arrt review: image production Flashcards
benefit and disadvantage of fixed kVp chart
consistent contrast, high mAs settings for larger patients/body parts
benefit and disadvantage of variable kVp chart
assures penetration of the objects of interest; contrast is prone to unacceptable variations
technical considerations for a wet plaster cast
doubling of exposure factors
100% increase in mAs or 8-10 increase in kVp
technical considerations for a dry plaster cast
50-60% increase of mAs, 5-7 increase of kVp
technical considerations for a fiberglass cast
25-30% increase of mAs, 3-4 increase in kVp
barium sulfate contrast media requires (higher/lower) kVp techniques to ensure proper penetration of the contrast
higher
IV iodine based contrast media requires (higher/lower) kVp techniques to ensure proper penetration of the contrast
lower; to prevent over penetration
matrix size is dependent on _______ and _______________
field of view, pixel density
increase in IR size results in a (decrease/increase) in matrix size
increase
decreasing pixel size results in (increased/decreased) matrix size and (increases/decreases) spatial resolution
matrix size = increase
spatial resolution = increase
decreasing pixel size (increases/decreases) visibility of small structures
increases
as DEL increases, spatial resolution (increases/decreases)
decreases
what is spatial resolution measured in?
line pairs per mm
pixel size is measured ___________; pixel pitch is measured _______________
end to end, center to center
minimum response time for AEC
approximately 0.001 sec
the time it takes for an AEC system to respond and send the signal to terminate the exposure
minimum response time
those factors that affect the amount of exposure reaching the radiographic image receptor
photographic factors
those factors that affect the degree of divergence of x-ray beam and the information recorded on the radiographic image receptor
geometric factors
two subtypes of geometric factors
recorded detail, distortion
what type of anatomy do you put under the cathode end?
“FAT CAT”
dense anatomy under cathode end
tube housing leakage maximum rate
0.88 mGy/hr at 1 m
what is the space charge effect?
collection of free electrons surrounding the filament
at 1000 mA, no more electrons can be boiled off the filament
equation to calculate heat units
heat units = kVp x mA x S x W
where W is the waveform factor
waveform factor single phase
1
waveform factor 3 phase 6 pulse
1.35
waveform factor 3 phase 12 pulse
1.41
waveform factor high frequency
1.45
waveform factors for3 phase 6 pulse, 3 phase 12 pulse, and high frequency are sometimes averaged to ____
1.4
a decreased anode angle (increases/decreases) the anode heel effect
increases
an increased anode angle (increases/decreases) the anode heel effect
decreases
the anode angle and the anode heel effect are _______ related
inversely
which of the following anode angles is steep/small?
6 or 20
6
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
a small anode angle with produce a (very narrow/very large) effective focal spot
very narrow
what type of anode angle do you want for high spatial resolution?
decreased (small) anode angle
what is larger, the actual focal spot or the effective focal spot?
actual is always larger than effective
the autotransformer works on what type of induction?
self induction
The step up & step down transformers work on what type of induction?
mutual induction
in a transformer, the side with more turns = where the voltage is (lower/higher)
higher
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”
step up transformers
(increase/decrease) voltage
(increase/decrease) amperage
increase voltage, decrease amperage
step down transformers
(increase/decrease) voltage
(increase/decrease) amperage
decrease voltage, increase amperage
3 phase 6 pulse rectification has what voltage ripple?
14%
3 phase 12 pulse rectification has what voltage ripple?
4%
high frequency rectification has what voltage ripple?
~1%
mA station selected by the radiographer determines the amount of _______________ sent to the (primary/secondary) side of the filament transformer
current and voltage, primary
a rheostat operates as a ____________ within the filament circuit. by varying ________ in a circuit, ____ can be controlled
variable resistor, resistance, current
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
What type of exams would you use a “stationary” grid? Will you see grid lines?
portable or tabletop; you can see grid lines
What type of exams would you use an “oscillating” grid?
within bucky system; no grid lines
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
a minimum kVp change of ___% is necessary to yield a noticeable receptor exposure change
10%
a minimum mAs change of ___% is necessary to yield a noticeable receptor exposure change
30%
what is grid focus error? where is grid cutoff seen?
