Publications by authors named "Klaus Achterhold"

Speckle-based X-ray imaging (SBI) is a phase-contrast method developed at and for highly coherent X-ray sources, such as synchrotrons, to increase the contrast of weakly absorbing objects. Consequently, it complements the conventional attenuation-based X-ray imaging. Meanwhile, attempts to establish SBI at less coherent laboratory sources have been performed, ranging from liquid metal-jet X-ray sources to microfocus X-ray tubes.

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The introduction of mammography screening programs has significantly reduced breast cancer mortality rates. Nevertheless, some lesions remain undetected, especially in dense breast tissue. Studies have shown that phase-contrast imaging can improve breast cancer diagnosis by increasing soft tissue contrast.

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Article Synopsis
  • Optimizing the binding energy at active sites is essential for improving the selectivity and activity of catalysts in the electrochemical reduction of CO2. !* -
  • Copper is effective in reducing CO to hydrocarbons but struggles with product selectivity due to moderate binding energies of intermediates; a new Cu-Pd dimer structure is proposed using a metal-organic framework (MOF) to address this issue. !* -
  • The incorporation of palladium into the Cu-Pd structure enhances the adsorption of the COOH* intermediate, leading to more selective generation of carbon monoxide and deepening the understanding of catalyst structure-activity relationships. !*
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Chelicerae, the mouthparts of chelicerates, are essential for food processing. Particularly within harvestmen (Opiliones), some species have greatly elongated their tripartite chelicerae and utilize them for mating behavior, defense, and primarily for predation. We investigated two European species, Ischyropsalis muellneri and Ischyropsalis hellwigii, which occupy different niches (caves, forests), exhibit different feeding ecologies (opportunist, specialist), and first and foremost possess different chelicerae morphologies (long and thin, short and robust).

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Background Many clinically relevant fractures are occult on conventional radiographs and therefore challenging to diagnose reliably. X-ray dark-field radiography is a developing method that uses x-ray scattering as an additional signal source. Purpose To investigate whether x-ray dark-field radiography enhances the depiction of radiographically occult fractures in an experimental model compared with attenuation-based radiography alone and whether the directional dependence of dark-field signal impacts observer ratings.

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X-ray diffraction (XRD) is an important material analysis technique with a widespread use of laboratory systems. These systems typically operate at low X-ray energies (from 5 keV to 22 keV) since they rely on the small bandwidth of K-lines like copper. The narrow bandwidth is essential for precise measurements of the crystal structure in these systems.

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X-ray absorption spectroscopy (XAS) is an element-selective technique that provides electronic and structural information of materials and reveals the essential mechanisms of the reactions involved. However, the technique is typically conducted at synchrotrons and usually only probes one element at a time. In this paper, a simultaneous two-color XAS setup at a laboratory-scale synchrotron facility is proposed based on inverse Compton scattering (ICS) at the Munich Compact Light Source (MuCLS), which is based on inverse Compton scattering (ICS).

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While K-edge subtraction (KES) imaging is a commonly applied technique at synchrotron sources, the application of this imaging method in clinical imaging is limited although results have shown its superiority to conventional clinical subtraction imaging. Over the past decades, compact synchrotron X-ray sources, based on inverse Compton scattering, have been developed to fill the gap between conventional X-ray tubes and synchrotron facilities. These so called inverse Compton sources (ICSs) provide a tunable, quasi-monochromatic X-ray beam in a laboratory setting with reduced spatial and financial requirements.

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Article Synopsis
  • - Inverse Compton scattering is a method for generating high-quality quasi-monochromatic X-ray radiation, making synchrotron techniques more accessible for use in labs and industry.
  • - The Munich Compact Light Source is a compact facility utilizing this technology, with improvements to the X-ray source discussed and various suitable experimental techniques detailed.
  • - A multipurpose X-ray application beamline with two end-stations is designed for diverse experiments, including imaging and spectroscopy, with future upgrades planned to enhance its functionalities.
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Purpose: X-ray microbeam radiation therapy is a preclinical concept for tumor treatment promising tissue sparing and enhanced tumor control. With its spatially separated, periodic micrometer-sized pattern, this method requires a high dose rate and a collimated beam typically available at large synchrotron radiation facilities. To treat small animals with microbeams in a laboratory-sized environment, we developed a dedicated irradiation system at the Munich Compact Light Source (MuCLS).

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X-ray fluoroscopy is a commonly applied diagnostic tool for morphological and functional evaluation of the intestine in clinical routine. Acquisition of repetitive X-ray images following oral or rectal application of iodine contrast agent visualizes the time dependent distribution of the contrast medium, and helps to detect for example leakages, tumors or functional disorders. However, movements of the intestine and air trapped inside usually prevent temporal subtraction imaging to be applied to fluoroscopy of the gastrointestinal tract.

