1. Volume I Companion Presentation Frank R. Miele Pegasus Lectures, Inc.
Ultrasound Physics & Instrumentation 4th Edition
Volume I
Companion Presentation
Frank R. Miele
Pegasus Lectures, Inc.
Pegasus Lectures, Inc.
COPYRIGHT 2006

2. License Agreement Pegasus Lectures, Inc. All Copyright Laws Apply.
This presentation is the sole property of
Pegasus Lectures, Inc.
No part of this presentation may be copied or used for any purpose other than as part of the partnership program as described in the license agreement. Materials within this presentation may not be used in any part or form outside of the partnership program. Failure to follow the license agreement is a violation of Federal Copyright Law.
All Copyright Laws Apply.
Pegasus Lectures, Inc.
COPYRIGHT 2006

3. Volume I Outline Pegasus Lectures, Inc. Chapter 1: Mathematics
Chapter 2: Waves
Level 1
Level 2
Chapter 3: Attenuation
Chapter 4: Pulsed Wave
Chapter 5: Transducers
Chapter 6: System Operation
Pegasus Lectures, Inc.
COPYRIGHT 2006

4. Chapter 2: Waves - Level 2
Pegasus Lectures, Inc.
COPYRIGHT 2006

5. Classification of Sound
Notice how the same data is presented on both a linear and a logarithmic scale. Because of the large dynamic range, notice that the logarithmic scale is a more “useful” way of presenting the data.
Fig. 26: Linear and Logarithmic Scale (Pg 112)
Pegasus Lectures, Inc.
COPYRIGHT 2006

6. Sound Ranges Pegasus Lectures, Inc. Note that: “infra” means below
0.02
0.2 20
20 K
20 M 2
200
2 K
200 K
2 M
Infrasound
Note that:
“infra” means below
“ultra” means above
“audible” refers to human hearing
Audible Range
Ultrasound
Diagnostic Ultrasound
Pegasus Lectures, Inc.
COPYRIGHT 2006

7. Typical Ultrasound Periods
The frequency and the period give the same information.
You should be able to convert back and forth between the period and the frequency.
Frequency = 2 MHz  Period = 1/(2 MHz) = 0.5 sec
Frequency = 10 MHz  Period = 1/(10 MHz) = 0.1  sec
Pegasus Lectures, Inc.
COPYRIGHT 2006

8. Diagnostic Ultrasound and Higher Frequencies
Fig. 27: Intravascular Ultrasound (IVUS) Image of a Coronary Artery (Pg 113)
Pegasus Lectures, Inc.
COPYRIGHT 2006

9. Propagation Velocity (c)
In Level 1, we discussed the fact that sound was determined strictly by the properties of the medium. It is now important to discuss which properties of the medium affect the propagation velocity and how.
The propagation velocity is related to the square root of the bulk modulus of the medium.
The propagation velocity is inversely related to the density of the medium.
Pegasus Lectures, Inc.
COPYRIGHT 2006

10. Fig. 28: Changing Volume with Pressure (Pg115)
Bulk Modulus
Fig. 28: Changing Volume with Pressure (Pg115)
Pegasus Lectures, Inc.
COPYRIGHT 2006

11. Bulk Modulus and Stiffness
High Bulk Modulus results when the material is stiff (incompressible or inelastic). Therefore, materials that are stiff tend to have high propagation speeds.
Propagation Speed (c) is related to stiffness.
(stiffer mediums have higher propagation speeds)
Pegasus Lectures, Inc.
COPYRIGHT 2006

12. Propagation Velocity Analogy
Fig. 29: (Pg 116)
Pegasus Lectures, Inc.
COPYRIGHT 2006

13. Stiffness and Propagation Velocity
Slower Wave Propagation
(More Compressible)
Faster Wave Propagation
(Stiffer)
Fig. 30: (Pg 117)
Pegasus Lectures, Inc.
COPYRIGHT 2006

14. Compressibility and Propagation Velocity (Animation)
(Pg. 118 A)
Pegasus Lectures, Inc.
COPYRIGHT 2006

15. Density and Propagation Velocity
Slower Wave Propagation
(Higher Density)
Faster Wave Propagation
(Lower Density)
Fig. 31: (Pg 117)
Pegasus Lectures, Inc.
COPYRIGHT 2006