using a grid outside established range range (SID), along lateral edges of image
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
what is a ghost image artifact?
caused when there is insufficient erasure of an image
the number of pixels sampled per millimeter as the laser scans each line of the imaging plate
sampling frequency
when you increase matrix size, you (increase/decrease) spatial resolutino
increase
what tool is used for spatial resolution tests in digital radiography?
line pair gauge
grid errors***
off angle
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
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
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
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
contrast of an image (increases/decreases) as the ratio of the grid increases
increases
which is better to reduce magnification: longer SID or shorter OID?
shorter OID
sampling frequency is the _______________________ as the _____ scans each line of the imaging plate
number of pixels sampled per millimeter, laser
increasing the sampling frequency (increases/decreases) the spatial resolution
increases
(CR/DR) uses sampling frequency
CR
Nyquist frequency is the relationship between the __________________ and __________________
sampling frequency, the spatial resolution
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
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
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
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
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
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
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
where are the rectifiers? what do they do?
in high voltage circuit
convert AC to DC
values of interest (region of interest) is the __________ of information that is ______________________
digital data set, arranged into a histogram distribution
what is rescaling?
a digital processing technique that is used to modify an overexposed or underexposed image
adjusts actual histogram to expected/desired
what is a LUT?
look up table
Mathematical process used to add desired brightness/contrast to the image
what is modulation transfer function?
Accuracy of the image compared to the actual object
System’s ability to transfer objection information into the image
with MTF, resolution is best as the MTF ___; worst score is ____
approaches 1; worst at 0
what is edge enhancement?
improves visibility of small, high contrast structures, noise may be slightly increased
what is equilization?
postprocessing function where underexposed areas (light) are made darker and overexposed areas (dark) are made light
what is spatial frequency filtering also known as?
what is edge enhancement also known as?
smoothing or low pass filtering, high pass filtering
what is spatial frequency filtering/smoothing/low pass filtering?
postprocessing function that suppresses image noise (spatial resolution is degraded with this function)
what is electronic cropping or masking?
postprocessing “collimation”
window level determines ____________; window width determines ________________
brightness, gray scale (contrast)
wider window widths result in a (long/short) gray scale with (high/low) image contrast
wider = longer gray scale with low contrast
narrow window widths result in a (long/short) gray scale with (high/low) image contrast
narrow = short gray scale, high contrast
what does HIS stand for? what does it refer to?
hospital information system; contains full patient information
what does RIS stand for? what does it refer to?
radiology information system; contains radiology specific information about a patient including radiologist reports
what does EMR stand for? what does it refer to?*
electronic medical record
what does EHR stand for? what does it refer to?*
electronic health record
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
most common physical network connection layout
mesh
what does DICOM stand for?
digital imaging and communication in medicine
what does PACS stand for?
picture archiving and communication system
what does RAID stand for?
redundant array of independent disks
RAID 5 is most current
laser used in conversion of analog images into digital images
helium-neon laser
beam restriction variance
2% (+/-) of SID
linearity variance
10% (+/-)
reproducibility variance
5% (+/-)
how often should lead aprons be tested?
annually
x axis on histogram = ____
y axis on histogram = ____
x axis = intensity
y axis = frequency
signal values below VOI on histogram = ____________
Above VOI = ______________
below = collimated exposure
above = outside body
histogram accuracy can be improved with __________ and _______________
selecting correct body part, correct collimation
______________ identifies values of interest for processing
Histogram analysis
a histogram is a _____ representing the _________ recorded by the _________
graph, range of exposure values, image receptor
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)
what does MIMPS stand for?
medical image management & processing system
how is EHR different from an EMR?
EHRs are used to communicate information in EMRs
as anode angle increases, there is a ____________ in anode heel effect and a _______ in the effective focal spot
decrease, increase
Total brightness levels visible in the image refers to
gray scale
Describe low contrast image appearance
difference is small
Describe high contrast image appearance
difference is big
How would a “short scale” contrast appear?
High contrast, short scale
How would a “long scale” contrast appear?
