Optimization procedure for a Talbot-Lau x-ray phase-contrast imaging system

In Talbot-Lau x-ray imaging, the fringe visibility provided by the interferometer is a crucial quality parameter to preserve high quality images at an acceptable dose level. The noise of the obtained differential phase signal and the dark-field image is directly influenced by the visibility. To optimize the performance of such an interferometer, we use wave-field simulations to investigate the effect of the phase grating G1. Therefore, we varied the grating parameters duty cycle and grating bar height. Each set of these parameters were evaluated for different propagation distances and for multiple x-ray spectra. In this multidimensional space the interferometer configuration with the highest visibility over a wide range of energies was selected to cover a multiple possible x-ray applications. We manufactured the optimized phase grating G1, the corresponding source grating G0 and analyzer grating G2 and compare the experimental results with the expected results obtained from simulations. The presented measurements show outstanding visibilities up to 50% using a broad x-ray spectrum. These measurements are in very good agreement to the simulation results. The achieved visibility is up to two times higher than for a standard-type setup. This enhancement results in high quality images at a reasonable dose level which we exemplarily demonstrate by imaging a foreign object in a pork trotter.