Quality Assurance and Fault Analysis

Question 1

What is the purpose of quality assurance in dental radiology?

Answer 1

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

Question 2

The quality assurance programme is necessary in every dental practise. IT should cover all aspects of using radiographs including what?

Answer 2

Procedures (e.g. risk assessments, local rules, contingency plans, etc.)

• Staff training
• X-ray equipment
• Patient dose
• Image processing
• Display equipment
• Image quality

Question 3

The quality assurance programme in dental practises should be created with input from who?

Answer 3

A medical physics expert

Question 4

Why should digital image receptors be checked?

Answer 4

because they are reusable therefore wear and tear (and mishandling) will eventually impact the image quality and necessitate replacement

Question 5

How often should digital receptors be checked?

Answer 5

formally checked every 3 months or sooner if an issue is suspected

Question 6

What 3 main things needed to be checked with digital receptors?

Answer 6

• the receptor itself
• image uniformity
• image quality

Question 7

What do you want to check about the receptor itself? (digital image receptors)

Answer 7

• check for visible damage to the casing/wiring (Not overly bent
• no creases)
• check if clean e.g. no congealed disinfectant from not being dried off properly and no saliva

Question 8

How do you check the image uniformity when checking digital receptors?

Answer 8

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)

Question 9

How would you check the image quality of a digital image receptor?

Answer 9

Take a radiograph of a test object & assess the resulting image against a baseline

Question 10

What damage can be seen on phosphor plate receptors? How do they show up?

Answer 10

• Scratches  white lines (can be quite large. Shown by red arrows)
• Cracking (from flexing)  network of white lines (yellow arrow - due to bending within the mouth etc)
• Delamination  white areas around edge
• i.e. separation of phosphor layer from base plate - shown by green arrow. Mishandling or drying out

Question 11

How will damage show up on solid state sensors?

Answer 11

• white squares/straight lines
• Don’t get as much damage with SS but can damage more sensitive parts in it
• can get digital components failing and get dead pixels (can get single pixels failing or a full line making the white line)

Question 12

How does damage to film receptors tend to show up?

Answer 12

as black marks due to sensitisation of radiographic emulsion (sensitised by light or presssure etc rather than x-rays)

However, they may appear white if the emulsion is scraped off

Question 13

Marks on film receptors may represent what?

Answer 13

-nail marks, bites, fingerprints etc

(can lightly scrath the emulsion to make it black by sensitising the crystals. The same goes for the fingerprints)

Question 14

What is a step-wedge and how is used in quality analysis of radiographs?

Answer 14

Is a type of test object used to check the image quality/contrast

It uses overlapping layers of lead foil

The step-wedge is exposed to normal clinical exposure and compared to a baseline (have to see all 6 steps)

Question 15

What is the aim of quality analysis of clinical image quality?

Answer 15

To ensure that radiographs are consistently adequate for diagnostic purposes

Question 16

QA of clinical image quality consists of what 3 parts?

Answer 16

1. Image quality rating
   
   • grading each image
2. Image quality analysis
   
   • reviewing images to calculate ‘success rate’ and identify any trends for suboptimal images
   • Carried out periodically
3. Reject analysis
   
   • Recording and anylysing each unacceptable image

Question 17

What should happen if non-diagnostic images are occuring too frequently or if the same issue keeps arising?

Answer 17

Take action and figure out whats going wrong and sort it

Question 18

What are the grades for radiographic analysis? (new)

Answer 18

Diagnostically acceptable

Diagnostically not acceptable

Question 19

What does diagnostically acceptable mean?

Answer 19

No errors or minimal errors in either patient preparation, exposure positioning, image (receptor) processing or image reconstruction and of sufficient image quality to answer the clinical question

Question 20

What does diagnostically not acceptable mean?

Answer 20

errors in either patient prep, exposure, positioning, image receptor processing, or image reconstriction which render the image diagnostically not acceptable

Question 21

What are the target percentages for radiographs that are DA? (both film and digital receptors)

Answer 21

digital imaging - no less than 95%

film imaging - no less than 90%

Question 22

What should you be able to see in a bitewing radiograph?

Answer 22

• entire crowns of upper and lower teeth
• include distal aspect of the forestanding posterior tooth and mesial aspect of the last standing tooth (may need more then 1 radiograph)
• every approximal surfcae shown at least once without overlap (where possible e.g. not with crowding)

Note: must also have adequate contrast, sharpness and resolution, as well as minimal distortion

Question 23

What should you be able to see in a periapical radiograph?

Answer 23

• entire root
• periapical bone
• crown

Question 24

What are some potential faults that you may see?

Answer 24

• too dark or too pale
• inadequate contrast
• unsharp
• distorted
• over-collimated (collimator error)
• receptor marks/damage

Question 25

Describe cone cutting and how it might happen.

Answer 25

Is when part of the image is cut off

• incorrect assembly of the receptor holder
• incorrect alignment between x-ray tibe and receptor holder
• incorrect orientation of the rectangular collimator

Question 26

Why might an image be too dark or too light?

Answer 26

Many potential causes:

• exposure factors
  
  • Incorrect exosure settings, patients skin too thick, faulty timer on X-ray unit
• Developing factors (film)
  
  • Incorrect duration, incorrect temp, incorrect conc
• Viewing factors
  
  • Inappropriate light source
  • inappropriate display screen
  • excessive environmental light