Phase contrast X-ray imaging can be much more sensitive to soft tissue lesions than conventional absorption contrast X-ray imaging, being a potential game changer for medical imaging. A phase contrast method well suited for clinical implementation is the grating interferometry. We show that by using μm period multi-meter long interferometers one can strongly increase the phase sensitivity and lower the dose towards soft tissue imaging applications such mammography. Conventional X-ray tubes do not provide, however, sufficient X-ray flux for clinical imaging with such long interferometers. Instead, 100-TW class lasers could produce highly directional and intense X-ray sources ideal for high sensitivity medical interferometry. We present the X-ray source characteristics required for clinical interferometry, advantages and disadvantages of betatron versus inverse Compton scattering sources for clinical application, and some practical considerations towards laser based interferometric medical imaging.
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 μm thick Au gratings at 10° incidence we increased several fold the interferometer contrast for a spectrum with ~58 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.
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