Breast density measurement in full-field digital mammography: System calibration and stability

Abstract

Breast density calibrations and stability measurements were undertaken on digital mammography systems to investigate whether a single calibration could be used for extended periods. The results indicated that the calibration did not change over time and was the same for two units investigated. The daily mean pixel value per mAs (MPV/mAs) for five systems was recorded over 22 months and showed varying periods of stability up to more than a year. However, step changes in MPV/mAs were noted and resulted from, for example, detector re-calibration or replacement. During stable periods the MPV/mAs for the static units varied mostly by