Characterization of a GaAs photon counting detector for mammography

The purpose of this study was to evaluate the performance of mammography images acquired with a prototype Gallium Arsenide (GaAs) photon counting detector. The contrast to noise ratio was measured using different aluminum/PMMA phantoms of different thicknesses. In addition, microcalcification detection accuracy was evaluated using a receiver operating characteristic (ROC) study with three observers reading an ensemble of images for each case. For both studies, comparisons were made to a commercial mammography system. The contrast to noise ratio was estimated by imaging 18, 36 and 110 μm thick aluminum targets placed on top of 6 cm of PMMA plates and was found to be similar or better over a range of exposures. Similar task performance in detecting microcalcifactions was observed between the systems over a range of clinically applicable dose levels with a small increase in GaAs’s system at lower dose levels. The GaAs system was evaluated using a typical mammography X-ray spectrum provided by the Automatic Exposure Settings (AEC) of the commercial mammography system and using only one energy threshold (i.e, one energy window). Operating the GaAs detector with multiple energy windows (i.e., two energy windows) may provide improved performance for a given dose.