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radiology > Radiation Physics and X-ray Machine > Flashcards

Radiation Physics and X-ray Machine Flashcards

1
Q

What is radiation?

A

The emission and propagation of energy through space.

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2
Q

What are the two types of radiation?

A

Particulate and electromagnetic radiation.

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3
Q

What type of radiation is electrons, alpha particles, protons, and neutrons?

A

Particulate radiation

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3
Q

What type of radiation are X-rays?

A

Electromagnetic radiation

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4
Q

What type of radiation is visible light?

A

Electromagnetic radiation

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5
Q

What are the three properties of electromagnetic radiation?

A

Does not have mass
Travel at the speed of light
No electrical charge

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6
Q

What are the two properties of particulate radiation?

A

Has mass
Travel in straight lines at high speed

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7
Q

What type of radiation is a cathode ray?

A

Particulate radiation, high speed electrons originate at x-ray tube

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7
Q

What are the four types of non-ionizing radiation?

A

Radio waves
Microwaves
Infrared
Visible light

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8
Q

What are the three ionizing forms of radiation?

A

Ultraviolet
X-rays
Gamma rays

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9
Q

What is radioactivity?

A

Process of unstable atoms undergo spontaneous disintegration or decay to try to be in a more balanced state

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9
Q

What is the filament in the cathode tube made of?

A

Tungsten

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9
Q

What does the filament sit in the cathode?

A

Focusing cup

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10
Q

What charge is a cathode?

A

Negative

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11
Q

Where are electrons produced?

A

Cathode

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12
Q

What is the function of the focusing cup?

A

Directs electrons in a narrow beam to the anode

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13
Q

What type of anode is used in dentistry?

A

Stationary

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14
Q

What charge is the anode? Why?

A

Positive to attract electrons

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15
Q

What is the focal spot of the anode made up of?

A

Tungsten

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16
Q

What is the stem made up of in the anode?

A

Copper

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17
Q

Is copper or tungsten a better heat conductor?

A

Copper

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18
Q

What surrounds the tube and transformers?

A

Insulating oil

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19
Q

What is the function of the insulating oil?

A

Prevent overheating by absorbing heat

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20
Q

Where is the transformers?

A

In the metal housing

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21
Q

What is the metal housing filled with?

A

Insulating oil

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22
Q

What is the function of the metal housing?

A

Protection of X-ray tube and grounds high voltage components

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23
Q

What is the function of the transformers?

A

Alters the voltage

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24
Q

What is the function of the tube head seal?

A

Permits the exit of x-rays

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25
Q

What is the tube head seal made of?

A

Lead and aluminum

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26
Q

What is the function of the aluminum disk?

A

Filter

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27
Q

What type of photons can penetrate through anatomic structures and each image receptors?

A

High energy photons

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28
Q

What do low energy photons cause?

A

Unnecessary exposure to the patient

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29
Q

How are low energy photons removed?

A

By adding filters

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30
Q

What are the inherent low energy photon filters?

A

X ray tube housing
Glass envelope
Oil

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31
Q

What are the added low energy photon filters

A

Sheets of aluminum

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32
Q

What size aluminum filter is required for 50-70 kVp?

A

1.5 mm aluminum equivalent

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33
Q

What size aluminum filter is required for kVp above 70?

A

2.5mm aluminum equivalent

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34
Q

What is the collimator?

A

Lead plate with a hole that fits over the opening of the metal housing

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35
Q

What is the function of the PID?

A

Aims and shaped x-ray beam

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35
Q

What is the function of the collimator?

A

Restricts size of X-ray beam

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36
Q

What is the function of the step-down transformer?

A

Reduce voltage from 110-220 volts to 3-5 volts

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37
Q

All dental equipment is usually collimated to what diameter at the patient’s face?

A

2.75 inches, or 7cm

38
Q

What is the function of the step-up transformer?

A

Increase voltage from 65,000 volts to 100,000 volts

39
Q

What is autotransformer?

A

Voltage compensator that corrects minor fluctuations

40
Q

What is the tube current?

A

Flow of electrons through the tube, from cathode to anode

41
Q

What is the tube current controlled by?

A

mA

42
Q

What is the function of the timer in the power supply?

A

Built to control the duration of x-ray exposure

43
Q

What is tube voltage controlled by?

A

kVp

44
Q

High tube voltage is required between what structures to generate X-rays?

A

Cathode and anode

45
Q

What are the four steps that occur when the X-ray unit is turned on?

A
  • Electricity is at 110 volts to 220 volts
  • Step down transformer reduces it to 4 to 5 volts
  • Heats the filament circuit, uses 3 to 5 volts
  • Thermionic emission
46
Q

What is thermionic emission?

A

Release of electrons from the outer shell of the tungsten filament

47
Q

What are the three steps that occur when the exposure is activated?

