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RAD 350 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

why can’t x-rays be focused by a lens or reflected by a mirror?

A

high frequency = penetration

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2
Q

why do x-rays always carry the risk of molecular damage?

A

xrays ionizing

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3
Q

why are x-rays highly penetrating?

A

high energy and high frequency

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4
Q

why are x-rays not affect by either electric or magnetic fields?

A

neutrally charged

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5
Q

why do x-rays travel in a straight line

A

they are a photon –> like light
neutrally charged

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6
Q

what characteristic or property of x-rays allows us to produce and view them on an image receptor?

A

ability to effect change on phosphors = image

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7
Q

who discovered electromagnetic induction

A

michael faraday

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8
Q

who created vacuum tube/cathode ray

A

william crookes

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9
Q

who produced the first film

A

richard leach maddox

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10
Q

how are x-rays produced

A

accelerating electrons

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11
Q

what does a vacuum tube produce

A

cathode rays –> invisible x-rays

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12
Q

who discovered x-rays

A

Wilhelm Roentgen

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13
Q

x-rays have
_____ wavelengths and _____ frequency
this makes them ____

A

short
high
highly penetrating

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14
Q

what is an x-ray considered as?

A

a wave but has particle like characteristics

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15
Q

what is the difference between a wave and a particle

A

a wave is neutral
a particle has a charge

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16
Q

do x-rays have consistent energies or wavelengths?

A

no –> energies and wavelength cannot be controlled

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17
Q

what kind of frequency is reflective

A

low frequency

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18
Q

what are the components to an x-ray circuit

A

operating console
high-voltage generator
x-ray tube

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19
Q

what does an x-ray imaging system do

A

control intensity of electron flow to make x-ray beam
converts potential energy –> kinetic energy –> electromagnetic energy

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20
Q

why does electron intensity be high?

A

to make sure electrons are going fast and are strong enough

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21
Q

what is the potential energy in an x-ray system

A

voltage

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22
Q

what is kinetic energy in an x-ray system

A

tube current –> mAs

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23
Q

what occurs during kinetic energy conversion to electromagnetic energy

A

electrons are flowing from cathode to anode

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24
Q

what does an operating console do

A

controls tube current and voltage
controls line compensation, kVp, mA, and exposure time

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25
Q

why is it important to control tube current and voltage

A

proper radiation quantity (mAs) and quality (kVp)

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26
Q

what does radiation quantity control atomically

A

current of electrons flowing from cathode to anode

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27
Q

what is line compensation

A

measures voltage going to the system and adjusts it to 120-220V + or - 5%

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28
Q

mA and exposure time are ____ proportional

A

inversely

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29
Q

is it better to have higher mA or exposure time

A

mA –> cardinal rules –> goal: reduce time exposed

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30
Q

what components are in an operating console

A

line compensator
autotransformer
major and minor kVp selector
kVp meter
timing circuit and selector

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31
Q

What does a autotransformer do

A
  • receives energy from AC source and adjusts to what is needed –> voltage varies greatly
  • powers rest of unit
  • directly determines voltage
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32
Q

what is another name for autotransformer

A

adjustable transformer

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33
Q

what affects autotransformers

A

kVp selection –> voltage adjusted to kVp needed

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34
Q

how is voltage and kVp related

A

voltage = potential energy
kVp = kinetic energy
x-ray needs higher energy –> gets it through more voltage (PE) TRANSFORMING to kVp (KE)

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35
Q

what does AC do in a line compensator

A

????? self induction?

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36
Q

what does an autotransformer consist of?

A

solenoid –> coil of insulated wire around iron core

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37
Q

purpose of major and minor kVp selector?

A

minor changes in voltage

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38
Q

purpose of kVp meter?

