Quantifying the hydroxyapatite orientation near the ossification front in a piglet femoral condyle using X-ray diffraction tensor tomography

Abstract

While a detailed knowledge of the hierarchical structure and morphology of the extracellular matrix is considered crucial for understanding the physiological and mechanical properties of bone and cartilage, the orientation of collagen fibres and carbonated hydroxyapatite (HA) crystallites remains a debated topic. Conventional microscopy techniques for orientational imaging require destructive sample sectioning, which both precludes further studies of the intact sample and potentially changes the microstructure. In this work, we use X-ray diffraction tensor tomography to image non-destructively in 3D the HA orientation in a medial femoral condyle of a piglet. By exploiting the anisotropic HA diffraction signal, 3D maps showing systematic local variations of the HA crystallite orientation in the growing subchondral bone and in the adjacent mineralized growth cartilage are obtained. Orientation maps of HA crystallites over a large field of view (~ 3 × 3 × 3 mm3) close to the ossification (bone-growth) front are compared with high-resolution X-ray propagation phase-contrast computed tomography images. The HA crystallites are found to predominantly orient with their crystallite c-axis directed towards the ossification front. Distinct patterns of HA preferred orientation are found in the vicinity of cartilage canals protruding from the subchondral bone. The demonstrated ability of retrieving 3D orientation maps of bone-cartilage structures is expected to give a better understanding of the physiological properties of bones, including their propensity for bone-cartilage diseases.

Synchrotron X-ray Studies of the Structural and Functional Hierarchies in Mineralised Human Dental Enamel: A State-of-the-Art Review

“…Laboratory X-ray tensor tomography has been carried out to provide details of the orientation of human dentinal tubules [ 594 ], as well as enamel and dentine [ 595 ]. SAXS tensor tomography can be complemented with diffraction tensor tomography; for example, to study bone [ 596 ].…”

Orientational mapping of minerals in Pierre shale using X-ray diffraction tensor tomography

“…Our motivation for this work has been to study the spatial distributions and orientation of minerals in shales to better understand their physicochemical properties. We have inves-tigated if we could obtain the clay mineral orientation by applying XRDTT, similar to what has previously been carried out on bone by us (Mü rer et al, 2021) and others (Liebi et al, 2015(Liebi et al, , 2018; however, here we used a single tomography axis, thus significantly reducing the experimental complexity and the reconstruction computing time. In tensor tomography, when the solution is found by optimization of a large amount ($10 6 ) of parameters, the use of multiple tomography axes can be beneficial in adding more sampling points to prevent the optimization from stagnating in local minima.…”

“…For finegrained isotropic materials, X-ray diffraction computed tomography (XRD-CT) (Harding et al, 1987;Kleuker et al, 1998;Stock et al, 2008;Mü rer et al, 2018;Grü newald et al, 2020) currently allows 3D non-destructive determination of material composition, particle size, shape and crystal lattice parameters of millimetre-sized samples with spatial resolution typically in the 10 À1 -10 2 micrometre range (Birkbak et al, 2015;Palle et al, 2020). Reconstructed diffractograms can be combined with Rietveld refinement (Rietveld, 1969;Frølich et al, 2016) or Williamson-Hall analysis (Williamson & Hall, 1953;Mü rer et al, 2021) for accurate determination of material volume fractions, and hence be used to obtain accurate spatially resolved maps of sample composition, crystallite size and strain. XRD-CT normally requires that the specimen materials are fine grained and isotropic, ensuring that the scattering signal from each sample voxel is rotationally invariant (Feldkamp et al, 2009).…”

“…While traditional pole figure (texture) analysis aims to describe the averaged orientation distribution function valid for a presumably uniform sample (Bunge, 1969;Breiby & Samuelsen, 2003), tensor tomography can reconstruct 3D maps of the variations of the texture in heterogeneous nonuniform samples. SASTT and XRDTT have recently been demonstrated on bone (Liebi et al, 2015(Liebi et al, , 2018Guizar-Sicairos et al, 2020;Mü rer et al, 2021), polymers (Skjønsfjell et al, 2016) and brain tissue (Gao et al, 2019). While SASTT/ XRDTT have facilitated 3D orientational X-ray imaging, the experiments are time consuming because many (typically >10 6 ) diffraction patterns have to be collected to adequately probe the sample.…”

Non-destructive 3D orientational mapping of bone using diffractive X-ray tomography

“…This is crucial for reconstructing evolutionary scenarios and biomechanical models of extinct species, for which soft tissues are lost during fossilization. X-ray diffraction computed tomography (XRD-CT) is an emerging imaging technique, allowing non-destructive 3D mapping of samples with material-specific contrast [1] and has recently also been demonstrated with orientational contrast [2][3][4]. In this presentation we demonstrate the application of XRD-CT to study the microstructure of different types of bones without destructive sample sectioning.…”