Teachers’ Notes
Electromagnetic spectrum ................................................. 2
Radiowaves ................................................................. 2
Infrared......................................................................... 3
Thermography .............................................................. 4
Visible light ................................................................... 5
X-rays........................................................................... 8
Radiotherapy ................................................................ 9
Radioactivity ...................................................................... 11
Nuclear Medicine ......................................................... 13
PET .............................................................................. 16
Radiotherapy ................................................................ 17
Ultrasound ......................................................................... 18
Doppler Ultrasound ...................................................... 20
Worksheets
Electromagnetic spectrum ................................................. 22
Infrared .............................................................................. 23
X-Rays .............................................................................. 24
Nuclear Medicine............................................................... 25
PET ................................................................................... 26
Ultrasound ......................................................................... 27
Answers....................................................................... 29
Acknowledgements .............................................. 32
www.teachingmedicalphysics.org.uk
1
Electromagnetic spectrum
National Curriculum requirements (KS4, Sc4 Physical Processes)
Students should be taught:





That waves transfer energy without transferring matter (3d)
that the electromagnetic spectrum includes radio waves, microwaves,
infrared, visible light, ultraviolet waves, X-rays and gamma rays (3e)
some ways in which microwaves, infrared and ultraviolet waves are used
and the potential dangers of these (3f)
some uses of X-rays and gamma rays in medicine (3g)
how information can be transmitted along optical fibres (3h)
Radio waves
What happens when you use your
mobile phone?
These images show the effect of
using a mobile phone on head
temperature.
An image of the head has been
scanned into a computer. A computer
program then worked out where the
microwaves emitted by the mobile
phone go, and the amount they heat
the head by.
The maximum heating in this case
was 0.2oC. The left hand image
shows the surface of the head and
the right hand image is a slice
showing how the temperature
changes deeper into the head.
Q: Do you think this is dangerous?
A: 0.2oC is about the same change as
normal physiological changes, so is
probably not significant but is of the
same order of magnitude. The
Government recommends minimum
mobile phone use, especially for
children.
www.teachingmedicalphysics.org.uk
2
Infrared
Pulse oximetry
A pulse oximeter showing the heart rate
(81 beats per min) and oxygenation of
the finger (99%). It uses red and near
infrared light to determine the amount of
blood and its colour. Blood absorbs light
strongly so an increase in the amount of
blood means that less light is measured.
Blood carrying oxygen is also a brighter
red than blood carrying deoxygenated
blood. This means that we can measure
both the amount of blood and the
amount of oxygen it is carrying.
Near Infrared Spectroscopy (NIRS)
Like pulse oximetry, near infrared
spectroscopy (NIRS) uses near infrared
light to determine the amount of blood
and its colour.
When the child observes a visual
stimulus (alternating checkerboard
pattern), the parts of the brain which
respond to vision increase their electrical
activity. This increased activity requires
energy, so blood supply to the region
increases. Blood is a strong absorber of
near infrared light and so, by measuring
the transmission of near infrared light
across the head, we can get a
measurement of blood volume and
therefore brain activity. The black hat
prevents light from the room being
detected.
The second picture shows NIRS being
used on an adult volunteer.
The third picture shows the measured
blood flow response to flashing lights.
The lights flash for 18 s. For the first 5 s,
nothing happens, then there is a big
increase in oxygenated blood and a
smaller decrease in deoxygenated
blood, so overall a small increase in
blood volume. Even though the brain is
using oxygen up, the body responds by
sending more blood than is necessary,
so the additional oxygenated blood
exceeds the brain's requirements and
the overall effect is an increase in
oxygenated blood.
www.teachingmedicalphysics.org.uk
3
Thermography
Thermograms are surface maps of temperature, created by measuring emitted infrared
radiation.
Hands
This picture shows a thermal picture of
the temperature of the hand. On the left
is a normal patient, where each finger is
warm and has a similar temperature.
The patient on the right has Raynaud's
syndrome, which is a problem with the
circulation in the fingers and toes.
Reduced blood flow to fingers means he
or she has some fingers which are much
colder than the others.
Face
This shows a thermogram of a child’s
face. The lips, nose and eyes are
warmer, and the head where it is
insulated by hair is cooler and so is
emitting less infrared radiation.