A

reads voltage before exposure
aka pre-reading voltmeter

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39
Q

purpose of timing circuit

A
  • regulate x-ray exposure by turning off x-ray tube automatically
  • reduce heat and radiation dose
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40
Q

types of timing circuits

A

synchronous
electronic
mAs
automatic exposure control

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41
Q

synchronous timer

A
  • uses motor that operates at frequency of 60hz @ 60 rotations per second
  • timer is in 1/60s increments
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42
Q

cons of synchronous timers

A

cannot be used in series of exposures –> has to be redialed in after each exposure

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43
Q

purpose of automatic exposure control (AEC)

A
  • measures mAs reaching IR by using ionization chamber
  • controls time/exposure
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44
Q

purpose of ionization chambers

A

control exposure

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45
Q

how to AEC relate to ionization chambers

A

enough voltage hits chamber selected the operational amplifier terminates exposure

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46
Q

cons of using ionization chambers

A
  • large room for error
  • patient position correctly or risk overdose
  • metal absorbs = longer radiation exposure
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47
Q

purpose of AEC back up timer

A
  • used if AEC malfunction
  • protects from heat and overexposure
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48
Q

cons of AEC back up timer

A

150% over suggested time –> can still overexpose
if thick area and AEC back up kicks on it can underexpose

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49
Q

purpose of step up transformer

A

uses AC to get high voltage to supply tube with energy

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50
Q

purpose of step down filament transformer

A

supplies low current to heat up filament for thermionic emission about 12V

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51
Q

what controls step down transformer

A

mA adjustments

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52
Q

purpose of mA selector

A

controls amperage in filament circuit

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53
Q

purpose of rectifiers

A
  • changes AC to DC before releasing to xray tube
  • ensures electrons flow from cathode to anode only
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54
Q

cons of step up transformer

A

cannot be adjusted or controlled –> increases voltage by fixed amount

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55
Q

purpose of high voltage generator

A

increases output voltage from autotransformer to kVp needed

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56
Q

parts of a high voltage generator

A

high voltage step up transformer
step down filament transformer
rectifiers

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57
Q

mA meter

A

monitors xray tube current in secondary circuit

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58
Q

what is a semiconductor diode?

A

2 electrodes –> n-type and p-type
ex. rectifiers

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59
Q

half wave rectification

A
  • voltage wave is unable to dip below zero
  • no electric current
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60
Q

cons of half wave rectification

A

wastes half of power and 2x exposure time

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61
Q

half wave has ____
full wave has _____

A

zero, one or two diodes
4 diodes

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62
Q

pros of full wave rectification

A

uses less mAs

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63
Q

what occurs during full wave rectification

A

negative half-cycle is reversed so anode is positive

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64
Q

cons of single phase power

A

low energy
low penetrability
little diagnostic value
100% ripple

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65
Q

single vs three phase

A

pulsating
multiple waves and constant high voltage

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66
Q

pros of three phase power

A

voltage never drops to zero during exposure = constant energy
less ripples

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67
Q

what is a ripple

A

fluctuations of energy from zero to max voltage

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68
Q

what is good for ripple

A

low ripples –> output is similar to input = less fluctuations

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69
Q

purpose of high frequency generator

A

helps waveform, voltage, and reduces ripples

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70
Q

how does a high frequency generator work

A

increases the voltage frequency through AC and DC power converters

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71
Q

what are the external components of x-ray tube

A

support structure/mechanism
protective housing
glass or metal enclosure

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72
Q

how many diodes are in an x-ray tube

A

2 diodes –> + and - sides

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73
Q

what is the primary parts of xray tube

A

cathode and anode

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74
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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75
Q

why use glass?

A

high melting point to withstand heat

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76
Q

why metal?

A

maintains constant electric potential

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77
Q

why is it good to maintain a constant electrical potential

A

to accelerate emitted electrons to the anode

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78
Q

purpose of x-ray tube window

A

thin area that xray beams are emitted from

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79
Q

can beam particles leak out from the window

A

yes because xrays cannot be controlled as radiation leaks out but environment can be modified

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80
Q

purpose of protective housing

A

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

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81
Q

what is considered as a useful beam

A

xrays beams coming from window

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82
Q

oil
purpose?
located?

A

insulator for electricity
thermal cushion for heat
protective housing

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83
Q

cathode + or - ?

