arrt review: image production Flashcards
1
Q
benefit and disadvantage of fixed kVp chart
A
consistent contrast, high mAs settings for larger patients/body parts
2
Q
benefit and disadvantage of variable kVp chart
A
assures penetration of the objects of interest; contrast is prone to unacceptable variations
3
Q
technical considerations for a wet plaster cast
A
doubling of exposure factors
100% increase in mAs or 8-10 increase in kVp
4
Q
technical considerations for a dry plaster cast
A
50-60% increase of mAs, 5-7 increase of kVp
5
Q
technical considerations for a fiberglass cast
A
25-30% increase of mAs, 3-4 increase in kVp
6
Q
barium sulfate contrast media requires (higher/lower) kVp techniques to ensure proper penetration of the contrast
A
higher
7
Q
IV iodine based contrast media requires (higher/lower) kVp techniques to ensure proper penetration of the contrast
A
lower; to prevent over penetration
8
Q
matrix size is dependent on _______ and _______________
A
field of view, pixel density
9
Q
increase in IR size results in a (decrease/increase) in matrix size
A
increase
10
Q
decreasing pixel size results in (increased/decreased) matrix size and (increases/decreases) spatial resolution
A
matrix size = increase
spatial resolution = increase
11
Q
decreasing pixel size (increases/decreases) visibility of small structures
A
increases
12
Q
as DEL increases, spatial resolution (increases/decreases)
A
decreases
13
Q
what is spatial resolution measured in?
A
line pairs per mm
14
Q
pixel size is measured ___________; pixel pitch is measured _______________
A
end to end, center to center
15
Q
minimum response time for AEC
A
approximately 0.001 sec
16
Q
the time it takes for an AEC system to respond and send the signal to terminate the exposure
A
minimum response time
17
Q
those factors that affect the amount of exposure reaching the radiographic image receptor
A
photographic factors
18
Q
those factors that affect the degree of divergence of x-ray beam and the information recorded on the radiographic image receptor
A
geometric factors
19
Q
two subtypes of geometric factors
A
recorded detail, distortion
20
Q
what type of anatomy do you put under the cathode end?
A
“FAT CAT”
dense anatomy under cathode end
21
Q
tube housing leakage maximum rate
A
0.88 mGy/hr at 1 m
22
Q
what is the space charge effect?
A
collection of free electrons surrounding the filament
at 1000 mA, no more electrons can be boiled off the filament
23
Q
equation to calculate heat units
A
heat units = kVp x mA x S x W
where W is the waveform factor
24
Q
waveform factor single phase
A
1
25
waveform factor 3 phase 6 pulse
1.35
26
waveform factor 3 phase 12 pulse
1.41
27
waveform factor high frequency
1.45
28
waveform factors for3 phase 6 pulse, 3 phase 12 pulse, and high frequency are sometimes averaged to ____
1.4
29
a decreased anode angle (increases/decreases) the anode heel effect
increases
30
an increased anode angle (increases/decreases) the anode heel effect
decreases
31
the anode angle and the anode heel effect are _______ related
inversely
32
which of the following anode angles is steep/small?
6 or 20
6
33
the anode heel effect increases with (increased/decreased) anode angle, (increased/decreased) SID, and (increased/decreased) field size
decreased anode angle
decreased SID
increased field size
34
a small anode angle with produce a (very narrow/very large) effective focal spot
very narrow
35
what type of anode angle do you want for high spatial resolution?
decreased (small) anode angle
36
what is larger, the actual focal spot or the effective focal spot?
actual is always larger than effective
37
the autotransformer works on what type of induction?
self induction
38
The step up & step down transformers work on what type of induction?
mutual induction
39
in a transformer, the side with more turns = where the voltage is (lower/higher)
higher
40
What is the role of the rectifier?
makes AC current into DC current (one way street for electrons)
rectifiers are also called "solid state diodes"
41
step up transformers
(increase/decrease) voltage
(increase/decrease) amperage
increase voltage, decrease amperage
42
step down transformers
(increase/decrease) voltage
(increase/decrease) amperage
decrease voltage, increase amperage
43
3 phase 6 pulse rectification has what voltage ripple?
14%
44
3 phase 12 pulse rectification has what voltage ripple?
4%
45
high frequency rectification has what voltage ripple?
