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Screens

Screen review

QuestionAnswer
what is the purpose of intensifying screens converts small quantity of xrays to larger quantity of light photons
what are the advantages of intensifying screens -less pt dose -less wear and tear on the euipment
what is the disadvantage of intensifying screens low spatial resolution
how are screens constructed -base layer -reflective layer -phosphor/active layer -protectcive coat
functions to provide mechanical support for phosphor base layer
-redirects isotropically emitted light to film -uses 2x light, so it decreases pt dose, but loses spatial resoltin -detail screens use yellowish/brown light absorbing dye to absorb spread of long wavelength light which improves spatial resolution reflective layer
isotropic propagation light emitted in all directions
converts xrays to light/intensification phosphor or active layer
what color light would calcium tungstate phosphor give off blue
what color light would a pure rare earth phosphor give off green
when rare earth phosphors are combined with additional elements what color do they give off blue violet
what are the three rare earth phosphors -gadolinium -lanthanum -yitrium
between rare earth phosphors and calcium tungstate which has a higer DQE and conversion efficiency rare earth
as screen speed increases, does it give off more or less light more
what is the advantage of a fast speed screen less dose
what is the disadvantage of a fast speed screen less spatial resolution
what size crysatls give more speed large
do you have more speed with thick or thin emulsion thick
do you have more speed with or without a reflective layer with
what does excessive heat do to the speed of your screen slows it down
what is the test for resolution line pair test(line pair bar phantom)
what is spectral matching matching the color light given off by the screen to film that is sensitive to that color
clumping of phosphor causes what screen structure mottle
clumping of crystal in film causes what film graininess
low mas will cause what quantum mottle
what can cause poor film-screen contact -worn felt -broken hinges or latches -foreign matter -warped cassettes -bent frame -trapped air(transitory-comes and goes)
what does poor film-screen contact look like on a film blurry spot
what is the test used to detect poor film-screen contact wire mesh test
fluorescence emits light only while stimulated
phosphorescence emits light for short period after stimulation has ended
photostimuable gives of luminescence twice
spatial resolution/resolving power ability to image an object faithfuly
speed/sensitivity/coversion efficiency how fast a minimal exposure is converted to light
high DQE allows us to do what lower our mas
what will happen if you use a high speed screen with a technique for a slow speed screen you will over expose the film(therefore you would underexpose film if you used a low speed screen with a high speed technique)
if you only cared about pt dose what film/screen combo would you use fast/fast
if you only cared about image quality or resolution what film/screen combo would you use slow/slow
if you wanted a good balance between dose and resolution what are your film/screen options -fast/slow -medium/medium
what is the main purpose of a film cassette -light tight -good film/screen contact
what is the purpose fo the protective coat -protects from abrasions,stains,and scratches(white line artifact) -provides cleaning surface
how is tube side of cassette constructed -radioluscent -carbon fiber or bakelit
how is backside of cassette constructed -radiopaque -w/ lead foil to prevent backscatter
what is the primary difference between the imaging plate cassette and film cassette blocker
what is spatial resolution in film screens dependant upon -phosphor crystal size -phosphor layer thickness -phosphor concentration -type of phosphor -reflective layer -yellow light absorbing dye
what is the modular transfer function to measure resolution measures information lost between subject an IR caused by light diffusion
what is the line spread function to measure resolution microdesitometer to measure the film screen combos ablility to accurately measure boundries of images
what is intensification factor exposure with a screen vs. exposure w/o a screen
Created by: bigad1982