What is MRI?
Magnetic resonance imaging is a way to look inside the body without using radiation or x-rays. MRI can produce two- or three-dimensional images of what’s going on inside the body. It uses a large magnet, radio waves, and a computer to make these pictures. The magnet is large enough to surround the patient.
Why is MRI important?
MRI images are extremely precise and tell physicians about types of tissue inside the body. For this reason, MRI can reduce the number of diagnostic surgeries. MRI uses no radiation to make images.
How does MRI make images?
The body is composed of particles called atoms. Normally, the protons of these atoms spin in a random direction. In a MRI scanner, a strong external magnetic field is used to temporarily line up all the protons. Next, a radio frequency signal is sent to the magnetic field. The signal makes the protons move out of their alignment, like a spinning top pumping into another spinning top. When the radio signal is turned off, the atoms move back to their original position and release energy. A receiver in the MRI scanner picks up this energy and determines how long it took the atoms to return to their original position. This time in influenced primarily by the type of tissue the atom is in. Nest, a computer uses this information to construct an image on a TV screen. This image can be printed onto film or saved as a file.
What are some typical uses of MRI imaging?
- Diagnosing brain and nervous system diseases, such as multiple sclerosis, tumors, spinal cord and back problems, hydrocephalus, stroke, trauma, and vascular disease (carotid artery stenosis)
- Looking for evidence that a cancer is spreading or making sure it has not spread
- Diagnosing problems of the muscles and skeleton, such as injuries to knees, shoulders, back, ligaments, tendons, cartilage, and bones.