How does an MRI scan machine work?

The scanner’s magnetic field temporarily aligns hydrogen particles that are naturally present in body tissues. Radio signals then disturb that alignment. As the particles return to their usual state, they release signals that are detected by receiver coils placed near the area being examined. A computer turns these signals into slices and other views of the body.

Different tissues return signals at different rates, creating contrast between organs, fluid, muscle, and abnormal areas. This makes MRI useful for many soft-tissue questions. MRI does not use ionising radiation. The machine still requires careful screening because its strong magnetic field can interact with some implants and loose metal.

Lie as still as you can while each sequence runs; movement can reduce image clarity. You may hear loud rhythmic noises and be asked to hold your breath briefly for some body areas. Tell staff about implants, metal fragments, pregnancy, kidney problems, allergies, and claustrophobia. If contrast is planned, follow the centre’s instructions and report any previous reaction.

Tell staff straight away if you feel unusual heating, pulling, pain, or distress inside the scanner. After contrast, seek prompt medical advice for widespread hives, swelling, breathing difficulty, or faintness. Urgent symptoms such as a seizure, sudden weakness, trouble speaking, or a sudden severe headache need immediate care independently of MRI results.

Ask what the scan is intended to investigate, whether contrast will be used, and whether you need to change any medicines. Ask how the images will be interpreted and whether further testing, including a biopsy, may be considered.