Exposures Test #2

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njpeterson
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25568
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Exposures Test #2
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2010-07-06 18:11:08
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Exposures Test
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  1. What are the two photographic properties?
    Density and Contrast
  2. What are the two geometric properties?
    Recorded detail and Distortion
  3. Definition, sharpness, spatial resolution all mean....
    Recorded detail
  4. Recorded detail is measured in _______________.
    line pairs per millimeter (lp/mm)
  5. True or False: All radiographic images have less recorded detail than the object itself.
    True
  6. As matrix size increases, pixel size decreases, and spatial resolution ______________.
    Increase
  7. As bit depth increases, spatial resolution ___________.
    Increases
  8. Lots of line pairs per millimeter, tiny object size.
    High spatial frequency
  9. Few line pairs per millimeter, large object size.
    Low spatial frequency
  10. High signal to noise ratio means what in terms of resolution?
    Good Resolution
  11. Measures the accuracy of an image compared to the original object on a scale of 0 to 1.
    Moduation Transfer Function (MTF)
  12. What does 1 and 0 represent in MTF?
    • 1 = perfect, image can never be perfect.
    • 0 = no image.
  13. In the Nyquist Theorem, digital imaging requires that the spatial resolution fequency signal be sampled how many time from each cycle?
    Twice
  14. This occurs when Nyquist Theorem is violated, and the incoming data is sampled less than twice per cycle.
    Aliasing
  15. True or False: Ojects smaller then the size of the focal spot cannot be imaged.
    True
  16. As OID decreases, resolution _____________.
    Increases
  17. As SID increases, resolution ______________.
    Increases
  18. Sharpness of an image.
    Umbra
  19. The imperfect, unsharp shadow surrounding the umbra.
    Penumbra
  20. As focal spot size decreases, penumbra decreases, and resolution _______________.
    Increases
  21. Radiographic film usually has resolving capabilities in the range ______ lp/mm, far beyond the ability of any screen or human eye.
    100
  22. As phosphor size and layer thickness decrease, resolution ____________.
    Increases
  23. As gray scale bit depth increases, what happens to resolution?
    As gray scale bit depth increases, resolution increases.
  24. As concentration of phosphor layer increases, resolution __________.
    Increases
  25. As film/screen speed increases, what happens to resolution?
    As speed increases, resolution increses
  26. What is the main cause for loss of resolution in CR?
    Light scattering
  27. What is the main cause for loss of resolution in DR?
    The monitor
  28. Why does motion reduce recorded detail?
    Anatomy does not stay in place long enough for image to form, this creates blurriness
  29. What is the only way to correct quantum mottle?
    Increase mAs
  30. How does motion affect resolution?
    Motion decreases resolution
  31. Motion that is under the direct control of the patient.
    Voluntary
  32. Motion that is not under the conscious control of the patient.
    Involuntary
  33. What are some ways to reduce voluntary motion?
    Provide clear patient instructions and immobilization
  34. What are some ways to reduce involuntary motion?
    Decrease time and increase mAs
  35. The misrepresentation of size or shape of the structures being examined.
    Distortion
  36. Why is size distortion always magnification in film/screen radiography?
    The divergence of the beam.
  37. True or False: Size distortion is always minification in film/screen radiography.
    False
  38. As OID increases, magnification ______________.
    Increases
  39. How is size distortion affected by an increase in SID?
    As SID increases, magnification decreases
  40. As OID increases, resolution ______________.
    Decreases
  41. The misrepresentation by unequal magnification of the actual shape of the structure being examined.
    Shape distortion
  42. The object appears to be longer than it really is.
    Elongation
  43. Object appears shorter than it really is.
    Foreshortening
  44. When does elongation occur?
    When the tube or the image receptor is improperly aligned.
  45. When does foreshortening occur?
    When the part is improperly aligned.
  46. CR is ____________ to the part and the image receptor
    Perpendicular
  47. The part is _____________ to the image receptor.
    Parallel
  48. If the CR is not centered to the part, how is the image formed?
    The image is formed by angled photons and shape distortion occurs.
  49. The application of scientific knowledge to an analysis of the image.
    Art of image critique
  50. True or False: An optimal diagnostic quality radiograph is always within acceptable limits.
    True
  51. Equipment performance monitoring through a variety of quality assurance and quality control.
    Quality control.
