  In X-ray phase contrast imaging, phase retrieval from intensity measurements
is the key for further quantitative analysis and tomographic reconstructions.
In this letter, we present a single-shot approach for quantitative phase
retrieval in high-energy X-ray grating interferometry. The proposed approach
makes use of the phase-attenuation duality of soft tissues when being imaged
with high-energy X-rays. The phase retrieval formula is derived and presented,
and tested by numerical experiments including photon shot noise. The good
agreement between retrieval results and theoretical values confirms the
feasibility of the presented approach.
