A method to evaluate the performance of X-ray imaging scintillators by means of the brightness-sharpness index (BSI)

Purpose: To propose an image quality index, the brightness-sharpness index (BSI), for assessing the quality of the image produced by phosphors of medi cal imaging detectors. Material and Methods. BSI was evaluated by experimental X-ray luminescence and modulation transfer function measurements. BSI was determined for a num ber of lest phosphor screens prepared from Gd2O2S:Tb, La2O2S:Tb, and Y2O2S: Tb phosphor materials. The screens covered a wide range of coating thicknes ses from 50 to 150 mg/cm(2) and measurements were performed for Xray tube v oltages between 50 and 120 kVp. Results. Gd2O2S:Tb phosphor exhibited higher brightness and sharpness, as c ompared to the other phosphor materials, for all screens and X-ray tube vol tages used. Best Gd2O2S:Tb performance was observed for thin screens and hi gh tube voltages. La2O2S:Tb exhibited higher BSI values than Y2O2S:Tb for m edium and high tube voltages. Conclusion: Results showed that phosphor materials of high X-ray detection and X-ray-to-light conversion propel ties exhibit high BSI values indicatin g that BSI may provide a means of phosphor performance evaluation for imagi ng applications.