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MRT > MED RAD FINAL EXAM > Flashcards

MED RAD FINAL EXAM Flashcards

1
Q

Radiation is transmitted through

A

waves and particles

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2
Q

List radiation types

A

electromagnetic, acoustic, particulate, gravitational

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3
Q

List wave features

A

amplitude, frequency, wavelength, period

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4
Q

Explain amplitude

A

max strength of wave

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5
Q

Increase amplitude =

A

increase intensity

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6
Q

Explain frequency

A

number cycles per second (Hz) - number of times going up / down

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7
Q

Increase frequency =

A

increase intensity

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8
Q

Explain wavelength

A

distance between 2 same wave points

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9
Q

Shorter wavelength =

A

increase intensity, higher energy

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10
Q

Explain period

A

how long each wave cycle takes

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11
Q

Charges have an ________ field around them

A

electric

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12
Q

Moving charges create a _________ field

A

magnetic

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13
Q

Disturbance in a charge creates ____________ waves

A

electromagnetic

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14
Q

Explain “electric and magnetic fields are perpendicular to the direction of energy”

A

electric and magnetic fields travel horizontally and vertically down the wave at at 90 degree angle

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15
Q

Photons are the quantum form of ___________

A

EMR (electromagnetic radiation)

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16
Q

What properties do low E EMR have?

A

wave like properties

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17
Q

What properties do high E EMR have?

A

particle like properties

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18
Q

Explain purple / blue end of the EMR spectrum

A

High E, High frequency, shorter wavelength

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19
Q

Explain red end of the EMR spectrum

A

low E, low frequency, longer wavelength

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20
Q

EMR travels at?

A

speed of light in a vacuum

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21
Q

waves and C (speed of light) formula

A

C = f x wavelength

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22
Q

Energy formula

A

E = h x f

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23
Q

Most of the x-ray beam is high or low E photons?

A

low E photons

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24
Q

Two processes that create xrays

A

characteristic and brems radiation

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25
Q

characteristic radiation process

A

electron hits inner shell electron, knock it out of orbit, outer shell electron drops into vacancy (usually L), releases E in form of x-ray photon

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26
Q

characteristic radiation only affected by what?

A

atomic number

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27
Q

brems produces mostly ________ photons

A

low energy

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28
Q

Photons produce what?

A

EMR

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29
Q

Energy travels as _________ waves

A

sinusodial

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30
Q

Electric and magnetic fields are _________ to the direction of energy

A

perpendicular (90)

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31
Q

What does ionize have the ability to do?

A

remove electrons from atoms (ex. CS and PE, gamma, x-ray) - creates ions

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32
Q

Why is coherent scatter non-ionizing?

A

because it doesn’t have enough energy to remove electrons from atoms - it’s LOW E

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33
Q

What is wave like particle duality

A

waves can exhibit particle-like properties while particles can exhibit wave-like properties

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34
Q

c = __ x ___ ^ m/s

A

c = 3 x 10^8 m/s

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35
Q

Order of colours in EMR

A

purple, blue, green, yellow, orange, red

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36
Q

List wavelike interactions:

A

reflection, refraction, diffraction, interference

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37
Q

Explain reflection

A

Bounces off surface, changes direction (not absorbed)

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38
Q

Explain refraction

A

Change in direction from speed (ex. straw bending in water)

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39
Q

Explain diffraction

A

wave bends around boarders to create pattern

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40
Q

Explain interference

A

Waves add together (constructive) OR cancel out (destructive)

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41
Q

Do x-rays diffract?

A

yes (atomic planes of a crystal cause an incident beam of X-rays to interfere with one another)

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42
Q

Define quantum and example

A

smallest unit of something (photon = x-rays)

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43
Q

What occurs during excitation?

A

excites electron to higher E level, no charge change - non ionizing

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44
Q

Are high or low energy photons more harmful?

