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RAD 350 > Test 3 > Flashcards

Test 3 Flashcards

1
Q

factors that affect xray photon emissions (5)

A

tube housing
target material
filteration
voltage waveform
prime factors

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2
Q

what is a prime factor

A

factors that directly affect xray quality/quantity of xray emissions

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3
Q

list prime factors (3)

A

mAs
kVp
distance

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4
Q

how is prime factors controlled

A

direct control by radiographer

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5
Q

what does xray quantity measure

A

number of xray photons in useful beam

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6
Q

what is associated with xray quantity (AKAs)

A

xray output
intensity
exposure

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7
Q

what affects xray quantity and how

A

mAs –> less mAs = less photons in beam
kVp —> more = increase by 4 factors
distance –> more distance less photons in beam
filtration –> hardens beam = less photons in beam

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8
Q

how is xray quantity is measured (2)

A

mGya –> milligray in air
milliroentgen (mR)

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9
Q

what does mGya measure

A

number of ion pairs produced in air by quantity of xrays

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10
Q

if mAs is doubled what is doubled

A

quantity is doubled

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11
Q

if kVp is doubled = quantity _____

A

increased by factor of 4

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12
Q

what does xray quality measure

A

penetrating ability of xray beam

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13
Q

what is penetrability

A

distance an xray beam travels in matter

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14
Q

what can travel farther away (xray beam)

A

high energy xrays

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15
Q

what affects xray quality and why?

A

kilovoltage –> gives energy to penetrate
filteration –> takes away energy of photons

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16
Q

what does NOT affect radiation quality and why

A

distance
mAs
nothing to deal with energy of beam

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17
Q

importance of penetrability for xray

A

ability to penetrate deeper in tissues

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18
Q

high energy xrays is ____,___

A

high quality, hard

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19
Q

low energy xrays has ____,___

A

low quality, soft

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20
Q

difference between high and low energy xrays

A

high energy –> penetrates tissues deeply

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21
Q

what affects penetrability and give example

A

atomic number of tissue irradiated
low atomic number = more penetrability
high = less

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22
Q

what thickness of soft tissue to reduce xray intensity by half?

A

3-6 cm

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23
Q

how is xray quantity represented

A

HVL
half value layer

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24
Q

what is HVL

A

thickness of absorbing material to reduce xray intensity by half of original value

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25
Q

HVL of diagnostic xray

A

3-6 cm

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26
Q

what does milliamperage measure and direction

A

xray tube current
number of electrons in tube from cathode to anode

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27
Q

if mA increases = ______ (3)

A

increases for ALL
number of electrons
mass density of patient
exposure time

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28
Q

directly or inversely proportional?
mA and number of electrons
mA and exposure time
mA and density (mass)

A

directly for ALL

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29
Q

mA
s
stands for what

A

mA = tube current
s = exposure time

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30
Q

what is the primary control for image receptor exposure

A

mAs

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31
Q

how is image receptor exposure measured by

A

exposure value
ex. I#, E#, EI#, S#

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32
Q

how do you know if image is underexposed or overexposed

A

under –> value below
over –> value

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33
Q

how do you know if image is underexposed or overexposed

A

under –> value below
over –> value over

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34
Q

low mAs = ____
high mAs = ____

A

underexposed & grainy
overexposed

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35
Q

kVp controls what? (2)

A

quantity and quality of xray beam
signal to digital detector

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36
Q

increase kVp = increase ____

A

speed and energy of electrons

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37
Q

optimal range for kVp

A

60-110

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38
Q

proper balance for patient dose

A

higher kVp and lower mAs

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39
Q

how does kVp affect quality

A

more energy = greater penetrability

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40
Q

how does kVp affect quantity

A

increase kVp = more interactions at target

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41
Q

what is subject contrast resolution

A

visibility of details of clear white through various shades of gray/black
ex. lungs

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42
Q

what affects subject contrast resolution

A

less kVp = less penetrability = less signals = less gray tones

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43
Q

how can image contrast be fixed

A

computer processing

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44
Q

what does distance affect

A

intensity of xrays
IR exposure

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45
Q

_____ distance =
_____ intensity
_____ IR exposure

A

increase = decrease & decrease

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46
Q

compensator for distance?

