Radiology chapter twenty two

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Radiology chapter twenty two
2010-10-14 08:22:56
Chapter twenty two panoramic fillm

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  1. Uses of the panoramic x-ray
    • evaluate impacted teeth
    • evluate eruption patterns
    • detect diseases, lesions, and conditions of the jaw
    • examine extent of large lesions
    • evaluate trauma
  2. What should the panoramic film not be used to determine?
    • diagnos caries
    • periodontal disease
    • periapical regions
  3. The x ray tube moves around the patients head in one direction while the film rotates in the____________________.
    opposite direction
  4. tomo
  5. allows the imaging of one layer or section of the body while blurring images from structures in other planes
  6. The tomography image in dental radiology conforms to what?
    the shape of the dental arches
  7. the pivotal point or axis, around which the cassette carrier and x-ray tubehead rotate is termed what?
    rotation center
  8. What are the 3 rotation centers?
    • double-center rotation
    • triple-center rotation
    • moving=center rotation
  9. does the center of rotation change as the film and tubehead rotate around the patient? What does this allow?
    • yes
    • the image layer to conform to the elliptical shape of the dental arches
  10. the location and number of rotational centers influences what?
    the size and shape of the focal troph
  11. 2 rotation centers, one for the right side, one for the left side
    double-center rotation
  12. 3 rotational centers, uninterrupted image
    triple-center rotation
  13. continously moving circle, uninterrupted image
    moving-center rotation
  14. a 3 dimensional curved zone in which structures are clearly demonstrated on a panoramic radiograph; used to determine where the dental arches must be positioned to achieve the clearest image
    focal trough
  15. in most panoramic x-ray machines, the focal trough is__________in the anterior, and____________in the posterior
    • narrow
    • wide
  16. What do different panoramic x-ray machines differ in?
    • number of rotation centers
    • size and shape of focal trough
    • type of film transport mechanism used
  17. what are the similar components that each panoramic x ray machine have?
    • x-ray tube head
    • head positioner
    • exposure controls
  18. describe the collimater used in panoramic radiography.
    lead plate with an opening in the shape of a narrow vertical slit
  19. Where does the x ray beam travel in panoramic radiography?
    through the narrow slit in the collimator, emerges as a narrow band and passes through the pt, then through another vertical slit in the cassette carrier
  20. what is the main purpose of a collimator?
    to reduce patient exposure to x radiation
  21. Does the vertical angulation ever change in panoramic x ray?
  22. the tubehead of the unit always rotates___________the pts head as the film rotates______________of the pts head.
    • behind
    • infront
  23. head positioner consists of
    • chin rest
    • notched bite block
    • forehead rest
    • lateral head support or guides
  24. Which of these is fixed and can't be moved?:
    exposure time
    exposure time
  25. What is the purpose of the screen film?
    it converts the x rays to light, and then exposes the film
  26. What sizes are the film used in panoramic radiology available in?
    • 5 X 12
    • 6 X 12
  27. what color of light does calcium tungstate screen emit? And rare earth?
    • blue
    • green
  28. Which type of intensifying screen is recommended and why?
    rare earth, because it requires less x-ray exposure and is faster, so less radiation to the pt
  29. What must you label on the casset of the panoramic film?
    • left and right sides
    • dentist name
    • pt name
    • date
  30. What is the purpose of placing pts teeth in the notch of the biteblock?
    to align the teeth in the focal trough
  31. Where should the pts midsagittal plane be positioned for a pano?
    perpendicular to the floor
  32. where should the pts frankfort plane be positioned for a pano?
    parallel to the floor
  33. What are 2 more common pt preparation errors in panoramic radiography?
    • ghost image
    • lead apron artifact
  34. a radioopaque artifact seen on a panoramic film that is produced when a radiodense object is penetrated twice by the x ray beam, such as earings or hearing aids etc.
    ghost image
  35. how does a ghost image appear on a radiograph?
    indistinct, larger, and higher than its counter part, and is blurred
  36. What will appear on the radiograph if the pts lips arent closed on the bite block?
    a darke radiolucent shadow that obscures the anterior teeth
  37. What will appear on the radiograph if the tongue is not positioned on the roof of the mouth?
    a dark radiolucent shadow that obscures the apices of the maxillary teeth
  38. What happens if the pts chin is tipped up and the frankfort plane is not parallel to the floor?
    • hard palate and floor of the nasal cavity appear superimposed over the roots of the maxillary teeth
    • loss of detail in the maxillary incisor region
    • reverse smile line is seen on radiograph
  39. What happens if the pts chin is tipped down and the frankfort plane is not parallel with the floor?
    • mandibular incisors appear blurred
    • loss of detailn in the anterior apical regions
    • condyles may not be visible
    • exagerated smile line
  40. What happens if the pt is positioned anterior to the focal trough?
    anterior teeth appear skinny; image is blurred
  41. What happens if the pt is positioned posterior to the focal trough?
    anterior teeth appear fat; out of focus and blurred
  42. What happens if the pts head is not centered, midsagittal plane is not perpendicular to the floor?
    the ramus and posterior teeth appear unequally magnified on the pano; the side furthest from the film appears magnified, and the side closest appears smaller
  43. What happens if the pts spine is not strait?
    the cervical spine appears on the radiograph as a radiopacity
  44. What are the advantages of the pano?
    • field size
    • simplicity
    • pt cooperation
    • minimal exposure to radiation
  45. What are the disadvantages of the pano?
    • image quality
    • focal trough limitations
    • distortion
    • equipment cost