physics

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Author:
lmarie
ID:
16174
Filename:
physics
Updated:
2010-04-25 22:11:38
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Period
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Description:
ARDMS SPI Physics Review
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  1. The effects of the medium upon the sound wave.
    Acoustic Propagation Properties
  2. The effects of the sound wave on biologic tissue
    Biologic Effects
  3. Sound is what kind of wave?
    Mechanical, longitudinal
  4. Period-
    Definition?
    Determined by?
    Changed by sonographer?
    The time required to complete a single cycle

    determined by--source

    changed by sonographer--no
  5. Frequency-
    Definition?
    Units?
    Determined by?
    Changed by sonographer?
    • Definition--The number of certain events that occur in a particular time duration
    • Units-- per second, hertz, Hz
    • Determined by--Source
    • Changed by sonographer--no
  6. Ultrasound Range?
    Greater than 20,000Hz, not audible
  7. Audible Sound
    20-20,000 Hz
  8. Infrasound?
    Less than 20 Hz
  9. Formula for intensity?
    • I= power/area
    • I=w/cm2
  10. Intensity is proportional to?
    Amplitude2
  11. Formula for wavelength?
    wavelength (mm)= prop. speed (mm/us) / frequency (MHz)
  12. Formula for wavelength in soft tissue?
    wavelength= 1.54mm/frequency (MHz)
  13. Wavelength is determined by?
    Source and Medium
  14. Propagation speed is determined by?
    • Medium only,
    • density and stiffness
  15. Propagation Speed formula?
    • speed= frequency x wavelength
    • (m/s) =(Hz) x (m)
  16. In-Phase waves interfere how?
    Constructively
  17. Pulse duration formula?
    PD= number of cycles in pulse x period

    or

    PD=number of cycles in pulse / frequency
  18. Pulse Repetition Period definition?
    The time from the start of one pulse to the start of the next pulse. Includes "on time" and "off time"
  19. PRP
    Determined by?
    Changed by sonographer?
    • Determined by-- source
    • Changed by sonographer--yes
    • (amount of listening time is determined by image depth)
  20. PRF definition?
    The number of pulses that occur in one second
  21. PRP formula?
    1/ PRF
  22. PRF formula?
    1/ PRP
  23. Depth and PRF are related how?
    Inversely proportional
  24. Depth and PRP are related how?
    directly proportional
  25. PRP x PRF = ??
    1
  26. Duty Factor formula?
    DF = PD/PRP x 100
  27. Duty Factor
    Definition?
    Determined by?
    Changed by sonographer?
    • Definition-- The percentage of time the system is transmitting sound. (% of "on time")
    • Determined by-- source
    • changed by sonographer--yes
  28. SPL formula?
    SPL= number of cycles x wavelength
  29. SPL determines resolution?
    Axial resolution
  30. PRP, PRF, and DF are all affected by what?
    Depth of view
  31. What intensity is most relevant with respect to tissue heating?
    SPTA
  32. What is the log of:
    a-100?
    b-10,000?
    • a-2
    • b-4
    • (count the zeros)

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