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RAD 350 - Naomi > TEST 2 > Flashcards

TEST 2 Flashcards

1
Q

What does a line compensator do?

A

modify and adjust incoming voltage to be consistent 220V

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2
Q

Kinetic energy in x-ray system

A

kVp setting provides large potential difference to give kinetic energy to filament electrons

mAs provides electrons flow (tube current)

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3
Q

KE –> electromagnetic energy

A

electrons flow from cathode to anode

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4
Q

potential energy in xray

A

Voltage

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5
Q

Potential energy in x-ray

A

Voltage

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6
Q

What does an autotransformer do

A

directly determine voltage applied to x-ray tube through kVp selector

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7
Q

Is the autotransformer adjustable?

A

YES

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8
Q

What is autotransformer made of

A

single coil of insulated wire wound around a large iron core

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9
Q

How are X-ray produced

A

1.electrons boiled off the filament –> filament e-
2. interact with the target anode or nucleus that could lead to the release of Characteristic & Brems x-ray photons (1%) AND heat (99%)

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10
Q

What do major & minor kVp selector do

A

both to select kVP desired
minor: fine tune the technique

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11
Q

3 components of X-ray circuit

A

operating console
high-voltage generator
x-ray tube

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12
Q

What does kVp meter do

A

read voltage before exposure

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13
Q

What does timing circuit (exposure time) do

A

regulate duration of x-ray exposure
control low voltage

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14
Q

4 types of timing circuit

A

Synchronous
Electric
mAs
Automatic Exposure Control (AEC)

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15
Q

What is the limitation for Synchronous timers

A

cannot be used for serial exposures because it must be reset after each exposure

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16
Q

Synchronous timer

A

use motor that operates at frequency of 60hz @ 60 rotations per second

timer: 1/60s increment

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17
Q

Electric timer

A

microprocessor controls it

based on time it takes to charge a capacitor through variable resistor

1ms

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18
Q

mAs timer

A

terminate exposure when desired mAs is obtained

located in 2nd circuit

provides safe tube current in shortest time possible

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19
Q

AEC

A

measure quantity of radiation that reach IR.

has an ionization chamber

required precise position skills

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20
Q

[AEC ] what is the
ionization chamber? what does it do

A

radiolucent device that control exposure when activated

It adjust the amount of necessary radiation to send exposure terminal signal to IR

when there is efficient voltage/ ionization, operational amplifier terminate exposure

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21
Q

What does AEC backup timer do

A

terminate exposure in case of malfunction

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22
Q

What is good about AEC backup timer

A

protects from tube from overheating and patient from overexposure

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23
Q

What is bad about AEC backup timer

A

timer is too short –> underexposed image

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24
Q

What does Step-UP transformer do

A

increase voltage from autotransformer by a fixed amount
(V–> kV)

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25
Q

Change in voltage & current is an _____ relationship

A

inverse

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26
Q

What does Step-DOWN transformer do

A

increase current by reducing voltage that applied to the filament

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27
Q

What activated step-down transformer

A

mA adjustment

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28
Q

What does mA selector do

A

control Amperage in filament circuit. In other words, control rate which e- boiled off

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29
Q

What does Rectifier do

A

convert AC–> DC

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30
Q

What is the process of Rectification

A

solid-state rectifier banks are arranged in pairs to route current through xray tube each time

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31
Q

What does rectifier make of?

A

solid-state semiconductor diode (2 electrodes)

current ( + to -)
electron (- to +)

electricity pass through rectifier, created + charge on the anode & - charge on the cathode focusing cup

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32
Q

Half-wave rectification

A

no electric current
no negative swing during half of its cycle

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33
Q

Half-wave rec contains how many diodes

A

0, 1 or 2

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34
Q

Half-wave rec produce how many x-ray pulse per second

A

60

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35
Q

Cons of half-wave rect

A

waste 1/2 of its power–> double exposure time

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36
Q

Full-wave rec contain how many diodes

A

4 in high-voltage circuit

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37
Q

What does High-Voltage Generator do

A

increase V from autotransformer to kVp

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38
Q

3 parts of High-Voltage Generator

A

high voltage (step up transformer)
step down filament transformer
rectifiers

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39
Q

What does mA meter do

A

monitor xray tube current

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40
Q

What is single-phase power

A

resulted from pulsating x-ray beam

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41
Q

Characteristics of single-phase power

A

low in energy, penetrability

little diagnostic value

100% ripple

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42
Q

what is the benefit of 100% ripple in single-phase

A

less energy waste

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43
Q

Characteristics of three-phase power

A

multiple waves at constant high voltage

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44
Q

what is the benefit of less ripple in three-phase power

A

Voltage never drop to 0 during exposure = constant energy

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45
Q

What is a ripple

A

energy fluctuate from 0 to max voltage

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46
Q

What do high-frequency generator do

A

Improve waveforms
smooth V
reduce ripple from three-phase full wave
change incoming-line voltage frequency

