Magnetic Resonance Imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from torn ligaments to tumors to damaged organs.
During the scan, you lie on a table that slides inside a tunnel-shaped machine. The scan can take a long time to perform, and you must stay still. It may include holding your breath for up to 20 seconds at a time. The scan is painless though you may sense a slight warmth. The MRI machine makes a lot of noise, so you will be offered ear protection. Tell Your Doctor if You:
* Are pregnant
* Have pieces of metal in your body. (It is a large Magnet)
* Have electronic devices in your body, such as a cardiac pacemaker You will not be allowed to take the test if any of these conditions exist. Source:
http://medlineplus.gov/ | 
