X-RAYS, DENTAL
XYLOMETAZOLINE
X-RAY
Spine .
Lung
X-ray
machine
Adjustable
stand
Heart /
Diaphragm
CHEST X-RAY IMAGE
X-ray film in
cassette
CHEST X-RAY PROCEDURE
X-rays well and appear white on an X-
ray image. Soft tissues, such as muscle,
absorb less and appear grey.
Because X-rays can damage living
cells, especially those that are dividing
rapidly, high doses of radiation are used
for treating cancer (see
radiotherapy).
Hollow or fluid-filled parts of the body
often do not show up well on X-ray film
unless they first have a contrast med-
ium (a substance that is opaque to
X-rays) introduced into them. Contrast-
medium X-ray techniques are used to
image the gallbladder (see
cholecystogra-
phy
), bile ducts (see
cholangiography
),
the urinary tract (see
urography
),
the
gastrointestinal tract (see
barium X-ray
examinations),
blood vessels (see
angiog-
raphy; venography
), and the spinal cord
(see
myelography
).
X-rays can be used to obtain an image
of a “slice” through an organ or part of
the body by using a technique known as
tomography
. More detailed images of a
body slice are produced by combining
tomography with the capabilities of a
computer (see
CT scanning
).
Large doses of X-rays can be extremely
hazardous, and even small doses carry
some risk (see
radiation hazards
). Modern
X-ray film, equipment, and techniques
produce high-quality images with the
lowest possible radiation exposure to the
patient. The possibility of genetic dam-
age can be minimized by using a lead
shield to protect the patient's reproduc-
tive organs from X-rays. Radiographers
and radiologists wear a
film badge
to
monitor their exposure to radiation.
(See also
imaging techniques; radiogra-
phy; radiology.)
X-rays, dental See
dental X-rays.
xylitol A naturally occurring carbohydrate
that is only partially absorbed by the
body and is sometimes used as a sweet-
ener by people with diabetes. Xylitol
chewing gum has been shown to reduce
recurrent ear infections in some children.
Excess xylitol may lead to abdominal
discomfort and flatulence.
xylometazoline A
decongestant
drug
used in the form of a spray or drops to
relieve nasal congestion caused by a
common
cold, sinusitis
, or hay fever (see
rhinitis, allergic
). Xylometazoline is also
used as an ingredient of eye-drops in the
treatment of allergic
conjunctivitis
.
Excessive use of xylometazoline may
cause headache, palpitations, or drowsi-
ness. Long-term use of the drug may
cause nasal congestion to worsen when
treatment is stopped.
X
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