[Bavarian mammography screening: results of consistency tests in X-ray units over three months]

To find out whether the quality requirements in daily, weekly or monthly tests of the "European protocol for the quality control of the physical and technical aspects of mammographic screening (EPQC)" can be maintained when screening the population of a large area. Furthermore, to check the specific tolerances of different test positions given by the EPQC for redundancy and statistical correlation.

Daily test images were obtained with an additional exposition of a sensitometric step wedge according DIN 6868 - 2. Weekly densitometry and visual inspection were performed at the University of Applied Sciences, Cologne.

All units were able to maintain basic requirements on image quality as long as films of the same batch number were used. Some tolerance requirements of the EPQC are inconsistent and redundant.

The occasionally considerable fluctuations of film processing require a daily check on the processing conditions. Daily test images of the units are only obligatory in the first 4 to 5 weeks of a new operation. All test results should be analyzed retrospectively in an independent test laboratory with emphasis on the statistical behavior of the unit. The tolerances prescribed by the EPQC are not always consistent and should be adapted to today's scientific standard when applied in mammography screening centers.