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.

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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.

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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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