Magnetic resonance imaging (MRI), sometimes called nuclear magnetic resonance imaging (NMR), is a noninvasive, nonionizing diagnostic technique.
It is useful in detecting small tumors, blocked blood vessels, or damaged vertebral disks.
Because it does not involve the use of radiation, it can often be used where X-rays are dangerous.
Large magnets beam energy through the body, causing hydrogen atoms in the body to resonate. This produces energy in the form of tiny electrical signals.
A computer detects these signals, which vary in different parts of the body and according to whether an organ is healthy or not. The variation enables a picture to be produced on a screen and interpreted by a medical specialist.
What distinguishes MRI from computerized X-ray scanners is that most X-ray studies cannot distinguish between a living body and a cadaver, while MRI “sees” the difference between life and death in great detail.
More specifically, it can discriminate between healthy and diseased tissues with more sensitivity than conventional radiographic instruments like X-rays or CAT scans.
CAT, or computerized axial tomography, scanners have been around since 1973 and are actually glorified X-ray machines.
They offer three dimensional viewing but are limited because the object imaged must remain still.