Comprehensive dose survey of breast screening in Ireland.

The primary purpose of this study was to evaluate the impact of digital mammography screening on breast dose by analysing the results of a patient dose survey of the Irish breast screening programme. Results from the survey were used to determine a dose reference level for the screening programme. Approximately, 100 examinations were acquired for each of the digital mammography systems operational in the screening programme. Each examination consisted of two standard views of each breast. The mean glandular dose for each acquired image was calculated. The dose reference level was established by calculating the 95th percentile of the average mean glandular dose for the average compressed breast thickness of the mediolateral oblique views. The overall average mean glandular dose per examination was 2.72 ± 0.04 mGy. The average compressed breast thickness was 61.4 ± 0.03 mm. The average compression force was 109 ± 7 N. A dose reference level value of 1.75 mGy was established for the screening programme. The results of this clinical dose survey provide a valuable indication of the dose performance of modern full field digital mammographic imaging systems. The results demonstrate clearly the dose benefits of digital mammography. The dose benefit of digital screening was further demonstrated by the establishment of a comparatively lower diagnostic reference level for the screening programme. The comparison of the dose performance of individual X-ray systems with the diagnostic reference level highlights the need for more optimisation within the service.