~1%
46
mA station selected by the radiographer determines the amount of _______________ sent to the (primary/secondary) side of the filament transformer
current and voltage, primary
47
a rheostat operates as a ____________ within the filament circuit. by varying ________ in a circuit, ____ can be controlled
variable resistor, resistance, current
48
small focal spots usually range in size from ______; large focal spots usually range in size from _____
0.1 to 1.0 mm
0.3 to 2.0 mm
49
What type of exams would you use a “stationary” grid? Will you see grid lines?
portable or tabletop; you can see grid lines
50
What type of exams would you use an "oscillating” grid?
within bucky system; no grid lines
51
How will the following AEC
adjustments change the seconds during exposure? (Increase or decrease of seconds)
Increase kVp
Increase mA
Decrease mA
Increase Density setting by + 1
Increase kVp = decrease exposure time
Increase mA = decrease exposure time
Decrease mA = increase exposure time
Increase Density setting by + 1 = increase (?)
ONLY DENSITY will change receptor exposure; exposure time just changes how quickly you get there
52
a minimum kVp change of ___% is necessary to yield a noticeable receptor exposure change
10%
53
a minimum mAs change of ___% is necessary to yield a noticeable receptor exposure change
30%
54
what is grid focus error? where is grid cutoff seen?
using a grid outside established range range (SID), along lateral edges of image
55
what is a moire effect (aliasing) artifact?
a wavy artifact in digital imaging caused when grid lines are projected onto the imaging plate and are parallel with the scanning laser
56
what is a ghost image artifact?
caused when there is insufficient erasure of an image
57
the number of pixels sampled per millimeter as the laser scans each line of the imaging plate
sampling frequency
58
when you increase matrix size, you (increase/decrease) spatial resolutino
increase
59
what tool is used for spatial resolution tests in digital radiography?
line pair gauge
60
grid errors***
off angle
61
what is lateral decentering error in terms of grid error? where is grid cutoff seen?
central ray is not centered to the center of grid IN A FOCUSED GRID, higher frequency of grid lines on one side than the other
62
what is stopped grid error in terms of grid error? where is grid cutoff seen?
when an oscillating grid stops moving during the exposure, grid lines across entire image
63
what is upside down error in terms of grid error? where is grid cutoff seen?
grid is placed upside down, normal receptor exposure in center of image but complete cutoff towards both ends of the image
64
what is off level grid error? where is grid cutoff seen?
grid is placed not perpendicular (not level) in relation to the x-ray beam, results in decreased exposure across entire image
65
contrast of an image (increases/decreases) as the ratio of the grid increases
increases
66
which is better to reduce magnification: longer SID or shorter OID?
shorter OID
67
sampling frequency is the _______________________ as the _____ scans each line of the imaging plate
number of pixels sampled per millimeter, laser
68
increasing the sampling frequency (increases/decreases) the spatial resolution
increases
69
(CR/DR) uses sampling frequency
CR
70
Nyquist frequency is the relationship between the __________________ and __________________
sampling frequency, the spatial resolution
71
S numbers are (directly/inversely) proportional to the exposure received by the IR
exposure index numbers are (directly/inversely) proportional
S numbers are inverse, EI are direct
72
where is the pre-reading kVp meter? what does it do?
primary or low voltage circuit between secondary side of autotransformer and primary side of the step up
provides a reading of the voltage that will be induced in the secondary side of the step up
73
where is the exposure switch? what does it do?
primary or low voltage circuit between secondary side of autotransformer and primary side of the step up
closes the circuit between the autotransformer and the step up transformer
74
where is the exposure timer? what does it do?
primary or low voltage circuit between secondary side of autotransformer and primary side of the step up
provides a means of controlling the duration of the radiographic exposure
75
where is the mA selector? what does it do?
connected in series within the low voltage filament circuit between the autotransformer and the step down transformer
regulates amperage conducted through the filament circuit which regulates the amount of thermionic emission
76
where is the focal spot selector? what does it do?
located within the filament low voltage circuit
selects the size of the filament within a dual filament tube
77
where is the mA meter? what does it do?
located in series to the midpoint of the secondary side of the step-up transformer
helps rectifiers/diodes make direct current
78
where are the rectifiers? what do they do?
in high voltage circuit
convert AC to DC
79
values of interest (region of interest) is the __________ of information that is ______________________
digital data set, arranged into a histogram distribution
80
what is rescaling?
a digital processing technique that is used to modify an overexposed or underexposed image
adjusts actual histogram to expected/desired
81
what is a LUT?
look up table
Mathematical process used to add desired brightness/contrast to the image
82
what is modulation transfer function?
