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What are the 5 steps to imaging process
- -image acquisition
- -image processing
- -image archiving
- -image display
- -image analysis
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what activities are done in image acquisition?
- "unique to each modality"
- Production of x-ray is the same as film/screen and digital and the creation of the image is also the same
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what activities are done is image processing?
- hard copy= film
- soft copy=monitor
images can be switched from soft and hard copy but there will be a loss of resolution
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what activities are done is image archiving?
- (image storage)
- Film screen is stored in a jacket
- Soft copy is stored electronically( if printed can be stored in jacket)
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what activities are done is image display?
- Hard copy (view box)
- Soft copy (monitor) when using a monitor there are several variables to set
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what activities are done is image analysis?
- tech looks at quality of the image
- -density
- -contrast
- -detail
- -distortion
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what is a pyramid problem?
- An acceptable radiograph is the result of multiple factors
- =may have several things affecting one another
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What to tech diagnose for?
Techs diagnose for quality not disease/pathology
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What are the steps in the diagnostic process?
- 1) Narrow the search-look for anything that is not of diagnostic quality (positioning, density, artifacts)
- 2) seek a hypothesis- determine what is causing the problem
- 3) seek more information- validate or disprove the hypothesis
- 4) evaluate the hypothesis
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What is acceptance limits and Explain Wide and Narrow acceptance limits?
- Standards for image evaluation
- wide- more skewed towards darker densities and lower contrast
- narrow-CON- increased repeat rates
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What does high atomic number.. do to absorption and density?
(bone) creates more absorption and a decrease in density.
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What is the visibility of detail?
visible to the eye bc of sufficient density and sufficient contrast so that structures can be seen
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What is the definition of density? in digital what controls density? what is density called when using digital?
blackening of the film. it is controlled by window level. brightness.
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what is the definition of contrast?
Difference b/w adjacent densities?
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How do we determine film has accessible amount of density?
- between OD range of .25 - 2.5
- light=missing information
- dark= received too many photons= to much recorded information
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Would you rather have the film too light or too dark?
Would rather have film to dark than to light.. bc to light you can not see all of diagnostic information
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if you double mAs.. do you double exposures... do you double density??
if you double mAs.. you double exposures.. but do not double density
= formulas are accurate when talking about exposures but not when talking about density
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How much change in density does that have to be in able to see the difference?
30%
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which formula is accurate- distance to intensity or distance to density??
Distance to intensity is accurate
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what is the definition of controlling factors?
controls density in a direct way
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what is definition of influencing factors?
affect density in a indirect way
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What is the controlling factors of density?
mAs
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what is the controlling factor of contrast?
kvp
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what is the reciprocity law?
as long as density and exposures stay the same exposure and density stay the same
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what adjusting density what do you do to mAs?
double or 1/2 mAs
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what adjusts density in digital?
window leveling
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what does kvp do when dealing with the beam?
affects the average energy of the beam
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when is the 15% a variable form from 15-25%?
it is a variable when kvp and thickness of patient are not average
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is focal spot an influencing factor or controlling factor of density and when does it affect density?
it is an influencing factor and it affects density when the tube is broken
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how do you fix it anode heel affect? and how do you use it to your advantage? is it a controlling or influencing factor of density?
- fix it by collimating
- -beam stronger on cathode side. so put thicker anatomy on cathode side.
- - it is an influencing factor
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is the inverse square law and exact or not exact formula? and as intensity increases what does density do?
- yes it is an exact formula.
- - as intensity increase density increase
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is the density maintenance formula exact or not?
not exact.
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as OID increases what does density do?
as OID increase ; density decrease
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as filtration increase what does density do?
filtration increase ; density decrease (collimation)
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What does filtration do to density, intensity and average energy of the beam?
filtration; decrease density, decreases intensity, and increases average energy of the beam.
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what does collimation do to contrast?
collimations increases contrast
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what does filtration due to contrast
filtration decrease contrast
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as grid ratio increase what does it do to scatter clean up, contrast and density?
as grid ratio increases, scatter clean up increases, increase contrast and density decrease
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a decrease in grid frequency does what to scatter absorbed contrast and density?
an decrease is grid frequency increases scatter absorbed and increases contrast and decreases density
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does grid errors and grid cut off increase for decrease density?
decrease density
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an increase in developer temp, emersion time and chemical activity do what to density?
increase density
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As thickness of the anatomical part increases what does attenuation do and what does density do?
as thickness increases, attenuation increases and density decrease
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Composition: as the atomic number increases what does attenuation and density do?
as atomic number increases, attenuation increases and density decreases
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Composition: as tissue density decrease, what does attenuation and density do?
as tissue density decreases, attenuation decreases, and density increases
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what is film speed based on?
it is based on the size of crystals and the thickness of emulsion layer
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what is screen speed?
ability of a screen to produce visible light?