A

low, because high E photons are more likely to penetrate

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45
Q

Explain beam spectra features: max E

A

highest energy possible (furthest right), depends on kvp

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46
Q

Explain beam spectra features: low E

A

lowest energy possible (furthest left), filtration (filters out low E), mostly produced by brems

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47
Q

Explain beam spectra features: avg E (effective beam E)

A

affected by waveform, atomic number, filtration - 1/3-1/2 of peak - tallest peak

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48
Q

Explain beam spectra features: line spectra

A

depends on atomic number, contsant E level, shouldn’t move until atomic number changes - fixed E

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49
Q

In a graph for beam/emission spectra look for changes in:

A

height, avg E, line spectrum, max / min

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50
Q

Explain emission spectra changes involving: kvp

A

shift on the “x” axis of graph - increase in kvp causes increased photons / max E / avg E

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51
Q

Explain emission spectra changes involving: ripple

A

Avg E / height change - decreased ripple causes increased photons / avg E (low ripple has MORE energy = higher height). Shifts left (increased ripple = decreased photons)

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52
Q

Explain emission spectra changes involving: filtration

A

increased filtration causes decreased photons, increased avg E (shifts to the right)

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53
Q

Explain emission spectra changes involving: mA

A

affects curve height (change will occur in the same spot - no shift), increase mA causes increased photons (equal increase)

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54
Q

Explain emission spectra changes involving: atomic number

A

line spectrum (char): increased Z causes increased photons / avg E. Brems: avg E to the right as atomic number increases

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55
Q

Max E on a spectra graph only moves on x axis if what changes?

A

kvp

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56
Q

What does filtration help with?

A

improving image quality by decreasing low E photons

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57
Q

Avg E of 100 kev

A

100 / 2 and 100 / 3 = 33 to 50

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58
Q

Larger area under graph =

A

larger intensity

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59
Q

K BE and L BE tungsten

A

69 and 12

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60
Q

What percent of beam is characteristic radiation?

A

0-10%

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60
Q

Electron must have at least ______ to dislodge in char rad

A

70

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60
Q

Anything less than 69 =

A

no char rad

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60
Q

Characteristic radiation only exist at ________ levels

A

certain energy

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60
Q

K - shell BE is high or low E?

A

high E

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61
Q

How many possibilities with char rad?

A

5

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62
Q

Brems is _____ of the beam

A

90%

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63
Q

What percent becomes xrays and heat?

A

x-rays = 1%, heat = 99%

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64
Q

What do electrons do?

A

orbit around the nucleus

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65
Q

Define binding energies

A

E required to remove an electron from atom

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66
Q

AEC location in mammo and why?

A

After IR ; allows decreased OID with breast

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67
Q

What decreases anode heel effect in mammo?

A

tube tilt - allows for maintained CR + SR

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68
Q

Mixed target and filter in mammo is what kind of radiation?

A

brems rad

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69
Q

same target and filter in mammo is what kind of radiation?

A

char rad

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70
Q

Why do we use molybdenum in mammo?

A

low atomic number, spike at 17-19 kev

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71
Q

Energy molybdenum and rhodium?

A

Mo = 17-19 kev and Ro = 20-23 kev

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72
Q

Grounded metal tube used in mammo prevents?

A

off focus radiation

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73
Q

Most of mammo beam is?

A

char rad

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74
Q

SR factors in mammo

A

compression, small FS, AEC location (after), IR (direct), grounded metal tube (decrease off focus rad), OID

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75
Q

CR factors in mammo

A

Compression, beam E, grid, tube orientation (Chest-cathode, BT-anode), tube tilt

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76
Q

Magnification mode factors in mammo

A

No grid (uses air gap technique), done to look at a. certain area - middle is sharper, uses increased OID and small FS - increased SR (pixels) / CR (photons)

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77
Q

Increase or decrease PT dose mammo: compression

A

decrease (compression decreases thickness so less penetration / kvp needed)

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78
Q

Increase or decrease PT dose mammo: Beam E

A

increase

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79
Q

Increase or decrease PT dose mammo: tomosynthesis

A

increase (multiple images at once)

80
Q

Increase or decrease PT dose mammo: mag mode

A

same - because no grid is used so it balances out

81
Q

Increase or decrease PT dose mammo: grid

A

increase (higher exp time needed to compensate)

82
Q

Increase or decrease PT dose mammo: short SID

A

increase (higher intensity - BT)

83
Q

Does shorter SID / small angle increase or decrease anode heel effect?

