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Rad105 > Test 3 - Chpt 7, 8 > Flashcards

Test 3 - Chpt 7, 8 Flashcards

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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
Increasing kVp = # of Compton interactions does what and probability does what?
interactions increase, and probability decreases
26
decreasing kVp = # of photoelectric interactions does what and probability does what?
interactions increase, probaility compared to Compton increases
27
Interaction that results in the incident photon having enough energy to not interact with the electrons but interacts with the nucleus instead
pair production
28
What two things are produced from pair production?
positron and an electron
29
Pair production is AKA
annihilation reaction
30
for the positron and electron particles of a pair production interaction to exist they must have what energy?
0.51 MeV each (the energy equivalent of an electron)
31
What happens to the electron from a pair production interaction?
goes through many interactions before resting in another atom
32
What happens to the positron from a pair production interaction?
travels until it strikes an electron and causes an annihilation event (positron and electron are destroyed, converting their energy into 2 x-ray photons)
33
How does photodisintegration occur?
when photons with super high energies strike the nucleus of the atom and make it unstable
34
During photodisintegration, how does the nucleus of the atom become stable?
it ejects a nuclear particle
35
What is differential absorption?
difference between x-ray photons that are absorbed photo-electrically versus those that penetrate the body
36
What is it called when X-ray photons pass through the body and reach the IR?
transmission
37
What is it called when photons are absorbed by the body and don't reach the IR?
absorption
38
When an X-ray photon interacts with a macromolecule the energy may manifest as a change to what?
As a change to the structure of the macromolecule
39
The 3 most common effects of differential absorption
main-chain scission cross-linking point lesions
40
(T/F) the composition of the anatomic tissues affects the x-ray beam interaction
true
41
What creates an image that structurally represents the anatomic area?
differential absorption (transmission and absorption)
42
Do anatomic parts absorb the primary beam to the same degree?
No
43
What is the reduction in the energy or number of photons in the primary x-ray beam?
attenuation
44
what occurs as a result of the photon interactions with the atomic structures that compose the tissues?
attenuation
45
What 2 processes occur in the diagnostic range?
absorption and scattering
46
total photon absorption depends on what?
the energy of the incoming x-ray photon and the atomic number of anatomic tissue
47
photoelectric interactions increase with what kVp?
lower kVp
48
the chance of a photoelectric interaction decreases with what kVp?
increase in kVp
49
there are more Compton interactions with what kVp?
increase in kVp
50
there is a decrease in the chance of Compton interactions happening with what kVp?
increase in kVp
51
Increasing tissue thickness does what to beam attenuation?
increased attenuation
52
factors that affect beam attenuation (4)
tissue thickness type of tissue tissue density x-ray beam quality
53
X-rays are attenuated exponentially and reduced about 50% for each _____ cm of tissue thickness
4-5
54
increase in tissue atomic number does what to beam attenuation?
increases attenuation
55
What is unwanted exposure on the image caused by scatter?
fog
56
the invisible image that exists on the exposed IR before it's processed
latent image
57
the visible image on IR after processing
manifest image
58
(T/F) digital images are composed of numeric data that can be easily manipulated by a computer
true
59
(T/F) quality is improved with a smaller matrix size that includes a greater number of pixels
false larger matrix
60
What increases as the matrix increases? (3)
computer processing time network transmission time digital storage space
61
the numeric value assigned to each pixel is determined by the
relative attenuation of X-ray
62
each pixel has a ________ that controls the exact pixel brightness (gray level) that can be specified
bit depth
63
Photons that travel through tissue to reach the IR
transmission
64
Photons exiting the patient to form the image on the IR
Remnant
65
A tissue with a high what would absorb more photons
Atomic number
66
What results in a nuclear fragment being emitted
Photodisintegration
67
Photons formed somewhere other than the target
Off focus
68
Where patient does is highest
Skin entrance
69
Emits a positron and an electron having 0.51 MeV
Pair production
70
There is no ionization with this interaction
Coherent scatter
71
The reduction in the number of photons as they pass through matter
Attenuation
72
This results in the whites on the radiographic image
Photoelectric
73
Refers to how tightly molecules are bonded in an sonic structure
Tissue density
74
The ______ energy is equal to the difference between the incident photon and the burning energy of the inner-shell electron
Ejected electron
75
Photoelectric absorption is predominant at what kVp levels and increases image contrast
Lower
76
Compton scattering becomes the predominate interaction at what kVp levels?
High
77
Compton only depends on what and not what?
Depends on the energy of the incoming photon Not the atomic number of the anatomic tissue
78
photoelectric depends on what two things?
- the energy of the incoming electron - the atomic number of the tissue
79
with higher kVp the percentage of photoelectric does what, and Compton interactions?
Photoelectric interactions decreases Compton interactions Increases
80
x-rays are attenuated exponentially and generally reduced by how much for each 4-5 cm of tissue thickness?
50%
81
Higher penetrating X-rays have what wavelength and what frequency?
shorter wavelength higher frequency
82
Fluoroscopy can be visualized with what two things?
flat panel detector or image intensifier
83
How much of the primary beam X-ray beam interacting with the anatomical part reaches the IR
Less than 5%
84
Classical interactions has an energy of
Less than 10 keV
85
Compton scattering occurs with what energy photons
Moderate energy X-ray photons 20-40 keV
86
Photoelectric interactions occur with what diagnostic range
20-120 keV
87
Photodisintegration occurs with what photon energy
More than 10 MeV
88
(T/F) the remaining photon from Compton scattering may leave the anatomic part to interact with the IR
true
89
matter per unit volume or the compactness of the atomic particles composing the anatomic part
tissue density

Rad105 (6 decks)

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