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Radiographic Physics Exam 2 > Density 1 > Flashcards

Density 1 Flashcards

1
Q

What can be affected by altering the FFD/SID?

A

Density and detail

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2
Q

What can be affected by altering OFD (object film distance)?

A

Detail

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3
Q

What is the appearance of an underexposed film?

A

Too light (not enough mAs)

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4
Q

What is the appearance of an overexposed film?

A

Too dark (too much mAs)

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5
Q

What is the appearance of a radiolucent object on film?

A

Black (x-rays pass right through)

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6
Q

What is the appearance of a radiopaque object on film?

A

White (x-rays are absorbed and don’t hit film)

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7
Q

What term is used to describe something appearing on a film that could be easily removed from the patient before an x-ray is taken (examples = necklaces, earrings, glasses)?

A

Artifact

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8
Q

What term describes something appearing on a film that cannot be easily removed from the patient (examples = prosthesis, surgical clips)?

A

Foreign body

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9
Q

Why do foreign bodies appear white on x-ray?

A

X-rays are absorbed and not going through to the film (radiopaque)

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10
Q

What measurement is the quantity of electrons to be boiled off the filament?

A

mA

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11
Q

What measurement is the time in seconds the electrons have to boil off the filament?

A

S

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12
Q

How do we achieve mAs and what is it?

A

mA X s; the quantity of x-rays produced

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13
Q

How much of the energy produced from x-ray is heat? How much is usable x-ray energy for film?

A

99% heat

1% x-rays

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14
Q

What directly sends the electrons to the filament?

A

mA button

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15
Q

What structure emits the electrons through thermionic emission?

A

Heated filament

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16
Q

What feature of the anode makes it attract the electrons?

A

Strong positive charge

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17
Q

How fast can electrons accelerate?

A

0 to 1.5 billion meters per second

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18
Q

What is the distance from the cathode to anode?

A

2 centimeters

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19
Q

Where is the electron energy converted to x-ray energy (1%) and heat energy (99%)?

A

At collision with Tungsten anode target

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20
Q

What measurement must be analyzed to determine which technique utilizes the most electrons?

A

mA (higher the mA, the more electrons used)

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21
Q

What measurement must be analyzed to determine which technique produces the most x-rays?

A

mAs (higher the mAs, the more x-rays produced)

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22
Q

What is the relationship between mA and mAs?

A

DIRECT (example = when mA is doubled, mAs is also doubled)

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23
Q

What is the relationship between time and mAs?

A

DIRECT (example = when time is doubled, mAs is also doubled

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24
Q

How does increased time affect density?

A

Increased density due to increased mAs (which controls overall density)

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25
Q

A calcium deposit in the body showing up on x-ray would be an example of: radiolucency or radiopacity?

A

Radiopacity

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26
Q

What color appears on x-ray when x-ray photons pass through the tissue and expose the film?

A

Black

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27
Q

What color appears on x-ray when x-ray photons are completely absorbed and no x-ray photons hit the film?

A

White

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28
Q

What does it mean when gray appears on the film?

A

Some x-rays are absorbed while others pass through

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29
Q

What measurement is responsible for varying shades of gray on a film?

A

kVp

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30
Q

What are the five patient densities that are visible upon x-ray?

A 
1 air
2 fat (oil)
3 water
4 bone
5 metal
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31
Q

Which of the five patient densities is most radiopaque?

A

Bone and metal

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32
Q

Which of the five patient densities is most radiolucent?

A

Gas

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33
Q

How do skin, blood, muscle, and fat appear on x-ray?

A

Gray

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34
Q

What general levels of mAs and kVp are needed to penetrate skin, blood, muscle, and fat on x-ray?

A

Medium

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35
Q

What general levels of mAs and kVp are needed to penetrate bone and metal on x-ray?

A

High

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36
Q

What general levels of mAs and kVp are needed to penetrate gas on x-ray?

A

Low

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37
Q

When a film appears darker, is it over- or underexposed?

A

Overexposed (too much mAs)

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38
Q

How could we fix a film that is overexposed?

A

Cut mAs by 1/2 (to decrease density)

39
Q

If a film appears too light, is the film over- or underexposed?

A

Underexposed

40
Q

How could we fix a film that is underexposed?

A

Double mAs (technically increasing kVp would also help)

41
Q

What amount of change in mAs is required to even see a visible change in darkness on a film?

A

30% change

42
Q

What is the general rule for changing mAs to fix a film?

A

50% mAs reciprocal rule (double or cut density in half on a too light or too dark film by doubling or cutting mAs in half)

43
Q

Even though a film requires a 30% change in mAs to have a visible difference, what is the issue with that concept?

A

A film should NEVER be retaken solely for a 30% change

44
Q

Double the density of this technique: 50 mAs @ 70 kVp.

A

100 mAs @ 70 kVp

45
Q

Cut the density in half of this technique: 30 mAs @ 65 kVp.

A

15 mAs @ 65 kVp

46
Q

Double the density of this technique: 300 mA, .5 sec @ 80 kVp.

A

300 mA, 1 sec @ 80 kVp

47
Q

Cut the density in half of this technique: 150 mA, .2 sec @ 70 kVp.

A

150 mA, .1 sec @ 70 kVp

48
Q

What secondary things can affect density?

A

kVp, FFD/SID, patient size and shape, pathology, film processing, grids, film-screen speed, compensating filtration

49
Q

What is the relationship between film density and FFD/SID?

A

Inversely proportional

50
Q

What effect does a longer FFD/SID have on density?

A

Decreased density (lighter film)

51
Q

What is the purpose of the direct square law?

A

Maintain radiographic density when distance changes

52
Q

How should mAs be adjusted when distance increases to maintain radiographic density?

A

Triple mAs (rule of 3)

53
Q

How should mAs be adjusted when distance decreases to maintain radiographic density?

A

Divide mAs by 3 (rule of 3)

54
Q

If the current film is at 40” and at 25 mAs, 75 kVp and is going to be moved to 72”, what should the new mAs be to maintain overall film density?

A

75 mAs (tripled because of the rule of 3)

55
Q

What is the function of the developer?

A

Reduces exposed silver to black atomic silver

56
Q

The developer action is directly proportional to what measurements?

A

Developer concentration and temperature and developing time

57
Q

Would an increase or decrease in developer concentration lead to a lighter film?

A

Decrease

58
Q

Would an increase or decrease in developing time lead to a darker film?

A

Increase

59
Q

Would an increase or decrease in developer temperature lead to a lighter film?

A

Decrease

60
Q

What structures are contained within the screen?

A

Phosphor crystrals

61
Q

How many layers make up the screen?

A

4: base, undercoating, phosphor layer, and protective layer

62
Q

Where is the screen located?

A

Inside cassettes (in contact with film)

63
Q

Does a slower or faster screen require less mAs?

A

Faster (less x-ray needed)

64
Q

Which presents with a loss of detail: slower or faster screens?

A

Faster screens

65
Q

What is an overall benefit to using a faster screen regarding the patient?

A

Patient dose reduced

66
Q

Which increases patient dose: slower or faster screen?

A

Slower screen

67
Q

Which has better detail: slower or faster screen?

A

Slower screen

68
Q

Which has less light being emitted from the phosphors: slower or faster screen?

A

Slower screen (therefore, more x-ray is required)

69
Q

Define hyperstenic in reference to patient size.

A

Large

70
Q

Define stenic in reference to patient size.

A

Average

71
Q

Define asthenic in reference to patient size.

A

Thinner than average

72
Q

Define hypostenic in reference to patient size.

A

Super thin

73
Q

What measurements must be altered with larger patients and why?

A

Increased mAs and more kVp due to increased production of scatter

74
Q

What measurement is the power responsible for penetrating anatomy and production of scatter?

A

kVp

75
Q

What is the term for the radiation that interacts with matter that travels in all different directions and has experience a loss of energy?

A

Scatter (seen more with larger patients)

76
Q

In the diagnostic energy range, which five ways of interaction between x-rays and matter are clinically significant?

A

Compton’s and photoelectric effects

77
Q

What is Compton’s effect, in general?

A

Scatter

78
Q

What is the photoelectric effect, in general?

A

Absorption

79
Q

What are the five ways in which x-rays react with matter?

A 
1 Compton's effect (scatter)
2 Photoelectric effect (absorption)
3 Classical scatter
4 Pair production
5 Photodisintegration
80
Q

Most of the scatter produced is by what concept?

A

Compton’s effect

81
Q

What is another term for radiographic noise?

A

Scatter

82
Q

How does scatter affect the contrast of the film?

A

Decreases contrast (foggy appearance)

83
Q

What two factors determine the probability that an x-ray photon will scatter?

A

1 density of object

2 energy of x-ray

84
Q

Which types of x-rays tend to scatter: high-energy, mid to high energy, or low-energy?

A

Mid to high energy x-rays

85
Q

What two things increase with increased kVp?

A

Scatter and penetration

86
Q

What is produced from the differential absorption of x-rays in tissues caused by the photoelectric effect?

A

Subject contrast

87
Q

Do electrons closer to the nucleus or further from the nucleus have less binding energy?

A

Further from the nucleus

88
Q

When is absorption most likely to occur?

A

When the energy of the x-ray is equal to or slightly greater than the binding energy of the electron it interacts with

89
Q

When the energy of the x-ray is much greater than the binding energy of the electron it interacts with, what is the outcome?

A

Scatter or straight penetration

90
Q

Do more dense or less dense tissues cause increased absorption?

A

More dense

91
Q

What type of scatter results from low-energy x-rays interacting with matter?

A

Classical scatter (insufficient energy to cause ionization)

92
Q

What concept occurs when an x-ray interacts with the nucleus, and the energy is converted into matter in the form of a positron and negatron?

A

Pair production

93
Q

During pair production, what is the end result with the positron and negatron?

A

They annihilate each other releasing two .51 MeV gamma rays in opposite directions

Radiographic Physics Exam 2 (4 decks)

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