# Technetium-99m is a radioactive isotope used as a medical tracer. Explain why Technetium-99m is suitable for use as a medical tracer, including reference to its half-life, the type of radiation it emits, and the difference between irradiation and contamination in this context.

> OCR A-Level Physics B: Advancing Physics (H557) — 6.3 Nuclear and particle physics · Explain · 5 marks

> Technetium-99m is injected into a patient's bloodstream and travels through the body, where it can be detected by external equipment to produce images of internal organs. It has a half-life of 6 hours and is a gamma emitter.

## Mark scheme (5 marks)

1. Technetium-99m has a half-life of 6 hours, which is short enough that it decays away relatively quickly after the procedure.
2. The half-life is long enough for the isotope to flow through the body and be detected before it decays away.
3. Technetium-99m is a gamma emitter, meaning gamma radiation can pass through body tissue and be detected externally.
4. The patient is irradiated by the Technetium-99m, meaning they are exposed to radiation from the source but do not become permanently radioactive themselves.
5. Contamination would be hazardous because radioactive atoms would remain on or in the patient for a long time, continuing to emit radiation; irradiation from a short half-life tracer is less hazardous because activity quickly decreases.

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/technetium-99m-is-a-radioactive-isotope-used-1daa4b56) · Published by Druglandscape Ltd.