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Rad Exposures > Radiographic Intensifying Screens > Flashcards

Radiographic Intensifying Screens Flashcards

1
Q

What are Intensifying Screens?

A

A device that converts the x-ray beam energy into visible light

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2
Q

What converts the x-ray beam into visible light?

A

Intensifying Screens

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3
Q

What are some advantages of Intensifying Screens?

A
  • Shorter Exposure times
  • Extend the life of the tube
  • Improved image contrast
  • Smaller focal spot size
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4
Q

What are some disadvantages of Intensifying Screens?

A
  • Wear (they are not long term)
  • Blurring
  • Magnification
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5
Q

How much of the latent image is formed by the fluorescence of the screens?

A

99%

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6
Q

By amplifying the incoming x-ray beam, what happens to the patent dose?

A

It is decreased

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7
Q

What is the purpose of the reflective layer?

A

To intercept light that has interacted with the phosphor and redirects it to the film

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8
Q

What does the Base of the intensifying screen do?

A

Serves as mechanical support for the active phosphor layer

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9
Q

Describe the Base of the intensifying screen:

A
  • Polyester or cellulose triacetate
  • Rugged, moist layer (does not absorb water)
  • Chemically inert
  • Flexible
  • Does not discolor with age
  • Does not suffer from radiation damage
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10
Q

What is Luminescence?

A

The emission of visible light

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11
Q

Where is the protective coating layer located?

A

Layer closest to the film (actually touches the film)

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12
Q

What is the protective layer useful for?

A

To prevent Abrasions and Stains

  • Abrasions
    • Fingernails, Jewelry
    • Pick off
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13
Q

What is pick off?

A

White line artifacts caused by watches, bracelets fingernails etc.

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14
Q

What prevents static electricity build up?

A

The Protective Layer

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15
Q

What are two things the protective layer must be?

A
  • Transparent to light (for fluorescence)

- Have a durable surface for cleaning

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16
Q

What is another name for the phosphor layer?

A

The Active Layer

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17
Q

Where are the rare earth elements that create the glow located?

A

In the active layer

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18
Q

What creates the glow of the intensifying screen?

A

The rare earth elements within the active layer when exposed to radiation

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19
Q

What impacts the quality and amplification of the phosphor/ active layer?

A
  • Thickness of layer
  • Concentration of phosphor crystals
  • Size of crystals
  • Type of phosphor
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20
Q

What are the two types of rare earth elements used at the phosphor layer?

A
  • Yttirium Tantalate

- Gadolanium (used in MRI contrast)

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21
Q

What do phosphors do?

A

Convert x-ray beam to light

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22
Q

What is minimal afterglow?

A

All light stops after exposure

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23
Q

What are the Favorable Properties of a Radiographic Intensifying screen phosphor

A
  1. Should have high atomic #, so absorption is high
  2. Should emit large amount of light when struck by x-rays
  3. Minimal afterglow
  4. Must have proper wavelength (spectral matching)
  5. Not affected by heat, humidity or other elements
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24
Q

What happens when x-rays interact with the reflective layer?

A

It emits light and reflects back to the film (shiny white surface)

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25
Q

What is the most important property of the reflective layer?

A

To intercept light and redirect it

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26
Q

What is the goal of the reflective layer?

A

To get as much light from the phosphor layer to the film

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27
Q

What typically degrades a film?

A

The way we handle them

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28
Q

What is an important thing about Fluorescence?

A

Light is distributed Isotropically (evenly)

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29
Q

What is Fluorescence?

A

Visible light emitted when phosphor is stimulated

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30
Q

What is Phosphorescence?

A
  • Long periods of visible light emission after stimulation of phosphor
  • Screen lag or after glow (still giving off light)
  • Missed the return
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31
Q

Is Phosphorescence wanted or unwanted?

A

Unwanted

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32
Q

What is screen speed?

A

A number used to identify the efficiency of conversion of x-rays to usable light

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33
Q

What are effecting factors of screen speed?

A

Increase in:

  • Phosphor size
  • Thickness of layer
  • Concentration
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34
Q

In terms of film speed, what will an increase in temperature do?

A

Give you a decrease in screen speed

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35
Q

What are the (3) screen speed classes?

A
  • Fast
  • Slow
  • Medium
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36
Q

Describe the characteristics of Fast Screens:

A

Thick Layer

Large Crystals

37
Q

Describe the characteristics of Slow Screens:

A

Thin Layer

Small Crystal size

38
Q

Describe the characteristics of Medium Screens:

A

Medium Layers

Medium Crystal size

39
Q

What speed film will give you better detail, but requires more radiation?

A

Slow Screens

40
Q

The faster the intensifying screen the more…

A

Light emitted for the same x-ray exposure

41
Q

What two speeds are typically used?

A

Fast and Slow

42
Q

Fast screen film will give you speed, but what does it sacrifice?

A

Quality and Detail

43
Q

Using intensifying screens greatly reduces what?

A

The amount of x-rays needed and patient dose

44
Q

Are rare earth screens widely used?

A

Yes

45
Q

Test

Lanthanum and Gadolinium are faster and more efficient than what?

