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trisemester 3 TCC > test 2 xray physics > Flashcards

test 2 xray physics Flashcards

1
Q

What happens to contrast when lower kVp is used?

A

Higher contrast image is created with a shorter scale of contrast (less steps between darkest and lightest)

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2
Q

What type of x-ray will create an image with less contrast?

High kVp and Low mAs

or

Low kVp and High mAs

A

High kVp and Low mAs

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3
Q

How does higher kVp/lower mA affect scatter?

A

More scatter

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4
Q

Where is the grid placed?

A

Behind the patient and in front of the image receptor (basically between patient and image receptor)

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5
Q

When using a grid, how does it affect the exposure to the patient?

A

It will increase the exposure to the patient anywhere between 4-5 times compared to no grid

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6
Q

How does a grid affect image quality?

A

Improved diagnostic image quality

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7
Q

What happens to non-scattered photons as they pass through a grid?

A

They pass through the radiolucent part of the grid, but some do still get absorbed by the lead strips

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8
Q

What is grid ratio?

A

Height of the lead strips divided by the distance between the lead strips (h/D)

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9
Q

What is the grid frequency?

A

Number of lines per inch or other unit of measurement

lines/inch

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10
Q

Pertaining to grids, what is the height of the lead strips divided by the distance between the lead strips?

A

Grid ratio

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11
Q

What is grid selectivity or “Sigma”?

A

Amount of primary radiation transmitted divided by the scatter radiation transmitted

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12
Q

If the grid ratio is very high, how much scatter goes through?

A

Very little scatter

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13
Q

If the grid ratio is very low, how much scatter goes through?

A

Lots of scatter goes through

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14
Q

What is a typical grid ratio for musculoskeletal imaging?

A

5:1 - 12:1 ratio

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15
Q

What type of grid ratio has better clean up and better contrast?

A

Higher ratio grids

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16
Q

What happens to patient dose as you increase the grid ratio?

A

It increases

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17
Q

Pertaining to grid frequency, what frequency is generally less efficient? (high or low)

A

High frequency

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18
Q

Pertaining to grid frequency, what frequency is generally more efficient? (high or low)

A

Low frequency

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19
Q

Do higher frequency grids require more or less dose?

A

More pt. dose

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20
Q

Most grids range from _____-_____ lines per centimeter

A

25-45 lines per centimeter

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21
Q

How can you increase grid ratio?

A

Increase the height of lead strips or decrease the distance between the lead strips

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22
Q

Where does grid cut-off occur?

A

The lateral margins of the grid, especially with closer source-image distances

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23
Q

What is the grid that involved grid strips that are angled to accommodate the increasingly divergent angle of photons further away from the central ray?

A

Focused grids - these are used for general radiography

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24
Q

Do higher ratio grids have more or less focal range than low ratio grids?

A

Less focal range

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25
Q

What happens to focal range with a lower grid ratio?

A

It increases

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26
Q

What are crossed grids?

A

Grids with lead strips that run both lengthwise and side-to-side to reduce more scatter photons. (These are not usually used in general radiography)

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27
Q

What are some drawbacks to the air-gap technique?

A

There can be image magnification and distortion of the image

Higher exposure is also necessary (about 10% increase per cm of air gap)

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28
Q

What projection includes a natural air gap?

A

Lateral cervical spine x-ray

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29
Q

What is the term for screen film radiography?

A

Analog radiography

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30
Q

What is the exiting beam also known as?

A

Remnant beam, it is the x-ray beam that forms the image

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31
Q

What is the purpose of the film?

A

To create a permanent record of the x-ray exiting beam

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32
Q

What are the major components of film?

A

Base - piece of plastic for physical support

Emulsion - picture layers of the film

Adhesive lay

Supercoating - protection

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33
Q

Originally, glass was used as what part of the x-ray film?

A

Base

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34
Q

What type of material replaced the glass base very long ago, but was very flammable?

A

Cellulose nitrate

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35
Q

What type of material is currently used as the base of x-ray film?

A

Polyester

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36
Q

What makes up the emulsion layer of x-ray film?

A

A homogenous mixture of gelatin and silver halide crystals

Gelatin provides = support

Silver halide crystal = sensitive to light and X-ray

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37
Q

What type of formation is silver halide?

A

Crystal lattice formation

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38
Q

What are the components of the silver halide crystal that helps make up the emulsion layer of x-ray film?

A

Silver bromide 95%

Silver iodide 5%

Silver sulfide

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39
Q

What component of the silver halide crystal is extremely important in photosensitivity of film?

A

Silver sulfide

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40
Q

X-ray film is mostly exposed by light from what

A

Intensifying screens

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41
Q

Exposure of the film to light or x-ray photons causes a movement of electrons and/or atoms within the silver halide crystal is know as what? It is the invisible change in electron configuration of silver halide crystal.

A

Latent image formation

42
Q

What is latent image?

A

It is the invisible change in electron configuration of silver halide crystal

43
Q

What happens at the molecular level of the silver halide crystals when exposed to light/x-rays?

A

electrons accumulate at the silver sulfide “sensitivity specks” and reduce a very small number of the silver ions to metallic silver

44
Q

Electrons accumulate at the silver sulfide “sensitivity specks” and reduce a very small number of the silver ions to _______________.

A

Metallic silver

45
Q

What is the most common type of film used in general purpose radiography?

A

Screen film

46
Q

What type of film is used in conjunction with intensifying screens?

A

screen film

47
Q

What is the purpose of the intensifying screen?

A

To convert x-ray photon energy into visible light photons

48
Q

What causes the “most” film exposure?

