RT 180 test 2

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fongpay03
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117140
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RT 180 test 2
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2011-11-17 00:00:09
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RT 180 test 2
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  1. Recommended kVp for iodinated contrast studies:
    70-75 kVp
  2. Recommended kVp for barium contrast studies:
    110-120 kVp
  3. Recommended kVp for bone studies:
    55-70 kVp
  4. Recommended kVp for chest studies with grid:
    110-120 kVp
  5. Recommended kVp for chest studies without grid:
    75-85 kVp
  6. Recommended kVp for abdomen studies:
    75-80 kVp
  7. Recommended exposure times to control motion unsharpness for head and neck:
    50-100 milliseconds
  8. Recommended exposure times to control motion unsharpness for the heart:
    3-7 milliseconds
  9. Recommended exposure times to control motion unsharpness for the abdomen:
    50-80 milliseconds
  10. Recommended exposure times to control motion unsharpness for extremities:
    50 milliseconds
  11. Recommended exposure times to control motion unsharpness for pediatric exams:
    Requires much faster exposure times
  12. High (shorter) contrast. More or less shades of gray?
    Less shades of gray
  13. Low (longer) contrast. More or less shades of gray?
    More shades of gray
  14. Lower kVp = _____wavelengths, _____ energy, ______ penetration, _______ contrast, _____ gray scales.
    • Longer wavelengths
    • Lower energy
    • Lower penetration
    • Higher contrast
    • Lower gray scales
  15. Higher kVp = _____wavelengths, _____ energy, ______ penetration, _______ contrast, _____ gray scales.
    • Shorter wavelengths
    • Higher energy
    • More penetration
    • Lower contrast
    • Higher gray scales
  16. kVp controls what image quality?
    • Contrast
    • Gray scale
    • Density
  17. What rule for kVp is used to see a visible change?
    5% rule
  18. SID controls what image characteristic?
    Size distortion (magnification)
  19. What is affected by tube object IR alignment and angling of the CR?
    • Shape distortion (foreshortening or elongation)
    • ***SID does not affect these image qualities
  20. How much of a change in SID is required to actually see a change in visible density? ( in the clinical setting)
    20%
  21. Increasing SID, _______ pnuembra
    Decreases
  22. Define radiographic quality
    The degree of excellence that anatomical structures are displayed
  23. What are the two photographic properties?
    • Density and contrast
    • ***visibility
  24. What are the two geometric qualities?
    • Sharpness of recorded detail and distortion
    • ***sharpness
  25. What rule for kVp is used to maintain equal image density?
    • 15% rule
    • ***increase kVp by 15%, decrease mAs by 1/2(50%)
    • ***decrease kVp by 15%, increase mAs by 2
  26. What is the geometric unsharpness formula?
    FS x OID/SOD
  27. What is the magnification factor?
    SID/SOD
  28. What is the % of magnification?
    • Subtract 1 then x 100
    • ***must first calculate the magnification factor
  29. Foreshortening is caused:
    When anatomy is angled, beam is perpendicular to IR, but IR is not parallel to anatomy
  30. Elongation is caused:
    When anatomy is angled, beam is perpendicular to anatomy, but beam is not perpendicular to IR and beam is not parallel to anatomy
  31. The ______ the matrix size and the ______ the pixel size = the sharper the spatial resolution
    Bigger; smaller
  32. Define dynamic range
    The maximum number of gray shades that can be displayed on a monitor
  33. Define bit depth
    The pixel's ability to display ranges of gray shades
  34. Define contrast resolution
    The ability to distinguish many shades of gray from black to white
  35. Increasing window leveling makes the image ____ on the CRT monitor (darker or lighter)
    Darker
  36. Decreasing window leveling makes the image _____ on the CRT monitor (darker or lighter)
    Lighter
  37. Increasing window width(ing) results in ___ visible gray shades ( more or less)
    More
  38. Decreasing window width(ing) results in ___ visible gray shades ( more or less)
    Less
  39. What must be set first? Window width or window leveling?
    Window width to get visible gray scale range then window level for desired brightness
  40. Typical QC testing for monitors could include:
    • Display resolution
    • Display luminance
    • Geometric distortion
    • Spatial resolution and noise
  41. Square law formula
    I1/I2 =(D1/D2)squared
  42. Reciprocity Law
    Exposure = intensity x time
  43. What is the reciprocity law failure?
    When exposure times are too long or short which results in reduced speed. Increase of radiographic technique may be required
  44. Define exposure time (T)
    • length of time that tube circuit is closed thereby allowing the electrons in the space charge to move (flow) from the filament (cathode) over to the anode thus producing x-rays
    • ***electrons come from the cathode then move to anode
  45. High kVp techniques result in low contrast images for 3 important reasons:
    • 1. Increase penetration of the primary beam through various tissues lengthens the image gray scale
    • 2. Photoelectric interactions are rapidly lost, leaving a high Compton-to-photoelectric ratio: In the image, "white" densities are lost, leaving fog more apparent in the image
    • 3. Scatter radiation produced by the Compton interaction is both more energetic and scatters in a more forward direction, so that an increased amount of scatter reaching the film produces more fog in the image
  46. Anode heel effect
    The intensities of primary beam varies along the longitudinal axis of primary which less intensity on the anode side of beam.
  47. Regarding grids, lower ratio = _____ clean-up scatter, _____ density
    • less clean-up scatter
    • more density
  48. Regarding grids, higher ratio = _____ clean-up scatter,_____ density
    • more clean-up scatter
    • less density

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