Study guide test 3

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Study guide test 3
2012-11-04 00:07:14
Chapters 13

Chapters 9-13
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  1. What adjusts the intensity of the ultrasound beam transmitted into the patient?
    power control
  2. How does power control effect images?
    Improves signal-to-noise ratio and enhances sensitivity
  3. What reduces the signal-to-noise ratio and degrades sensitivity?
    phase aberration
  4. A loss of signal coherence during beam formation is called?
    phase aberration
  5. What is it when echo frequency is subdivided into frequency bands by filters, processed, then recombined?
    Frequency compounding
  6. What is the purpose of frequency compounding?
    To emphasize penetration, resolution, or tissue texture (To improve contrast resolution)
  7. What aquires multiple beam angles and averages the data, reduces acoustic noise while improving border definition of speculations reflectors
    Spatial compounding
  8. What improves the depiction of tissue boundaries and reduces noise variations?
    Spatial compounding
  9. What effect does compression have on an image?
    Changes the grayscale mapping
  10. What increases amplitude of low signals and decreases amplitudes of high signals so that all echo-induced signals are represented in the scan converter?
    Log compression
  11. What improves image contrast but usually with a loss of weaker echoes?
    Low dynamic range
  12. What reduces image contrast but retains a broader extent of signal levels?
    High dynamic range
  13. What scanning technique creates a visual display of information that would be obtained by manual palpation?
  14. What detects the relative tissue displacement between precompression (no stress) and compression (stress) measured by ultrasound?
  15. What does it mean if strain is proportional to stress?
    the material exhibits elastic behavior
  16. As the sound wave propagates through the medium, ________ components intesify , and the waveform becomes more distorted.
  17. What are present in the central portion of the transmitted beam but offset from the transducer face?
  18. What are created as a result of propagation through tissue and are not produced upon reflection?
  19. What is applied to remove the fundamental echo signal, and only the tissue harmonic component is processed for image formation?
    harmonic band filter
  20. What employs long waveforms during transmission to improve the signal-to-noise ratio and/or penetration?
    coded excitation
  21. What are two common methods to encode transmitted waveform?
    • 1. frequency modulation
    • 2. binary encoding
  22. What eliminates low-level signals and noise below a certain level when selected by the operator?
    rejection controls
  23. Rejection of signals decreases what?
    Dynamic range
  24. What removes weak signals and noise?
  25. How does rejection remove weak signals and noise?
    by passing only signals greater than a prescribed signal level
  26. What can be applied to enhance spatial detail?
    write zoom
  27. What are negative properties of persistence?
    • 1. fast-moving objects become blurred with increased persistence
    • 2. poor temporal resolution
  28. What are positive properties of persistence?
    • 1. allow high-quality abdominal scans to be ontained
    • 2. reduces noise
  29. The translation of the range of pixel values to brightness levels is called?
    gray-scale mapping
  30. What is selected by the operator and can alter the presentation of the displayed image?
    gray-scale map
  31. What does user-controlled compression modify?
    gray-scale map
  32. What is a scan conversion method to assign echo amplitude to a pixel, which is not interrogated by a scan line?
    bilinear interpolation
  33. Where is bilinear interpolation performed?
    in axial and angular directions
  34. What are the two types of acoustic noise?
    • 1. clutter
    • 2. speckle
  35. What are "false" echo signals originating outside the main beam caused by side lobes, grating lobes, and scattering?
  36. What are the bright and dark variations in the image from scattering of multiple small non-specular reflectors?
  37. What is determined primarily by the spatial pulse length, which depends on the center frequency and the bandwidth of the transducer?
    Axial resolution
  38. What defines the finite size of the detection sampling volume along the axial direction?
    Spatial pulse length
  39. What is the best axial resolution considered to be?
    Half the spatial pulse length
  40. What is determined primarily by the beam width and the scan-line density?
    Lateral resolution
  41. What depends on beam width and changes with depth?
    Lateral resolution
  42. What is contrast?
    The difference in brightness levels
  43. What has high signal levels and are readily seen?
    Small reflectors
  44. What two components make up image contrast?
    • 1. intrinsic (detection) contrast
    • 2. displayed contrast
  45. What do time gain compensation and dynamic range affect?
  46. Displayed contrast translates pixel values to brightness levels on the monitor via what?
    Gray-scale map
  47. What describes the ability of a series of several frames aquired sequentially in time to depict the movement of structures?
    Temporal resolution
  48. What does decreasing scan range, scan-line density, persistence, or sector angle improve?
    Temporal resolution
  49. An increase in frame rate is usually accompanied by what?
    Reduction in scan-line density
  50. Frame rate, scan-line density, and scan range are all ____________
  51. What does the inaccurate presentation of spatial relationships cause?
    Geometric distortion
  52. What can an improperly calibrated PACS interface or image recording device introduce?
    Geometric distortion
  53. What is the assignment of an intermediate signal level when the ultrasonic beam encompasses objects with different reflectivities?
    Partial volume
  54. Frequency and spatial compounding enhances signals from tissue features while ___________ ______
    Suppressing speckle
  55. What is partially canceled when multiple images are added together?
  56. What artifact can occur in-plane direction (lateral) or out-of-plane direction (slice thickness)?
    Partial voume
  57. High receiver gain or TGC increases the visibilty of what artifact?
    Partial volume
  58. What is another name for elevation plane?
    Slice thickness
  59. What artifact can sample multiple tissues at once and blend the reflectors together?
    Partial volume
  60. Where is partial volume artifact typically seen?
    Beyond the mechanical focal zone
  61. What artifacts area is distal to low attenuation structure and has more intensity of reflections than surrounding tissue?
    Acoustic enhancement
  62. What artifact area is distal to high attenuation structure and has less intensity of reflections than surrounding tisue?
    Acoustic shadowing
  63. What artifact is seen in an area of fixed transmit focus where there is a greater intensity in the focal zone?
  64. What causes banding artifact to be seen?
    improper TGC setting
  65. What artifact has multiple evenly spaced echoes, decreasing in intensity?
  66. What artifact has a "ladder appearance" when sound bounces between two strong reflectors?
  67. The mscle interface near the skin surface is often the source of what artifact?
  68. What artifact is made up of small, highly reflective objects?
    Comet tail
  69. What artifact looks similar to reverberation, but more closely spaced together?
    Comet tail
  70. What artifact typically arises from the near wall or lumen of the gallbladder when crystaline deposits of cholrsterol are present?
    Comet tail