Characterization of Normal Bone in the Equine Distal Limb with Effective Atomic Number and Electron Density Determined with Single-Source Dual Energy and Detector-Based Spectral Computed Tomography.

Single-source dual energy (SSDECT) and detector-based spectral computed tomography (DBSCT) are emerging technologies allowing the interrogation of materials that have different attenuation properties at different energies. Both technologies enable the calculation of effective atomic number (EAN), an index to determine tissue composition, and electron density (ED), which is assumed to be associated with cellularity in tissues. In the present prospective observational study, EAN and ED values were determined for 16 zones in normal subchondral and trabecular bone of 37 equine cadaver limbs. Using both technologies, the following findings were obtained: 1. palmar/plantar EAN zone values in the fetlock increased significantly with increasing age of the horse; 2. all EAN and ED values were significantly lower in the trabecular bone than in the subchondral bone of all phalanges; 3. in the distal phalanx and navicular bone, most EAN and ED values were significantly lower compared to the proximal and middle phalanx; and 4. some EAN and ED values were significantly different between front and hind limbs. Several EAN and ED values significantly differed between SSDECT and DBSCT. The reported EAN and ED values in the subchondral and trabecular bone of the equine distal limb may serve as preliminary reference values and aid future evaluation and classification of diseases.

Spherical Agglomerates of Lactose Reduce Segregation in Powder Blends and Improve Uniformity of Tablet Content at High Drug Loads.

We report here on improved uniformity of blends of micronised active pharmaceutical ingredients (APIs) using addition of spherical agglomerates of lactose and enhanced blend flow to improve tablet content uniformity with higher API loads. Micromeritic properties and intra-particle porosity (using nano-computed X-ray tomography) of recently introduced spherical agglomerates of lactose and two standard lactose grades for the direct compression processes were compared. Powder blends of the individual lactose types and different micronised API drug loads were prepared and subjected to specific conditions that can induce API segregation. Tablet content uniformity during direct compression was related to the lactose material attributes. The distinctive micromeritic properties of the lactose types showed that spherical agglomerates of lactose had high intra-particle porosity and increased specific surface area. The stability of binary blends after intense sieving was governed by the intra-particle porosity and surface roughness of the lactose particles, which determined the retention of the model substance. Greater intra-particle porosity, powder specific surface area, and particle size of the spherical agglomerates provided greater adhesion of micronised particles, compared to granulated and spray-dried lactose. Thus the spherical agglomerates provided enhanced final blend flow and uniformity of tablet content at higher drug loads.

Predicting the macroscopic response of electrospun membranes based on microstructure and single fibre properties.

In the present paper, the three-dimensional structure and macroscopic mechanical response of electrospun poly(L-lactide) membranes is predicted based only on the geometry and elasto-plastic mechanical properties of single fibres supplemented by measurements of membrane weight and volume, and the resulting computational models are used to study the non-affine micro-kinematics of electrospun networks. To this end, statistical parameters describing the in-plane fibre morphology are extracted from scanning electron micrographs of the membranes, and computational network models are generated by matching the porosity of the real mats. The virtual networks are compared against computed tomography scans in terms of structure, and against uniaxial tension tests with respect to their macroscopic mechanical response. The obtained virtual network structure agrees well with the fibre disposition in real networks, and the rigorous prediction of the mechanical response of two membranes with mean diameters of 1.10µm and 0.70µm captures the experimental behaviour qualitatively. Favourable quantitative agreement, however, is obtained only after lowering the Young's moduli, yield stresses and hardening slopes determined in single fibre tests, and after reducing the density of inter-fibre bonds in the model of the membrane with thinner fibres. The simulations thus demonstrate the validity and merits of the approach to study the multi-scale mechanics of electrospun networks, but also point to potential discrepancies between the properties of electrospun fibres within a network and those produced for single fibre characterisation, and highlight the existing uncertainty on the density and quality of bonds between fibres in electrospun networks.

Bone mineral density, mechanical properties, and trabecular orientation of cancellous bone within humeral heads affected by advanced shoulder arthropathy.

