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C1 > XRAY TUBE AND XRAY PRODUCTION > Flashcards

XRAY TUBE AND XRAY PRODUCTION Flashcards

1
Q

What type of enclosure is used in X-ray tubes?

A

Glass or metal enclosure

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2
Q

What type of device is an X-ray tube?

A

A special type of diode (anode and cathode)

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3
Q

What is the main function of an X-ray tube?

A

Converts electrical energy into electromagnetic energy

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4
Q

What are the three main external components of an X-ray tube?

A

Support structure, protective housing, and glass/metal enclosure

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5
Q

What is the most frequently used X-ray tube support system?

A

Ceiling-support system

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6
Q

What does the preferred detent position mean?

A

When the X-ray tube is centered above the examination table at the standard SID

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7
Q

What is the function of protective housing in X-ray tubes?

A

Insulates against electric shock, dissipates heat, and supports the tube mechanically

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8
Q

What is isotropic emission in X-ray tubes?

A

Emission with equal intensity in all directions

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9
Q

What is leakage radiation?

A

X-rays that escape through protective housing

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10
Q

What is the primary material used for the glass enclosure in X-ray tubes?

A

Pyrex glass

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11
Q

What are the advantages of metal enclosures in X-ray tubes?

A

Longer tube life and constant electric potential

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12
Q

What are the two primary parts of the cathode in an X-ray tube?

A

Filament and focusing cup

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13
Q

What material is the filament in an X-ray tube made of?

A

Thoriated tungsten

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14
Q

What is the role of the focusing cup in an X-ray tube?

A

Surrounds the filament and controls electron flow

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15
Q

What is space charge in the context of X-ray tubes?

A

A cloud of electrons emitted by the filament

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16
Q

What is the space charge effect?

A

Difficulty emitting subsequent electrons due to electrostatic repulsion

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17
Q

What is the saturation current in an X-ray tube?

A

The maximum filament current when all electrons are used

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18
Q

What is the focal spot in an X-ray tube?

A

The region of the anode target where electrons produce X-rays

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19
Q

What are the sizes of focal spots typically used?

A

Small (0.1-1 mm) and large (0.3-2 mm)

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20
Q

What material is commonly used for the anode in X-ray tubes?

A

tungsten

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21
Q

What are the three primary functions of the anode?

A

Conducts electricity, dissipates heat, and provides mechanical support

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22
Q

What is the main cause of tube failure in X-ray systems?

A

Tungsten vaporization and arcing

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23
Q

A design to allow a large area for heating while maintaining a small focal spot

A

line focus principle

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24
Q

What is the anode heel effect?

A

Greater radiation intensity on the cathode side compared to the anode side

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25
Q

X-rays produced outside the focal spot

A

off-focus radiation

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26
Q

What are the three ways heat is dissipated in an X-ray tube?

A

Radiation, conduction, and convection

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27
Q

What causes damage to the rotor assembly in X-ray tubes?

A

Excessive heat during long exposure times

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28
Q

What is the unit for heat energy in X-ray applications?

A

Heat units (HU)

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29
Q

What is the formula for heat units in a single-phase system?

A

HU = kVp × mA × s

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30
Q

What is the formula for heat units in a high-frequency system?

A

HU = 1.45 × kVp × mA × s

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31
Q

What is the difference between characteristic and bremsstrahlung X-rays?

A

Characteristic X-rays are discrete, while bremsstrahlung X-rays have a continuous spectrum

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32
Q

What is the efficiency of X-ray production dependent on?

A

Tube voltage (kVp)

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33
Q

What happens when target material atomic number increases?

A

Efficiency and energy of X-rays increase

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34
Q

Reduces low-energy X-rays, increasing the average energy of the beam

A

added filtration

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35
Q

What does a radiographic rating chart indicate?

