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29 Cards in this Set

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The active layer of the readiographic intensifying screen that emits light
phosphor
Examples of rare earths
*gadolinium
*lanthanum
*yttrium
Purpose of cassette with screens
reduces radiation dose
Intercepts light headed in other directions and redirects it to the film.

Increases the efficiency of the radiographic intensifying screen, nearly douling the number of light photons reaching the film.
reflective layer
Activates rare earths
Turbian
Any material that emits light in response to some outside stimulation.
luminescent material/phosphor
The emitted visible light from phosphor
luminescence
Two types of luminescence
*fluorescence
*phosphorescence
When visible light is emitted only while the phophor is stimulated
fluorescence
When the phosphor continues to emit light after stimulation
phosphorescence
Undesirable phosphorescence in an intensifying screen
screen lag/ afterglow
Occurs when an outer-shell electron is raised to an excited state and returns to its ground state with the emission of a light photon.
luminescence
Three primary characteristics of radiographic intensifying screens
*screen speed
*image noise
*spatial resolution
A relative number that describes how efficiently x-rays are converted into usable light.
screen speed
The faster the screen speed, the _______ the resolution.
lower
Information concerning patient dose
(IF)intensification factor
IF equation
Exposure required without screen / Exposure required with screens
Screen speed is determined by
*the # of xrays interacting with the phosphor

*how efficiently xray energy is converted to visible light that interacts with film
Radiographic conditions controlled by the radiologic technologist.
*radiation quality
*image processing
*temperature
*film speed
*screen speed
Two characteristics why rare earth screens have increased speed.
*higher DQE
*higher CE
The percentage of x-rays absorbed by the screen.
(DQE)Detective quantum efficiency
The amount of light emitted for each e-ray absorbed.
(CE)Conversion efficiency
Calcium tungstate screen has a DQE of _____ and a CE of ____.
20% and 5%
Measured in a number of ways and can be given a numerical value.
spatial resolution
Screen blur is ________ in thinner screens.
reduced
Lead lines separated by interspaces of equal size.
line-test pattern
Reduction in spatial resolution is greater when phosphor layers are _____.
thick
Reduction is greater when crystal size is ______.
large
Screen-film contact can be checked by radiographing a ______. If there are any darker areas of blurring, screen-film contact is _____.
wire mesh, poor