Back
This shows a thermogram overlaid onto
a normal photograph taken with visible
light. The triangles are used to align the
two images (though above the right
shoulder you can see a slight
mismatch). This person is healthy.
www.teachingmedicalphysics.org.uk
4
Visible Light
Endoscopy
Endoscopy is a minimally invasive
diagnostic medical procedure used to
see inside the body by inserting a small
scope through a natural body opening. It
is often cited as a use of optical fibres,
though modern endoscopes tend to use
cameras to take the images.
The left hand picture shows an
endoscope.
The right hand picture shows an x-ray
image of an endoscope passing down
the oesophagus, into the stomach (far
right), then round into the small intestine.
The left hand picture is taken in the
stomach, with the endoscope bending
round so you can see part of it coming
out of the oesophagus. It shows the wall
of the stomach lapsing back into the
oesophagus, which is called a hernia.
The right hand picture is again in the
stomach and shows a parasitic worm. If
treated with the right drugs, the worm
will detach from the stomach wall, pass
through the digestive system and leave
the body in faeces.
www.teachingmedicalphysics.org.uk
5
Scanning laser ophthalmoscope
This uses blue laser light to image the back
of the eye (the retina). The mirrors scan the
light across the retina allowing an image to
be built up.
www.teachingmedicalphysics.org.uk
6
This image shows the optic disc (where
the optic nerve leaves the eye) and has
a large number of blood vessels
supplying it.
To the left of the image is the macula,
the region of the eye with the most
cones and with the fovea at the centre.
Photodynamic therapy (PDT)
PDT can be used to treat Bowen’s
disease (a kind of skin cancer). A cream
called Metvix is rubbed onto the skin and
it is preferentially absorbed by cancer
cells, so the drug collects in the tumour.
When the skin is then illuminated with
visible light, the drug breaks down and
destroys cells. The process is therefore
doubly selective – first the drug collects
in the tumour and second, only the
tumour is illuminated. The pictures show
the skin before and after treatment.
Blue light treatment of jaundice in
babies
Premature babies sometimes have
jaundice. This makes them look yellow
and is due to excess bilirubin, the yellow
pigment in bruises. It is usually harmless
but can be treated using blue light. The
blue light breaks down the bilirubin so
that it can be excreted in urine.
www.teachingmedicalphysics.org.uk
7
X-Rays
This is the first clinical x-ray taken by
Wilhelm Roentgen on 22 Dec 1895. It
shows his wife’s hand, with her wedding
ring and the bones of her fingers clearly
visible. She had been worried about the
long hours he was spending in the lab,
so Roentgen took this image to show
her what he had been doing!
It was taken with a 15 minute exposure;
a modern x-ray image has an expose of
about10 ms
Click, and the picture fades into a modern x-ray
CT (computed tomography) takes
images that are slices through the body.
They can be reconstructed to make a 3D
image of the body.
This is a CT image which has been
processed by computer so that only the
bones and the muscles are shown. The
second metatarsal bone (the bone that
David Beckham broke in 2002) is
shown.
www.gehealthcare.com
Similarly, this CT image of the pelvis
which has been processed so that only
the bones are shown.
www.gehealthcare.com
www.teachingmedicalphysics.org.uk
8
Radiotherapy
Radiotherapy is the treatment of cancers using high energy radiation (x and gamma
rays).
Ionising radiation damages cells, and high enough doses can kill them. The cells in
cancerous tissue are dividing very rapidly, making them more susceptible to damage
by radiation. Healthy cells are also able to regenerate if they are only slightly damaged,
cancerous cells cannot. Even so, care has to be taken to ensure that only the
malignant cancer cells, and not the surrounding healthy tissue, receive a high dose.
This is a picture of a linear accelerator
(linac).
A linac generates high energy x-rays. It
rotates around the body, with the tumour
at the centre of rotation, irradiating the
tumour from different directions. This
means the tumour receives a large
dose, but the dose to healthy tissue is
minimal.
Demonstration: the linac moves around
the ring irradiating the tumour from
different directions.
Q: Which part of the body has
received the higher dose?
A: The tumour
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9
Treatment planning
X-ray CT or MRI (magnetic resonance imaging) images are used to plan the
radiotherapy treatment.
