Uses of nuclear radiation — AQA GCSE Physics
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Uses of nuclear radiation explained
Medicine uses nuclear radiation in two distinct ways.
Read the full explanation
For exploration, a tracer containing a gamma-emitting isotope is swallowed or injected and taken up by the organ under investigation; because gamma radiation is weakly ionising and highly penetrating, it passes out of the body to a detector such as a gamma camera, building an image of how the organ is working with a modest dose to the patient. For control or destruction of unwanted tissue, high-energy gamma beams are aimed at a tumour from several directions so the beams cross only at the tumour, or a sealed source is implanted next to it. Alpha emitters are never used as tracers, since the radiation would be absorbed by tissue and never escape to be detected.
Students should be able to: describe and evaluate the uses of nuclear radiations for exploration of internal organs, and for control or destruction of unwanted tissue evaluate the perceived risks of using nuclear radiations in relation to given data and consequences.
Evaluating means weighing, not listing. Set the benefit against the risk using the figures you are given. A tracer scan may diagnose a condition that could not otherwise be found, at a dose of a few millisieverts, which can be compared directly with the annual background dose in the same units. Radiotherapy may destroy a tumour, but the beam also passes through healthy tissue, causing side effects and a small added risk of a second cancer. A short half-life isotope cuts the dose because its activity falls away quickly after the procedure. Perceived risk is what people believe the danger to be, which is often higher than the measured risk; a good evaluation says which figures support the decision and reaches a conclusion.
Your focus
- Describe how a gamma tracer produces an image of an internal organ.
- Justify the choice of a gamma emitter with a short half-life for use as a tracer.
- Describe two ways radiation is used to control or destroy unwanted tissue.
Show all 6 objectives
- Evaluate a medical use of radiation by comparing a quoted dose with the annual background dose.
- Explain why perceived risk may differ from the risk the data supports.
- Reach and justify a conclusion about whether a procedure's benefit outweighs its risk, citing the figures given.
Uses of nuclear radiation exam tips
Marking Points
- one mark for describing a tracer as a gamma-emitting isotope taken into the body and followed by a detector outside it
- one mark for gamma being chosen because it penetrates out of the body and is weakly ionising
- one mark for external radiotherapy directing gamma beams at a tumour, rotating or crossing them so healthy tissue receives less
- one mark for internal treatment using an implanted or injected source placed in or next to the unwanted tissue
- one mark for a benefit stated using the data provided, such as the proportion of patients successfully diagnosed or treated
- one mark for a risk stated using the data, such as the dose in millisieverts compared with the annual background dose
- one mark for explaining that a short half-life tracer limits the dose because its activity falls quickly
- one mark for weighing the two against each other rather than listing them separately
- one mark for a conclusion that refers back to the figures given
Examiner Tips
- 💡Say what the radiation does, not just what the technique is called, because the mark is usually for the mechanism.
- 💡Name the radiation type and give a reason for it; 'gamma, because it penetrates out of the body' is a complete point.
- 💡Separate exploration from destruction in your answer, since the question usually wants one of each.
- 💡Quote at least one number from the stem in your evaluation; an evaluation with no data rarely reaches the top band.
- 💡Use a comparison of like with like, for instance a procedure dose against the annual background dose, both in millisieverts.
- 💡Finish with an explicit judgement; leaving the answer balanced but undecided loses the final mark.
Common Mistakes
- choosing an alpha emitter for a tracer, when the radiation could not leave the body
- saying radiotherapy destroys only cancer cells and leaves healthy tissue untouched
- describing a tracer as a treatment that cures the illness
- confusing an X-ray image, which uses an external machine, with a gamma tracer scan
- using a long half-life isotope as a tracer and so leaving the patient with a prolonged dose
- listing benefits and risks in two columns with no comparison or conclusion
- answering from memory when the question supplies data to be used
- treating perceived risk as identical to measured risk
- asserting that all radiation is equally dangerous regardless of dose or type
- giving a conclusion that contradicts the figures quoted earlier in the answer