Digital radiology using self-scanned readout of amorphous selenium: design considerations for mammography

We are developing a large area, flat panel solid-state detector for general application to digital radiology. The proposed detector employs a continuous photoconductive layer of amorphous selenium (α-Se) to convert incident x rays to electron-hole pairs, which are then separated and drawn to the surface of the α-Se by an applied electric field. The resulting charge image is digitally read out in situ using a large area active matrix array made with cadmium selenide (CdSe) thin film transistors (TFTs). The relationship between the potential imaging properties and the design parameters of this detector concept for digital mammography were analyzed theoretically using measured characteristics of α-Se layers and CdSe active matrices.