INTRODUCTION TO ULTRASOUND
What is Ultrasound?
Fundamental Principles, Sound Wave Physics and Medical Imaging Applications
Ultrasound →
Ultrasound is a medical imaging technique that uses
high-frequency sound waves
(typically above 20,000 Hz and usually 2–20 MHz in diagnostic imaging)
to create real-time images of organs, tissues, blood vessels,
and other structures inside the body.
Infrasound
< 20 Hz
Human Audible Range
20 Hz – 20,000 Hz
Ultrasound
> 20,000 Hz
20 Hz
20,000 Hz
WAVE FORM (Pressure vs Time)
+
−
0
Pressure
Time ➜
Compression
Compression
Compression
Rarefaction
Rarefaction
Wavelength (Ξ»)
Compression →
Compression is the phase of a sound wave in which particles are
squeezed closer together, producing a region of
high pressure.
Compression = particles are closer together
→ High pressure
→ Higher particle density
→ Followed by rarefaction
Compression = particles are closer together
→ High pressure
→ Higher particle density
→ Followed by rarefaction
P =
F
A
P =
F /
A
F
190
N
A
1.25
m²
F
190 N
A
1.25 m²
Rarefaction →
Rarefaction is the phase of a sound wave in which particles of the medium move
away from each other, resulting in a region of
decreased pressure and decreased density.
Rarefaction = particles are spread apart
→ Low pressure
→ Lower particle density
→ Negative pressure phase
→ Followed by compression
Rarefaction = particles are spread apart
→ Low pressure
→ Lower particle density
→ Negative pressure phase
→ Followed by compression
Sound Formation →
Formation of sound is the process by which sound is produced when an object
vibrates and causes the particles of a surrounding medium
(such as air, water, or a solid) to vibrate. These vibrations travel through
the medium as sound waves and can be heard when they reach
the ear.
Example: When a guitar string is plucked, it vibrates and produces sound waves that travel through the air to our ears.
Example: When a guitar string is plucked, it vibrates and produces sound waves that travel through the air to our ears.
πΈ A2
WHAT IS ULTRASOUND?
✎ Best Study Notes • MCQ Practice
Quick study →
Ultrasound uses high-frequency sound waves
to produce images of structures inside the body.
01. What is ultrasound?
02. What type of wave is used in diagnostic ultrasound?
03. Ultrasound waves require what to travel?
04. Ultrasound is generally defined as sound above:
05. Which device produces and receives ultrasound?
06. How are ultrasound images mainly produced?
07. Which effect is used in an ultrasound transducer?
08. What happens when ultrasound reaches a tissue boundary?
09. Which mode commonly displays a real-time anatomical image?
10. Why is diagnostic ultrasound widely used?
✎ REMEMBER
Ultrasound = high-frequency mechanical sound waves.
It needs a medium to travel and diagnostic ultrasound
does not use ionizing radiation.
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