ULTRASOUND – PART 2

Hi friends!!!

In our previous blog we have
seen about Ultrasound – Technology and Probes. Please check out for the link
given below.

ULTRASOUND – PART 1

Today we are going to see
about Modes of ultrasound and artifacts in ultrasound imaging.

Let’s get into the topic
with a small introduction about ultrasound.

WHAT IS

ULTRASOUND?

Sound generally means what the human ear can hear. All
vibrations including sound waves have frequencies. Frequency means how often
something vibrates per second. So we can call frequency as vibrations per
second. The unit of frequency is Hertz. The human ear can hear frequencies
between 20 Hz to 20000 Hz. Any sound with a frequency above 20000 Hz is called as
Ultrasound. In medical field ultrasound machine uses high frequency sound waves
to produce images of the body.

WHAT ARE THE MODES OF

THE ULTRASOUND?

A – MODE (Amplitude mode): A single transducer scans a line through the body
with the echoes plotted on screen as a function of depth. It is used where
precise length and depth measurements are needed.

B – MODE (Brightness mode): It is a two-dimensional ultrasound image display
composed of bright dots representing the ultrasound echoes. The brightness of
each dot is determined by the amplitude of returned echo signal. It facilitates
the visualization and quantification of anatomical structures. It is the most
common type.

M – MODE (Motion mode): It is a time motion display of the ultrasound wave
along a chosen ultrasound line. All of the reflectors along the line are
displayed along time axis. Rapid motions can be recorded, displayed and
measured.

WHAT ARE THE

ARTIFACTS?

Artifacts lead to the improper display of the
structures to be imaged. Image can be too bright or too dark which can lead to
misinterpretation of underlying pathology.

The following are the most common artifacts in
ultrasound imaging.

REVERBERATION: Time delays due to travel of echoes when there are 2
or more parallel reflectors in the sound path. Here the ultrasound beam
reflects back and forth between the reflectors, the ultrasound interprets the
sound waves returning as deeper structures since it took longer for the wave to
return to the transducer.

Reverberation artifact can be improved by changing the
angle of exposure.

MIRROR IMAGE: When sound wave hits a highly reflective surface such
as diaphragm but instead of directly returning back to the transducer, sound
waves encounters a second reflector and then reflected back to the highly
reflective surface again, then returns back to the transducer. Thus the delayed
returning echoes are considered as if it is returned from a deeper structure,
hence giving a mirror artifact on the other side of the reflective surface.

ACOUSTIC SHADOWING: Some structures tend to reflect all the sound waves. So
the ultrasound beam does not pass through an object, leaving the area behind
the reflector unexplored. As a result, in ultrasound monitor there appears a
black area beyond the surface of the reflector.

REFRACTION: Refraction occurs when the sound wave reaches two
tissues of different acoustic impedances. Ultrasound beam reaching the second
tissue changes direction which may cause an organ to be improperly displayed.

 

Now I hope you have
acquired some knowledge about Ultrasound machine. We will discuss about topics
related to Biomedical Engineering, Medical Devices, Healthcare in our next
blog.

Please check out for the link below to gain knowledge about ENDOSCOPE.

ENDOSCOPE

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Biomedical, so that we can discuss it in future blogs.

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