Image quality evaluation for FIB-SEM images.

Focused ion beam scanning electron microscopy (FIB-SEM) tomography is a serial sectioning technique where an FIB mills off slices from the material sample that is being analysed. After every slicing, an SEM image is taken showing the newly exposed layer of the sample. By combining all slices in a stack, a 3D image of the material is generated. However, specific artefacts caused by the imaging technique distort the images, hampering the morphological analysis of the structure. Typical quality problems in microscopy imaging are noise and lack of contrast or focus. Moreover, specific artefacts are caused by the FIB milling, namely, curtaining and charging artefacts. We propose quality indices for the evaluation of the quality of FIB-SEM data sets. The indices are validated on real and experimental data of different structures and materials.

3D analysis of microvasculature in murine liver fibrosis models using synchrotron radiation-based microtomography.

Cirrhosis describes the development of excess fibrous tissue around regenerative nodules in response to chronic liver injury and usually leads to irreversible organ damage and end-stage liver disease. During the development of cirrhosis, the formation of collagenous scar tissue is paralleled by a reorganization and remodeling of the hepatic vascular system. To date, macrovascular remodeling in various cirrhosis models has been examined using three-dimensional (3D) imaging modalities, while microvascular changes have been studied mainly by two-dimensional (2D) light microscopic and electron microscopic imaging. Here, we report on the application of high-resolution 3D synchrotron radiation-based microtomography (SRµCT) for the study of the sinusoidal and capillary blood vessel system in three murine models of advanced parenchymal and biliary hepatic fibrosis. SRµCT facilitates the characterization of microvascular architecture and identifies features of intussusceptive angiogenesis in progressive liver fibrosis in a non-destructive 3D manner.

VoroCrack3d: An annotated semi-synthetic 3d image data set of cracked concrete.

Sustainability is an important topic in the field of materials science and civil engineering. In particular, concrete, as a building material, needs to be of high quality to ensure its durability. Damage and failure processes such as cracks in concrete can be evaluated non-destructively by micro-computed tomography. Cracks can be detected in the images, for example via edge-detection filters or machine learning models. To study the goodness, robustness, and generalizability of these methods, annotated 3d image data are of fundamental importance. However, data acquisition and, in particular, its annotation is often tedious and error-prone. To overcome data shortage, realistic data can be synthesized. The data set described in this article addresses the lack of freely available annotated 3d images of cracked concrete. To this end, seven concrete samples without cracks were scanned via micro-computed tomography. Realizations of a dedicated stochastic geometry model are discretized to binary images and morphologically transformed to mimic real crack structures. These are superimposed on the concrete images and simultaneously yield the label images that distinguish crack from non-crack regions. The data set contains 1 344 of such image pairs and includes a large variety of crack structures. The data set may be used for training machine learning models and for objectively testing crack segmentation methods.

Predicting the Tensile Behaviour of Ultra-High Performance Fibre-Reinforced Concrete from Single-Fibre Pull-Out Tests.

In this paper, a prediction model for the tensile behaviour of ultra-high performance fibre-reinforced concrete is proposed. It is based on integrating force contributions of all fibres crossing the crack plane. Piecewise linear models for the force contributions depending on fibre orientation and embedded length are fitted to force-slip curves obtained in single-fibre pull-out tests. Fibre characteristics in the crack are analysed in a micro-computed tomography image of a concrete sample. For more general predictions, a stochastic fibre model with a one-parametric orientation distribution is introduced. Simple estimators for the orientation parameter are presented, which only require fibre orientations in the crack plane. Our prediction method is calibrated to fit experimental tensile curves.

Reconstructing porous structures from FIB-SEM image data: Optimizing sampling scheme and image processing.

Nano-porous materials can be imaged spatially by focused ion beam scanning electron microscopy (FIB-SEM). This method generates a stack of SEM images that has to be segmented (or reconstructed) to serve as basis for structural characterization. To this end, we apply two state-of-the-art algorithms. We study the influence of the original image's voxel size on estimates of morphological characteristics and effective permeabilities. Special attention is paid to analyzing anisotropies due to the FIB-SEM typical anisotropic sampling. Quantitative comparison of morphological descriptors and flow properties of reconstructed data is enabled by the use of synthetic FIB-SEM sets for which a ground truth is available. Moreover, in that case, reconstruction parameters can be chosen optimally, too.

In situ demineralisation of human enamel studied by synchrotron-based X-ray microtomography--a descriptive pilot-study.

An in situ study was designed to investigate naturally developed demineralisation in human enamel in a widely non-destructive manner in combination with X-ray microtomography. Samples of human enamel were carried in the oral cavity of participants for 24 h daily for either 21 or 29 days using so-called intraoral mandibular appliances (ICTs). Demineralisation was thereby generated in a natural way without causing caries in the subjects' dentition. By employing synchrotron-based X-ray microtomography (XMT) in combination with volume image analysis, a quantification and three-dimensional visualisation of different stages of mineral density loss was possible. Basic features of the demineralised samples were similar to those reported in earlier in vitro studies. However, the analysed samples showed significant differences in the morphology of surface attack and the degree of mineral density loss depending on the carrier, the exposure time and the position within the ICT. In particular, the varying local conditions within a carrier's oral cavity seem to be different than in an in vitro study. Our results show that the combination of ICTs and quantitative image analysis applied to XMT data provides an analytical tool which is highly suited for the fundamental investigation of naturally developed demineralisation processes.