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47
Q

Benefit of high-frequency generator

A

produce xray with consistent energy levels

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48
Q

3 external components of xray tube

A

support structure
protective housing
glass or metal enclosure

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49
Q

What is an X-ray tube

A

electronic vacuum, contains 2 electrode inside a glass/metal enclosure

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50
Q

purpose of glass or metal enclosure

A

creates vacuum tube to pack electrons tightly together = more efficiency and longer tube life

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51
Q

Why use glass enclosure

A

high melting point to withstand heat

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52
Q

Why use metal enclosure

A

maintain constant electric potential = longer life tube

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53
Q

Purpose of x-ray tube window

A

emit useful beam

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54
Q

For the xray tube, Lead is built in everywhere except

A

tube window

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55
Q

Another name for primary beam

A

useful beam

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56
Q

What is leakage

A

2nd type of radiation
escape protective housing

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57
Q

3 purpose of protective housing

A

covers tube with lead to reduce leakage
prevents electric shock
mechanical support

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58
Q

Some protective housing contains oil which serves as

A

insulator for electricity
dissipate heat

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59
Q

components of cathodes

A

filament(tungsten-thorium alloy) and focusing cup (nickel)

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60
Q

when thermionic emission occur

A

when filament is heated up and emits electrons

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61
Q

What material made up filament

A

Tungsten

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62
Q

What is the charge of focusing cup and its purpose

A

neg charged
accelerate electrons within a confined space –> focuses electrons to hit focal spot

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63
Q

Location of focusing cup

A

cathode

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64
Q

explain how can focusing cup force electrons together into a cloud when both of their charges are negative

A

the neg charge of focusing cup is greater than the neg of e-. Individual electron-neg charge cause them to repel and scatter as they boiled of the filament

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65
Q

Location of focal spot

A

anode

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66
Q

3 Functions of anode

A

electrical conductor
mechanical support for target
thermal dissipater

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67
Q

Types of anode

A

stationary and rotating

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68
Q

pro of rotating anode

A

spins target = more surface area for electrons to hit ==> high intensity xray beams in short time

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69
Q

What drives the anode

A

electromagnetic induction motor

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70
Q

Difference b/w stator & rotor

A

stator: has electromagnets
rotor: shaft made of bars of copper & soft iron

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71
Q

what is the target

A

area of where electrons hit the anode from cathode

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72
Q

Why Tungsten is used as a material for the Target

A

high atomic # –> high efficiency x-ray production

high thermal conductivity –> efficient at dissipating heat

high melting point –> withstand high tube current w/o bubbling

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73
Q

What is a focal spot

A

area of target from which x-ray are emitted

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74
Q

What size of focal spot produce image with better spatial resolution

A

small effective focal spot

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75
Q

The ___ focal spot = the greater heat concentration. Therefore we need a large actual focal spot.

A

smaller

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76
Q

The focal spot size is determined by __

A

filament size

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77
Q

The focal spot size is determined by __

A

filament size

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78
Q

What is line focus principle

A

Target is angled (5-20 degrees) to allow large area for heating while maintaining small focal spot

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79
Q

How do we create small effective focal spot

A

angle the target (anode) 5-20 degrees to change size of effective focal spot

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80
Q

line focus principle is good for what?

A

greater heat capacity and better radiographic image sharpness

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81
Q

what is the effect for
-large actual focal spot
-small effective focal spt

A

-maintain heat dissipation
- improve image quality

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82
Q

What is anode heel effect

A

radiation intensity on cathode is higher than on the anode

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83
Q

Effective compensation for the anode heel effect would involve positioning:

A

the thinnest portion of the body part under the anode.

