FILM SCREENS HIGH YIELD

Question 1

what is the significance of intensifying screens that fluoresce?

Answer 1

they absorb x-rays and emit visible light

Question 2

what image is produced from intensifying screens used with x-rays?

Answer 2

image is inverted

bones are dark

Question 3

what is the function of intensifying screens?

Answer 3

decrease dose reduces patient dose 20-50x

shortens exposure times

makes thicker body parts easier to image

Question 4

what affects the dose of intensifying screens?

Answer 4

intensifying factor

IF=exposure required w/o screens/exposure required w/ screen

30-50 sec

Question 5

what are the disadvantages of intensifying screens?

Answer 5

decreases sharpness

any gaps allow more light to spread and fog occurs, not good

Question 6

what are the advantages of intensifying screens?

Answer 6

shortens exposure time

allows flexible kVp and contrasts adjustment

• decrease mAs
• decreases tube heat
• increases tube life

Question 7

what are the layer of intensifying screens?

Answer 7

base-made of plastic

reflecting or absorbing layer-made of titanium dioxide

phosphor layer-varies in thickness

protective layer-plastic cover that touches the film

Question 8

what is the significance of the phosphor layer?

Answer 8

varies in thickness

converts x-ray energy to visible light

Mae of calcium tungsten or rare earth elements

Question 9

what are the types of elements used as film screens?

Answer 9

calcium tungstate

rare earth elements

Question 10

why is calcium tungstate significant for screen type?

Answer 10

produces blue light

3-5% conversion efficiency

Question 11

why are earth elements significant for screen type?

(Gadolinium Oxysulfide, Lanthanum Oxybromide, Yttrium Oxysulfide) what colors do these produce

Answer 11

speed, more efficient

gadolinium
-green visible light

lanthanum
-blue visible light

gadolinum + yttrium
-blue-green visible light

Question 12

what are considerations for screen type?

Answer 12

elements

single vs double

screens
absorption efficiency

Question 13

single vs double screens?

Answer 13

single screens are cheaper, better detail but slower

double screens are fast, increase speed by 2 h/e, cross over happens decreasing detail

Question 14

in terms of absorption efficiency for screens, which one has the highs absorption?

Answer 14

pair of lanthanum screens

60% absorption

Question 15

what are the two types of absorption efficiencies?

Answer 15

absorption

conversion

Question 16

how do we increase screen speed? *any affects of this increase?

Answer 16

double number of screens

increases phosphor layer thickness

increase phosphor crystals

use reflective backings

*decrease of detail

Question 17

different films for different screens?

types of each

Answer 17

spectral matching

• orthochromatic film
• -requires red safelight
• blue-sensitive
• -requires amber safelight

film emulsion layer

Question 18

films that have screens will have _____?

Answer 18

very thin emulsion layers

Question 19

screen film properties?

Answer 19

thin emulsion
high contrast
short scale
low latitude
enhanced light sensitivity

Question 20

non screen film properties?

Answer 20

thick emulsion
low contrast
long scale
long latitude
enhanced x-ray sensitivity