# Technetium-99m is a radioactive isotope used as a medical tracer. Explain why Technetium-99m is well suited for use as a medical tracer, referring to its type of emission, half-life, and the difference between irradiation and contamination.

> OCR A-Level Physics A (H556) — 6.1 Capacitors · Explain · 5 marks

> Technetium-99m is injected into a patient and detected by a scanner outside the body. It has a half-life of 6 hours and decays into a stable, non-radioactive isotope that is safely excreted by the body.

## Mark scheme (5 marks)

1. Technetium-99m is a gamma emitter, and gamma radiation is the most penetrating type, allowing it to pass through body tissue and be detected outside the body.
2. A 6-hour half-life means there is sufficient time for the tracer to travel through the body and be detected before it decays away.
3. The short half-life means the patient is not exposed to radiation for a long period of time, reducing the long-term risk to the patient.
4. Irradiation is when an object is exposed to radiation from a source but does not itself become radioactive, so the patient's tissues are irradiated but not contaminated.
5. Contamination is the unwanted presence of radioactive atoms on or in a material; because Technetium-99m decays into a stable isotope that is excreted, the risk of long-term contamination is minimised.

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/technetium-99m-is-a-radioactive-isotope-used-8b6bfbe9) · Published by Druglandscape Ltd.