Dental Radiology

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sthomp88
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36661
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Dental Radiology
Updated:
2010-09-22 21:59:05
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dental ray image chapter eight
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characteristics
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  1. a series of steps that collectively produces a visible permanent image on a dental radiograph
    film processing
  2. purposes of film processing
    • convert the latent (invisible) image on the film into a visible image
    • to preserve the visible image so that it is permanent and does not disappear from the denta radiograph
  3. the portion of a processed radiograph that is dark or black
    radiolucent
  4. what type of structures appear radiolucent on an x-ray?
    structures that lack densiy and permit the passage of the x-ray beam with little or no resistance
  5. the portion of a processed radiograph that appears lightr white
    radiopaque
  6. what type of structures appear radiopaque?
    structures that are dense and absorb or resist the passage of the x-ray beam including, enamel,dentin, and bone
  7. Diagnostic radiograph produces images that;
    • exhibit proper density and contrast
    • have sharp outlines
    • are the same shape and size as the object being radiographed
  8. visual characteristics of dental radiograph
    • density
    • contrast
  9. the overall blackness or darkness of a dental radiograph
    density
  10. what 3 things does a radiograph with correct density allow the radiographer to view?
    • black areas - air space
    • white areas - enamel, dentin, and bone
    • gray areas - soft tissue
  11. 3 exposure factors that control the density of a radiograph
    • milliamperage (mA)
    • operating kilovoltagepeak (kVp)
    • exposure time
  12. true or false. Subject thickness/size and density of the bone also affect the overall density of a radiograph
    true
  13. How does an increase in milliamperage affect the film density of a radiograph?
    it produces more x-rays exposed to the film and increases the film density, so it appears darker
  14. How does an increase in operating kilovoltage peak affect the density of the radiograph?
    it increases the film density by increasing the average energy of the x-rays by producing x-rays with higher energy. the film appears darker
  15. How does an increase of exposure time affect the densiy of the radiograph?
    it increases the film density by increasing the total number of x-rays that reach the film surface. the film appears darker
  16. the difference in the degrees of blackness (densities) between adjacent areas on a dental radiograph
    contrast
  17. the difference in the amount of light transmitted through adjacent areas of a radiograph
    contrast
  18. very light and very dark areas that are strikingly different
    high contrast
  19. many shades of gray
    low contrast
  20. how is contrast determined?
    by film contrast and subject contrast
  21. characteristics of the film that influence radiographic contrast
    film contrast
  22. what type of characteristics influence the contrast of the film?
    • inherent qualities
    • film processing
  23. who controls the inherent qualities of the film
    the manufacturer
  24. who controls film processing of the radiograph?
    the dental radiographer
  25. true or false. an increase in development time or temperature increases the contrast of the film.
    true
  26. the characteristics of the subject that influences radiographic contrast
    subject contrast
  27. what type of characteristics is subject contrast determined by?
    • thickness
    • density
    • composition (atomic number) of subject
  28. how is subject contrast altered? And how does this affect the outcome?
    • by adjusting the kVp
    • high operating kilovoltage peak (more than 90) = low contrast
    • low operating kilovoltage peak (60-75) = high contrast
  29. what is the one exposure factor that has a direct influence on contrast of the radiograph?
    kilovoltage peak
  30. How does the kilovoltage peak directly affect the contrast?
    increasing the kilovoltag peak increases the average energy of the x-rays produced allowing them to penetrate tissue better which results in more variations in tissue on the film with varying shades of gray, or low contrast
  31. the range of useful densities seen on a dental radiograph
    scale of contrast
  32. a dental radiograph that shows only 2 densities, areas of black and white show what scale of contrast
    short-scale contrast
  33. a lower kVp results in a radiograph with ____________-scale contrast, which can also be described as having______________ contrast.
    • short
    • high
  34. a dental radiograph that exhibits many densities or many shades of grey exhibits which kind of contrast?
    long-scale contrast
  35. a higher kVp range results in a radiograph with _________-scale contrast and ______________contrast
    • long
    • low
  36. a device used to demonstrate short-scale and long-scale contrast
    stepwedge
  37. name the 3 geometric characteristics of the radiographic image
    • sharpness
    • magnification
    • distortion
  38. the capability of the x-ray film to reproduce the distinct outlines of an object or, in other words, to how well the smallest details of an object are reproduced on dental radiograph
    sharpness
  39. unsharpness, or blurring of the radiographic image that is present in every radiograph.
    penumbra
  40. what are the 3 factors that influence sharpness of a radiograph?
    • focal spot size
    • film composition
    • movement
  41. what are the meanings of the latin words pene, and umbra?
    • almost
    • shadow
  42. the tungsten target of the anode, which converts bombarding electron into x-ray photons, and concentrates the electrons and creates an enormous amount of heat.
    focal spot
  43. what is the size of the focal
    .6mm2 to 1.0mm2
  44. the smaller the focal spot area, the ___________the image appears; the larger the focal point size, the_____________the loss of image sharpness.
    • sharper
    • greater
  45. what is relative to the size of the crystals found in the film emulsion?
    sharpness
  46. what type of crystals does the emulsion of faster film contain?
    larger crystals that produce less image sharpness
  47. what type of crystals does the emulsion of slower film contain?
    smaller crystals that produce that produce more image sharpness
  48. true or false. Movement of either the film or the patient influences film sharpness
    true
  49. a radiographic image that appears larger than the actual size of the object it represents
    magnification
  50. what are the 2 factors that influence the image magnification on a target radiograph?
    • target-film distance
    • object-film distance
  51. distance between the source of x-rays (focal spot on the tungsten target) and the film
    target-film distance
  52. what determines the target-film distance?
    the length of the position indicating device
  53. a longer PID and target-film distance result in__________image magnification, and a shorter PID and target-film distance result in____________image magnification
    • less
    • more
  54. distance between object being radiographed (tooth) and the dental x-ray film
    object-film distance
  55. a decrease in object-film distance results in a______________in magnification, and an increase in object-film distance results in an___________ in magnification
    • decrease
    • increase
  56. a variation in the true size and shape of the object being radiographed
    distortion
  57. what causes a distorted image?
    • unequal magnification of different parts of the same object
    • improper film alignment or angulation of x-ray beam
  58. what influences the dimensional distortion of a radiograph?
    • object-film alignment
    • x-ray beam angulation
  59. how must the object and film be situated to avoid distortion?
    parallel to eachother
  60. how should the x-ray beam angulation be situated to the tooth to prevent distortion?
    perpendicular to the tooth and film

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