Isodose curves (lines joining the points
in the tissue that will receive the same
dose of radiation) are overlaid on this
x-ray CT scan of the chest.
Q: Can you also point to ….
the spine
the ribs?
A medical physicist analyses the images
and works out how to target the linac so
that the tumour receives the maximum
dose but other tissues receive a small
dose. Particularly sensitive organs such
as the spine and gut should receive as
small a dose as possible.
Computers help the physicists to
calculate the dose. This picture shows
the beam coming from 5 linac positions
to treat a tumour in the chest
www.teachingmedicalphysics.org.uk
10
Radioactivity
National Curriculum requirements (KS4, Physical Processes)
Students should be taught:






that radioactivity arises from the breakdown of an unstable nucleus (6a)
about some sources of the ionising radiation found in all environments (6b)
the characteristics of alpha and beta particles and of gamma radiation (6c)
the meaning of the term ‘half-life’(6d)
the beneficial and harmful effects of ionising radiation on matter and living
organisms (6e)
some uses of radioactivity, including radioactive dating of rocks. (6f)
What is radioactivity?
Table of properties of different types of radiation (not in the presentation)
name
Alpha (α)
Beta (β)
Gamma (γ)
What is it?
An electron
mass
A helium nucleus (2 protons and 2
neutrons)
Heavy
Light
Electromagnetic
wave
Zero
charge
+4
-1
None
penetration
Poor
Quite good
Highly penetrating
Alpha particles can be stopped by a few centimetres of air, or a
piece of paper.
Beta particles need a few millimetre of aluminium to stop them.
Gamma rays can only be stopped completely by several
centimetres of lead.
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11
Uranite
Uranite ore contains uranium, a
radioactive element. It looks the same
as a non-radioactive rock.
Radiation can be detected by a Geiger counter. These click every time either an alpha
or beta particle, or a gamma ray, is detected.
www.teachingmedicalphysics.org.uk
12
Nuclear medicine
Nuclear medicine uses radioisotopes to
investigate the function of the body. It
works by following what happens to
certain chemicals so the doctor can see
if an organ is doing its job properly. The
chemicals, called tracers, are 'labelled'
with a radioactive isotope and their path
followed through the body.
The radioisotopes are produced in
generators where isotopes with long
half-lives (e.g. molybdenum-99, half-life
67 hours) decay to isotopes with shorter
lives (e.g. Technetium-99m, half life
6 hours).
The Technetium-99m is drawn out of the
generator in a solution and can be made
into a range of different drugs
(radiopharmaceuticals) that are
absorbed by different parts of the body.
In the image you can see the lead glass
used to shield the face of the medical
physicist.
Q: What material is this?
A: Lead.
Q: Why?
A: Because lead can absorb all types of
radiation, even gamma rays.
www.teachingmedicalphysics.org.uk
13
The radiopharmaceutical is drawn up
into a syringe shielded with lead and its
dose checked before it is injected into
the patient.
The gamma rays given off by the
radioisotope are detected by a gammacamera (a detector that takes images
with gamma rays) which is connected to
a computer and gives an image of the
distribution of the isotope in the patient.
The image shows where the drug is
absorbed, and if several pictures are
taken over a period of time it can also
show how quickly the isotope is
absorbed.
This is a bone scan made using
technetium-99m.
Q: Can you see where the patient was injected?
A: By the elbow joint in the patient’s left arm.
You can tell this as some of the radioactive technetium-99m has remained there.
www.teachingmedicalphysics.org.uk
14
The images show the build up of the
tracer in the kidneys over time. The left
kidney is healthy, but there is a blockage
stopping the isotope from reaching the
right kidney. In the PowerPoint
presentation these images fade in after
each other with only one mouse click.
Ventilation/perfusion scan. This involves
two tests which may be done together or
separately. The patient is injected with a
radioactive drug which remains in the
bloodstream around the lungs. An image
of the distribution of this drug (on the
right) shows the blood perfusion in the
lungs. This should be uniform. A light
area may show a blockage where the
blood is not adequately perfusing the
lung.
The second test is a ventilation scan,
where the patient breathes radioactive
xenon or krypton gas. This shows those
parts of the lungs which are adequately
ventilated.
