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X-RAY INTERACTION WITH MATTER & XRAY EMISSION Flashcards

1
Q

What is X-ray quantity?

A

The number of X-rays in the useful beam

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2
Q

What happens to mAs when SID increases?

A

mAs must increase by SID^2 to maintain constant exposure

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3
Q

What is the best method for specifying X-ray quality?

A

Half-value layer (HVL)

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4
Q

What are the units of X-ray intensity?

A

R, mR, and mGya

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5
Q

What is the SI unit for measuring X-ray quantity?

A

mGya

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6
Q

What is the relationship between X-ray quantity and mAs?

A

Proportional

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7
Q

What is the formula for X-ray quantity and mAs?

A

I1/I1=MAS1/MAS2

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8
Q

What is the relationship between X-ray quantity and kVp?

A

Proportional to kVp^2

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9
Q

What is beam hardening?

A

Reducing low-energy X-rays through filtration

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10
Q

What is X-ray quality?

A

The penetrability of the X-ray beam

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11
Q

How is X-ray quality measured?

A

By the half-value layer (HVL)

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12
Q

The thickness of material needed to reduce X-ray intensity to half its original value

A

half-value layer

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13
Q

What is attenuation?

A

Reduction in X-ray intensity due to absorption and scattering

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14
Q

How is HVL determined?

A

Using an X-ray tube, radiation detector, and graded thicknesses of filters

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15
Q

What is the effect of increasing mAs on X-ray quality?

A

None

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16
Q

What is the effect of increasing mAs on X-ray quantity?

A

Increased

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17
Q

What is the effect of increasing kVp on X-ray quality?

A

Increased penetrability

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18
Q

What is the effect of increasing kVp on X-ray quantity?

A

Increased

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19
Q

What are the types of filtration in X-ray tubes?

A

Inherent and added filtration

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20
Q

What is the total filtration in diagnostic X-ray systems?

A

2.5 mm Al

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21
Q

A filter designed to shape the X-ray beam intensity

A

compensating filter

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22
Q

What is a wedge filter used for?

A

Examination of the foot

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23
Q

What is a bow-tie filter used for?

A

CT imaging systems

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24
Q

What is a trough filter used for?

