This study explores recent developments in quantitative phase-contrast microtomography using Talbot Array Illuminators (TAI) combined with Unified Modulated Pattern Analysis (UMPA). We first compare the performance of the TAI-based method for phase-retrieval with propagation-based imaging (PBI) for analyzing a Mg-10Gd bone implant sample that violates the single-material assumption. Our results demonstrate that the TAI method yields a significantly higher contrast-to-noise ratio (CNR) compared to PBI (101.68 vs. 54.37, an 87% improvement) while maintaining comparable edge sharpness. The TAI method also visualizes a substructure of the degradation layer, which appears comparatively blurred in the PBI images. Additionally, we introduce a hanging-rotation-axis approach for imaging paraffin-embedded samples in an ethanol bath, aiming to reduce edge enhancement artifacts caused by large electron density differences. Preliminary results indicate that the TAI-based images of a paraffin-embedded lymph node show improved uniformity in background intensity, though some additional low-frequency noise is observed. All experiments were conducted at the High Energy Materials Beamline (HEMS), PETRA III, DESY, operated by Hereon. Our findings highlight the potential of TAI-based phase-contrast imaging for complex, multi-material samples and suggest avenues for further optimization of the technique.
Simon Pinzek, Thomas Beckenbach, Manuel Viermetz, Pascal Meyer, Alex Gustschin, Jana Andrejewski, Nikolai Gustschin, Julia Herzen, Joachim Schulz, Franz Pfeiffer
Background: X-ray grating interferometry is an emerging imaging technique that strongly relies on fine grating structures. A common method to fabricate compatible gratings is deep x-ray lithography (DXRL).
Aim: To develop a method to fabricate grating structures by DXRL, which does not require a synchrotron source.
Approach: The synchrotron source is replaced by a conventional x-ray tube. The fabrication process is adapted for the divergent beam by cylindrically bending mask and substrate.
Results: A 10-μm period absorption grating with 80-μm-thick gold lamellae is successfully fabricated from an intermediate 110-μm high structured resist. This grating is characterized and implemented in a preclinical Talbot-Lau interferometer designed for medical thorax imaging.
Conclusion: This approach can overcome the strong dependence on synchrotron facilities for the fabrication of gratings for x-ray grating interferometry. As x-ray tubes are more widely available, this is a cost-efficient and scalable alternative suitable for industrial production.
Phase-contrast imaging is one of the standard X-ray imaging methods at synchrotron beamlines and has already proven to be beneficial for soft-tissue visualization. However, most implementations use single-distance inline phase-contrast techniques, and are thus not able to provide quantitative information. To access these, grating-based imaging (GBI) setups or, rather recently, speckle-based imaging (SBI) methods can be used. We built a new grating-based setup at the beamline P05 operated by HZG at the storage ring PETRA III / DESY. This new setup overcomes the previously reported limitations in spatial resolution compared to inline phase-contrast imaging. Furthermore, it allows for accurate quantitative phase contrast micro computed tomography of biological soft tissue. We replaced the typically used sandpaper by a 2D phase-grating as a wavefront marker, which increased the visibility and allowed for using fewer phase steps. Combined with an existing SBI phase-retrieval algorithm, the so-called Unified Modulated Pattern Analysis (UMPA) and an optimized scan protocol, we reached a resolution below 4 microns in scan times less than two hours. We investigated stained and unstained tissue samples, to quantify the staining process of different tissue types and were able to observe an increase in electron density, dependent on the stain and tissue type. By this, we could show the successful operation of our setup to quantitatively investigate samples on a micro meter scale at the beamline P05.
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