DMU physics final

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DMU physics final
2010-09-19 02:38:47
ultrasound physics

DMU physics final review
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  1. A linear array transducer creates a _____ image
  2. contrast agents are
    • called microbubbles
    • can be swallowed
    • strong reflectors of ultrasound
  3. shallow imaging has
    • higher frame rate
    • shorter go-return time
    • superior temporal resolution
  4. when frame rate increases, ____ resolution improves
  5. harmonic frequency arises from
    non-linear behavior
  6. low MI has _____ harmonics
  7. high line density improves individual images with images containing more detail. this improves
    spatial resolution
  8. a damaged crystal array
    • displays a single shadow on the overall image
    • has to be reported
  9. what is the dynamic range of an ultrasound system that can process voltages ranging from 5 volts to 5000 volts
    60 dB
  10. with linear phased array transducers, ___ crystals are fired to create each sound pulse
  11. high MI causes
    • bubbles to rupture
    • strong harmonics
  12. fundamental frequency is
    frequency created by the transducer
  13. affects the number of pulses
    • sector size
    • line density
    • number of focal points
  14. dynamic range is measured in
  15. a mechanical transducer has
    mechanical steering
  16. frame rate is affected by
    • speed of sound in the medium
    • imaging depth
  17. harmonic frequency is
    • twice the fundamental frequency
    • the second harmonic frequency
  18. artifacts created by array transducers are called
    grating lobes
  19. frame rate and Tframe are ______________ related
  20. if a transducer transmits a fundamental frequency of 2 MHz the harmonic frequency will be
    4 MHz
  21. the main advantage of multiple focal zones is it provides excellent ____ resolution
  22. the amount of contrast harmonics produced can be estimated by a number called ---
    the mechanical index (MI)
  23. slice thickness resolution is also called
    elevational resolution
  24. an amplifier increases a voltage from 5 to 5000 volts. how many decibels of gain is this?
  25. imaging depth and number of pulses in each picture
    • determine frame rate
    • are controlled by the sonographer
  26. what determines the frame rate on an ultrasound machine
    • imaging depth
    • speed of sound in the medium
  27. what increases temporal resolution
    • narrow sector
    • single focus
    • shallow imaging
    • low line density
  28. contrast harmonics result from
    non linear behavior of microbubbles
  29. number of lines per frame and the frame rate determine the
  30. wide sector image will
    • inferior temporal resolution
    • lower frame rate
    • more pulses per frame
  31. if a sonographer turns off the multi-focus feature, what would happen?
    temporal resolution improves
  32. dynamic aperture is a form of
    • recieve electronic focusing
    • accomplished by varying the number of crystals being used to recieve the reflected signal coing back from the body
  33. convex transducers have a blunted ____top
    fan shaped
  34. annular arrays
    • use inner crystals for shallow regions
    • have larger diameter rings that have a deep focal length
    • use outer crystals to image outer regions
    • have small diameter rings with a shallow focus that diverges rapidly
  35. phased arrays typically have _____ crystals
    100 - 500
  36. linear switched or sequential arrays
    • rectangular shaped
    • large transducers with approx 200 crystals or elements arranged in a line that are fired at different times in sequence

    have no steering and are fixed focusing