There are two common amorphous silicon scintillator coating materials: cesium iodide and gadolinium oxysulfide. Cesium iodide has a stronger ability to convert X-rays into visible light than gadolinium oxysulfide, but the cost is relatively high; processing cesium iodide into a columnar structure can further improve the ability to capture X-rays and reduce scattered light. Detectors using gadolinium oxysulfide coating have fast imaging speed, stable performance and low cost, but the conversion efficiency is not as good as that of cesium iodide coating. The materials and processes of the scintillator coating affect the ability of X-rays to be converted into visible light and therefore have an impact on DQE.
The imaging principles of the two materials are different. Cesium iodide is a semiconductor material that can generate electron-hole pairs under the action of Radiation dose; Gadolinium oxysulfide is a scintillator material that produces fluorescence under the action of X-rays. The fluorescence is collected by a photodiode to generate an electrical signal, which is later read by a TFT. Gadolinium oxysulfide scintillator has light loss due to photoelectric conversion, and its theoretical quantum detection efficiency is lower than that of semiconductor materials. However, needle-like cesium iodide can now be obtained by improving the growth process, which can effectively improve light scattering.
In terms of semiconductor detection materials, there are cadmium telluride, mercury iodide, lead iodide, amorphous selenium (used in breast detectors), etc. Only amorphous selenium still has a place in breast detection due to its good spatial resolution. Living space is squeezed by scintillator, and mercury and lead compounds do not meet environmental needs. A more promising ternary compound material is cadmium telluride. The problem of crystal growth has been invested in the development of medical CT, and the czt film applied to flat panels still needs to solve the problem of low-temperature deposition, and there is still a long way to go! In general, the imaging effect of cesium iodide is slightly better than that of gadolinium oxysulfide (of course this is also dose-related in recent years). Gadolinium oxysulfide is cheaper, but there is not much difference between the two.
A gadolinium oxysulfide scintillator combination plate, including a sensor array flat layer containing a plurality of photosensitive sensor units, a scintillation gadolinium oxysulfide surface layer laid on the sensor array flat layer, and a scintillator with non-specific optics laid on the scintillator layer layer. A reflective structural layer with isotropic reflection characteristics, the surface of the optical reflective structural layer has several light reflective units, and the number of the light reflective units is greater than or equal to the number of the photosensitive sensor units. The invention can overcome the technical problem of MTF decrease caused by light scattering during substrate propagation, thereby improving the performance of the scintillator.