Image intensifiers (II) are utilized to convert low energy x-radiation into visible light images. Frequently the detector portion of an x-ray C-arm used in operating theaters, the image intensifier has a low scatter input portion made of low absorption substances such as titanium or aluminum . Image intensifiers are several thousand times more sensitive compared to standard 400-speed screen-film combinations, and in practice can produce images using several thousand times less radiation .
The biggest advantage of image intensifiers in medical imaging is the synergy of high detector efficiency and high conversion efficiency to effectively utilize fluoroscopy while adhering to the radiation protection principle of dose optimization.
After the x-ray beam emerges from the patient, it enters the image intensifier tube through the input window and is partially absorbed by the fluorescent input screen (entrance phosphor) creating a number of light photons.
The electrons are accelerated towards the output fluorescent screen by an electric field produced between the photocathode and anode. Focusing and distortion minimization is accomplished by the focusing electrodes.
The electrons hit the output phosphor and cause large numbers of light photons to be produced, which subsequently may be captured by various imaging devices .