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GENP 311 > WRONG FOLDER - ORPT - Radiation Physics and X-Ray Machine > Flashcards

WRONG FOLDER - ORPT - Radiation Physics and X-Ray Machine Flashcards

1
Q

Matter

A

Anything that has mass and occupies space

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2
Q

Nucleus

A

Nucleons, protons and neutrons

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3
Q

Mass number

A

Number of protons and neutrons

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4
Q

Atomic number

A

Number of protons

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5
Q

Molecule

A

Two or more atoms joined by a chemical bond
Form by the transfer of electrons

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6
Q

Letters of orbital shells

A

K - Q

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7
Q

Farthest orbital shell is…

A

Q

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8
Q

Closest orbital shell is…

A

K

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9
Q

How are electrons held in orbits?

A

Electrons are negative, electrostatic attraction between the positive nucleus

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10
Q

What shell has the highest binding energy (BE)?

A

K

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11
Q

Binding energy is dependent on…

A

Distance from nucleus

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12
Q

What units of measure are used for binding energy (BE)?

A

Electron volts or kilo electron volts

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13
Q

Ionization

A

Removal of an electron from an atom

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14
Q

How does ionization work?

A

Energy required to remove the electron must exceed the BE of the electron

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15
Q

Ion pair

A

Positive ion and ejected electron

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16
Q

Radiation

A

Emission and travel of energy through space

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17
Q

Particulate radiation

A
  • Electrons (beta particles, cathode rays), protons, neutrons, alpha particles
  • Tiny particles of matter that has mass
  • Travel in straight lines at high speed
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18
Q

Beta particles

A

Nucleus of radioactive atoms

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19
Q

Cathode rays

A

High speed electrons originated in an x-ray tube

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20
Q

Electromagnetic radiation

A
  • Does not have mass or weight
  • Travel at the speed of light
  • No electrical charge
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21
Q

Examples of electromagnetic radiation

A

Visible light, x-rays, y-rays, UV, IR radiation/heat, microwaves, and radiowaves

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22
Q

How does electromagnetic radiation work?

A

Movement of wave-like energy as a combination of electric and magnetic fields

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23
Q

Non-ionizing radiation

A

Radiowaves, microwaves, infrared, visible light

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24
Q

Ionizing radiation

A

UV, x-rays, gamma rays

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25
Q

Radioactivity

A
  • Process by which certain unstable atoms or elements undergo spontaneous disintegration to decay in an effort to station a more balanced nuclear state
  • Throwing particles out to try to make itself more stable
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26
Q

Is radioactivity used in dentistry?

A

No

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27
Q

Electromagnetic radiation properties

A
  • Does not have mass or weight
  • No electrical charge
  • Travel at the speed of light
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28
Q

What is a cathode made up of?

A

Made of coiled Tungsten wire filament

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29
Q

What is the source of electrons?

A

Cathode

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30
Q

What is the purpose of the focusing cup?

A
  • Electrostatically focuses them in a straight path
  • Electrons are then accelerated towards a positive anode
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31
Q

What is the charge of the cathode?

A

Negative

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32
Q

What is the focusing cup made up of?

A

Molybdenum

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33
Q

What happens when the cathode is heated?

A

The electron is produced at the cathode

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34
Q

What is the charge of an anode?

A

Positive

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35
Q

What is the source of x-rays

A

Anode

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36
Q

What is the anode made of?

A

Small tungsten target

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37
Q

What are the two types of anodes?

A
  • Stationary
  • Rotating: Not used in dental units
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38
Q

Where is the focal spot located?

A
  • Anode
  • 2-3mm thick
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39
Q

What is the focal spot made of?

A
  • Copper
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40
Q

What conducts heat better?

A

Copper

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41
Q

Mental housing contains…

A
  • Transformers
  • Filled with insulating oil
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42
Q

Function of metal housing

A
  • Protection of X-ray tube
  • Grounds the high-voltage components
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43
Q

Transformer purpose

A

Alter the voltage

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44
Q

Insulating oil purposes

A
  • Surrounding tube and transformers
  • Prevents overheating by absorbing heat
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45
Q

Tube head seal purpose

A

Lead/aluminum covering of tube head that permits exit of x-rays

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46
Q

Aluminum disks purpose

A
  • Acts as filter
  • Absorbs low energy x-rays, reduces amount of radiation a person gets
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47
Q

Low energy photon receptors can’t…

A

Can not reach image receptors, end up cause unnecessary exposure to the patient

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48
Q

Higher energy photons can…

A

Penetrate through anatomic structures and reach image receptors or sensors

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49
Q

How are low energy photons removed?

