WRONG FOLDER - ORPT - Radiation Physics and X-Ray Machine Flashcards
(132 cards)
1
Q
Matter
A
Anything that has mass and occupies space
2
Q
Nucleus
A
Nucleons, protons and neutrons
3
Q
Mass number
A
Number of protons and neutrons
4
Q
Atomic number
A
Number of protons
5
Q
Molecule
A
Two or more atoms joined by a chemical bond
Form by the transfer of electrons
6
Q
Letters of orbital shells
A
K - Q
7
Q
Farthest orbital shell is…
A
Q
8
Q
Closest orbital shell is…
A
K
9
Q
How are electrons held in orbits?
A
Electrons are negative, electrostatic attraction between the positive nucleus
10
Q
What shell has the highest binding energy (BE)?
A
K
11
Q
Binding energy is dependent on…
A
Distance from nucleus
12
Q
What units of measure are used for binding energy (BE)?
A
Electron volts or kilo electron volts
13
Q
Ionization
A
Removal of an electron from an atom
14
Q
How does ionization work?
A
Energy required to remove the electron must exceed the BE of the electron
15
Q
Ion pair
A
Positive ion and ejected electron
16
Q
Radiation
A
Emission and travel of energy through space
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
18
Q
Beta particles
A
Nucleus of radioactive atoms
19
Q
Cathode rays
A
High speed electrons originated in an x-ray tube
20
Q
Electromagnetic radiation
A
- Does not have mass or weight
- Travel at the speed of light
- No electrical charge
21
Q
Examples of electromagnetic radiation
A
Visible light, x-rays, y-rays, UV, IR radiation/heat, microwaves, and radiowaves
22
Q
How does electromagnetic radiation work?
A
Movement of wave-like energy as a combination of electric and magnetic fields
23
Q
Non-ionizing radiation
A
Radiowaves, microwaves, infrared, visible light
24
Q
Ionizing radiation
A
UV, x-rays, gamma rays
25
Radioactivity
- 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
26
Is radioactivity used in dentistry?
No
27
Electromagnetic radiation properties
- Does not have mass or weight
- No electrical charge
- Travel at the speed of light
28
What is a cathode made up of?
Made of coiled Tungsten wire filament
29
What is the source of electrons?
Cathode
30
What is the purpose of the focusing cup?
- Electrostatically focuses them in a straight path
- Electrons are then accelerated towards a positive anode
31
What is the charge of the cathode?
Negative
32
What is the focusing cup made up of?
Molybdenum
33
What happens when the cathode is heated?
The electron is produced at the cathode
34
What is the charge of an anode?
Positive
35
What is the source of x-rays
Anode
36
What is the anode made of?
Small tungsten target
37
What are the two types of anodes?
- Stationary
- Rotating: Not used in dental units
38
Where is the focal spot located?
- Anode
- 2-3mm thick
39
What is the focal spot made of?
- Copper
40
What conducts heat better?
Copper
41
Mental housing contains...
- Transformers
- Filled with insulating oil
42
Function of metal housing
- Protection of X-ray tube
- Grounds the high-voltage components
43
Transformer purpose
Alter the voltage
44
Insulating oil purposes
- Surrounding tube and transformers
- Prevents overheating by absorbing heat
45
Tube head seal purpose
Lead/aluminum covering of tube head that permits exit of x-rays
46
Aluminum disks purpose
- Acts as filter
- Absorbs low energy x-rays, reduces amount of radiation a person gets
47
Low energy photon receptors can't...
Can not reach image receptors, end up cause unnecessary exposure to the patient
48
Higher energy photons can...
Penetrate through anatomic structures and reach image receptors or sensors
49
How are low energy photons removed?
Filter (small metallic disk)
50
Inherent filters on an X-ray machine
- Tube housing
- Glass envelope
- Oil
51
Required total filtration for 50-70 kVp
1.5mm Aluminum equivalent
52
Required total filtration for above 70kVp
2.5 mm Aluminum equivalent
53
Collimator
- Lead plate with a hole that fits directly over the opening of metal housing
- Restricts the size of X-ray beam, shapes it
54
Position indicating device (PID)
- Lead lined cylinder that extends from the metal housing of tube head
- Aims and shape the X-ray beam
55
Collimators purpose is to...
Regulate the shape and size of the beam
56
What size collimator is used in dental equipment?
2.75 inches or 7cm in diameter
57
What shape collimation reduces patient exposure?
Rectangle
58
Step down transformer
Reduce voltage of incoming line current 110-220V to 3-5 volts, filament circuit
59
Step up transformer
Increases the voltage to 65,000 to 100,000 voltage
60
Autotransformer
Voltage compensator that corrects minor fluctuations
61
Tube voltage
- High voltage is required between cathode and anode to generated X-rays
- Controlled by kVp
62
Tube current
- It is a flow of electrons through the tube
- From cathode to anode
- Controlled by mA
63
Timer
Built to control the duration of x-ray exposure
64
What happens when you turn the X-ray unit on?
- 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
Thermionic emission
Release of electrons from the outer shell of tungsten filament
66
What happens when you activate the exposure?
- 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
Where does the heat go that is produced during the X-ray?
