Quality Assurance & Fault Analysis of Radiographs Flashcards
What is the purpose of quality assurance?
The purpose of quality assurance (QA) in dental
radiology is to ensure consistently adequate
diagnostic information, whilst radiation doses to
patients (and other persons) are kept ALARP,
taking into account the relevant requirements of
IRMER17 and IRR17
What aspects should quality assurance cover?
• Procedures (e.g. risk assessments, local rules, contingency plans, etc.)
• Staff training
• X-ray equipment
• Patient dose
• Image processing
• Display equipment
• Image quality
When should digital receptors be checked and what are the things to check?
Should be formally checked on a regular basis
• e.g. every 3 months (or sooner if issue is suspected)
• Things to check
1. The receptor itself
2. Image uniformity
3. Image quality
What to check in each of the digital receptors?
- The receptor
• Check for visible damage to casing/wiring
• Check if clean (e.g. no congealed disinfectant/saliva) - Image uniformity
• Expose receptor to an unattenuated X-ray beam & check if resulting image is uniform
(i.e. should show a consistent shade of grey across the whole image) - Image quality
• Take a radiograph of a test object & assess the resulting image against a baseline
What can be damaged in the receptor resulting in the image being affected?
Phosphor plates
• Scratches → white lines
• Cracking (from flexing) → network of white lines
• Delamination → white areas around edge
• i.e. separation of phosphor layer from base plate
Solid-state sensors
• Sensor damage → white squares/straight lines
Film
• Damage often appears as black marks due to
sensitisation of radiographic emulsion
• However, may appear white if emulsion is scraped off
What is a step wedge?
A step wedge is one type of test object used to check image quality/contrast
• Self-made or provided by manufacturer
How is a step wedge used?
Exposed to a normal clinical exposure (e.g. adult mandibular molar periapical)
& resulting image is compared to a baseline
• Baseline example: “Must be able to differentiate all 6 steps”
• Carried out regularly (e.g. every morning)
What are the aims of QA clinical image quality?
Aims to ensure that radiographs are consistently adequate for diagnostic purposes
What are the 3 parts of QA clinical image quality?
Consists of 3 parts
1. Image quality rating
• Grading each image
- Image quality analysis
• Reviewing images to calculate “success rate” & identify any trends for suboptimal images
• Carried out periodically (e.g. every 4 months you review the last 150 images) - Reject analysis
• Recording & analysing each unacceptable image
What are the diagnostically acceptable positioning factors for bitewing radiographs?
• Show entire crowns of ↑ & ↓ teeth
• Include distal aspect of the canine, & mesial aspect
of the last-standing tooth
• May require >1 radiograph
• Every approximal surface shown at least once
without overlap (where possible)
• May be impossible if crowding
What are the diagnostically acceptable positioning factors for periapical radiographs?
• Shows entire root
• Shows periapical bone
• Shows crown
What are potential faults visible on image?
• Too dark or pale (N.B. may be possible to correct if digital)
• Inadequate contrast
• Unsharp
• Distorted
• Over-collimated
• Receptor marks/damage
How do collimation errors occur? (Cone cutting)
- incorrect assembly of receptor holder
- incorrect alignment between x-ray tube and receptor holder
- incorrect orientation of the rectangular collimator
What are the potential causes of incorrect image radiodensity?
• Image too dark or too light
• Many potential causes
• 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
