Magnetic resonance imaging (MRI) uses a powerful magnetic field, radio waves and a computer to produce more detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. This painless, non-invasive test may be used to help diagnose or monitor treatment for a variety of conditions affecting the abdomen, brain, breasts, chest, pelvis, prostate, spine and more.
Unlike conventional X-ray exams and computed tomography (CT) scans, MRI does not use ionizing radiation. Instead, radio waves redirect alignment of hydrogen atoms within the body without causing chemical changes in the tissue. As the hydrogen atoms return to their usual alignment, they emit energy. The MR scanner captures this energy and generates a series of images, each of which shows a thin slice of the body. The images can then be studied from different angles by the radiologist.
Learn how to prepare for MRI and what to expect before, during and after the procedure.
Before the Procedure
Guidelines about eating and drinking vary with the specific exam. Unless you are told otherwise, you may follow your regular daily routine and take food and medications as usual.
You should tell the technologist if you have medical conditions, have had surgery recently or have medical or electronic devices in your body. These objects may interfere with the exam or potentially pose a risk, depending on their nature and the strength of the MRI magnet. Women should always inform their radiologist if they are breastfeeding or if there is any possibility they may be pregnant. If you have claustrophobia or anxiety, you may want to ask your physician for a mild sedative prior to your exam.
Wear comfortable, loose-fitting clothing to your exam. Metal objects, including jewelry, eyeglasses and dentures, may affect the MRI and should be left at home. You may be given a gown to wear and asked to remove jewelry, hearing aids and removable dental work.
During the Procedure
The technologist begins by positioning you on the moving exam table. Straps and bolsters may be used to help you stay still and maintain the correct position. Devices that contain coils capable of sending and receiving radio waves may be placed around or adjacent to the area of the body being studied.
If your radiologist wants to use a contrast dye during your MRI, an intravenous (IV) line will be put in a vein in your hand or arm and the dye will be injected into the IV line during the scan.
You will be placed into the magnet of the MRI unit and the radiologist and technologist will perform the exam while working at a computer outside of the room. It is important that you remain perfectly still while the images are being obtained, which is typically only a few seconds to a few minutes at a time. MRI exams generally include multiple runs, some of which may last several minutes. The entire exam is usually completed within 45 minutes.
After the Procedure
When the exam is complete, you will be asked to wait until the technologist verifies that the images are of high enough quality for accurate interpretation. Once this has been confirmed, the IV line will be removed and you can return to your normal activities.
After the images have been interpreted, your radiologist or referring physician will discuss the findings with you. Depending on the results of the MRI, additional tests or procedures may be scheduled to gather further diagnostic information.