Quality Assurance and Fault Analysis Flashcards
What does quality assurance program cover
procedures staff training x ray equipment patient dose image processing display equipment image quality
When should digital image receptors be checked
they are reusable and therefore susceptible to wear tear and mishandling
check regularly - every 3 months
What are things to check on the digital image receptor
receptor itself
imager uniformity
image quality
What do we look or on the receptor
check for visible damage to casing/wiring
check if clean (no congealed disinfectant or saliva)
How do we check image uniformity of digital receptor
expose receptor to an unattenuated x ray beam and check if resulting image is uniform
should be consistent shade of grey
How do we check image quality of digital receptor
take a radiograph of a test object and assess the resulting image against a baseline
What does scratches on phosphor plate appear as
white lines
What does cracking from flexing the phosphor plate result in
network of white lines
What does delamination of phosphor plates result in
white areas around the edge
What is delimitation
separation of phosphor layer from base plate
If there is sensor damage to the solid state sensor what can this result in
square/straight lines
If there is damage to sensor’s blasting casing what can happen
can get damage to more delicate components and may get dead pixels
How does damage to film often present as
black marks due to sensitization of radiographic emulsion
however may appear white if emulsion is scraped off
What may marks on film represent
nail marks
bite marks
finger prints
What is a step wedge
one type of test object used to check image quality and contrast
self made or provided by manufacture
What is a step wedge made of
overlapping layers of lead
How do you use a step wedge
expose to a normal clinical exposure
compare image ot baseline
carry out regularly
What is the aim of QA of clinical image quality
ensure radiographs are consistently adequate for diagnosis
What are the 3 parts of QA of clinical image quality
image quality rating
image quality analysis
reject analysis
What is image quality rating
grading each image
What is image quality analysis
reviewing images to calculate success rate and identify any trends for suboptimal images
carried out periodically (every 4 months you review the last 150)
What is reject analysis
recording and analysing each unacceptable image
What is the quality ratings
diagnostically acceptable
diagnostically unacceptable
What is diagnostically acceptable
no errors or minimal either in either px prep, exposure, positioning, image processing, image reconstruction and sufficient image quality to answer clinical q
What is diagnostically unacceptable
errors in the list from before meaning image can’t be used for diagnosis
shouldn’t be greater than 5% in digital and 10% in film
What do we look at to know if image answers our Qs
which tooth/teeth
which parts of tooth/teeth
what other structures
what extent of pathology
What do the question answers depend on
type of radiograph taken
clinical justification for it
What are diagnostically acceptable poisoning factors for bitewings
show entire crowns of upper and lower teeth
include distal aspect of fore standing standing posterior teeth and mesial aspect of last standing tooth
may require more than 1
every approximal surface shown at least once without overlap where possible
What are diagnostically acceptable poisoning factors for PA
shows entire root
shows PA bone
shows crown
What must radiograph have in addition to correct positioning factors
adequate contrast
sharpness
resolution
as well as minimal distortion
What is fault analysis
identifying and explaining fails so can be remedied
What are potential faults visible on image
too dark or pale inadequate contrast unsharp distorted over collimated receptor marks or damage
What are potential faults in collimation error
incorrect assembly or receptor holder
incorrect alignment between x ray tube and receptor holder
incorrect orientation of rectangular collimator (attached to x ray unit)
What are potential faults in incorrect image radio density
image too dark or light
What are potential causes of incorrect radio density
exposure factors
developing factors (FILM)
viewing factors
What are the exposure factors
incorrect exposure settings, patients tissues too thick, faulty timer on x-ray unit
What are developing factors (film)
incorrect duration, incorrect temp, incorrect conc
What are viewing factors
inappropriate light source (film), inappropriate display screen (digital)
excessive environmental light
