Evaluating and Modelling the Performance of a Portable X-Ray Imaging System

The current study was carried out at the premises of the University of Leicester and 3DX-Ray Ltd. The analysis was done on a portable X-ray system that is destined for security applications and consists of an X-ray source, a digital panel and a laptop. Given several constraints related to the modern needs of security applications and to the commercial aspect of the product, not only the overall performance of the system has been evaluated but also a series of factors that can reduce the image quality, in terms of resolution and contrast, has been analysed. To achieve this, two models that estimate the absorption and the scattering signal have been developed. The absorption model alone failed to predict the transmitted intensity that reaches the screen when low contrast, low density materials are exposed. A qualitative analysis on the scattering signal showed that scattering plays an important role, hence, another model has been developed to simulate the scattering process. During model development various physical parameters, that were required for the correct projection, have been quantified. Although the detector panel has not been studied thoroughly, the sum of the two models resulted in a very good approximation of the exposure as it was verified by the comparison of the calculations against the experimental data. Throughout calculations, a semi-empirical discrete energy spectrum was used to simulate the spectrum of the generated X-ray beam, as there was no spectral analysis done on the source. In addition to the model development, a method that estimates the dimensions of one of the fundamental limits of system’s resolution, the focal spot, has been devised. Future work includes the unification of the two models and the thorough investigation of the detector.