Magnetic resonance imaging (MRI) is a safe and painless test that produces clear cross-sectional or three-dimensional images of the body’s tissues, even through bone and other obstructions. Unlike x-rays and computed axial tomography (CAT) tests, which use radiation, MRI relies on radiofrequency sound waves and a magnetic field to produce images of the body.

Because of its safety and clarity, the MRI is a valuable tool that can aid in the diagnosis of a wide range of conditions. There is little preparation necessary for the standard MRI and requires only that the patient remove all metal objects such as jewelry prior to the test.

MRI may be administered with or without the use of a dye, known as a contrast medium. The contrast medium helps increase the visibility of organs and tissues for a more detailed image. If a contrast medium is used, it is usually injected into the patient’s vein prior to the test. In some cases, the contrast material may be swallowed in a liquid.

MRI is often used to diagnose cancer and to determine the extent of the disease. It is most effective in detecting cancer of the musculoskeletal system, brain and spinal cord and internal organs such as the lungs, liver and kidney. It is a common choice for examining the male and female reproductive systems to detect abnormalities and functional disorders. In addition, physicians are increasingly using MRI to supplement mammography to aid in breast cancer diagnosis.

Because the MRI test relies on a large magnetic field, certain people should avoid the test. These include patients with implanted pacemakers and implantable cardioverter defibrillators (ICDs). Patients with certain other medical implants, such as metal plates or heart valve replacements, should consult their physicians about the restrictions of the test. In all cases, patients should inform the physician or technician of any metal objects present in their bodies. Also, pregnant women should generally avoid MRI because the risk to the developing fetus is unknown. However, there may be some instances when an MRI is warranted in pregnant patients.

The test may take up to one hour to complete in a rather tight space. Patients who become nervous or anxious in small spaces may wish to ask their physician about receiving a sedative before the MRI. Using a less enclosed type of MRI machine, such as an open MRI, may be another option. If patients receive sedatives, they may be unable to drive home following the test. Otherwise, patients are free to go about their daily activities after the MRI is completed.