A

mAs

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47
Q

inverse square law

A

intensity of radiation at a given distance from point source has a inverse relationship

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48
Q

what does inverse square law calculate

A

relationship between distance and xray intensity

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49
Q

what measures xray intensity

A

mR

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50
Q

what explains distance’s relationship to intensity and IR exposure

A

exposure maintenance formula

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51
Q

if mAs is increased –> distance is ____

A

decreased by the square of the change

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52
Q

what is the exposure maintenance formula used for

A

to compensate effects for changes in distance will have on IR exposure on image

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53
Q

how is density and contrast primarily controlled

A

post processing parameters

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54
Q

if changes applied to mAs, kVp, and distance but no visual effects –> how does that occur

A

exposure latitude of digital imaging

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55
Q

what are the factors for digital image quality

A

mAs
kVp
distance

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56
Q

exposure latitude controls what?

A

brightness / contrast

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57
Q

When x-rays strike matter what occurs

A

attenuate
direct transmission –> passes through unaffected
scatter

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58
Q

Differential absorption is

A

difference between the x-ray photons that are absorbed photoelectrically and those that penetrate the body

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59
Q

why does differential absorption occur

A

energy levels in the photons and anatomic parts vary = different absorption of primary beam at varying degrees

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60
Q

what does differential absorption control/create

A

contrast –> varying grays
creates image formation and darken areas

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61
Q

what % of xray actually create the image?

A

0.5%

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62
Q

how do we increase differential absorption? why?

A

decrease kVp = more mAs = more photons to interact with to have varying grays

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63
Q

what is attenuation

A

how much photons in beam have been reduced after passing through given thickness of material

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64
Q

Differential absorption and attenuation of the x-ray beam depend on:

A

The atomic number of the atoms in tissue
The mass density of tissue
The x-ray energy

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65
Q

attenuation is greater with _____

A

thicker patients –> body mass

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66
Q

attenuation reduces xrays how?

A

in % based off EACH thickness of material

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67
Q

Quality and quantity of photons should be ___________ with ____________ body part thickness

A

increasing, increasing

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68
Q

high atomic number = _____ attenuation

A

greater

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69
Q

____ density = ____ attenuation

A

lower density
lower attenuation

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70
Q

4 major substances for variations in x-ray absorption?

A

air
fat
muscle
bone

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71
Q

what controls the contrast of an image (variations in the shades of gray)

A

DIFFERENTIAL ABSORPTION

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72
Q

what substance has:
high actual atomic number
low effective atomic number
low tissue density

A

air

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73
Q

what substance absorbs the least amount of photons and why?

A

air
less packed atoms (density) = less interactions = more photons reaching IR (direct transmission)

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74
Q

what does it mean if more photons reach the IR

A

IR gets a greater exposure

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75
Q

what substance has:
lowest effective atomic number
lower tissue density than muscle

A

fat

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76
Q

what substance has a tissue density similar to water

A

fat

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77
Q

why can we see a kidney in a KUB

A

the organ is surround by fat –> increased tissue density = visibility

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78
Q

what substance has:
high atomic number
high effective atomic number
higher density than fat

A

muscle

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79
Q

list substances on tissue density from lowest to highest

A

air –> fat –> muscle –> bone

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80
Q

list substance on atomic number from low to high

A

fat –> muscle –> bone –> air

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81
Q

what substance is the greatest attenuator

A

bone

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82
Q

why can Psoas muscles on a KUB be seen

A

greater amount of absorption

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83
Q

why do bones have a high atomic number

A

calcium –> very dense

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84
Q

what substance has:
greatest tissue density
high atomic number
high effective atomic number

A

bone

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85
Q

what substance has the highest absorption rate

A

bone

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86
Q

which substance allows for the least amount of photons to reach the IR?
highest amount?

A

bone
air

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87
Q

why is direct transmission important for images

A

provides image that represents the anatomic part –> passes through anatomic structures = darker areas

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88
Q

what does scatter xray produce (4)

A

noise
lower image contrast
less image visibility
extra patient dose

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89
Q

scatter xray output

A

ionization and loss of energy

90
Q

why is scatter xray dangerous

A

loss of energy = ion –> energy absorbs into body = molecular damage

91
Q

how is scatter created

A

compton interaction

92
Q

factors that affect scatter

A

kVp

x-ray field size

body part thickness –> mass tissue density

93
Q

scatter increases with which factors

A

ALL FACTORS –> kVp, field size, mass tissue density

94
Q

____ kVp = ____ compton = ____ photoelectric

A

increase
increase
decrease

95
Q

____ xray energy = _____ scatter

A

increase
increase

96
Q

thicker patients = ____ kVp

A

increases

97
Q

kVp affects what? Increase kVP = ?