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84
Q

Explain why the intensity at cathode side is stronger than anode side

A

x-ray constitute to the useful beam emitted tw the cathode traverse a lesser thickness of target material than anode

85
Q

Why anode heel effect important

A

imaging anatomic structure that varies in thickness or mass density

86
Q

A ____ angle tube will give greater anode heel effect

A

SMALL

87
Q

What are 3 causes of x-ray tube failure

A

Heat
maintaining anode at elevated temperature for prolonged period
filament (high temp cause filament to vaporize)

88
Q

What effect does temperature have on filament

A

high temp cause them to vaporize

89
Q

The X-ray tube is very thermal. What are the 3 ways to dissipate heat for tube

A
  1. radiation
  2. conduction
  3. convection
90
Q

Explain radiation as a way to dissipate heat

A

transfer heat by emission of infrared radiation (light)

91
Q

Explain conduction as a way to dissipate heat

A

transfer energy from one objec to another

92
Q

Explain convection as a way to dissipate heat

A

transfer heat by movement of heated substance from one place to another

93
Q

3 things needed to produce X-ray

A
  1. kVp provide large potential difference to give energy for filament e-
  2. mAs giving quantity of e-
  3. the target anode for e- to interact
94
Q

Example of conduction

A

heat-tolerant materials

95
Q

Example of radiation

A

heat energy from anode to oil bath

96
Q

Example of convection

A

rotating anode
cooling fans

97
Q

What do you do to extend tube life

A
  1. warm up the tube before normal operations
  2. maintain filament in an energized state –> shortens its useful life.
    3.no use of extreme exposure factors
98
Q

Radiographic rating chart conveys ___

A

which radiographic techniques are safe & unsafe for x-ray tube operation

99
Q

Anode cooling chart conveys _____

A

thermal capacity of anode & its heat dissipation

100
Q

Housing cooling chart conveys___

A

thermal capacity of housing & its heat dissipation

101
Q

Rotating anode is made of ____

A

copper

102
Q

Why copper for rotating anode

A

good at thermal and electricity

103
Q

Why molybdenum is used

A

low thermal conductivity
tensile strength

104
Q

How does rotating anode turn

A

use induction motor to operate through electromagnetic mutual induction

105
Q

How does angling the target affect the intensity of beam on anode side

A

the heel of target is partially in the path of xray beam produced –> cause absorption and reduce intensity of beam on anode side

106
Q

what reduces leakage radiation to required standards

A

protective housing

107
Q

Primary function of x-ray imaging system

A

speed up electrons from cathode to anode

108
Q

Speed of electrons determine _____

A

if excitation or ionization happened

109
Q

Heat is ____ rather than ___

A

excitation - ionization

110
Q

what is ionization

A

transfer sufficient energy to overcome BE of orbital electrons eject them from atom

111
Q

Heat is ___ proportional to the tube current and kVp

A

directly

112
Q

increase kVp will ____ efficiency of x-ray production

A

increase ==> better quality x-ray w/o overheating tube

113
Q

What is responsible for most of the heat in the xray tube

A

cycle of outer-shell electron excitation and neutralization

114
Q

How is heat produced?

A

filament e- enters anode target and interact with outer-shell electrons. They transfer sufficient energy to excite. This excess energy is given of as infrared radiation (light)

115
Q

when does Brems radiation occur

A

when incident electron interacts with force field of nucleus

116
Q

What is required for incident electron to interact with the force field of nucleus to produce Brems

A

incident electrons must have enough energy to pass by orbital electrons without interacting

117
Q

How are Brems photons produced?

A

incident electrons interacts with force field of nucleus creates a force of attraction between the 2. This attraction slows down electrons and make them change direction which causes loss of kinetic energy. This energy is released as Brems photons

118
Q

What is the energy of Brems photons

A

difference between the entering - exiting KE of electron

119
Q

More loss of KE when e- pass close to the nucleus results in ____

A

more Brems photon

120
Q

Why 1 e- can cause many x-ray

A

after the first interaction, the e- can go on to interact with different atoms before losing all of its energy

121
Q

When does Characteristics radiation occur

A

when e- interacts with inner-shell electron

122
Q

What is required for incident electrons to produce Characteristics photons

A

enough energy to knock inner-shell electron from orbit

123
Q

At what kVp levels Characteristic X-rays are produced

A

above 70

124
Q

How are Characteristics photons are produced

A

If energy of incident photon is greater than the BE of orbital electron, the electron is removed from the orbit => Unstable => e- from outer shell drop expend its PE to fill in the vacancy. This energy is given off as Characteristic photons

expending of energy during cascade that produce characteristic xray

125
Q

Electrons drop into ___ -shell produce ____ within diagnostic xray range

A

K
characteristics

126
Q

The effective energy of characteristic xrays increase with _____

A

increase atomic number of target element

127
Q

What is ionization

A

adding or removing electron from an atom

128
Q

What happened to X-ray when they interact with matter

A
  1. can be absorbed (attenuation)
  2. can partially transfer energy and scatter
  3. pass through matter unaffected (direct transmission)
129
Q

Can we predict what happen to a single photon

A

NO - the interaction is random
Can only predict what happened on the average

130
Q

what does moderate energy xray interact with?