The mechanical properties of cancellous bone in the humeral head are increasingly interesting due to the increased popularity of stemless prosthetic fixation in the cancellous bone of the metaphysis. Age or pathology-related systemic osteoporosis, inactivity, or pathology of the shoulder joint may influence the primary bonding of implants that rely on good cancellous bone quality. We assessed the bone mineral density (BMD) and anisotropy using micro-computed tomography (micro-CT) (0.04 mm voxel size) and correlated the results with indentation load/displacement response. Resected parts of humeral heads (from patients undergoing total shoulder replacement, n = 18) were used as probes. The region of interest was defined as 2 mm medial from the resection plane, presuming that it mirrored the bone quality lateral to the resection plane. The indentation tests were performed with a large probe (diameter 10 mm) in a single destructive loading procedure. The BMD and trabecular orientation were determined by micro-CT. Our results showed a correlation between the BMD and the slope of the load/displacement curve. Furthermore, the trabeculae were predominantly oriented orthogonal to the joint surface. In conclusion, the predominant factor determining the bone quality and mechanical resistance to pressure appears to be the BMD, while trabecular orientation could not be related to load/displacement response. Statement of clinical significance: Bone quality predominately determines the mechanical properties of cancellous bone. This might be crucial when prosthetic implants need to be anchored in metaphyseal bone. Therefore, clinical decision-making processes should also include local BMD measurements.

A novel approach to increase robustness, precision and high-throughput capacity of single cell gel electrophoresis.

The routine use of single cell gel electrophoresis assay in medical diagnostics and biomonitoring is prevented by its high variability. Several factors have been identified and can be grouped into four main categories: 1) the biological sample, 2) the assay protocol, 3) the physical parameters during electrophoresis and 4) the analysis. Even though the scientific knowledge on assay variability is available, not much has been done so far to tackle the issues from the technological side. Therefore, this study addresses the question in how far the precise and accurate control over the physical parameters of electrophoresis is able to reduce variability of single cell gel electrophoresis assay results. All four above mentioned categories make up the overall assay variability. To resolve the contribution from a single category, the remaining three have to be kept as constant as possible. To achieve this we generated a set of x-ray treated control cells, worked according to a well-defined standard operating procedure and one single operator performed the analysis. Thereby variability resulting from the electrophoresis tank could be elucidated. We compared assay performance in two such tank systems: a newly developed electrophoresis tank that accurately controls voltage, temperature during the electrophoretic run and the homogeneity of the electric field, and a widely used commercially available standard platform tank. In summary, our results demonstrate that, irrespective of the cellular sample and its intrinsic biological variability, accurate control over physical parameters considerably increases repeatability, reproducibility and precision of single cell gel electrophoresis.

Differentiation of dental restorative materials combining energy-dispersive X-ray fluorescence spectroscopy and post-mortem CT.

Today, post-mortem computed tomography (CT) is routinely used for forensic identification. Mobile energy-dispersive X-ray fluorescence (EDXRF) spectroscopy of a dentition is a method of identification that has the potential to be easier and cheaper than CT, although it cannot be used with every dentition. In challenging cases, combining both techniques could facilitate the process of identification and prove to be advantageous over chemical analyses. Nine dental restorative material brands were analyzed using EDXRF spectroscopy. Their differentiability was assessed by comparing each material's x-ray fluorescence spectrum and then comparing the spectra to previous research investigating differentiability in CT. To verify EDXRF's precision and accuracy, select dental specimens underwent comparative electron beam excited x-ray spectroscopy (EDS) scans, while the impact of the restorative surface area was studied by scanning a row of dental specimens with varying restorative surface areas (n = 10). EDXRF was able to differentiate all 36 possible pairs of dental filling materials; however, dual-energy CT was only able to differentiate 33 out of 36. The EDS scans showed correlating x-ray fluorescence peaks on the x-ray spectra compared to our EDXRF. In addition, the surface area showed no influence on the differentiability of the dental filling materials. EDXRF has the potential to facilitate corpse identification by differentiating and comparing restorative materials, providing more information compared to post-mortem CT alone. Despite not being able to explicitly identify a brand without a control sample or database, its fast and mobile use could accelerate daily routines or mass victim identification processes. To achieve this goal, further development of EDXRF scanners for this application and further studies evaluating the method within a specific routine need to be performed.