A

Calcium Tungstate

46
Q

What does RESC stand for?

A

Rare Earth Screen Cassettes

47
Q

What is Quantum Mottle

A

Speckles; Defects in the image

like rain drops on a sidewalk

48
Q

RESC are manufactured to perform at…

A

Increased speeds without effecting resolution

-but show effects of quantum mottle

49
Q

RESC has increased sensitivity. What are some examples?

A
  • Higher x-ray absorption

- More efficient conversion of x-ray energy into light

50
Q

What must be spectrally matched with film?

A

RESC

51
Q

What is responsible for absorption of x-rays in the screen

A

Photoelectric effect

52
Q

What is K-shell absorption edge?

A
  • When x-ray energy= K shell electrons

- Can bind and become available for photoelectric interactions

53
Q

What is the K-shell?

A

The only shell that produces characteristic x-rays (69.5)

54
Q

The probability of photoelectric absorption in RESC is higher when the x-ray energy in K-shell electron binding energy is…

A

Matched

55
Q

What is the Intensification Factor (IF)?

A

The ratio of the exposures required to produce the same optical density with and without screens

56
Q

IF=

A

Exposure required without screens
_____________________________
Exposure required with screens

57
Q

If you are imaging a hand on a direct exposure cassette at 100 mAs, and at 4 mAs with an intensifying screen, what is your IF?

A

100
____ = 25
4

IF= 25 times higher

58
Q

Intensification Factor is directly proportional to what?

A

Screen speed

59
Q

What is Conversion Efficiency?

A
  • The ability of the phosphor to emit as much light per x-ray photon interaction as possible
  • Ideally x-ray photon is converted into visible light
60
Q

True /False

In Conversion Efficiency, the higher it is the better?

A

True

61
Q

As CE increases, patient dose does what?

A

Decreases

62
Q

What is Quantum (x-ray photons) Mottle?

A

Insufficient quantity of photons striking the intensifying screen

63
Q

What does an intensifying screen with a reflective layer do?

A

Provides focus onto the film for high conversion

64
Q

What is spacial resolution?

A
  • Ability to accurately image an object
  • Image Detail
  • How well you see the detail of the image
65
Q

T/F

With the use of Intensifying screens you get a loss of Spatial resolution?

A

True

But less patient dose

66
Q

Spacial Resolution is effected by what?

A

Focal Spot size

  • Size
  • Thickness
  • Concentration
67
Q

What does a greater concentration of crystals do?

A

Gives you better resolution; improved screen speed

68
Q

What are ways spatial resolution are affected?

A
  • OID
  • SID
  • Focal Spot size
  • Motion
69
Q

What does film screen combination decrease?

A

Decreases:

  • Patient dose
  • Occupational Exposure
  • Tube heat production
  • X-ray exposure time
  • X-ray tube mA
  • Focal spot size
70
Q

What do film screen combinations Increase?

A

Increases:

  • Variability of kVp selection
  • Contrast adjustment
  • Spatial resolution
  • Ability to magnify image
71
Q

What are the parts of a cassette?

A
  • Front cover
  • Contact felt
  • Front screen (intensifying screen)
  • Film
  • Back screen (intensifying screen)
  • Contact felt
  • Back cover
72
Q

Describe the front cover:

A
  • Made of carbon fiber
  • Low atomic #
  • Minimal attenuation
73
Q

Describe the back cover?

A
  • Thicker
  • Metal
  • High atomic #
  • Absorption of transmitted x-rays (image absorbed)
74
Q

What are some cassette requirements?

A
  • Low absorption front material
  • Lead foil back (as a barrier)
  • Provides tight film screen contact
75
Q

What are some examples of the “ease of use” design for the cassettes?

A
  • Easy to handle in the darkroom
  • Will not accidentally open in daylight
  • Not too heavy
76
Q

What color is the front side of the cassette?

A

Brown

77
Q

What is the reason for the felt in the primary barrier?

A
  • To give a firm base for adequate pressure when closing

- Gives even contact

78
Q

RESC exhibit a CE of…

A

15-20%

Resulting in increased sensitivity and speed

79
Q

RESC emit a green light and the use of specially designed ________________ must be used to maintain speed

A

Green sensitive film

  • Whatever the color, they must be matched
  • (blue/ blue etc)
80
Q

When opening, how much can you open the cassette?

A

2-3 inches

81
Q

How do you store film?

A

On end

82
Q

How are films cleaned?

A

With an electrostatic cleaning solution

DO NOT USE WATER

83
Q

Why do you clean film with an electrostatic cleaning solution?

A
  • Does not leave mineral stains

- Will not become sticky

84
Q

How long will cassettes last with proper care?

A

10-15 years

85
Q

When using gauze to clean screens, how do you wipe?

A

Side to side at right angles

86
Q

What is poor screen film contact?

A

Loss of contact which degrades the film

87
Q

What is the main cause of poor film screen contact?

A

Poor management of cassettes

88
Q

When are film screens evaluated?

A

Every quarter or semi annually

89
Q

What is the cause an exhausted cassette?

A
  • Mishandling
  • Lack of cleaning
  • Age

Rad Exposures (3 decks)

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