Quantitative phase and absorption tomography with an X-ray grating interferometer and synchrotron radiation

We report on a study on the accuracy and precision of X-ray phase and absorption tomograms obtained with a grating interferometer using monochromatic synchrotron radiation. The quantitative assessment of the performances of the X-ray interferometer is a fundamental aspect in the interpretation of the results obtained with this device. The work presented in this paper consists in the comparison of experimental with calculated three-dimensional distributions of the X-ray refractive index in a phantom sample made of known materials. The quality of phase and absorption tomograms has been determined with respect to their sensitivity and contrast-to-noise ratios. Moreover, the effect of image artifacts typical in phase contrast imaging based on the phase-stepping technique, especially stripe features generated by the phase wrapping phenomenon, has been investigated by comparison with numerical simulations. The results show that the artifacts cannot only be qualitatively explained by the calculations, but they can even be quantitatively reproduced. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim