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C1 > X-RAY INTERACTION WITH MATTER & XRAY EMISSION > Flashcards

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
Q

What are the five X-ray interactions with matter?

A

Coherent scattering
Compton scattering
photoelectric effect
pair production
photodisintegration

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26
Q

What is coherent scattering?

A

Interaction where X-rays change direction without energy change

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27
Q

At what energy does coherent scattering occur?

A

Below 10 keV

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28
Q

Interaction of X-rays with outer-shell electrons, ejecting them

A

Compton scattering

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29
Q

What is a photoelectron?

A

The ejected electron in the photoelectric effect

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30
Q

What is the photoelectric effect?

A

Total absorption of X-rays by inner-shell electrons

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31
Q

What is pair production?

A

Conversion of X-ray energy into an electron and positron

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32
Q

What energy level is required for pair production?

A

1.02 MeV

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33
Q

What is photodisintegration?

A

X-rays absorbed by the nucleus, emitting a nucleon

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34
Q

At what energy level does photodisintegration occur?

A

10 MeV

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35
Q

What is the relationship between the photoelectric effect and atomic number?

A

Proportional to the cube of the atomic number (Z³)

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36
Q

Variations in X-ray absorption in tissues, creating image contrast

A

differential absorption

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37
Q

How does mass density affect X-ray interaction?

A

Proportional increase in both Compton and photoelectric interactions

38
Q

What are the contrast agents used in radiology?

A

Positive: Barium and iodine
Negative: Air

39
Q

What is exponential attenuation?

A

Total reduction in X-rays due to absorption and scattering

40
Q

General graying of the image that reduces contrast

A

image noise

41
Q

What interaction produces image noise?

A

Compton scattering

42
Q

What is the primary factor that reduces image contrast?

A

Compton scattering

43
Q

What is backscatter radiation?

A

X-rays scattered back toward the incident beam direction

44
Q

What is attenuation the product of?

A

Absorption and scattering

45
Q

What is the relationship between X-ray energy and Compton scattering probability?

A

Inversely proportional (1/E)

46
Q

What happens to photoelectric interactions as X-ray energy increases?

A

decrease proportionally

47
Q

What is the effect of tissue atomic number on Compton scattering?

A

No effect (independent of atomic number)

48
Q

What is the effect of tissue atomic number on the photoelectric effect?

A

Proportional to 𝑍^3

49
Q

What is the relationship between mass density and X-ray interaction?

A

Proportional increase in both Compton and photoelectric interactions

50
Q

What is the main characteristic of low-kVp technique in imaging?

A

Produces high-contrast radiographs

51
Q

What is high-kVp technique used for?

A

Outlining organs and penetrating contrast media

52
Q

What is a double contrast examination?

A

Imaging using air and barium for contrast

53
Q

Conversion of electron and positron mass into energy

A

annihilation radiation

54
Q

What are the effective atomic numbers (Z) for fat, soft tissue, and bone?

A

Fat: 6.3
Soft Tissue: 7.4
Bone: 13.8

55
Q

What is the effective Z for iodine and barium as contrast materials?

A

Iodine: 53, Barium: 56

56
Q

What is the main advantage of using positive contrast agents?

A

They have a higher atomic number than surrounding tissues

57
Q

What is the SI unit of mass density?

A

kg/m³

58
Q

What is the mass density of lung tissue?

A

320 kg/m³

59
Q

What is the mass density of soft tissue and muscle?

A

1,000 kg/m³

60
Q

What is the mass density of bone?

A

1,850 kg/m³

61
Q

What is the relationship between kVp and differential absorption?

A

Lower kVp increases differential absorption

62
Q

What is the principal method to image small differences in soft tissue?

A

Use low kVp to maximize differential absorption

63
Q

What percentage of emitted X-rays contribute to the radiographic image?

A

Approximately 0.5%

64
Q

What is the function of a step-wedge filter?

A

Used in special procedures to image long sections of anatomy

65
Q

What is the photoelectric effect most likely to occur with?

A

Inner-shell electrons

66
Q

What interaction is responsible for radiopaque areas in an image?

A

Photoelectric effect

67
Q

What interaction is responsible for radiolucent areas in an image?

A

Transmission of X-rays without interaction

68
Q

Why is beryllium used for the window in mammography?

A

Its low atomic number allows transmission of low-energy X-rays

69
Q

What is the typical inherent filtration equivalent in X-ray systems?

A

0.5 mm Al

70
Q

What is the purpose of added filtration in X-ray systems?

A

Improves beam quality by removing low-energy X-rays

71
Q

What is the total filtration requirement for diagnostic X-ray systems?

A

2.5 mm Al

72
Q

What is a compensating filter designed for?

A

To make the remnant beam more uniform in intensity

73
Q

What type of filter is used for chest radiography?

A

Trough filter

74
Q

What is the significance of gadolinium and holmium in filtration?

A

High atomic numbers improve filtration efficiency

75
Q

What interaction does not occur during diagnostic radiology?

A

Pair production and photodisintegration

76
Q

What type of X-ray interaction occurs with low-energy X-rays?

A

Coherent scattering

77
Q

What is the main disadvantage of increased kVp?

A

Reduced image contrast

78
Q

What happens to the X-ray beam when filtration is increased?

A

Beam quality increases, but quantity decreases

79
Q

What is the typical range of HVL for diagnostic X-ray beams?

A

3-5 mm Al or 3-6 cm of soft tissue

80
Q

What does increasing filtration do to patient dose?

A

Reduces patient dose by removing low-energy X-rays

81
Q

What is the function of a conic filter?

A

Used in digital fluoroscopy

82
Q

What materials are commonly used for compensating filters?

A

Aluminum, copper, or a combination of materials

83
Q

What does a wedge filter do?

A

Shapes the X-ray beam for uniform imaging of uneven anatomy

84
Q

How does increasing atomic number affect X-ray absorption?

A

Increases absorption due to higher photoelectric effect probability

85
Q

Why is air used as a negative contrast agent?

A

agent? Its low atomic number reduces absorption, creating contrast

86
Q

What is the primary reason for using barium in GI imaging?

A

Its high atomic number and mass density provide excellent contrast

87
Q

What is the relationship between photon energy and wavelength?

A

Higher energy corresponds to shorter wavelength

88
Q

What is the effect of increased mass density on X-ray transmission?

A

Reduces X-ray transmission

89
Q

What is the energy of annihilation radiation?

A

0.511 MeV per photon

90
Q

What is the effective atomic number (Z) of human soft tissue?

A

7.4

C1 (9 decks)

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