 agnetic
Resonance Imaging, or "MRI," represents one of the newest and
most exciting fields of medical imaging. Like CT, MRI produces images which
are the visual equivalent of a slice of anatomy. However the MRI is also
capable of producing those images in an infinite number of projections through
the body.
MRI
uses a large magnet, radio frequencies and a computer to produce its
images. As the patient enters an MRI scanner, his body is surrounded
by a magnetic field up to 8,000 times stronger than that of the earth.
|
|
The
human body is made of tiny particles called atoms. At the center of all
atoms are spinning particles called nuclei. Normally, nuclei spin at many
different angles. The magnetic field of the MRI scanner makes the nuclei
spin at the same angle.
The scanner then subjects the nuclei to a radio signal, temporarily
knocking them out of alignment. When the signal stops, the nuclei
return to the aligned position, releasing their own faint radio frequencies.
A part of the scanner known as the coil, working like a radio antenna,
receives these frequencies. The data is then computer processed to
produce very detailed images of the human anatomy.
|
|
With MRI technology it is possible to see, with unparalleled clarity,
the brain and the tiny nerves which make up the spinal cord. Understandably,
MRI has become the technology of choice for examining the brain, neck
and spinal cord.
There are some patients who cannot undergo an MRI examination. They are
those dependent upon cardiac pacemakers, those with metallic clips previously
placed to stop or prevent bleeding into the brain or those with metallic
foreign bodies in or around the eyes.
Because
MRI uses no ionizing radiation and presents no apparent risk to patients,
it is replacing more painful and risky examinations.
In children, it is being used to look for congenital or post surgical
changes in the spinal cord as well as tumors of the spinal cord and brain.
In adults, it rapidly displays degenerative disease of the spinal disks.
In the past, these patients could be studied only by myelography, a painful
procedure which requires an injection of dye into the spine. The dye causes
terrible headaches and a hospital stay of at least 24 hours.
In its few years in clinical use, MRI has proven a valuable addition to
previously available imaging techniques.
|
