Evaluation of imaging setups for quantitative phase contrast nanoCT of mineralized biomaterials

Multiscale X-ray phase-contrast CT unveils the evolution of bile infarct in obstructive biliary disease

Bile infarct is a pivotal characteristic of obstructive biliary disease, but its evolution during the disease progression remains unclear. Our objective, therefore, is to explore morphological alterations of the bile infarct in the disease course by means of multiscale X-ray phase-contrast CT. Bile duct ligation is performed in mice to mimic the obstructive biliary disease. Intact liver lobes of the mice are scanned by phase-contrast CT at various resolution scales. Phase-contrast CT clearly presents three-dimensional (3D) images of the bile infarcts down to the submicron level with good correlation with histological images. The CT data illustrates that the infarct first appears on day 1 post-BDL, while a microchannel between the infarct and hepatic sinusoids is identified, the number of which increases with the disease progression. A 3D model of hepatic acinus is proposed, in which the infarct starts around the portal veins (zone I) and gradually progresses towards the central veins (zone III) during the disease process. Multiscale phase-contrast CT offers the comprehensive analysis of the evolutionary features of the bile infarct in obstructive biliary disease. During the course of the disease, the bile infarcts develop infarct-sinusoidal microchannels and gradually occupy the whole liver, promoting the disease progression.

3D interconnected porous PMMA scaffold integrating with advanced nanostructured CaP-based biomaterials for rapid bone repair and regeneration

Bioactive scaffolds with polymer and nanostructured bioactive glass-based composites are promising materials for regenerative applications in consequence of close mimics of natural bone composition. Poly methyl methacrylate (PMMA) is a highly preferred thermoplastic polymer for orthopedic applications as it has good biocompatibility. Different kinds of bioactive, biodegradable as well as biocompatible biomaterial composites such as Bioglass (BG), Hydroxyapatite (Hap), and Tricalcium phosphate (TCP) can be integrated with PMMA, so as to augment the bioactivity, porosity as well as regeneration of hard tissues in human body. Among the bioactive glass, 60S BG (Bioactive glass with 60 percentage of Silica without Sodium ions) is better materials among aforementioned systems owning to mechanical stability as well as controlled bioactive material. In this work, the fabrication of PMMA-CaP (calcium phosphate)-based scaffolds were carried out by Thermal Induced Phase Separation method (TIPS). X-ray diffractogram analysis (XRD) is used to examine the physiochemical properties of the scaffolds that evidently reveal the presence of calcium phosphate besides calcium phosphate silicate phases. The Field Emission Scanning Electron Microscopy (FESEM) studies obviously exhibited the microstructure of the scaffolds as well as their interconnected porous morphology. The PMMA/60S BG/TCP (C50) scaffold has the maximum pore size, measuring 77 ± 23 μm, while the average pore size ranges from 50 ± 20 to 80 ± 23 μm. By performing a liquid displacement method, the C50 scaffold is found to have the largest porosity of 50%, high hydrophilicity of 118.16°, and a compression test reveals the scaffolds to have a maximum compressive strength of 0.16 MPa. The emergence of bone-like apatite on the scaffold surface after 1st and 21st days of SBF immersion is further supported by in vitro bioactivity studies. Cytocompatibility and hemocompatibility analyses undoubtedly confirmed the biocompatibility behavior of PMMA-based bioactive scaffolds. Nano-CT investigation demonstrates that PMMA-CaP scaffolds provide more or less alike morphologies of composites that resemble the natural bone. Therefore, this combination of scaffolds could be considered as potential biomaterials for bone regeneration application. This detailed study promisingly demonstrates the eminence of the unique scaffolds in the direction of regenerative medicines.

