A method for determining the information capacity of x-ray imaging scintillator detectors by means of luminescence and modulation transfer function measurements

A method to determine the information capacity of x-ray phosphor screens us ed in the detectors of medical imaging systems is described. Information ca pacity was determined via x-ray luminescence efficiency (XLE), modulation t ransfer function (MTF) and emission spectrum measurements. The method was a pplied to laboratory prepared screens from commonly employed phosphor mater ials. The screen coating weight varied from 50 mg cm(-2) to 140 mg cm(-2). Results indicated that information capacity decreased with screen coating t hickness but also depended on intrinsic phosphor properties (density, effec tive atomic number, intrinsic conversion efficiency, light wavelength). The Gd2O2S:Tb phosphor, exhibiting high density and effective atomic number, w as found to be superior to La2O2S:Tb and Y2O2S:Tb.