Principles of Shadow Cast Flashcards
SOD should be as ____ as possible. FOD (object receptor dist) should be as _____ as possible.
long, short
long axis object should be ____ to receptor. Central ray should be ____ to receptor.
parallel, perpendicular
focal spots that are ____ produce sharper image
smaller
Long x-ray to object dist because?
xrays less divergent and less magnification
short object-receptor bc?
less mag, sharper
Parallel object-film b/c?
decreases distortion, improves sharpness
Too short = beam ___ angulation? Too long = beam ____ angulation
over, under
Parallel vs bisecting angle method?
parallel - less distortion
Detail means (2)
sharpness and resolution
factors affecting detail?
6
focal spot size SOD FOD movement of patient film speed density
Density effect?
Thickness
Density of anatomy
Atomic #
filtration
collimation
distance
artifacts
LOWER density
…more obstacles
Density means?
lighter image is decreased Optical Density (less xrays)
darker image is increased OD
Density effect?
kVp increase
mA increase
exposure time
faster film
Processing: time, temp, concentration
HIGHER density
…more power, more processing, longer exposure
How does thickness, density of material, and its atomic # affect contrast? Beam quantity (mA)
greater contrast - more information
How does kVP affect contrast?
filtration
mean energy?
All lower contrast - because everything passes through at high energies
How can processing effect contrast?
improper time, temp, chemical comcentration
What is the right angle technique?
2 radiographs 90 degrees to each other at area of interest
SLOB rule?
same lingual opposite buccal
object moves in same direction as tube (entire thing, NOT which way its pointing) –> lingual (axis rotates between buccal and lingual objects)
Buccal object rule (BOR) -
in a pair of objects image, image of buccal object moves in the same direction that x-ray beam is directed
If the camera is shooting to the left, the buccal object will “move” to the left. Opposite of SLOB rule–the way its POINTING not the way it moves (which are opposites). If the camera moves right it points more left.
