Novel nanocrystalline Gd_2O_3(Eu) scintillator screens with a micro-pixel structure for high spatial resolution X-ray imaging

摘要

We developed a novel pixel-structured scintillation screen with nanocrystalline Gd_2O_3:Eu particle sizes for high spatial resolution X-ray imaging detectors. Nanocrystalline Gd_2O_3:Eu scintillators were successfully synthesized with a hydrothermal method and a subsequent calcination treatment, which were used as a material for converting incident X-rays into visible light. In this work, silicon-based pixel structures with different 100,50 and 30 urn pixel sizes, a 10 u.m wall width and a 120 urn thickness were prepared with the standard photolithography and the deep reactive ion etching (DRIE) process. Subsequently, a micro-pixel-structured scintillation screen was fabricated by adding the synthesized nanocrystalline Gd_2O_3:Eu scintillating phosphor to pixel-structured silicon arrays. Additionally, X-ray imaging performance such as relative light intensity, X-ray to light response and the spatial resolution in terms of modulation transfer function (MTF) were measured by using an X-ray source and a lens-coupled charge coupled device (CCD) camera system. The light intensity of the pixel-structured nanocrystalline Gd_2O_3:Eu screen was much higher than that of a pixel-structured sample made with a commercial microcrystalline Gd_2O_3:Eu product due to the density of the nanocrystalline Gd_2O_3:Eu scintillating powder-filled silicon structure. As the pixel size of the pixel-structured silicon decreased, the light intensity decreased. However, as the pixel size decreased, the spatial resolution significantly improved with no evident crosstalk from the emitted optical photons between adjacent scintillating pixels. The MTF of pixel-structured nanocrystalline Gd_2O_3:Eu screens with a 100 and a 50 urn pixel size was 20% and 30% at 6 lp/mm, respectively. As a result, this new technology showed that a microchannel structure based on a nanocrystalline Gd_2O_3:Eu scintillator could provide higher light intensity and high spatial resolution imaging compared to conventional microcrystalline scintillating phosphor.