  52. True or False: An non-optimal diagnostic quality radiograph is always within acceptable limits.
    True. Film is still passable, just learn from this exam
  53. True or False: If an image is outside acceptance limits, it must be repeated.
    True
  54. What are the three major categories for determining the cause of image problems?
    • Technical factors - denstiy and contrast or recorded detail and distortion
    • Procedural factors - patient positioning and/or patient prep
    • Equipment malfunction - x-ray machine or processor
  55. Quality in all aspects of imaging chain is termed...
    Quality Assurance
  56. Quality Control controls....
    Equipment and performance standards
  57. what is the largets hosptial accredidation agency?
    JCAHCO (joint commission of accredidation of health care organization)
  58. How often is the processor senistometric monitored? Why is it monitored?
    It is monitored daily. This is done to determine if it is operating w/i limits
  59. What equipment is necessary for processor senisitometric monitoring?
    • control box of film (all films come out of same box)
    • sensitometer (puts densities on the film)
    • densitometer (reads densities)
    • digital thermometer (bc it doesnt break, wont contaminate)
  60. contrast index
    speed index
    b+f
    developer temp
    • be w/i + or - .1
    • be w/i + or - .1
    • be w/i + or - .5
    • be w/i + or - .1 (f) or + or - .5 (c)
  61. how often are dark room safe lights tested?
    semiannually (every 6 mo.)
  62. what are some reasons why safe lights can fog film?
    • cracked/ worn filter (cause fading)
    • wrong bulb wattage
    • too many safe lights
    • safe lights are too close to work area
  63. too much fog on film...
    low contrast, high density
  64. film that is exposed or unexposed to safe lights has to be..
    less than or equal too .02 OD
  65. focal spot size test is done how often?
    semiannually
  66. what are 3 tools used to measure FSS and how are they used?
    • lp/mm tool- image piece on equipment then read it compared to a key
    • star test pattern- image piece on equipment then read it compared to a key
    • pin hole camera- creates a density on film, indicating the FS (creates image of affected FS)
  67. How is HVL measured?
    mm/Al
  68. if the beam is filtered too little, half vaule layer is....
    half value layer is low ( soft/ low energy photons still in the beam= increase pt. dose)
  69. when checking collimator, central ray, and bucky tray accuracy what two tools can be used?
    • collimator template- place table top, collimate to square on template
    • beam alignment tool- place on collimator template and align steel ball to bullseye
  70. if the light field is larger than xray field....
    if the light field is smaller than xray field...
    • clip anatomy
    • increased pt. dose
  71. distance and angulator accuracy acceptance limits
    calculated SID = + or - 2% of actual SID
  72. If tube angulation is + or - actual angle on angle indicator ___________ results
    distortion
  73. actual KVP needs to be b/w ____% of tested KVP than whats set.
    5
  74. KVP DRIFTS OVER TIME
  75. timer accuracy is determinded by
    • spinning top test = pulses, should be a certain # of dots to match up (single phase)
    • synchronized spinning top test= done for 3 phase and high frequency
  76. what are the acceptance limits for timer accuracy?
    + or - 5% of actual time compared to set time
  77. shorter exposure time = _____ density
    less
  78. Generator is capable of repeating expsoures accurately
    • Reproducibility
    • ( same dosimeter reading every time)
  79. expose dosimeter w/ different combinations w. mA & time but get same reading
    Linearity
  80. if linearity is out of limits...
    density increases all the time OR density is decreased all the time
  81. display monitors are adjusted until
    • all shades of gray are visible
    • (this is seen on a SMPTE test pattern)
  82. Display monitors are tested for...
    • resolution
    • brightness
  83. PACS system is checked to...
    make sure HIS & RIS is all working w/ data accurately
  84. what is Fix Q
    where innaccuracy on file goes and is MANUALLY changed (human is neeeeded!)
  85. Repeat image studies are done _____ & to determine ________.
    • quarterly
    • amount and cause of repeats
  86. If the repeat rate is too low...
    Repeate rate should be..
    • techs are passing poor quality films for fear of repercussions
    • b/w 3 & 10%

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