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Chapter 13
SWGTC-R/T-Chapter 13-Wallace-Intensifying Screens
Question | Answer |
---|---|
Two parts of an intensifying screen. | base and an active layer |
What is the base of an intensifying screen made of? | piece of cardboard or plastic |
Why does the base have a white reflective surface? | to direct light given off by the intensifying screen back to the film. |
Layers of an intensifying screen | base, reflecting layer, active layer |
what is the active layer of an intensifying screen made of? | microscopic crystals of a phospor suspended in a matrix |
What do the phospors do? | give off light when struck by the x-ray photons |
In areas where not a lot of radiation got through the patient, the light from the phospors will ______________________. | not be very bright. |
areas that are exposed by only a little light will develop as a ____________. | light grey tone or white. |
isotropically | in all directions |
ability of a material to giveoff light when struck by x-rays. | flourescence |
_______________ is a problem that can occur in older intensifying screens. | phosphorescence |
phosphorescence | continued light emission after the x-rays have been turn off |
phosphorescence causes _____________ density | increased |
Fast screens emit __________ than slower screens. | more light |
The density is greater in _________ screens. | fast |
___________ screens decrease patient dose, but also cause a decrease in ______________. | fast, recorded detail |
Poor screen contact _____________ recorded detail. | reduces |
Why is the wire mesh test performed? | to check for areas of poor screen contact |
Two types of intensifying screens used today. | calcium tungstate and rare earth |
this screen's phospors emit a blue-violet light hen struck by x-ray photons | calcium tungstate |
This type of intensifying screen emits a yellow light when struck by x-ray photons. | rare earth |
This type of intensifying screen is able to produce about the same amount of recorded detail as the other, but does so with a reduced radiation dose to the patient. | rare earth |
True/False: It is not neccesary to change exposure factors when changing screen speeds. | False: exposure factors must be changed to prevent the film from being too light or too dark. |