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cassette and IS

QuestionAnswer
function of a cassette portable light proof case for film to protect it from light
name the layered parts of a cassette cassette thats radiolucent,IS, film,IS,cassette w/lead backing
what is the test for poor contact for film and IS wire mesh test for fuzziness, space or poor contact
the IS provides added ________ to the image added density if area of phosphers are blocked there will be a white spot on image
what are some types of holders cardboard like envelope,conventional w/latches,double and single screens like sandwich,CVD cassettes
what are IS used for to amplify incoming x-rays,forms 99% of latent image,reduces PT radiation
how does the IS absorb radiation photoelectric light
what are the two types of luminescence fluorescence-instantaneous and phosphorescence-delayed
what are some names for delayed phosphorescent emission screen lagg or afterglow,,happens w/aging phosphers
what is the IS coated with radiolucent plastic coating
what are the layers of an IS base,relflective layer,phospher layer,protective layer
what is the base of the IS made of polyester plastic 1mm thick has to be flexible,rigid,chemically inert,radiolucent
what is the reflective layer of the IS made of magnesium oxide or titanium dioxide 25mi thick that reflects light back toward film,decreases PT radiation by adding more light to the image
what is the phosphor layer of the IS known as the active layer,converts active photons to light photons
what makes up the protective layer of the IS protective plastic appled to top of phospher to allow cleaning,prevent scratches and build-up of static electricity
what are two factors affecting IS speed resolution controlled by crystal size and density,speed-more phosphors and higher kV more speed but less detail
what are the screen speeds labeled as and the formula Releative SpeedRs1(mAs1)/Rs2=mAs2
why are rare earths the preferred phosphors they have great absorption abilities,intensification factors and conversion of efficiency
two rare earths that offer increased speed and maintain resolution lanthanum and gadolinium
qualities in choosing a phospher for IS not to deteriate rapidly,not a lg amount of light per interaction,low enough atomic number,no afterglow and provide uniform quality
criteria for good recorded detail provided by IS thin layer of crystals,too much will give off too much light
quantum mottle is most often seen in what kind of exam fluoro,an increase in mAs will prevent it
some problems with cassettes are droppping them causes bending and hinges and compression bands to loose contact w/film making images fuzzy
film speed is dependent on the size of the crystals
fast film has more or less crystals more or larger, makes it faster because they need less exposure to be ionized,but grainier images
if the film is too white,not enough density what is the most common fault mAs or kV too low
what is the main function of screens to reduce PT radiation
what are phosphors they convert photon energy into light
what is the criteria for film speed and its down fall thicker phosphor layer,higher absorption,but decreased resolution
the purpose or the back of the cassette being lined with lead is to absorb secondary radiation so not to have back scatter get back to the film
what are artifacts unwanted marks or images on a radiograph
felt padding is for to ensure secure contact w/film
what are intensifying screens thin sheets or layers of fluorescent that is housed in a cassette,x-ray energy is absorbed by material and converted to light
why are two IS seen more often than one one is mostly seen in mamography for fine detail,two increase absorption and receptor sensitivity of image blurring
when is x-ray absorption most probable when photon energy is just slightly higher than k-energy of absorbing material
lanthanum and gadolinium,rare earths, are most used for what reason k-edge of these elements is in the x-ray beam spectrum whichh increase the chance of x-ray interaction and absorption
is speed and sensitivity constant for a an intensifying screen or is there a dependent variable kV selected for specific exams changes speed and sensitivity
purpose of IS is to add ________ on film of x-ray exposure blackening effect
early phosphors such as calcium tungstate emitted a _______ emitter blue
lanthanide series are also called rare earth elements
what are the atomic numbers for the rare earths 57-71 and 39 has same properties
what is the function of the activator mixed with the phosphor layer and name enhance light output in speed and wavelength Terbium and Europium w/Terbium are most used
does x-ray absorption increase or decrease with atomic number of the phosphor increases
quantum mottle is due to non even light emission from the IS,irregular spread of image points
Screen Speed is amount of luminance for a given x-rayex. 200 screen needs half the exposure than a 100 screen
describe relationship of screen speed and light emission direct relation-faster screen,more light emitted for same intensity of exposure
describe the relationship of screen speed and PT dose inverse relation-as speed increases less radiation necessary and radiation decreases, slower screens need more radiation thus upping PT dose
screen speed and density have what type of relation direct-as screen speed increases with the same exposure factors, density increases -as screen speed decreases density decreases
why are rare earths phosphors so much faster than calcium tungstate increased absorption and conversion factors
poor screen contact can be caused by warped,bent or broken cassette
why do some IR contain lead foil to stop backscatter from fogging the film
does the IS need to be protected from light no
poor screen contact could cause blurred image
single IS raise PT dose but are used for better recorded detail
a 200 speed screen with the same technical factors shows less or more density than a 50 screen more density, more crystals to produce density
when comparing a 50 to 100 speed screen which one would require a greater exposure 50 speed less dense crystal thickness to produce image
Principle action of the crystals in IS is to produce x-rays into visible light
rare earths predominently give off what color emittance blue and green
quantum mottle is mostly seen in high or low speed systems high speed, irratic exposure
film speed can be increased by thickness of phosphor layer and adding reflective backing to phosphor layer
resolution can be improved by adding dye to slow speed or using slower speed screen
what is spectral matching to obtain maximum efficiency from a film-screen IR light emitted by screens should correspond to maximum light sensittivity of the film
the amount of x-ray absorption by IS phosphor is dependent upon photo electric effect
resolution is measured in lines pairs per millimeter
what is conversion efficiency ratio of the x-ray energy absorbed by a phosphor to the visible light energy emitted
the front of cassette must be covered by a light tight substance that is homogeneous and radiolucent to keep one density through out
describe the affect of density because of thickness layer of phosphor SMALLER crystal size, less dense layer will darken smaller area of a film-LARGER more density of crystals will darken or produce more larger area of darkness to film
poor contact between film and IS increases or decreases image density decreases
when screen speed is increased should technique be increased or decreased to maintain density decrease technique with higher more dense layers of phosphor IS
why are rare earths mixed with an activator like Terbium they do not fluoresce well
describe the intensification facor of IS increase kV more absorption of x-rays in screen, more intensification
calcium tungstate has a conversion efficiency of____% and rare earths are between ______% 5% for calcium tungstate and 15-30% for rare earths
Created by: mharvey