A

negative

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84
Q

components of cathodes

A

filament and focusing cup

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85
Q

where does thermionic emission occur

A

in filament aka step down transformer

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86
Q

what is thermionic emission

A

the filament heating up to create free electrons by boiling electrons off of the alloy

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87
Q

purpose of focusing cup

A

negatively charged to repulse and accelerate electrons within a confined space –> focuses electrons to hit focal spot

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88
Q

location of focusing cup

A

cathode

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89
Q

location of focal spot

A

anode

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90
Q

is anode + or - ?

A

positive side

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91
Q

purpose of anode

A

electrical conductor
mechanical support for target
thermal dissipater

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92
Q

how is heat produced
%?

A

when electrons hit the anode energy is released as 99% heat and 1% xray

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93
Q

types of anode?

A

stationary and rotating

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94
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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95
Q

con of rotating anode and solution

A

no vacuum or mechanical connection to turn anode
solution:
electromagnetic induction motor

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96
Q

stator?
purpose?

A

series of electromagnets
spins stem of anode = higher efficiency

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97
Q

rotor

A

shaft made of bars of copper and soft iron

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98
Q

what is the target

A

area of where electrons hit the anode from cathode
ex. tungsten

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99
Q

purpose of high frequency generator

A

improve waveform and voltage
reduces ripple

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100
Q

how does high frequency generator improve voltage

A

uses AC and DC converters to alter 60hz to 25000hz

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101
Q

what are the primary parts to the xray tube

A

anode and cathode

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102
Q

what are the cathode and anode considered as

A

a type of diode –> + and -

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103
Q

what the are the external components of the xray tube

A

support structure
protective housing
glass or metal enclosure

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104
Q

why do we use a glass enclosure

A

pyrex glass can withstand high heat

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105
Q

why do we use a vacuum tube

A

tightly packs electrons to be more efficient xray production = longer tube life

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106
Q

why is the glass enclosure mixed with metal?

A

to maintain a constant electric potential = longer tube life

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107
Q

what is within the glass enclosure

A

xray tube window

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108
Q

purpose of xray tube window

A

thin area that allows useful beams to be emitted

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109
Q

what does an xray tube contains

A

2 electrodes

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110
Q

purpose of protective housing

A

reduces leakage of secondary radiation
protects against electric shock
mechanical support
protects tube

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111
Q

direction of xray movement

A

everywhere –> radiates

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112
Q

how does the protective housing protect against electrical shock

A

oil acts as insulator and thermal cushion for heat

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113
Q

cathode is + or -?

A

negative side of xray tube

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114
Q

components of cathode

A

filament and focusing cup

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115
Q

purpose of focusing cup

A

confines electron beam to small area of anode

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116
Q

how does the focusing cup work

A

it is negatively charged which repulses electrons to help accelerate and concentrate them to hit the focal spot on the anode

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117
Q

what is thermionic emission

A

when the filament heats up creating free electrons by boiling off electrons from the alloy

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118
Q

purpose of filament

A

coil of wire used for thermionic emission

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119
Q

is anode + or -?

A

positive side of xray tube

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120
Q

purpose of anode

A

electrical conductor
mechanical support for target
thermal dissipater

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121
Q

what is considered the target

A

tungsten

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122
Q

how is heat created

A

when electrons hit the anode

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123
Q

types of anodes

A

rotating
stationary

124
Q

rotating vs stationary

A

rotating: high intensity xray beams in short time –> 500x more area
stationary: doesn’t produce enough energy to penetrate thick tissues

125
Q

pros of rotating

A

500x more area = 500x more xrays

126
Q

con of rotating
solution?

A

no mechanical connection to outside to spin anode
solution: electromagnetic induction motor

127
Q

components of anode

A

stator
rotor

128
Q

purpose of stator

A

series of electromagnets to spin anode = higher efficiency

129
Q

rotor

A

shaft made of bars of copper and soft iron

130
Q

what is a target

A

area of the anode that gets hit by electrons flowing from the cathode

131
Q

what is the target made out of and why?

