Our GP is ready to help you if you want to be sure that you are healthy and in good shape, you have medical questions or problems and want to discuss with an experienced doctor, you have some unknown symptoms and want to know what they could be related to, you want to know another medical opinion about the best way of treatment of your disease.
A Doppler ultrasound test uses reflected
sound waves to evaluate blood as it flows through
a blood vessel. It helps evaluate blood flow through the major arteries
and veins of the arms, legs, and neck. It can show blocked or reduced blood
flow in the arteries of the neck that could cause a stroke. It can also reveal
blood clots in leg veins that could break loose and block blood flow to the
lungs (pulmonary embolism).
During duplex Doppler ultrasound, a handheld
instrument (transducer) is passed lightly over the skin above a blood vessel.
The transducer sends and receives sound waves that are amplified through a
microphone. The sound waves bounce off solid objects, including blood cells.
The movement of blood cells causes a change in pitch of the reflected sound
waves (called the Doppler effect). If there is no blood flow, the pitch does
not change. Information from the reflected sound waves can be processed by
a computer to provide graphs or pictures that represent the flow of blood
through the blood vessels. These graphs or pictures can be saved for future
review or evaluation.
There are four types of Doppler ultrasound:
“Bedside” or continuous
wave Doppler. This type
of Doppler ultrasound uses the change in pitch of the sound waves to provide
information about blood flow through a blood vessel. The doctor listens to
the sounds produced by the transducer to evaluate the blood flow through an area that
may be blocked or narrowed. This type of ultrasound can
be done at a person's bedside in the hospital to provide a rapid estimate
of the extent of blood vessel damage or disease.
Duplex Doppler. Duplex
Doppler ultrasound uses standard ultrasound methods to
produce a picture of a blood vessel and surrounding organs. In addition, a
computer converts the Doppler sounds into a graph that provides information
about the speed and direction of blood flow through the blood vessel being
evaluated.
Color Doppler. Color Doppler uses standard ultrasound
methods to produce a picture of a blood vessel. In addition, a computer converts
the Doppler sounds into colors that are overlaid on the image of the blood
vessel and that represent the speed and direction of blood flow through the
vessel.
Power Doppler. Power Doppler is a new ultrasound technique being developed
that is up to five times more sensitive than color Doppler. Power Doppler can
also obtain some /images that are difficult or impossible to obtain using standard
color Doppler. However, power Doppler is most commonly used to evaluate blood flow through
vessels within solid organs. Blood flow in individual blood vessels is most commonly evaluated
by duplex Doppler.
Doppler Ultrasound Results
Doppler ultrasound
Normal:
For continuous wave or duplex Doppler, the signals obtained are the same
for both sides of the neck or for both limbs. No blockage, aneurysm,
or narrowing of a blood vessel (stenosis) is detected. The rate of blood flow is similar
to standard values. These results indicate open blood vessels with normal
blood flow.
On a duplex Doppler ultrasound graph:
The normal
flow of blood through
a vein shows an up-and-down pattern that matches your breathing.
The normal flow of blood through
an artery shows a pattern that matches your heart rate.
For color Doppler,
the image indicating blood flow
is normal for both sides of the neck or for both limbs.
Abnormal:
For continuous wave Doppler, differences in blood flow between
the right and left sides of the body may be heard. At the exact location where
an artery is blocked or narrowed, the sound may be high-pitched or turbulent.
Blockage (such as from a blood clot), aneurysm, or narrowing of a
blood vessel may be detected. The rate of blood flow may be compared to standard
values to determine the amount of blockage or narrowing of the blood vessel.
A
duplex Doppler ultrasound graph may show irregular flow that
indicates a blocked or narrowed blood vessel.
A color Doppler image may show a
blocked or narrowed blood vessel
or an aneurysm.
In the veins, a blood clot may be indicated if blood flow does
not change in response to breathing or does not increase in response to an augmentation maneuver or
Valsalva's
maneuver. Incomplete blockage of a vein by a blood clot may be seen on color Doppler or during
a compression maneuver.
Medical online consultation with qualified doctors
Copyright © 2004-2005