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Dosimetry Physics 1 > Review Exam 1 > Flashcards

Review Exam 1 Flashcards

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1
Q

Mode of decay when high n/p+ ratio

A

B-

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2
Q

Mode of decay when too many neutrons

A

B-

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3
Q

Mode of decay when too many p+

A

Beta +/Positron emission

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4
Q

Most likely mode of decay for heavier elements

A

Alpha

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5
Q

Mode of decay for PET

A

Positron Emission

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6
Q

Mode of decay that can result in characteristic or Auger e-

A

Electron capture

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7
Q

Isotope

A

same # of p+, diff # neutrons

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8
Q

Isotone

A

Same # of neutrons, diff # p+

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9
Q

Isobar

A

Same # nucleons (both), diff p+

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10
Q

Formula for # of e- in a shell

A

2n^2

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11
Q

speed of light

A

3 x 10^8

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12
Q

The penetrability of the beam is the definition of?
Expressed by what 2 concepts?

A

Beam quality.
HVL or kVp

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13
Q

The # of photons

A

Quantity

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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.

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15
Q

Positive side of x-ray tube

A

anode

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16
Q

negative side of x-ray tube

A

Cathode

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17
Q

What does cathode do?

A

Has tungsten filament that emits e- when heated (thermionic emission occurs here)

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18
Q

What does anode do?

A

Contains tungsten target; electrons hit target to produce x-rays.

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19
Q

Contains tungsten target; electrons hit target to produce x-rays.

A

Anode

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20
Q

Has tungsten filament that emits e- when heated (thermionic emission occurs here)

A

Cathode

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21
Q

3 reasons tungsten is chosen for the target?

A
  1. High Z (high production efficiency)
  2. High melting point
  3. Dissipates heat (prevents overheating)??
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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.

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23
Q

Avg energy of ployenergetic beam is?

A

1/3 max photon energy

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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

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25
Q

Occurs when an uncharged particle
or radiation such as a photon or neutron liberate a directly ionizing particle when they interact with matter.

A

Indirect ionization

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26
Q

Atoms of the target become ionized or excited

A

Direct action

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27
Q

Radiation interacts with other atoms to produce free radicals that then do the damage to critical targets.

A

Indirect action

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28
Q

Interaction dominant in tx range?

A

Compton

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29
Q

Interaction dominant in dx range?

A

Photoelectric

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30
Q

Probability of brems:

A

Z^2

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31
Q

Z of tungsten

A

74

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32
Q

Beam flatness is measured where?

A

10 cm depth in water, but only middle 80% of beam bc of penumbra.

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33
Q

Beam flatness is?

A

of photons

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34
Q

Beam flatness is quantity or quality?

A

Quantity

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35
Q

How does filtration affect the quality of the beam?

A

it hardens the beam

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36
Q

How does filtration affect the quantity of the beam?

A

Reduces it by 4x (to 1/4)

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37
Q

What does beam flatness look like deeper than 10 cm?

A

middle hump

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38
Q

What does beam flatness look like more shallow than 10 cm?

A

lateral horns

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39
Q

Linac Part: changes direction of horizontal beam to vertical

A

Bending Magnet

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40
Q

Linac Part: copper “pipe” held under high vacuum to remove air molecules, where e- are accelerated

A

Waveguide

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41
Q

Energy range for Grenz:

A

10-20kVp

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42
Q

Energy range for Contact therapy:

A

40-50kVp

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43
Q

Energy range for Superficial

A

50-150kVp

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44
Q

Energy range for orthovoltage

A

150-500kVp

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45
Q

Energy range for supervoltge

A

500kVp – 1MV

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46
Q

What is the input electron energy from the electron gun?

A

50 keV

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47
Q

Photon interaction most likely with High Z:

A

Coherent

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48
Q

Photoelectric Z and/or E:

A

Z^3/E^3

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49
Q

Pair production Z and/or E:

A

Z^2

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49
Q

Comp Z and/or E:

A

Ind of Z, depends on e-density

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50
Q

Coherent energy range:

A

<10KeV

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51
Q

Photelectric energy range:

A

60-90 KeV

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52
Q

Compton energy range:

A

25 KeV – 10 MeV

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53
Q

Pair production energy range:

A

> 1.02 MeV

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54
Q

Pneumonic for photon interaction:

A

CoPhoComPair

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55
Q

Coherent - inner or outer shell e-?

A

outer

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56
Q

Photelectric - inner or outer shell e-?

A

inner

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57
Q

Compton - inner or outer shell e-?

A

outer

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58
Q

Pair Production - inner or outer shell e-?

A

inner

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59
Q

What happens to penumbra if you increase SSD?