Combining both scans allows a doctor to
work out whether the lung is functioning
properly, and allows operations to be
designed so as to reduce long-term
damage.
Computer software enables us to look at
the kidney from all directions. This
image of a kidney rotates in the
PowerPoint presentation.
www.teachingmedicalphysics.org.uk
15
PET
Positron Emission Tomography (PET) scanning uses beta+ emitting isotopes.
The isotope decays emitting a positron (which is a positive electron, also called a beta+
particle, and is a particle of antimatter). The positron can only travel about 1 mm before
losing its energy and slowing down. When it slows down enough, it will meet a negative
electron from a nearby atom, and they will 'annihilate', leaving no particles. Their
energy is converted into two gamma rays which travel in opposite directions so that
momentum is conserved.
This is used to make the radionuclides
used in PET imaging by bombarding
atoms with accelerated protons. It must
be near to the PET scanner as the
radionuclides used only have a short
half-life (e.g. 2 mins for Oxygen-15).
The information from the PET scan (in
colour on slide) can be superimposed on
an x-ray CT image (grey/blue on slide).
In this way, doctors get the benefit of
high contrast from the PET scan and
good spatial resolution from the CT
image.
www.teachingmedicalphysics.org.uk
16
Radiotherapy
For more information see radiotherapy in the electromagnetic spectrum section (pg 9-10).
Modern radiotherapy units use linear
accelerators (linacs for short). These
produce very high energy x-ray beams.
The head rotates around the patient with
the centre of the circle in the centre of
the area to be treated. Older units
worked in a similar way but used a
single cobalt-60 source which emitted
gamma rays. A more modern approach
to radiotherapy using cobalt-60 is with a
Gamma Knife.
Gamma knife
The gamma knife is used for brain
surgery, but is non-invasive (it is
performed without cutting the skin or
muscles and the skull does not need to
be opened), though a frame needs to be
attached to the skull using 4 screws
(fitted under local anaesthetic).
The gamma knife has 201 cobalt-60
sources, which emit gamma rays and
have a half-life of 5.26 years. The
sources are positioned in a hemisphere
inside the unit. The patients head, held
in the frame, is held inside a helmet with
201 holes to precisely target the
radiation. When treatment starts, the
patients head is moved inside the unit.
The treatment is planned using CT or
MRI images, so that the sources are
correctly targeted to irradiate the tumour
and avoid healthy tissue, especially
around the eye and cochlea.
The gamma knife is used to treat benign
and malignant tumours, blood vessel
malformations, pain, and some
movement and psychiatric disorders.
There are currently three in the UK (two
in London and one in Sheffield).
www.teachingmedicalphysics.org.uk
17
Ultrasound
National Curriculum requirements (KS4, Sc4 Physical Processes)
Students should be taught:

about sound and ultrasound waves, and some medical and other uses of
ultrasound (3l)
How does it work?
The probe is coupled to the skin to
make a good connection using a
special coupling gel.
The probe emits an ultrasound pulse.
When the ultrasound wave reaches a
boundary (such as the edge of an
organ), some of it is reflected and some
of it continues.
The same thing happens at every
boundary.
Many elements can be joined together
to make a probe which can create an
image.
www.teachingmedicalphysics.org.uk
18
www.gehealthcare.com
The left hand slide shows a typical ultrasound scanner and the slide on the right a
foetus at 8 weeks, 18 weeks and 24 weeks old.
Surface Rendering
The image on the left is a 2D ultrasound
scan through the foot of a foetus. The
image on the right has been processed
by computer to find the outline of the
foot. This is surface rendering.
www.gehealthcare.com
4D ultrasound can be used to image movement such as the heart beating (imaging the
heart) or kissing. These two ultrasound images show the muscles used for kissing and
speaking, which provides useful information for facial reconstruction surgery.
www.teachingmedicalphysics.org.uk
19
Doppler Ultrasound
The ultrasound probe emits an ultrasound
wave. It travels through tissue and echoes
off boundaries, as with standard
ultrasound. In most cases, the echo has
the same frequency as the emitted wave
but if the target is moving, as in the case of
a blood cell, the wavelength of the
reflected wave will be modified by the
Doppler effect.
