Magnetic Resonance Imaging (MRI) Machine. Courtesy of Intermountain Medical Imaging, Boise, Idaho. Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures that are inside the body. During the MRI test (also called an MRI scan), you usually lie on your back on a table that is part of the MRI scanner. Your head, chest, and arms may be held with straps to help you stay still. The table will then slide into the round opening of the magnet. Inside the scanner you will hear a fan and feel air moving.