High Energy X-ray Phase-Contrast Imaging Using Glancing Angle Grating Interferometers

The Talbot-Lau grating interferometer enables refraction based imaging with conventional X-ray tubes, offering the promise of a new medical imaging modality. The fringe contrast of the normal incidence interferometer is however insufficient at the >40 keV photon energies needed to penetrate thick body parts, because the thin absorption gratings used in the interferometer become transparent. To solve this problem we developed a new interferometer design using gratings at glancing incidence. For instance, using 120 mu m thick Au gratings at 100 degrees incidence we increased several fold the interferometer contrast for a spectrum with 5 similar to 8 keV mean energy. Tests of DPC-CT at 60-80kVp using glancing angle interferometers and medically relevant samples indicate high potential for clinical applications. A practical design for a slot-scan DPC-CT system for the knee is proposed, using glancing angle gratings tiled on a single substrate.