Room: Room 207
Purpose: To evaluate data from mammography surveys over a 17-year interval in order to identify trends and anomalies in system performance.
Methods: From 382 annual surveys of mammography systems, we collected data on the measured average glandular dose (AGD), AGD displayed by the system, the percent difference between measured and displayed AGD (%AGD discrepancy), image quality, and reasons for survey failure. Image quality was defined as scored visible fibers, specks, and masses in the mammography accreditation phantom. These data encompassed screen-film, digital, and digital breast tomosynthesis systems across four vendors between 2001 and 2018. Pearson correlations were calculated between collected data and survey year to determine potential trends.
Results: Excluding 3D combo imaging, measured and displayed AGD decreased linearly with survey date (r=-0.61, p<0.01 and r=-0.30, p<0.01, respectively). AGD decreased 31% between the first three years included in the study and the last 3 years. Including 3D combo imaging, AGD increased 4.3%. The %AGD discrepancy decreased linearly with survey date (r=-0.35, p<0.01). In 2013, the displayed dose changed from tending to be lower than the measured dose to being higher. Overall, the RMS %AGD discrepancy was 12%. Image quality initially decreased during the first four years of the study, increased over the following eight years, and then plateaued. 19% of surveys failed due to collimation, 11% from artifacts, 5% from AEC, and <5% from each of the other failure modes. Survey failures from both artifacts and collimation errors decreased linearly with survey year (r=-0.51, p<0.01 and r=-0.62, p<0.01, respectively).
Conclusion: From 2001 to 2018, the data demonstrate trends of lower dose per image, increased image quality, and decreased survey failures from artifacts and collimation. The correlations do not identify the causes behind these trends, which could be due to better machine performance or changes in methods/equipment used in performance evaluations.