Review Exam 1 Flashcards
(173 cards)
1
Q
Mode of decay when high n/p+ ratio
A
B-
2
Q
Mode of decay when too many neutrons
A
B-
3
Q
Mode of decay when too many p+
A
Beta +/Positron emission
4
Q
Most likely mode of decay for heavier elements
A
Alpha
5
Q
Mode of decay for PET
A
Positron Emission
6
Q
Mode of decay that can result in characteristic or Auger e-
A
Electron capture
7
Q
Isotope
A
same # of p+, diff # neutrons
8
Q
Isotone
A
Same # of neutrons, diff # p+
9
Q
Isobar
A
Same # nucleons (both), diff p+
10
Q
Formula for # of e- in a shell
A
2n^2
11
Q
speed of light
A
3 x 10^8
12
Q
The penetrability of the beam is the definition of?
Expressed by what 2 concepts?
A
Beam quality.
HVL or kVp
13
Q
The # of photons
A
Quantity
14
Q
Space charge effect
A
Space-charge effect creates a cloud of electrons caused by the electrons repelling each other, rather than the free flow of electrons. Can cause reduced beam output.
15
Q
Positive side of x-ray tube
A
anode
16
Q
negative side of x-ray tube
A
Cathode
17
Q
What does cathode do?
A
Has tungsten filament that emits e- when heated (thermionic emission occurs here)
18
Q
What does anode do?
A
Contains tungsten target; electrons hit target to produce x-rays.
19
Q
Contains tungsten target; electrons hit target to produce x-rays.
A
Anode
20
Q
Has tungsten filament that emits e- when heated (thermionic emission occurs here)
A
Cathode
21
Q
3 reasons tungsten is chosen for the target?
A
- High Z (high production efficiency)
- High melting point
- Dissipates heat (prevents overheating)??
22
Q
Explain anode-heel effect
A
The heel attenuates more electrons, so intensity on the heel side is decreased. The greater the target angle, the greater the attenuation of the beam.
23
Q
Avg energy of ployenergetic beam is?
A
1/3 max photon energy
24
Q
Occurs when a particle (charged)
such as an electron, proton or alpha particle collides with matter to produce a charged particle.
A
Direct ionization
25
Occurs when an uncharged particle
or radiation such as a photon or neutron liberate a directly ionizing particle when they interact with matter.
Indirect ionization
26
Atoms of the target become ionized or excited
Direct action
27
Radiation interacts with other atoms to produce free radicals that then do the damage to critical targets.
Indirect action
28
Interaction dominant in tx range?
Compton
29
Interaction dominant in dx range?
Photoelectric
30
Probability of brems:
Z^2
31
Z of tungsten
74
32
Beam flatness is measured where?
10 cm depth in water, but only middle 80% of beam bc of penumbra.
33
Beam flatness is?
of photons
34
Beam flatness is quantity or quality?
Quantity
35
How does filtration affect the quality of the beam?
it hardens the beam
36
How does filtration affect the quantity of the beam?
Reduces it by 4x (to 1/4)
37
What does beam flatness look like deeper than 10 cm?
middle hump
38
What does beam flatness look like more shallow than 10 cm?
lateral horns
39
Linac Part: changes direction of horizontal beam to vertical
Bending Magnet
40
Linac Part: copper “pipe” held under high vacuum to remove air molecules, where e- are accelerated
Waveguide
41
Energy range for Grenz:
10-20kVp
42
Energy range for Contact therapy:
40-50kVp
43
Energy range for Superficial
50-150kVp
44
Energy range for orthovoltage
150-500kVp
45
Energy range for supervoltge
500kVp – 1MV
46
What is the input electron energy from the electron gun?
50 keV
47
Photon interaction most likely with High Z:
Coherent
48
Photoelectric Z and/or E:
Z^3/E^3
49
Pair production Z and/or E:
Z^2
49
Comp Z and/or E:
Ind of Z, depends on e-density
50
Coherent energy range:
<10KeV
51
Photelectric energy range:
60-90 KeV
52
Compton energy range:
25 KeV – 10 MeV
53
Pair production energy range:
>1.02 MeV
54
Pneumonic for photon interaction:
CoPhoComPair
55
Coherent - inner or outer shell e-?
outer
56
Photelectric - inner or outer shell e-?
inner
57
Compton - inner or outer shell e-?
outer
58
Pair Production - inner or outer shell e-?
inner
59
What happens to penumbra if you increase SSD?
it increases
60
Klystron vs magnetron:
Cheaper
Shorter lifespan
Magnetron
61
Klystron vs magnetron:
Higher energy
More stable
More expensive
Klystron
62
Klystron vs magnetron:
More common in high energy Linacs
Klystron
63
What linear accelerator component sets the dose rate?
