radiography ch 17 paralleling technique

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radiography ch 17 paralleling technique
2014-08-27 22:23:20
paralleling technique

chapter 17
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  1. parallel
    dont intersect
  2. intersecting
    they intersect
  3. perpendicular
    cross at them median plane
  4. right angle
    right angle
  5. long axis of the tooth
    basic concept
  6. central ray
    through center
  7. principles of paralleling technique
    • film (receptor) is placed in the mouth parallel to the long axis of the tooth being radiographed
    • central ray of the xray beam is directed perpendicular to the film and long axis of the tooth
    • film holder must be used to keep film parallel with the long axis of tooth
  8. paralleling technique principles object-film (receptor) distance must be
    increased to keep film parallel due to anatomic configuration of oral cavity (causes image magnification, causes loss of definition) her example of the tooth on the wall and flashlight
  9. to compensate for magnification and loss of definition
    • increase target-film distance to 16" (ours are already at 16 in lab)
    • use rectangular collimator to reduce amount of radiation patient receives by 70% don't use alot because hard to do
  10. film holders are
    beam alignment devices paralleling technique requires the use of these
  11. XCP paralleling technique
    • extension cone paralleling
    • yellow: are posterior PA
    • Red: bitewing -don't use really
    • Blue: anterior PA
  12. film for paralleling technique - anterior region
    size 1 film we use 2 placed vertical (tall) use cotton roll when taking film so you get the edge of the incisor
  13. film paralleling technique - posterior region
    • size 2
    • placed horizontal
  14. rules for paralleling technique
    • film (receptor) placement: positioned to cover the teeth to be examined
    • film receptor position: positioned parallel to the long axis of tooth- away from tooth
    • vertical angulation: rays must be perpendicular to film and long axis of tooth
    • horizontal angulation: rays must be directed through contact areas
    • film receptor exposure: beam must be centered on film so cone cutting is avoided
  15. paralleling technique step by step procedure
    • briefly expalin radiographic procedures to patient before beginning
    • adjust chair to upright and comfortable height for you so you arent' bending over lots
    • adjust headrest - upper arch should be parallel to floor, midsagittal (midline) is perpendiculaar to floor
    • place lead apron with thyroid collar on patient
    • remove all objects from mouth (dentures, retainers, gum) and remove eyeglasses
  16. step by step procedures for equipment preparation
    • set kVp (kilovoltage peak) and mA (milliamperage) to recommendations
    • open sterilized package and assembel film holder if needed
    • insert film packet into holder
  17. exposure sequence for film placement - anterior exposure sequence
    • start on maxillary right canine
    • expose all maxillary anterior teeth from right to left
    • end with the maxillary left canine
    • move to mandibular left canine
    • expose all mandibular anterior teeth from left to right
    • finish with mandibular right canine
  18. exposure sequence for film placement - posterior exposure
    • begin with the maxillary right quadrant
    • assemble the XCP (extension cone paralleling) for this area
    • expose premolar film first, then molar film
    • move to the mandibular left quadrant
    • expose premolar film, then molar film
    • reassemble the XCP for teh maxillary left quadrant
    • expose premolar film then molar film
    • move to the mandibular right quadrant
    • finish by exposing premolar film, then molar film
  19. modifications in paralleling technique - shallow palate
    shallow palate you tilt 20 degrees or less (cause distortion) use cotton rolls, vertical angulation increased by 5-15 degrees
  20. modifications in paralleling technique - bony growths or Torus, Tori
    place film on far side of torus or between tongue and tori
  21. modifications in paralleling technique - mandibular premolar region
    • place film under tongue while tipping it
    • place bite-block firmly on mandibular premolars
    • have patient gently/slowly close together
  22. paralleling technique advantages/disadvantages
    • accuracy, simplicty, duplication
    • Dis - film placement, discomfort