It is interesting to realise that there are two
Doppler shifts occurring. The first occurs
between the transmitted wave and the
blood cell (with the probe acting as a
source). But then, the beam echoes off the
blood cell, so the moving blood cell
behaves as a source and there is a second
Doppler shift of the echoed wave, between
the blood cell and the detector. Hence, the
Doppler shifted frequency is twice what
you would initially expect.
In this image, the Doppler ultrasound
probe is measuring the blood flow in the
radial artery, the same one you measure
your pulse from.
Doppler imaging can be combined with
normal ultrasound imaging which can be
used to image blood flow. Colour can be
added to the image to make it easier to
see.
Click on the loudspeaker icon to hear the sound.
Q: Can you work out the heart rate?
www.teachingmedicalphysics.org.uk
20
Both the image and the Doppler data of
the healthy carotid artery are clean and
smooth as the smooth walled vessels
lead to laminar flow.
The partially blocked carotid artery
causes turbulent flow, as seen from the
red and blue regions in the Doppler
image (blood flow towards and away
from the probe).
www.gehealthcare.com
This is a complicated image of the heart
of a foetus. It shows the blood moving
between the ventricles and the arteries.
In the PowerPoint presentation you can
see the motion of the heart as it beats.
Safety
Ultrasound imaging has been used for
50 years, and is thought to be safe,
though some energy is absorbed by the
tissue, causing heating. This is very
small in 2D ultrasound, and though new
4D imaging uses more energy it is
thought to be safe.
Q: Should we use it to diagnose foetal illness?
A: Yes, the benefit of being able to diagnose and treat the foetus is greater than the
risk of causing it harm.
Q: Should we use it to make videos of healthy babies for parents?
A: Some people say that because there is no medical benefit to the baby, the risk
outweighs the benefit. Others say that these scans help the parents to bond with
the baby, so there is a benefit. What do you think?
[END OF PRESENTATIONS]
www.teachingmedicalphysics.org.uk
21
The Electromagnetic Spectrum
1) Name the parts of the Electromagnetic Spectrum
Low Energy
___________
High Energy
_______
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _-_ _ _ / _ _ _ _ _
2) Write a) what part of the body the image shows, b) the part of the
electromagnetic spectrum used and c) the name of the method used
to take each image.
a)……………………
b)…………………...
c)……………………
…………………….
…………………….
…………………….
………………………
……………………….
……………………….
3) Match the Medical Physics job with the part of the Electromagnetic
spectrum used (each word can be used more than once or not at all)
Imaging a fracture in a bone
Gamma rays (γ)
Thermography
X-rays
Treating cancer
Infra Red (IR)
CT scans
Visible
Endoscopy
Ultraviolet (UV)
Photodynamic therapy
Bone scan
www.teachingmedicalphysics.org.uk
22
Infrared Radiation
1) a. Colour in your key.
b. Colour in outside the face where it is coldest.
c. Colour in the rest of the picture, working out which parts of your
face give out the least and most infrared radiation.
34oC
32oC
30oC
2) Look at the images of the hands below
One person has healthy hands; the other person has a poor blood
supply to their fingers (Raynaud's syndrome)
a. Label one picture HEALTHY and POOR BLOOD SUPPLY
……………………………….
……………………………
b. On each hand in the left hand image, label a blood vessel
c. What are the names of the three types of blood vessel?
…………………., ……………………., ………………………
www.teachingmedicalphysics.org.uk
23
X-Rays
1) a) What differences can you see between
the two x-ray images?
…………………………………………………
……….…………………………………………
………………….………………………………
…………………………….……………………
…………………………………………………
…………………………………………………
…………………………………………………
b) What year was x-ray 1 taken in? circle your answer
1795
1895
1995
c) Label a knuckle in each image
d) What is the feature marked in the left image?
2) Radiotherapy- fill in the gaps in the paragraph below using the words in
the box
healthy
dose
cancerous
dividing
tumour
kill
DNA
X-rays
irradiating
X-rays and other radiation can damage the _ _ _ in
cells and kill them. Cells which are ________ rapidly
are more likely to be killed, so we use x-rays to ____
the rapidly-dividing ______ cells. We must make sure
that _______ tissue is undamaged. A linear
accelerator generates ______. It rotates around the
body, ___________the tumour from all directions.
