# Explain how an MRI scanner produces an image of soft tissues inside the body, and state one advantage of MRI over X-ray imaging when examining soft tissue organs.

> AQA A-Level Physics (7408) — 3.10.4 Non-ionising Imaging · Explain · 5 marks

> MRI (magnetic resonance imaging) is a non-ionising imaging technique used widely in hospitals to examine internal soft tissue structures such as the brain and spinal cord.

## Mark scheme (5 marks)

1. MRI uses a strong magnetic field (and radio waves) applied to the body
2. The magnetic field causes hydrogen nuclei (protons) in the body to align / respond to the field
3. When the radio waves are switched off, the nuclei emit signals / release energy as they return to their original alignment
4. Signals from different tissues differ / the strength or timing of signals depends on tissue type, allowing a detailed image to be constructed
5. MRI does not use ionising radiation (so there is no risk of cell/DNA damage) / MRI gives much better contrast / detail for soft tissue than X-rays

## Key terms

- [MRI](https://www.gradenine.co.uk/glossary/mri)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-an-mri-scanner-produces-99487d0e) · Published by Druglandscape Ltd.