A

Increase (tilt is used)

84
Q

increased mAs = ________ pt dose

A

increased (longer exp)

85
Q

What affects beam E in mammo?

A

using Mo / Ro, kvp, filtration

86
Q

Low E interacts with __________

A

molecules & atoms

87
Q

Medium E (diagnostic) interacts with ____________

A

electron

88
Q

High E (NOT in diagnostic) interacts with __________

A

nucleus (ignores electrons)

89
Q

Define attenuation - examples

A

beam / rad intensity loss - absorption and scatter

90
Q

Chest has _______ natural subject contrast

A

high (high kvp to smooth it out)

91
Q

Breast has _______ natural subject contrast

A

low (low kvp can help increase SC)

92
Q

In image, CS shows difference in _______

A

density

93
Q

In image, PE shows difference in _______

A

atomic number and density

94
Q

Magic number for bone and soft tissue

A

Bone: 40, ST: 20

95
Q

What occurs above / below the magic # for bone and soft tissue?

A

above 40/20 = scatter, below 40/20 = absorption

96
Q

Magic number where both CS and PE have a chance of occuring

A

at 80 kvp they have a 50/50 chance of occuring

97
Q

what occurs above / below the magic # for CS/PE?

A

bwloq 80 = more chance of absorption (grey shades), above 80 = more chance of scatter

98
Q

High kvp = _______ absorption

A

decreased

99
Q

Increase Z = _______ PE

A

increased

100
Q

Increased E = _______ CS/PE

A

decreased

101
Q

Other name(s) for CS?

A

modified scatter

102
Q

Other name (s) for coherent scatter?

A

unmodified, thomson, rhyleigh, classical

103
Q

Energy CS is left with after interaction?

A

66% (2/3)

104
Q

Energy of a photon formula

A

KE = hf - BE (Energy of the photon minus the BE)

105
Q

Explain occurrence of k-edge

A

Sudden increase in absorption of x-rays that occur when the E is just above the BE

106
Q

Greatest probability of absorption (PE) happening

A

Photon E just above BE, none if it’s below

107
Q

PE interaction

A

x ray photon comes in, ionizes atom - inner k-shell electron ejected, all energy absorbed, outer shell electron drops in, secondary characteristic radiation & photoelectron created

108
Q

Probability of photoelectron effect occurring formula atomic number and energy

A

𝑃𝐸 = 𝑍^3/𝐸^3

109
Q

No chance of absorption when?

A

photon E below BE

110
Q

How does PE affect the patient?

A

All E from interaction goes to PT (absorbed) - so photon has lower E after interaction

111
Q

End products for PE

A

photoelectron and secondary char rad

112
Q

End products for coherent scatter

A

scattered photon

113
Q

End products for CS

A

ion pair (positive atom, compton electron) and scattered photon

114
Q

CS interaction

A

X-ray photon comes in, Ionizes atom, knocks OUTER shell electron out (CAN be inner shell – but usually outer), changes direction (direction change depends on E), loses some energy, creates ion pair and scattered photon

115
Q

Coherent scatter affect on pt?

A

none - no tissue damage occurs - E is kept by atom

116
Q

Coherent scatter interaction

A

x-ray photon comes in, EXCITES atom, changes direction, scattered photon created ; maintains all it’s E (same E, freq, wavelength)

117
Q

How rare is coherent scatter?

A

rarely occurs - less than 5%

118
Q

Scatter effect on image?

