Development of an image receptor for use in digital mammography

We have recently developed a digital x-ray image receptor for use in mammographic procedures. The detector is based upon a photoconductor, amorphous selenium (a-Se), coupled to a polymer dispersed liquid crystal (PDLC) layer. A potential is applied across the structure to create a bias electric field in the photoconductor. When x-rays are absorbed in the photoconductor, electron-hole pairs are released. The created charges are swept to the a-Se /PDLC interface via the applied electric field, which causes potential variations across the PDLC. These variations lead to liquid crystal (LC) molecule re-orientation, which affects the propagation of readout light from an external source through the display. The readout light can be bright in this arrangement so that no secondary quantum sinks are present. Since this system is independent of light creation in contrast with a phosphor screen system, the image brightness can be adjusted independently of the number of xrays used to make the image. The image can be digitized with a CCD camera and a frame grabber. Results will be presented on the PDLC characteristics, the system model and initial images from the detector.