| Ultrasound - Vascular
What is Vascular Ultrasound? Back to Top
Ultrasound or
sonography involves the sending of sound waves through the body. Those
sound waves are reflected off the internal organs. The reflections are
then interpreted by special instruments that subsequently create an
image of anatomic parts. No ionizing radiation (x-ray) is involved in
ultrasound imaging.
An ultrasound image is a useful way of evaluating the body's
circulatory system. Ultrasound images are captured in real-time, so
they can help radiologists monitor the blood flow to organs and tissues
throughout the body, as well as evaluate the placement and success of
repair, such as after arterial bypass surgery. With ultrasound images,
radiologists can locate and identify blockages (stenosis) and
abnormalities like blood clots, plaque or emboli and help plan for
their effective treatment.
What are some common uses of the procedure? Back to Top
Ultrasound
imaging of the body's veins and arteries can help the radiologist see
and evaluate blockages to blood flow, such as clots in veins and plaque
in arteries. With knowledge about the arterial blood flow gained from
an ultrasound image, the radiologist can often determine whether a
patient is a good candidate for a procedure like angioplasty.
Ultrasound images may also be used to plan or review the success of
procedures that graft or bypass blood vessels—such as renal (relating
to the kidney) artery bypass. Ultrasound of the veins may reveal blood
clots that require treatment, such as anticoagulant therapy (blood
thinner), or filters to prevent clots from traveling to the lungs
(embolism).
Ultrasound of the vascular system also provides a fast, noninvasive
means of identifying blockages of blood flow in the neck arteries to
the brain that might produce a stroke or mini-stroke.
How should I prepare for the procedure? Back to Top
You
should wear comfortable, loose-fitting clothing for your ultrasound
exam. No other preparation is required. If your abdominal vessels are
being studied, you will need to fast before the procedure.
What does the equipment look like? Back to Top
The equipment
consists of a transducer and a monitoring system. The transducer is a
small hand-held device that resembles a microphone. The radiologist or
sonographer spreads a lubricating gel on the area being examined and
then presses this device firmly against the skin.
The transducer passes the image to the ultrasound machine and from
there to a viewing monitor. The radiologist or technologist watches
this screen during an examination and captures representative images
for storage. Often, the patient is able to see it as well. Blood flow
also produces sound that can be heard with Doppler ultrasound. You may
also hear the sounds.
An example of the ultrasound equipment that may be used is shown at the top of this page.
How does the procedure work? Back to Top
Ultrasound imaging
is based on the same principles involved in the sonar used by bats,
ships at sea, and anglers with fish detectors. As a controlled sound
bounces against objects, its echoing waves can be used to identify how
far away the object is, how large it is, its shape and its internal
consistency (fluid, solid or mixed).
The ultrasound transducer functions as both a loudspeaker (to create
the sounds) and a microphone (to record them). When the transducer is
pressed against the skin, it directs a stream of inaudible,
high-frequency sound waves into the body. As the sound waves echo from
the body's fluids and tissues, the sensitive microphone in the
transducer records tiny changes in the sound's pitch and direction.
These signature waves 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 can be recorded on videotape. In
addition, still frames of the moving picture are usually "frozen" to
capture a series of images. Blood flow changes the pitch of the sound
beam; this Doppler effect can be heard or detected on the image as
color or displayed graphically.
How is the procedure performed? Back to Top
The patient is positioned on an examination table that can tilt and move.
A clear gel is applied to the area that will be examined. The gel
helps the transducer make a secure contact and eliminates air pockets
between the transducer and the skin, since the sound waves cannot
penetrate air. The sonographer, vascular technologist or radiologist
then presses the transducer firmly against the skin and sweeps along
the area of interest, reviewing the images on the monitor and capturing
"snapshots" as required. For venous ultrasound examinations, the
transducer is pressed gently on the leg.
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 monitor. Often, though, the sonographer or radiologist is able to
review the ultrasound images in real time as they are acquired, and the
patient can be released immediately.
What will I experience during the procedure? Back to Top
Most
ultrasound studies are fast and easy. You will lie on your back on an
examining table that may be tilted or moved to provide access to the
area that will be imaged. The sonographer or radiologist will spread
some gel on your skin and then press the transducer firmly against your
body, moving it until the desired images are captured. Most exams take
less than 30 minutes; however, more complicated examinations may take
somewhat longer.
Who interprets the results and how do I get them? Back to Top
A
radiologist, who is a physician experienced in ultrasound and other
radiology examinations, will analyze the images and send a report to
your personal physician. Generally, you will receive results of the
examination from your physician. Currently, new technology such as PACS
(picture archiving andl communication systems) may enable your
physician to review the images and retrieve the report over the
Internet at many facilities.
What are the benefits vs. risks? Back to Top
Benefits
- Ultrasound scanning is noninvasive (no needles or injections) and usually painless.
- Ultrasound is widely available and easy to use.
- Ultrasound uses no ionizing radiation.
- Ultrasound images can demonstrate structure, movement and function in the body's blood vessels in real time.
Risks
- For standard diagnostic ultrasound, there are no known harmful effects on humans.
What are the limitations of Vascular Ultrasound? Back to Top
Vessels deep in the body are harder to see than superficial vessels. Specialized equipment may be necessary.
Calcifications that occur as a result of atherosclerosis may obstruct the ultrasound beam.
Sometimes
ultrasound cannot differentiate between a blood vessel that is closed
or very nearly closed because the weak volume of blood flow produces a
weak signal. Back to Top |
