RAD-172 MIDTERM CH.22 28 29 30

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  1. Intensifying screens produce ______
    a large amount of light photons when struck by xray photons
  2. what is the purpose of IS
    amplify the incoming xray beam and reduce patient dose
  3. describe the construction of the IS
    • composed of radiolucent plastic coated with phosphors that emit light when struck
    • they are in pairs on the top and bottom of cassette so a fil can be put in between
  4. what are the four layers of the IS
    • base
    • reflective layer
    • phosphor layer
    • protective coat
  5. what is the active layer of the IS
    phosphor layer
  6. what is the refelctive layer composed of
    magnesium dioxide or titanium dioxide
  7. what are the characteristics of phosphors
    • high atomic number
    • high conversion efficiency
    • appropriate spectral matching
    • minimal phosphorescence
  8. what is conversion efficiency
    what decreases as conversion efficiency increases
    • the ability of the phosphor to emit as much light per xray photon interaction as possible per measurement of screen speed
    • pt dose
  9. what is spectral emission
    spectral matching
    • an indication of the precise wavelength emitted by the phosphor
    • ability to match the sensitivity of film to latent image matching color of light to film
  10. what are the two types of luminescence
    fluorescence and phosphorescence
  11. what is another term for screen lag or after glow
    delayed phosphorescence emission
  12. why are rare earths used
    they offer increased speed w/ maintaining resolution, when compared to calcium tungstate screens
  13. list some rare earth phosphors
    list their spectral matching
    • gadolinium green
    • lanthanum blue
    • yttrium blue
    • calcium tungstate blue
  14. what are the characteristics that film screens posses
    same features as films
  15. how many lp/mm can the naked eye resolve
    state the lp/mm for non screen detail par, and high speed screens
    • 10-20lpmm
    • non screen 100lp/mm
    • detail par 15lp/mm
    • high speed screens 7lp/mm
  16. how does film lose contact with screens
    caused by foreign objects in the cassette and warped or damged cassettes
  17. what test is done to check for poor film screen contact
    wire mesh test
  18. what is quantum mottle
    happens when insufficient phosphor crystals emit light to expose a
  19. How can you reduce quantum mottle
    increase mAs
  20. what factors can affect screen speed but not resolution
    kvp and high temperature
  21. how can film speed be classified as three things
    • intensification factor
    • descriptive rating
    • relative speed number
  22. what is the k-shell absorption edge
    when incident xray photons match the K-shell binding energy of the phosphor ther is an increase in characteristic production within the screen
  23. what is an asymmetrical screen
    screens that have increased quantum mottle resolution to show better detail
  24. what are some characteristics film cassettes
    • front of cassette is radiolucent
    • the IS screens are attached to the inside of the front and back of cassette
    • rigid to support body parts and lightweight
    • made with lead foil to reduce the residual beam and absorb back scatter
  25. what is the proper care of a cassette (4 things)
    • when loading cassettes the tops should never be fully open
    • cassettes sohuld be stored on end like a book
    • screens should be cleaned with electrostatic cleaning solution
    • never close a wet cassette
  26. what is an artifact
    anything that blocks the transmission of light between the screen and film (dust or pitted screens, white spots)
  27. panchromatic films
    orthochromatic films
    • film that is sensitive to entire visible light spectrum
    • ortho films only sensitive to green light
  28. define density/IR exposure
    the amount of radiation that has exposed the IR
  29. brightness
    is a monitor control function that can change the lightness and darkness of an image on a display monitor but it is not related to IR exposure
  30. is brightness interchangeable with density
  31. describe how density is related to IR exposure
    the visibility of the image is the result of exposure to film in both film and DR
  32. window level
    window width
    • describes digital post processing that produce changes in brightness
    • contrast
  33. what is the controlling and influencing factor of density
    mas and kvp
  34. what are various terms for contrast
    • short scale
    • high contrast
    • increased
  35. what is subject contrast
    what is the dependent on
    • the range of differences in the intensity of the xray beam after it has been attenuated by the subject
    • kvp and the type of irradiated material
  36. what are the two photographic properties  that comprise the visibility of detail
    contrast and density
  37. high contrast factors are good for what studies
    soft tissue studies
  38. image receptor contrast deals with what
    h&d curve
  39. what is changeable in a fixed kvp system
    what is changeable in a variable kv system
    • mas changeable kv is fixed
    • kvp is changeable mAs is fixed
  40. recorded detail
    • one of the two geometeric properties of radiographic image quality
    • it is the degree of geometric sharpness or accuracy, spatial resolution of the structural lines recorded in the xray image
  41. spatial resolution
    how do we measure spatial resolution
    • deals with objects being closer together
    • using point spread function
  42. spatial frequency is measured using what
    modulation transfer function
  43. what is the unit of resolution for primary film/screen
    lines per millimeter
  44. matrix size:
    pixel size:
    gray scale:
    • a square of series of boxes that gives form to the image
    • picture elements; individual matrix boxes
    • the number of shades of gray in a radiographic image
  45. what is image noise
    bg information the image receptor receives
  46. nyquist criterion:
    • it is when digital imaging requires spatial resolution info to be sent/sampled over twice from each cycle
    • this is what compares the spatial frequency if it is not the same as nyquist criterion and the data sampled are less than twice per cycle then the image is changed with cauderoy lines
  47. what causes the cauderoy lines on an xray
    moire effect = from aliasing
  48. penumbra
    • geometric unsharpness
    • sharp area of a shadow
  49. geometric factors
    receptor factors
    • geo factors = FSS Distance OID,SID
    • recep. factors = Film/screen systems, digital systems
    • motion = voluntary involuntary equipment
  50. what other terms mean detail
    • sharpness definition
    • spatial resolution
  51. what is the geometric unsharpenss formula
    FOD is the same as ___
    OID is the same as ____
    how do you find FOD
    • FSS * object -film-distance or OID/FOD(focus object distance)
    • SOD
    • OFD

    SID - OID = FOD or SOD
  52. what is the density maintenance formula
    m2=m11*g2g1(Grid factors)*S1S2(Film Speed)*D2(squared)D1(squared)*K

    • if there is a 15% increase in kv (*1/2)
    • if there is a 15% decrease in kv (*2)
  53. list the grid conversion factors
    • no grid 1
    • 5:1 2
    • 6-1 3
    • 8-1 4
    • 10-1 5
    • 12-1 5
    • 16-1 6
  54. dynamic range
    the concept of contrast as it is displayed on a soft copy monitor for digital images, range of density/brightness of the display monitor light emission
  55. define contrast
    one of the properties that comprise visibilty of detail; the difference between adjacent densities
  56. what are three ways resolution can be measured
    through the lines per millimeter, line spread function and modulation transfer function
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RAD-172 MIDTERM CH.22 28 29 30
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