A

Safe and unsafe radiographic techniques

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36
Q

X-rays produced when electrons are slowed by the target nucleus

A

bremsstrahlung radiation

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37
Q

X-rays produced when an outer electron fills an inner-shell void

A

characteristic radiation

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38
Q

Electrons traveling from the cathode to the anode

A

projectile electron

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39
Q

What is the main purpose of a rotating anode?

A

Provides a larger target area and dissipates heat more effectively

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40
Q

What materials are used in mammographic targets?

A

Molybdenum (Z=42) and Rhodium (Z=45)

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41
Q

What is the typical rotation speed of a rotating anode?

A

3,600 to 10,000 rpm

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42
Q

Connects the anode to the rotor while minimizing heat conduction

A

anode stem

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43
Q

What is the material used for the anode stem?

A

Molybdenum

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44
Q

What are the two principal parts of an electromagnetic induction motor in an X-ray tube?

A

Stator and rotor

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45
Q

Where is the stator located in an X-ray tube?

A

Outside the enclosure

46
Q

Where is the rotor located in an X-ray tube?

A

Inside the glass envelope

47
Q

What is the coast time of the rotor?

A

Approximately 60 seconds

48
Q

How does the line focus principle affect the effective focal spot?

A

Decreases its size compared to the actual focal spot

49
Q

What happens to the anode heel effect as the target angle decreases?

A

The heel effect becomes more pronounced

50
Q

What is the central ray in X-ray imaging?

A

The imaginary line generated by the centermost X-ray in the beam

51
Q

What are the consequences of off-focus radiation?

A

Increases skin dose, reduces image contrast, and exposes unintended tissues

52
Q

How can off-focus radiation be reduced?

A

Using a fixed diaphragm or a metal enclosure X-ray tube

53
Q

What is the most frequent cause of abrupt tube failure?

A

Electron arcing due to vaporized tungsten

54
Q

What is the primary cause of filament failure in X-ray tubes?

A

Tungsten vaporization

55
Q

What are the three types of rating charts used in X-ray systems?

A

Radiographic rating chart, anode cooling chart, and housing cooling chart

56
Q

What does the radiographic rating chart specify?

A

Safe exposure levels for X-ray tube operation

57
Q

Determines thermal capacity and heat dissipation of the anode

A

anode cooling chart

58
Q

Hardens the X-ray beam by removing low-energy X-rays

A

added filtration

59
Q

What is the discrete spectrum in X-ray emission?

A

Contains specific values, such as characteristic X-rays

60
Q

What is the continuous spectrum in X-ray emission?

A

Contains all possible values, such as bremsstrahlung X-rays

61
Q

The average energy of the X-ray photons in the beam

A

effective energy

62
Q

How does an increase in tube current affect the X-ray emission spectrum?

A

Increases the amplitude of the spectrum

63
Q

What is the rule of thumb for kVp and mAs?

A

A 15% increase in kVp is equivalent to doubling the mAs

64
Q

What is the effect of added filtration on the X-ray beam?

A

Reduces quantity but increases average energy

65
Q

What is the effect of increasing the target atomic number?

A

Increases both the quality and quantity of X-rays produced

66
Q

What is the effect of voltage ripple on X-ray beam quality and quantity?

A

Reduces both quality and quantity

67
Q

What are the key factors affecting X-ray emission spectra?

A

Tube current, tube voltage, added filtration, target material, and voltage waveform

68
Q

How does the target material affect the X-ray spectrum?

A

Higher atomic number increases efficiency and shifts the spectrum to higher energies

69
Q

What are the main causes of anode damage in X-ray tubes?

A

Excessive heat, long exposure times, and single excessive exposures

70
Q

How does tube voltage affect the X-ray emission spectrum?

A

Increases both amplitude and position

71
Q

What is bremsstrahlung radiation commonly referred to as?

A

“Slowed down” radiation

72
Q

How is the quantity of X-rays measured?

A

By the area under the X-ray emission spectrum curve

73
Q

What is the formula for calculating HU in a three-phase 6-pulse system?

A

HU = 1.35 × kVp × mA × s

74
Q

What is the formula for calculating HU in a three-phase 12-pulse system?

