Chapter 26: Extraoral Imaging Flashcards
Types, Principles, Equipment and Guidelines of Extraoral Imaging
How is the central ray of the x-ray beam positioned for a transcranial projection?
- toward a point 2 inches above and 0.5 inches behind the opening of the ear canal
- downward and forward to be centered on the temporomandibular joint
Define the term: orbit
the bony cavity that contains the eyeball
How is the image receptor positioned for a Waters projection?
- perpendicular to the floor in a receptor-holding device
- long axis of the receptor is positioned vertically
Define the term: zygoma / zygomatic bone / malar bone
the cheekbone (appears as a diffuse radiopaque band posterior to the zygomatic process of the maxilla)
How is the central ray of the x-ray beam positioned for a Reverse Towne projection?
through the center of the head and perpendicular to the image receptor
Define the term: lateral jaw projection- body of the mandible
an extraoral projection used to evaluate the posterior body of the mandible in order to evaluate impacted teeth, fractures, and lesions located in the body of the mandible
How is the image receptor placed for a lateral cephalometric projection?
- perpendicular to the floor in a receptor–holding device
- long axis of the receptor is positioned horizontally
Define the term: extraoral image
- an image that results when an image receptor is placed outside the mouth and is exposed to x-rays
- used to examine large areas of the skull or jaws
Define the term: extraoral
outside the mouth
What is the proper position of the patient’s head for a lateral jaw projection of the ramus of the mandible?
- tipped approximately 15 degrees toward the side being images
- the chin is extended and elevated slightly
Define the term: perpendicular
intersecting at or forming right angles
List the four classifications of extraoral projection techniques.
- lateral jaw imaging
- skull imaging
- extraoral bite-wing imaging
- temporomandibular joint imaging
Define the term: transcranial projection
an extraoral projection used to evaluate the superior surface of the condyle and the articular eminence or to evaluate the movement of the condyle when the mouth is opened and to compare joint spaces
Define the term: midsagittal plane
an imaginary line or plane passing through the center of the body that divides it into right and left halves
Define the term: glenoid fossa
a concave, depressed area of the temporal bone where the mandibular condyle rests
What is the proper position of the patient’s head for a lateral jaw projection of the body of the mandible?
tipped approximately 15 degrees toward the side being imaged, with the chin extended and slightly elevated
How is the image receptor positioned for a posteroanterior projection?
- perpendicular to the floor in a receptor-holding device
- long axis of the receptor is positioned vertically
Define the term: dental imaging
the creation of digital representation of anatomic structures for the purpose of diagnosis
How is the patient’s head positioned for a posteroanterior projection?
- the patient faces the receptor with the forehead and nose touching the receptor and head centered over the receptor
- the midsaggital plane is aligned perpendicular to the floor
- the Frankfort plane is aligned parallel to the floor
Define the term: Frankfort plane
the imaginary plane that intersects the orbital rim of the eye and opening of the ear
Define the term: maxillary sinuses
paired cavities or compartments of bone located within the maxilla and located superior to the maxillary posterior teeth (appear radiolucent)
How is the image receptor positioned for a lateral jaw projection of the body of the mandible?
- flat against the patient’s cheek and centered over the body of the mandible
- the patient must hold the receptor with their thumb placed under the edge
Define the term: Waters projection
an extraoral projection used to evaluate the maxillary sinus area
Define the term: nasal cavity / nasal fossa
a pear-shaped compartment of bone located superior to the maxilla (appears radiolucent)
How is the central ray of the x-ray beam positioned for a lateral jaw projection of the ramus of the mandible?
- directed to a point posterior to the third molar region on the side opposite the image receptor
- directed upward -15 to -20 degrees and centered on the ramus of the mandible
- perpendicular to the image receptor
Define the term: parallel
moving or lying in the same plane; always separated by the same distance and not intersecting