Magnetic Resonance Imaging (MRI) uses radio waves in the presence of a strong magnetic field that surrounds the opening of the MRI machine where the patient lies to get tissues to emit radio waves of their own.
Different tissues (including tumors) emit a more or less intense signal based on their chemical makeup, so a picture of the body organs can be displayed on a computer screen. Much like CT scans, MRI can produce three-dimensional images of sections of the body, but MRI is sometimes more sensitive than CT scans for distinguishing soft tissues.
![MRI without contrast](https://webarchive.library.unt.edu/eot2008/20090131064640im_/http://imaging.cancer.gov/images/Documents/c4e50ffa-c6a8-445d-8aa8-7a5b5d0f383b/mri1.gif) |
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(Top) MRI scan without contrast showing possible tumor in the liver. (Bottom) MRI scan of the same patient using contrast. Images courtesy of Dr.
Peter Choyke, Clinical Center, NIH. |
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