Lead Intensifying Screens are thin sheets of lead foil mounted on card for ease of handling. One is placed either side of x-ray film and in close contact with it, inside the cassette or film holder prior to exposure. They are used in most radiographic techniques, excluding some of those employing low kilo-voltages, because they reduce the exposure required and improve the quality of the image. The screens are made from the finest available radiographic lead foil, laminated onto flexible white photographic base card. The lead surface is not covered with a lacquer coating. The specially formulated lead-rich alloy is hard enough not to cause the transfer of deposits onto the film in normal use. Un-coated lead also has the advantages of higher intensification and the absence of problems associated with uneven coating or melting or partial wearing away of the lacquer. The corners of the screens are rounded to a convenient radius to prevent damage to films and cassettes. Each screen is clearly stamped with the lead thickness.
To ensure that the screens are received in perfect condition, the lead surface is protected by a PEEL-OFF protective plastic film. IT IS ESSENTIAL that the protective film is removed before using the screens.
The film is best removed by applying a piece of adhesive tape to the corner of the screen, the tape and film will peel away together cleanly and easily.
Intensifying screens are made in sizes for all the world markets. Standard metric and imperial sizes are cut according to BS3490:1985 and ISO 5655-1982. Special sizes can be made to order. The following lead thicknesses (mm.) are available; 0.050, 0.100, 0.125, 0.150, 0.200, 0.250, 0.500, 0.750, 1.000, 1.500, 2.000 and 3.000. Pairs of any thickness combinations can be supplied. Screens are normally sold in 5, 10 or 25 pair packs, but those thicker than 0.250mm are available only in single pair packs.
Intermediate (centre) screens, with lead foil on each side of the card support, are available with any lead thickness. Most commonly they are supplied as 0.10mm (0.05 lead on each side) or 0.20mm (0.10mm of lead on each side).