Biofilms in 3D porous media: Delineating the influence of the pore network geometry, flow and mass transfer on biofilm development.

This study investigates the functional correspondence between porescale hydrodynamics, mass transfer, pore structure and biofilm morphology during progressive biofilm colonization of a porous medium. Hydrodynamics and the structure of both the porous medium and the biofilm are experimentally measured with 3D particle tracking velocimetry and micro X-ray Computed Tomography, respectively. The analysis focuses on data obtained in a clean porous medium after 36 h of biofilm growth. Registration of the particle tracking and X-ray data sets allows to delineate the interplay between porous medium geometry, hydrodynamic and mass transfer processes on the morphology of the developing biofilm. A local analysis revealed wide distributions of wall shear stresses and concentration boundary layer thicknesses. The spatial distribution of the biofilm patches uncovered that the wall shear stresses controlled the biofilm development. Neither external nor internal mass transfer limitations were noticeable in the considered system, consistent with the excess supply of nutrient and electron acceptors. The wall shear stress remained constant in the vicinity of the biofilm but increased substantially elsewhere.

Investigation of the Axial Gap Clearance in a Hydrodynamic-Passive Magnetically Levitated Rotary Blood Pump Using X-Ray Radiography.

The HeartWare HVAD is a radial rotary blood pump with a combination of passive magnetic and hydrodynamic bearings to levitate the impeller. The axial gap size between impeller and housing in this bearing and its sensitivity to speed, flow, and pressure difference is difficult to assess. Shear stresses are exceptionally high in this tiny gap making it important for blood damage and related adverse events. Therefore, the aim of this study was to measure the axial gap clearance in the HVAD at different operating conditions employing radiography. To quantify the gap size in the HVAD, the pump was positioned 30 mm in front of the X-ray source employing a microfocus X-ray tube with an acceleration voltage up to 300 kV. Beams were detected on a flat panel detector (Perkin Elmer XRD 1611-CP3). The pump was connected to a tubing circuit with a throttle to adjust flow (0, 5, 10 L/min) and a water glycerol mixture to set the desired viscosity (1, 4, 8 mPas). Rotational speed was varied between 1800 and 3600 rpm. In this study, for clinically relevant conditions at 5 L/min and 2700 rpm, the axial gap was 22 µm. The gap size increased with rotational speeds dependent on the viscosity (2.8, 6.9, and 9.4 µm/1000 rpm for 1, 4, and 8 mPas, respectively), but was independent from the volume flow and the pressure head at constant speeds. In summary, using X-ray radiographic imaging small gaps in a rotary blood pump during operation can be measured in a nondestructive contact-free way. The axial hydrodynamic bearing gap in the HVAD pump was determined to be in the range of about three times the diameter of a red blood cell. Its dependence on operating volume flow and generated pressure head across the pump is not pronounced.

Correction: Biofilm imaging in porous media by laboratory X-Ray tomography: Combining a non-destructive contrast agent with propagation-based phase-contrast imaging tools.

[This corrects the article DOI: 10.1371/journal.pone.0180374.].

Biofilm imaging in porous media by laboratory X-Ray tomography: Combining a non-destructive contrast agent with propagation-based phase-contrast imaging tools.

