Speaker
Dr
Bo Kyung Cha
(KERI)
Description
In the last decade, indirect digital X-ray imaging detectors have widely been used for medical imaging and industrial applications. Indirect-detection method is usually cosisted of a scintillation screen (or an X-ray converter) and 2D electronic image devices. A variety of scintillation materials such as terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) and europium-doped gadolinium oxide(Gd2O3:Eu) and thallium-doped Cesium iodide(CsI:Tl) with columnar structure are commonly used because of their high luminescence efficiency and emission wavelength(500-600nm region) well matching to silicon sensors such as a-Si:H based TFT panel detector, CCD and CMOS based imaging devices. However, many researches on scintillation materials are still ongoing for high spatial X-ray imaging application.
In this work, nanocrystalline Gd2O3(Eu) material as a scintillator for high spatial X-ray imaging were fabricated through co-precipitation synthesis method. This synthesis process was carried out using Eu(NO3)3·6H2O and Gd(NO3)3·6H2O as well as a 0.25mol DEA precipitant. The precipitate solution was vigorously stirred at room temperature (RT). And then complete precipitation was done by adding small amount of DI water and maintaining for a few hours. After centrifugation by DI water and ethanol, the bright white powder was dried at 60°C for 12 hours. The as-synthesized powder was calcinated at various temperatures with 600-1400°C in the electric furnace. And also, the synthesized Gd2O3 powders with Eu3+ concentration of 3, 5, 7, 10mol% were calcinated at different heat-treatment time with 3, 5, 7, 10 hour. For evaluation of X-ray imaging characterization, uniform nanocrystalline Gd2O3(Eu) scintillation films with both 145 and 200μm thickness were fabricated by screen printing method.
X-ray diffraction(XRD) and scanning electron microscopy(SEM) were measured in order to investigate the characterization such as the crystal structures and microstructures of nanocrystalline Gd2O3(Eu) scintillator according to various calcination time and Eu3+ concentration. The phase transformation from cubic to monoclinic structure was discovered at 1300°C calcination temperature. The highest light output by X-ray excitation was showed at 1100°C calcinations temperature and 5 hour. As calcination time and doped-Eu3+ concentration of synthesized Gd2O3(Eu) scintillator increase, particle size and crystal structure were little not changed. X-ray imaging performance in terms of the light response to X-ray exposure dose, signal-to-noise-ratio (SNR) and modulation transfer function(MTF) were measured by combining the fabricated nanocrystalline Gd2O3(Eu) screens with a lens coupled-CCD camera under radiographic conditions.
Author
Dr
Bo Kyung Cha
(KERI)
Co-authors
Mr
Bae Jung Hyung
(KAIST)
Prof.
Cho Gyuseong
(KAIST)
Dr
Huh Young
(KERI)
Dr
Jeon Sungchae
(KERI)
Mr
Kim Jong Yul
(KAIST)
Dr
Seo Chang-Woo
(KERI)
