Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Screens
Screen review
| Question | Answer |
|---|---|
| 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
Popular Radiology sets