A

tungsten in the copper anode
why? high melting point = more electrons can hit

132
Q

pros of tungsten

A

high atomic number = high efficiency for xray
high thermal conductivity
efficient heat dissipator
withstand high tube current without pitting or bubbling

133
Q

what does pitting affect

A

decreases in imaging quality

134
Q

where does pitting occur

A

focal spot

135
Q

what is a focal spot

A

area of target –> electrons hit

136
Q

what produces fine image details

A

small focal spot = better spatial resolution
good for thin tissue

137
Q

cons of small focal spot

A

high heat concentration –> less anode surface area used

138
Q

pros and cons of large focal spots

A

Pros:
good heat dissipator
thick body parts
short exposure time
con:
large effective spot

139
Q

what is effective focal spot

A

area projected onto patient

140
Q

what is actual focal spot

A

physical area on the anode

141
Q

goal of line focus principle

A

create small effective focal spot to increase image sharpness

142
Q

how do we create a small effective focal spot

A

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

143
Q

how does angle affect effective focal spot

A

angle decreases the width of the effective focal spot without altering the actual focal spot

144
Q

line focus principle is good for what?

A

to get larger heating area and a smaller effective focal spot by adding an angle

145
Q

cons of small anode angle

A

small effective focal spot
limits size of useable field
anode heel effect

146
Q

reasons for xray tube failures

A

heat
having anode at high heat for long time periods
filament

147
Q

why does the filament need low current

A

high mAs can vaporize the filament

148
Q

what % does a xray tube produce

A

1% and 99% heat

149
Q

methods to dissipate heat

A

radiation
conduction
convection

150
Q

radiation

A

transfer heat by emission of infrared radiation

151
Q

conduction

A

transfer energy from one object to another
ex. oil, glass or other materials

152
Q

convection

A

transfer heat by movement
ex. spinning of anode

153
Q

anode heel effect

A

the intensity on the cathode side is higher than anode side

154
Q

why do we need a low current for a step down transformer

A

so we can get a low voltage since voltage controls the damage to the tube

155
Q

why is the intensity higher on the cathode side

A

due to the angled anode the beams close towards direction of the cathode has less material to pass through to exit the anode

156
Q

what effect does a larger anode angle have on anode heel effect

A

less effect

157
Q

what affect does a smaller anode angle have on anode heel effect

A

greater effect

158
Q

radiographic rating chart

A

lists safe and unsafe techniques for xray tube operation

159
Q

anode cooling chart

A

thermal capacity for anode and time it takes for cool down

160
Q

housing cooling chart

A

thermal capacity for housing and time it takes for cool down

161
Q

primary function of xray tube

A

accelerate electrons from cathode to anode

162
Q

how do we accelerate electrons

A

increase kVp

163
Q

what occurs by increasing the kVp

A

intensity of mAs and energy of xray beam is increased
AKA quality and quantity

164
Q

projectile electrons?

A

high speed electrons moving from cathode to anode

165
Q

xray tube current

A

electrons moving from cathode to anode
mA –> amp

166
Q

when an electron’s velocity is at zero what occurs

A

electrons are boiling off the filament

167
Q

when a projectile electron interacts with the target what is produced

A

thermal energy
electromagnetic energy (infrared radiation)
xray

168
Q

location of projectile electrons?

A

focusing cup

169
Q

what energy is converted during an interaction from a projectile electron

A

kinetic energy

170
Q

excitation

A

charged particle transfers all or some of energy to orbital electron temporarily raising to higher energy shell

171
Q

what is produced during excitation

A

heat

172
Q

when does ionization occur

A

enough energy transferred to overcome binding energy of orbital electrons to eject electron from atom

173
Q

what determines ionization

A

speed of electron = strength

174
Q

anode heat is mainly what?

A

excitation

175
Q

what law is applied when heat is generated

A

law of energy conservation –> the kinetic energy from electron has to go somewhere

176
Q

what controls heat

A

tube current (mA) and kVp
directly proportional

177
Q

how do we increase the efficiency of xrays

A

increase kVp

178
Q

why not always high kVp for better images

A

HEAT BAD FOR TUBE

179
Q

bremsstrahulung radiation

A

an incident electron slows down through interaction from force field of nucleus
no physical interactions

180
Q

what happens to the electron’s energy?

