PERFORMING A CT SCAN
CT scanning combines the use of a
computer and X-rays emitted by a
rotating machine to produce cross-
sectional images. Before the scan is
carried out, a contrast medium may be
injected to make blood vessels, organs,
or abnormalities show up more clearly;
for scans of the intestines, a drink of
contrast medium may be given to
highlight loops of intestine.
The scanner rotates around the patient. As
it does so, it sends a great number ofX-ray
beams, each of low dosage and lasting only a
fraction ofa second, through the patient’s body
at different angles.
The patient lies on a table that can be
moved up or down to allow easy transfer
and accurate positioning within the machine.
The table then slides the patient into the centre
A c e n t r a l s l i d i n g c r a d l e
in t h e t a b l e m o v e s t h e
p a t i e n t , a t a c o n t r o l l a b l e
r a t e , in t o t h e m a c h i n e
T h e m a c h i n e c a n b e t i lt e d in a n y
d i r e c t i o n t o a l l o w p r e c i s e a r e a s
t o b e X -r a y e d
B r a in
t i s s u e
E a r
c a v it y
Detectors in the scanner record the amount
of X-rays absorbed by different tissues. This
information is sent to a computer, which converts
it into an image (such as the section through
the head, above) for a radiologist to interpret.
S k u l l
N a s a l
c a v it y
A body structure that consists of mus-
cle and tendon fibres and encircles a
A growth of bacteria or other m icroor-
artificially in the laboratory.
Microorganisms are collected from
the site of an infection and cultured in
order to produce adequate amounts so
that tests to identify them can be per-
formed. Cells from a fetus may be
cultured to diagnose disorders prena-
tally. Healthy cells may be cultured for
the study of chromosomes (see
Some types of tissue,
such as skin, may be cultured to pro-
duce larger amounts that can then be
used for grafting. Other tissues are cul-
tivated to provide a medium in w hich
viruses can be grown and identified in
the laboratory; viruses w ill only m ulti-
ply w ithin living cells.
An ancient procedure in w hich the
practitioner draws blood to the skin
surface by applying a heated vessel to
the skin. It produces an inflammatory
response thought to relieve
and musculoskeletal pains.
An extract from the bark and juices
of various trees that has been used for
centuries by South American Indians as
an arrow poison. Curare kills by pro-
compounds that are related to curare
are sometimes used to produce paraly-
sis during surgery.
The process of restoration to normal
health after an illness. The word “ cure”
usually means the disappearance of a
disease rather than simply a halt in its
progress. A treatment that ends an ill-
ness may also be called a cure.
The use of a surgical instrument called
to scrape abnormal tissue, or
samples for analysis, from the lining of
a body cavity or from the skin.
The scraping of a cavity or other dental
surface with a
(a narrow, spoon-
shaped instrument). Dental curettage is
one method used to remove the lining
of periodontal pockets and diseased tis-
sue from root surfaces in
This enables the healthy underlying tis-
sue to reattach itself to the root surface.
used for scraping away material or tis-
sue from an organ, cavity, or surface.
A type of
that occurs speci-
fically in people w ho
extensive skin burns.