A

Chest radiography

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25
What are the five X-ray interactions with matter?
Coherent scattering Compton scattering photoelectric effect pair production photodisintegration
26
What is coherent scattering?
Interaction where X-rays change direction without energy change
27
At what energy does coherent scattering occur?
Below 10 keV
28
Interaction of X-rays with outer-shell electrons, ejecting them
Compton scattering
29
What is a photoelectron?
The ejected electron in the photoelectric effect
30
What is the photoelectric effect?
Total absorption of X-rays by inner-shell electrons
31
What is pair production?
Conversion of X-ray energy into an electron and positron
32
What energy level is required for pair production?
1.02 MeV
33
What is photodisintegration?
X-rays absorbed by the nucleus, emitting a nucleon
34
At what energy level does photodisintegration occur?
10 MeV
35
What is the relationship between the photoelectric effect and atomic number?
Proportional to the cube of the atomic number (Z³)
36
Variations in X-ray absorption in tissues, creating image contrast
differential absorption
37
How does mass density affect X-ray interaction?
Proportional increase in both Compton and photoelectric interactions
38
What are the contrast agents used in radiology?
Positive: Barium and iodine Negative: Air
39
What is exponential attenuation?
Total reduction in X-rays due to absorption and scattering
40
General graying of the image that reduces contrast
image noise
41
What interaction produces image noise?
Compton scattering
42
What is the primary factor that reduces image contrast?
Compton scattering
43
What is backscatter radiation?
X-rays scattered back toward the incident beam direction
44
What is attenuation the product of?
Absorption and scattering
45
What is the relationship between X-ray energy and Compton scattering probability?
Inversely proportional (1/E)
46
What happens to photoelectric interactions as X-ray energy increases?
decrease proportionally
47
What is the effect of tissue atomic number on Compton scattering?
No effect (independent of atomic number)
48
What is the effect of tissue atomic number on the photoelectric effect?
Proportional to 𝑍^3
49
What is the relationship between mass density and X-ray interaction?
Proportional increase in both Compton and photoelectric interactions
50
What is the main characteristic of low-kVp technique in imaging?
Produces high-contrast radiographs
51
What is high-kVp technique used for?
Outlining organs and penetrating contrast media
52
What is a double contrast examination?
Imaging using air and barium for contrast
53
Conversion of electron and positron mass into energy
annihilation radiation
54
What are the effective atomic numbers (Z) for fat, soft tissue, and bone?
Fat: 6.3 Soft Tissue: 7.4 Bone: 13.8
55
What is the effective Z for iodine and barium as contrast materials?
Iodine: 53, Barium: 56
56
What is the main advantage of using positive contrast agents?
They have a higher atomic number than surrounding tissues
57
What is the SI unit of mass density?
kg/m³
58
What is the mass density of lung tissue?
320 kg/m³
59
What is the mass density of soft tissue and muscle?
1,000 kg/m³
60
What is the mass density of bone?
1,850 kg/m³
61
What is the relationship between kVp and differential absorption?
Lower kVp increases differential absorption
62
What is the principal method to image small differences in soft tissue?
Use low kVp to maximize differential absorption
63
What percentage of emitted X-rays contribute to the radiographic image?
Approximately 0.5%
64
What is the function of a step-wedge filter?
Used in special procedures to image long sections of anatomy
65
What is the photoelectric effect most likely to occur with?
Inner-shell electrons
66
What interaction is responsible for radiopaque areas in an image?
Photoelectric effect
67
What interaction is responsible for radiolucent areas in an image?
Transmission of X-rays without interaction
68
Why is beryllium used for the window in mammography?
Its low atomic number allows transmission of low-energy X-rays
69
What is the typical inherent filtration equivalent in X-ray systems?
0.5 mm Al
70
What is the purpose of added filtration in X-ray systems?
Improves beam quality by removing low-energy X-rays
71
What is the total filtration requirement for diagnostic X-ray systems?
2.5 mm Al
72
What is a compensating filter designed for?
To make the remnant beam more uniform in intensity
73
What type of filter is used for chest radiography?
Trough filter
74
What is the significance of gadolinium and holmium in filtration?
High atomic numbers improve filtration efficiency
75
What interaction does not occur during diagnostic radiology?
Pair production and photodisintegration
76
What type of X-ray interaction occurs with low-energy X-rays?
Coherent scattering
77
What is the main disadvantage of increased kVp?
Reduced image contrast
78
What happens to the X-ray beam when filtration is increased?
Beam quality increases, but quantity decreases
79
What is the typical range of HVL for diagnostic X-ray beams?
3-5 mm Al or 3-6 cm of soft tissue
80
What does increasing filtration do to patient dose?
Reduces patient dose by removing low-energy X-rays
81
What is the function of a conic filter?
Used in digital fluoroscopy
82
What materials are commonly used for compensating filters?
Aluminum, copper, or a combination of materials
83
What does a wedge filter do?
Shapes the X-ray beam for uniform imaging of uneven anatomy
84
How does increasing atomic number affect X-ray absorption?
Increases absorption due to higher photoelectric effect probability
85
Why is air used as a negative contrast agent?
agent? Its low atomic number reduces absorption, creating contrast
86
What is the primary reason for using barium in GI imaging?
Its high atomic number and mass density provide excellent contrast
87
What is the relationship between photon energy and wavelength?
Higher energy corresponds to shorter wavelength
88
What is the effect of increased mass density on X-ray transmission?
Reduces X-ray transmission
89
What is the energy of annihilation radiation?
0.511 MeV per photon
90
What is the effective atomic number (Z) of human soft tissue?
7.4

C1 (9 decks)

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