AN EXPERIMENTAL-METHOD FOR THE DETERMINATION OF SPATIAL-FREQUENCY-DEPENDENT DETECTIVE QUANTUM EFFICIENCY (DQE) OF SCINTILLATORS USED IN X-RAY-IMAGING DETECTORS

The spatial-frequency-dependent detective quantum efficiency (DQE) of imaging scintillators was studied independently of the optical detecto r (film, photocathode, or photodiode) employed in medical imaging devi ces. A method was developed to experimentally determine the scintillat or DQE in terms of its luminescence efficiency (LE), quantum detection efficiency, modulation transfer function, and light emission spectrum . Gd2O2S : Tb,La2O2S : Tb,Y2O2S : Tb and ZnSCdS :Ag scintillating scre ens were prepared in laboratory and were excited to luminescence by a medical X-ray tube. Maximum DQE values varied between 0.13 and 0.33 de pending on the scintillator material, the screen coating weight, and t he tube voltage; Gd2O2S:To was superior to La2O2S:Tb followed by ZnSCd S : Ag and Y2O2S :Tb This ranking was maintained at frequencies up to 100 cycles/cm. Considering the same material, DQE of thin screens was found superior to DQE of thicker screens at medium-to-high frequencies . The proposed method allows for the comparison of imaging characteris tics of scintillating materials without the inclusion of optical detec tor imaging properties.