Factors affecting the performance and efficiency of fluoroscopic screens.

Abstract

All who have had any concern whatsoever with apparatus for the production of X rays are fully conversant with the great changes which have been effected in the plant producing the high-tension current and in the design of the X-ray tube since X rays were first employed. It is not perhaps generally realised that X-ray screens, both fluoroscopic and intensifying, have also been greatly altered and improved since their inception. Modern fluoroscopic screens consist of four separate layers all of which should be in close contact with one another. These layers are: (a) A front protective layer which renders the screen washable and protects the surface generally. (b) A layer containing the fluorescent material. (c) A reflecting layer. (d) A backing layer to give mechanical strength. This consists of a thin layer of transparent colourless material; cellulose acetate is often employed but there is no reason why other plastic materials should not be employed. It is essential that this protective layer should be as thin as practicable, since if the thickness is more than 0·001 to 0·002 in. it has a slightly detrimental effect upon the definition of the screen. It is also essential that the adhesion between the protective layer and the screen itself should be very good. The essential feature of an X-ray screen is, of course, the luminescent substance employed in its construction, this being the transformer of X-ray energy into visible light energy.