A Model for a Linear a-Se Detector in Simulated X-Ray Breast Imaging with Monte Carlo Software

As alternative to high-cost and long clinical trials on patient population for testing x-ray breast imaging techniques, the AGATA project proposes the use of in-silico clinical trials with digital patient models and simulated devices. In the in-silico reproductions, the detector model assumes great importance, and its performance should reflect that of the real detector. In this work, we simulated a linear-response a-Se area detector as a pure X-ray absorber of known thickness. The detector response curve, modulation transfer function (MTF) and noise power spectrum (NPS) were measured on a clinical mammographic unit. The same tests were replicated in-silico via the AGATA Geant4 Monte Carlo software. The relations between the measured energy-dependent detector response curves (pixel value vs air kerma) and the simulated ones (pixel dose vs air kerma) will permit to convert simulated pixel values to practical scale values. The comparison between simulated and measured MTF, will permit to define a linear filter for spatial resolution tuning in simulated projections. The comparison between simulated and measured NPS will support strategies for defining a suitable noise model, specifically for the estimates of neglected white noise due to electrons and electro-hole pairs tracking, as well as due to the (not simulated) thermal noise.