Modulator
64
What components in the linear accelerator treatment head change between electron and photon mode? Photon mode
Target and flattening filter is in the carousel when it is in photon mode.
65
What components in the linear accelerator treatment head change between electron and photon mode? Electron mode
Target is removed and scattering foil is put in
66
Klystron vs magnetron - which one amplifies microwaves?
Klystron
67
Klystron vs magnetron - which one generates microwaves?
magnetron
68
What machine component injects pulsed electrons to waveguide?
Electron gun
69
Variation of dose in comparison to CAX dose at depth of 10cm is the definition for?
Flatness
70
The amount of time to deliver 1 cGy, with a 10x10 cm FS, to a specified depth (usually DMAX), at a distance of 100cm away is the definition of?
MU
71
The photon interacts with an atom and ejects on of the (inner) orbital electrons. The photon gives 100% of its energy to the ejected electron.
Photoelectric Effect
72
Auger and characteristic x-rays can occur with which photon interaction?
Photelectric
73
An incoming photon hits an outer orbital electron & not all energy is transferred. This results in an ejected electron and a weaker photon.
Compton
74
Annihilation reaction can happen after?
Pair production
75
An incoming photon interacts with the nucleus and gives up all of its energy in creating a positron and negatron.
Pair production
76
Modes of decay: Combination of two lighter nuclei
Nuclear Fusion
77
Modes of decay: Nucleus splits into two
Nuclear Fission
78
1 J/kg = ___ Rads = ___ Gy
100, 1
79
1 Gy = ___ cGy
100
80
1cGy = ___ rad = ___ Gy
1, 0.01
81
A photon passes near an electron and sets it into an oscillation. The oscillating e- then re-radiates the energy at the same frequency as
the incident photon.
Coherent scatter
82
83
84
MU: The amount of time to deliver ___, with a __ FS, to a specified depth (usually ___), at a distance of ___ away is the definition of?
1 cGy, 10x10 cm, DMAX, 100cm
85
What is meant by "good geometry"?
Put the detector where no scatter will be measured.
86
To measure beam flatness, all points must be within __?
3%
87
A voltage rectifier does what?
Prevents backflow (e- can only go in one direction)
87
When the beam goes through the mirror it is what type of filtration?
Inherent
87
Describe the difference in HVLs for monoenergitc beams vs polyenergetic beams:
Why?
Monoenergetic - all HVLs are the same thickness
Polyenergetic - Each subsequent HVL will be thicker due to beam hardening
88
How do you calculate the binding energy for the L or M-shell?
E = E (k-shell) - E (L or M-shell)
89
How does kVp affect output?
squared relationship
90
How mA or mAs affect output?
Directly proportional relationship
91
What does a flattening filter do to the avg energy of the beam? Why?
Increases it due to beam hardening
92
Flattening filter filters out __ photons?
low energy
93
Brems produces a monoenergetic or polyenergetic beam?
polyenergetic
94
Characteristic produces a monoenergetic or polyenergetic beam?
monoenergetic
95
Why doesn't this graph start out at 0?
The beam has been hardened, so all low energy photons have been filtered out already.
96
Calculate the avg energy of this graph.
150keV x 1/3 = 50 keV
97
Explain what the peaks are.
Characteristic x-ray of different atoms that are emitted that occur when the electron drops from one orbital to the other after an e- has been ejected from that orbital.
The energy will always be the same for the same atom. The energy is "characteristic" of each atom.
98
A high speed electron passes near a
nucleus and is deflected from its pass after being acted upon by Coulomb forces. They lose energy, slow down and propagates the
energy through space.
Brems
99
"braking radiation"
Brems
100
Brems or Characteristic: Part or all of the electron’s energy may be given off
Brems
101
Electron can engage in multiple ___ interactions
Bremsstrahlung
102
Brems or Characteristic?
Brems
103
Brems or Characteristic: Direction of beam depends on energy.
Breams
104
The higher the energy of a brems beam, the ___ (direction) beam is.
more forward
105
Probability of brems varies with __ of the __.
Z^2, target
106
What determines the energy of the Brem beam?
How close it gets to nucleus and how much it makes it change its path
107
Brems or Characteristic?
Brems
108
An electron interacts with an atom by ejecting an orbital electron which leaves the atom ionized.
