What should you know about MRI and CAT scans?

A CAT scan is another name for CT scan and uses X-rays to create cross-sectional images quickly. It can show bones, bleeding, lung tissue, and many abdominal findings clearly. MRI uses magnetic fields and radio waves, often providing detailed contrast between soft tissues such as the brain, spinal cord, and muscles. MRI avoids ionising radiation but may take longer and requires careful screening for metal and implanted devices. Contrast may be used with either test. Neither scan alone confirms every diagnosis; a biopsy or other assessment may be needed.

Your clinician chooses the test according to the suspected problem, the body region, urgency, and previous images. Tell the imaging team about pregnancy, kidney disease, allergies, implanted devices, metal fragments, and difficulty staying still. Follow instructions about fasting, medicines, clothing, and contrast. If imaging is being used to investigate a brain tumour or another concern, ask how the result will guide the next step.

Seek urgent help for sudden weakness, new speech difficulty, a seizure, severe sudden headache, collapse, or rapidly worsening confusion. After contrast, get urgent help for breathing difficulty, fainting, or swelling of the face or throat. Do not delay emergency assessment while waiting for a planned scan.

Ask whether MRI or CT is intended, whether contrast is needed, how quickly the result is required, and whether an earlier scan can answer the question. Ask whether a biopsy or another test is needed after imaging.