Radiation Physics and X-ray Machine Flashcards
1
Q
What is radiation?
A
The emission and propagation of energy through space.
2
Q
What are the two types of radiation?
A
Particulate and electromagnetic radiation.
3
Q
What type of radiation is electrons, alpha particles, protons, and neutrons?
A
Particulate radiation
3
Q
What type of radiation are X-rays?
A
Electromagnetic radiation
4
Q
What type of radiation is visible light?
A
Electromagnetic radiation
5
Q
What are the three properties of electromagnetic radiation?
A
Does not have mass
Travel at the speed of light
No electrical charge
6
Q
What are the two properties of particulate radiation?
A
Has mass
Travel in straight lines at high speed
7
Q
What type of radiation is a cathode ray?
A
Particulate radiation, high speed electrons originate at x-ray tube
7
Q
What are the four types of non-ionizing radiation?
A
Radio waves
Microwaves
Infrared
Visible light
8
Q
What are the three ionizing forms of radiation?
A
Ultraviolet
X-rays
Gamma rays
9
Q
What is radioactivity?
A
Process of unstable atoms undergo spontaneous disintegration or decay to try to be in a more balanced state
9
Q
What is the filament in the cathode tube made of?
A
Tungsten
9
Q
What does the filament sit in the cathode?
A
Focusing cup
10
Q
What charge is a cathode?
A
Negative
11
Q
Where are electrons produced?
A
Cathode
12
Q
What is the function of the focusing cup?
A
Directs electrons in a narrow beam to the anode
13
Q
What type of anode is used in dentistry?
A
Stationary
14
Q
What charge is the anode? Why?
A
Positive to attract electrons
15
Q
What is the focal spot of the anode made up of?
A
Tungsten
16
Q
What is the stem made up of in the anode?
A
Copper
17
Q
Is copper or tungsten a better heat conductor?
A
Copper
18
Q
What surrounds the tube and transformers?
A
Insulating oil
19
Q
What is the function of the insulating oil?
A
Prevent overheating by absorbing heat
20
Q
Where is the transformers?
A
In the metal housing
21
What is the metal housing filled with?
Insulating oil
22
What is the function of the metal housing?
Protection of X-ray tube and grounds high voltage components
23
What is the function of the transformers?
Alters the voltage
24
What is the function of the tube head seal?
Permits the exit of x-rays
25
What is the tube head seal made of?
Lead and aluminum
26
What is the function of the aluminum disk?
Filter
27
What type of photons can penetrate through anatomic structures and each image receptors?
High energy photons
28
What do low energy photons cause?
Unnecessary exposure to the patient
29
How are low energy photons removed?
By adding filters
30
What are the inherent low energy photon filters?
X ray tube housing
Glass envelope
Oil
31
What are the added low energy photon filters
Sheets of aluminum
32
What size aluminum filter is required for 50-70 kVp?
1.5 mm aluminum equivalent
33
What size aluminum filter is required for kVp above 70?
2.5mm aluminum equivalent
34
What is the collimator?
Lead plate with a hole that fits over the opening of the metal housing
35
What is the function of the PID?
Aims and shaped x-ray beam
35
What is the function of the collimator?
Restricts size of X-ray beam
36
What is the function of the step-down transformer?
Reduce voltage from 110-220 volts to 3-5 volts
37
All dental equipment is usually collimated to what diameter at the patient’s face?
2.75 inches, or 7cm
38
What is the function of the step-up transformer?
Increase voltage from 65,000 volts to 100,000 volts
39
What is autotransformer?
Voltage compensator that corrects minor fluctuations
40
What is the tube current?
Flow of electrons through the tube, from cathode to anode
41
What is the tube current controlled by?
mA
42
What is the function of the timer in the power supply?
Built to control the duration of x-ray exposure
43
What is tube voltage controlled by?
kVp
44
High tube voltage is required between what structures to generate X-rays?
Cathode and anode
45
What are the four steps that occur when the X-ray unit is turned on?
- 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
What is thermionic emission?
Release of electrons from the outer shell of the tungsten filament
47
What are the three steps that occur when the exposure is activated?
