Extraoral Radiography Professor Nancy Rivaldo Monroe Community College
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?
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?
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
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
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
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
BASE
Structural component upon which other screen elements are applied
Made of polyester
Provides rigidity to the screen
REFLECTIVE LAYER
Coating of white titanium dioxide
Reflects stray light back to x-ray film
Increases efficiency and sensitivity
Contributes to dose reduction
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
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
Lateral Oblique (Lateral Jaw)
Film positioned lateral to jaw on side of patient’s 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
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
Lateral Sinus
Modification of lateral skull
Used to examine growths, infections or foreign bodies in maxillary sinus
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
Posteroanterior of Mandible
Shows entire mandible in frontal plane
Used to localize impactions, fractures and pathologic conditions
Posteroanterior of Sinus
Referred to as Waters View
Best projection for maxillary sinus
Used to view fractures of maxilla, malar bone and zygomatic arch
Submental Vertex See structures as if viewer looking
upward from under patient’s chin
Can view condylar heads, base of skull and sphenoid sinus
Used to view fractures and displacements of zygomatic arch
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
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
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)
Arthrography Used for imaging soft tissue
components of TMJ
Radiopaque die injected into joint space
View condyle, glenoid fossa and joint space
Transcranial TMJ
Radiograph taken through or across the skull or cranium
Lindblom technique most common
Shows glenoid fossa and relationship to condyle