This ppt describes basic principles of Ultra Sound Imaging. Advantages, Applications, limitations and modes of operations are also included.

1. ULTRA SOUND IMAGING
Prepared by : Abhijith Prabha ,
L6A ,roll no : 6 ,
ECE Department , SNGCE.
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2. INTRODUCTION
 An ultrasound imaging device is a machine that is
commonly used to examine underlying features of the
human body.
 Its advantages are that no surgery is needed in order to
obtain a clear picture of entities such as kidney stones.
 The main parts of an ultrasound equipment are the
ultrasound transducer or probe, the electrical control of
the probe (including "beam former") and the visualization
system. This section will focus particularly on the
visualization system.
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3. Principle
 The ultrasound machine transmits high-frequency (1 to 5
megahertz) sound pulses into your body using a probe.
 The sound waves travel into your body and hit a boundary
between tissues (e.g. between fluid and soft tissue, soft
tissue and bone).
 Some of the sound waves get reflect back to the probe,
while some travel on further until they reach another
boundary and get reflected.
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4. Fig : schematic diagram of principle of Ultra Sound imaging
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5. Principle
 The reflected waves are picked up by the probe and
relayed to the machine.
 The machine calculates the distance from the probe to
the tissue or organ (boundaries) using the speed of
sound in tissue (5,005 ft/s or1,540 m/s) and the time of
the each echo's return (usually on the order of millionths
of a second).
 The machine displays the distances and intensities of the
echoes on the screen, forming a two dimensional image
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6. Relation between attenuation and frequency in body.
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7. Attenuation coefficient of different body
tissues
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8. Ultra Sound Machine
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9. The Ultrasound Machine
 A basic ultrasound machine has the following
parts:
 transducer probe - probe that sends and receives the sound waves
 central processing unit (CPU) - computer that does all of the
calculations and contains the electrical power supplies for itself and
the transducer probe
 transducer pulse controls - changes the amplitude, frequency and
duration of the pulses emitted from the transducer probe
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10.  display - displays the image from the ultrasound
data processed by the CPU
 keyboard/cursor - inputs data and takes
measurements from the display
 disk storage device (hard, floppy, CD) - stores
the acquired images
 printer - prints the image from the displayed data
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11. Fig : working of Ultrasonic Machine
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12. Ultrasound generator
.
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13. Fig: block diagram of Ultra Sound generator
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14. Ultrasound receiver
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15. Fig : ckt diagram of a typical Ultrasound
Receiver
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16. Modes of operation
A MODE
A stands for Amplitude. Information of the reflected
signal in a single ultrasound beam is continually
displayed distance from the transducer and intensity are
shown by position and amplitude in a line on an
oscilloscope. This mode is mainly of historical interest,
may be rarely used in gynaecology or ophthalmology.
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17. Modes of operation
B MODE
B stands for Brightness. In this case A-mode
information from many beams, typically forming a sector
in a plane of the body, is shown as pixel intensity on a
monitor. B mode is often referred to as 2D, and is the
most important modality for anatomic assessment and
orientation in the body, also for localising and as a
background for display of other information such as
Doppler signals.
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19. Modes of operation
M MODE
M stands for motion. This approach is used for the
analysis of moving organs. It is based on A-mode data
from a single ultrasound beam that are represented as
function of time. This does not require a sweep through
many ultrasound beams which allows for high temporal
resolution.
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20. Fig : illustration of Ultrasound image in Mode M
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21. Modes of operation
Doppler mode
 Doppler mode exploits the frequency shift due to relative
motion between two objects. With this approach
information regarding blood velocity and cardiac valves
can be obtained.
 Doppler mode can be obtained by continuous or pulsed
wave (PW); in addition, velocity data can be shown as
overlaying colour on B-mode images (colour
Doppler, power Doppler and Tissue Doppler).
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22. Transducers
 Mechanical Probe: seldom used now.
 Electronic Probe:
– Linear array transducers
• piezoelectric elements linearly arranged
• sequentially activated to produce an image
– Phased array transducers
• smaller scanning surface (foot print)
• good for echocardiography
• more expensive
• elements are activated with phase differences to
allow steering of the ultrasound signal
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23. Applications
 Obstetrics and Gynaecology
 measuring the size of the foetus to determine the due
date
 determining the position of the foetus to see if it is in the
normal head down position or breech
 checking the position of the placenta to see if it is
improperly developing over the opening to the uterus
(cervix)
 seeing the number of foetuses in the uterus
 checking the sex of the baby (if the genital area can be
clearly seen)
 checking the foetus's growth rate by making many
measurements over time
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24. Applications
 Cardiology
 seeing the inside of the heart to identify abnormal
structures or functions
 measuring blood flow through the heart and major
blood vessels
 Urology
 measuring blood flow through the kidney
 seeing kidney stones
 detecting prostate cancer early
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25. Advantages
 Ultrasonic can be easily focused, i.e., they are
directional.
 They are inaudible.
 It is possible to investigate the properties of very
small structures.
 Information obtained by US , particularly in
dynamic studies, cannot be acquired by other
more convenient technique.
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26. Limitations
 development of heat - tissues or water absorb the
ultrasound energy which increases their temperature
locally
 formation of bubbles (cavitations) - when dissolved
gases come out of solution due to local heat caused by
ultrasound
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27. END
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