Novel radiography approaches based on the wave nature of x-rays when propagating through matter have a great potential for improved future x-ray diagnostics in the clinics. Here, we present a significant milestone in this imaging method: in-vivo multi-contrast x-ray imaging of a mouse using a compact scanner. Of particular interest is the enhanced contrast in regions related to the respiratory system, indicating a possible application in diagnosis of lung diseases (e.g. emphysema).

To explore the future clinical potential of improved soft-tissue visibility with grating-based X-ray phase contrast (PC), we have developed a first preclinical computed tomography (CT) scanner featuring a rotating gantry. The main challenge in the transition from previous bench-top systems to a preclinical scanner are phase artifacts that are caused by minimal changes in the grating alignment during gantry rotation. In this paper, we present the first experimental results from the system together with an adaptive phase recovery method that corrects for these phase artifacts. Using this method, we show that the scanner can recover quantitatively accurate Hounsfield units in attenuation and phase. Moreover, we present a first tomography scan of biological tissue with complementary information in attenuation and phase contrast. The present study hence demonstrates the feasibility of gratingbased phase contrast with a rotating gantry for the first time and paves the way for future in vivo studies on small animal disease models (in the mid-term future) and human diagnostics applications (in the long-term future).differential X-ray phase contrast | grating interferometer | X-ray imaging O ne of the main shortcomings of existing biomedical X-ray imaging systems is their weak contrast in soft tissue. This limitation can be addressed by phase-sensitive imaging methods that rely on the phase shift that X-rays undergo when passing through matter (1). The resultant refraction angle can be utilized as contrast mechanism in a grating-based interferometer in radiographic (2, 3) and tomographic acquisition mode (4, 5). In a computed tomography scan, quantitative information about the sample's composition can be extracted-i.e., the linear attenuation coefficient μ and decrement of the refractive index δ can be reconstructed (6-8). Because the grating-based phase-contrast imaging method is compatible with X-ray tube sources, when operated as Talbot-Lau interferometer (9), a translation to a clinical application scenario is currently discussed with great enthusiasm in the research community. Recent studies with laboratory X-ray sources have shown excellent imaging results with respect to softtissue contrast (10)(11)(12)(13)(14). In order to explore the envisioned clinical potential, we have developed a first preclinical phase-contrast CT scanner. This development represents an important milestone in the translation of phase-contrast imaging to clinical settings, as all grating-based phase-contrast setups, which are reported in the literature so far, use a rotating sample for tomographic scans. Because this mode of operation is obviously not preferable for intended in vivo animal studies, we have explored with this work the step from rotating sample to rotating gantry. The main challenge in this translation process was mechanical stability regarding the required precise alignment of the X-ray optical components (gratings). Even mechanical movements of either grating of only fractions of a micrometer during gantry rotation already c...

We investigated the cluster-surface interaction of Au clusters deposited on MgO cubes and on amorphous carbon, and its influence on the morphology of the Au cluster. Au clusters, produced in a laser vaporization source, are deposited with low energy on carbon-coated microscope grids on which MgO cubes are first deposited as substrates. Clusters on the amorphous carbon as well as clusters on the MgO cubes are studied by high-resolution electron microscopy ͑HREM͒. The clusters have different morphologies for the two different surfaces, and a dilation of the Au lattice is also measured for the clusters deposited on the crystalline surface of MgO to perfectly accommodate the MgO lattice. Classical molecular dynamics ͑MD͒ is applied to model this behavior. Good agreement is found between experimental cross-section HREM images and theoretical images simulated with the multislice technique using the model calculated by MD.

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