Image production Flashcards
Increase mA =
exposure, contrast, spatial, distortion
increase exposure
Increase kVp =
exposure, contrast, spatial, distortion
increase exposure
decrease contrast
Increase OID =
exposure, contrast, spatial, distortion
Increase contrast (air gap)
Decrease spatial
Increase distortion
Increase SID =
exposure, contrast, spatial, distortion
Decrease exposure
Increase spatial
Decrease distortion
Increase Focal spot size =
exposure, contrast, spatial, distortion
decrease spatial
Increase grids =
exposure, contrast, spatial, distortion
Decrease exposure
Increase contrast
Increase flitration =
exposure, contrast, spatial, distortion
Decrease exposure
Increase contrast
Increase motion =
exposure, contrast, spatial, distortion
Decrease spatial
Increase anode heel =
exposure, contrast, spatial, distortion
exposure
pt factors =
exposure, contrast, spatial, distortion
all
which (SID / OID / SOD) governs sharpness
SOD
how to get SOD from sid and oid
Sid - oid
Unsharpness formula w/ and w/o Focal spot
fs x oid/sod OR sod/oid
Change in SID greater than - should increase tech (mA)
10 %
Mag formula
SID/SOD
Anode angle increase =
Larger effective spot
decrease spatial
Which end is more intense b/c of anode heel
cathode 25% more intense, thicker part goes here
Spaital resolution 4 variables
- motion
- SID, OID ,SOD
- Focal spot size
- size of dels / pixels
sharpness formula
sod/oid
Del drop out is b/c of
TFT failure (IR)
Del saturation
max charge del can hold
Nyquist theorem
highest spatial resolution that can be recorded
Nyquist theorem controlled by
pixel pitch
MTF
modulation transfer function
how well DR can record spatial
Best way to measure blur in the system
MTF (o=worst)
MTF depends on
del pitch
prenumbra is controlled by
SOD OID focal spot size
Limiting factor for spatial resolution
pixel
Pixel size formula
FOV/matrix
Pixel size decrease = - spatial & - matrix
increase, increase
Pixel pitch
space between pixels
Pixel bit depth
max # of brightness
base of 2
Spatial frequency
min object size
spatial frequency formula
1/2(Psize)
Attenuation coefficient
% of beam absorbed by pt
Attenuation coefficient based on
voxels
Analog to digital converter selects
selects value for dynamic range
DQE
Detective quantum efficiency
converts xrays to signal
- determines overall efficiency of system
DQE
Dels fill factor
% of semiconductor surface area
Indirect CR CCD
scillation
lens/fiber optics
sensor chip (light into #s)
Indirect DR
scintillation cesium iodide gadolinium (xray to light) Photodiode amorphous silicon (light to electrical charge) TFT (collects & processes)
DR direct
Nonscintillation amphrous silium (xray hits; release electron) TFT (collects & processes)
CR
Photostimuable bromides eurpium
bromide = light
phosphor stores
eurpium makes phosphpr release & make electrons
electrical generator
mechnical to electrical
electrical motors
electrical to mechincal
Autotransformer
change voltage to match kvp
selfinduction
step up transformer
volts to kilvolts
rectifier
makes ac to dc
rectifier single-phase ripple
100%
rectifier three-phase ripple 6 pulse
14%
rectifier three-phase ripple 12 pulse
4%
high freq ripple
1%
quantization
values to pixel from grayshade (bit depth)
rescaling
fixes images brightness and contrast
flat field uniformity
evens out brightness from dead pixels
interpolation
fixes dead pixels
histogram analysis
finds useful voi of image
- makes histogram
rescaling
Look up table
makes good level of contrast and broghtness
graduation processing
compares to look up table
grayscale
of value given to pixel
equalization
sharpness, contrast
edgehancement
high pass
improves visibility of small, high contrast areas
smoothing
low pass
reduces noise, spatial and contrast
frequency domain
sorting image from size
halo effect
noise
darker gets darker
lighter gets lighter
detail processing
see fine details w/o change in contrast
intensity domain
sorting image by values of pixels
window level
brightness
window with
contrast
spatial domain
sorts image by location of pixels
point processing
subtraction
area processing
zooming in and out
global processing
flipping from left to right
DICOM
digital imaging and communication in medicine
protocol for pacs
PACS
picture archiving and communication system
storage, retrieval, manipulation, and transmission of image
RIS
modality work list, radiology data
HIS
stores and manages all systems
assigns medical # and pt info
exposure indicator
amount of light reiceved bt plate
for milli move decimal place over
3 times
for window level and width, increasing =
lower contrast / brightness
15 % rule
increase kvp by 15% doubles exposure
fixed kvp
same kvp
change ma
variable kvp
change kvp same ma
more common
beam intensity formula
intensity1 kvp1^2
/ = /
intensity2 kvp2^2
base 60
kvp is 2x measured part
60 + (part x 2)
mA controls
heat that gets to filament
how AEC works
- chamber gets current
- capactior holds charge
- thyratron releases the charge
- electromagnet switch stope exposure
ACE detectors are placed
in front of the grid
AEC density/intensity control
how sensitive thyraton is
MRT
minimum response time
how long circuit takes to pass rad
0.002-.02
inherent filtration
parts of tube
1.5mm
4cm rule
pt thickness increase by 4cm, double exposure
Minimum change for tech
35% ma
5% kvp
grid ratio
5:1 2 6 ;1 3 8; 1 4 10;1 5 12;1 5 16;1 6
moire effect
incorrected grid
off level
grid titled, exposure decrease exposure
off focus
sid wrong, decrease density at edges
off center
cr not in center, decrease exopsures
upside down grid
underexposure except in center
how fluoro works
image intensifier (xray to light to electrical signal) 1. Input phosphor xray to light 2. photocathode light to electrons 3. electrostatic lens 4. output phosphor electrons to light
flux gain
image is brighter b/c of acceleration
minification gain
the output is smaller than the input (brighter image)
total brightness fluoro
flux and minifaction
conversation factor
Ratio of luminance of output vs exposure rate of input
flat panel image intensifier
replaces image intensifer
see better smaller anatomy
grid conversion formula
ma1 grid factor 1
/ = /
ma2 grid factor 2
DAP
dose area product
total air kerma hit pt
ABC / AERC
kvp and ma adjusted to keep brightness
fluoro sid min
15”
12” portable
OSLS
Al oxide
stimulated by laser to read dose
energy released as light
thermoluminescent dosimeter
lithium fluoride crystals
correction factor single phase
1
correction factor 3 phase & high freq
1.4
output phosphor made of
zinc cadmium sulfide
new ma formula?
direct square law
to find actual image size
image size/mag factor
mag factor = sid/sod (sid - oid)
wide width = - contrast
long, short
