IMAGE INTENSIFIER

Typical Number in Hospital:

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References: 7

This is an integral part of any diagnostic X-ray set which can produce a fluoroscopic image on a video monitor, or on cine film. X-rays can cause a fluorescent screen to glow in the form of the X-ray image, and early fluoroscopes employed this principle to provide moving pictures which had to be viewed in total darkness.

The image intensifier enhances the brightness of the image many times (e.g. x1000 to x5000) so that it can be televised or filmed for daylight viewing. The image intensifier itself is an electronic device contained in a large evacuated glass envelope. It comprises a fluorescent screen on to which the X-rays fall, and this is in contact with a second layer (photocathode) which emits electrons in response to light from the fluorescent screen. The rest of the image intensifier is an electron accelerator and focusing system which produces a smaller brighter image on a second phosphorescent screen similar to a CRT screen. The image on this second screen can be viewed by the cine or video camera.

Fluoroscopic (or screening) systems using image intensifiers are useful for a large number of examinations for which a moving image is essential. Unfortunately they cannot match the sharpness of detail obtained with conventional X-ray film and cassettes.