Courtesy of Diane Newton, MD, and Drew Taylor, Director of Advanced Open Imaging, Meridian, 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 space that contains the magnet.

Inside the scanner you will hear a fan and feel air moving. You may also hear tapping or snapping noises as the MRI scans are done. It is very important to stay completely still while the scan is being done.

An open MRI machine has a larger opening compared to a standard MRI machine. Some have magnets that do not completely surround your body, as shown here. But this kind of open MRI cannot do some types of MRI scans.

People who get nervous in small places (are claustrophobic) may feel better using an open MRI machine. An open MRI machine also may be easier to use for people who are very overweight or obese. But not all medical centers have this kind of MRI machine.