A

image contrast is reduced

98
Q

larger field size = ?

A

increased scatter and patient dose

99
Q

why would a larger field size increase dose?

A

mAs would have to be increased
more body area exposed

100
Q

what factor would have a higher photoelectric effect and less compton? ex?

A

higher atomic number
ex. bone absorption (photoelectric) = less scatter

101
Q

if thickness of tissue increases what occurs?

A

increase of :
scatter
field size
angle of scatter

102
Q

30cm thick exposure would produce how much scatter? ex?

A

100%
abdomen

103
Q

what is remnant radiation

A

remaining xray beam after being attenuated by patient

104
Q

Remnant radiation is composed of?

A

transmitted and scatter radiation

105
Q

remnant radiation is also known as

A

remnant beam or exiting radiation

106
Q

approximately ______of the x-rays actually create the image

A

.5%

107
Q

what technique would produce the least amount of scatter?

A

a technique involving a high kVp and low mAs

108
Q

scatter vs diagnostic rays

A

scatter travels in divergent paths and more likely grid absorbed

109
Q

____ atomic number = ____ attenuation = ____ scatter

A

increase
increase
decrease

110
Q

part of useful beam and not

A

useful: transmitted
NOT: scatter

111
Q

methods to reduce scatter

A

restricting beam (collimating)
use grid
technique

112
Q

what is transmitted radiation

A

radiation (rays) that actually hit the IR from the primary beam

113
Q

why do we get different types of radiation

A

beam is heterogenous –> varying energy levels

114
Q

what is beam restriction dependent on

A

body part size

115
Q

beam restriction pro? why?

A

less scatter = better image
less primary photons = less patient dose/ tech dose

116
Q

___ collimation = increased _____

A

increase
spatial resolution

117
Q

collimator pro?

A

regulates primary beam field size
light source to aid positioning

118
Q

purpose of shutters

A

regulate field size –> cones in beam
bottom: reduces penumbra
upper: reduces off focus radiation

119
Q

bottom shutters affects what part of beam

A

periphery of beam

120
Q

how is a penumbra produced and effects what?

A

ratios of SOD/OID = fuzzier image (edge unsharpness)

121
Q

increased penumbra effect =

A

increase OID
decrease SOD

122
Q

decrease penumbra effect =

A

decrease OID
increase SOD

123
Q

why do we have a penumbra effect

A

x-ray emitted has dimensions (geometric)

124
Q

why do we get off focus radiation? what does it produce?

A

photons not produced at focal spot exits and hits IR = ghosting after image

125
Q

what is repeatable error penumbra or off focus radiation

A

penumbra

126
Q

rules of collimation

A

field size never larger than cassette
collimate to proper anatomic area

127
Q

positive beam limitation device (PBLD)?
PRO?

A

auto collimation to size of cassette
good: reduces overexposure

128
Q

when to use masking
when not to use masking

A

off focus radiation occurs
cropping exposure field after image taken

129
Q

what is aperture diaphragm

A

simple beam restricting device –> additional filtration
made of lead has hole in center attaches to xray tube

130
Q

aperture diaphragm pro? ex?

A

fixes field size
increases spatial resolution
decreases scatter
EX. fractures in extremities

131
Q

type of aperture diaphragm
PRO?
ex when used?

A

cone and cylinders
most effective for scatter control
dentist

132
Q

what is a grid

A

absorbs scatter before it reaches the IR

133
Q

grid pro?

