# A patient is given a radioactive tracer containing technetium before a medical scan. 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

> Technetium is a radioactive isotope widely used in hospitals to help produce images of the inside of the body. It has a half-life of 6 hours and is a gamma emitter. Once inside the body, it decays into a safe isotope that can be excreted.

## Mark scheme (5 marks)

1. Technetium is a gamma emitter, so the radiation can pass out through body tissue
2. Gamma radiation can be detected outside the body to form an image
3. The half-life of 6 hours is short enough that the tracer does not remain radioactive in the body for a long time, reducing harm to the patient
4. The half-life is long enough for the tracer to travel through the body and be detected before it decays away
5. Technetium decays into a safe isotope that can be excreted by the body, so it does not remain as a source of radioactive contamination

## Key terms

- [tracer](https://www.gradenine.co.uk/glossary/tracer)
- [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-patient-is-given-a-radioactive-2f9cb1e1) · Published by Druglandscape Ltd.