A

decreased quality - grain / decreased contrast

119
Q

Pair production interaction

A

photon comes in, interacts with nucleus, nucleus rips it into two, creates positron and electron - E level 1.02 mEv

120
Q

Photodisintgration interaction

A

photon comes in, interacts with nucleus, nucleus releases apart of itself (nuclear fragment) - E level 10 mEv

121
Q

Probability of coherent scatter occurring?

A

Higher Z / low E - when you have wayyyyyy higher BE than photon E (so, not with human tissue)

122
Q

What does PE magnify image wise?

A

Subject contrast - able to show detail / differences in tissues (lower kvp use)

123
Q

What do each CS / PE show differences in

A

CS = density, PE = atomic number and density

124
Q

Probability of CS occuring?

A

when photon E much higher than BE

125
Q

Difference in x-ray photos are mostly due to

A

absorption

126
Q

What happens once k-edge is hit?

A

huge spike of absorption

127
Q

As E increases, what happens to CS/PE?

A

both decrease

128
Q

Why lower kvp with abdomen than chest ?

A

want to heighten subject contrast like the kidneys / bowels

129
Q

When imaging the chest, especially with a female patient, want to use a high or low kvp? why?

A

With a high kvp the breast would show up grey like other soft tissue

130
Q

Why does mammo use low kvp?

A

Less penetration power needed because breast is just ST/Fat, and low kvp allows for more absorption = increased subject contrast to show details in breast

131
Q

Mo BE?

A

20 kev (will allow photons in JUST below - 17-19)

132
Q

KeV best for imaging breast?

A

17-24 kEv

133
Q

K-edge filters all but ______ with Mo

A

17-19kev

134
Q

Rhodium BE

A

23 kev

135
Q

K-edge filters all but ______ with Ro

A

20-23 kev

136
Q

Why is char rad needed for k-edge to occur?

A

because char rad is what gives it the spike

137
Q

Smaller space charge in mammo why?

A

because the cathode and anode are closer together

138
Q

Chances of space charge occurring _______ with low kvp

A

increases

139
Q

The shorter distance with the cathode and the anode in mammo allows for?

A

less intensity loss in the beam (attenuation)

140
Q

Con of short SID distance in mammo?

A

increased pt dose, increased anode heel, decreased sharpness (beam divergence)

141
Q

How to decrease anode heel effect in mammo?

A

tube tilt - 20-24 degrees - allows SR to be maintained, and having chest wall at cathode end, BT at anode end

142
Q

AEC location in mammo

A

after IR

143
Q

Use of ______ FS size in mammo allows for ______

A

small, better SR / detail

144
Q

Digital tomosynthesis in mammo increases ____ resolution

A

CR

145
Q

Can PE cause new ionizations?

A

yes

146
Q

PE is made up of

A

char rad

147
Q

PT dose with PE?

A

ALL E to patient, so high pt dose

148
Q

Why is subject contrast higher with PE?

A

because absorption is a factor with subject contrast (density/thickness), the more absorbed, the better the subject contrast

149
Q

Why does chances of absorption decrease with increased energy?

A

because the energy of the photons are too high to be absorbed

150
Q

Can coherent scatter cause ionization ?

A

no, too low of E - just excites (non ionizing)

151
Q

Decreased E in CS after interaction leads to

A

longer wavelength, decreased freq, decreased E

152
Q

Probability of PE occurring density formula

A

𝑃𝐸 = density^1

153
Q

Probability of CS occurring density formula

A

CS = d/E^1

154
Q

As E in increases, probability of PE decreases _______ and CS decreases _______

A

PE - sharply, CS - gradually

155
Q

Can CS cause new ionizations?

A

Yes

156
Q

Can pair production cause new ionizations?

A

yes

157
Q

Can photodisintegration cause new ionizations?

A

yes

158
Q

With tungsten K shell BE 69, what would happen with photons with 60 kev?

A

they’d likely be absorbed (and too high for L shell)

159
Q

Will CS graph have k-edge?

