Clinical image quality should be assessed and compared against performance targets as part of the Employer’s quality assurance programme. The analysis of images should be carried out by an operator who is trained and experienced in taking the type of radiograph being assessed.
Radiographs can be categorised for image quality [1] as follows:
A = Diagnostically acceptable. 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.
N = Diagnostically not acceptable. Errors in either patient preparation, exposure, positioning, image (receptor) processing or image reconstruction which render the image diagnostically unacceptable.
Radiographs can be evaluated prospectively by rating according to the above criteria and recording the rating as they are being viewed, or retrospectively by drawing a suitably representative sample of radiographs from clinical records at regular intervals and rating the image quality as above.
It is recommended that the quality ratings of radiographs are regularly analysed to determine the percentage of the total images produced that are categorised as A or N (see Quality Assessment of Radiographic Images template). Analysis should be carried out at least every six months and the sample size should include at least 100 images [1]. When using more than one type of radiograph e.g. intra oral and panoramic images, results should be reported separately.
The target percentages of images rated as diagnostically acceptable are:
- Digital images – not less than 95%
- Film images – not less than 90%
It is also recommended that day-to-day surveillance of image quality be maintained to allow any significant deterioration in quality to be detected and investigated in a timely manner.
Include as part of your quality assurance programme a clearly defined method of ensuring that the image quality of radiographs is rated, targets are set and results analysed and recorded to allow comparison with your targets.
If radiographs are rated as a ‘N’ (diagnostically unacceptable), provide a description of the fault and the possible cause so that this can be rectified.
- The description should include the date, nature of deficiency, known or suspected cause of the deficiency and the number of repeat radiographs required, if any.
- The analysis of rejected images should be undertaken every six months, during the image quality analysis.
- A list of common faults seen in conventional dental radiographs and dental CBCT images can be found in the ‘Guidance Notes for Dental Practitioners on the Safe Use of X-ray Equipment’ [1].