Magnetic resonance imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from torn ligaments to tumors. MRIs are very useful for examining the brain and spinal cord.

During the scan, you lie on a table that slides inside a tunnel-shaped machine. Doing the scan can take a long time, and you must stay still. The scan is painless. The MRI machine makes a lot of noise. The technician may offer you earplugs.

Before you get a scan, tell your doctor if you

• Are pregnant
• Have pieces of metal in your body. You might have metal in your body if you have a shrapnel or bullet injury or if you are a welder.
• Have metal or electronic devices in your body, such as a cardiac pacemaker or a metal artificial joint