arrt review: image production / fluoroscopy Flashcards
Flux gain is the ______________ gained during acceleration from _____________ to the ______________
kinetic energy, photocathode, output phosphor
Minification gain is the _____________________ from the _______________ to the __________________
concentration of photoelectrons, input phosphor, output phosphor
Brightness is the ability of the ___________________ to increase the _______________ level of the image
image intensifier, brightness
percentage that measures the efficiency of the image intensifier
conversion factor
What is the Input phosphor made of? what does it do?
Cesium iodide
converts x-rays to light photons (1 to 1,000 light photons)
What is the output phosphor made of? what does it do?
Zinc cadmium sulfide
converts e- to light photons
What is the photocathode made of? what does it do?
Cesium and antimony compounds
converts light photons to photoelectrons (e-)
Why are lower grid ratios used in fluoroscopic imaging?
Using higher kVp and lower mAs (using contrast is the reason behind these technical factors)
Only __________ grids used in conventional fluoro (____________________________________)
linear, (crossed in interventional)
how do you calculate brightness gain?
Brightness gain = flux gain x minification gain
how do you calculate flux gain?
output light photons/input x-ray photons
how do you calculate minification gain?
diameter of input phosphor^2/diameter of output phosphor^2
what is the order of components in an image intensifier?
(anti-scatter grid)
input phosphor
photocathode
electrostatic focusing lenses
anode
output phosphor
what converts x-rays to light in the image intensifier?
input phosphor
which comes first in the image intensifier: photocathode or input phosphor?
input phosphor
what converts light photons to electrons in the image intensifier?
photocathode
what converts electrons to light photons in the image intensifier?
output phosphor
what does a CCD/video camera do in the image intensifier?
convert light photons to electrical (analog) signal
what does an ADC do in the image intensifier?
converts electrical (analog) signal to a digital signal
the ABC prevents fluctuations in the _______
SNR
how does Automatic Brightness Control work?
Feedback loop from image intensifier or flat panel detector to adjust exposure factors
what is an example of another name for ABC?
automatic exposure rate control (AERC)
what is vignetting?
decrease in image brightness around the edges of the image
what is vignetting caused by?
caused by OID or curved edge of input phosphor
what is pincushion artifact?
Parts of the image appear curved or bent inward toward the center of the image
what is pincushion artifact caused by?
curved shape of input phosphor, external magnetic fields
what is S-shape artifact?
parts of the image appear curved or bent inward toward the center of the image
what is S-shape artifact caused by?
external magnetic fields, mis-angulation of the x-ray beam
what is blooming?
parts of the image white out causing a loss of visual sharpness
what is blooming caused by?
high energy x-rays hitting the input phosphor, creating intense light production
what is veiling glare artifact?
type of blooming, contrast recuing haze on the fluoro image
what is veiling glare artifact caused by?
scattering of x-ray, light, and e- energies inside the image intensifier
what is lag?
delay in the response tie of the image intensifier to changes in beam intensity
what is noise?
grainy or mottled image
how can you reduce lag?
use frame averaging or high-speed image intensifiers
older image intensifier systems used _____ to send to a TV; modern image intensifiers use ________
vidicon, CCD
image intensifiers with CCDs have __________________ and __________________ compared to vidicon tube systems
higher spatial resolution, less image blooming and lag
order of parts in flat panel detectors
Indirect (scintillation → photodiode → TFT)
What kind of digital conversion is used in FPD’s in fluoro? Indirect or direct?
Indirect (scintillation → photodiode → TFT)
flat panel vs. image intensifiers
flat panels =
(more/fewer) energy conversions (higher/lower) patient dose
(more/less) artifacts
(wider/narrower) dynamic range
fewer energy conversions
lower patient dose
less artifacts
wider dynamic range
what is the scintillation layer made of in a flat panel detector?
cesium iodide or gadolinium
what is the photodiode layer made of in a flat panel detector?
amorphous silicon
overall conversion process of flat panel detectors
xrays –> light –> electrical signal —> digital signal
with pulsed fluoroscopy, the higher the frame rate, the ____________
more seamless the image appears
which is a setting/mode, and which is operator controlled?
Pulsed fluoro, intermittent fluoro
pulsed = mode, intermittent = operator
what occurs in frame averaging?
pixels are averaged and compared for the most common elements
what is the effect of frame averaging on patient dose?
Does not impact patient exposure or tube heat
what is the effect of frame averaging on fluoro image quality?
Decreases noise, makes image clearer
Static fluorograph made during fluoro exam is a ________
spot image
Spot imaging = (higher/lower/no effect) on patient dose
higher
Last image hold = (higher/lower/no effect) on patient dose
no effect
spot imaging is like a _______ and last image hold is like a ____________
static xray, screenshot
federally mandated limit for the exposure rates of conventional fluoro
100 mGy/minute
where is ghost imaging seen, CR or DR?
CR only
