Kazuki Shigeta

High spatial resolution performance of pixelated scintillators

In indirect conversion flat panel detectors (FPDs) for digital X-ray imaging, scintillating materials such as Terbiumdoped Gadolinium Oxysulfide (Gadox) convert X-ray into visible light, and an amorphous silicon (a-Si) photodiode array converts the light into electrons. It is, however, desired that the detector spatial resolution is improved because the light spreading inside scintillator causes crosstalk to next a-Si photodiode pixels and the resolution is degraded compared with direct conversion FPDs which directly convert X-ray into electrons by scintillating material such as amorphous selenium. In this study, the scintillator was pixelated with same pixel pitch as a-Si photodiode array by barrier rib structure to limit the light spreading, and the detector spatial resolution was improved. The FPD with pixelated scintillator was manufactured as follows. The barrier rib structure with 127μm pitch was fabricated on a substrate by a photosensitive organic-inorganic paste method, and a reflective layer was coated on the surface of the barrier rib, then the structure was filled up with Gadox particles. The pixelated scintillator was aligned with 127μm pixel pitch of a-Si photodiode array and set as a FPD. The FPD with pixelated scintillator showed high modulation transfer function (MTF) and 0.94 at 1cycle/mm and 0.88 at 2cycles/mm were achieved. The MTF values were almost equal to the maximum value that can be theoretically achieved in the FPD with 127μm pixel pitch of a-Si photodiode array. Thus the FPD with pixelated scintillators has great potential to apply for high spatial resolution applications such as mammography and nondestructive testing.