Magnetic resonance imaging (MRI) is a safe and painless test that uses sound waves and a magnetic field to produce clear cross-sectional or three-dimensional images of the body’s tissues. Unlike an x-ray or a computed axial tomography (CAT) scan, MRI uses no radiation.

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 typically injected into the patient’s vein prior to the test.

Because of its safety and clarity, the MRI is a valuable tool that can aid in the diagnosis of a wide range of conditions, including:

• Cancer
• Musculoskeletal (bones and muscles) disorders
• Heart and vascular disease
• Brain abnormalities (aneurysm, stroke)
• Disorders of organs (lungs, liver, kidneys)

MRI can be helpful in diagnosing cancers of the male and female reproductive systems (e.g., ovary, prostate, endometrium) and to diagnose breast disorders, such as breast cancer or a rupture in a breast implant.

Because the MRI test relies on a large magnetic field, certain people should avoid the test. Pregnant women should generally avoid MRI because the risk to the developing fetus is unknown. Experts advise pregnant women not to have an MRI during the first trimester (12 weeks) of their pregnancy. In some cases, alternative imaging methods such as ultrasound can be used. However, there may be some instances when an MRI is warranted in pregnant women and the patient's physician will determine its necessity.

In addition, patients with implanted pacemakers and implantable cardioverter defibrillators (ICDs) should avoid the test. Patients with certain other medical implants, such as metal plates or heart valve replacements, should consult with their physician regarding the restrictions of the test. Women with intrauterine devices (IUDs) can safely have an MRI. In all cases, patients should inform the physician or technician of any metal objects present in their bodies.

An MRI scan 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 prior to the MRI. Using a less enclosed type of MRI machine, known as an open MRI, may be another option. If patients receive a sedative, they may be unable to drive following the test. Otherwise, patients are able to resume their daily activities after the MRI is completed.