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Computed tomography (CT) is a foundation of modern clinical diagnostics but it presently only retrieves information from X-rays attenuation. However, it is known that micro structural texture or porosity – which is well below the spatial resolution of CT – can be revealed by grating-based dark-field imaging. Diagnostic value of this sub-resolution tissue information has been demonstrated in pre-clinical studies on small-animal disease models and recently also in a first clinical radiography system.1 These studies show that dark-field imaging is particularly useful for early detection and staging of lung diseases. While dark-field CT is regularly realized in laboratory environment, the transfer to human scale and bringing it to clinical application poses several technical challenges. Switching from a step-and-shoot acquisition to a mode where the gantry and acquisition operate continuously as well as reducing scan times to below seconds and ensuring stability against vibrations are key concerns when it comes to the translation of the established laboratory dark-field technology to full-body medical CT. In,2 we recently demonstrated the first dark-field CT implementation, which collectively solves these roadblocks and therefore is a milestone in the development of clinical CT imaging. The prototype we present allows to reconstruct the attenuation and dark-field channels of a human thorax phantom from a one second long acquisition and covers a 45 cm diameter field of view. In this work, we present how the first dark-field CT prototype works and focus particularly on the technical design, optimized design of the gratings for CT application and the first characterization of the interferometer in the rotating gantry. We discuss which steps where particularly important for the realization and where we see potential for further improvements. These results provide key insights for future dark-field CT implementations.
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