The patient lies inside a scanner sur-
rounded by a large, powerful magnet. A
receiving magnet is then placed around
the part of the body to be investigated.
If large areas, such as the abdomen, are
to be imaged, the receiving magnet is
fitted inside the scanner; for a smaller
area, such as a joint, a magnet may be
placed around the part to be scanned.
The scanner generates a strong mag-
netic field, which causes the atoms in
the body to line up parallel to each
other. Short pulses of radio waves from
a radiofrequency source briefly knock the
atoms out of alignment. As the atoms
realign they emit tiny signals, which are
detected by the receiving magnet. Infor-
mation about these signals is passed to
a computer, which builds up an image
based on the signals' strength and loca-
tion. MRI images can be enhanced by
use of a
tumours and blood vessels.
Images from MRI are similar to those
greater contrast between normal and
abnormal tissues. MRI is useful in
studying the brain and spinal cord, the
internal structure of the eye and ear, the
internal organs, and blood flow.
There are no known risks or side effects.
The technique does not use ionizing
radiation and can be performed repeat-
edly, but the scanner may interfere with
the functioning of pacemakers, hearing
aids, and other electrical devices.
The abbreviation for methicillin-
bacterium resistant to methicillin and
responsible for the emergence of infec-
tions in hospitals that are difficult to
treat and can sometimes be fatal.
The abbreviation for the disorder
for the food
The abbreviation for midstream
specimen of urine: a specimen of urine
to be examined for the presence of
microorganisms. The initial part of the
stream is not collected, in order to
avoid bacterial contamination of the
specimen from the skin or the lining of
the lower urinary tract.
A swollen sac or cavity within
the body that is filled with
secreted by its inner lining.
Drugs that make spu-
tum (phlegm) less sticky and easier to
cough up. An example is
emits pulses of radio waves
picks up signals
produced by body in
response to radio waves