A

kinetic energy turns into xrays

181
Q

what dictates how much energy the xray photon will have

A

the greater deviation of the electron = more xray photon energy

182
Q

bremsstrahulung energy reaction ratio

A

xray photon exactly the difference between entering and exiting kinetic energy

183
Q

where is a bremsstrahulung xray produced

A

at any cathode

184
Q

how many interactions can be made from a single bremsstrahulung electron

A

multiple until loss of energy

185
Q

what happens once a bremsstrahulung electron loses energy

A

it becomes part of the current flow

186
Q

what determines the characteristic radiation energy level needed

A

the target material

187
Q

what is characteristic radiation

A

when an incident electron interacts with an inner shell (k) electron with enough energy to knock electron out of orbit

188
Q

what is the typically energy needed for radiation to be characteristics

A

69kVp +

189
Q

what would raise the energy level needed for characteristic radiation

A

if binding energy of electron is higher
electron closer together = higher binding energy

190
Q

what happens to the projectile electron from the characteristic interaction

A

it goes to a slightly different direction from incident electron

191
Q

electron cascade

A

outer shell electron falls in to fill hole left by projectile electron and continues on until no more outer shell electrons or pulls in electron from surroundings

192
Q

what is produced from electron cascade

A

xray photon from lower energy state (energy difference) between the 2 shells

193
Q

characteristic energy reaction ratio

A

exact difference between binding energy between inner and outer shells from where electron dropped

194
Q

why with k shell first?

A

outer shell electron’s energy is too low for diagnostic purposes

195
Q

what increases effective energy of characteristic xray

A

increasing atomic number of target element

196
Q

as cascade occurs what are the energy levels

A

inner shell highest
outer shell lowest

197
Q

what is heterogeneous

A

xray beams with various energies

198
Q

why are xray beams heterogeneous

A

energy levels are random from nucleus deviation (bend)
also varying frequencies and wavelengths

199
Q

xray emission spectrum

A

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

200
Q

what makes up the primary beam spectrum

A

both brems and characteristic

201
Q

kvp range for brems and percentage of occurrence

A

80-100kVp
80-90%

202
Q

relation of kVp and keV

A

keV = 30-40% of kVp
more kvp = more kev but not equal

203
Q

what is discrete xray spectrum

A

a graph-able spectrum using characteristic xrays
shows different electron binding energies for differing elements

204
Q

why do we use characteristic xrays for the discrete xray spectrum graph

A

specific energies used for target = predictable

205
Q

characteristic peak

A

peak = k shell emissions
varies if xray output is above kshell peak

206
Q

continuous xray spectrum

A

uses brems radiation
measures any produced cathode electron energy
from peak to 0

207
Q

what affects the spectrum

A

mA = amplitude
kVp = amplitude/energy of photon
generator = intensity of beam, phasing efficiency, and average photon energy
atomic number = kvp and ma –> characteristic made?
voltage ripple = decreases ma and kvp
filtration = decrease in ma and kvp

208
Q

half value layer

A

the thickness of absorbing material that attenuation half of xray
measures quality of xray and sets radiation safety

209
Q

attenuation

A

reduction in xray intensity occurring from absorption and scattering

210
Q

what is quality of xrays measured by

A

half value layer

211
Q

typical half value layer?

A

HVL of 3-5 mm Al

212
Q

how does kvp relate to HVL

A

more kvp = more intensity = more HVL

213
Q

filtration

A

removes low energy brems from beam –> not useful diagnostic by using absorbing materials in primary beam

214
Q

effects of filtering

A

decreases intensity of beam
increases average photon energy
lowers radiation dose
control photon energy
density –> mA / gray scales

215
Q

name layers of xray filters

A

1st glass envelope
2nd compensating filter (Al)

216
Q

hardening of beam

A

filters beam of soft photons for highest quality/intensity

217
Q

aluminium equivalency

A

many materials like lead shielding is not 100% lead made out of other materials

218
Q

why do we use wedges and trough filters

A

visualizes fine details by lowering xray beams to certain parts of body –> decreases darkness (air)