A

electrons

131
Q

what does high energy xray interact with?

A

nuclei

132
Q

what does low energy xray interact with?

A

whole atoms

133
Q

2 factors determine types of interaction between photons and atoms

A
  1. atomic number of atom
  2. energy of photons
134
Q

5 types of patient interactions

A
  1. classical (coherent scattering)
  2. photoelectric interaction
  3. compton interaction
  4. pair production
  5. photodisintegration
135
Q

does the photons always interact with atoms?

A

no –> atoms = empty space –> passes through without interactions

136
Q

What is produced for coherent scattering and how?

A

Scatter x-rays are produced as extra energy with a wavelength equals to incident x-rays when it interacts with atom and became excited

137
Q

What is the energy level for incident xray for coherent scattering?

A

low enegry (< 10keV)

138
Q

What does it mean to say no ionization happened ?

A

incident photons are unable to remove orbital electrons from their shell due to its low-energy level

139
Q

Effect of coherent scattering?

A

slightly contribute to pt DOSE

create image noise

140
Q

What are produced in Compton scattering interaction? and How

A
  1. ejected electrons
  2. scatter photons

incident photon interacts with the electrons in the outer-shell causing ionization. As a result, an electron is ejected with the energy equals to its BE and KE that leaves the atom. This is the secondary electron. Scattered photon is also ejected and changed direction which get absorbed photoelectrically

141
Q

compton scattering energy level

A

30-40

142
Q

Compton scattering is the greatest hazard to whom ?

A

radiation workers

143
Q

who discovered photoelectric effect

A

albert einstein

144
Q

when does photoelectric occur

A

energy of incident photon is equal to or slightly higher than binding energy of inner shell

145
Q

What happened to incident photon in Photoelectric

A

totally absorbed by the atom when trying to remove an electron

146
Q

What is produced in photoelectric interaction

A

photoelectron

147
Q

What is the equation represent the energy transfer of incident photon for Photoelectric & Compton

A

Ei = Eb + Eke
Ei = Es + (Eb + Eke)

148
Q

how to decrease photoelectric effect

pro?

A

high kVp –> by hardening beam

lower radiation dose

149
Q

compton scattering ____ proportional to kVp
photoelectric effect ____ proportional to kVp

A

directly
inversely

150
Q

What happened to incident photon in Pair Production

A

disappear after interact with nucleus of atom

151
Q

What happened to the energy of incident photon in Pair production

A

transformed into negatron & positron

152
Q

What does negatron do
What does position do

A

lose KE by exciting & ionizing atoms in its path

annihilate electron to result in 2 photons (0.511 meV each)

153
Q

Which modality do we use annihilation

A

PET

154
Q

Which types of interaction are used for radiation therapy

A

PP
photodisintegration

155
Q

how does energy transfer in photodisintegration

A

high energy photon collides with nucleus of atom which directly absorbs all the energy of photon

156
Q

What are produced when incident photon interact with nucleus in photodisintegration

A

neutron
nuclear fragment by nucleus

157
Q

what is heterogeneous

A

xray beams with various energies

158
Q

xray emission spectrum

A

the collective of all different energies of xrays
aka the different potential energy in single beam

159
Q

90% of primary beams is from____

A

Brems interactions because it can be created at any energy level

160
Q

Discrete xray spectrum produced by_____

A

characteristics X-ray

161
Q

Why does the energy of characteristic xray produced is different

A

due to the difference in BE of electrons for every element

162
Q

what cause fluctuation when xray output is above K shell peak

A

characteristic peak

163
Q

Discrete xray spectrum produced by _____
Continuous xray spectrum produced by ____
Emission xray spectrum produced by _____

A

characteristic
brems
both

164
Q

What 6 factors affect the spectrum

A

mA, time
kVp
target
generator
distance
filtration

165
Q

How does mA -tube current affect spectrum

A

change amplitude of emission graph

166
Q

How does kVp -tube potential affect spectrum

A

change in # of higher-energy photon + amplitude

167
Q

How does TARGET affect spectrum

A

atomic number of target affect both QUALITY & QUANTITY of xrays

168
Q

How does GENERATOR affect spectrum

A

generator efficiency increases = increases Xray beam intensity
Voltage ripple = decrease ma & kVp

