Extraoral Radiography

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Extraoral Radiography

• Professor Nancy Rivaldo
• Monroe Community College

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Considerations

• Define extraoral
• Indications for use of extraoral
• Define cassette
• What is an intensifying screen?
• Advantage and disadvantage of intensifying
  screens
• What is screen film?
• How is speed/intensification determined?

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Cont.

• What is a grid?
• What are the 7 common extraoral exposures?
• What is a cephalometric radiograph?
• What are two extraoral exposures commonly used in
  cephalometrics?
• What is the best extraoral exposure for maxillary
  sinus?

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Cont.

• What is sialography?
• What techniques are used to examine the TMJ?

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Extraoral

• Film packet or cassette placed outside oral
  cavity
• Advantages
• --usually easier than intraoral
• --minimal equipment needed
• Indications for use
• --patient has limited opening
• --area to be viewed is larger then can be
  seen on intraoral radiograph

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Cassette

• Light-tight container in which film placed
• Rigid or flexible
• Flat or curved
• Varying sizes
• Should have L or R identification for
  orientation of images in relation to patient

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Cassette--cont.

• Tubeside of cassette placed toward head
• Radiation enters film from opposite side

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Intensifying Screens

• Intensify or increase radiation
• Decrease exposure time
• Coated with a fluorescence substance
• Material responsible for fluorescence called
  phosphors
• Phosphors emit light when irradiated

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Phosphors

• Type of phosphor plays role in speed or
  intensification
• Calcium tungstate produces blue light
• Rare earth elements sensitive to light in green
  portion of light spectrum
• Rare earth elements more efficient in converting
  x-ray energy into light

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Screen Composition

• BASE
• PHOSPHOR LAYER
• REFLECTIVE LAYER
• PROTECTIVE COATING

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BASE

• Structural component upon which other screen
  elements are applied
• Made of polyester
• Provides rigidity to the screen

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REFLECTIVE LAYER

• Coating of white titanium dioxide
• Reflects stray light back to x-ray film
• Increases efficiency and sensitivity
• Contributes to dose reduction

13
PHOSPHOR LAYER

• Contains phosphor materials that fluoresce
• Emit visible light when irradiated

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Screen Film

• Used with intensifying screen (film placed
  between two intensifying screens in cassette
  holder)
• Cassette irradiated, screens convert x-ray energy
  into light, which in turn exposes screen film
• This additional mean of exposing film
  intensifying decrease radiation to patient
• Indirect imaging

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Grid

• Used to prevent scattered radiation from reaching
  film
• Series of narrow lead strips separated by spaces
  of low-density material
• Act as cleaning device to improve image contrast

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Lateral Oblique (Lateral Jaw)

• Film positioned lateral to jaw on side of
  patients face to be examined
• Used with children and patients with limited jaw
  opening
• Examines posterior region of mandible
• View fractures, impactions, salivary stones in
  floor of mouth

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Lateral Skull

• Lateral view of entire skull
• Primary use cephalometrics
• --assess patient profile
• --assist in predicting jaw growth pattern
• --used for measuring arch size changes
• Can also view fractures and pathologic conditions

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Lateral Sinus

• Modification of lateral skull
• Used to examine growths, infections or foreign
  bodies in maxillary sinus

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Posteroanterior of Skull

• Shows entire skull in posterior-anterior plane
• Primary use cephalometrics
• --measure skull growth
• --observe growth abnormalities
• Used to view fractures and pathologic conditions
  of skull in frontal plane

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Posteroanterior of Mandible

• Shows entire mandible in frontal plane
• Used to localize impactions, fractures and
  pathologic conditions

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Posteroanterior of Sinus

• Referred to as Waters View
• Best projection for maxillary sinus
• Used to view fractures of maxilla, malar bone and
  zygomatic arch

22
Submental Vertex

• See structures as if viewer looking upward from
  under patients chin
• Can view condylar heads, base of skull and
  sphenoid sinus
• Used to view fractures and displacements of
  zygomatic arch

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Cephalometry

• Extraoral radiographs of head used for making
  skull measurements
• Purpose is to correlate skeletal growth with
  tooth development and position
• Lateral skull and posteroanterior projection of
  skull most commonly used in ortho surveys

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Hand-Wrist Films

• Used to correlate chronologic age with
• --skeletal age and development
• --dental aged and development
• Based on principle that these bones are good
  indications of skeletal maturation due to the
  many centers of ossification in this area

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TMJ Survey

• TMJ tomography radiographic technique to
  examine joint
• Other radiographs (pan) will show the bone and
  relationship of joint components only (erosions,
  bony deposits)

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Arthrography

• Used for imaging soft tissue components of TMJ
• Radiopaque die injected into joint space
• View condyle, glenoid fossa and joint space

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Transcranial TMJ

• Radiograph taken through or across the skull or
  cranium
• Lindblom technique most common
• Shows glenoid fossa and relationship to condyle

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Sialography

• Examination of salivary gland
• Uses radiopaque dye injected into ducts
• Initial radiograph taken followed by successive
  radiographs to visualize draining of gland