1. Fundamentals of Sonographic Wave Propagation and New Technologies
Michael J. Hartman, MS, RDMS, RVT, RT(R)

2. Presentation Disclaimer
The Society of Diagnostic Medical Sonography (SDMS) and the presenter do not endorse the products or companies included in this presentation, nor does the presenter or the SDMS make any assurances of the accuracy of statements or quality of goods and services. The SDMS and presenter have not received any financial compensation from the companies represented in this presentation.

3. Objectives Fundamentals of sonographic wave propagation
Classification of sound
Classification of waves
Propagation velocities
Transducers
Attenuation
New technologies regarding wave propagation

4. Sonographic Images
How are images formed?

5. Transducers
Converts energy from one form to another

6. Ultrasound Transducer Function
Converts one form of energy to another
Electrical to mechanical
Mechanical to electrical
Pulse-Echo Principle

7. How Sonographic Images are Formed
Transducer supplied with electric pulse
Transducer converts electrical energy into mechanical energy
Sound energy encounters an acoustical interface and is reflected back
Transducer converts mechanical energy into electrical energy
Internal processor determines the location and strength of the returning signal
Reflection is positioned on the display

8. SONAR = (SOund Navigation And Ranging)
In use since 1940’s
Echo location
Determine water depth

9. Classification of Sound
Infrasound = < 20 Hz
Audible Sound = 20-20,000 Hz
Ultrasound = > 20,000 Hz
Diagnostic Ultrasound = 2-20 MHz
Radiating Waves
Non-ionizing “radiation”

10. Classification of Waves
Electromagnetic waves
Will propagate in a medium or vacuum
Mechanical waves
Require a medium to propagate

11. Propagation of Mechanical Waves
Transverse waves
Longitudinal waves

12. Longitudinal Wave

14. Wavelength Wavelength = the distance a wave travels in a single cycle
Measured in units of distance

15. Frequency The number of times a wave is repeated per second
Determined by the source of the wave (transducer)
Measured in Hz (or MHz)
Higher frequency =
Shorter wavelengths
Increased resolution
Less penetration
Lower frequency =
Longer wavelengths
Decreased resolution
Greater penetration

16. Frequency One cycle per second = 1 Hertz (Hz)
One thousand Hertz = 1 kilohertz (kHz)
One million Hertz = 1 Megahertz (1 MHz)
Examples:
3 Hertz = 3 cycles per second
5.0 MHz transducer operates at 5,000,000 cycles per second
Image, Courtesy of Pegasus Lectures, Inc.

17. Frequency Same propagation speeds, but different frequencies
Wavelength is dependent upon frequency
Images, Courtesy of Pegasus Lectures, Inc.

18. Period Represents the time it takes between single cycles
Measured in units of time

19. Propagation Velocity (Speed of Sound in a Medium)
Wave speed = wavelength × frequency
v = λ ƒ
(where v is in m/s, λ is in m, and f is in Hz).

20. Acoustic Impedance Propagation Velocity (Speed of Sound in a Medium)
Determined by the properties of the medium
Density
Propagation velocity

21. Propagation Velocities
Average speed in soft tissue = 1540 meters/second
Image, Courtesy of Pegasus Lectures, Inc.

22. Amplitude
Amplitude = peak pressure of the wave, intensity of the returning echo

23. Amplitude With audible sound:
The loudness of the sound depends on the amplitude of the vibrations
The pitch of the sound corresponds to the frequency of the vibrations

24. Intensity
Intensity = Power
Beam area

25. Ultrasound Transducer Components

26. Elements

27. Matching Layer

28. Backing Material

29. Continuous vs. Pulsed Wave

30. Attenuation in Tissue
The reduction in power and intensity as sound travels through a medium
To diminish or decrease
Absorption, reflection, scattering, refraction & diffraction

31. Absorption Most dominant attenuation factor in soft tissue
Higher frequencies are absorbed faster than lower frequencies

32. Time Gain Compensation (TGC)
Operator-controlled adjustment to compensate for attenuation

33. Reflection
Image, Courtesy of Pegasus Lectures, Inc.

34. Specular Reflector Occurs at large, smooth interfaces
Image, Courtesy of Pegasus Lectures, Inc.

35. Scattering
Image, Courtesy of Pegasus Lectures, Inc.

36. Rayleigh Scattering
Image, Courtesy of Pegasus Lectures, Inc.

37. Refraction

38. Diffraction

39. Potential Bioeffects Thermal = generation of heat
Mechanical = production of bubbles (Cavitation )

40. Ultrasonic Cleaning
Ultrasonic cavitation used for cleaning small items

41. Ultrasonic Disintegration
Ultrasonic cavitation used to kill bacteria

42. Therapeutic Ultrasound

43. Ultrasonic Cavitation/Lipo Cavitation

44. Ultrasonic Drug Delivery/ Phonophoresis

45. Extracorporeal Shock Wave Lithotripsy (ESWL)

46. Percutaneous Nephrolithotomy
Left kidney

47. High Intensity Focused Ultrasound (HIFU)

48. Focused Ultrasound Guided by MRI

49. Silicone Tissue Mimicking Phantom
Before
After

50. Testing for Initial Accuracy with MR

51. Wireless Future of Medicine

52. Holter Monitor

53. First Wireless Ultrasound System

54. Battery and Transducer

56. References
Kremkau, F. W. (2005). Diagnostic Ultrasound: Principles and Instruments. Philadelphia, PA: Saunders.
Miele, F. (2006). Ultrasound Physics & Instrumentation. Forney, Texas: Pegasus Lectures, Inc.
Pistol Shrimp Video (2007). Available from
Schroeder, A., Kost, J., & Barenholz, Y. (2009). Ultrasound, liposomes, and drug delivery: principles for using ultrasound to control the release of drugs from liposomes. Chemistry and Physics of Lipids, 162(1), 1-16.
Siemens (2012). Siemens Acuson Freestyle Wireless Ultrasound Transducer. Available from
TedTalks (2011). Yoav Medan: Ultrasound Surgery - Healing Without Cuts. Available from
TedTalks (2010). Eric Topol: The Wireless Future of Medicine. Available from
Zagzebski, J. A. (1996). Essentials of Ultrasound Physics. St. Louis, Missouri: Mosby.