Extra-oral Radiography Flashcards

1
Q

Images relating to the mandible?

Images relating to the maxilla and cranium?

A

Images relating to mandible:

  • postero-anterior mandible
  • lateral oblique mandible
  • DPT

Images relating to maxilla and cranium:

  • lateral cephalogram
  • occipito-mental views
  • sailography
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2
Q

Describe some positioning landmarks:

A
  • radiographic baseline: line from outer canthus of eye to external auditory meatus (EAM) - represents base of skull
  • frankfort plane: inferior orbital border to upper border of EAM - aka anthropological base line (used in DPT)
  • maxillary occlusal plane: ala of nose to tragus of ear - used in CBCT
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3
Q
A
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4
Q

What is an anti-scatter grid?

A

Anti-scatter grid:

  • stop photons scattered in patient reaching film
  • avoids degrading and reducing contrast
  • narrow strips of lead alternating with plastic
  • fixed or moving
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5
Q

List some things to consider when positioning a patient for an extra-oral radiograph:

A
  • position of patient relative to film
  • position of x-ray beam relative to patient
  • angle of x-ray beam relative to film
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6
Q

Indications for a postero-anterior mandible view?

Why is this method preferred?

A

Postero-anterior view:

  • fractured mandible - shows medio-lateral displacement
  • cysts and malignancy causing medio-lateral expansion or bone destruction
  • good visualisation of posterior belly and ramus
  • limited visualisation of head/neck of condyle
  • midline can be obscured by spine
  • usually requested in conjunction with a DPT
  • reduced magnification of facial structures
  • reduced dose to eyes
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7
Q

How should a patient be positioned for a PA mandible view?

A
  • pt faces film
  • nose and forehead touches film holder
  • radiographic base line - horizontal
  • aim centre of beam at midline of pt at mid ramus height
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8
Q

Indications for lateral oblique jaw radiography?

A
  • fracture of body, ramus and condyle
  • pathology e.g. cysts
  • assessment of wisdom teeth (always request a DPT first)
  • dental assessment in special needs patients
  • caries in children who cannot tolerate BWs
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9
Q

What are the three techniques used to take a lateral oblique jaw radiograph?

A
  • isocentric positioning using a skull unit
  • dental tube with vertical angulation
  • dental tube with horizontal angulation
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10
Q

Indications for cephalometric radiography and some points regarding the images:

A
  • orthodontic assessment
  • pre-orthognathic surgery
  • can only be done using cephalostat
  • pt positioned with rods in ears to gove standardised positioning
  • image must be reproducible
  • must have means of calculating amount of magnification or calibrating the digital image
  • must be able to visualise soft and hard tissues
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11
Q

How can soft tissues be imaged on a lateral cephalogram?

A

Aluminium filter:

  • positioned over anterior part of face
  • designed to attenuate the beam in anterior facial region
  • allows visalisation of bone and soft tissue on one film, despite relatively high exposure factors needed for the facial bones
  • if digital, tissues made visible by software
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12
Q

Indications for occipito-mental views:

A
  • facial bone fractures - zygoma, le-fort fractures and orbital blowout
  • pathology - limited use in sinus disease, only used rarely
  • different angulations allow us to view different areas of complex anatomy: OM 0, 10 and 30 most common
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