Quality Assurance & Fault Analysis of Radiographs

Question 1

What is the purpose of quality assurance in dental radiology?

Answer 1

to ensure consistently adequate diagnostic information, while radiation doses to patients and other persons are kept ALARP taking into account the relevant requirements of IRMER17 and IRR17

Question 2

What is a quality assurance programme?

Answer 2

• necessary in every dental practice/hospital
• should cover all aspects of using radiographs
  
  • procedures
  • staff training
  • x-ray equipment
  • patient dose
  • image processing
  • display equipment
  • image quality
• created with input from medical physics expert
  
  • role defined in IRMER17

Question 3

What does quality assurance of digital image receptors involve?

Answer 3

• digital receptor are reusable so experience wear and tear
  
  • eventually impacts on image quality
  • necessitates replacement
• should be formally checked on a regular basis
  
  • every 3 months
  • sooner if issue is suspected
• things to check
  
  • receptor itself
    - check for visible damage to casing/wiring
    - check if clean (no congealed disinfectant or saliva)
  • image uniformity
    - expose receptor to unattenuated x-ray beam
    - check if resulting image is uniform
  • image quality
    - take radiograph of a test object
    - assess resulting image against baseline

Question 4

How does receptor damage affect an image?

Answer 4

• phosphor plate
  
  • scratches
    - white lines
  • cracking
    - from flexing
    - network of white line
    - cracking along phosphor layer
    - usually at edge or corner
  • delamination
    - white areas around edge
    - separation of phosphor layer from base plate
• solid state sensory
  
  • sensor damage
    - white squares caused by dead pixels
    - white straight lines
• film
  
  • usually appears as black marks due to sensitisation of emulsion
  • white if emulsion is scraped off
  • nail marks
  • bite marks
  • fingerprints

Question 5

What is a step wedge used for in quality assurance of receptors?

Answer 5

• step wedge used to check image quality and contrast
• spotted to a normal clinical exposure and image compared to baseline
  • baseline example must be able to differentiate all 6 steps
  • carried out regularly
    - every morning

Question 6

What does quality assurance of image quality involve?

Answer 6

• ensures radiographs are consistently adequate for diagnostic purposes
• 3 parts
  
  • image quality rating
    - grading each image
  • image quality analysis
    - reviews image to calculate success rate
    - identify trends for suboptimal images
    - carried out periodically (every 4 months review last 150)
  • reject analysis
    - recording and analysing each unacceptable image
• action must be taken if non-diagnositic images are occurring too frequently or if the same issue keeps arising

Question 7

What is the quality assurance for clinical image quality?

Answer 7

• quality rating
  
  • diagnostically acceptable
    - A
    - no/minimal errors
    - digital imaging successful in at least 95%
    - film imaging successful in at least 90%
  • diagnostically unacceptable
    - N
    - errors
    - digital imaging non successful in less than 5%
    - film imaging non successful in less than 10%

Question 8

What must be considered concerning clinical image quality?

Answer 8

• to determine whether diagnostically acceptable consider:
  
  • which tooth/teeth?
  • what other structures?
  • what extent of the pathology?
• variable depending on:
  
  • type of radiograph
  • clinical justification for radiograph

Question 9

What is considered diagnostically acceptable for a bitewing?

Answer 9

• entire crowns of upper and lower teeth visible
• includes distal aspect of canine and medial aspect of last tooth
  
  • may require more than one radiograph
• every approximate surface shown at least once without overlap
  
  • where possible
  • may be impossible due to crowding
• adequate contrast, sharpness, resolution and minimal distortion

Question 10

What is considered diagnostically acceptable for a periapical?

Answer 10

• shows entire root
• shows periodical bone
• shows crown
• adequate contrast, sharpness, resolution and minimal distortion

Question 11

What is fault analysis?

Answer 11

• identifying and explaining faults so they can be remedied
• potential faults visible on image
  • too dark or too pale
  • inadequate contract
  • unsharp
  • distorted
  • over-collimated
  • receptor marks/damage

Question 12

What is cone cutting?

Answer 12

• collimation error
  
  • incorrect assembly of receptor holder
  • incorrect alignment between X-ray tube and receptor holder
  • incorect orientation of rectangular collimator

Question 13

What is incorrect image radio density?

Answer 13

• image too dark or too light
• many potential causes
  • exposure factors
    - incorrect exposure settings
    - patient’s tissue too thick
    - faulty timer on x-ray unit
  • developing factors
    - incorrect duration
    - incorrect temperature
    - incorrect concentration
  • viewing factors
    - inappropriate light source (film)
    - inappropriate display screen (digital)
    - excessive environmental light