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From Flashcardlet > processing unit 1 part 2 > Flashcards

processing unit 1 part 2 Flashcards

0
Q

The emission of visible light is called? What are the two types?

A

Luminescence

Phosphorescence and fluorescence

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1
Q

Function of intensifying screen and primary advantage of using one?

A

Converts X-rays to light. Light exposes the film interacts with emulsion to produce latent image.
Reduce patient dose

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2
Q

How does luminescence occur?

A

Radn hits atom causing outer e to excite and remove and then return to place causing light emission

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3
Q

When phosphor continues to emit light after stimulation is called? Also known as?

A

Phosphorescence

Afterglow, screen lag

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4
Q

Visible light is emitted only during stimulation is called?

A

Fluorescence

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5
Q

Layers of an intensifying screen

A

Protective layer
Phosphor layer or active layer
Reflective layer
Base

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6
Q

Protective layer must be transparent to light and allow light to be emitted evenly is known as?

A

Uniform lucency

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7
Q

Location of phosphor layer, it’s function, high or low atomic number?

A

Btwn protective and reflective
Converts X-rays to emit light
High atomic so it absorbs more X-rays to convert to light

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8
Q

Types of phosphors used?

A

Rare earth and non rare earth

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9
Q

Most popular non rare earth phosphor emits what color light, it’s atomic number, list 2 other non rare earth phosphors

A

Calcium tungstate emits blue light (Thomas Edison 1914)
Atomic number 74
Barium lead sulfate and barium fluorochloride

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10
Q

Examples of rare earth phosphors, what light they emit?

A 
Yttrium (39) emits blue
Gadolinium oxysulfide (64) MRI use emits green
Lanthanum oxysulfide (57) emits green
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11
Q

Two primary advantages do using rare earth

A

High absorption efficiency

Higher conversion efficiency

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12
Q

Location and purpose of reflective layer

A

Btwn base and phosphor

Directs light back towards film instead of all directions, dble amt of light reaching film increasing screen speed

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13
Q

Light from screen emitted equally in all directions is called? Where do we want it to go?

A

Isotopic emission

Want it to interact with emulsion of film

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14
Q

Base of intensifying screen location and is made of?

A

Farthest from the film but closest to cassette cover

Polyester plastic for durability and flexible support

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15
Q

Absorption efficiency known as? Definition?

A

DQE detective quantum efficiency

How well phosphors in screens absorb X-rays

16
Q

Differences in phosphors of absorption efficiency

A

Calcium tungstate is 30%

Rare earth is 50-60%

17
Q

Most absorption of X-rays by the intensifying screen phosphors is result of what type of effect?

A

Photoelectric

18
Q

Conversion efficiency definition, CE of tungstate and rare earths, how it effects pt dose

A

How well phosphors convert X-rays to light
Tungstate is 5
Rare earth is 15-20
Higher CE = lower pt dose

19
Q

The color of light emitted from intensifier must match the color of light the film is sensitive to is called?

A

Spectral matching

20
Q

Orthochromatic should be used with what type of screens? Tungstate? What happens if not?

A

Rare earth bc green
Blue light
Image will be under exposed (light)

21
Q

Amount of exposure needed to produce a given density is known as?

A

Intensifying screen speed

22
Q

Faster screen speed does what to pt dose? Resolution?

A

Decrease pt dose

Decrease resolution

23
Q

Ratio needed to produce given density without using screens to the amount of exposure needed to produce same density with screens is called

A

Intensification factor

Without screens / with screens

24
Q

Larger crystals does what to screen speed?

Thickness of phosphor layer does what to screen speed?

A

Increase IF screen speed

25
Q

How use of reflective layer affects screen speed and IF

A

Increased speed = increased IF

26
Q

Resolution also called?

A

Recorded detail or sharpness

Called resolution in CR and DR

27
Q

Resolution is measured in?

A

Line pairs / mm

28
Q

Type film produces best recorded detail? LP/mm?

A

Direct nonscreen film
50
10 to eye lp/mm

29
Q

Type screen produces best resolution? Lp/mm?

A

Slow or detailed screens

15 lp/mm

30
Q

Crystal size and phosphor thickness affect on resolution?

A

Smaller crystals = better resolution

Thinner phosphor layer = better resolution

31
Q

An area of I sharpness may result from torn compression pad caused by?

A

Poor screen film contact

32
Q

Resolution for CR and DR images

A

CR 2.5 to 5 lp/mm

DR 5 to 15 lp/mm with avg 8

33
Q

Deterioration or grainy appearance is called (2)?

A

Quantum mottle or image noise

34
Q

Causes for quantum mottle

A

Low mA
Isotopic emission
Low absorption efficiency of screen

35
Q

Low absorption efficiency of screen also called

A

DQE

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