SOME DETAILS ABOUT THE DOPPLER ULTRASONOGRAPHY AND ITS TYPES IN DIAGNOSTIC RADIOLOGY

1. DOPPLER
ULTRASONOGRAPHY
MAAJID MOHI UD DIN MALIK
LECTURER COPMS ADESH UNIVERSITY
BATHINDA PUNJAB

2. DOPPLER ULTRASONOGRAPHY
Doppler ultrasonography is a non-invasive procedure that
uses detectable changes in high frequency sound waves (2-20
MHz), based on the Doppler effect, to create clear digital
images in real time. As a medical imagery method it is used
for diagnostics, during medical procedures or for pathology
research. It has been in medical use for several decades with
no or little report of long-term side effects.

3. Thus is characterized as harmless, painless, cost-effective and
generally widely available. It requires little or no prior
patients’ preparation or aftercare. Predominantly, it is used to
monitor the circulatory system by detecting direction, velocity
and turbulence of blood flow, in order to provide information
on possible blood clots, blocked vessels, cardiac or valve
insufficiency.

4. PHYSICAL PRINCIPLES
Doppler ultrasonography is based on two
basic principles:
1. Ultrasound principle
High-frequency sound wave aimed at a
target will be reflected back and detected.

5. DOPPLER PRINCIPLE
Effect of changes in the sound pitch
depending on the movement of the object in
relation to the detector (positive or negative
shift - the speed of sound in blood is 1570 m/s).

6. Piezoelectric crystals within the transducer or
probe produce electrical pulses when vibrated by
the returning wave (as with all ultrasonography
gel medium is used). The transducer will send
thousands of series of waves, which may be
continuous or pulsed. If pulsed then pauses for
detection of the returning waves are necessary.
Upon detection, ultrasonograph calculates and
determines the direction and depth of each
returning sound wave.

7. Thousands of such pulses sent and detected are
computed and displayed in order to produce an
image of the studied object, each detected wave
displayed as pixel on the screen. Use of color
helps in depicting direction and rate of blood
flow, assisting the physician interpreting the
results. It is important to note that there is no
standard on colors used for depiction of effect or
type of vessel, thus colors vary between
manufactures or operating modes.

8. TYPES
Color flow Doppler ultrasound
Continuous wave Doppler ultrasound
Duplex Doppler ultrasound

9. COLOR FLOW DOPPLER
ULTRASOUND
The use of color flow Doppler (CFD) or color
Doppler imaging (CDI) (or simply color
Doppler) sonography allows the visualization
of flow direction and velocity within a user
defined area. A region of interest is defined by
the sonographer, and the Doppler shifts of
returning ultrasound waves within are color-
coded based on average velocity and direction.

10. CLINICAL USE
Color flow Doppler is used frequently in sonography to
semi quantitate overall blood flow to a region of interest.
Depiction of the general velocity and direction of blood
flow within the heart and blood vessels is of primary
importance in echocardiography and vascular
ultrasound respectively. It also allows the generation of
unique phenomena such as the fluid color sign or
the twinkling artifact, and allows the targeting
of spectral Doppler for a quantitative assessment of
blood flow.

11. CONTINUOUS WAVE DOPPLER
ULTRASOUND
With continuous-wave Doppler ultrasound, the
emitting and receiving crystals function continuously
and display information representative of all moving
targets in the ultrasound beam. The continuous
mode has no limitation of recordable velocities and
therefore allows accurate measurement of high
velocities. The signal, however, is not gated (it
receives all underlying velocities); thus, spatial
localization of the abnormal velocities is lacking.

12. DUPLEX DOPPLER
ULTRASOUND
A duplex ultrasound is a test to see how blood
moves through your arteries and veins.

13. HOW THE TEST IS PERFORMED
A duplex ultrasound combines:
Traditional ultrasound: This uses sound
waves that bounce off blood vessels to create
pictures.
Doppler ultrasound: This records sound
waves reflecting off moving objects, such as
blood, to measure their speed and other
aspects of how they flow.

14. There are different types of duplex
ultrasound exams. Some include:
Arterial and venous duplex ultrasound of the
abdomen. This test examines blood vessels and
blood flow in the abdominal area.
Carotid duplex ultrasound looks at the carotid
artery in the neck.
Duplex ultrasound of the extremities looks at
the arms or legs.
Renal duplex ultrasound examines the kidneys
and their blood vessels.

15. PROCEDURE
You may need to wear a medical gown. You will lie
down on a table, and the ultrasound technician will
spread a gel over the area being tested. The gel helps
the sound waves get into your tissues.
A wand, called a transducer, is moved over the area
being tested. This wand sends out the sound waves.
A computer measures how the sound waves reflect
back, and changes the sound waves into pictures.
The Doppler creates a "swishing" sound, which is
the sound of your blood moving through the arteries
and veins.

16. You need to stay still during the exam. You may be
asked to lie in different body positions, or to take a
deep breath and hold it.
Sometimes during a duplex ultrasound of the legs,
the health care provider may calculate an ankle-
brachial index (ABI). You will need to wear blood
pressure cuffs on your arms and legs for this test.
The ABI number is obtained by dividing the blood
pressure in the ankle by the blood pressure in the
arm. A value of 0.9 or greater is normal.

17. A-MODE
A-mode is the simplest type of ultrasound. A
single transducer scans a line through the
body with the echoes plotted on screen as a
function of depth. Therapeutic ultrasound
aimed at a specific tumor or calculus is also A-
mode, to allow for pinpoint accurate focus of
the destructive wave energy.

18. B-MODE
In B-mode ultrasound, a linear array of
transducers simultaneously scans a plane
through the body that can be viewed as a two-
dimensional image on screen.

19. M-MODE
M stands for motion. In m-mode a rapid
sequence of B-mode scans whose images
follow each other in sequence on screen
enables doctors to see and measure range of
motion, as the organ boundaries that produce
reflections move relative to the probe.

20. THE NATURE OF ULTRASOUND
Ultrasonic waves are waves of frequency above
the audible frequencies the human ear. In
medical diagnostics are used ultrasound
frequencies between 1 and 20 MHz
The most important parameters describing the
wave are :
Wavelength
Frequency
Velocity
Intensity

21. The first three characteristics are linked
together by the formula:
 v = fl
v–Velocity of ultrasound (approximately
1540 m/s in the soft tissues),
f–Frequency in Hz
l–Wavelength in m

22. THE MAIN COMPONENTS OF
THE ULTRASONIC DEVICES
Ultrasound device, essentially, consists of a
transducer, transmitter pulse generator,
compensating amplifiers, the control unit for
focusing, digital processors and systems for
display.
It is used in cases of: abdominal, cardiac,
maternity, gynecological, urological,
cerebrovascular examination, breast
examination, and small pieces of tissue as well
as in pediatric and operational review.

23. THE INVERTER AND THE
ULTRASOUND BEAM
The inverter is a device that converts
electrical signals into mechanical (ultrasonic
vibrations), and vice versa. When activated
inverter is leaned on the body, it emits an
ultrasonic beam. Ultrasonic waves are focused
by lenses, ultrasonic mirrors and by electronic
means.

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