A theoretical model predicting the intensity of light emitted by x-ray imaging phosphor screens per unit of area and time over incident x-ray flux (absolute efficiency) was developed. The model takes into account : A) the structure of the screens which consists of luminescent grains embedded in a binding matrix. B) the direct deposition of energy by x-ray absorption effects.. C) the re-absorption of K fluorescence characteristic x-rays produced when the x-ray energy exceeds the energy of the K absorption edge of the phosphor material. To test the model a set of (Gd,La)2O2S:Tb phosphor screens was prepared by sedimentation in the laboratory. Experimental absolute efficiency data were obtained at x-ray tube voltage range from 40 to 160 kVp. The coincidence between experimental and theoretical results were satisfactory. (authors) 7 refs., 4 figs.
Tsoukos, S; Kateris, A; Kalivas, N; Spyrou, G; Panayiotakis, G;  Kandarakis, I; Gavouras, D 
- Department of Medical Physics, School of Medicine, University of Patras, 265 00 pAtras (Greece)
- Department of Medical Instrumentation Technology, Technological Educational Institution of Athens (Greece)