• Question: Why is an MRI scan using magnets better than an Xray?

    Asked by reecejack137 to Sam on 17 Jun 2013.
    • Photo: Sam Horrell

      Sam Horrell answered on 17 Jun 2013:

      I wouldn’t say either one is better than the other. Both techniques are valid for their own purpose.

      When you take an X-ray of a broken bone the bone absorbs the X-rays but the soft tissue doesn’t so you get a picture of the bone. In an MRI they use magnets which have an effect on the nuclei of atoms, mostly positive hydrogen from water. This makes the hydrogen spin and produce a radio frequency which is detected by the MRI scanner. Different amounts of water makes parts of the image darker or lighter and allow us to build up an picture. By rotating the magnetic field we can build up a 3D picture of the soft tissue in the body such as the brain which X-rays would just pass through.

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