Spectroscopic dark-field imaging using a grating-based Talbot-Lau interferometer

In recent years X-ray phase-contrast imaging became applicable in the hard X-ray regime through the use of a grating-based Talbot-Lau interferometer and was demonstrated to be a promising technique to gain contrast in different fields of medical imaging. In addition to absorption imaging, phase-contrast and dark-field imaging is capable to yield completely new information and is able to provide structural information about a specimen at a scale much less than imaging system-based resolution. Therefore an effective implementation of this information in medical imaging applications benefits substantially from a detailed look onto interferometer setup based effects on the phase signal. For the calculation of the dark-field signal, the loss in intensity modulation, represented by the contrast ratio V / V0, due to local scattering effects within the specimen structure is exploited. By using an energy-resolving detector, spectral effects of a X-ray tube spectrum on the interferometer image quality can be determined. In this contribution we will show first results on spectroscopic dark-field imaging, with a focus to the potential utilization on porous bone structure. Measurements were carried out using a Talbot-Lau interferometer in connection with a hybrid photon-counting semiconductor Timepix detector, which provides an adjustable lower threshold for photon detection.