Theoretical characterization of imaging performance of screen-printed mercuric iodide photoconductors for mammography

Abstract

We theoretically characterize the imaging performance of a hypothetical mercuric iodide (HgI 2 ) photoconductor prepared by a screen printing method in terms of the spatial-frequencydependent detective quantum efficiency (DQE) using the cascaded-systems analysis. In the DQE model, we use the "photon-interaction process" in order to represent both the selection of interacting photons and subsequent conversion gain as a single process because both processes are not statistically independent but their probabilities are determined by the photon energy. We further include the thermal generation process of leakage current charges and the incomplete chargecollection process in the DQE model. Theoretical imaging performances of the hypothetical HgI 2 photoconductor sample are compared with those of a 0.2-mm thick amorphous selenium (a-Se) under mammographic imaging conditions. It is shown that the hypothetical HgI 2 with a smaller value of the average ionization energy than a-Se gives a better DQE performance at lower exposure levels, which suggests that a HgI 2 -based photoconductor may have the potential to reduce the 1 Corresponding author.

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