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?

Cont.

What is sialography? What techniques are used to

examine the TMJ?

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

Cassette--cont.

Tubeside of cassette placed toward head

Radiation enters film from opposite side

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

Screen Composition BASE

PHOSPHOR LAYER

REFLECTIVE LAYER

PROTECTIVE COATING

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

PHOSPHOR LAYER

Contains phosphor materials that fluoresce

Emit visible light when irradiated

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

Sialography

Examination of salivary gland

Uses radiopaque dye injected into ducts

Initial radiograph taken followed by successive radiographs to visualize draining of gland