Signal propagation in rare earth image receptors for digital mammography applications

Signal conversion and propagation in image receptors were studied employing laboratory prepared Gd₂O₂S:Tb and La₂O₂S:Tb phosphor screens. The optical signal emitted by the screens per unit of X-ray exposure was experimentally and theoretically evaluated in the mammographic energy range. Parameters related to signal propagation (light absorption, scattering, reflection, and optical pulses statistical distribution), intrinsic X-ray to light conversion efficiency, and electron signal generated by the photodetector were studied. Image receptors employing Gd₂O ₂S:Tb screens produce higher optical and electron signal intensities whereas receptors with La₂O₂S:Tb screens give better optical pulse statistics, resulting in noise reduction