Paralleling Technique Flashcards
What are two other names for the paralleling technique?
•right-angle technique
•long-cone technique
What does FFD stand for?
Focal Film Distance
The paralleling technique is used to expose which radiographs?
-periapical radiographs
-bite-wing radiographs
Why is the rectangular PID recommended by the ADA and American Academy of Oral and Maxillofacial Radiology?
it reduces the amount of radiation the patient receives by as much as 70%, as well as reduces scatter radiation
Central ray
central portion of the primary beam of x-radiation
What are the principles (2) of the paralleling technique?
- receptor is place parallel to the long axis of the tooth
- central beam is directed perpendicular (right angle 90 degree) to both the tooth and receptor
Why must a beam alignment device be used with the paralleling technique
to keep the receptor parallel with the long axis of the tooth
The further the receptor is from the tooth, the greater the ________&________ of the image.
magnification and distortion
Why a longer tube (12-15” FFD) used with the paralleling technique?
a longer beam is less divergent, so it will bring the image back to accurate size
Should the receptor be placed closer to or further from the tooth to achieve parallelism
further from the tooth (closer to the midline)
The x-ray beam diverges in what shape?
Conical
When object-receptor distance is increased, what other distance must also be increased
target-receptor distance
How is exposure time measured?
-in impulses (x-rays are produced in bursts)
-one second is 60 impulses (one impulse every 1/60 of a second)
Describe inverse square law
If the distance between an object and a light source is doubled (X2), the object receives 1/4 as much light
A 16” FFD required ____ times the amount of exposure time as an 8” FFD
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