Quality Assurance and Fault Analysis Flashcards
What aspects should quality assurance cover?
- procedures (e.g. risk assessment, local rules, contingency plans etc.)
- staff training
- x ray equipment
- patient dose
- image processing
- display equipment
- image quality
Who should a quality assurance programme be created with input from?
a medical physics expert
When should a digital image receptor be checked for quality assurance?
on a regular basis
for example every 3 months (or sooner if an issue is suspected)
What things should be checked when assesing a digital image receptor?
- the receptor itself
- image uniformity
- image quality
How is the receptor itself checked for quality? (digital image receptors)
check for visible damage to casing/wiring
check if clean (no congealed disinfectant/saliva)
How is the image uniformity checked for quality? (digital image receptors)
expose receptors to an unattenuated x ray beam and check if resulting image is uniform (i.e. should show a consistent shade of grey across the whole image)
How is the image quality checked ? (digital image receptors)
take a radiograph of a test object and assess teh resulting image against a baseline
(receptor damage affecting image) what happens if the phosphor plates have scratches?
white lines
(receptor damage affecting image) what happens if the phosphor plates have cracking from flexing?
network of white lines
(receptor damage affecting image) what happens if the phosphor plates have delamination?
white areas around edge
i.e. separation of phosphor layer from base plate
(receptor damage affecting image) what happens if the solid state sensors have sensor damage?
white squares/straight lines
What damage do the red, yellow, green and blue arrows indicate is wrong with the receptor?
red- scratches to phosphor plate
yellow- cracking from flexing of the phosphor plate
green- delamination of phosphor plate
blue- sensor damage to the solid-state sensor
(receptor damage affecting image) what happens if the film has damage to it?
the damage is often appears as a black mark due to sensitisation of radiographic emulsion
however, may appear white is emulsion is scraped off
What has caused these marks?
Nail scratching
What has caused the marking in the blue circle
delamination
What can be used to check image quality/contrast? And how often should this be carried out
A Step wedge
Can be self made using overlapping layers of lead foil (e.g. 6 different layers of thickness) or provided by manufacturer
Exposed to a normal clinical exposure
This must be compared to a baseline
“must be able to differentiate all 6 steps)
SHOULD be carried out regularly, e.g. every morning
What is the aim of QA of quality assessment of clinical image quality
aims to ensure that radiographs are consistently adequate for diagnostic purposes
What are the 3 parts of the QA of clinical image quality?
-image quality rating
- image quality analysis
- reject analysis
What is meant by image quality rating?
grading each image
what is meant by image quality analysis?
- reviewing images to calculate “success rate” and identify any trends for suboptimal images
- carried out periodically (e.g. every 4 months you review the last 150 images)
What is meant reject analysis for QA of clinical image quality
recording and analysis each unacceptable image
What is the target percentage of radiographs or CBCT images in sample for diagnostically acceptable quality rating? (digital imaging and film imaging)
- Digital Imaging , NOT less than 95%
- Film Imaging , NOT less than 90%
What is the target percentage of radiographs or CBCT images in sample for diagnostically NOT acceptable quality rating? (digital imaging and film imaging)
- Digital Imaging , NOT greater than 5%
- Film Imaging , NOT greater than 10%
What things should an image show in order for it to be considered diagnostically acceptable?
Which tooth/teeth
what parts of the tooth/teeth
what other structures?
what extent of the pathology?
What are the diagnostically acceptable positioning factors for bitewing radiographs ?
show entire crown of upper and lower teeth
include distal aspect of the canine and mesial aspect of the last standing tooth
every approximal surface shown at least once without overlap (where possible)
Must also have adequate contrast, sharpness and resolution as well as minimal distortion
What are the diagnostically acceptable positioning factors for periapical radiographs ?
shows entire root
shows periapical bone
shows crown
Must also have adequate contrast, sharpness and resolution as well as minimal distortion
What faults can be present on the image itself?
- too dark/too pale
- inaqeduate contrast
- unsharp
- distorted
- over collimated
- receptor marks/damage
Name 3 potential faults due to a collimation error (“cone cutting”)
- incorrect assembly of receptor holder
- incorrect alignment between x-ray tube and receptor holder
- incorrect orientation of the rectangular collimator
What 3 main things may cause incorrect image radiodensity?
- exposure factors
incorrect exposure settings, patient’s tissues too thick, faulty timer on X-ray unit
- developing factors(film)
Incorrect duration, incorrect temperature, incorrect concentration
- viewing factors
Inappropriate light source (film), inappropriate display screen (digital), excessive environmental light
What is the main purpose of quality assurance of radiographic imaging?
to ensure radiographs are consistently diagnostic and that your patients are not exposed to unnecessary radiation
