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Investigation of an active matrix flat-panel imager (AMFPI) employing a thin layer of polycrystalline HgI2 photoconductor for mammographic imaging

Active matrix flat-panel imagers (AMFPIs) have become ubiquitous across a wide variety of medical x-ray imaging applications. While AMFPIs based on both direct and indirect detection of the incident radiation offer many advantages, their performance is limited by relatively modest system gain compared to electronic additive noise. The effects of this limitation upon imaging performance become particularly apparent at lower exposures and/or at higher spatial frequencies. One potential strategy for overcoming this limitation involves the use of a high gain photoconductor such as mercuric iodide (HgI2) which has the potential to improve system gain by up to an order of magnitude compared to that provided by a-Se, the only photoconductor material presently used in direct detection AMFPIs. In this paper, preliminary results from an investigation of the performance of a prototype direct detection AMFPI employing a relatively thin layer of polycrystalline HgI2 created through a screen-printing method and operated under mammographic irradiation conditions are presented. The results encourage further examination of this strategy to improve the performance of AMFPIs designed for mammography.