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Image quality analysis

This article focuses on how to ensure image quality is of an appropriate level to meet QA standards, and how to take corrective action.

The purpose of a QA programme for image quality is to ensure the consistent production of radiographs of adequate quality for diagnostic purposes and to minimise the number of repeat radiographs.

This contributes to keeping patient doses as low as reasonably practicable.

The Dental GNs recommend that a two-point grading system be used to assess image quality, as seen in the extract below. Suggested target values are also shown.

Table 5.2 from the Dental GNs. This is titled 'subjective image quality ratings of dental radiographs and CBCT images' and must be completed with the 'Quality rating', the 'Basis' for this rating, and the target percentage of radiographs or CBCT images in sample

In some cases, for example, where a practice has a large proportion of patients with additional needs, these targets may not be achievable.

In this case, the practice may set its own targets in consultation with the MPE.

Audits of image quality

The QA programme should include regular audits to ensure image quality meets the set performance targets. This can be either:

  • A prospective study – image quality ratings are assigned and recorded for all radiographs as they are being viewed
  • A retrospective study – a suitable representative sample of radiographs is drawn from clinical records at regular intervals, the image quality ratings are assigned and recorded, and the results analysed.

The analysis should be undertaken by someone who has been adequately trained in taking radiographs. The Dental GNs recommend that an audit should be carried out at least every 6 months with a sample size of at least 100 radiographs unless the workload is too low to support this number.

Each modality (eg intra-oral, panoramic etc) should be treated separately and a record of each analysis should be kept, assist in spotting trends over time.

Reject image analysis and corrective action

The guidance also recommends that further analysis of any images in the quality category ‘N’ (diagnostically unacceptable) is carried out. A record, including the information below, of the analysis, should be kept.

  • Date
  • Nature of the deficiency
  • The known or suspected cause of the deficiency
  • Number of repeat radiographs/images taken
  • Corrective action taken

Again, this record should help to identify trends; for example, if it is the same operator that routinely causes the deficiency it may indicate that further training is required.

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Dental Radiography: Radiation Protection in Dental Practice

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