Bma Illustrated Medical Dictionary

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 pregnancy, but often at

18–20 weeks. The age, size, and growth

rate of the fetus can be determined;

multiple pregnancies detected; and

certain problems, such as neural tube

defects, diagnosed. Scans may be taken

early in pregnancy if problems, such as

an ectopic pregnancy, are suspected.

Ultrasound scanning can also be used

in newborn babies to examine the brain

through a gap in the skull (for example,

to investigate hydrocephalus). Ultra-

sound can help to diagnose disorders

such as cirrhosis, gallstones, hydroneph-

rosis, and pancreatitis, as well as

problems in the thyroid gland, breasts,

bladder, testes, ovaries, spleen, and

eyes. The technique is also used during

needle biopsyto help guide the needle.

Doppler ultrasound is a modified form

of ultrasound that uses the Doppler

effectto investigate moving objects.

This can be used to examine the fetal

heartbeat and to obtain information

about the rate of blood flow in vessels.

ultrasound treatmentThe use of ultra-

soundto 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 lightInvisible 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 ozone

layer. The ultraviolet light (mainly UVA)

that reaches the earth’s surface causes

the tanning effects of sunlight and the

production of vitamin Din the skin. It

can have harmful effects, such as skin

cancer (see sunlight, adverse effects of).

Ultraviolet light is sometimes used in

phototherapy. A mercury-vapour lamp

(Wood’s light) can also produce ultravi-

olet light. This is used to diagnose skin

conditions such as tineabecause it

causes the infected area to fluoresce.

umbilical cordThe ropelike structure

connecting the fetusto the placentathat

supplies the fetus with oxygen and

nutrients from the mother’s circulation.

The umbilical cord is usually 40–60 cm

long and contains 2 arteries and a vein.

umbilical herniaA soft swelling at the

umbilicusdue to protrusion of the ab-

dominal contents

through a weak area

of abdominal wall.

Umbilical hernias

are quite common

in newborn babies

and occur twice

as often in boys as

in girls. The swel-

ling increases in

size when the baby

cries, and it may

cause discomfort.

Umbilical hernias

usually disappear

without treatment

by age 2. If a her-

nia is still present

at age 4, surgery

may be needed.

ULTRASOUND TREATMENT UMBILICAL HERNIA

U

ULTRASOUND SCANNING

Radiographer

ULTRASOUND SCANNING IN PREGNANCY

Gel

Monitor

Ultrasound

transducer