169
Q

How does DISTANCE affect spectrum

A

farther = xray photons decreases in each square cm of beam = decrease exposure

170
Q

How does FILTRATION affect spectrum

A

thicker filter = higher atomic # = decrease ma & kVp

171
Q

What is HVL is used for

A

measure quality (kVp) of Xray

172
Q

typical HVL

A

3-5 mm Al

173
Q

how does kvp relate to HVL

A

more kvp = more intensity = more HVL

174
Q

Attennuation

A

reduction in xray intensity occurring from absorption and scattering

175
Q

4 effects of filtration

A

decreases mAs (intensity) of beam
increases kVp (average photon energy)
lower pt dose
image brightness

176
Q

Purpose of filtration

A

harden xray beam to remove low-energy photons
produce highest quality (penetrating) xray possible

177
Q

Why do we need to harden the beams

A

lower pt dose

178
Q

What is the standard material for filtering material

A

Aluminum

179
Q

3 types of filtration

A

inherent
added
compensating

180
Q

Difference in 3 types of filtration

A

inherent: glass/metal enclosure
added: thin sheet of Al between protective xray tube housing (window) and beam collimator
compensating: additional filter added to compensate differences in subject radiopacity
between collimator and patient

181
Q

Purpose of collimator

A

decrease pt dose
increase image resolution

182
Q

total filteration

A

inherent + added filtration
at least 2.5mm Al equivalent

183
Q

Differential absorption and attenuation of xray beam depend on 3 factors

A
  1. atomic #
  2. mass density
  3. xray energy
184
Q

what are 2 interactions have significant impact on xray image

A

PE & Compton

185
Q

___ atomic number = ____ attenuation
why

A

increase
increase
higher atomic number = more atoms to interact with

186
Q

___ mass density = ____ attenuation
why

A

decrease
decrease
less atoms to interact with

187
Q

___ xray energy = ____ attenuation
why

A

increase
decrease
more push power = less interactions

188
Q

to see grayscale effect

A

more photoelectric affect + less scatter & noise

189
Q

types of cell dysfunctions

A

repaired
altered
dead

190
Q

For a certain body part, why should we have a good technique

A

too much kVp = push hard = less interaction w atom= nothing reach IR = black/w image

increase kVp =

190
Q

For a certain body part, why should we have a good technique

A

too high kVp = push hard = less interaction w atom= nothing reach IR = black/w image
increase kVp = decrease PE = good for pt dose = increase scatter
==> just right kVp

191
Q

what is the most dangerous cellular dysfunction
why?

A

altered
given long exposures –> less immunity = less likely to repair –> risk of cancer

192
Q

what can occur with dead cellular dysfunction

A

risk of organ failure because of apoptosis

193
Q

what does EXPOSURE measure? unit?

A

radiation intensity in the air.

roentgen

194
Q

what does DOSE measure? UNIT?

A

radiation absorbed from radiation exposure

rad

195
Q

what is exposure used for

A

calculates entrance skin exposure

196
Q

what is dose used for

A

estimates irradiation of patients

197
Q

What is ESE? what does it measure?

A

entrance skin exposure
skin dose of radiation exposure as beam enters

198
Q

where is ESE calculated at

A

minimum SOD

CR where the beam is most intense = most radiation will hit pt

199
Q

When we dealing with patient protection, what should we assume?

A

maximum effect at entrance exposure to minimize exposure rather than internal exposure.

200
Q

3 areas of high ESE? why?

A

L-spine
pelvis & hip
abdomen

thicker body parts = more exposure = more pt dose

201
Q

7 ways to reduce patient dose

A

communication
positioning
kVp
mAs
distance
collimation
shielding

202
Q

REDUCE PT DOSE BY

A

reduce technique
collimate
no repeat

203
Q

relationship bw SID/SOD & ESE

A

inverse

204
Q

SOD

A

source to object distance
ex: anode target to patient

205
Q

SSD

A

source skin distance
ex. CR

206
Q

What are 2 target production

A

brems & characteristic

207
Q

What are produced in each types of interaction?

A
  1. coherent (excitation only, no ionization)
  2. comp scatter (secondary characteristics) - leakage & scatter
  3. PE ( cascade)
  4. PP (2 photons
  5. Photodisintegration (absorption only)

RAD 350 - Naomi (3 decks)

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