Performance of advanced a-Si/CsI-based flat panel x-ray detectors for mammography

The GE Senographe 2000D(TM), the first full field digital mammography system based on amorphous Silicon (a-Si) flat panel arrays and a Cesium-Iodide (CsI) scintillator, has been in clinical use for several years. The purpose of this paper is to demonstrate and quantify improvements in the detective quantum efficiency (DQE) for both typical screening and ultra-low exposure levels for this technology platform. A new figure of merit, the electronic noise factor, is introduced to explicitly quantify the influence of the electronic noise, conversion factor, modulation transfer function (MTF), and pixel pitch towards the reduction of DQE at low exposure levels. Methods to improve the DQE through an optimization of both the flat panel design and the scintillator deposition process ate discussed. The results show a substantial improvement in the DQE(f) at all frequencies and demonstrate the potential for DQE(0) to exceed 80%. The combination of high DQE at. ultra low exposures and the inherent fast read-out capability makes this technology platform ideal for both current clinical procedures and advanced applications that may use multiple projections (tomosynthesis) or contrast media to enhance digital mammography.