We report on the design and experimental realization of a 2D x-ray grating interferometer. We describe how this interferometer has been practically implemented, discuss its performance, and present ...multidirectional scattering (dark-field) maps and quantitative phase images that have been retrieved using this device.
Bone material contains a hierarchical network of micro‐ and nano‐cavities and channels, known as the lacuna‐canalicular network (LCN), that is thought to play an important role in mechanobiology and ...turnover. The LCN comprises micrometer‐sized lacunae, voids that house osteocytes, and submicrometer‐sized canaliculi that connect bone cells. Characterization of this network in three dimensions is crucial for many bone studies. To quantify X‐ray Zernike phase‐contrast nanotomography data, deep learning is used to isolate and assess porosity in artifact‐laden tomographies of zebrafish bones. A technical solution is proposed to overcome the halo and shade‐off domains in order to reliably obtain the distribution and morphology of the LCN in the tomographic data. Convolutional neural network (CNN) models are utilized with increasing numbers of images, repeatedly validated by `error loss' and `accuracy' metrics. U‐Net and Sensor3D CNN models were trained on data obtained from two different synchrotron Zernike phase‐contrast transmission X‐ray microscopes, the ANATOMIX beamline at SOLEIL (Paris, France) and the P05 beamline at PETRA III (Hamburg, Germany). The Sensor3D CNN model with a smaller batch size of 32 and a training data size of 70 images showed the best performance (accuracy 0.983 and error loss 0.032). The analysis procedures, validated by comparison with human‐identified ground‐truth images, correctly identified the voids within the bone matrix. This proposed approach may have further application to classify structures in volumetric images that contain non‐linear artifacts that degrade image quality and hinder feature identification.
A deep‐learning processing approach is proposed to assess in three dimensions the micro‐ and nano‐porosity in bone imaged by Zernike nano‐computed tomography.
Nephrotoxicity is an important drug safety aspect to be assessed during drug discovery and development. To study renal toxicity, in vitro cell-based assays are often used. Unfortunately, translating ...the results of such cell assays to vertebrates including human remains challenging. Therefore, we aim to evaluate whether zebrafish larvae (ZFL) could serve as a vertebrate screening model to detect gentamicin-induced changes of kidney glomeruli and proximal tubules. To validate the model, we compared the results of ZFL with those obtained from kidney biopsies of gentamicin-treated mice. We used transgenic zebrafish lines expressing enhanced green fluorescent proteins in the glomerulus to visualize glomerular damage. Synchrotron radiation-based computed tomography (SRμCT) is a label-free approach providing three-dimensional representations of renal structures with micrometre resolution. Clinically used gentamicin concentrations induce nephrotoxicity and affect glomerular and proximal tubular morphology. Findings were confirmed in mice and ZFL. There was a strong correlation between fluorescent signals in ZFL, SRμCT- derived descriptors of glomerular and proximal tubular morphology and the histological analysis of mouse kidney biopsies. A combination of SRμCT and confocal microscopy provides unprecedented insights into anatomical structures of the zebrafish kidney. Based on our findings, we suggest to use ZFL as a predictive vertebrate screening model to study drug-induced nephrotoxicity and to bridge the gap between cell culture-based test systems and experiments in mammals.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Magnesium (Mg) is one of the most promising materials for human use in surgery due to material characteristics such as its elastic modulus as well as its resorbable and regenerative properties. In ...this study, HF-coated and uncoated novel bioresorbable magnesium fixation screws for maxillofacial and dental surgical applications were investigated in vitro and in vivo to evaluate the biocompatibility of the HF coating.
Mg alloy screws that had either undergone a surface treatment with hydrofluoric-acid (HF) or left untreated were investigated. In vitro investigation included XTT, BrdU and LDH in accordance with the DIN ISO 10993-5/-12. In vivo, the screws were implanted into the tibia of rabbits. After 3 and 6 weeks, degradation, local tissue reactions and bony integration were analyzed histopathologically and histomorphometrically. Additionally, SEM/EDX analysis and synchrotron phase-contrast microtomography (µCT) measurements were conducted. The in vitro analyses revealed that the Mg screws are cytocompatible, with improved results when the surface had been passivated with HF. In vivo, the HF-treated Mg screws implanted showed a reduction in gas formation, slower biodegradation and a better bony integration in comparison to the untreated Mg screws. Histopathologically, the HF-passivated screws induced a layer of macrophages as part of its biodegradation process, whereas the untreated screws caused a slight fibrous tissue reaction. SEM/EDX analysis showed that both screws formed a similar layer of calcium phosphates on their surfaces and were surrounded by bone. Furthermore, the µCT revealed the presence of a metallic core of the screws, a faster absorbing corrosion front and a slow absorbing region of corroded magnesium.