16. Density and Propagation Velocity (Animation)
(Pg. 118 B)
Pegasus Lectures, Inc.
COPYRIGHT 2006

17. Wave Velocity versus Train Velocity
Fig. 32: (Pg 118)
Notice that the “wave” moves 30 m in the time that the train only moved 3 m.
(See animation of next slide)
Pegasus Lectures, Inc.
COPYRIGHT 2006

18. Wave vs. Train Velocity (Animation)
(Pg. 118 C)
Pegasus Lectures, Inc.
COPYRIGHT 2006

19. Don’t Oversimplify Pegasus Lectures, Inc.
At first glance, it appears that higher density materials would have lower propagation velocities because of the inverse relationship.
This contradicts what we see in reality in the body.
The reason is that the bulk modulus is generally higher for more dense materials (it is harder to compress a dense material than a less dense material).
A higher bulk modulus results in a higher propagation velocity.
Therefore, more dense materials in the body tend to have higher not lower propagation velocities.
This last fact becomes apparent by looking at the table of propagation velocities.
Pegasus Lectures, Inc.
COPYRIGHT 2006

20. Propagation Velocities in the Body
Medium
Propagation Velocity
Air (25 degrees C)
347 m/sec
Lung
500 m/sec
Fat
1440 m/sec
Water (25 degrees C)
1495 m/sec
Brain
1510 m/sec
“Soft Tissue”
Average 1540 m/sec
Liver
1560 m/sec
Kidney
Blood
Muscle
1570 m/sec
Bone
4080 m/sec
Table 5: (Pg 121)
Pegasus Lectures, Inc.
COPYRIGHT 2006

21. Propagation Speed (c) Summary
The propagation speed of sound is determined by two properties of the medium:
density ()
(Bulk Modulus) stiffness
As the density increases, the propagation speed decreases.
(assumes no change in stiffness – which is not very realistic)
As the stiffness increases the propagation speed increases.
Important point: For most materials, as the density increases, the stiffness increases much faster. This non-linear relationship results in more dense materials typically having much higher propagation velocities.
Pegasus Lectures, Inc.
COPYRIGHT 2006

22. Density, Stiffness and Propagation Velocity (Animation)
(Pg. 119)
Pegasus Lectures, Inc.
COPYRIGHT 2006

23. Calculating the Wavelength
You must be able to calculate the wavelength. (Pages )
Example: If the transmit frequency is 5 MHz, what is the wavelength in water?
Pegasus Lectures, Inc.
COPYRIGHT 2006

24. Power Pegasus Lectures, Inc.
Power is a measure of how much work or energy is expended per time.
Power has units of Watts.
So what happens to the power if you double the transmit voltage (amplitude)?
Pegasus Lectures, Inc.
COPYRIGHT 2006

25. Intensity Pegasus Lectures, Inc.
The intensity is the distribution of power over area.
So what happens to the intensity if you double the transmit voltage (amplitude)?
Intensity has units of Watts per area:
Pegasus Lectures, Inc.
COPYRIGHT 2006

26. Relationship of intensity with Amplitude
So if the amplitude is doubled, the power increases by a factor of four, resulting in an increase in intensity by a factor of four.
Recall that voltage is a measure of amplitude.
Pegasus Lectures, Inc.
COPYRIGHT 2006

27. Decibels Pegasus Lectures, Inc. Decibels is a logarithmic power ratio:
Note: the extra factor of 2 in the amplitude form converts the amplitude ratio into a power ratio.
Pegasus Lectures, Inc.
COPYRIGHT 2006

28. Amplitude versus Frequency
Amplitude and frequency are measures of completely different parameters.
In terms of sound:
Amplitude corresponds to volume
Frequency corresponds to pitch
Pegasus Lectures, Inc.
COPYRIGHT 2006

29. Same Frequency – Different Amplitude
Fig. 33: (Pg 135)
Pegasus Lectures, Inc.
COPYRIGHT 2006

30. Same Amplitude – Different Frequency
Fig. 34: (Pg 136)
Pegasus Lectures, Inc.
COPYRIGHT 2006

31. Notes
Pegasus Lectures, Inc.
COPYRIGHT 2006