Monte Carlo study on optimization of reflectors in pixelated CsI film for mammographic application

Isotropic light spread in the scintillator film decreases the spatial resolution of scintillator-based digital X-ray imaging systems such as digital radiography and mammography. Pixelation of the scintillator film could be a good solution to overcome this limitation. This has been demonstrated with pixilated CsI:Tl layers which was made by thermal evaporation process on a pre-patterned substrate or which was post-patterned by laser after preparation. Additionally, in order to minimize cross-talk between pixels and to maximize light collection efficiency, a reflection material can be coated on the top and side surfaces of each pixilated scintillator block. In this paper, several materials such as Al, and quarter-wave multilayer reflector with SiO₂ and TiO₂ were considered as the reflector materials of pixilated CsI:Tl scintillator blocks. Through a serious of simulations given below on these simple 2-dimensional scintillator blocks coated by a reflector, reflectivity, cross-talk, and modulation transfer function were calculated to find the optimum reflector. (author)