A

it increases

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60
Q

Klystron vs magnetron:
Cheaper
Shorter lifespan

A

Magnetron

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61
Q

Klystron vs magnetron:
Higher energy
More stable
More expensive

A

Klystron

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62
Q

Klystron vs magnetron:
More common in high energy Linacs

A

Klystron

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63
Q

What linear accelerator component sets the dose rate?

A

Modulator

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64
Q

What components in the linear accelerator treatment head change between electron and photon mode? Photon mode

A

Target and flattening filter is in the carousel when it is in photon mode.

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65
Q

What components in the linear accelerator treatment head change between electron and photon mode? Electron mode

A

Target is removed and scattering foil is put in

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66
Q

Klystron vs magnetron - which one amplifies microwaves?

A

Klystron

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67
Q

Klystron vs magnetron - which one generates microwaves?

A

magnetron

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68
Q

What machine component injects pulsed electrons to waveguide?

A

Electron gun

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69
Q

Variation of dose in comparison to CAX dose at depth of 10cm is the definition for?

A

Flatness

70
Q

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?

A

MU

71
Q

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.

A

Photoelectric Effect

72
Q

Auger and characteristic x-rays can occur with which photon interaction?

A

Photelectric

73
Q

An incoming photon hits an outer orbital electron & not all energy is transferred. This results in an ejected electron and a weaker photon.

A

Compton

74
Q

Annihilation reaction can happen after?

A

Pair production

75
Q

An incoming photon interacts with the nucleus and gives up all of its energy in creating a positron and negatron.

A

Pair production

76
Q

Modes of decay: Combination of two lighter nuclei

A

Nuclear Fusion

77
Q

Modes of decay: Nucleus splits into two

A

Nuclear Fission

78
Q

1 J/kg = ___ Rads = ___ Gy

A

100, 1

79
Q

1 Gy = ___ cGy

A

100

80
Q

1cGy = ___ rad = ___ Gy

A

1, 0.01

81
Q

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.

A

Coherent scatter

82
Q
A
83
Q
A
84
Q

MU: The amount of time to deliver ___, with a __ FS, to a specified depth (usually ___), at a distance of ___ away is the definition of?

A

1 cGy, 10x10 cm, DMAX, 100cm

85
Q

What is meant by “good geometry”?

A

Put the detector where no scatter will be measured.

86
Q

To measure beam flatness, all points must be within __?

A

3%

87
Q

A voltage rectifier does what?

A

Prevents backflow (e- can only go in one direction)

87
Q

When the beam goes through the mirror it is what type of filtration?

A

Inherent

87
Q

Describe the difference in HVLs for monoenergitc beams vs polyenergetic beams:
Why?

A

Monoenergetic - all HVLs are the same thickness
Polyenergetic - Each subsequent HVL will be thicker due to beam hardening

88
Q

How do you calculate the binding energy for the L or M-shell?

A

E = E (k-shell) - E (L or M-shell)

89
Q

How does kVp affect output?

A

squared relationship

90
Q

How mA or mAs affect output?

A

Directly proportional relationship

91
Q

What does a flattening filter do to the avg energy of the beam? Why?

A

Increases it due to beam hardening

92
Q

Flattening filter filters out __ photons?

A

low energy

93
Q

Brems produces a monoenergetic or polyenergetic beam?

A

polyenergetic

94
Q

Characteristic produces a monoenergetic or polyenergetic beam?

A

monoenergetic

95
Q

Why doesn’t this graph start out at 0?

A

The beam has been hardened, so all low energy photons have been filtered out already.

96
Q

Calculate the avg energy of this graph.

A

150keV x 1/3 = 50 keV

97
Q

Explain what the peaks are.

A

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
Q

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.

A

Brems

99
Q

“braking radiation”

A

Brems

100
Q

Brems or Characteristic: Part or all of the electron’s energy may be given off

A

Brems

101
Q

Electron can engage in multiple ___ interactions

A

Bremsstrahlung

102
Q

Brems or Characteristic?

A

Brems

103
Q

Brems or Characteristic: Direction of beam depends on energy.

A

Breams

104
Q

The higher the energy of a brems beam, the ___ (direction) beam is.

A

more forward

105
Q

Probability of brems varies with __ of the __.

A

Z^2, target

106
Q

What determines the energy of the Brem beam?

A

How close it gets to nucleus and how much it makes it change its path

107
Q

Brems or Characteristic?

A

Brems

108
Q

An electron interacts with an atom by ejecting an orbital electron which leaves the atom ionized.

A

Characteristic

109
Q

Describe how a characteristic x-ray occurs: (4 steps)

A
  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
Q

Characteristic is also called?