A

Filter (small metallic disk)

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50
Q

Inherent filters on an X-ray machine

A
  • Tube housing
  • Glass envelope
  • Oil
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51
Q

Required total filtration for 50-70 kVp

A

1.5mm Aluminum equivalent

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52
Q

Required total filtration for above 70kVp

A

2.5 mm Aluminum equivalent

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53
Q

Collimator

A
  • Lead plate with a hole that fits directly over the opening of metal housing
  • Restricts the size of X-ray beam, shapes it
54
Q

Position indicating device (PID)

A
  • Lead lined cylinder that extends from the metal housing of tube head
  • Aims and shape the X-ray beam
55
Q

Collimators purpose is to…

A

Regulate the shape and size of the beam

56
Q

What size collimator is used in dental equipment?

A

2.75 inches or 7cm in diameter

57
Q

What shape collimation reduces patient exposure?

A

Rectangle

58
Q

Step down transformer

A

Reduce voltage of incoming line current 110-220V to 3-5 volts, filament circuit

59
Q

Step up transformer

A

Increases the voltage to 65,000 to 100,000 voltage

60
Q

Autotransformer

A

Voltage compensator that corrects minor fluctuations

61
Q

Tube voltage

A
  • High voltage is required between cathode and anode to generated X-rays
  • Controlled by kVp
62
Q

Tube current

A
  • It is a flow of electrons through the tube
  • From cathode to anode
  • Controlled by mA
63
Q

Timer

A

Built to control the duration of x-ray exposure

64
Q

What happens when you turn the X-ray unit on?

A
  • Electricity is 110-220 V
  • Step down transformer reduces it to 4-5 V
  • Heats the filament circuits, uses 3-5 V
  • Thermionic emission
65
Q

Thermionic emission

A

Release of electrons from the outer shell of tungsten filament

66
Q

What happens when you activate the exposure?

A
  • Step up transformer generates high voltage
  • Electrons produced at cathode are accelerated towards anode. The focusing cup directs the electrons
  • When they bombard the focal spot of the tungsten target, the K.E of electrons is converted into x-ray photons
  • Ineffective!!!
67
Q

Where does the heat go that is produced during the X-ray?

A
  • Carried away from the copper stem
  • Absorbed by insulating oil
68
Q

Where are X-rays carried to?

A

travel through tube head seal, disks/filters, collimator, PID, then unleaded glass window

69
Q

Bremsstrahlung or Breaking Radiation, direct hit interaction

A

Electron hits the nucleus and stops

70
Q

Bremsstrahlung or Breaking Radiation, indirect interaction

A

Electron passes close to the nucleus

71
Q

What happens in Breaking radiation?

A

K.E of electron is converted to X-ray photon

72
Q

What interaction produces the most x-rays?

A

Breaking radiation, 70%

73
Q

Characteristic radiation

A
  • Incident electron with energy higher than BE of K-shell electron
  • Ejects the K-shell electron
  • Electron is replaced
74
Q

In characteristic radiation, what fills the vacancy?

A

Outer shell electron

75
Q

In characteristic radiation, the difference in energy between both shells is released as what?

A

X-ray photon

76
Q

What percentage of x-rays are produced by characteristic radiation?

A

10-28%

77
Q

No interaction of radiation with patient

A

9%

78
Q

Absorption of photoelectric effect with patient

A

27%

79
Q

Compton scatter with patient

A

57%

80
Q

Coherent scatter with patient

A

7%

81
Q

Incident photon

A
  • Interacts with inner shell electrons of an atom in pt’s tissues,
  • Gives off all energy and ceases to exist
82
Q

If the energy is greater than the binding energy, the electron does what?

A

Absorbs energy and ejects as a photoelectron

83
Q

During photoelectric interactions, where is there a vacancy? What fills it?

A
  • K shell
  • Outer shell electrons
84
Q

In photoelectric interactions, the different in energy between both shells is released as…

A
  • Characteristic radiation
  • Is absorbed by patient because of low energy
85
Q

Patient tissue atom accounts for…

A

28-30% of interactions

86
Q

Compton Scattering

A
  • X-ray photon collides with outer shell electrons and ejects election from orbit
  • Incident photon is scattered into different direction with lower energy
87
Q

When does compton scattering occur?

