Assessing the information content of phosphor produced medical images: application to Zn2SiO4 : Mn phosphor

In this study a method to assess the information content of medical images produced by phosphors is described. The optical signal emitted by the phosp hor after X-ray excitation, the detective quantum efficiency (DQE), express ing the signal-re-noise ratio (SNR) transfer efficiency, and the informatio n;capacity were experimentally determined. The method was based on light fl ux and modulation transfer function (MTF) measurements and was used to asse ss the imaging performance of the Zn2SiO4:Mn phosphor. The latter was emplo yed in the form of laboratory prepared phosphor layers (test screens). Resu lts showed that high values for optical signal emission and DQE were obtain ed for medium thickness phosphor layers (56 and 89 mg/cm(2)) at 20 kVp X-ra y tube voltage. The information capacity was found to decrease continuously with phosphor coating weight. (C) 2000 Elsevier Science Ltd, All rights re served.