A

Fluoroscence

111
Q
A

Characteristic

112
Q

Electron capture and ___ are competing processes?

A

Beta +

113
Q

Characteristic is favored in the __ Z range, while Auger is favored in __.

A

high, low

114
Q

Which is more likely to occur, a characteristic x-ray or an Auger e-?

A

Characteristic

115
Q

A is

A

Atomic mass #, # of nucleons

116
Q

Z is

A

Atomic #, # of p+

117
Q

Are photons directly or indirectly ionizing?

A

Indirectly

118
Q

…

A

Fluence

119
Q

…

A

Fluence rate or flux density

120
Q

Which interaction independent of Z?

A

Compton

121
Q

Identify the mode of decay:

A

Alpha

122
Q

Identify the mode of decay:

A

B-

123
Q

Identify the mode of decay:

A

B+ or positron emission

124
Q

Identify the mode of decay:

A

E- capture

125
Q

Identify the mode of decay: helium nucleus

A

Alpha

125
Q

Identify the mode of decay: 2 protons, 2 neutrons, no electrons

A

Alpha

126
Q

Identify the mode of decay:
Excess neutrons (high n/p) ratio, and it must be reduced. Done by emitting an electron.

A

B-

127
Q

Identify the mode of decay:
neutron to proton

A

B-

128
Q

Identify the mode of decay:
proton to neutron

A

B+ or e- capture

129
Q

Identify the mode of decay:
Deficiency in neutrons

A

B+

130
Q

Identify the mode of decay:
low n/p ratio

A

B+

131
Q

Identify the mode of decay:
Orbital electron gets captured by nucleus and combines with a proton, transforming into a neutron

A

E- capture

132
Q

Identify the mode of decay:
Alternative to positron decay; unstable nuclei deficient of neutrons seeks to increase n/p ratio.

A

E- capture

133
Q

Identify the mode of decay:
Characteristic x-ray or Auger e- can be emitted

A

E- capture

134
Q

Pair production can lead to ___.

A

An annihilation reaction.

135
Q

Explain the relationship between Atomic #, n/p+ ratio and stability for heavy nuclei:

A

For heavy nuclei (atomic # > 20), stable nuclei have a n/p+ ratio of 1.4 to 1 (1.4 neutrons to 1 proton)

136
Q

Explain this graph

A

For heavy nuclei (atomic # > 20), stable nuclei have a n/p+ ratio of 1.4 to 1 (1.4 neutrons to 1 proton)

137
Q

Explain the relationship between Atomic #, n/p+ ratio and stability for lighter nuclei:

A

1:1 n/p+ ratio is stable for an atomic # < 20

138
Q

When looking at an equation where decay is taking place, what defines the mode of decay?

A

The particle that is emitted from the reaction

139
Q

What is the mean life formula?

A

Ta = 1.44 (T1/2)

140
Q

What is the parent and the daughter?

A

The parent is the original and the daughter is what the parent decays into.

141
Q

What nuclear reaction is used when making radioactive isotopes? (2 names)

A

alpha, p+
fusion

142
Q

What nuclear reaction is this?

A

alpha, proton

143
Q

What particle is this?

A

Deuteron

144
Q

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.

A

Fission

145
Q
A

Fission

146
Q

What are the scales used for each graph?

A

Left - linear
Right - logarithmic

147
Q

What is the decay constant (definition)?

A

Portion of atoms decaying per unit time

148
Q
A

B-

149
Q
A

B+

150
Q
A

proton

151
Q
A

neutron

152
Q
A

Alpha

153
Q

e- and positron rest mass

A

9.11 x 10^-31

154
Q

E- rest energy

A

0.511 MeV

155
Q

rest mass for p+ and neutron

A

1.675 x 10^-27

156
Q

deuteron rest mass

A

3.34 x 10^-27

157
Q

alpha rest mass

A

6.65 x 10^-27 (approx. double deuteron)

158
Q

charge?

A

-1

159
Q

charge?

A

+1

160
Q

charge?

A

+1

161
Q

charge?

A

0

162
Q

charge?

A

+1

163
Q

charge?

A

+2

164
Q

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.

A

Radioactive decay

165
Q

What linac component is shown?

A

Klystron

166
Q

What linac component is shown?

A

Magnetron

167
Q

What linac component is shown?

A

Klystron

168
Q

Explain this graph.

A

Air KERMA is higher in the buildup region. Absorbed dose is higher after the buildup region due to also measuring backscatter.

169
Q

2 modes of decay that are competing processes:

A

B+ and electron capture

Dosimetry Physics 1 (7 decks)

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