# A hospital uses a radioactive tracer to investigate the function of a patient's thyroid gland. The tracer emits gamma radiation and has a short half-life. Explain why a gamma-emitting source with a short half-life is suitable for use as a medical tracer inside the body.

> OCR GCSE Physics A: Gateway Science (J249) — P4.4 Uses and hazards of radiation · Explain · 4 marks

> Radioactive tracers are injected into patients and their movement through the body is monitored from outside using detectors.

## Mark scheme (4 marks)

1. Gamma radiation can penetrate through body tissues to reach detectors outside the body
2. Alpha or beta radiation would be absorbed by body tissues and could not be detected externally
3. A short half-life means the activity/radioactivity decreases quickly after use
4. This reduces the radiation dose received by the patient, lowering the risk of cell damage or cancer

## Key terms

- [gamma radiation](https://www.gradenine.co.uk/glossary/gamma-radiation)
- [tracer](https://www.gradenine.co.uk/glossary/tracer)
- [half-life](https://www.gradenine.co.uk/glossary/half-life)

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-hospital-uses-a-radioactive-tracer-83709f76) · Published by Druglandscape Ltd.