Reference levels for image quality in mammography.

Diagnostic reference levels are a well-established tool for optimisation in diagnostic radiology. A dose-reference level for certain diagnostic procedures, meant to identify practices with unusually high doses, is usually set at the third quartile of the distribution of doses in different diagnostic centres. If image quality is somehow quantified, the same 'worst quarter' principle can also be used to identify practices with less than optimal performance in terms of image quality. In Slovenia, the performance of mammographic centres is evaluated annually. Technical testing includes average glandular dose determination and evaluation of technical image quality using the image of a mammographic phantom. From the phantom image, simple image quality parameters are derived and for some of them reference levels can be established. In this study, the results from ten years of testing (1996--2006) at mammography centres are presented and the usefulness of reference levels is evaluated.