D. Cavouras et al., Assessment of the gain transfer function of phosphors for application in medical imaging radiation detectors, EUR J RAD, 35(1), 2000, pp. 70-77
Objective: to study various phosphors used in detectors of medical imaging
systems by the gain transfer function (GTF), defined in terms of X-ray lumi
nescence efficiency, light spectrum and modulation transfer function.
Materials and methods: four phosphor materials, La2O2S:Tb, Y2O2S:Tb, Y2O2S:
Eu and Y2O3:Eu were used in the form of fluorescent layers prepared in the
laboratory. The GTF was determined at 30 kVp and 80 kVp X-ray tube voltages
for various phosphor coating weights.
Results: La2O2S:Tb, which was the highest density and effective atomic numb
er phosphor used, was found to exhibit the best GTF performance at 80 kVp.
At 30 kVp, the yttrium based phosphors were found of increased performance.
This is mainly due to the proximity of the X-ray energy to the K-absorptio
n edge of yttrium at 17 keV. Europium activated phosphors were found to per
form very well when combined with the red sensitive film and the silicon ph
otodiode.
Conclusion: The GTF may be a useful method for comparing and selecting phos
phor materials for use in various medical imaging applications. (C) 2000 El
sevier Science Ireland Ltd. All rights reserved.