Low contrast, long gray scale
high kVp = (high/low) scatter
low kVp = (high/low) scatter
high kVp = high scatter
low kVp = low scatter
Why does using a grid improve contrast?
helps to maintain high signal differences in remnant beam
increasing grid ratios (ex: adding a grid) will ______ scatter which will _____ image contrast
decrease, increase
anything that increases scatter will do what to contrast?
decrease
with a higher kVp, there is a (higher/lower) percent of photoelectric effect and a (higher/lower) percent of Comptom effect occurring
lower, higher
Will low kVp have a high or low attenuation?
high attenuation
Will high kVp have a higher or lower attenuation?
low attenuation
low x-ray absorption = (high/low) signal
high signal
true/false: windowing changes the data set of the image
false, it does not change the data set
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”
for optimal spatial resolution, do you want a large or small OID?
small OID
Increasing SID (increases/decreases) spatial resolution due to __________________________
increases, beam divergence/less penumbra is created
do we want large or small DELs for spatial resolution?
we want SMALL DELs for good spatial resolution
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
an image receptor has a matrix of ____ whereas the digital image has a matrix of _____
DELs, pixels
do you want a large or small matrix for good spatial resolution?
large matrix (large TV!)
SOD/SID “source” is measured from what?
the anode target
minimum recommended resolution by the ACR
3MP
the ___________ test can test monitor resolution. if it fails, it is usually the result of ________________
SMPTE Test Pattern, structural damage within the monitor
what does the SMPTE test pattern test?
spatial resolution within the MONITOR
as spatial frequency increases (object size decreases), MTF ____________
decreases
what type of filter is used for absorbing low energy x-rays before they reach the patient?
inherent filter
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
recommended maximum dose limit for occupational radiation exposure in the US?
50 mSv per year
with regards to decreasing pixel size, decreasing can sometimes increase noise, but ____________ outweighs this
spatial resolution improvement
Viewing angle that is best
90 degree angle to the monitor
DI of 3 means the receptor received exposure ____ too (high/low)
100% too high
DI of 2 means the receptor received exposure ____ too (high/low)
58% too high
DI of 1 means the receptor received exposure ____ too (high/low)
26% too high
DI of -1 means the receptor received exposure ____ too (high/low)
21% too low
DI of -2 means the receptor received exposure ____ too (high/low)
37% too low
DI of -3 means the receptor received exposure ____ too (high/low)
50% too low
CCD and TFT are used in _________________
general readiography
TFT is used for _____________ and ____________
angiography, fluoroscopy
what does the scintillation layer do?
converts xrays to light
what does the CCD layer do?
converts light to an electrical signal
what does the TFT layer do?
sends electrical signal to ADC
what does the photodiode layer do?
converts light to an electrical signal
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
flat-panel detector systems typically use a ______________
thin-film transistor (TFT)
systems using a scintillation layer must have a ______________ or a ___________ to convert _____________
photodiode or charged coupled device, light into an electrical signal
in a CCD system, the scintillation layer is connected to the CCD sensor chips by _________
lenses or fiber optics
what are the 3 controlling factors for magnification?
SID, OID, SOD
what are the 3 controlling factors for shape distortion?
(1) anatomy of interest alignment (foreshortening)
(2) tube and (3) IR alignment (elongation)
what factor(s) control foreshortening?
anatomy of interest being parallel versus not parallel with tube/IR
what factor(s) control elongation?
tube and IR
mnemonic for remembering elongation vs. foreshortening factors
“TIRE”
Tube, IR = Elongation
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
magnification factor = _________
SID/SOD
when kVp is decreased, you (increase/decrease) the differences in signal intensities in the remnant beam
increase the difference
S number exposure indicators are (direct/inverse)
inverse
DI numbers are (direct/inverse)
direct
example: S number ideal for an exposure is 200. 75 would mean the x-ray is (overexposed/underexposed)
overexposed
What is on the x-axis on a histogram?
exposure values
What is on the y-axis on a histogram?
frequency
portion of processing that modifies to desired brightness/contrast
look up table
portion of processing that corrects for over or underexposure
rescaling
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
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
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
what is ghost imaging? does it appear in CR or DR?
incomplete erasure where old exams are seen; seen in CR only
how does “hyper-dense” artifact appear?
bright white
Centering must be within what percentage?
1% of the SID
