Estimation of the information content of medical images produced by scintillators interacting with diagnostic X-ray beams

The information content of medical images produced by X-ray beam-scintillat or interaction was assessed by a method involving detective quantum efficie ncy (DQE) and information capacity determination. The method was based on e mitted light fluence and modulation transfer function (MTF) measurements an d it was employed to evaluate the performance of (Gd0.5La0.5)(2)O2S:Tb scin tillator, which was used in the form of laboratory prepared scintillator sc reens with coating weights ranging between 20 and 139 mg/cm(2). Screens wer e excited to luminescence using 80 and 120 kVp X-ray beams. The 83 mg/cm(2) scintillator layer exhibited the highest DQE at zero spatial frequency. Th ick scintillator layers displayed higher DQE values in the low frequency ra nge while at high frequencies the DQE of thin scintillators were higher. Ad ditionally, thin scintillator layers showed slow DQE variation with increas ing frequency. The information capacity of scintillator layers decreased wi th increasing coating weight indicating that the information content of ima ges produced by thin scintillating layers is higher and more evenly distrib uted with respect to spatial frequencies. (C) 1999 Elsevier Science B.V. Al l rights reserved.