Magnetic resonance imaging, also known as MRI, uses radio waves and a strong magnetic field instead of X-rays to provide clear, detailed pictures of internal organs and tissues. MRIs are especially helpful in providing images of the brain, muscles, heart and cancers in the body as they are good at showing contrast between soft tissues. The MRI scanner is a tube surrounded by a giant circular magnet. The patient lies on a bed that goes into the magnet, and the magnet and radio waves send information into a computer. The computer processes the information and then produces an image.
The test is painless; however, patients who are claustrophobic may find it somewhat uncomfortable. Due to the incredibly strong magnetic field generated by an MRI, patients are screened prior to going into the magnet.