A

improves contrast
reduces scatter

134
Q

who created the grid
when
issue

A

Gustav Bucky
1913
grid line superimposed anatomy

135
Q

who improved the grid
when
how

A

Hollis Potter
1920
moving grid during exposure = blurs lead grid lines

136
Q

when to use a grid
not use grid

A

body part thickness over 13 cm or 10 cm for film
kVp above 70
NO: children

137
Q

how to know when to use a grid

A

technique charts and manuals for kVp
calipers for thickness

138
Q

ASRT recommends usage of grid

A

use grid based on vendor
body parts over 10 cm

139
Q

why do we not use a grid on children
exceptions:

A

grid = increase patient dose
exception: fat ass kid –> over 12 cm

140
Q

pediatric vs adult radiosensitivity

A

pediatric 10x more

141
Q

grid constructed of

A

radiopaque strips with interspace material that is radiolucent

142
Q

radiopaque strips made of what? why?
interspace material made of what? why?

A

lead –> high atomic number = high attenuation rate
aluminum or plastic –> absorbs less photons = produces image
overall hardens beam

143
Q

grid ratio

A

height of lead strips to distance between strips

144
Q

higher grid ratio =

A

less scatter
increase grid errors –> position has to be perfect

145
Q

grid frequency

A

number of grid lines per inch or cm

146
Q

most common grid frequency

A

85-103 lines/in

147
Q

higher grid frequency =

A

thinner lead strips

148
Q

higher frequency
15:1 or 6:1

A

15:1

149
Q

contrast improvement factor measures?

A

how well a grid functions to improve contrast

150
Q

____ scatter = ____ contrast and _____ contrast improvement factor

A

increase
decrease
decrease

151
Q

grid conversion factor indicates?

A

increase of mAs needed when converting no grid to grid

152
Q

compensations if grid is used and why

A

increase mAs –> grid decreases quantity

153
Q

grid conversion factor also known as?

A

bucky factor

154
Q

____ grid ratio = ____ bucky factor

A

higher
higher

155
Q

___ kVp = ___ bucky factor

A

increase
increase

156
Q

____ grid frequency = ____ mAs

A

increase
increase

157
Q

grid motion types

A

stationary or moving

158
Q

con of stationary grid

A

grid lines may be seen

159
Q

rule of grids

A

CR must be perpendicular to avoid grid lines
dependent on tissue thickness

160
Q

grid types

A

parallel
focused
crosshatched

161
Q

parallel grid directions
xray tube effect

A

lead and interspace strips run parallel to each other
tube can be angled with length of grid without cut off

162
Q

focused grid direction

A

central grid strips parallel but as strips move away they become more inclined –> like central beam

163
Q

when would a focused grid be used

A

focal range is wide for low ratio grids
focal range is narrow for high ratio grids

164
Q

focused grids used for?

A

specific ranges of SID
focal distance
range

165
Q

crosshatch grid direction

A

2 linear grids perpendicular to each other

166
Q

crosshatch grid pro
con

A

best scatter clean up
no need for tube angle
CON: MOST grid errors

167
Q

when would a crosshatch grid be used

A

biplane cerebral angiography

168
Q

reasons for grid errors

A

use of focused grids
off centered tube or incorrect distance tube

169
Q

how to prevent grid error

A

proper tube/grid alignment

170
Q

why is grid error bad

A

unwanted absorption of primary radiation –> grid cut off

171
Q

what is grid cut off

A

the primary beam angled into the lead, absorbing undesirable primary radiation

172
Q

grid cut off effects

A

decrease density on periphery film

173
Q

types of grid errors (5)

A

off level
off focused
off center
upside down
moire effect

174
Q

off level occurs when?
fix?

A

when tube is angled across long axis of grid strips
FIX: grid perpendicular to CR

175
Q

off focused occurs when?

A

distance used other than specified for focal range

176
Q

off center occurs when?
effect on image?

A

CR does not hit grid at center
cutoff visible more on one side of image

177
Q

upside down occurs when?
effect on image?

A

focused grid not aligned with labeled tube side facing xray tube and IR in stationary
effect: uneven exposure

178
Q

moire effect occurs when? common with?

A

in digital systems
when grid lines are seen and scanned parallel to scan lines
common: stationary grids in mobile digital system

179
Q

alternative to using a grid
does what?

