine or joints
Visualizing torn ligaments in the wrist, knee and ankle
Diagnosing tendonitis
Evaluating masses in the soft tissues of the body
Evaluating bone tumours, cysts and bulging or herniated discs in the spine
Diagnosing strokes in their earliest stages
These are but a few of the many reasons to perform a MRI scan.
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MRI systems do not use ionising radiation (X-rays) that can damage living tissue. Also MRI
contrast materials have a very low incidence of side effects. Another major advantage for
MRI is its ability to image in any plane. CAT is limited to one plane, the axial plane (ie using a
loaf of bread analogy, the axial plane would be how a loaf of bread is normally sliced). A MRI
system can create axial images as well as images in the sagittal plane (slicing bread side to
side lengthwise) and coronally (think of the layers of a layer cake) or any degree in between,
without the patient ever moving. If you have ever had an X-ray, you know that every time
they take a different picture, you have to move.
MRI does have drawbacks, however. For example:

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There are many people who cannot safely be scanned with MRI (for example, because
they have pacemakers).
Orthopaedic hardware (screws, plates, artificial joints, etc…) in the area of a scan can
cause distortions on the images.
MRI scans require patients to hold very still for extended periods of time. MRI exams can
range in length from 20 minutes to 90 minutes or more. Even very slight movement of the
part we are scanning can cause very distorted images that will have to be repeated.
There are many claustrophobic patients in the world, and being in a MRI machine can be
a very disconcerting experience for them.
The machine makes a tremendous amount of noise during a scan. The noise sounds like
a continual, rapid hammering. Patients are given earplugs or stereo headphones to muffle
the noise (in most MRI centers you can even bring your own cassette or CD to listen to).
MRI systems are very, very expensive to purchase and therefore the exams are also very
expensive.
Interpretation of MRI images requires specialised training.
The almost limitless benefits of MRI for most patients far outweigh the few drawbacks.
Questions
34. What type of radiation passes through the body during an MRI examination?
35. What technology is needed to process data collected by an MRI scanner?
36. Describe how an MRI scan works.
37. Research What is a tumour?
38. Name three uses of an MRI scan, in diagnostic medicine.
39. Explain why MRI scans have significant advantages over other imaging systems.
40. Explain why an MRI scan is a non-invasive technique.
41. Name two significant disadvantages of MRI scanning technology.
© P Wilkinson 2002-04
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9.3.5.i
Identify data sources, gather, process, analyse and present information to
discuss the advantages and disadvantages of non-invasive and minimally
invasive medical techniques
Research Assignment
Thermography
Thermology is the study of heat. Thermography is a technique that uses differences in body
temperature to create images. It is one example of a non-invasive medical technique used
today. Thermography uses infra-red radiation to see inside the body. Infra red cameras are
used to detect the heat emissions from a subject. Computers are then used to analyse the
data collected to create colour images of the area being examined.
Blood flow and the amount of metabolic activity affect body temperature. The technique is
useful to detect cancerous tumours because these tumours are metabolically very active. It
can also be used to locate areas of increased or decreased blood flow.
What to do Part A
Diagnosis by thermography
1. Access one of the following web sites
2. Complete the task for that web site
 Breast cancer can be diagnosed by thermography. Use the following web site and
describe how thermography is used to diagnose breast cancer.
http://home.earthlink.net/~docbill/athand.htm
 Research is being constantly done in the area of thermography and its uses. Use the
following web site and describe 3 recent discoveries or techniques that use
thermography.
http://www.thermology.com/research.htm
What to do Part B
Identifying sources of information
Information about non-invasive and minimally invasive medical techniques can be found from
a number of sources.
Evaluate the quantity and quality of information that could be obtained on this topic from each
of the following areas.
 The school library.
 Encyclopaedias – World Book, Britannica
 The local Public Library
 Electronic sources – Encarta, etc
 The Internet.
Criteria to make a judgment includes quantity of information, readability (difficulty level,
detail), reliability of source, how up to date is the information and others.
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Summative Questions
42. Discuss the terms non-invasive and minimally invasive in relation to medical techniques.
43. Describe the advantages of using minimally invasive surgery techniques such
as key hole surgery
44. Discuss the importance in diagnostic medicine of non-invasive diagnostic techniques
including X-rays, ultrasound, thermography and magnetic resonance imaging (MRI).
45. Discuss the advantages and disadvantages of minimally invasive medical techniques
Note the following
Discuss questions require an extended answer.
The question itself provides no structure for the answer.
The steps below show one way of developing a structured answer (for question 43). This
structure could be used to for any discuss question.
Step 1
Underline important words in the question
non-invasive, minimally invasive, medical techniques.
Step 2
Circle the KEY verb in the question and recall its meaning.
Discuss – identify issues and provide points for/or against
Step 3
Make a list of issues that could be used to answer the question.
The question is asking you to consider what the two terms mean. Therefore,
the issues relate to factors to consider in deciding if a technique is non-invasive
or minimally invasive. Finally a definition or description of each type of
technique is needed (with examples).
Use the scaffold below to answer the question
Issue 1
For Issue 2
Penetrate the skin
Against
Amount of trauma, effect on normal functioning of the body
Write appropriate definitions or descriptions
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