(A) study on csi(tl) scintillator thin film characteristics for medical x-ray digital radiography

Abstract

Digital Radiography systems have currently developed and are replacing the conventional X-ray film. In indirect detector of digital radiography systems, the scintillating layer coupled to amorphous silicon photodiode converts the X-ray in to visible light. And also scintillators are the primary radiation sensor in many applications such as medical diagnostics, medical radiographs, and industrial component inspection. Among many various scintillators, T1-activated CsI scintillator is the most promising material for digital radiography. In this study, thin CsI(Tl) scintillation layers were fabricated by thermal vacuum evaporation of mixture of CsI and T1I2 powder. The thin films with various microstructures were manufactured in accordance with pressure, substrate temperature and substrate material. Due to proper evaporation parameters, thin films with porous, dense and columnar polycrystalline structure were manufactured very well. The manufactured thin films with different microstructures were annealed by rapid thermal annealing method. And the annealed thin films were measured for optical characteristics such like visible light transmittance and light output under X-ray exposure as different microstructures. And then in order to evaluate the spatial resolution in accordance with porous, dense, columnar microstructure, Modulation Transfer Function (MTF) curve was measured and analyzed by Charge Coupled Device (CCD) detector.