- 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
What happens to the heat produced during X-ray production?
Carried away by the copper stem and absorbed by the insulating oil
48
What two types of interactions occur when high energy electrons interact with the tungsten target?
- Breaking radiation
- Characteristic radiation
49
What type of interaction produces the most X-rays when high energy photons hit the tungsten target? How much?
Bremsstrahlung/breaking radiation, 70%
50
What happens during a direct hit interaction in breaking radiation?
Electron hits the nucleus and stops
51
What happens during a near miss interaction in breaking radiation?
Electron passes close to the nucleus
52
In both cases of breaking radiation, what is the energy of the electron converted into?
X ray photon
53
What type of interaction produces the least amount of X-rays when high energy photons hit the tungsten target? How much?
Characteristic radiation, 10-28%
54
What happens in characteristic radiation?
Incident electron ejects K shell electron, produces rebound electron, vacancy in K shell is filled by outer electron
55
What percentage of compton scattering interacts with the patient?
57%
56
What percentage of photoelectric absoportion interacts with the patient?
27%
57
What percentage of coherent scattering interacts with the patient?
7%
58
What percentage no interaction of radiation with patient occurs?
9%
59
In photoelectric interaction, the difference in energy between both shells is released as characteristic radiation, BUT…
Due to low energy, photons are absorbed into patient
60
Photoelectric interaction is needed to produce…
High contrast images in dental radiography
61
What is compton scattering?
X ray collides with outer shell electrons and ejects electrons from orbit, incident photon is scatter in a different direction with low energy
62
What is coherent scattering?
Interaction of low energy photons with whole atom, emits secondary x-ray photon that goes in different direction
63
Does coherent scattering contribute to diagnostic imaging?
No
64
What is X-ray beam quality?
Penetrating ability of X-ray beam
65
What is produced by shorter wavelength X-rays?
More energy, more penetration
66
What is produced by longer wavelength X-rays?
Low energy, less penetration
67
What controls quality and wavelength of X-ray beam
Tube voltage
68
Tube voltage makes electrons move from…
Cathode to anode
69
If you increase the kVp, what happens?
Increase speed of electrons
Electrons strike target with greater force
Shorter wavelength
70
1 kV equals how many volts?
1000 volts
71
Dental radiography ranges in how many kilo-volts?
60 to 100 kV
72
What range of kilo-volts does not allow for adequate penetration?
65-75 kV
72
What range of kilo-volts is over penetration?
80 to 100 kV
73
If the X-ray unit was operating at 70 kVp, the tube will generate X-ray photons with energies ranging from maximum to…
70 keV
74
What is the X-ray beam quantity?
Number of x-rays produced in a dental x-ray unit
75
What does amperage determine?
Amount of electrons passing through the cathode filament
76
What does ampere measure?
Number of electrons or current flowing through the cathode filament
77
X-ray beam quantity relates to the…
Tube current
78
1 mA equals how many amperes?
1000
79
Does a change in mA equal a change in energy of electrons?
No
80
In dental radiography, how many mA is required?
7 to 15 mA
81
Exposure time determines…
Quantity
82
Milliamperes times exposure time equals…
mA
83
In order for the density to remain the same, if milliamperage is increased what must happen to the exposure time?
Exposure time must decrease
84
What is x-ray beam intensity?
Product of quality and quantity per unit area per time of exposure
85
How does higher kVp, mA, and exposure time affect the beam intensity?
Increases beam intensity
86
As x-rays travel from the source, their intensity…
Decreases
87
What does the inverse square law explain?
Relationship between distance and intensity
88
What does the inverse square law state?
Intensity of radiation is inverse proportional to the square distance from the source of radiation
89
The thickness of filters to reduce intensity by half is called what?
Half value layer
90
What factors impact exposure time?
Seconds
Impulses
91
What factor impact tube current?
mA
92
What factor impact tube voltage?
kVp
93
What impacts the quantity of X-rays produced?
Exposure time
Tube current
94
What impacts the quality of X-rays produced?
Tube voltage
95
Does kVp or mA impact quantity?
mAs
96
Does kVp or mA impact quality?
kVp
