Image Geometry Flashcards
Increasing the OID does what?
increases the magnification
increasing the SID does what to magnification
decreases magnification
image sharpness is effected by what 3 things?
- Focal spot size
- Object image distance
- Source image distance
What is penumbra?
penumbra is image sharpness caused by photons
the photons from different origins converge to a single spot on the anatomy, then diverge from that point as they pass from anatomy to film, creating multiple shadows of the exact same anatomy in slightly different places on the film creating the fuzzy boarders
Penumbra increases most rapidly with increasing what?
OID
Inverse square Law?
Intensity 1/ intensity 2 = distance2 squared/ distance 1 squared
what is the outcome of the inverse square law
the outcome of the inverse square law is the intensity change of the beam from the original
What is the mAs rule?
mAs1/mAs2=Distance1 squared/distance2 squared
mAs varies directly with what?
square distance
what is the answer you get with the mAs formula used for?
it is the new mAs you will use in the X-ray suite. it is a more direct way of using the theory of inverse square law to obtain a useful answer
SID 40-56 do what to mAs
multiply by 2
SID 40-72 do what to mAs
multiply by 3
SID 40-80 do what to mAs
multiply by 4
Size distortion is always in the form of what?
always in the form of magnification enlargement
magnification is due to divergent beam
decreasing SID or increasing OID will cause greater magnification distortion
what causes magnification distortion the fastest?
OID
