Doppler effect

1. Cairo University
Faculty of Engineering
System and Bio-Medical department
Report on "Doppler Effect"
Prepared by: Aya Mustafa Alnahas
1st year Bio-Medical
Section 1
Under the supervision of: Dr. Mohamed Hesham
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2. Index
Introduction to Doppler ultrasound
Page 3
Doppler ultrasound diagnoses
Page 3
Doppler ultrasound procedure
Page 4
Doppler ultrasound benefits
Page 4
Mechanism of Doppler ultrasound
Page 4 - 5
The three basic types of Doppler
Page 5
ultrasound
Why Doppler ultrasound is done ?
Page 6
Application of ultrasound
Page 7
References
Page 8
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3. Introduction to the Doppler Effect
When most people hear the term "Doppler effect," they think of how
many meteorologists use Doppler to predict weather patterns. However,
Doppler can also be used for medical diagnosis in the form of a Doppler
ultrasound. In a normal ultrasound, a technician applies a
gel that acts as a conductor for sound waves to the
patient's skin. A transducer is moved over the area being
tested and sound waves are used to create pictures of
organs and other tissues. The Doppler effect is used to
measure the "change in sound waves reflected by a moving
object" (Mayo Clinic), so it can be used
Doppler Ultrasound Diagnoses
Because Doppler is used to measure changes in sound waves, it is used to
diagnose conditions related to circulation and blood flow. The Doppler ultrasound
can actually measure how fast or slow blood is moving, which can indicate a
circulatory problem. Blood clots can be found using Doppler ultrasound because
the ultrasound will be able to detect slower blood flow or a lack of blood flow
where the clot is located. Doppler ultrasound can also be used to identify
narrowed arteries, plaque buildup in the blood vessels, or blocked arteries. Found
early, many of these conditions can be treated before they become more serious.
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4. Doppler Ultrasound Procedure
The Doppler ultrasound may be done on the neck or on the extremities of
the body, depending on what symptoms the patient is experiencing. This
test is performed exactly like a regular ultrasound. The technician applies gel
to the area being tested, a transducer is moved over the gelled area, and the
ultrasound machine interprets the sound waves and creates pictures of
what is happening inside the body.
Doppler Ultrasound Benefits
The main benefit of Doppler ultrasound is that it is less invasive than other
procedures used to identify these types of medical problems. The
ultrasound is perform on the outside of the body and is not painful. Some
discomfort may be experienced as the transducer is used, but it is often
minimal. Because the ultrasound is not invasive, there are fewer risks to
using it as a diagnostic test and many patients are able to have serious
conditions detected without having to spend extensive time in the hospital.
Mechanism Of Doppler Ultrasound
During 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. See a picture of a Doppler ultrasound .
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5. Figure 1 shows a color Doppler ultrasound picture of blood flowing through a normal artery (red) and vein
(blue). Figure 2 shows an ultrasound picture of an artery narrowed by the buildup of calcium and fat
(cholesterol) in the inner lining of the artery, called plaque, which leads to "hardening of the arteries"
(atherosclerosis).
The three basic types of Doppler ultrasound are:
"Bedside" or continuous wave Doppler. This type 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 the bedside in the hospital with a portable machine to
provide a fast 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 the surrounding organs. Also,
a computer converts the Doppler sounds into a graph that gives 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. Also, 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 is a
special type of color Doppler. Power Doppler can get
some images that are hard or impossible to get using
standard color Doppler. Power Doppler is most
commonly used to evaluate blood flow through vessels within solid organs.
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6. Why It Is Done ???
Doppler ultrasound is done to:
1) Find blood clots and blocked or narrowed blood vessels in almost any part of the body,
especially in the neck, arms, and legs.
2) Evaluate leg pain that may be caused by
intermittent claudication, a condition caused by
atherosclerosis of the lower extremities.
3) Evaluate blood flow after a stroke or other
condition that might be caused by a problem with
blood flow. Evaluation of a stroke can be done through a technique called transcranial
Doppler (TCD) ultrasound.
4) Evaluate abnormal veins causing varicose veins or other problems.
5) Map veins that may be used for blood vessel grafts. It also can
check the condition of grafts used to bypass blockage in an arm or
leg.
6) Find out the amount of blood flow to a transplanted kidney or
liver.
7) Monitor the flow of blood following blood vessel surgery.
8) Find out the presence, amount, and location of arterial plaque.
Plaque in the carotid arteries can reduce blood flow to the brain
and may increase the risk of str oke.
9) Guide treatment such as laser or radiofrequency ablation of
abnormal veins.
10) Check the health of a fetus. Blood flow in the umbilical cord,
through the placenta, or in the heart and brain of the fetus may be
checked. This test can show if the fetus is getting enough oxygen and nutrients. Doppler
ultrasound may be used to guide decisions during pregnancy when:
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7. .
Applications of Doppler Effect
The Doppler effect provides a convenient means of
tracking a satellite that is emitting a radio signal of
constant frequency. The frequency of the signal
received on the Earth changes as the satellite is
passing. If the received signal is combined with a
constant signal generated in the receiver to give rise
to beats, then the beat can have a frequency that
produces an audible note, whose pitch decreases as
the satellite passes overhead.
The traffic police use a technique based on Doppler principle to detect over
speeding of vehicles on highways. An
electromagnetic wave is emitted by a
source at the side of the road attached
to a police car. The wave is reflected by a
moving vehicle, which thus, acts as a
moving source. The reflected wave will
have a Doppler shift in frequency.
Measurement of the frequency shift
using the phenomenon of beats, permits
the measurement of the speed of the vehicle.
The Doppler effect for light is important in
astronomy. Two stars which revolve around
one another are called double stars or
spectroscopic binaries. When one is
approaching the Earth, the other will be
receding and this causes a split in the spectral
lines, due to change in the frequency of the
light emitted. The phenomenon of red shift in the light from stars helps in
understanding the theory of expanding universe.
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8. Researches
http://www.tutorvista.com/content/physics/physics-iii/waves/doppler-effectapplications.php
http://en.wikipedia.org/wiki/Doppler_radar
http://www.qrg.northwestern.edu/projects/vss/docs/communications/3-whatis-the-doppler-effect.html
http://www.mayoclinic.org/doppler-ultrasound/expert-answers/faq-20058452
https://www.google.com.eg/search?q=doppler&source=lnms&tbm=isch&sa=X&
ei=FWj9UpvTK46ThgeszoHACw&ved=0CAcQ_AUoAQ&biw=1241&bih=567#facrc
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