Dual energy radiography using X-ray films and intensifying screens

The aim of this study was to investigate dual energy (DE) systems using X-ray films and intensifying screens as detecting media. This has been studied using both experimental methods and numerical modelling. Numerical methods were used to calculate energy losses due to K-fluourescent escape originating from the phosphors of the intensifying screens. This enabled the calculation of absorbed energy in screens. The method for screen selection and prediction of performance used the fact that detector response depends upon impinging X-ray energy. By equating the detector's absorbing characteristics to the resultant optical density (OD), an absorbed energy constant was calculated. These constants were used to predict OD for a given X-ray spectrum and hence simulation of detector characteristics. Experimental techniques were used to investigate sensitivity to chemical composition changes. These results compared favourably with computed values. It was demonstrated that although limitations exist, detector simulations are valid and X-ray film intensifying screen combinations make adequate DE detectors.