219
Q

inherent filter

A

glass or metal enclosure of xray beam

220
Q

added filter

A

thin sheet of Al between protective xray tube housing (window) and beam collimator

221
Q

compensating filter

A

additional filter added to compensate differences in subject radiopacity
between collimator and patient

222
Q

total filteration

A

total sum of inherent and added filtration
at least 2.5mm Al equivalent

223
Q

how to compensate for decrease in xray intensity after filtering

A

increase kvp

224
Q

what occurs during ionization

A

addition or removal of an electron

225
Q

what are the effects of ionizing radiation

A

ability to ionize atoms
changes the charges and force fields of atom

226
Q

can any form of energy ionize?

A

yes

227
Q

interactions of xrays

A

attenuation
some energy transfers and scatter
direct transmission

228
Q

direct transmission

A

xray can pass through unaffected –> pushes straight through to IR

229
Q

when does a photon interact with biological matter

A

random occurrence –> cannot predict single photon interaction reaction

230
Q

is the kVp ratio interact with cells equal?

A

no –> random interaction

231
Q

how can we predict the probability of photon interaction with matter

A

radiation decay –> large numbers of photons rather than single photon

232
Q

when does an electromagnetic radiation interact with matter?

A

matches size of wavelength of the radiation

233
Q

what does low energy xray interact with?
type of interaction?

A

whole atoms
excitation

234
Q

what does moderate energy xray interact with?

A

electrons

235
Q

what does high energy xray interact with?

A

nuclei

236
Q

what is the wavelength of higher energy xray

A

shorter wavelength

237
Q

what are interactions dependent on

A

kvp
body mass
SID
energy of photons
atomic number

238
Q

types of interactions

A

classical (coherent scattering)
photoelectric interaction
compton interaction
pair production
photodisintegration

239
Q

does the photons always interact with atoms?

A

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

240
Q

Coherent scattering energy levels

A

below 10 keV

241
Q

coherent scattering alternate name

A

thompson or classical

242
Q

what occurs during coherent scattering

A

excites target atom –> movement = energy emitted –> scattered xray produced

243
Q

output of coherent scattering

A

scattered xray wavelength = wavelength of incident xray
direction changes without energy change
image noise

244
Q

does energy transfer for coherent?
ionizing?

A

no energy transfer
no ionization

245
Q

who discovered photoelectric effect

A

albert einstein

246
Q

when does photoelectric occur

A

energy of incident photon is slightly higher than binding energy of k or L shell

247
Q

what happens to xray in photoelectric

A

entire xray is absorbed when incident xray removes an electron

248
Q

how does energy transfer in photoelectric

A

the inner shell electron absorbed all energy –> ejecting a photoelectron

249
Q

traits of photoelectron

A

negative charge
can ionize atoms
low energy

250
Q

energy ratio of photoelectron

A

kinetic energy = difference between energy of incident xray and binding energy of electron

251
Q

after effects of photoelectric effect

A

characteristic xrays –> low energy and locally absorbed

252
Q

probability of photoelectric

A

directly dependent on atomic number of irradiated tissue
indirectly with photon energy

253
Q

how to decrease photoelectric effect
pro?

A

high kVp –> by hardening beam
lower radiation dose

254
Q

compton scattering energy level

A

30-40keV

255
Q

when does compton scattering occur

A

incident xray interacts with outer shell electron and ejects electron= ionizing atom

256
Q

energy ratio of electron in compton

A

ejected electron = binding energy and kinetic energy that leaves the atom

257
Q

what happens to ejected electron in compton

A

ejected electron = scattered xray –> goes to interact with another electron –> gets absorbed photoelectrically

258
Q

energy of scattered xray in compton

A

2/3 of original energy

259
Q

what makes the most molecular damage

A

scattering

260
Q

what is the greatest interaction for diagnostic imaging

A

compton scattering

261
Q

compton scattering ______ as xray energy increases
____ with lower energy xrays

A

increases with kVp increase
decreases with kVp decrease

262
Q

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

A

directly
indirectly

263
Q

cons of compton scattering

A

reduces image contrast = useless

264
Q

energy level pair production
probability of occurrence

A

1.02MeV
higher probability at 10 MeV +

265
Q

if you have alot of energy ex. MeV….. what do you also have?

