X-ray photoconductors and stabilized a-Se for direct conversion digital flat-panel X-ray image-detectors

Recently developed direct conversion flat-panel X-ray image detectors provide not only potentially superior images but also enable a simple and convenient means of achieving digital radiography. The present flat-panel sensors use stabilized a-Se as an X-ray photoconductor to convert absorbed X-ray photons to collectable charge carriers. The present paper outlines the basics of the direct conversion flat-panel X-ray detector, formulates and reviews the required X-ray photoconductor properties and examines to what extent stabilized amorphous selenium (a-Se) fulfills these requirements and how it compares with other potential X-ray photoconductors that have been proposed. Charge transport and the electron-hole pair creation energy in stabilized a-Se are reviewed within the context of our present knowledge. Current materials problems and future potential developments are also critically discussed.