Overall, the HF-passivated Mg fixation screws showed significantly better biocompatibility in vitro and in vivo compared to the untreated screws.
Human brain tissue belongs to the most impressive and delicate three-dimensional structures in nature. Its outstanding functional importance in the organism implies a strong need for brain imaging ...modalities. Although magnetic resonance imaging provides deep insights, its spatial resolution is insufficient to study the structure on the level of individual cells. Therefore, our knowledge of brain microstructure currently relies on two-dimensional techniques, optical and electron microscopy, which generally require severe preparation procedures including sectioning and staining. X-ray absorption microtomography yields the necessary spatial resolution, but since the composition of the different types of brain tissue is similar, the images show only marginal contrast. An alternative to absorption could be X-ray phase contrast, which is known for much better discrimination of soft tissues but requires more intricate machinery. In the present communication, we report an evaluation of the recently developed X-ray grating interferometry technique, applied to obtain phase-contrast as well as absorption-contrast synchrotron radiation-based microtomography of human cerebellum. The results are quantitatively compared with synchrotron radiation-based microtomography in optimized absorption-contrast mode. It is demonstrated that grating interferometry allows identifying besides the blood vessels, the stratum moleculare, the stratum granulosum and the white matter. Along the periphery of the stratum granulosum, we have detected microstructures about 40 µm in diameter, which we associate with the Purkinje cells because of their location, size, shape and density. The detection of individual Purkinje cells without the application of any stain or contrast agent is unique in the field of computed tomography and sets new standards in non-destructive three-dimensional imaging.
Bioresorbable magnesium scaffolds are a promising future treatment option for coronary artery stenosis, especially for young adults. Due to the degradation of these scaffolds (<1 year), long-term ...device-related clinical events could be reduced compared to treatments with conventional drug eluting stents. First clinical trials indicate a return of vasomotion after one year, which may be associated with improved long-term clinical outcomes. However, even after decades of development, the degradation process, ideal degradation time and biological response in vivo are still not fully understood.
The present study investigates the in vivo degradation of magnesium scaffolds in the coronary arteries of pigs influenced by different strut thicknesses and the presence of antiproliferative drugs. Due to high 3D image contrast of synchrotron-based micro-CT with phase contrast (SR-μCT), a qualitative and quantitative evaluation of the degradation morphology of magnesium scaffolds was obtained. For the segmentation of the μCT images a convolutional network architecture (U-net) was exploited, demonstrating the huge potential of merging high resolution SR-μCT with deep learning (DL) supported data analysis.
In total, 30 scaffolds, made of the rare earth alloy Resoloy®, with different strut designs were implanted into the coronary arteries of 10 domestic pigs for 28 days using drug-coated or uncoated angioplasty balloons for post-dilatation. The degradation morphology was analyzed using scanning electron microscopy, energy dispersive x-ray spectroscopy and SR-μCT. The data from these methods were then related to data from angiography, optical coherence tomography and histology.
A thinner strut size (95 vs. 130 μm) and the presence of paclitaxel indicated a slower degradation rate at 28 d in vivo, which positively influences the late lumen loss (0.5 and 0.6 mm vs. 1.0 and 1.1 mm) and recoil values (0 and 1.7% vs. 6.1 and 22%).
A key problem in X-ray computed tomography is choosing photon energies for postmortem specimens containing both soft and hard tissues. Increasing X-ray energy reduces image artifacts from highly ...absorbing hard tissues including plaque, but it simultaneously decreases contrast in soft tissues including the endothelium. Therefore, identifying the lumen within plaque-containing vessels is challenging. Destructive histology, the gold standard for tissue evaluation, reaches submicron resolution in two dimensions, whereas slice thickness limits spatial resolution in the third. We present a protocol to systematically analyze heterogeneous tissues containing weakly and highly absorbing components in the original wet state, postmortem. Taking the example of atherosclerotic human coronary arteries, the successively acquired 3D data of benchtop and synchrotron radiation-based tomography are validated by histology. The entire protocol requires ∼20 working days, enables differentiation between plaque, muscle and fat tissues without using contrast agents and permits blood flow simulations in vessels with plaque-induced constrictions.
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