A

no, only PE (bc k-edge is absorption)

160
Q

How to calculate avg E? kvp

A

multiply kvp value by 2 and 3, any number in between is the Avg E

161
Q

How to figure out “what is the KE of the photoelectron”

A

E - BE (KE = hf - BE)

162
Q

If small diff in density, and very large diff in atomic number, which would show contrast? CS, PE, or both

A

PE (atomic number high) - both if density is larger diff

163
Q

Diff in photo mostly due to

A

absorption

164
Q

Why increase kvp with chest?

A

because chest has high natural subject contrast - so high kvp helps smooth it out, and higher kvp with female helps penetrate BT / show grey values

165
Q

Is mammo mostly PE or CS?

A

PE

166
Q

Probability of k-edge with L-shell

A

with very low E photons - decreases as E increases

167
Q

What does a filter allow for?

A

only a narrow range of photons through

168
Q

photons transmitted vs absorbed

A

Transmitted: X-rays pass through the material with little or no energy loss.
Absorbed: X-rays transfer all of their energy to the material and do not pass through

169
Q

What photons will be transmitted and what photons will be absorbed, with k-edge?

A

absorbed: photons with E just above the BE
transmitted: photons with E JUST below BE

170
Q

with K shell, ______ probability if below BE

A

zero (ex. 68)

171
Q

with K shell, _______ probability if above BE

A

greatest

172
Q

Does human tissue k-edge?

A

no, too low

173
Q

Ex. 80 kvp beam – only photons between 59-68 in the beam, meaning?

A

15% (80x0.15 = 12, 80-12 = 68)

174
Q

Will k-edge occur with contrast?

A

yes, because high Z

175
Q

calculate “kvp range”

A

BE x 2, BE x 3 = number in between

176
Q

Faster IR’s are better at ________

A

absorption (requires less mAs)

177
Q

High atomic number = _______ absorption

A

increased

178
Q

Heavy element filters absorb _______ E photons and lets in those _______ the BE

A

low, just under

179
Q

For IR to produce an image, must ______ radiation

A

absorb

180
Q

Can use a lower mAs with ______, which has better absorption and patient dose

A

rare earth

181
Q

Examples of ionizing radiation

A

gamma, xrays

182
Q

Examples of non-ionizing

A

Radiowaves, microwaves

183
Q

are high or low energy photons more penetrating?

A

high

184
Q

Most of x-ray beam is ________ E photons

A

low

185
Q

Purpose of fluorescence ?

A

emits x-rays after interaction

186
Q

Name of char rad depends on what?

A

depends on the shell being filled

187
Q

All mean the same thing with: char rad

A

discrete, line, homogenous, monoenergetic

188
Q

10% of beam is char rad at what kvp

A

70-150 kvp

189
Q

Differences between char rad & PE

A

PE - all E absorbed to patient, and involves photon
Char rad - occurs in the tube, involves electrons

190
Q

How are x-rays released in brems rad?

A

deceleration

191
Q

With brems, deceleration closer to the nucleus results in what?

A

Higher energy x-ray photon and more speed loss

192
Q

With brems, deceleration further from the nucleus results in what?

A

Lower E x-ray photon and less speed loss

193
Q

Explain Brems rad interaction

A

x-ray electron pass by nucleus, change direction

194
Q

Mean the same thing in Brems:

A

polyenergentic, heterogeneous, continuous

195
Q

Brems end product

A

Brems x-ray photon

196
Q

No char rad produced below ______

A

70 kvp (below 70kvp would be brems)

197
Q

Area under graph = _______

A

intensity

198
Q

Photons in brems can exist at _______

A

any E lvl

199
Q

In order for brems to hit peak, has to what?

A

hit nucleus - which is rare

200
Q

Determining peak is

A

1/3-1/2

201
Q

Max E is determined by

A

kvp

202
Q

Decrease ripple =

A

Increased E / photons

MRT (12 decks)

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