Fabrication and comparison Gd2O2S(Tb) and CsI(Tl) films for X-ray imaging detector application

During the last decade, digital X-ray imaging systems have been replacing analog X-ray imaging systems of conventional X-ray film-screen combination for radiography applications. Indirect detection methods consisted of an X-ray converter (or a scintillator film) and photodiode arrays are more widely used in medical diagnoses and industrial fields. Two major scintillation materials such as terbium doped gadolinium oxysulfide (Gd2O2S:Tb, GOS) and thallium doped cesium iodide (CsI:Tl) are commonly used. In this work, GOS scintillator films were manufactured by mixing and thermal hardening of Gd2O2S:Tb powder, dispersion agent, hardening agent, and other organic additives. And CsI:Tl scintillator films with columnar structure were also fabricated by the thermal evaporation method. The scintillation properties, such as emission spectrum and light yield etc., of the GOS and CsI:Tl films were measured by X-ray luminescence and photo-luminescence (PL) methods. The maximum luminescent intensity of both scintillators was observed at 540–560nm wavelength. In order to investigate the imaging performances of both GOS and CsI:Tl films as converters of X-ray imaging detectors, both scintillator films were coupled with an CCD sensor. The light response to X-ray dose, signal-to-noise ratio (SNR), spatial resolution were measured and analyzed under the same X-ray conditions. As X-ray dose increases, the SNR curves showed linear relationship. And the spatial resolution of two scintillator films was resolved at 7∼8lp/mm.