# Technetium-99m is widely used as a radioactive tracer in hospitals. Explain why technetium-99m is well suited for use as a medical tracer, referring to its half-life, the type of radiation it emits, and the safety implications for the patient.

> OCR A-Level Physics A (H556) — 6.4 Medical imaging · Explain · 5 marks

> A patient at a hospital is injected with a small amount of technetium-99m so that doctors can monitor blood flow through an organ. Technetium-99m is a gamma emitter with a half-life of 6 hours, and it decays into a stable isotope that can be excreted by the body.

## Mark scheme (5 marks)

1. Technetium-99m is a gamma emitter, and gamma radiation is the most penetrating type, so it can pass out through body tissue and be detected externally.
2. Alpha or beta radiation would be absorbed by the body/tissue before it could be detected, making them unsuitable as tracers.
3. A half-life of 6 hours is long enough for the tracer to flow through the body and be detected / for the medical procedure to be completed.
4. The short half-life means the technetium-99m decays away quickly, so the patient is not exposed to radiation for a long time / reducing long-term risk to the patient.
5. Technetium-99m decays into a stable, safe isotope that can be excreted by the body, so there is no long-term build-up of radioactive material inside the patient.

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/technetium-99m-is-widely-used-as-a-a631a90b) · Published by Druglandscape Ltd.