TECHNICAL ASPECTS OF TWIN SCREEN-FILM CHEST RADIOGRAPHY - COST-EFFECTIVE LUNG AND MEDIASTINAL IMAGING

Objective: To determine the sensitometry and 'cross-talk' of a twin sc reen-film cassette and to assess its clinical potential. Materials and Method's: The twin cassette utilises two sets of screens, divided by filter material, to provide an optimised image of the mediastinum and the lungs. The exposure difference for the two images was measured sen sitometrically. The contribution to film density of visible light and K-characteristic radiation, from adjacent screens in the absence of a dividing filter: was investigated. Result: Clinical experience indicat ed that an exposure difference of 3.4 between the front and back scree ns, was optimal. Visible light and K-characteristic radiation from the front screens, contributed up to 20 and 24% respectively, of the back film exposure and screen absorbed energy respectively. This was reduc ed to 0 and 6% with the use of the filter. Conclusions: The twin scree n-film cassette provides extended latitude to enable optimal visualisa tion of the lung and mediastinal regions. Adjacent screen 'cross-talk' has been overcome to allow standard and portable chest applications. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.