MRI...How to Prepare
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. MRIs are very useful for examining the brain and spinal cord.
Read more ... http://www.nlm.nih.gov/medlineplus/mriscans.html