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Radiology > Production of X-rays part 1 > Flashcards

Production of X-rays part 1 Flashcards

1
Q

What are the two parts of the tubehead?

A

x-ray tube
power supply (generator)

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2
Q

What buttons are on the control panel?

A

Exposure time, kVp and mA selectors

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3
Q

What type of exposure button do we use?

A

dead-man type (if you take finger off it stops exposure)

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4
Q

What three things are required on the control panel?

A
  • dead-man type exposure button
  • indicator light
  • audible signal
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5
Q

What is in the tube head?

A

Power supply + x-ray tube

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6
Q

What transformer is on the cathode (-) side?

A

step-down transformer

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7
Q

What transformer is on the anode (+) side?

A

step-up transformer

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8
Q

X-rays are produced by the anode or cathode?

A

anode

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9
Q

Electrons are produced by the anode or cathode?

A

cathode

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10
Q

What does the step-up transformer do?

A

raises voltage

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11
Q

What does the step-down transformer do?

A

lowers voltage

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12
Q

What are the parts of the tube head besides the power supply and x-ray tube?

A

◦ Glass envelope
◦ Insulating oil
◦ Metal housing
◦ Tube window
◦ Aluminum filters
◦ Lead collimator

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13
Q

What does the insulating oil in the tube head do?

A

disperse heat

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14
Q

What does the lead collimator do in the tube head?

A

determines final shape of the x-rays

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15
Q

What do the aluminum filters do in the tube head?

A

filters the x-rays that are not useful (don’t go to patient)

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16
Q

What is the space called inside the x-ray tube?

A

vacuum

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17
Q

What are the two main parts of the cathode (-)?

A

filament
focusing cup

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18
Q

What is the filament made of?

A

tungsten

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19
Q

What is the focusing cup made of?

A

molybdenum

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20
Q

What is the source of electrons?

A

filament

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21
Q

How does the filament generate electrons?

A

Is heated with a low voltage source and emits electrons at a rate proportional to its temperature (thermionic emission)

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22
Q

What is the charge of the focusing cup?

A

negative charge

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23
Q

What does the focusing cup do?

A

Focuses the electrons into a narrow beam directed to the focal spot (+)

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24
Q

What is thermionic emission?

A

emits electrons at a rate proportional to its temperature

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25
Q

What are the two parts of the anode (+)?

A
  • tungsten target
  • copper stem
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26
Q

What does the copper stem do?

A

Works as a thermal conductor to remove the heat from the tungsten avoiding target melting

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27
Q

What does the tungsten target do?

A

Transform the kinetic energy of the colliding electrons into x-ray photons

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28
Q

What produces the x-rays?

A

x-rays produced on the focal spot on the tungsten target (anode)

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29
Q

Is the tungsten target efficient or inefficient at producing x-rays?

A

Highly inefficient: produces 99% heat and 1% x-rays

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30
Q

Why is tungsten a good target material?

A
  1. High atomic number: efficient production of x-rays
  2. High melting point
  3. High thermal conductivity: to dissipate the heat produced away from the target
  4. Low vapor pressure: helps maintain vacuum in the tube at high temperatures.
  5. Cheap
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31
Q

What are the conditions necessary for x-ray production?

A

1.Separation of electrons
2.Production of high-speed electrons
3.Concentration of electrons
4.Sudden stoppage of electron stream

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32
Q

What allows for the separation of electrons?

A

Low voltage filament current heats the tungsten filament to incandescence with resultant separation of outer shell electrons from the tungsten atom (thermionic emission)

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33
Q

What allows for the production of high-speed electrons?

A

High potential difference is produced between the cathode and anode by applying a high voltage between them

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34
Q

What allows for the concentration of electrons?

A

Electron beam is focused by the focusing cup (negative charge) and directed towards the focal spot

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35
Q

What allows for the sudden stoppage of electron stream?

A

Upon striking the focal spot in the anode, the electron stream is stopped abruptly, and kinetic energy of the electron stream undergoes conversion to greater than 99% heat and less than 1% x-radiation

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36
Q

What is the focal spot?