A

HU = 1.41 × kVp × mA × s

75
Q

What type of X-rays are predominant in the diagnostic range?

A

Bremsstrahlung X-rays

76
Q

Why are K-characteristic X-rays important for imaging?

A

They have fixed energies specific to the target element

77
Q

What does the stator in the induction motor do?

A

Produces a magnetic field to rotate the rotor

78
Q

What happens to the intensity of X-rays on the cathode side due to the anode heel effect?

A

Intensity is higher on the cathode side

79
Q

What is the purpose of using a rotating anode?

A

To distribute heat over a larger surface area

80
Q

What is the primary interaction for heat production in the anode?

A

Outer-shell electron excitation and return

81
Q

How does increasing kVp affect the efficiency of X-ray production?

A

Efficiency increases with higher kVp

82
Q

What type of cooling is used to dissipate heat from the housing of an X-ray tube?

A

Convection cooling

83
Q

What is the melting point of tungsten used in X-ray tube targets?

A

3,410°C

84
Q

What is the main disadvantage of a glass enclosure compared to a metal enclosure?

A

Shorter tube life and greater likelihood of failure

85
Q

What does thermionic emission refer to in X-ray tubes?

A

Electron emission due to heating of the filament

86
Q

What additional element is mixed with tungsten in filaments to enhance efficiency?

A

Thorium (1-2%)

87
Q

What is the principal advantage of a small focal spot in X-ray imaging?

A

Improved spatial resolution

88
Q

What determines the effectiveness of the focusing cup?

A

Its size, shape, charge, filament size, and position

89
Q

What is the primary source of arcing in X-ray tubes?

A

Vaporized tungsten depositing on the enclosure

90
Q

What causes “pitting” in an X-ray tube target?

A

A single excessive exposure

91
Q

What is the purpose of a stationary anode in dental and portable X-ray systems?

A

Used when high tube current and power are not required

92
Q

What does the rotor do in the induction motor of an X-ray tube?

A

Rotates the anode

93
Q

What is the average cooling time for the housing of an X-ray tube?

A

1-2 hours

94
Q

What is the limiting factor for small focal spots?

A

Heat concentration on a smaller area of the target

95
Q

X-rays emitted through the window of the protective housing

A

useful beam

96
Q

How does added filtration affect the characteristic spectrum?

A

It does not affect the characteristic spectrum

97
Q

What is the purpose of a heat unit (HU) in X-ray applications?

A

Measures the heat energy generated during X-ray production

98
Q

What is the main advantage of using a high-frequency X-ray generator?

A

Higher efficiency and reduced voltage ripple

99
Q

What is a “grid-controlled” X-ray tube?

A

An X-ray tube where the focusing cup acts as an exposure switch

100
Q

What determines the energy of bremsstrahlung X-rays?

A

The energy of the projectile electron

101
Q

What happens to bremsstrahlung X-rays at higher projectile electron energies?

A

Their maximum energy increases

102
Q

What is the function of the central ray in X-ray imaging?

A

It determines the center of the X-ray beam

103
Q

How does increased target angle affect the effective focal spot?

A

It increases the size of the effective focal spot

104
Q

What is the main source of heat in an X-ray tube?

A

Interactions between outer-shell electrons and the anode

105
Q

What are the common materials used for rotating anode targets?

A

Tungsten, molybdenum, and graphite

106
Q

What is the significance of a high atomic number (Z) in target materials?

A

Higher Z increases X-ray production efficiency and energy

107
Q

What is the purpose of the added mechanical strength from rhenium in the target?

A

To withstand high-speed rotation and thermal expansion/contraction

108
Q

What does “off-focus radiation” result in?

A

Reduced image contrast and increased skin dose

109
Q

What is the effect of decreasing the anode angle on the field size?

A

The X-ray field size becomes smaller

110
Q

Why is molybdenum used in the anode stem?

A

Poor heat conductor to minimize heat transfer to the rotor

C1 (9 decks)

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