What is General Ultrasound
Ultrasound (US) imaging, also called ultrasound scanning or sonography,
is a method of "seeing" inside the human body through the use of high-frequency
sound waves. The sound waves are recorded and displayed as a real-time
visual image. No radiation is involved in ultrasound imaging.
US is a useful way of examining many of the bodyís internal organs, including
the heart, liver, gallbladder, spleen, pancreas, kidneys, and bladder. Because
US images are captured in real-time, they can show movement of
internal tissues and organs, and enable physicians to see blood flow and heart
valve functions. This can help to diagnose a variety of heart conditions and to
assess damage after a heart attack or other illness.
What are some common uses of
Millions of expectant parents have seen the first "picture" of
their unborn child with pelvic ultrasound examinations of the uterus and fetus.
Ultrasound imaging is used extensively for evaluating the eyes, pelvic and
abdominal organs, heart, and blood vessels, and can help a physician determine
the source of pain, swelling, or infection in many parts of the body. Because US
provides real time images, it can also be used to guide procedures such as
needle biopsies, in which a needle is used to sample cells from an organ for
laboratory testing. Ultrasound is now being used to image the breasts and to
guide biopsy of breast cancer.
Doppler ultrasound is a special technique used to examine blood flow. Doppler
images can help the physician to see and evaluate:
|blockages to blood flow, such as clots|
|build-up of plaque inside the vessel|
|congenital malformation |
How should I prepare for
You should wear comfortable, loose-fitting clothing for your US exam.
Other preparation depends on the type of examination you will have. For some
scans, your doctor may instruct you not to eat or drink for as many as 12 hours
before your appointment. For others, you may be asked to drink up to six glasses
of water two hours prior to your exam and avoid urinating, so that your bladder
is full when the scan begins.
What does the equipment look
Ultrasound scanners consist of a console containing a computer and
electronics, a video display screen and a transducer that is used to scan the
body. The transducer is a small hand
device about the size of a bar of soap, attached to the scanner by a cord. The
physician or technologist spreads a lubricating gel on the patientís abdomen
in the area being examined, and then presses the transducer firmly against the
skin to obtain images.
The US image is immediately visible on a nearby screen that looks much like a
computer or television monitor. The physician or technologist watches this
screen during an examination; often, the patient is able to see it as well.
How does US imaging work?
Ultrasound imaging is based on the same principles involved in the sonar used by
bats, ships at sea, and anglers with fish detectors. As the sound passes through
the body, echoes are produced that can be used to identify how far away an
object is, how large it is, and how uniform it is.
The ultrasound transducer functions as both a generator of sound (like a
speaker) and a detector (like a microphone). When the transducer is pressed
against the skin, it directs inaudible, high-frequency sound waves
into the body. As the sound echoes from the bodyís fluids and tissues, the
transducer records tiny changes in the pitch and direction of the sound. These
echoes are instantly measured and displayed by a computer, which in turn creates
a real-time picture on the monitor. The live images of the
examination are usually recorded on videotape, but one or more frames of the
moving picture may be "frozen" to capture a still image.
How is the procedure
The patient is usually positioned on an examination table. A clear gel is
applied to the patientís body in the area to be examined, to help the
transducer make secure contact with the skin. The sound waves produced by the
transducer cannot penetrate air, so the gel helps eliminate air pockets between
the transducer and the skin. The technologist or radiologist presses the
transducer firmly against the skin and sweeps it back and forth to image the
area of interest.
When the examination is complete, the patient may be asked to dress and wait
while the ultrasound images are reviewed, either on film or on a TV monitor.
Often, though, the technologist or radiologist is able to review the ultrasound
images in real time as they are acquired, and the patient can be released
What will I experience during the
Ultrasound imaging of the abdomen is painless, fast, and easy. You will
lie on your back on an examining table. The technologist or doctor will spread
some warm gel on your skin and then press the transducer firmly against your
body, moving it until the desired images are captured. There may be varying
degrees of discomfort from pressure as the technologist guides the transducer
over your abdomen, especially if you are required to have a full bladder. The
examination usually takes less than 30 minutes.
What are the benefits vs.
|Ultrasound imaging is a painless, low cost examination.|
|Ultrasound is widely available and easy to use.|
|US imaging uses no radiation, and is the preferred image modality
for diagnosis and monitoring of pregnant women and their unborn
|Ultrasound provides real-time imaging, making it a good
tool for guiding minimally invasive procedures such as needle
|US images can visualize movement and live function in the bodyís
organs and blood vessels.|
|Ultrasound scanning is painless and noninvasive.|
|For standard diagnostic ultrasound there are no known harmful
effects to humans.|
What are the limitations
of General Ultrasound Imaging?
Ultrasound waves do not reflect clearly from bone or air. For
visualization of bone, other imaging modalities should be selected.
Cardiac Ultrasound Images: