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Rad105 > Test 3 - Chpt 7, 8 > Flashcards

Test 3 - Chpt 7, 8 Flashcards

1
Q

Understanding x-ray photon interaction does what (2)

A

Minimizes harm to the patient
produces better-quality images

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2
Q

X-rays do these 3 things

A

get absorbed = white
travel straight through = black
scatter or secondary beam = grey

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3
Q

What three interactions are found within the diagnostic range

A

classical, Compton scattering, photoelectric effect

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4
Q

Coherent scattering AKA

A

classical or Thomson scattering

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5
Q

What 3 things does the Compton interaction do?

A
  • ionizes the atom = makes it unstable
  • Compton electron (ejected electron) goes through interactions of its own in adjacent atoms
  • incident photon (Compton scatter photon) is deflected and also causes interactions
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6
Q

In this event, the incident x-ray photon interacts with an orbital electron of a tissue atom and changes direction (no ionization)

A

coherent/classical / Thomson scattering

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7
Q

Interaction that has a low energy x-ray photon

A

coherent scattering

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8
Q

What results from coherent scattering? (Contrast)

A

Slightly lower contrast because it increases the scatter that reaches the IR

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9
Q

coherent scattering is likely to occur when an X-ray photon interacts with what?

A

the whole atom

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10
Q

What interaction contributes to the highest proportion of scatter in the image?

A

Compton scattering

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11
Q

What interaction results in image fog?

A

Compton scatter because the scatter strikes the IR in the wrong place

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12
Q

What is the most prevalent interaction between X-ray photons and the human body in general diagnostic imaging?

A

Compton scatter

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13
Q

The probability of Compton scatter is related to the?

A

the energy of the photon

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14
Q

How much energy do Compton scatter photons retain?

A

about 2/3

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15
Q

The major source of occupational dose is from what interaction?

A

Compton scatter

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16
Q

During a Compton interaction, what is the electron called that gets knocked out of orbit?

A

Compton electron

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17
Q

During a Compton interaction, after the electron is knocked out of orbit what does the remaining energy leave the atom as, and what is it called?

A

leaves the atom as a scattered photon AKA Compton photon

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18
Q

What shell does photoelectric interactions interact with?

A

inner shell electrons

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19
Q

During a photoelectric interaction, what is the electron called that was knocked out of orbit?

A

photoelectron

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20
Q

During a photoelectric interaction, what happens after the inner shell electron is knocked out of orbit, and what is created?

A

inner-shell vacancy creates a cascade effect and creates a characteristic photon

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21
Q

What happens to the characteristic photon that is created from a photoelectric interaction?

A

gets absorbed by the surrounding tissues

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22
Q

(T/F) The photoelectron has enough energy to undergo interactions of its own

A

true

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23
Q

What do photoelectric interactions affect?

A

increases the patient dose and increases image quality

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24
Q

The probability of the photoelectric interaction depends on what three things?

A
  • energy of the incident photons
  • atomic number of the tissue atoms
  • binding energy of the inner shell
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25
Q

Increasing kVp = # of Compton interactions does what and probability does what?

A

interactions increase, and probability decreases

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26
Q

decreasing kVp = # of photoelectric interactions does what and probability does what?

A

interactions increase, probaility compared to Compton increases

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27
Q

Interaction that results in the incident photon having enough energy to not interact with the electrons but interacts with the nucleus instead

A

pair production

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28
Q

What two things are produced from pair production?

A

positron and an electron

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29
Q

Pair production is AKA

A

annihilation reaction

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30
Q

for the positron and electron particles of a pair production interaction to exist they must have what energy?

A

0.51 MeV each
(the energy equivalent of an electron)

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31
Q

What happens to the electron from a pair production interaction?

A

goes through many interactions before resting in another atom

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32
Q

What happens to the positron from a pair production interaction?

A

travels until it strikes an electron and causes an annihilation event
(positron and electron are destroyed, converting their energy into 2 x-ray photons)

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33
Q

How does photodisintegration occur?

A

when photons with super high energies strike the nucleus of the atom and make it unstable

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34
Q

During photodisintegration, how does the nucleus of the atom become stable?

A

it ejects a nuclear particle

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35
Q

What is differential absorption?

A

difference between x-ray photons that are absorbed photo-electrically versus those that penetrate the body

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36
Q

What is it called when X-ray photons pass through the body and reach the IR?

A

transmission

37
Q

What is it called when photons are absorbed by the body and don’t reach the IR?

A

absorption

38
Q

When an X-ray photon interacts with a macromolecule the energy may manifest as a change to what?

A

As a change to the structure of the macromolecule

39
Q

The 3 most common effects of differential absorption

A

main-chain scission
cross-linking
point lesions

40
Q

(T/F) the composition of the anatomic tissues affects the x-ray beam interaction

A

true

41
Q

What creates an image that structurally represents the anatomic area?

A

differential absorption
(transmission and absorption)

42
Q

Do anatomic parts absorb the primary beam to the same degree?

A

No

43
Q

What is the reduction in the energy or number of photons in the primary x-ray beam?

A

attenuation

44
Q

what occurs as a result of the photon interactions with the atomic structures that compose the tissues?

A

attenuation

45
Q

What 2 processes occur in the diagnostic range?

A

absorption and scattering

46
Q

total photon absorption depends on what?

A

the energy of the incoming x-ray photon and the atomic number of anatomic tissue

47
Q

photoelectric interactions increase with what kVp?

A

lower kVp

48
Q

the chance of a photoelectric interaction decreases with what kVp?

A

increase in kVp

49
Q

there are more Compton interactions with what kVp?

A

increase in kVp

50
Q

there is a decrease in the chance of Compton interactions happening with what kVp?

A

increase in kVp

51
Q

Increasing tissue thickness does what to beam attenuation?

A

increased attenuation

52
Q

factors that affect beam attenuation (4)

A

tissue thickness
type of tissue
tissue density
x-ray beam quality

53
Q

X-rays are attenuated exponentially and reduced about 50% for each _____ cm of tissue thickness

A

4-5

54
Q

increase in tissue atomic number does what to beam attenuation?

A

increases attenuation

55
Q

What is unwanted exposure on the image caused by scatter?

A

fog

56
Q

the invisible image that exists on the exposed IR before it’s processed

A

latent image

57
Q

the visible image on IR after processing

A

manifest image

58
Q

(T/F) digital images are composed of numeric data that can be easily manipulated by a computer

A

true

59
Q

(T/F) quality is improved with a smaller matrix size that includes a greater number of pixels

A

false
larger matrix

60
Q

What increases as the matrix increases? (3)

A

computer processing time
network transmission time
digital storage space

61
Q

the numeric value assigned to each pixel is determined by the

A

relative attenuation of X-ray

62
Q

each pixel has a ________ that controls the exact pixel brightness (gray level) that can be specified

A

bit depth

63
Q

Photons that travel through tissue to reach the IR

A

transmission

64
Q

Photons exiting the patient to form the image on the IR

A

Remnant

65
Q

A tissue with a high what would absorb more photons

A

Atomic number

66
Q

What results in a nuclear fragment being emitted

A

Photodisintegration

67
Q

Photons formed somewhere other than the target

A

Off focus

68
Q

Where patient does is highest

A

Skin entrance

69
Q

Emits a positron and an electron having 0.51 MeV

A

Pair production

70
Q

There is no ionization with this interaction

A

Coherent scatter

71
Q

The reduction in the number of photons as they pass through matter

A

Attenuation

72
Q

This results in the whites on the radiographic image

A

Photoelectric

73
Q

Refers to how tightly molecules are bonded in an sonic structure

A

Tissue density

74
Q

The ______ energy is equal to the difference between the incident photon and the burning energy of the inner-shell electron

A

Ejected electron

75
Q

Photoelectric absorption is predominant at what kVp levels and increases image contrast

A

Lower

76
Q

Compton scattering becomes the predominate interaction at what kVp levels?

A

High

77
Q

Compton only depends on what and not what?

A

Depends on the energy of the incoming photon
Not the atomic number of the anatomic tissue

78
Q

photoelectric depends on what two things?

A
  • the energy of the incoming electron
  • the atomic number of the tissue
79
Q

with higher kVp the percentage of photoelectric does what, and Compton interactions?

A

Photoelectric interactions decreases
Compton interactions Increases

80
Q

x-rays are attenuated exponentially and generally reduced by how much for each 4-5 cm of tissue thickness?

A

50%

81
Q

Higher penetrating X-rays have what wavelength and what frequency?

A

shorter wavelength
higher frequency

82
Q

Fluoroscopy can be visualized with what two things?

A

flat panel detector or image intensifier

83
Q

How much of the primary beam X-ray beam interacting with the anatomical part reaches the IR

A

Less than 5%

84
Q

Classical interactions has an energy of

A

Less than 10 keV

85
Q

Compton scattering occurs with what energy photons

A

Moderate energy X-ray photons
20-40 keV

86
Q

Photoelectric interactions occur with what diagnostic range

A

20-120 keV

87
Q

Photodisintegration occurs with what photon energy

A

More than 10 MeV

88
Q

(T/F) the remaining photon from Compton scattering may leave the anatomic part to interact with the IR

A

true

89
Q

matter per unit volume or the compactness of the atomic particles composing the anatomic part

A

tissue density

Rad105 (6 decks)

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