What is an MRI scan?

The scanner records signals from water in body tissues and turns them into cross-sectional images. It can show the brain, spine, joints, organs and soft tissues in considerable detail. A radiographer positions you on a padded table that moves into a short, open-ended tunnel. The machine makes loud tapping and knocking sounds, so you usually receive headphones or ear protection.

Some examinations use a contrast medicine through a vein to make particular tissues or blood vessels easier to distinguish. Contrast is not needed for every scan. The images help a clinician investigate symptoms, monitor a known condition or plan treatment; they do not by themselves provide a final diagnosis. A biopsy may be needed when tissue must be examined.

Follow the imaging centre's instructions about eating, drinking and regular medicines. Tell the team about implanted devices, metal fragments, surgical clips, hearing devices, medication pumps and tattoos or patches containing metal. Remove jewellery, watches, cards and loose metal before entering the scanning room. Wear clothing without metal fasteners when advised.

During the scan, remain as still as you can and use the call button if you need help. Tell the team beforehand if enclosed spaces are difficult for you; they can discuss practical support. You may be able to listen to music and communicate throughout the examination.

Contact the requesting clinician promptly if the symptoms that led to the scan are worsening or new. Seek urgent medical care for sudden weakness, difficulty speaking, a seizure, severe breathing trouble or a sudden severe headache. After contrast, get medical help for trouble breathing, facial swelling or widespread hives.

Ask which body area will be scanned, whether contrast is planned, how long the appointment may take, and when you can expect the report. You can also ask whether the scan is investigating a specific condition and what other test might be considered if the images do not answer the clinical question.