A novel numerical method to eliminate thickness effect in dual energy X-ray imaging used in baggage inspection

Abstract

One of the methods for material inspection is the dual-energy X-ray technique. Although this method can be more useful in material distinguishing, but signal׳s intensities are still dependent on the thicknesses of materials in front of the detector, so the material identification results may be affected. In this paper, the new technique using Composite Simpson numerical method has been introduced for eliminating this conflicting effect which stems from material׳s thickness in the image. This method has been evaluated for some materials such as aluminum and plastic. Calculations have been performed using MCNP4C code to obtain the received X-ray intensity to the detectors. MATLAB software has been also used for the calculations of removing the effect of thickness and optimizing the system performance. Results have shown good performance in identifying materials independent of their thicknesses. The standard deviation of the R parameter, a common parameter for identification, has been improved from 0.613 to 0.0557 for aluminum and from 0.3043 to 0.0288 for plastic, respectively. This method provides an approximation for the X-ray attenuation at two X-ray energies instead of two energy spectra which greatly improves the material identification.