A

Area on the target to which the focusing cup directs the electrons and from which the x-rays are produced

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37
Q

Size of the _________ is important for image quality

A

focal spot

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38
Q

smaller focal spot, _____ spatial
resolution

A

higher

39
Q

smaller the focal spot → _____ heat accumulates

A

more

40
Q

Inclining the tungsten target does what to do the focal point?

A

smaller focal point

41
Q

What are two ways to alter the focal point heat problem?

A
  1. Rotating anodes
  2. Stationary anodes (line- focus principle)
42
Q

What is a rotating anode?

A

Allows heat at the focal spot to spread out over a large surface (medical devices mostly)

43
Q

What is the line-focus principle (stationary anode)?

A

Angling the target to achieve a smaller effective focal spot than the actual focal spot

  • Results in sharper radiographic image while maintaining the original surface area of the target for heat dissipation
44
Q

What is the actual focal spot?

A

the projection of the focal spot perpendicular to the target

45
Q

What is the effective focal spot?

A

the projection of the focal spot perpendicular to the electron beam

46
Q

Effective focal spot is always _____ than the actual focal spot

A

smaller

47
Q

What is the average size of the actual focal spot and effective focal spot?

A

actual - 3 mm
effective - 1 mm

48
Q

What are the two functions of the power supply?

A

◦ Provide a low-voltage current to heat the x-ray tube filament (step-down transformer)
◦ Generate a high potential difference to accelerate electrons form the cathode to the focal spot on the anode (step-up transformer)

49
Q

What does a transformer do?

A

Electromagnetic device that either increases or decreases the voltage in a circuit

50
Q

What are the 3 types of transformers?

A

◦ Step-down transformer (filament
transformer)
◦ Step-up transformer (high voltage)
◦ Autotransformer

51
Q

Used to convert 110 or 220 volts to 3-5 volts to heat the filament: step-up or step-down transformer?

A

Step-down transformer

52
Q

Which transformer is regulated by the mA switch?

A

Step-down transformer

53
Q

increasing mA setting will _______
the number of electrons emitted

A

increase

54
Q

Used to convert 110 or 220 volts to 60,000-100,000 volts to move the electrons across the tube: step-up or step-down transformer?

A

Step-up transformer

55
Q

Which transformer is regulated by the kV setting?

A

Step-up transformer

56
Q

Increasing the kV will ________ the energy of the electrons traveling from the cathode to anode

A

increase

57
Q

What does exposure time do?

A

Determines amount of time the high voltage circuit is applied across the x-ray tube (amount of time x-rays are produced)

58
Q

What is the time delay circuit?

A

delay of ½ second to heat the filament

59
Q

What is the timing circuit?

A

Actual time of exposure

60
Q

What does the kV (kilovoltage) do?

A

controls the acceleration of electrons from cathode to anode

61
Q

What does the mA (milliamperage) do?

A

controls heating of the filament

62
Q

What does the exposure time do?

A

controls the time in which x-rays are produced

63
Q
A

glass envelope

64
Q
A

x-ray tube

65
Q
A

power supply - step up transformer

66
Q
A

aluminum filter

67
Q
A

aiming cylinder

68
Q
A

power supply - step down transformer

69
Q
A

collimator

70
Q
A

insulating oil

71
Q
A

anode

72
Q
A

cathode

73
Q
A

cathode

74
Q
A

tube window

75
Q
A

anode

76
Q
A

copper stem

77
Q
A

vacuum

78
Q
A

glass envelope

79
Q
A

focal spot on tungsten target

80
Q
A

Electron focusing cup

81
Q
A

filament and electron cloud

82
Q
A

filament circuit

83
Q
A

aluminum discs

84
Q
A

postion indicating device

85
Q
A

lead collimator

86
Q
A

unleaded glass window of x-ray tube

87
Q
A

insulating oil

88
Q
A

metal housing of x-ray tube head

89
Q
A

anode

90
Q
A

step-up transformer

91
Q
A

x-ray tube

92
Q
A

step-down transformer

93
Q
A

cathode

Radiology (35 decks)

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