Magnetic Resonance Imaging (MRI) is a technique for taking pictures of the inside of the body. There is no harmful radiation in MRI. Instead, two natural forces are used: The natural magnetic properties of body tissues, and the radio waves released by the tissues when they are within a strong magnetic field. MRI uses a magnet to make the magnetic field stronger. It then translates the radio waves into an image that can be photographed.

Why Do the Exam?
An MRI procedure is totally painless, completely safe, and has no known side effects. This makes MRI better than X-rays or CT scans for getting very clear pictures of your cartilage, bone marrow, muscles, ligaments and spinal cord. It can also picture the fluid in your brain and spine. Many parts of the body can be studied with MRI, and the images produced are very detailed and clear. With MRI, images can be produced through any plane and from any angle of the area being studied. The brain, heart, and spine are the areas commonly studied with MRI.

How the Exam Works
MRI is safer than conventional X-rays, because its images are formed by two natural forces to obtain the images. The signal that helps generate MRI images comes from hydrogen nuclei, which are found in almost all body tissue, interacting with a strong magnetic field. Structures that contain fairly low amounts of hydrogen--like bone or air in the lungs and bowel--do not show up on the images. You will be exposed to a strong magnetic field, and the MRI machine then translates the radio waves released by your body tissues into clear images that can be viewed for study.

Doing the Exam
MRI takes between 30 and 60 minutes, and requires nothing of you other than you lie as still as possible while the test is being done. Once you get to the hospital, you will be asked to change into a hospital scrubs and lie down on a table. The table will then slide into the inside of a huge magnet. You will be able to talk to the technologist conducting the test, who will be watching the examination from the next room. You will not have any pain during the MRI, although you may hear the noise of the magnet, which sounds like a drum. It may also take you a few minutes to get used to being in the enclosed space of the magnet. When the test is over, the table on which you are lying will slide out from the magnet. You will then be able to get dressed in your own clothes and go about your usual routine.

Your Preparation
MRI is always done at the hospital since it requires equipment that is bulky and expensive. It is often done as an outpatient procedure. You will be asked to remove all metallic objects--keys, money, jewelry, and so on--so that they will not interfere with the test. You should tell the doctor if you have any metallic implants in your body. These might include artificial heart valves, joint replacements, bone plates or similar devices. Patients with cardiac pacemakers and some other implanted foreign bodies cannot at present be examined by MRI.

After the Exam
After the MRI you will be able to go on with your usual activities. There are no known aftereffects.

Your MRI images will be examined and interpreted by a doctor trained in MRI. They will then forward the results to your doctor, who will discuss the findings with you. Further studies and treatment may be recommended.