AQA GCSE Physics Foundation (8463), Foundation tier · Atomic structure › Hazards and uses of radiation
Practise Uses of nuclear radiation. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How nuclear radiation is used in medicine to explore internal organs (tracers) and to control or destroy unwanted tissue (radiotherapy), and how to weigh up benefits against risks using data. Expect 'describe' and 'explain' questions and 6-mark 'evaluate' questions. GCSE Physics only, not in Combined Science.
Key facts
Tracer: gamma emitter with a short half-life, detected outside the body by a gamma camera
Gamma for tracers: passes out of the body and is weakly ionising
Radiotherapy: ionising radiation kills cancer cells
External beams from several directions: large dose to tumour, smaller dose to healthy tissue
Internal source: placed in or next to the tumour
Use radiation when the benefit is greater than the risk
Notes
Exploring internal organs: tracers
A radioactive tracer is swallowed or injected. It travels through the body to the organ being investigated.
A detector outside the body (a gamma camera) builds up an image, showing how well the organ is working or where there is a problem.
The tracer should emit gamma rays: they pass out of the body to the detector, and they are weakly ionising, so they do little damage.
It should have a short half-life (a few hours), so the activity in the body soon falls. Technetium-99m (half-life about 6 hours) is widely used.
The thyroid gland absorbs iodine, so a radioactive isotope of iodine can be used to examine it.
Controlling or destroying unwanted tissue
diagram
Ionising radiation damages and kills cells, so it can be used to destroy cancer cells. This is radiotherapy.
External: beams of gamma rays are aimed at the tumour from several directions (the source moves around the patient). The tumour gets a large dose; healthy tissue gets a smaller one.
The beams overlap only at the tumour, so it gets a large dose.
Internal: a small radioactive source is placed in or next to the tumour, so most of the radiation is absorbed by the tumour cells.
Radioactive iodine can be swallowed to destroy unwanted thyroid tissue, because the thyroid absorbs iodine.
Weighing up the risks
Any exposure to ionising radiation carries some risk: healthy cells can be damaged, and the risk of cancer rises slightly.
Radiation is used when the benefit, such as diagnosing or treating a serious illness, is greater than the risk.
Perceived risk is how dangerous people think something is. It can differ from the real risk shown by data, so compare doses, e.g. with the yearly dose from background radiation.
Don’t lose marks
Saying a tracer should emit alpha. Alpha would not leave the body and is strongly ionising, so it would damage cells.
Saying a tracer should have a long half-life 'so it lasts longer'. The patient would stay radioactive for too long.
In 'evaluate' questions, giving only benefits or only risks, or giving no conclusion.
Saying external radiotherapy makes the patient radioactive. The patient is irradiated, not contaminated.
More tips
Memory tricks
Tracer checklist: Gamma + Short half-life ('GS: Get Scanned').
Radiotherapy: aim from many angles, all meeting at the tumour.
Evaluate = benefits + risks + data + a justified conclusion.
Exam technique
In a 6-mark evaluation, use the numbers given, e.g. compare the dose with the yearly background dose.
Use the words 'ionising', 'damages cells' and 'half-life' in medical-use answers.
When asked why something is suitable, give each property AND the reason it helps.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 4
Name two medical uses of nuclear radiationExploring internal organs with tracers; destroying unwanted tissue such as tumours.
Grade 5
Describe how a medical tracer is usedA gamma emitter is swallowed or injected and detected outside the body by a gamma camera.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Give one way that nuclear radiation is used in medicine to control or destroy unwanted tissue.
Radiotherapy, e.g. aiming gamma rays at a tumour to kill the cancer cells.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) Which two of the following are uses of nuclear radiation in medicine? Tick (✓) two boxes.[2]
Exploring internal organs using a radioactive tracer
Destroying cancer cells (radiotherapy)
Measuring body temperature
Measuring blood pressure
(b) A radioactive tracer is injected into a patient. The radiation is detected by a camera outside the body. Which type of radiation should the tracer emit? Tick (✓) one box.[1]
Alpha
Beta
Gamma
(c) Give one reason for your answer.[1]
Show the answer and mark scheme
(a)Answer: Exploring internal organs using a radioactive tracer; Destroying cancer cells (radiotherapy)
(b)Answer: Gamma
(c)Answer: Gamma rays pass out of the body to the camera and are only weakly ionising.
it can pass out of the body to reach the camera / it is the least ionising, so it causes the least damage to cells
Question 2Medium6 marks
Technetium-99m is used as a medical tracer. It is injected into a patient and collects in the organ being examined. A camera outside the body detects the radiation emitted. Technetium-99m emits gamma rays and has a half-life of 6 hours.
(a) Explain why an isotope that emits gamma rays is used as a tracer.[2]
(b) Explain why a half-life of 6 hours is suitable for a tracer.[2]
(c) Explain why an isotope that emits alpha particles would not be suitable as a tracer.[2]
Show the answer and mark scheme
(a)Answer: Gamma rays pass right out of the body to the camera, and they are only weakly ionising.
gamma rays are very penetrating, so they pass out of the body and reach the camera
gamma rays are weakly ionising, so they cause little damage to cells
(b)Answer: Long enough to complete the scan, but short enough that the activity soon becomes very low, keeping the dose small.
it is long enough for the tracer to reach the organ and for the images to be taken
it is short enough that the activity falls quickly after the scan, so the patient receives only a small dose
(c)Answer: Alpha particles would not get out of the body to the camera, and their strong ionisation would damage the tissue.
alpha particles would be absorbed in the body, so they could not be detected by the camera outside
alpha particles are strongly ionising, so they would damage the cells around the tracer