Contrast based method for the automated analysis of transfer functions and spatial resolution limits of micro- and nano-focus computed tomography systems: Evaluation with simulated data

Micro- and nano-focus X-ray sources are extensively used in X-ray computed tomography systems to achieve high spatial resolution. This is essential, when scanning small objects, where resolution limitations are mainly connected to the size of the focal spot. Therefore, much effort has been put into reducing the size of the focal spot, where the measurement of the focal spot size is challenging. In this paper, the implementation of a new evaluation method for the quantitative determination of the system's transfer function and the source’ spot size and shape are presented. The spatial resolution is calculated at different evaluation points to assess which particular threshold should be used to obtain the resolution limit and the focal spot size and shape. The implementation is explained and evaluated with the aid of simulated and real radiographs of the test chart, featuring line and star patterns designed to bridge the gap between existing resolution standards.