Clinical audit

    Audit sample: the quality of radiographs

    Applies to: All
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    Last reviewed: 20/03/2013
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    Last updated: 02/06/2008
    Why audit radiographs?

    Both the current regulations for the use of ionising radiation for medical and dental purposes (IRR99 and IR(ME)R2000) place a legal responsibility to establish and maintain quality assurance programmes in respect of dental radiology. As part of this, it is necessary to ensure the consistent quality of radiographs through audit. Radiographs must be justified and will only benefit patients if they lead to the correct treatment decision using the minimum radiation dosage. Image quality is important and, if poor, can compromise an accurate diagnosis. It should be remembered that, although individual patient dose may be low, dental radiographs represent one of the most frequently undertaken radiological investigations in the UK.

    There is a need to minimise or eliminate

    • Radiographic examinations where the results are unlikely to affect patient management and/or prognosis
    • Radiographic examination which are repeated unnecessarily
    • Duplication of radiographic examinations which have been done already
    • Inappropriate radiographic examinations
    • Avoidable lapses in quality assurance which impact on patient dose and care
    An audit of dental radiography can encompass:
    • Structure, by evaluating your own facilities against the standards laid down in the publication Guidance Notes for Dental Practitioners on the safe use of x-ray equipment (DH/NRPB, 2001)
    • Process, by examining what was done, for instance whether the correct exposure time was set or the radiographs properly processed
    • Outcome, by looking at the diagnostic yield or treatment decisions. This might include, for example, using radiographs to assess the extent of dental caries and the impact on the decision to restore the affected teeth
    • Image quality, looking at patient preparation, positioning, exposure, processing and film handling
    Aims and objectives

    This sample audit is specifically looking at image quality. In the process, we aim to monitor, improve and maintain quality of radiographic techniques, processing and storage of small radiographs.

    Suggested source materials
    The proposed standard

    85 per cent of small radiographs will be clinically acceptable, as defined below:

    A bitewing radiograph (conventional film) is clinically acceptable if it meets 10 of the following 12 criteria:

    1. Mesial 8 to distal 4 visible
    2. Cusps superimposed
    3. No proximal overlap
    4. 3mm of crestal bone visible
    5. No uneven distortion
    6. No coning-off
    7. Good contrast
    8. Correct exposure
    9. No bend or fold marks
    10. No processing artefacts
    11. No chemical staining
    12. Correctly labelled, dated and stored

    A periapical radiograph (conventional film) is clinically acceptable if it meets 9 of the following 11 criteria:

    1. 3mm of bone visible around apex
    2. Whole tooth visible on film
    3. No proximal overlap, unless intended
    4. No uneven distortion 
    5. No coning-off 
    6. Good contrast 
    7. Correct exposure
    8. No bend or fold marks 
    9. No processing artefacts 
    10. No chemical staining 
    11. Correctly labelled, dated and stored

    Note : for practitioners using digital radiography, the criteria relating to processing errors are replaced by those relating to digital imaging errors on the data collection sheets.

    The process

    First, it might be a good idea to discuss the audit with your staff. Staff members may wish to be involved in the project and can help you with the data collection and its recording. This project could be run as a collaborative audit, allowing you to compare your results with those of other dentists or team members in the practice. 

    We suggest that you audit retrospectively 50 bitewings and 50 periapicals, selected at random. Record your findings on a data collection sheet (below) and analyse them.

    The findings can then be taken to another staff meeting, where you set an action plan to improve the quality. Carefully note the action plan and ensure everyone involved acts on it.


    Data collection sheets are provided below in Excel format. Choose the appropriate data collection sheet(s) for your audit from the four provided. Select 0 for a fail or 1 for a pass in the green section and type any data into the blue sections. The calculations are done automatically and a graph is also produced automatically on the second sheet.

    Analyse your results by scoring each radiograph. Establish the totals and the percentage that have fulfilled the criteria. You can then compare that percentage to the standard set and identify any areas for improvement.

    Changes should be made to address areas identified as requiring improvement.


    Around six months after initiating your procedural changes, run your second audit cycle of 50 bitewings and 50 periapicals of patients seen since that time. Record your findings on a data collection sheet and analyse it. Hold another staff meeting to discuss the results. If the standard has been exceeded, consider either re-auditing in a year’s time to ensure that the standard is still being met, or raising the standard further through instituting further changes, and auditing again after a set period of time.

    Keeping the audits

    Audit is part of your clinical governance responsibilities, and your primary care organisation may wish to see proof of compliance with this requirement. You should keep the results of your audit for at least two years. Keeping them with your radiation protection file ensures all your radiation protection information for the practice is together in one place. It is a legal requirement to re-audit at least every 12 months.