Presented by: D.Sairam
Course : Bioanalytical and
Course Code: BSBT-202
Course Instructor: Dr.Subhabrata Kar
• Principle of Sonography
• Types of Sonography
Ultrasound scan is a medical test that uses high-frequency sound waves to
capture live images from the inside of your body. It is also called as
Sonography or Ultrasonography.
It uses high frequency sound waves to aid in the diagnosis and treatment of
patients. Ultrasound frequencies range from 2 to approximately 15 MHz
This technology is similar to that used by sonar and radar, which help the
military detect planes and ships.
Perhaps the most known application of this technique is associated with
Apart from this, Ultrasonography is also used for viewing bladder, eyes,
pancreas, liver, uterus etc.
Principle of Sonography
• The ultrasound beam originates from the transducer, which converts
electrical energy to sound waves.
• This ultrasound waves (pulses of sound) are sent from the
transducer, propagate through different tissues, and then return to
the transducer as reflected echoes.
• The returned echoes are converted back into electrical impulses by
the transducer and are further processed in order to form the
ultrasound image presented on the screen.
Components of Ultra Sonography
The following are the various components involved in
• Transducer Probe: It is the main components of the process.
It makes the sound waves and receives the echoes. In the probe,
there are one or more quartz crystals called Piezoelectric crystals.
• When an electric current is applied to these crystals, they change
shape rapidly by oscillating. The rapid shape changes, or vibrations,
of the crystals produce sound waves that travel outwards.
• Similarly, when sound or pressure waves hit the crystals, they emit
electrical currents. Therefore, the same crystals can be used to send
and receive sound waves.
• Central Processing Unit (CPU) : The CPU sends electrical currents to the transducer
probe to emit sound waves, and also receives the electrical pulses from the probes that
were created from the returning echoes.
• The CPU does all of the calculations involved in processing the data.
• After processing the data, the CPU forms the image on the monitor.
• The CPU can also store the processed data and/or image on disk.
• Transducer Pulse Controls: These controls allow the operator to set and change
the frequency and duration of the ultrasound pulses.
• The commands from the operator are translated into changing electric currents
that are applied to the piezoelectric crystals in the transducer probe.
• Disk Storage : The processed data and/ or images can be stored on disk. Generally, a
patient's ultrasound scans are stored on a floppy disk and archived with the patient's
Types of Sonography
• Doppler ultrasound is based upon the Doppler Effect.
• When the object reflecting the ultrasound waves is moving, it changes the frequency
of the echoes, creating a higher frequency if it is moving toward the probe and a
lower frequency if it is moving away from the probe.
• How much the frequency is changed depends upon how fast the object is moving.
Doppler ultrasound measures the change in frequency of the echoes to calculate how
fast an object is moving.
• Doppler ultrasound has been used mostly to measure the rate of blood flow through
the heart and major arteries.
• Blood clots and blood flow blockages may be identified with Doppler sonography in
Doppler ultrasound used to measure blood flow through
the heart. The direction of blood flow is shown in different
colours on the screen.
3-D Ultrasound Imaging
• In 3D foetal scanning, the sound waves are sent straight down and reflected back,
they are sent at different angles.
• The returning echoes are processed by a sophisticated computer program resulting in
a reconstructed three-dimensional volume image of the foetus's surface or internal
organs, in much the same way as a CT scan machine constructs a CT scan image from
• This is a more time taking process than 4-D Ultrasound Imaging where the output can
be accessed in real time.
• It was patented by two students from Duke University in 1987.
• There have been no real side effects noted to date but it is generally safer to avoid this
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