X-ray tomography is a powerful tool giving access to the morphology of biofilms, in 3D porous media, at the mesoscale. Due to the high water content of biofilms, the attenuation coefficient of biofilms and water are very close, hindering the distinction between biofilms and water without the use of contrast agents. Until now, the use of contrast agents such as barium sulfate, silver-coated micro-particles or 1-chloronaphtalene added to the liquid phase allowed imaging the biofilm 3D morphology. However, these contrast agents are not passive and potentially interact with the biofilm when injected into the sample. Here, we use a natural inorganic compound, namely iron sulfate, as a contrast agent progressively bounded in dilute or colloidal form into the EPS matrix during biofilm growth. By combining a very long source-to-detector distance on a X-ray laboratory source with a Lorentzian filter implemented prior to tomographic reconstruction, we substantially increase the contrast between the biofilm and the surrounding liquid, which allows revealing the 3D biofilm morphology. A comparison of this new method with the method proposed by Davit et al (Davit et al., 2011), which uses barium sulfate as a contrast agent to mark the liquid phase was performed. Quantitative evaluations between the methods revealed substantial differences for the volumetric fractions obtained from both methods. Namely, contrast agent-biofilm interactions (e.g. biofilm detachment) occurring during barium sulfate injection caused a reduction of the biofilm volumetric fraction of more than 50% and displacement of biofilm patches elsewhere in the column. Two key advantages of the newly proposed method are that passive addition of iron sulfate maintains the integrity of the biofilm prior to imaging, and that the biofilm itself is marked by the contrast agent, rather than the liquid phase as in other available methods. The iron sulfate method presented can be applied to understand biofilm development and bioclogging mechanisms in porous materials and the obtained biofilm morphology could be an ideal basis for 3D numerical calculations of hydrodynamic conditions to investigate biofilm-flow coupling.

Comment on 'A new method for fusion, denoising and enhancement of x-ray images retrieved from Talbot-Lau grating interferometry'.

In a recent paper (Scholkamm et al 2014 Phys. Med. Biol. 59 1425-40) we presented a new image denoising, fusion and enhancement framework for combining and optimal visualization of x-ray attenuation contrast, differential phase contrast and dark-field contrast images retrieved from x-ray Talbot-Lau grating interferometry. In this comment we give additional information and report about the application of our framework to breast cancer tissue which we presented in our paper as an example. The applied procedure is suitable for a qualitative comparison of different algorithms. For a quantitative juxtaposition original data would however be needed as an input.

A new method for fusion, denoising and enhancement of x-ray images retrieved from Talbot-Lau grating interferometry.

This paper introduces a new image denoising, fusion and enhancement framework for combining and optimal visualization of x-ray attenuation contrast (AC), differential phase contrast (DPC) and dark-field contrast (DFC) images retrieved from x-ray Talbot-Lau grating interferometry. The new image fusion framework comprises three steps: (i) denoising each input image (AC, DPC and DFC) through adaptive Wiener filtering, (ii) performing a two-step image fusion process based on the shift-invariant wavelet transform, i.e. first fusing the AC with the DPC image and then fusing the resulting image with the DFC image, and finally (iii) enhancing the fused image to obtain a final image using adaptive histogram equalization, adaptive sharpening and contrast optimization. Application examples are presented for two biological objects (a human tooth and a cherry) and the proposed method is compared to two recently published AC/DPC/DFC image processing techniques. In conclusion, the new framework for the processing of AC, DPC and DFC allows the most relevant features of all three images to be combined in one image while reducing the noise and enhancing adaptively the relevant image features. The newly developed framework may be used in technical and medical applications.

Reduction of phase artifacts in differential phase contrast computed tomography.

X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer setup allows visualizing the three-dimensional distribution of the refractive index by measuring the shifts of an interference pattern due to phase variations of the X-ray beam. Unfortunately, severe reconstruction artifacts appear in the presence of differential phase wrapping and clipping. In this paper, we propose to use the attenuation contrast, which is obtained from the same measurement, for correcting the DPC signal. Using the example of a DPC CT measurement with pronounced phase artifacts, we will discuss the efficiency of our phase artifact correction method.

Noise analysis of grating-based x-ray differential phase contrast imaging.

The sensitivity of x-ray radiographic images, meaning the minimal detectable change in the thickness or in the index of refraction of a sample, is directly related to the uncertainty of the measurement method. In the following work, we report on the recent development of quantitative descriptions for the stochastic error of grating-based differential phase contrast imaging (DPCi). Our model includes the noise transfer characteristics of the x-ray detector and the jitter of the phase steps. We find that the noise in DPCi depends strongly on the phase stepping visibility and the sample properties. The results are supported by experimental evidence acquired with our new instrument with a field of view of 50x70 mm(2). Our conclusions provide general guidelines to optimize grating interferometers for specific applications and problems.