Dental Radiography · NEBDN certificate
Faults and Quality Assurance
Image quality rating, positioning, exposure and processing faults, QA testing and reject analysis.
Deciding whether an image is good enough, and finding out why when it is not. The heaviest block is image quality rating on the two-point A and N scale, which the assessment tests precisely because it replaced an older three-point scale that many people still half-remember. Around it sit the faults themselves — positioning, exposure, processing and receptor — what each one looks like on the resulting image, and the routine QA testing, in-house checks, audits and reject image recording that are meant to catch them before a patient is re-exposed.
What this topic covers
These are the sub-topics the app's 45 questions for this topic are grouped into, with the number of questions on each. They are a fair map of where the weight sits.
| Sub-topic | Questions |
|---|---|
| Image quality rating: the two-point A and N scale | 10 |
| EMQ: Panoramic positioning and preparation faults | 6 |
| EMQ: Quality assurance tests and analyses | 6 |
| EMQ: Receptor and processing fault causes | 6 |
| Image quality analysis and reject image recording | 5 |
| Routine QA testing, in-house checks and audits | 5 |
| Positioning faults and their appearance | 4 |
| Exposure, processing and receptor faults | 3 |
Sub-topics beginning “EMQ” are extended matching questions: one stem, one right answer, and a list of up to 9 options to choose it from. They are testing whether you can discriminate between neighbouring answers, not whether you recognise the right one.
Study guide
The quality topic, and the one with a specific trap in it. Image quality rating uses a two-point scale — acceptable and not acceptable — and a great many people still half-remember a three-point scale from older guidance. The bank tests that difference directly, and it is the single highest-value thing to get right in this topic.
Image quality rating
The largest block of questions in the topic. Learn the current scale, and learn that it is current.
- The two-point A and N scale classifies an image as acceptable or not acceptable — there is no middle grade to reach for.
- What makes an image not acceptable is defined by whether it answers the clinical question, not by whether it is aesthetically good.
- If you were taught a three-point scale, actively unlearn it: questions are written so that the old middle grade is an attractive wrong option.
Positioning faults and their appearance
Each positioning error produces a characteristic appearance, and the assessment works backwards from the appearance.
- Learn faults as appearance-to-cause pairs, because that is the direction the extended matching questions run in.
- Panoramic positioning faults have their own named appearances and are examined as a set of their own.
- The same appearance can have more than one possible cause; read the stem for the detail that discriminates.
Exposure, processing and receptor faults
Faults that are not about where the patient was, but about what happened to the image afterwards.
- Exposure faults, processing faults and receptor faults produce different appearances and have different remedies.
- Extended matching questions on receptor and processing fault causes are common — practise naming the cause from the described image.
- Digital and film workflows fail in different ways; check which the stem describes.
Quality assurance and reject analysis
The programme that turns individual faults into a corrected process.
- Routine QA testing, in-house checks and audit each have a role, and questions ask which one a described activity belongs to.
- Reject image recording exists so that repeated faults are detected as a pattern rather than one at a time.
- Image quality analysis feeds back into technique — the link between the fault and the corrective action is the examinable part.
In the exam Two things carry this topic: the two-point quality scale, and the ability to name a fault from a described appearance. Drill the appearance-to-cause direction specifically, because recognising a fault when you see it is not the same skill as naming it from a written description, and the assessment can only test the second one.
This topic's questions are in the app
The free tier does not unlock any of the 45 questions for this topic, so there is no quiz to run here — and publishing one anyway would give away more than the app itself does. The study guide above is free to read in full.
To practise this topic, get the app. Or start with one of the topics that are free here .
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Revise anywhere, with the whole Radiography & Post-Reg bank
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