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Novel compact x-ray sources based on inverse Compton scattering can generate brilliant hard x-rays in a laboratory setting. Their collimated intense beams with tunable well-defined x-ray energies make them well suited for x-ray spectroscopy techniques, which are typically carried out at large facilities. Here, we demonstrate a first x-ray absorption spectroscopy proof-of-principle experiment using an inverse Compton x-ray source with a flux of >10 photons/s in <5% bandwidth.

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Article Synopsis
  • - Screening mammography has reduced breast cancer mortality, but many women still face unnecessary follow-ups due to unclear diagnoses, especially in the context of dense breast tissue which complicates image quality.
  • - Phase-contrast imaging can significantly enhance image quality by improving spatial resolution and contrast-to-noise ratio (CNR), while also reducing radiation dose by up to 20%.
  • - The study showed that this advanced imaging technique offers better diagnostic capabilities, evidenced by higher resolution and CNR in mammograms taken with monochromatic radiation compared to standard methods.
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About one third of all deaths worldwide can be traced to some form of cardiovascular disease. The gold standard for the diagnosis and interventional treatment of blood vessels is digital subtraction angiography (DSA). An alternative to DSA is K-edge subtraction (KES) imaging, which has been shown to be advantageous for moving organs and for eliminating image artifacts caused by patient movement.

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In the field of correlative microscopy, light and electron microscopy form a powerful combination for morphological analyses in zoology. Due to sample thickness limitations, these imaging techniques often require sectioning to investigate small animals and thereby suffer from various artefacts. A recently introduced nanoscopic X-ray computed tomography (NanoCT) setup has been used to image several biological objects, none that were, however, embedded into resin, which is prerequisite for a multitude of correlative applications.

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We demonstrate a laboratory-based method combining X-ray microCT and nanoCT with a specific X-ray stain, which targets the cell cytoplasm. The described protocol is easy to apply, fast and suitable for larger soft-tissue samples. The presented methodology enables the characterization of crucial tissue structures in three dimensions and is demonstrated on a whole mouse kidney.

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Microbeam radiation therapy (MRT), a preclinical form of spatially fractionated radiotherapy, uses an array of microbeams of hard synchrotron X-ray radiation. Recently, compact synchrotron X-ray sources got more attention as they provide essential prerequisites for the translation of MRT into clinics while overcoming the limited access to synchrotron facilities. At the Munich compact light source (MuCLS), one of these novel compact X-ray facilities, a proof of principle experiment was conducted applying MRT to a xenograft tumor mouse model.

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Targeted delivery of nanomedicine/nanoparticles (NM/NPs) to the site of disease (e.g., the tumor or lung injury) is of vital importance for improved therapeutic efficacy.

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Article Synopsis
  • Mammography is the standard method for early breast cancer detection, but its sensitivity is limited due to overlapping anatomical structures.
  • Recent advancements, like contrast-enhanced spectral mammography (CESM) using K-edge subtraction, have improved the identification of suspicious findings.
  • A new approach using two-material decomposition demonstrates even better image quality and contrast-to-noise ratio compared to clinical CESM, potentially advancing breast cancer detection methods while using a lower mean glandular dose.
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In clinical diagnosis, X-ray computed tomography (CT) is one of the most important imaging techniques. Yet, this method lacks the ability to differentiate similarly absorbing substances like commonly used iodine contrast agent and calcium which is typically seen in calcifications, kidney stones and bones. K-edge subtraction (KES) imaging can help distinguish these materials by subtracting two CT scans recorded at different X-ray energies.

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Compact X-ray sources based on inverse Compton scattering provide brilliant and partially coherent X-rays in a laboratory environment. The cross section for inverse Compton scattering is very small, requiring high-power laser systems as well as small laser and electron beam sizes at the interaction point to generate sufficient flux. Therefore, these systems are very sensitive to distortions which change the overlap between the two beams.

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The complexity of lung diseases makes pre-clinical in vivo respiratory research in mouse lungs of great importance for a better understanding of physiology and therapeutic effects. Synchrotron-based imaging has been successfully applied to lung research studies, however longitudinal studies can be difficult to perform due to limited facility access. Laboratory-based x-ray sources, such as inverse Compton x-ray sources, remove this access limitation and opens up new possibilities for pre-clinical small-animal lung research at high spatial and temporal resolution.

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Background: Tardigrades (water bears) are microscopic invertebrates of which the anatomy has been well studied using traditional techniques, but a comprehensive three-dimensional reconstruction has never been performed. In order to close this gap, we employed X-ray computed tomography (CT), a technique that is becoming increasingly popular in zoology for producing high-resolution, three-dimensional (3D) scans of whole specimens. While CT has long been used to scan larger samples, its use in some microscopic animals can be problematic, as they are often too small for conventional CT yet too large for high-resolution, optics-based soft X-ray microscopy.

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