An MR image measures the ability of hydrogen nuclei to absorb radio frequency energy. All soft tissues can be visualized with MRI, however dense bone and air are difficult to image with this procedure.
Magnetic resonance relies on a very powerful magnetic field.
One tesla equals 10,000 gauss. The high magnetic fields can produce a very strong pull on metallic objects and attention needs to be paid to this fact or flying projectiles may result. The MR image, like a CAT scan image, is dependent on computer processing of the signals. Diagnoses utilizing MRI are based on the fact that abnormal tissue displaces normal structures and results in contrast-enhanced areas which can be visualized. MRI is extremely sensitive at showing areas of hemorrhage and timing the duration of the hemorrhage.