radiographic screens and digital imaging Flashcards Preview

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Flashcards in radiographic screens and digital imaging Deck (49)
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1

What is a cassette

the device that provides a light tight film holder and rigid support for film, as well as an intensifying screen

2

The cassette contains two intensifying screen, one on each side of the inside of the cassette. What is their purpose?

this doubles the film exposure obtained with a given x-ray exposure, thus reducing the amount of exposure to the patient

3

What type of film is used inside an X-ray cassette?

dual emulsion

4

What is the function of the padding in the pack of a cassette?

it ensures that there is a light positive pressure exerted on the film when the cassette is closed so that there is optimal film/screen contact at all points on the film

5

How do intensifying screens double the film exposure obtained with a given x-ray?

They are coated with phosphors, which are fluorescent crystals that give off light when exposed to x-rays
this is the property of luminescence that creates 99% of the x-ray image

6

The process of glowing only while being excited (such as during ionizing radiation) that will cease glowing at completion of exposure

fluorescence

7

luminescence that demonstrates afterglow (continues to flow for a period of time after the exposure to radiation has ceased)

phosphorescence

8

the emission of light from a substance bombarded by radiation

luminescence

9

what does the term radio parent mean?

does not have a habit of absorbing X-rays

10

What is radioparent in the X-ray cassette?

the cassette face

11

What is the reflective layer of screens in a cassette made of?

titanium oxide

12

What is the function of the reflective later of cassette screens?

it redirects light created during exposure back towards the film

13

Edison discovered calcium tungstenate to be able to glow efficiently when exposed to radiation. This material was the gold standard in X-ray technology for a long time, but has been replaced with what rare earth phosphors?

gadolinium
lanthanum
yttrium

14

The base layer of screens in mostly made of

polyester or cellulose triacetate, which are radioparent, chemically inert, tough and flexible

15

What creates "faster" screens?

thicker phosphor layers and larger crystals in the phosphor

16

thicker phosphor layers and larger crystals in the phosphor result in

lower detail than thinner phosphor layers and smaller crystals but greater speed of x-ray exposure

17

the portion of electromagnetic spectrum the film is most sensitive to?

spectral sensitivity

18

Spectral sensitivity should match what?

the spectral emission of the screens used in the film

19

What is the formula for adjusting mAs for changing screen speed

(speed1/speed2) x mAs1 = mAs2

20

What is spectral emission

the color of light emitted by a phosphor

21

What is the protective layer of the screen

a thin transparent supercoat consisting of gelatin that protects the the emulsion of the phosphor on the film

22

How often should screens be cleaned?

monthly if films are taken every day
quarterly if films are taken once a week

23

What is screen speed?

the efficiency of a screen in converting x-rays to light

24

greater screen efficiency =

less exposure = faster screen

25

A screen with a speed of 200 would be twice as fast as a 100 speed screen and require _____ as much exposure

half

26

What screen speed is used for general purpose radiography?

400-600

27

What screen speed is used for extremity or other detailed radiography?

100

28

big crystals in thick layer =

fast exposure, lower detail

29

small crystals in thin layer =

slow exposure, greater detail

30

How do you calculate the change in technique needed to create a film of equal density on two different system speeds?

(system speed 1/system speed 2) x mAs 1 = mAs 2