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small phosphor layer and thin layer do what to screen speed? and does what to light and density?
decrease screen speed; creates less light and less density
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what is absorption efficiency?
the ability of phosphors to absorb more photons
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what is conversion efficiency?
how well it converts the x-ray photon into light
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Increased Absorption efficiency and conversion efficiency does that to density?
Increase density
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what is film speed?
the amount of density a film produced for a given amount of exposure
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Visibility of detail?
the image is visible because efficient density and contrast
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T or F: changes to overall density of image will not affect contrast
F: changes to overal density WILL affect contrast
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what is Dynamic Range? and what is it controlled by
contrast as displayed on a monitor. and it is controlled by window width
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What are the adjectives for High Contrast?
- Few shades of Gray
- increased contrast
- short scale contrast
- low KvP (high mAs)
- Black and white radiograph
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what are adjectives for low contrast?
- many shades of gray
- decreased contrast
- long scale contrast
- High kVp (low mAs)
- many grays
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does high or low contrast have more or less diagnostic information?
low contrast. as long as shades of gray are in the diagnostic range
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What is physical contrast?
total range of shades of gray reported on an image
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What is visible contrast?
Range of densities we can perceive with our eyes.
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radiographic Image receptor contrast?
film contrast from the IR
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Radiographic Subject Contrast?
contrast from the patient
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Does Intensity screens make a higher or lower contrast image?
makes a higher contrast image
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when dealing with intensifying screens what effects the contrast of the image? the screen speed or the intensifying screen?
intensifying screens
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what must be done to maximize contrast?
- have the OD range between .25 and 2.5
- if the image is to light or to dark contrast will be decreased
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what is latitude?
range of exposures that produce density in a diagnostic range
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as slope increase what does contrast do?
contrast increases
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if the latitude is wide what does the image have high or low contrast?
low contrast
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if the latitude is narrow what does the image have high or low contrast?
high contrast
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if the developer temp is to high or time in developer is too long or slow replenishment rate was does it cause and what does it do to contrast?
will create fog and decreases contrast
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what does window width control?
contrast
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what does window leveling control?
density
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what factors affect subject contrast?
- kVp
- Amount of irradiated material
- type of irradiated material
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What is the definition of Subject contrast?
the differential absorption of the beam either by through transmission, absorbed or scatter
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what does high kVp do to photon energies?
high kVp creates wide range of photon energies.
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what does low kVp do the the range of photon energies?
low kVp creates a small range of photon energies
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big difference in thickness creates a large a small difference in contrast?
large
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Thin patient
through transmission= black
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thick patient
absorption= white
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thick patient what would it do to scatter and contrast? how could you compensate?
- thick patient would increase scatter therefor lowering contrast.
- collimation creates less scatter therefor them making the contrast of the image better
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High atomic number what does it do to contrast
high atomic number= more photoelectric absorption and high contrast
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Tissue Density increase. what does it do to contrast?
As tissue density increases attenuation increases therefor making higher subject contrast
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What do you look at when evaluation contrast?
- overall density of the image is in diagnostic range
- number or range of densities present within the shades of gray
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When repeating contrast how much change must there be in order for your eyes to see?
30%
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What is the controlling factor of contrast?
kVp
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as kVp increase what happens to contrast?
as kVp decrease what happens to contrast?
- as kvp increases contrast decreases
- as kvp decreases contrast increases
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what are the influencing factors of contrast?
- mAs
- anode heel effect
- distance
- filtration
- beam restriction
- anatomical part
- Grids
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if you have to dark density what does contrast do?
contrast decreases
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if you have too light of an image what does contrast do?
contrast decreases
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Anode heel effect?
more photons on cathode side that on anode side... effects density so it then effects contrast
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If SID increases what does Density do and what does contrast do?
As SID increases divergence increases so density decreases and contrast decreases
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As SID decreases what happens to density and what happens to contrast?
As SID decreases density increases making the film to dark so contrast decreases
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what does an increase in OID do to contrast?
increase in OID creates and air gap which makes scatter miss the film and therefore making contrast increase
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what does a decrease in OID do to contrast?
a decrease in OID creates more scatter therefor decreasing contrast.
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As filtration increases what does contrast do?
as filtration increases contrast decreases= removes photons so less photons hit the beam lighter density decrease contrast
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what does beam restrictors (collimation) do to contrast?
increases contrast. lead in the beam creating less scatter and increasing contrast
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what does increase in patient thickness do to contrast?
increase in patient thickness, increase in scatter, so contrast decreases
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what does an increase in tissue density do to contrast?
increase in tissue density increases scatter and decreases contrast
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as effect atomic number increase what does it do to contrast?
increase bone= more photoelectric absorption so increases contrast
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what do grids do to contrast?
grids absorb scatter and increase contrast
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as grid ratio decreases what does contrast do?
contrast decrease
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what does fog when dealing with the developer do to contrast?
decrease contrast.
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