EUROPIUM-ACTIVATED PHOSPHORS FOR USE IN X-RAY-DETECTORS OF MEDICAL IMAGING-SYSTEMS

Three europium-activated phosphors Y2O2S:Eu, Y2O3:Eu, and YVO4:Eu emit ting red fight were studied to investigate their suitability for radio graphic cassettes or digital imaging systems. Screens were prepared fr om phosphor powders with various coating thicknesses by sedimentation. To assess phosphor light producing efficiency in relation to patient dose, each screen was X-rayed using 40-120 kVp and the number of light photons emitted per X-ray incident was experimentally and theoretical ly evaluated. Additionally, the capability of the emitted light to sen sitize films or to generate electrons in silicon photodiodes used in d igital imaging systems was examined. Y2O2S:Eu screens were most effici ent in light emission, and when combined with either red sensitive fil ms or Si photodiodes, they were found superior to Y2O3:Eu or YVO4:Eu s creens in film grain or electron signal generation. In many cases they were also found superior to terbium-activated phosphors. Provided tha t several problems related to industrial production (special dyes, ref lective backing, crossover effects) are dealt with, those europium-act ivated screens could be employed in low-tube-voltage radiographic appl ications.