A

When an x-ray photon interacts with the outer orbital shell electrons

88
Q

Compton scatter accounts for…

A

57% of interactions

89
Q

In compton scattering, the incident photon collides with…

A
  • The outer orbital electron of the patient’s tissue atom and is deflected from its path
  • Scattered to a new direction as a scattered photon
90
Q

Coherent scatter

A

Interaction of low energy x-ray photons (<10keV) with whole atom/outer shell electron

91
Q

Coherent scatter causes…

A

Causes the atom to become excited for a moment at the same time frequency of the x-ray photon

92
Q

In coherent scattering, what happens once the excited atom returns to it’s ground state?

A
  • It emits a secondary x-ray photon with similar energy as the incident photon
  • Secondary photon has a different direction than the incident photon
93
Q

Coherent scattering accounts for…

A

7-8% of total x-ray interaction

94
Q

What happens in coherent scattering?

A

Not enough energy to remove electron, vibrates whole atom, and goes into an excited state

95
Q

Control panels

A

Predetermined setting for kVp, mA according to anatomic region of the mouth

96
Q

X-ray beam quality

A

Mean energy or penetrating ability of x-ray beam

97
Q

Shorter wavelength x-rays have…

A
  • More energy
  • More penetration
98
Q

Longer wavelength x-rays have…

A
  • Lower energy
  • Less penetrating capability
99
Q

Tube voltage controls…

A

Quality, wavelength, and energy

100
Q

Tube voltage

A

Potential difference between cathode and anode that gives K.E. to electrons and make electrons move from cathode to anode

101
Q
A
102
Q

Can kVp be adjusted accordingly to individual patient needs?

A

Yes

103
Q

Dental radiography kV are between

A

65-100kV

104
Q

1kV equals how many V?

A

1000

105
Q

Overpenetration is…

A
  • 85-100kV
  • Shorter wavelength, more energy
106
Q

How many kV does not allow for adequate penetration

A
  • 65 to 75 kV
  • Longer wavelength, less energy
107
Q

Higher kVp is used in areas where…

A

That are dense or thick

108
Q

If the X-ray unit is operating at 70 kVp, x-ray photons with what energy ranges will be produced?

A

Max to 70keV

109
Q

X-ray beam quantity

A

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

110
Q

Amperage determines…

A

Amount of electrons passing through the cathode filament

111
Q

Ampere

A

Unit used to measure no of electrons or current flowing through the cathode filament

112
Q

1mA equals how many amperes?

A

1000 amperes

113
Q

1 milli ampere equals how many ampere?

A

1/1000

114
Q

Does a change in mA equal a change in the K.E of electrons?

A

No

115
Q

In dental radiography, how many mA is required?

A

7 to 15 mA

116
Q

Exposure time

A

Time that x-rays are produced

117
Q

Are x-rays produced in burst/pulses or a continuous stream?

A

Burst/pulses

118
Q

The exposure time determines…

A

Quality

119
Q

Milliamperes times exposure time equals…

A

mA

120
Q

Inside x-ray tube voltage determines…

A

The speed with which electrons move

121
Q

When milliamperage is increased the exposure time must what for the density to remain the same?

A

Decrease

122
Q

When milliamperage is decreased the exposure time must do what for the density to remain the same?

A

Increase

123
Q

X-ray beam intensity

A

Product of quality (energy of each photon), quantity (no of x ray photons), per unit area per unit time of exposure

124
Q

Increase in intensity of x-ray beam means…

A

Higher kvP and exposure time

125
Q

Distance between source of radiation and the film has an effect on the…

A

Intensity

126
Q

What distances are considered?

A
  • Source, teeth, and image receptor
127
Q

As x-rays travel from the source their intensity…

A

Decreases

128
Q

Inverse square law

A

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

129
Q

Aluminum filters remove…

A

Low energy

130
Q

Half value layer

A

The thickness of the material which reduce intensity by half

131
Q

What factors control mA and quantity of x-rays produced?

A
  • Exposure time (seconds, time)
  • Tube current (mA)
132
Q

What factors control kVp and quality of x-rays produced

A

Tube voltage (kVp)

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