EXPERIMENTAL-DETERMINATION OF DETECTOR GAIN, ZERO-FREQUENCY DETECTIVEQUANTUM EFFICIENCY, AND SPECTRAL COMPATIBILITY OF PHOSPHOR SCREENS - COMPARISON OF CSI-NA AND GD2O2S-TB FOR MEDICAL IMAGING APPLICATIONS

Gd2O2S : Tb and CsI : Na phosphors mostly used in X-ray medical imagin g detectors were compared at various X-ray tube voltages between 50 an d 150 kVp. Laboratory prepared test screens of 80, 110, and 150 mg/cm( 2) coating weight were evaluated on the basis of the number of emitted photons per incident X-ray (NEP) and DQE, both expressing the signal- and-noise transfer properties of image receptors, NEP and DQE were det ermined by a method employing luminescence and emission spectrum measu rements. The spectral compatibility of the two phosphors with films, p hotocathodes and the Si photodiode was also examined. CsI :Na exhibite d high performance in the 60-90 kVp X-ray tube voltage range while Gd2 O2S : Tb was found better at higher X-ray energies. The CsI : Na - fil m combination could provide an excellent X-ray radiographic detector, if effectively protected from humidity. Gd2O2S : Tb is more suitable f or high tube voltage digital imaging but also adequate for conventiona l imaging. (C) 1998 Elsevier Science B.V. All rights reserved.