# A hospital uses a radioactive tracer to monitor blood flow through a patient's body. The tracer emits gamma radiation and has a half-life of six hours. Explain why a gamma-emitting source with a short half-life is suitable for this medical use.

> AQA A-Level Physics (7408) — 3.8.1 Radioactivity · Explain · 5 marks

## Mark scheme (5 marks)

1. Gamma radiation can penetrate through the body / tissues to be detected outside the body
2. Gamma causes the least ionisation (inside the body), so causes least damage to cells/tissue
3. A short half-life means the activity / level of radiation decreases quickly
4. So the patient is not exposed to radiation for a long time / reduces long-term radiation dose to the patient
5. A long half-life would mean the source remains active / patient stays radioactive for a long time, increasing risk

## Key terms

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

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-cbe86638) · Published by Druglandscape Ltd.