Modeling MTF and DQE for Arbitrary Scintillator Thickness

Modeling the detective quantum efficiency (DQE) performance of a digital X-ray detector is critically dependent on an accurate representation of the modulation transfer function (MTF). Accurate MTF models that are valid for arbitrary thicknesses and spectra are difficult to formulate for CsI partially due to the needle structure present. We present a model for MTF based on cascaded system theory by dividing the scintillator into numerous thinner layers. The spreading of the light in each of these layers is compounded over the entire scintillator thickness. Using this method we are able to reproduce the MTF for scintillators with thicknesses ranging from 100 to 800mum for varying spectrum energy using two global fit parameters. Using these results, the DQE is then calculated using a cascaded system approach. We present the modeling results of MTF and DQE together with experimental data to demonstrate the ability to accurate predict system performance.