X-ray Image Intensifier

An x-ray image intensifier (XRII), is an imaging component which converts x-rays into a visible image.

The term image intensifier refers to a specific component of an x-ray imaging system, which allows low intensity x-rays to be converted to a visible light output. The device contains a low absorbency/scatter input window, typically aluminum, input fluorescent screen, photocathode, electron optics, output fluorescent screen and output window. These parts are all mounted in a high vacuum environment within glass or more recently, metal/ceramic. It allows the viewer to more easily see the structure of the object being imaged than past fluorescent screens. The X-ray II requires lower dose rates due to more efficient conversion of x-ray quanta to visible light. This device was originally introduced in 1948.

Viewing of the output was via mirrors and optical systems until the adaption of television systems in the 1960s. Additionally, the output was able to be captured on systems with a 100mm cut film camera using pulsed outputs from an x-ray tube similar to a normal radiographic exposure; the difference being the II rather than a film screen cassette provided the image for the film to record.

The input screens range from 15–57 cm, with the 23 cm, 33 cm and 40 cm being among the most common. Within each image intensifier, the actual field size can be changed using the voltages applied to the internal electron optics to achieve magnification and reduced viewing size. For example, the 23 cm commonly used in cardiac applications can be set to a format of 23, 17, and 13 cm. Because the output screen remains fixed in size, the output appears to "magnify" the input image.