MedlinePlus maintains a library of search topics, including MRI scans. This site is a project of the National Institutes of Health and the National Library of Medicine, which is the world's largest medical library, according to the website.
Magnetic resonance imaging, or MRI, technology produces images of structures within the body, says MedlinePlus. Doctors examine these images in order to see the extent of damage caused by trauma or to look for abnormalities such as tumors. Because the machine uses magnetism, patients having an MRI scan must remove all metal jewelry and alert the technician to any metal implants. The patient lies prone for the duration of the scan, which takes place in a tube-shaped machine.