A

high energy photons

266
Q

what occurs in pair production

A

incident xray photon strongly interacts with nucleus of atom of irradiated tissue and disappears

267
Q

what happens to energy in pair production

A

energy of photon transforms to 2 new particles
negatron (reg electron)
positron (positive charged electron)

268
Q

what does negatron do

A

loses kinetic energy through excitation and ionizing atoms in path

269
Q

what does positron do

A

antimatter –> ANNIHILATES nearby free electron = 2 photons created at 0.511MeV each

270
Q

why is annihilation good?

A

used in positron emission tomography PET

271
Q

what is used for radiation therapy

A

pair production
photodisintegration

272
Q

photodisintegration energy level

A

more than 10MeV –> very high energy

273
Q

how does energy transfer in photodisintegration

A

high energy photon collides with nucleus of atom and directly absorbs all the energy of photon
then absorption by patient = excitation –> no ionization

274
Q

what occurs in photodisintegration

A

energy transfer too high = unstable atom –> nucleus blows up scattering nucleus pieces
nucleus pieces are radioactive

275
Q

how is radiation intensity reduced

A

absorption through tissue and scattering

276
Q

what does attenuation measure

A

how much is absorbed
% of xray beam left

277
Q

xray attenuation relationship

A

exponentially –> can absorb forever

278
Q

how can xrays be stopped

A

lead ABSORBS the xray by fractional amounts

279
Q

differential absorption

A

different materials absorb at different rates

280
Q

dependents of differential absorption

A

atomic number
mass density
xray energy

281
Q

___ atomic number = ____ attenuation
why

A

increase
increase
higher atomic number = more atoms to interact with

282
Q

___ mass density = ____ attenuation
why

A

decrease
decrease
less atoms to interact with

283
Q

___ xray energy = ____ attenuation
why

A

increase
decrease
more push power = less interactions

284
Q

2 important interactions for xray image and why

A

photoelectric –> affects density
compton scattering –> creates noise

285
Q

kVp affect on xray image

A

high kVp = less grays

286
Q

types of cell dysfunctions

A

repaired
altered
dead

287
Q

what is the most dangerous cellular dysfunction
why?

A

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

288
Q

what can occur with dead cellular dysfunction

A

risk of organ failure because of apoptosis

289
Q

what does exposure measure

A

radiation intensity in the air

290
Q

what is exposure measured in

A

roentgen

291
Q

what does dose measure

A

radiation absorbed from radiation exposure

292
Q

what is dose measured in

A

rad

293
Q

what is exposure used for

A

calculates entrance skin exposure

294
Q

what is dose used for

A

estimates irradiation of patients

295
Q

what does entrance skin exposure measure

A

skin dose of radiation exposure as beam enters
looks at CR area

296
Q

where is ESE calculated at

A

minimum SOD

297
Q

areas of high ESE

A

L-spine
pelvis
hip
abdomen
high thickness = high intensity

298
Q

priority for patient dose

A

avoid repeats > all other methods to reduce patient dose

299
Q

for radiosensitive tissues what is a good position

A

ex. breast –> PA
place sensitive tissue furthest away from entrance exposure

300
Q

why are immobilizations good

A

eliminate motion
decrease tissue density –> compression

301
Q

how to reduce patient dose with kVp

A

increase kVp and decrease mAs
too low mAs = decrease sharpeness
too high kVp = high dose
BALANCE

302
Q

SID/SOD increase = ESE ____
why

A

decreases
more distance = less dose

303
Q

why not have max SOD/SID?

A

too far = decrease in xray beam intensity

304
Q

radiosensitive organs (3)

A

lens of eye
breast
reproductive organs

305
Q

SOD

A

source object distance
anode target to patient

306
Q

SSD

A

source skin distance
ex. CR

RAD 350 (5 decks)

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