A
  • Step up transformer generates high voltage
  • Electrons are produce at cathode, go to anode
  • Reach the focal spot and the energy of the electrons is converted to x-ray photons
48
Q

What happens to the heat produced during X-ray production?

A

Carried away by the copper stem and absorbed by the insulating oil

48
Q

What two types of interactions occur when high energy electrons interact with the tungsten target?

A
  • Breaking radiation
  • Characteristic radiation
49
Q

What type of interaction produces the most X-rays when high energy photons hit the tungsten target? How much?

A

Bremsstrahlung/breaking radiation, 70%

50
Q

What happens during a direct hit interaction in breaking radiation?

A

Electron hits the nucleus and stops

51
Q

What happens during a near miss interaction in breaking radiation?

A

Electron passes close to the nucleus

52
Q

In both cases of breaking radiation, what is the energy of the electron converted into?

A

X ray photon

53
Q

What type of interaction produces the least amount of X-rays when high energy photons hit the tungsten target? How much?

A

Characteristic radiation, 10-28%

54
Q

What happens in characteristic radiation?

A

Incident electron ejects K shell electron, produces rebound electron, vacancy in K shell is filled by outer electron

55
Q

What percentage of compton scattering interacts with the patient?

A

57%

56
Q

What percentage of photoelectric absoportion interacts with the patient?

A

27%

57
Q

What percentage of coherent scattering interacts with the patient?

A

7%

58
Q

What percentage no interaction of radiation with patient occurs?

A

9%

59
Q

In photoelectric interaction, the difference in energy between both shells is released as characteristic radiation, BUT…

A

Due to low energy, photons are absorbed into patient

60
Q

Photoelectric interaction is needed to produce…

A

High contrast images in dental radiography

61
Q

What is compton scattering?

A

X ray collides with outer shell electrons and ejects electrons from orbit, incident photon is scatter in a different direction with low energy

62
Q

What is coherent scattering?

A

Interaction of low energy photons with whole atom, emits secondary x-ray photon that goes in different direction

63
Q

Does coherent scattering contribute to diagnostic imaging?

A

No

64
Q

What is X-ray beam quality?

A

Penetrating ability of X-ray beam

65
Q

What is produced by shorter wavelength X-rays?

A

More energy, more penetration

66
Q

What is produced by longer wavelength X-rays?

A

Low energy, less penetration

67
Q

What controls quality and wavelength of X-ray beam

A

Tube voltage

68
Q

Tube voltage makes electrons move from…

A

Cathode to anode

69
Q

If you increase the kVp, what happens?

A

Increase speed of electrons
Electrons strike target with greater force
Shorter wavelength

70
Q

1 kV equals how many volts?

A

1000 volts

71
Q

Dental radiography ranges in how many kilo-volts?

A

60 to 100 kV

72
Q

What range of kilo-volts does not allow for adequate penetration?

A

65-75 kV

72
Q

What range of kilo-volts is over penetration?

A

80 to 100 kV

73
Q

If the X-ray unit was operating at 70 kVp, the tube will generate X-ray photons with energies ranging from maximum to…

A

70 keV

74
Q

What is the X-ray beam quantity?

A

Number of x-rays produced in a dental x-ray unit

75
Q

What does amperage determine?

A

Amount of electrons passing through the cathode filament

76
Q

What does ampere measure?

A

Number of electrons or current flowing through the cathode filament

77
Q

X-ray beam quantity relates to the…

A

Tube current

78
Q

1 mA equals how many amperes?

A

1000

79
Q

Does a change in mA equal a change in energy of electrons?

A

No

80
Q

In dental radiography, how many mA is required?

A

7 to 15 mA

81
Q

Exposure time determines…

A

Quantity

82
Q

Milliamperes times exposure time equals…

A

mA

83
Q

In order for the density to remain the same, if milliamperage is increased what must happen to the exposure time?

A

Exposure time must decrease

84
Q

What is x-ray beam intensity?

A

Product of quality and quantity per unit area per time of exposure

85
Q

How does higher kVp, mA, and exposure time affect the beam intensity?

A

Increases beam intensity

86
Q

As x-rays travel from the source, their intensity…

A

Decreases

87
Q

What does the inverse square law explain?

A

Relationship between distance and intensity

88
Q

What does the inverse square law state?

A

Intensity of radiation is inverse proportional to the square distance from the source of radiation

89
Q

The thickness of filters to reduce intensity by half is called what?

A

Half value layer

90
Q

What factors impact exposure time?

A

Seconds
Impulses

91
Q

What factor impact tube current?

A

mA

92
Q

What factor impact tube voltage?

A

kVp

93
Q

What impacts the quantity of X-rays produced?

A

Exposure time
Tube current

94
Q

What impacts the quality of X-rays produced?

A

Tube voltage

95
Q

Does kVp or mA impact quantity?

A

mAs

96
Q

Does kVp or mA impact quality?

A

kVp

radiology (5 decks)

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