Magnetic resonance imaging (MRI) is a painless test that uses magnets and radio waves to create a detailed picture of soft tissues and organs in your body. Unlike an X-ray, it does not use radiation. During this test, you’ll be positioned on a narrow table that slides through the opening of the tunnel-shaped scanner. In some cases, you’ll have a special dye injected into a vein in your hand or forearm, which helps certain parts of the scan stand out from others. MRIs take about 30 to 60 minutes to complete.