This means the ______ receives a higher ____than the healthy tissue.
3)
R A
D I
A C
S I
Y P
P S
C I
E A
C L
M A
G S
S I
V I
N D
D X
A R
L C
N A
J M
M E
R S
I S
S O T I M
D I N G C
O M E A A
S R M H N
E H T O I
Y G A C L
A A E M V
N L R C O
L O T X E
T R U O M
O I E M E
www.teachingmedicalphysics.org.uk
I
O
X
I
D
Y
U
G
H
U
N
L
U
E
G
A
M
A
D
I
T
R
E
M
I
R
R
A
D
I
A
T
E
Radiotherapy
Treatment, Plan
Dose, Limit
Cells, Dividing
Mitosis, Meiosis
DNA, Damage
Linac, X-ray
Gamma, Irradiate
Cancer
Tumour
24
Nuclear Medicine
1) Sort these sentences into the correct order
 Patient injected with radiopharmaceutical
 Computer reconstructs image
 Drug labelled with radioisotope
 Patient imaged with Gamma camera
 Drug moves through bloodstream to organ
2) a) Which of these isotopes would be suitable for use as a tracer?
Circle your choice.
14
C
Co
99m
Tc
15
O
57
Carbon-14
Cobalt- 57
Technetium-99m
Oxygen-15
half-life: 5730 years
half-life : 271 days
half-life: 6hours
half-life : 2mins
b) Why did you choose that radioisotope?
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
3)
Sort the following statements into those that suggest radioactivity
is Beneficial those that suggest it is Harmful, and those that suggest
it could be Either
Gamma
rays can only be
completely stopped
by lead
Radiation most affects cells
that are dividing
Exposure to radiation can
lead to sickness and burns
Radiation damages DNA
and can cause mutations
www.teachingmedicalphysics.org.uk
Radiation can kill
cells
Radiation can cause cancer
but is also used to cure it
Radioactive
isotopes can be
used as tracers
in the body
25
PET
1) A cross section of a PET scanner is shown below. The detectors
shaded in show gamma rays which were detected at the same time.
By drawing lines between the
pairs of detectors that detected
gamma rays, can you draw where
you think the tumour is?
2)
3)
4)
5)
6)
7)
What does PET stand for?
What type of radiation do the isotopes used in PET scans emit?
What happens when this particle meets an electron?
What is then produced?
What is the name of the machine used to produce the isotopes?
Which of the following isotopes are used in PET scans (circle the
correct answers)
Carbon-10
Oxygen-15
Fluorine-16
Carbon-11
Oxygen-16
Fluorine-17
Carbon-12
Oxygen-17
Fluorine-18
8) Which of these is a PET scanner?
9) What are PET scans often used to detect?
www.teachingmedicalphysics.org.uk
26
Ultrasound
1) Find the words listed, in the fastest time possible!
A
L
D
O
L
Y
C
N
E
U
S
O
U
N
D
G
D
O
P
P
N
W
S
V
S
I
O
A
E
U
G
H
R
S
O
A
C
T
E
P
M
E
L
H
P
I
Q
U
E
G
Ultrasound
High, Frequency
Sound, Wave
Imaging
Foetus
P
H
I
N
Q
E
R
F
O
T
O
H
L
E
R
G
T
A
B
I
W
Y
I
H
N
A
R
O
H
L
V
C
R
C
S
E
I
N
E
Y
Sonar
Dolphin, Bats
Echo, Echoes
Doppler
2) Look at the images of each foetus below
a. Write the age of the foetus under each picture
(8 weeks, 18 weeks)
8cm
Age………………………………
14cm
Age………………………………
b. On the 8 week old foetus, label the head, arms and legs
c. On the 18 week old foetus, label the skull and spine
d. How long is a full term pregnancy? ………………………….
3) How many uses of ultrasound can you list (medical and industrial)?
……………………………………………………………………………………
……………………………………………………………………………………
……………………………………………………………………………………
...................................................................................................................
...................................................................................................................
