Digital Imaging QC

advantages of digital over SF

reduced repeats from technical errors due to corrective software
filing: archived on computer system and no file room reducing lost images
postprocessing: resolution enhanced by computer software
teleradiology
reduced pt dose

disadvantages of digital over screen film

cost to initiate: equipment, hardware, software
lower spatial resolution: can resolve less lp/mm
collimation and centering need to be precise
more sensitive to scatter
dose creep: could increase pt dose

CR Erasure test

erasure thoroughness
expose IP with thick lead block
erase
make exposure with nothing and reprocess
verify absence of ghost image of lead block

plate uniformity testing is for

detectors and CR cassettes

plate uniformity testing

all calibrated to produce the same response to the same radiation exposure levels
expose multiple different detectors with the same kVp and mAs and should result in the same DI number

detector spatial resolution test

using LP test tool
the more lines you can see, the better SR

monitors need to be calibrated to

DICOM Grayscale standard display function
each equal monitor (all rads) must be displayed with same grayscale and brightness level

monitor evaluation is for

ensure consistent and accurate display of medical images: brightness, contrast, spatial resolution, distortion
2 patterns
SMPTE
TG 18

patterns for monitor evaluation

SMPTE
TG18

SMPTE

Society of Motion Picture and Television Engineers
display contrast
spatial resolution
distortion
luminescence: overall brightness

luminesence

overall brightness

where do you find display contrast on SMPTE

where to find spatial resolution on SMPTE

LP pattern is visible and straight, all letters and numbers are clear

where to find distortion on SMPTE

any area where the lines arent straight or visible

where to find luminescence on SMPTE

all squares are visible from adjacent squares

what do missing/dead pixels look like on monitor

appear as a white spot
areas of increased or decreased brightness
image blur

TG 18 test pattern

by AAPM (American Association of Physicists in Medicine)
geometric distortion
luminescence
resolution
no artifacts

TG18 and geometric distortion

straight lines
borders visible
image centered on screen

TG18 and contrast

5% and 95% squares visible

aspect ratio

ratio of width to height of display monitor

the software settings of computer controlling display

must be adjusted to match the aspect ratio or geometric distortion will occur

refresh rate

how many times each second that the monitor rewrites or updates the image on the display monitor
if too low can cause flickering

if refresh rate is too low

can cause flickering

printer QC

wet/dry laser imager

wet/dry laser imager how often

daily/weekly

wet/dry laser imager qc

look for artifacts
test temp of chemicals in wet
print test pattern to check density with densitometer

print test pattern for

wet/dry laser imager

technologist daily duties

inspect and clean PSP Cassettes or receptors and check hinges or latches
erase imaging plates
inspect laser printer
check interface and network connections

monthly QC Checks include

monitor tests: SMPTE/TG18
reject analysis

SMPTE should be done how often

weekly/monthly

reject analysis QC

QC tech, supervisor, RSO
data analyzed for reason, number of repeats, tech that repeated

when selecting reason for repeat why

must be accurate bc if it is due to over/underexposure the device may need to be recalibrated

semiannual QC is

vendor personnel preventative maintenance
PSP and FPD resolution test pattern

PSP and FPD resolution test pattern

contains lp/mm.
image it and compare with manufacturer recommendation to make sure it matches

DAP

dose area product

KAP

kerma area product

DAP and KAP for
measured by

measure of the total amount of radiation on a pt
measured by ionization chamber