A

air gap technique
reduces scatter by creating gap

180
Q

how to use air gap technique

A

increase OID –> patient far from IR

181
Q

Pro and cons of conventional grid use

A

PRO: reduce scatter and increase contrast
CON: increase dose, stationary grid errors, and increase potential repeat

182
Q

when would a stationary grid be used

A

portable (mobile) imaging

183
Q

pro and con of digital IR

A

con: highly sensitive scatter
pro: good scatter correction with digital processing

184
Q

when to use a grid on a digital IR

A

tissue thickness greater than 13cm
extreme amounts of scatter produced

185
Q

when not to use a grid with examples
exceptions

A

aerated thorax
chest
thoracic spine
sternum
ribs above diaphragm
EXCEPT: if patient is very large

186
Q

what grid ratio do we use for digital IR

A

lower grid ratios (6:1 portable)

187
Q

types of noise

A

scatter and mottle

188
Q

how do we get mottle

A

not enough mAs to get interactions

189
Q

mottle effect on image

A

pixelated image
loses sharpness of image

190
Q

no technique compensation
what effects occur by removing grid

A

reduces probability of mottle

191
Q

what would the technique compensation be by removing the grid

A

mAs decrease by 1/2
or decrease all technique by 1/3

192
Q

can post processing feature remove scatter?

A

no just removes effects of scatter

193
Q

when was the virtual grid software created and by who?

A

2014 by Fujifilm

194
Q

virtual grid software steps

A

scatter xray estimation
grid effect calculations
granularity improvement processing

195
Q

how does scatter xray estimation work

A

estimates dose and thickness to estimate the amount of scatter will be produced

196
Q

how does grid effect calculation work

A

determines intensity of contrast correction is needed

197
Q

how does granularity improvement processing work

A

analyzes contrast-to-noise ratio to apply noise reduction algorithms

198
Q

what cannot be altered after exposure

A

grid ratio
amount of scatter

199
Q

virtual grid vs plain grid

A

virtual:
reduces dose
reduces possibility for grid errors
flexibility to compensate during exposure
reduces effects of scatter
accepts larger tissue thickness (13cm)
plain grid:
increase dose and grid errors
reduces scatter
cannot be changed after exposure
less tissue thickness (10cm)

200
Q

when would we use virtual grid software

A

knee
shoulder
c-spine –> not for swimmers
lat/oblique mandible
most pediatric procedures

201
Q

is grid the most important way to reduce patient dose? why?

A

no grid less important
most procedures can be done non grid and over 13 cm
grid ratio is less important –> lower ratios can be commonly used

202
Q

why is pathology important

A

diseases can alter body so technique needs to be altered
better patient care

203
Q

pathology is the study of what

A

study of disease process of how it affects structural and functional changes

204
Q

pathological conditions affects what

A

thickness and composition of tissues

205
Q

types of pathological conditions

A

additive and destructive

206
Q

how does additive condition affect the body

A

increases thickness
increase effective atomic number
increase tissue density

207
Q

how does additive conditions affect an image? why?

A

more attenuation = more white

208
Q

disease worsens for additive condition =

A

decrease in IR exposure

209
Q

____ technique for additive condition? why?

A

increase –> harder to penetrate tissue due to increase in thickness/atomic number/density

210
Q

if additive …. how much do we increase kVp

A

5-15% manually
or AEC system changes mAs automatically but not kVp

211
Q

how does destructive condition affects the body

A

decreases tissue thickness
decrease effective atomic number
disease density

212
Q

how does destructive conditions affect an image? why?

A

darkens image –> less attenuation so more photons go straight to IR

213
Q

disease worsens for destructive condition =

A

increase in IR exposure

214
Q

____ technique for destructive condition? why?

A

decrease because the photons go straight to IR already making image too dark

215
Q

abscess-encapsulated infection affects body how?

A

increase tissue thickness
can alter composition

216
Q

edema-swelling affects body how?

A

increases tissue thickness
can alter composition in lungs

217
Q

tumor-abnormal new growth affects body how?

A

increase tissue thickness
can alter composition in lungs and bone

218
Q

types of pathology that does not need change in technique

A

ulcers
diverticula
simple fractures

219
Q

pathology that does not need xray diagnosis

A

diabetes
anemia
meningitis

220
Q

kvp and mAs changes to accommodate pathology

A

5%-15% kVp
25%-50% mAs

221
Q

15% kVp increase = ___

A

2x exposure

222
Q

15% kVp decrease = _____

A

2x mAs to maintain exposure

RAD 350 (5 decks)

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