Phase contrast in laboratory‐based X‐ray micro/nano‐CT

X‐ray micro/nano‐CT has evolved into an extremely valuable tool for various research fields. The current state‐of‐the‐art laboratory‐based systems can scan samples with a resolution below 1 micrometer. Achieving such high resolution usually means scanning very small and thus low absorbing samples, which is done using an X‐ray tube with a very small focal spot size. Under these conditions, the acquired projections not only contain absorption contrast, but also phase contrast due to refraction of the X‐rays. This phase contrast results in edge enhancement, which can be beneficial to detect very small features in radiography. In tomography however, the reconstruction of such mixed projections using a conventional algorithm yields cross‐sections that are severely distorted by so‐called phase contrast artifacts. These artifacts can be prevented by applying a phase retrieval method like the Modified Bronnikov Algorithm (MBA) [1], or the similar simultaneous phase and amplitude extraction [2], which allows reconstructing the object’s refraction function instead of its attenuation function. Alternatively, one can use the Bronnikov‐Aided Correction (BAC) [3] to reduce the phase contrast signal in the projections, which can then be reconstructed without introducing phase artifacts in the reconstructed attenuation function. At the Centre for X‐ray Tomography of the Ghent University (UGCT), these two complementary methods MBA and BAC are commonly applied in every‐day practice, thereby improving the reconstruction quality of high‐resolution CT scans significantly [3,4] (illustrated in figures 1 and 2). Since neither method requires changes in the scanner hardware or the acquisition, they can be readily applied to projection data from any high‐resolution scanner. In addition to results from the scanners of UGCT, results will also be presented for the successful application of both methods on data acquired using other high‐end Xray micro/nano CT systems