Extra Oral Radiography Flashcards
Name extra oral views of cranium and maxilla
Lateral cephalogram
Lateral skull
Occipito mental view
TM joint views
From what direction does the X-ray beam come for a posters anterior views?
From back to film placed at front
From what direction does the X-ray beam come for a antero posterior view?
X-ray beam from front to film placed at back
From what direction does the X-ray beam come for a lateral view?
From side
Describe the radiographic baseline
Outer canthus of eye to external auditory meatus
What does the radiographic baseline represents?
Base of skull
Describe the Frankfort plane
Inferior orbital border to upper border of external auditory meatus
What does the Frankfort plane represent?
Anthropological base line
Describe the maxillary occlusal plane?
ALA of nose to Tragus of ear
What equipment if required for extra oral radiography?
Skull unit Cephalometric unit High intensity, high penetrating beam Cassette with intensifying screen and film Anti scatter grid
What is Compton scatter?
When X-rays pass through tissues and some are scattered
Why is more scattered produced in skull radiography?
Field of the beam is increase therefore more scatter is produced
What does scatter radiation add to?
Background fog= greyer image
What is the purpose of anti scatter grid?
Stops scattered photons reaching film
What is the composition of anti scatter grids?
Narrow strips of lead alternating with plastic
When is a postero anterior film indicated?
Fractures
Cysts and malignancy
Visualisation of posterior body of mandible
Midline can be obscured by spine
Benefits of postero anterior?
Reduced magnification of facial structures
Reduced dose to eyes
When would a reverse Townes be indicated?
Trauma or pathology
Improve visualisation of head and neck of condyle
Describe positioning re. Reverse Townes
Positioned re. PA
X-ray beam angled 30 degrees up
Centred through midline
When would a lateral oblique radiograph be indicated?
Fracture
Pathology of cysts
Assessment of 8s
Specials needs and children who can tolerate bws re. Diagnosis of caries
What are the 3 techniques re. Lateral oblique X-rays?
Isocentric
Dental tube vertical
Dental tube horizontal
When is cephalometric radiography indicated?
Ortho assessment
Pre ortho surgery
What appears on image re. Cephalometric?
Soft and hard tissue
What is the function of the aluminium filter?
Allows visualisation of bone and soft tissue on one film
Name 4 extra oral views of the mandible
Postero anterior
Reverse tommes
Lateral oblique mandible
DPT
