ULTRASOUND SCANNING - a patient's guide
Dr David Hough - Radiologist, Auckland Radiology Group
What is it?
Ultrasound uses high frequency sound waves to obtain a
cross-sectional image of an organ or body part, in any desired plane.
Sound waves are emitted by a hand-held transducer, and the
reflections of these sound waves are detected in the same transducer
and converted into black and white images on a TV screen. Selected
images are frozen on the TV screen and filmed.
As ultrasound is a real-time examination, movement may be
observed, for example fetal heartbeats and limb movements during
obstetric scans. Doppler ultrasound measures an alteration of the
reflected sound frequency caused by flowing blood, and colour or
graphical images of blood flow may be obtained.
What is it used for?
Common scans include abdomen (including liver, gallbladder,
kidneys and other organs), pelvis, obstetric, vascular (e.g. aorta,
carotid arteries, leg veins), thyroid gland, and scrotum. Ultrasound
is also used for scanning some tendons and joints, for example
tendons of the knee or ankle, and the shoulder joint. It is also
sometimes used for examination of the extremities, for example
looking at lumps, and identifying small "foreign bodies", i.e.
splinters in the hands or feet.
Who can have ultrasound?
Anyone may undergo an ultrasound scan. There are no known harmful
effects from a diagnostic ultrasound scan.
Before the scan
Fasting is generally required for 4 hours prior to an abdominal or
gallbladder ultrasound scan, and pelvic scans or early pregnancy
scans require a full bladder. If you are having an obstetric scan and
wish to have a video recording of the scan, please remember to bring
along a blank videotape.
What happens during the scan?
The scan will be performed either by a sonographer or radiologist.
A sonographer is a radiographer who has undergone speciality training
in ultrasound scanning, and a radiologist is a specialist doctor with
higher training in ultrasound. The radiologist may wish to have a
second look at a scan performed by a sonographer; this additional
check does not mean that something is wrong.
You will need to expose the skin of the body part being scanned. A
clear gel is applied to the skin; this reduces friction and improves
the transmission of sound waves into the body. The transducer is a
small handheld device that is applied to the skin and moved into
different positions to obtain the desired scan images. There is no
pain or discomfort from the scan, other than having a full
In some gynaecological cases an internal or trans-vaginal scan
will be performed. This will be discussed with you prior to the scan.
The bladder is emptied prior to commencing the scan. A special
transducer with a new protective covering is placed into the vagina
for this scan, providing superior visualisation of pelvic organs.
After the scan
The films are examined by the radiologist, who then issues a
report to the referring doctor. The report is usually available the
same day, or immediately in urgent cases.
Pregnancy And Birth
Dr David Hough
- Radiologist, Auckland Radiology Group
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