Images courtesy of GE Healthcare (www.gehealthcare.com)
www.teachingmedicalphysics.org.uk
27
a) Match the correct age of the foetus in each surface rendered ultrasound
scan to the correct picture
10 week old foetus
14cm
12 week old foetus
21 week old foetus
18cm
32 week old foetus
b) Label the umbilical cord in each picture (hint, you can’t see it in
the picture of the 32 week old foetus)
9cm
4) A dolphin hears an echo from a fish 0.02 seconds after it makes a
noise (Hint, speed of sound in water is 1500m/s)
a. How far has the ultrasound wave travelled?
b. How far away is the fish?
c. The dolphin swims closer to a distance of 9m from
the fish, How long will it take to hear the echo?
Images courtesy of GE Healthcare (www.gehealthcare.com)
www.teachingmedicalphysics.org.uk
11cm
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The Electromagnetic Spectrum - Answers
Low Energy
radiowave
High Energy
infrared
visible ultraviolet
x-ray/gamma ray
2. a) abdomen, lungs, oesophagus
b) x-ray, gamma, visible
c) x-ray CT (computed tomography), nuclear medicine (or gamma camera),
endoscopy
3.
Imaging a fracture in a bone
Gamma rays (γ)
Thermography
X-rays
Treating Cancer
Infra Red (IR)
CT scans
Visible
Endoscopy
Ultraviolet (UV)
Photodynamic therapy
Bone scan
Infrared - Answers
2 a) Left: healthy
Right: Poor blood supply
b) Artery, vein and capillary
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X-Rays- Answers
1) a. One is a negative, one is positive, different noise levels in images, more detail
of bones seen in right hand image.
b. 1895
d. wedding ring
2) X-rays and other radiation can damage the DNA in cells and kill them. Cells
which are dividing rapidly are more likely to be killed, so we use x-rays to kill the
rapidly-dividing cancerous cells. We must make sure that healthy tissue is
undamaged. A Linear accelerator generates x-rays. It rotates around the body,
irradiating the tumour from all directions. This means the tumour receives a
higher dose than the healthy tissue.
Nuclear Medicine- Answers
1) Drug labelled with radioisotope
Patient injected with radiopharmaceutical
Drug moves through bloodstream to organ
Patient imaged with Gamma camera
Computer reconstructs image
2) a) Technetium-99m
b) It has a suitable half-life, Carbon-14 and Cobalt-57 decay too slowly and
Oxygen-15 decays too quickly, though O-15 is used in PET imaging.
3) Exposure to radiation causes sickness and burns – bad
Radioactive isotopes can be used as tracers in the body – good.
Radiation can cause cancer, but is also used to treat it - either
Others, arguments for both
PET- Answers
2)
3)
4)
5)
6)
7)
8)
9)
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Positron emission tomography
Beta-+, positrons, positive electrons
They annihilate
Two gamma rays, travelling in opposite directions
A cyclotron
C-11, O-15, F-18
A)a cyclotron b) PET scanner c) gamma knife
tumour
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Ultrasound - Answers
2)
leg
head
skull
spine
arm
Age………8 weeks…………………
Age…………18 weeks………….
d. 40 weeks
3) Pre natal scans, heart imaging, blood flow in arteries (Doppler ultrasound)
SONAR, precision cleaning, detecting flaws (manufacturing)
10 week old foetus
12 week old foetus
21 week old foetus
32 week old foetus
2) a. 30m, b. 15m c. 0.012s
Images courtesy of GE Healthcare (www.gehealthcare.com)
www.teachingmedicalphysics.org.uk
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Acknowledgements
This booklet and worksheets were written by Emily Cook.
The lessons were developed by Adam Gibson, Jeff Jones, David Sang,
Angela Newing, Nicola Hannam and Emily Cook.
We are grateful to the following people and institutions for providing
images:
Dr Gerard van Leeuwen
Dr Clare Elwell
Dr Kevin Howells
Dr Sandy Mosse
Dr Paul Campbell
Dr Topun Austin
Prof Alf Linney
Dr Jing Deng
Dr David Taylor
Nature
GE Healthcare
Elekta
Paul Burke
Cochlear Europe Ltd
The Nuclear Medicine and Radiotherapy Departments of the Royal Free
Hospital, London
UCL's Medical Illustration Unit
The Cromwell Gamma Knife Centre, London
Prof Jem Hebden
We have attempted to obtain permission and acknowledge the contributor
of every image. If we have inadvertently used images in error, please
contact us.
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