Optimization of the X-ray tube voltage with respect to the dynamical resolution in radiography and tomography

Abstract: The tube acceleration voltage influences the contrast in radiographic images. Let a specimen be considered made of a homogenous material, with variable thickness. The local differences in thickness cause contrast in the radiographic image of the specimen. To distinguish the thickness differences, or details, in the best possible way, it is necessary to maximize the contrast. The most straightforward approach to this task is to maximize the difference of the intensities of beams penetrating the object through its maximum and minimum thickness by setting the appropriate X-ray source / detector parameters. However, in case of tomography, the minimum thickness is zero in the majority of projections and a modified approach must be used. Additionally, the task gets more complicated when a real detector with quantizied (discrete) response is considered. This contribution introduces a mathematical model that allows setting the effective energy of the polychromatic X-ray beam from the point of view of contrast. It extends the model for small changes of thickness presented at iCT 2017 and subsequently in NDT.net. The predicted results are compared with experimental data.