A

Visible light generated by the intensifying screen

49
Q

Screen film that has emulsion on the front and back of it to increase speed is known as what?

A

duplex film

50
Q

What effect does duplex film do when taking x-rays?

A

Increases speed of the system/decrease amount of radiation

51
Q

What are important film characteristic that can be influenced by the kind of film that is being used?

A

Speed and Contrast

52
Q

What color systems are used in x-ray?

A

Blue or Green

53
Q

In what color wavelengths are x-ray films most sensitive to light?

A

Blue and Green spectra

54
Q

If using blue sensitive film, what color light should be used?

A

blue

55
Q

If using green sensitive film, what color light should be used?

A

greeeeeeeen

56
Q

Which color is better for x-rays? Green or Blue?

A

DO NOT MATTER

57
Q

What is the term for a light source that emits light in a spectra that the film has a low sensitivity to?

A

safe lights

58
Q

are safe lights completely safe?

A

no, that are only safe at a limited time and intensity

59
Q

Red safe light filters are safe for what color film?

A

blue and green

60
Q

What is the maximum wattage for safe lights?

A

15 watts

61
Q

What is the minimum distance that the safe light can be from the working surface?

A

5 ft.

62
Q

What type of film is designed to be used without intensifying screens?

A

direct exposure film

63
Q

What is direct exposure film used for?

A

Dental applications

64
Q

What is the film that only has emulsion on one side?

A

single emulsion

65
Q

How does duplicating film (film used to make a copy of x-rays) act compared to regular x-ray film?

A

Reacts in opposite fashion to regular x-ray film

66
Q

What color do exposed areas of duplicating film become?

A

white

which is the opposite of x-ray film which turns black

67
Q

What temperature should unexposed x-ray film should be stored?

A

below 68 deg.

68
Q

How long will x-ray film last at room temperature?

A

45 days

69
Q

What humidity should x-ray film be stored at?

A

Less than 60%

70
Q

What should you avoid when handing unexposed film?

A

Avoid excess heat = <68 degrees

Avoid excess humidity = <60%

Avoid static electricity (occurs with <40% humidity)

Avoid light or x-ray exposure

Avoid mechanical force

71
Q

If we have static electricity on an unexposed film, what can occur?

A

latent image can occur

72
Q

Film that has been exposed to diagnostic x-ray is more sensitive to ______ or __________ than unexposed film

A

light; radiation fog

73
Q

How do you remove lines/marks on exposed and processed x-ray films?

A

Denatured Alcohol, do not use water because it will make gelatin softer and can cause the image to be scratched

74
Q

What do you do if your processed x-ray film is wet?

A

Let it dry but

Do not place next to anything because acts like glue

75
Q

What is the term for converting latent image formation into visual (manifest) image?

A

film processing

76
Q

What does film processing do at the atomic level?

A

It will potentiate the reaction of the ionic silver into metallic silver of the exposed crystals. (it turns black)

77
Q

What are the 4 steps of film processing?

A

Developing

Fixing

Washing

Drying

78
Q

What stage of film processing involves the latent image becoming the manifest image?

A

Developing stage

79
Q

What makes up the developer solution?

A

Water and Reducing agent (reduces ionized silver into metallic silver)

80
Q

What color do exposed silver halide crystals become?

A

Black

81
Q

What is the purpose of the fixing solution?

A

Stop the reduction reaction of the developer solution

Removes unexposed emulsion

Preserves the image

82
Q

What chemical in the fixing solution stops the action of the developer?

A

Acetic acid

83
Q

What solution stops the reduction reaction of the developer solution, removes the unexposed emulsion, and preserves the image?

A

Fixing solution

84
Q

What are important variables in processing images?

A

Time, Temperature, Chemical concentration

85
Q

What happens if film is left in developer solution for too long?

A

It will over-develop causing the reducing agent to begin to act on unexposed silver halide crystals. It will look like an over exposed film (black)

86
Q

Is time more important in the developing or fixer stage?

A

developing

87
Q

What stage is the most temperature dependent part of processing film?

A

developing

88
Q

Developing temperature should not vary by more than how much degrees?

A

+/- 1 degree Fahrenheit

89
Q

Excess temperature in developer solution will make film appear like what?

A

Over-exposed

90
Q

What temperature do most automatic processes operate at for processing film?

A

95 degrees Fahrenheit

91
Q

Proper chemical concentration is important in what stage(s) when processing film?

A

Developing and fixing stages

92
Q

What happens to chemical strength/potency when a film is processed?

A

It diminishes

93
Q

What happens to chemical strength/potency when developer/fixing solution is stored over time?

A

it will diminish

94
Q

What removes residual chemicals from the emulsion when processing film?

A

Washing - “Water bath”

95
Q

What color will the film look like over time if fixer solution is left on the film?

A

Rusty-brown/orange color

96
Q

You notice an old x-ray that appears to have a rusty-brown/orange tint. What caused this?

A

Fixer solution was left on the image and not washed off properly

97
Q

A small amount of _______ solution will ruin a large amount of _______ solution.

A

A small amount of fixer solution will ruin a large amount of developer solution.

98
Q

What is the final stage of processing film?

A

Drying stage - using forced hot air

99
Q

What is worse? Having some developer solution contaminate fixer solution or having some fixer solution contaminate developer solution?

A

Having some fixer solution contaminate developer solution is much worse.

100
Q

why is having some fixer solution contaminate developer solution much worse?

A

has to do with the flow of processing. The fixer solution come after the developer solution and will have a worse affect with only a bit getting in

trisemester 3 TCC (25 decks)

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