In digital mammography noise characteristics are measured in quality control procedures. In the European Guidelines a
method of measurement to investigate noise in digital mammography systems was proposed to evaluate the presence of
additional noise beside quantum noise. However this method of noise analysis does not discriminate sufficiently between
systems with and without additional noise. Therefore a different noise analysis is proposed. In this analysis the noise of a
digital system is subdivided into three components: electronic, quantum and structured noise and the noise dose
dependency of these components is studied. The usefulness of this analysis in both the frequency and spatial domain is
investigated on a number of DR and CR systems.
The results show that large differences between digital mammography systems exists. Some systems do have a large
range in detector dose for which quantum noise is the largest noise component. For one system however, electronic and
structured noise are more dominant. In addition to the differences between systems smaller differences in noise
characteristics exist between different target-filter combinations on a particular system. These differences might be
attributed to the limited flatfield calibration, the heel effect and difference in sensitivity. The noise analysis in both the
frequency and spatial domain give useful information about the noise characteristics of systems. The analysis in the
spatial domain is relatively easy to perform and to interpret. This analysis might be suitable for QC purposes. The
analysis in the frequency domain does give additional information and might be used for thorough investigations.