Worksheet
Questions 1 to 10 have only one correct answer. Write down which answer, A,B,C or D you
believe is correct.
1.
PET is the acronym for which of the following:
A
B
C
D
2.
PET scanning is used for a number of different reasons. Which of the following is
PET scanning not normally used for?
A
B
C
D
3.
Positive electron tunneling
Polarised electric topography
Positron emission tomography
Positional elevated testing
Identifying some tumours
Treating patients with asthma
Investigating the damage caused to a heart after a heart attack
Studying the advance of Alzheimer’s disease
Before a patient can have a PET scan it is normal for them to:
1
2
3
4
Travel to a specialist hospital
Drink a barium rich liquid
Eat nothing for 4 to 6 hours beforehand
Be injected with a radioactive isotope
Identify which of the statements above are correct.
A
B
C
D
4.
4 only
2 and 4 only
3 and 4 only
1, 3 and 4 only
The radioactive isotope that is injected into the patient decays by positron
emission. A positron is:
A
B
C
D
A particle with the mass of an electron and the charge of a neutron
A particle with the mass of a proton and the charge on an electron
Identical to a neutron but with a positive charge, (a neutron positive)
Identical to an electron, but with a positive charge, (a beta positive)
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5.
A positron very rapidly meets an electron and annihilates with it. This means that:
A
B
C
D
6.
Which of the following statements is a correct description of the two gamma rays
which are emitted following the annihilation of a positron and an electron?
A
B
C
D
7.
3
4
Beta minus decay occurs when a neutron becomes a proton and an
electron is emitted
Beta plus decay occurs when a proton becomes a neutron and a positron
is emitted
With beta minus decay the atomic number is unchanged
With beta plus decay the atomic number decreases by 1
A
B
C
D
1 and 2 only
2 and 3 only
1,2 and 3 only
1,2 and 4 only
2
The atoms of different isotopes of carbon have:
A
B
C
D
9.
They are emitted in the same direction
They are emitted at 180O to each other
They are absorbed by the body tissue
They are absorbed by the radioactive isotope
Which of the following statements describing beta decay are true?
1
8.
The positron and electron are destroyed and gamma rays are emitted
The positron and electron form a nucleus and gamma rays are emitted
The positron and electron combine with the isotope to produce oxygen 18
The positron and electron combine with the isotope to produce fluorine 18
The same number of protons but different mass numbers
The same number of neutrons but different mass numbers
The same number of protons and the same mass numbers
The same number of neutrons and the same mass numbers
A cyclotron is used to produce the radioactive isotope injected in PET scanning.
1
2
3
4
Stable nuclei become radioactive
Protons are accelerated to high energies
Protons are injected into the cyclotron
Stable nuclei are bombarded with protons
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The order in which these events take place is:
A
B
C
D
10.
1,2,3,4
4,1,3,2
3,2,4,1
3,4,1,2
The cyclotron must be sited close to the PET scanner. This is mainly because:
A
B
C
D
It is dangerous to transport radioactive materials a long way
The radioactive isotope produced has a short half life
Liquids may be spilt if they are carried a long way
The cyclotron and the PET scanner use the same power supply
Questions 11 to 15 are a little more challenging.
11.
a) Fluorine-18 is one of the radioactive nuclides used in PET scans. Fluorine-18 can
be made by bombarding oxygen-18 nuclei with protons. The equation for this reaction
is:
18
8
O
1
+ 1
p
=
18
9
F
+
X
What is the identity of the other product, X, in this reaction?
b) Carbon-11 can also be used as a tracer in PET scans. Complete the equation below
that describes the decay of carbon-11, with the emission of a positron. What is the
product Y?
11
6
C
0
= Y + 1 e
12.
Fluorine 18 has a half life of 110 minutes. A sample fresh from the cyclotron has an
activity recorded by the geiger counter as 200 counts per minute. What will be the
activity of the same sample recorded by the geiger counter 11 hours after the sample
has been taken from the cyclotron?
13.
Identify the isotope Fluorine-18 on the nuclear stability chart shown below.
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Does Fluorine-18 have too many or too few protons for stability?
Why will positron (beta plus) emission from Fluorine-18 create a stable nucleus?
Which of the following carbon isotopes would you suggest could also decay by
positron emission?
11
6
C,
12
6
C,
13
6
C,
14
6
C,
15
6
C
By considering the chart, which of these carbon isotopes do you believe are stable?
14.
The detectors in a PET scanner are designed to detect gamma rays.
a) Explain, in terms of the penetration properties of beta and gamma radiations,
why it is not practical to detect the positrons emitted from the decaying isotope,
but it is practical to detect the gamma rays.
b) Explain in terms of momentum why the two gamma rays from one
annihilation are emitted in exactly opposite directions.
c) The two gamma rays emitted from the annihilation have energy. Where did
this energy come from?
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15.
Write a sentence to explain each of the following statements concerning PET scans.
i) The isotope producing cyclotron is sited very close to the PET
scanner.
ii) Cancerous tumours take up more of the glucose that contains the
radioactive tracer than normal cells.
iii) Patients are advised to avoid contact with children and pregnant
women for the rest of the day after a PET scan.
iv) A PET scan may be used to decide that a patient should be given
palliative care rather than treatment to cure the complaint.
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