ULTRASONOGRAPHY , PROPERTIES OF ULTRASONOGRAPHY, PRINCIPLE , ADVANTAGES & DISADVANTAGES........................

1. ULTRASONOGRAPHYAnand Gurmaita

2. INTRODUCTION TO ULTRASOUND IMAGING
SOUND
Sound is a wave that is created by vibrating object and
propagated through a medium from one location to
another, via particle interaction.
Sound waves needs medium to travel.
Speed of sound wave in air is 343 m/s.
Sound waves cannot travel through vaccum.

3. The particles moves in the direction parallel to the
direction of the wave i.e. longitudinally.
The particles pushes its neighboring particles and
restore its original position at the end of the interaction.
COMPRESSION
=> The backward and forward motion of particles in the
direction of the wave creates region of high pressure with
in the medium , where the particle compressed together is
called compression.

6. Rarefaction
The backward and forward motion of particles in the
direction of the wave creates region of low pressure with
in the medium, where the particles are spread apart is
called Rarefaction.
Wavelength of sound wave
The wavelength of the sound is the distance between
two successive high pressure pulses or two successive
low pressure.

8. Soundwave is measured in Hertz(Hz).
The audible range of sound wave for human is 20Hz to
20000Hz.
Soundwave is also known as pressure wave.
Soundwave above 20000Hz is known as Ultrasound.

9. ULTRASOUND IMAGING
Ultrasound imaging is an imaging technology that uses
high frequency sound waves to characterize tissue.
History of ultrasound
Ultrasound was originally developed during World War-I
to track submarines as SONAR technology.(SOUND ,
NAVIGATING AND RANGING)

10. Ultrasound was medically used in 1950s for the first
time.

11. PROPERTIES OF ULTRASONIC WAVE
They have a high energy content.
They get reflected , refracted and absorbed as similar to the
properties of light.
They can be transmitted over large distance.
They produce intense heating effect when passes through a
substance.
Ultrasound relies on the properties of acoustic physics (
Compression/Rarefaction, reflection, impedance etc. ) to
localize and characterize different tissue type.

12. The speed of ultrasonic wave in the human tissue is
1540 m/s.
The frequency range is above 20000 Hz.
The frequency range used in ultrasound imaging is
2 MHz to 16 MHz .
They are attenuated through absorption and scattering.
( Attenuated = decreased in magnitude, amount or force)

13. ADVANTAGES OF ULTRASOUND
Ultrasound uses non-ionizing sound waves and has not
been associated with carcinogenesis. This is particularly
important for evaluation of fetal and gonadal tissue.
Ultrasound is easily available that CT or MRI.
Ultrasound examine is less expensive than CT or MRI.
There are only few contraindications to the use of
ultrasound in compare of MRI or CT.
Doppler evaluation of organs and blood vessel can be
done.

14. Real time imaging can be done. ( eg. Fetal heart rate )
There is no effect of metallic object in ultrasound as
compared to CT or MRI.
An ultrasound exam is easily be extended to cover
another organ system or evaluate the contralateral
extermities.

15. DISADVANTAGES OF ULTRASOUND
More training is required to operate ultrasound machine
efficiently.
Ultrasound is not capable of examine the bone or air as it has
high acoustical impendence.
The high frequency of ultrasound result in a potential risk of
thermal heating or mechanical injury to tissue at microscopic
level.
Ultrasound has its own set of artifacts , which can reduce image
quality.
Some ultrasound examine may be limited by abnormally large
body habitus.

16. PRINCIPLE OF ULTRASOUND
Ultrasound uses ultrasonic sound waves that are
produced and detected within an ultrasound transducer.
The physical concept underlying the transducer is the
piezoelectric effect.
Piezoelectric effect is the property of some material
( Piezoelectric material ) that causes them to change in
shape when an electricity is applied to them ( which
causes in vibration of piezoelectric material and produce
ultrasound.)

17. DETECTION OF ULTRASOUND WAVES
Ultrasound waves which return to the detector , either by
reflecting or scattering , causes the piezoelectric material
to vibrate , generating an electric signal that is converted
into image.

18. TRANSDUCER
Ultrasound transducer is a device which converts electric
energy into mechanical (sound) energy and back again,
based on piezoelectric effect and the electric signal to
image.
A ultrasound transducer contains a piece of piezoelectric
material between two electrodes

20. THE END