X-ray image intensifier

The XRII requires lower absorbed doses due to more efficient conversion of X-ray quanta to visible light.

The thickness of input phosphor range from 300 to 450 micrometres reach a compromise between absorption efficiency of X-rays and spatial resolution.

Thicker input phosphor has higher absorption efficiency but poor spatial resolution and vice versa.

Sodium activated Caesium Iodide is typically used due to its higher conversion efficiency thanks to high atomic number and mass attenuation coefficient, when compared to zinc-cadmium sulfide.

[2] A potential difference (25-35 kilovolts) created between the anode and photocathode then accelerates these photoelectrons while electron lenses focus the beam down to the size of the output window.

The output window is typically made of silver-activated zinc-cadmium sulfide and converts incident electrons back to visible light photons.

This gain makes image intensifiers highly sensitive to X-rays such that relatively low doses can be used for fluoroscopic procedures.

High-speed digitalisation with analogue video signal came about in the mid-1970s, with pulsed fluoroscopy developed in the mid-1980s harnessing low dose rapid switching X-ray tubes.

[15][16] Smaller "mini" mobile c-arms are also available, primarily used to image extremities, for example for minor hand surgery.