What you can expect

By Mayo Clinic Staff

During the test

The MRI machine looks like a tube that has both ends open. You lie down on a movable table that slides into the opening of the tube. A technologist monitors you from another room. You can talk with the person by microphone.

The MRI machine creates a strong magnetic field around you, and radio waves are directed at your body. The procedure is painless. You don't feel the magnetic field or radio waves, and there are no moving parts around you.

During the MRI scan, the internal part of the magnet produces repetitive tapping, thumping and other noises. Earplugs or music may be provided to help block the noise. If you are worried about feeling claustrophobic inside the MRI machine, talk to your doctor beforehand. You may receive a sedative before the scan.

In some cases, a contrast material, typically gadolinium, may be injected through an intravenous (IV) line into a vein in your hand or arm. The contrast material enhances the appearance of certain details. The material used for MRIs is less likely to cause an allergic reaction than the material used for CT scans.

An MRI can last up to an hour or more. You must hold very still because movement can blur the resulting images.

During a functional MRI, you may be asked to perform a number of small tasks — such as tapping your thumb against your fingers, rubbing a block of sandpaper or answering simple questions. This helps pinpoint the portions of your brain that control these actions.

After the test

If you haven't been sedated, you may resume your usual activities immediately after the scan.

Aug. 17, 2013