Accuracy of the image compared to the actual object
System’s ability to transfer objection information into the image
83
with MTF, resolution is best as the MTF ___; worst score is ____
approaches 1; worst at 0
84
what is edge enhancement?
improves visibility of small, high contrast structures, noise may be slightly increased
85
what is equilization?
postprocessing function where underexposed areas (light) are made darker and overexposed areas (dark) are made light
86
what is spatial frequency filtering also known as?
what is edge enhancement also known as?
smoothing or low pass filtering, high pass filtering
87
what is spatial frequency filtering/smoothing/low pass filtering?
postprocessing function that suppresses image noise (spatial resolution is degraded with this function)
88
what is electronic cropping or masking?
postprocessing "collimation"
89
window level determines ____________; window width determines ________________
brightness, gray scale (contrast)
90
wider window widths result in a (long/short) gray scale with (high/low) image contrast
wider = longer gray scale with low contrast
91
narrow window widths result in a (long/short) gray scale with (high/low) image contrast
narrow = short gray scale, high contrast
92
what does HIS stand for? what does it refer to?
hospital information system; contains full patient information
93
what does RIS stand for? what does it refer to?
radiology information system; contains radiology specific information about a patient including radiologist reports
94
what does EMR stand for? what does it refer to?*
electronic medical record
95
what does EHR stand for? what does it refer to?*
electronic health record
96
what is a WAN versus a LAN network? which is faster?
wide area network (city/state/world)
local area network (smaller)
LAN is faster than WAN
97
most common physical network connection layout
mesh
98
what does DICOM stand for?
digital imaging and communication in medicine
99
what does PACS stand for?
picture archiving and communication system
100
what does RAID stand for?
redundant array of independent disks
RAID 5 is most current
101
laser used in conversion of analog images into digital images
helium-neon laser
102
beam restriction variance
2% (+/-) of SID
103
linearity variance
10% (+/-)
104
reproducibility variance
5% (+/-)
105
how often should lead aprons be tested?
annually
106
x axis on histogram = ____
y axis on histogram = ____
x axis = intensity
y axis = frequency
107
signal values below VOI on histogram = ____________
Above VOI = ______________
below = collimated exposure
above = outside body
108
histogram accuracy can be improved with __________ and _______________
selecting correct body part, correct collimation
109
______________ identifies values of interest for processing
Histogram analysis
110
a histogram is a _____ representing the _________ recorded by the _________
graph, range of exposure values, image receptor
111
what is flat fielding?
post processing function implemented in order to eliminate non-uniformities in X-ray imaging sensors (applicable in the anode heel effect)
112
what does MIMPS stand for?
medical image management & processing system
113
how is EHR different from an EMR?
EHRs are used to communicate information in EMRs
114
as anode angle increases, there is a ____________ in anode heel effect and a _______ in the effective focal spot
decrease, increase
115
Total brightness levels visible in the image refers to
gray scale
116
Describe low contrast image appearance
difference is small
117
Describe high contrast image appearance
difference is big
118
How would a “short scale” contrast appear?
High contrast, short scale
119
How would a “long scale” contrast appear?
Low contrast, long gray scale
120
high kVp = (high/low) scatter
low kVp = (high/low) scatter
high kVp = high scatter
low kVp = low scatter
121
Why does using a grid improve contrast?
helps to maintain high signal differences in remnant beam
122
increasing grid ratios (ex: adding a grid) will ______ scatter which will _____ image contrast
decrease, increase
123
anything that increases scatter will do what to contrast?
decrease
124
with a higher kVp, there is a (higher/lower) percent of photoelectric effect and a (higher/lower) percent of Comptom effect occurring
lower, higher
125
Will low kVp have a high or low attenuation?
high attenuation
126
Will high kVp have a higher or lower attenuation?
low attenuation
127
low x-ray absorption = (high/low) signal
high signal
128
true/false: windowing changes the data set of the image
false, it does not change the data set
129
narrow window width = __________
wide window width = ___________
narrow window width = little gray, high contrast
wide window width = lots of gray, low contrast
"window lets the gray in"
130
for optimal spatial resolution, do you want a large or small OID?
small OID
131
Increasing SID (increases/decreases) spatial resolution due to __________________________
increases, beam divergence/less penumbra is created
132
do we want large or small DELs for spatial resolution?
we want SMALL DELs for good spatial resolution
133
do you want large/small factors for the following image receptor factors in spatial resolution?
