# A hospital uses a radioactive tracer to produce images of a patient's internal organs. The tracer contains technetium, which is a gamma emitter with a half-life of 6 hours. Explain why technetium is a suitable radioactive isotope to use as a medical tracer inside the human body.

> OCR A-Level Physics B: Advancing Physics (H557) — 6.4 Medical imaging · Explain · 5 marks

> Medical tracers are substances that contain radioactive isotopes. They are introduced into a patient's body and detected from outside to produce images of internal organs. The choice of isotope used in a tracer must be carefully considered to ensure it is both effective and safe.

## Mark scheme (5 marks)

1. Technetium is a gamma emitter, so the radiation can pass through body tissue and be detected outside the body
2. Gamma radiation causes less ionisation inside the body, reducing damage to healthy cells / tissue
3. The half-life of 6 hours is long enough for the tracer to travel through the body and be detected
4. The short half-life means the technetium decays away quickly, reducing the long-term radiation dose to the patient
5. Technetium decays into a safe isotope that can be excreted by the body

## Key terms

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

## Related

- [Revision notes for OCR A-Level Physics B: Advancing Physics (H557)](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-d74ff991) · Published by Druglandscape Ltd.