Evaluation of the Red Emitting ${\rm Gd}_{2}{\rm O}_{2}{\rm S}!!:!!{\rm Eu}$ Powder Scintillator for Use in Indirect X-Ray Digital Mammography Detectors

The aim of the present study was to investigate the imaging transfer characteristics and the luminescence efficiency (XLE) of Gd₂O₂S:Eu powder scintillator for use in X-ray mammography detectors. Gd₂O₂S:Eu emits in the red part of the visible spectrum, having very good spectral compatibility with optical sensors employed in digital imaging systems. Three Gd₂O₂S:Eu powder scintillating screens, with coating thicknesses 33.1, 46.4 and 63.1 mg/cm² , were prepared in our laboratory. The imaging performance of these screens was assessed by experimental determination of the modulation transfer function (MTF), the noise transfer function (NTF) and the detective quantum efficiency (DQE) as well as a single index image quality parameter such as the information capacity (IC). A theoretical model, describing radiation and light transfer, was used to fit experimental MTF data. This has allowed the estimation of optical attenuation coefficients of the scintillator. In addition, a previously validated Monte Carlo code, based on the X-ray attenuation properties and on the Mie light scattering theory, was used to estimate the X-ray detection efficiency, the Swank factor and the zero frequency DQE of the Gd₂O₂S:Eu scintillator. Results showed that Gd₂O₂S:Eu exhibits high MTF and DQE values, which are comparable to those of a commercially employed Gd₂O₂S:Tb screen. In addition Gd₂O₂S:Eu shows high compatibility (effective gain) to CCDs and to recently introduced CMOS based detectors. Considering our image quality parameters and luminescence efficiency results, this material can potentially be considered for use in digital X-ray mammography detectors.