In situ synchrotron radiation μCT indentation of cortical bone: Anisotropic crack propagation, local deformation, and fracture

The development of treatment strategies for skeletal diseases relies on the understanding of bone mechanical properties in relation to its structure at different length scales. At the microscale, indention techniques can be used to evaluate the elastic, plastic, and fracture behaviour of bone tissue. Here, we combined in situ high-resolution SRμCT indentation testing and digital volume correlation to elucidate the anisotropic crack propagation, deformation, and fracture of ovine cortical bone under Berkovich and spherical tips. Independently of the indenter type we observed significant dependence of the crack development due to the anisotropy ahead of the tip, with lower strains and smaller crack systems developing in samples indented in the transverse material direction, where the fibrillar bone ultrastructure is largely aligned perpendicular to the indentation direction. Such alignment allows to accommodate the strain energy, inhibiting crack propagation. Higher tensile hoop strains generally correlated with regions that display significant cracking radial to the indenter, indicating a predominant Mode I fracture. This was confirmed by the three-dimensional analysis of crack opening displacements and stress intensity factors along the crack front obtained for the first time from full displacement fields in bone tissue. The X-ray beam significantly influenced the relaxation behaviour independent of the tip. Raman analyses did not show significant changes in specimen composition after irradiation compared to non-irradiated tissue, suggesting an embrittlement process that may be linked to damage of the non-fibrillar organic matrix. This study highlights the importance of three-dimensional investigation of bone deformation and fracture behaviour to explore the mechanisms of bone failure in relation to structural changes due to aging or disease. STATEMENT OF SIGNIFICANCE: : Characterising the three-dimensional deformation and fracture behaviour of bone remains essential to decipher the interplay between structure, function, and composition with the aim to improve fracture prevention strategies. The experimental methodology presented here, combining high-resolution imaging, indentation testing and digital volume correlation, allows us to quantify the local deformation, crack propagation, and fracture modes of cortical bone tissue. Our results highlight the anisotropic behaviour of osteonal bone and the complex crack propagation patterns and fracture modes initiating by the intricate stress states beneath the indenter tip. This is of wide interest not only for the understanding of bone fracture but also to understand other architectured (bio)structures providing an effective way to quantify their toughening mechanisms in relation to their main mechanical function.

Deep Gauss-Newton for phase retrieval

We propose the deep Gauss-Newton (DGN) algorithm. The DGN allows one to take into account the knowledge of the forward model in a deep neural network by unrolling a Gauss-Newton optimization method. No regularization or step size needs to be chosen; they are learned through convolutional neural networks. The proposed algorithm does not require an initial reconstruction and is able to retrieve simultaneously the phase and absorption from a single-distance diffraction pattern. The DGN method was applied to both simulated and experimental data and permitted large improvements of the reconstruction error and of the resolution compared with a state-of-the-art iterative method and another neural-network-based reconstruction algorithm.

Multiscale Femoral Neck Imaging and Multimodal Trabeculae Quality Characterization in an Osteoporotic Bone Sample

Although multiple structural, mechanical, and molecular factors are definitely involved in osteoporosis, the assessment of subregional bone mineral density remains the most commonly used diagnostic index. In this study, we characterized bone quality in the femoral neck of one osteoporotic patients as compared to an age-matched control subject, and so used a multiscale and multimodal approach including X-ray computed microtomography at different spatial resolutions (pixel size: 51.0, 4.95 and 0.9 µm), microindentation and Fourier transform infrared spectroscopy. Our results showed abnormalities in the osteocytes lacunae volume (358.08 ± 165.00 for the osteoporotic sample vs. 287.10 ± 160.00 for the control), whereas a statistical difference was found neither for shape nor for density. The osteoporotic femoral head and great trochanter reported reduced elastic modulus (Es) and hardness (H) compared to the control reference (−48% (p < 0.0001) and −34% (p < 0.0001), respectively for Es and H in the femoral head and −29% (p < 0.01) and −22% (p < 0.05), respectively for Es and H in the great trochanter), whereas the corresponding values in the femoral neck were in the same range. The spectral analysis could distinguish neither subregional differences in the osteoporotic sample nor between the osteoporotic and healthy samples. Although, infrared spectroscopic measurements were comparable among subregions, and so regardless of the bone osteoporotic status, the trabecular mechanical properties were comparable only in the femoral neck. These results illustrate that bone remodeling in osteoporosis is a non-uniform process with different rates in different bone anatomical regions, hence showing the interest of a clear analysis of the bone microarchitecture in the case of patients’ osteoporotic evaluation.