density and contrast in Rad. Flashcards
In density what is the prime factor?
mAs
In density what is the Controlling factor?
mAs
what is density of a radiographic image?
overall darkness of the image
how is scatter related to density?
Directly related (both will either increase or decrease)
what is the relationship between SID and Density ?
Indirectly related ( one increases and the other decreases)
how is patient size and density related?
Indirectly related (one increases and the other decreases)
what happens when a filter is used related to patient exposure?
the filter reduces the amount of photons (mAs) exposing the patients skin.
when filtration is added, what happens to density?
density will increase b/c of kVp condensation
as filtration is added what happens to kVp?
it will need to increase to compensate
when a grid is added what happens to Density?
density wil decrease
focal spot and Density have what relation?
no relation
when a grid is added what happens to scatter production?
nothing will happen to scatter production
when adding a grid what will happen to scatter reaching the IR?
less scatter will reach the IR
As OID increases what happens to Density?
density will decrease
when increasing OID what will happen to scatter production?
nothing will happen
when Increasing OID what happen to scatter hitting the IR?
Density will decrease b/c less scatter will hit the IR
In digital what controls Density?
Window leveling
what is contrast?
difference between adjacent density
what is long scale contrast?
more grays [/////////]
what is short scale contrast?
Black and white [/ ]
for every Inch of OID how much do I increase SID?
7in
Does kVp control contrast in digital?
No
will short or long scale contrast have higher kVp?
Long scale
long scale contrast will have what contrast?
Low rad. contrast
short scale contrast will have what contrast?
High rad. contrast
what controls contrast in digital?
Look-up table ; histogram
what is beam restriction?
collimation
does AEC control density?
no, it will be the density knob
what does beam restriction do to contrast
it will Increase contrast which means [B/W]
when adding bean restriction scatter production will?
decrease
when adding beam restriction is added scatter hitting the IR will?
decrease
what controls contrast in the digital monitor?
Window width= Dynamic rage
as OID increase what happens to rad. contrast?
Increased contrast; [B/W]; short scale
what is the 15% rule?
increase kVp by 2X which increases Density
