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Exposure Unit 2

Film, Inten. Screens, and CR/DR

QuestionAnswer
What type of film is only used for display and not used for image acquistion? laser film
What type of film does not use an intensifying screen and is now obsolete? direct exposure
what are the layers in film? base, emulsion, adhesive layer, protective/t-coat/supercoat layer
what is the difference between single and double emulsion? double emulsion layer has 2 emulsion layers and single only has 1. single emulsion film has glossy non-emulsion side and a dull emulsion side.
what is the function of the base of the film? supports the image, tinted blue for preventing eye strain.
What is the base of the film made out of? polyester
what is the emulsion layer made out of? silver bromide (AgBr) or silver halide crystals dissolved in gelatin
T/F: a film's adhesive layer glues the protective coat to the emulsion. False; adhesive layer glues the emulsion to the base
T/F: silver ions have a positive charge. true
T/F: silver halide crystals are made of silver bromide and silver iodide true
T/F: the emulsion side of a single emulsion film can be identified in a darkroom because it is glossy or shiny false; the emulsion side is the dull side
T/F: As film/screen speed increases, recorded detail decreases. True; recorded detail is the same thing as sharpness
T/F: all of the folling are examples of intensifying phosphors that are not made from rare earth elements: calcium tungstate, zinc sulfide, barium platinocyanide, and barium lead sulfide true
T/F: If the tech uses the tech factors for a high speed film/screen but accidently used a slow speed film/screen, the image produced will be overexposed. False; it will be underexposed. because high speed film/screen factors use low mAs, but if low mAs is used on slow speed film/screen will be underexposed. This is because slow speed film/screens use smaller crystals and won't produce enough density.
T/F: Rare earth phosphors have a greater conversion and absorption efficiency compared to calcium tungstate phosphors. true
T/F: If films are not spectrally matched to the light emitted by the intensifying phosphor, the film will be excessively dark. False; the film will be excessively light.
What does it mean by spectrally matching? refers to correctly matching the color sensitivity of the film to the color emission of the intensifying screen. So example, use blue-sensitive film with blue light-emitting screens.
define latent image. invisible image that is on the film after it was exposed to light. Hasn't been processed yet.
What is the Gurney-Mott theory? exposure of the silver bromide crystals in the film emulsion by light or xray photons creates the latent image and initiates the conversion process from a latent to a manifest image
What must be present in the silver bromide crystal for the gurney-mott theory to occur? sensitivity speck (sulfide contaminant)
When exposure/photons causes ionization of the AgBr crystals how is this represented in an equation? AgBr + photon --> Br (neutral) + e- + Ag+ (postively charged)
When the trapped e- attracts to the Ag+ ions around the sensitivity speck how is this wrote into an equation? e- + Ag+ --> Ag (black metallic silver)
What are the 2 major steps in film processing? reduction and fixation
What happens in reduction? adds more e- to exposed sensitivity specks and produces more black metallic silver. Unexposed crystals are not reduced to black metallic silver.
What happens in fixation? neutralizes the developer & stops the reduction process. dissolves & removes unexposed/underdeveloped crystals
How is film speed increased? increasing photon absorption in the emulsion layer
What are ways to increase film speed in the emulsion layer? more AgBr crystals, thicker emulsion, double emulsion.
In general, as film speed is increased what happens to blur and recorded detail? film speed increases; recorded detail decreases; blur increases
Intensifying screens are used to: a) decrease patient exposure b)increase recorded detail c)increase film latitude d)decrease contrast A
What is the relationship between screen speed, light emission and patient dose? the faster an intensifying screen is the more light is emitted for the same intensity of the exposure. As screen speed increases, less radiation is needed and patient dose decreases.
Which of the following is the latent image center for radiographic film? a)phosphor layer b)polyester base c)detector element d)sensitivity speck D
The ability to emit light only when stimulated by xrays is known as what? a)phosphorescence b)sensitometry c)conversion efficiency d)fluorescence D
Who invented the calcium tungstate intensifying screen? Edison
In intensifying screens, what are the layers? furthest from the film: base, reflecting OR absorbing layer, phosphor layer, and protective layer
How does using a reflective layer lower patient dose? reflective layer reflects light back towards the film producing more density; therefore less mAs is needed and lowers pt. dose.
Would you use a reflective layer or absorbing layer for detail work exams? absorbing layer, because it produces less density and uses a slower speed system. If a reflective layer was used there would be too much density.
Name some rare earth phosphors. Gadolinium, Lanthanum, Yttrium
What is the difference between fluorescence and phosphorescence? phosphorescence is undesirable because it continues to glow after exposed to light photons. Fluorescence only glows when exposed to light photons and then stops when exposure is over.
What color light does calcium tungstate emit? violet-blue
What color light do RE materials emit? green-blue
What does intensifying screen efficiency determine? it determines the amount of light that exposes the film.
As screen efficiency increases what happens to film density? film density increases
T/F: As screen efficiency increases pt. dose decreases. True; as screen efficiency increases, speed increases and that means more density is produced and less radiation is used to produce density.
What is the Intensification Factor? IF= exposure required without a screen/exposure with a screen
An abd. was taken with a 200RS screen at 75kV @ 50mAs. This results in the ESE of 200mR. A similar exam was taken w/o screens and resulted in ESE=6400mR. What is the IF of the film screen combination? IF=6400/200= 32
which speed system is normally used for detail and extremity work? slow speed
which speed system is normally used for abd. and bucky procedures? fast speed
When RS# increases, what happens to film density, patient dose and sharpness? Increasing the RS# means using a fast speed system where less mAs is being used lowering patient dose, film density is increased because there is bigger crystals. Sharpness decreases because of the fast film speed.
The rad. dept. is upgrading its system from 100 to 500 speed system for CXR. If a 10 mAs was used previously what must the new mAs be with the 500 speed system? (mAs1/mAs2)divided by (RS2/RS1) the new mAs would be 2. If 10mAs was used with the 500 speed system the image would be overexposed because 2 mAs was the new needed factor to maintain density.
When converting from film/screen system to a CR system how much should you adjust your tech factors? adjust your tech factors as if converting to a 200RS#.
what 3 things do intensifying screens depend on? absorption efficiency (DQE), conversion efficiency (CE), emission efficiency
what is DQE? absorption efficiency; the ability of phosphor layer to absorb xrays.
What has a better DQE, rare earths or calcium tungstate? rare earths
Created by: mokapis