Ultrasonic waves are emitted by a trans-
ducer, which is placed on the skin over
the part of the body to be viewed. The
transducer contains a crystal that con-
verts an electric current into sound waves.
These pass readily through soft tissues
and fluids, making this procedure useful
for examining fluid-filled or soft organs.
One of the most common uses of ultra-
sound is to view the uterus and fetus, at
any time during
but often at
18-20 weeks. The age, size, and growth
rate of the fetus can be determined;
certain problems, such as
diagnosed. Scans may be taken
early in pregnancy if problems, such as
, are suspected.
Ultrasound scanning can also be used
in newborn babies to examine the brain
through a gap in the skull (for example,
sound can help to diagnose disorders
problems in the thyroid gland, breasts,
bladder, testes, ovaries, spleen, and
eyes. The technique is also used during
to help guide the needle.
Doppler ultrasound is a modified form
of ultrasound that uses the
to investigate moving objects.
This can be used to examine the fetal
heartbeat and to obtain information
ultrasound treatment The use of
to treat soft-tissue injuries (such
as injuries to ligaments, muscles, and
tendons). Ultrasound treatment reduces
inflammation and speeds up healing. It
is thought to work by improving blood
flow in tissues under the skin.
ultraviolet light Invisible light from the
part of the electromagnetic spectrum
immediately beyond the violet end of
the visible light spectrum. Long wave-
length ultraviolet light is termed UVA,
intermediate UVB, and short UVC.
Ultraviolet light occurs in sunlight, but
much of it is absorbed by the
layer. The ultraviolet light (mainly UVA)
that reaches the earth's surface causes
the tanning effects of sunlight and the
in the skin. It
can have harmful effects, such as
sunlight, adverse effects
Ultraviolet light is sometimes used in
. A mercury-vapour lamp
(Wood's light) can also produce ultravi-
olet light. This is used to diagnose skin
conditions such as
causes the infected area to fluoresce.
umbilical cord The ropelike structure
supplies the fetus with oxygen and
nutrients from the mother's circulation.
The umbilical cord is usually 40-60 cm
long and contains
arteries and a vein.
umbilical hernia A soft swelling at the
protrusion of the ab-
through a weak area
of abdominal wall.
are quite common
in newborn babies
as often in boys as
in girls. The swel-
size when the baby
cries, and it may
by age 2. If a her-
nia is still present
at age 4, surgery
may be needed.
about the rate of blood flow in vessels.
ULTRASOUND SCANNING IN PREGNANCY