DEL
pitch
fill factor
small DEL
small pitch
larger fill factor
134
an image receptor has a matrix of ____ whereas the digital image has a matrix of _____
DELs, pixels
135
do you want a large or small matrix for good spatial resolution?
large matrix (large TV!)
136
SOD/SID "source" is measured from what?
the anode target
137
minimum recommended resolution by the ACR
3MP
138
the ___________ test can test monitor resolution. if it fails, it is usually the result of ________________
SMPTE Test Pattern, structural damage within the monitor
139
what does the SMPTE test pattern test?
spatial resolution within the MONITOR
140
as spatial frequency increases (object size decreases), MTF ____________
decreases
141
what type of filter is used for absorbing low energy x-rays before they reach the patient?
inherent filter
142
what are compensating filters? are they in the tube housing?
used to even out exposure levels across an image, not part of the radiographic unit
143
recommended maximum dose limit for occupational radiation exposure in the US?
50 mSv per year
144
with regards to decreasing pixel size, decreasing can sometimes increase noise, but ____________ outweighs this
spatial resolution improvement
145
Viewing angle that is best
90 degree angle to the monitor
146
DI of 3 means the receptor received exposure ____ too (high/low)
100% too high
147
DI of 2 means the receptor received exposure ____ too (high/low)
58% too high
148
DI of 1 means the receptor received exposure ____ too (high/low)
26% too high
149
DI of -1 means the receptor received exposure ____ too (high/low)
21% too low
150
DI of -2 means the receptor received exposure ____ too (high/low)
37% too low
151
DI of -3 means the receptor received exposure ____ too (high/low)
50% too low
152
CCD and TFT are used in _________________
general readiography
153
TFT is used for _____________ and ____________
angiography, fluoroscopy
154
what does the scintillation layer do?
converts xrays to light
155
what does the CCD layer do?
converts light to an electrical signal
156
what does the TFT layer do?
sends electrical signal to ADC
157
what does the photodiode layer do?
converts light to an electrical signal
158
which three of the following components are included in indirect capture flat-panel digital image detector systems?
photodiode
scintillation layer
ADC
thin-film transistor array
photoconductor
photodiode, scintillation, TFT array
159
flat-panel detector systems typically use a ______________
thin-film transistor (TFT)
160
systems using a scintillation layer must have a ______________ or a ___________ to convert _____________
photodiode or charged coupled device, light into an electrical signal
161
in a CCD system, the scintillation layer is connected to the CCD sensor chips by _________
lenses or fiber optics
162
what are the 3 controlling factors for magnification?
SID, OID, SOD
163
what are the 3 controlling factors for shape distortion?
(1) anatomy of interest alignment (foreshortening)
(2) tube and (3) IR alignment (elongation)
164
what factor(s) control foreshortening?
anatomy of interest being parallel versus not parallel with tube/IR
165
what factor(s) control elongation?
tube and IR
166
mnemonic for remembering elongation vs. foreshortening factors
"TIRE"
Tube, IR = Elongation
167
with respect to foreshortening/elongation, the law of isometry states that the CR should be set at _________ formed between the object & receptor to minimize ____________
half of the angle formed, foreshortening
168
magnification factor = _________
SID/SOD
169
when kVp is decreased, you (increase/decrease) the differences in signal intensities in the remnant beam
increase the difference
170
S number exposure indicators are (direct/inverse)
inverse
171
DI numbers are (direct/inverse)
direct
172
example: S number ideal for an exposure is 200. 75 would mean the x-ray is (overexposed/underexposed)
overexposed
173
What is on the x-axis on a histogram?
exposure values
174
What is on the y-axis on a histogram?
frequency
175
portion of processing that modifies to desired brightness/contrast
look up table
176
portion of processing that corrects for over or underexposure
rescaling
177
what are the required pieces of information on an image for identification?
patient name
patient DOB
exam date
exam location/facility
R or L marker
178
what is receptor damage? does it happen with CR or DR?
Physical damage that causes hyper-dense artifact on the image that can occur with Dr or CR
179
what is a detector element malfunction or dead pixel? does it appear in CR or DR?
Dead or damaged DELs appear as hyper-dense artifact, only in DR
180
what is ghost imaging? does it appear in CR or DR?
incomplete erasure where old exams are seen; seen in CR only
181
how does "hyper-dense" artifact appear?
bright white
182
Centering must be within what percentage?
1% of the SID
183