- Carried away from the copper stem
- Absorbed by insulating oil
68
Where are X-rays carried to?
travel through tube head seal, disks/filters, collimator, PID, then unleaded glass window
69
Bremsstrahlung or Breaking Radiation, direct hit interaction
Electron hits the nucleus and stops
70
Bremsstrahlung or Breaking Radiation, indirect interaction
Electron passes close to the nucleus
71
What happens in Breaking radiation?
K.E of electron is converted to X-ray photon
72
What interaction produces the most x-rays?
Breaking radiation, 70%
73
Characteristic radiation
- Incident electron with energy higher than BE of K-shell electron
- Ejects the K-shell electron
- Electron is replaced
74
In characteristic radiation, what fills the vacancy?
Outer shell electron
75
In characteristic radiation, the difference in energy between both shells is released as what?
X-ray photon
76
What percentage of x-rays are produced by characteristic radiation?
10-28%
77
No interaction of radiation with patient
9%
78
Absorption of photoelectric effect with patient
27%
79
Compton scatter with patient
57%
80
Coherent scatter with patient
7%
81
Incident photon
- Interacts with inner shell electrons of an atom in pt’s tissues,
- Gives off all energy and ceases to exist
82
If the energy is greater than the binding energy, the electron does what?
Absorbs energy and ejects as a photoelectron
83
During photoelectric interactions, where is there a vacancy? What fills it?
- K shell
- Outer shell electrons
84
In photoelectric interactions, the different in energy between both shells is released as...
- Characteristic radiation
- Is absorbed by patient because of low energy
85
Patient tissue atom accounts for...
28-30% of interactions
86
Compton Scattering
- X-ray photon collides with outer shell electrons and ejects election from orbit
- Incident photon is scattered into different direction with lower energy
87
When does compton scattering occur?
When an x-ray photon interacts with the outer orbital shell electrons
88
Compton scatter accounts for...
57% of interactions
89
In compton scattering, the incident photon collides with...
- 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
Coherent scatter
Interaction of low energy x-ray photons (<10keV) with whole atom/outer shell electron
91
Coherent scatter causes...
Causes the atom to become excited for a moment at the same time frequency of the x-ray photon
92
In coherent scattering, what happens once the excited atom returns to it's ground state?
- 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
Coherent scattering accounts for...
7-8% of total x-ray interaction
94
What happens in coherent scattering?
Not enough energy to remove electron, vibrates whole atom, and goes into an excited state
95
Control panels
Predetermined setting for kVp, mA according to anatomic region of the mouth
96
X-ray beam quality
Mean energy or penetrating ability of x-ray beam
97
Shorter wavelength x-rays have...
- More energy
- More penetration
98
Longer wavelength x-rays have...
- Lower energy
- Less penetrating capability
99
Tube voltage controls...
Quality, wavelength, and energy
100
Tube voltage
Potential difference between cathode and anode that gives K.E. to electrons and make electrons move from cathode to anode
101
102
Can kVp be adjusted accordingly to individual patient needs?
Yes
103
Dental radiography kV are between
65-100kV
104
1kV equals how many V?
1000
105
Overpenetration is...
- 85-100kV
- Shorter wavelength, more energy
106
How many kV does not allow for adequate penetration
- 65 to 75 kV
- Longer wavelength, less energy
107
Higher kVp is used in areas where...
That are dense or thick
108
If the X-ray unit is operating at 70 kVp, x-ray photons with what energy ranges will be produced?
Max to 70keV
109
X-ray beam quantity
Number of x-rays produced in dental x-ray unit
110
Amperage determines...
Amount of electrons passing through the cathode filament
111
Ampere
Unit used to measure no of electrons or current flowing through the cathode filament
112
1mA equals how many amperes?
1000 amperes
113
1 milli ampere equals how many ampere?
1/1000
114
Does a change in mA equal a change in the K.E of electrons?
No
115
In dental radiography, how many mA is required?
7 to 15 mA
116
Exposure time
Time that x-rays are produced
117
Are x-rays produced in burst/pulses or a continuous stream?
Burst/pulses
118
The exposure time determines...
Quality
119
Milliamperes times exposure time equals...
mA
120
Inside x-ray tube voltage determines...
The speed with which electrons move
121
When milliamperage is increased the exposure time must what for the density to remain the same?
Decrease
122
When milliamperage is decreased the exposure time must do what for the density to remain the same?
Increase
123
X-ray beam intensity
Product of quality (energy of each photon), quantity (no of x ray photons), per unit area per unit time of exposure
124
Increase in intensity of x-ray beam means...
Higher kvP and exposure time
125
Distance between source of radiation and the film has an effect on the...
Intensity
126
What distances are considered?
- Source, teeth, and image receptor
127
As x-rays travel from the source their intensity...
Decreases
128
Inverse square law
Intensity of radiation is inversely proportional to the square distance from source of radiation
129
Aluminum filters remove...
Low energy
130
Half value layer
The thickness of the material which reduce intensity by half
131
What factors control mA and quantity of x-rays produced?
- Exposure time (seconds, time)
- Tube current (mA)
132
What factors control kVp and quality of x-rays produced
Tube voltage (kVp)
