Which material is commonly used in modern image intensifiers for the input fluorescent screen layer?

Cesium iodide is the material commonly used in modern image intensifiers for the input fluorescent screen layer due to its superior performance characteristics. This material is highly efficient in converting X-ray photons into visible light, specifically in the blue and green wavelengths, which are best suited for increasing the sensitivity of the imaging system. Furthermore, cesium iodide has excellent spatial resolution capabilities, which contributes to the clarity and quality of the images produced.

In addition to its high efficiency, cesium iodide's structure allows for minimal diffusion of light within the layer, thereby providing a clearer and sharper image. This characteristic is essential in fluoroscopic imaging where precision and detail are critical for diagnosis.

Other options, while they may have been used in the past or have particular applications, do not match cesium iodide's effectiveness in contemporary image intensifier technology.