Magnetic resonance imaging (MRI) is a non-invasive medical test that utilises a powerful magnetic field, radio waves and a computer to produce detailed pictures of the internal structures of the body. Unlike conventional X-ray examinations and computed tomography (CT) scans, MRI does not utilise ionising radiation. Instead, radio waves are used to temporarily change the alignment of hydrogen atoms that exist naturally within the body. As the hydrogen atoms return to their usual alignment, they emit energy that varies according to the type of body tissue from which they come. The scanner captures this energy and creates a picture of the tissues scanned based on this information.