K-edge and Mirror Filtered X-ray Grating Interferometers

Talbot-Lau interferometers having good angular resolution and fringe contrast are needed for refraction imaging of biomedical objects with conventional X-ray tubes. To maximize angular resolution the interferometers must work in high Talbot orders, which in turn narrows the spectral region of good fringe contrast. To select this narrow region from the broad tube spectrum we study spectral filtering with K-edge absorbers or with grazing incidence X-ray mirrors. For instance, using a total reflection Au mirror at 2.7 mrad incidence in conjunction with a Mo tube at 50 kVp we obtain up to 30% contrast in the fifth Talbot order. The improved angular sensitivity and contrast achieved with quasi-monochromatic filtering enable single-exposure refraction imaging of soft tissues. The mirror filtering offers also a path for increasing the interferometer contrast at high X-ray energy.