Characteristic
109
Describe how a characteristic x-ray occurs: (4 steps)
1. An electron interacts with an atom by ejecting an orbital electron which leaves the atom ionized.
2. A vacancy is created and an outer orbital electron will fall down to a
closer orbital
3. When an electron moves down there is an energy potential, which results in x-rays.
4. Energy potential between orbital levels result in discrete (monoenergetic) energies
110
Characteristic is also called?
Fluoroscence
111
Characteristic
112
Electron capture and ___ are competing processes?
Beta +
113
Characteristic is favored in the __ Z range, while Auger is favored in __.
high, low
114
Which is more likely to occur, a characteristic x-ray or an Auger e-?
Characteristic
115
A is
Atomic mass #, # of nucleons
116
Z is
Atomic #, # of p+
117
Are photons directly or indirectly ionizing?
Indirectly
118
...
Fluence
119
...
Fluence rate or flux density
120
Which interaction independent of Z?
Compton
121
Identify the mode of decay:
Alpha
122
Identify the mode of decay:
B-
123
Identify the mode of decay:
B+ or positron emission
124
Identify the mode of decay:
E- capture
125
Identify the mode of decay: helium nucleus
Alpha
125
Identify the mode of decay: 2 protons, 2 neutrons, no electrons
Alpha
126
Identify the mode of decay:
Excess neutrons (high n/p) ratio, and it must be reduced. Done by emitting an electron.
B-
127
Identify the mode of decay:
neutron to proton
B-
128
Identify the mode of decay:
proton to neutron
B+ or e- capture
129
Identify the mode of decay:
Deficiency in neutrons
B+
130
Identify the mode of decay:
low n/p ratio
B+
131
Identify the mode of decay:
Orbital electron gets captured by nucleus and combines with a proton, transforming into a neutron
E- capture
132
Identify the mode of decay:
Alternative to positron decay; unstable nuclei deficient of neutrons seeks to increase n/p ratio.
E- capture
133
Identify the mode of decay:
Characteristic x-ray or Auger e- can be emitted
E- capture
134
Pair production can lead to ___.
An annihilation reaction.
135
Explain the relationship between Atomic #, n/p+ ratio and stability for heavy nuclei:
For heavy nuclei (atomic # > 20), stable nuclei have a n/p+ ratio of 1.4 to 1 (1.4 neutrons to 1 proton)
136
Explain this graph
For heavy nuclei (atomic # > 20), stable nuclei have a n/p+ ratio of 1.4 to 1 (1.4 neutrons to 1 proton)
137
Explain the relationship between Atomic #, n/p+ ratio and stability for lighter nuclei:
1:1 n/p+ ratio is stable for an atomic # < 20
138
When looking at an equation where decay is taking place, what defines the mode of decay?
The particle that is emitted from the reaction
139
What is the mean life formula?
Ta = 1.44 (T1/2)
140
What is the parent and the daughter?
The parent is the original and the daughter is what the parent decays into.
141
What nuclear reaction is used when making radioactive isotopes? (2 names)
alpha, p+
fusion
142
What nuclear reaction is this?
alpha, proton
143
What particle is this?
Deuteron
144
Nuclear reaction that occurs when high Z nuclei are bombarded by neutrons. After absorbing the neutrons, it splits into nuclei of lower Z, as well as more neutrons.
Fission
145
Fission
146
What are the scales used for each graph?
Left - linear
Right - logarithmic
147
What is the decay constant (definition)?
Portion of atoms decaying per unit time
148
B-
149
B+
150
proton
151
neutron
152
Alpha
153
e- and positron rest mass
9.11 x 10^-31
154
E- rest energy
0.511 MeV
155
rest mass for p+ and neutron
1.675 x 10^-27
156
deuteron rest mass
3.34 x 10^-27
157
alpha rest mass
6.65 x 10^-27 (approx. double deuteron)
158
charge?
-1
159
charge?
+1
160
charge?
+1
161
charge?
0
162
charge?
+1
163
charge?
+2
164
The process by which an unstable nucleus/atom attempts to become stable. This results in emitting radiation (usually a particle) and the transformation of the unstable atom into a different more stable atom.
Radioactive decay
165
What linac component is shown?
Klystron
166
What linac component is shown?
Magnetron
167
What linac component is shown?
Klystron
168
Explain this graph.
Air KERMA is higher in the buildup region. Absorbed dose is higher after the buildup region due to also measuring backscatter.
169
2 modes of decay that are competing processes:
B+ and electron capture
