Image Quality Factors Flashcards
what are the image quality factors
density
contrast
detail
distortion
the degree of blackening of a radiograph
density
one of the 2 properties that make visibility of detail
density
density is also known as
optical density
density-more visible when the crystal’s in the film emulsion are converted to_ in the developer solution
black metallic silver
when deciding between a film that is too dark or too light, choose
the dark film
What is the controlling factor of density
mAs
any combination of mA and time that will produce the same mAs will produce the same density
reciprocity law
the min. change necessary to have any effect on density is the shift your mAs by
30% rule
30%
relationship between mAs and density
directly proportional relationship
as mAs increased, density
increases
mAs is decreased, density
decreases
as kV increases, there is a _between the anode and cathode
greater potential difference
when the potential difference is higher, the electrons strike the anode in _ 3’s and with _ energy and produce _ x-rays
greater
greater
more
directly effects density, but not in a proportional relationship
kV
as kV increases, density
increases
as kV decreases, density
decreases
an increase of 15% kV will double density and a decrease in kV of 15% will half the density
15% rule
intensity of the beam is greater at the cathode because of the anode heel effect
anode heel effect (anode can be ^ to 45% weaker)
if you increase your distance, you must increase your exposure factors to maintain the same density (exposure)
density (exposure) maintenance formula
mAs1=D1 2
—————
mAs2=D2 2
the intensity (density, exposure) of the beam is inversely proportional to the square of the distance
inverse square law
if distance is doubled, intensity decreases _ times
4
if distance is halved, intensity increases _ times
4
this variation is from the divergence of the beam as it travels through space
I2=D1 2
as filtration increases, density decreases
(a low energy photon most likely would not make it to the IR, but if it did it would add density. _ is removing those low energy photons before they can reach the IR)
filtration
filtration
collimation reduces the total number of photons. This reduces scatter, reduces scatter, reducing densities on the film
beam restriction
inverse relationship between part thickness and density (as prt. thickness increases, density decreases
anatomical part
grids absorb scatter, which would add exposure and density to the IR (the higher the grid ratio, the less the density)
Grids
the faster the film/screen speed, the more density the IR will receive (as speed increases, density increases)
IR
for filtration what affects the quantity
HBL/ 1/2 value layer
for filtration what affects qualty
beam hardening
as developer temp increases, density
increases
as immersion time increases, density
increases
as replenishment rate increases, density
increases
as mAs increases, density
increases
as kV decreases, density
decrease
as distance increases, density
decreases
as filtration decreases, density
increases
as beam restriction decreases, density
increases
as grid ratio increases, density
decreases
as film/screen speed decreases, density
decreases
as processing increases, density
increases
