Novel optical imaging technique to determine the 3-D orientation of collagen fibers in cartilage: variable-incidence angle polarization-sensitive optical coherence tomography

Objective: To investigate a novel optical method to determine the three dimensional (3-D) structure of articular cartilage collagen non-destructively. Methods: Polarization-sensitive optical coherence tomography was used to determine the apparent optical birefringence of articular cartilage for a number of different illumination directions. A quantitative method based on the theory of light propagation in uniaxial crystalline materials was validated on equine flexor tendon. Qualitative maps of fiber polar and azimuthal orientation at sites on the posterior and anterior segments of the equine third metacarpophalangeal (fetlock) joint were produced, and the azimuthal orientations compared with data from a split-line experiment. Results: Polar and azimuthal angles of cut flexor tendon broadly agreed with the nominal values but suggested that the accuracy was limited by our method of determining the apparent birefringence. On intact equine fetlock joints we found a non-zero polar tilt that changed in direction at various points along the apex, moving from the sagittal ridge outwards. The azimuthal orientation changes from being parallel to the sagittal ridge in the posterior region to being inclined to the ridge in the anterior region. This broadly agrees with split-line data for the anterior region but differs in the posterior region, possibly reflecting depth-dependent orientation changes. Conclusion: General quantitative agreement was found between our method and histology in validation experiments. Qualitative results for cartilage suggest a complicated 3-D structure that warrants further study. There is potential to develop this approach into a tool that can provide depth-resolved information on collagen orientation in near real-time, non-destructively and in vivo. (c) 2008 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved

Evaluation of a cheap ultrasonic stage for light source coherence function measurement, optical coherence tomography and dynamic focusing

We evaluate the performance of a cheap ultrasonic stage in setups related to optical coherence tomography. The stage was used in several configurations: (1) optical delay line in an optical coherence tomography (OCT) setup; (2) as a delay line measuring coherence function of a low coherence source (e. g. superluminescent diode) and (3) in a dynamic focusing arrangement. The results are as follows: the stage is suitable for coherence function measurement (coherence length up to 70 mu m) of the light source and dynamic focusing. We found it unsuitable for OCT due to an unstable velocity profile. Despite this, the velocity profile has a repeatable shape (4% over 1000 A-scans) and slight modifications to the stage promise wider applications

Imaging of 3D tissue-engineered models of oral cancer using 890 and 1300 nm optical coherence tomography

© 2015, Nizhny Novgorod State Medical Academy. All rights reserved. Optical coherence tomography (OCT) generates its primary form of contrast from elastic backscatter. It is now the gold standard technique for retinal screening and is emerging rapidly in cardiovascular research however it remains a research goal to establish it to the same degree in epithelial cancer detection and diagnosis. In this report we compare two different OCT systems: an 890 nm spectrometer-based OCT system with 2.5 µm axial resolution and a 1300 nm swept-source OCT system with 7.5 µm axial resolution to determine the effect of these different OCT parameters on the endogenous backscatter contrast of dysplastic/malignant oral mucosa models relative to normal mucosa models. Tissueengineered oral mucosa models constructed with a dysplastic cell line (DOK), a malignant cell line (Cal27) and normal cell were imaged with both of these OCT platforms and comparisons made with regard to apparent epithelial thickness and the visibility of the epithelium relative to the underlying stroma. For the Cal27’s, hematoxylin and eosin staining confirmed the formation of a keratinized layer superficial to a thickened layer of viable cells on top of the stroma. The keratinized layer presented as a hyperreflective thickened layer superficial to a darker region on both OCT platforms. The keratinized layer caused a steep fall in signal at 890 nm, making it difficult to visualise underlying structures, whereas 1300 nm OCT clearly visualized both the epithelial cells and the stroma lying beneath. For the DOK cells, hematoxylin and eosin staining confirmed the formation of an epithelial layer frequently presenting an abnormal morphology especially at the epidermal/stromal junction, with features such as infiltrating, bulbous rete pegs. These were more clearly visualized under 890 nm OCT. These observations show that 890 nm OCT retains some of its known advantages of higher contrast between anatomical tissue layers when used to observe dysplastic and malignant 3D oral mucosa constructs. However 1300 nm OCT is confirmed to possess a greater ability to image the full thickness of the model epithelia and in particular it is more suited to imaging through the keratinized layer

Meat freshness revealed by visible to near-infrared spectroscopy and principal component analysis

Increasing concerns about adulterated meat encouraged industry looking for new non-invasive methods for rapid accurate meat quality assessment. Main meat chromophores (myoglobin, oxy-myoglobin, fat, water, collagen) are characterized by close comparable absorption in visible to near-infrared (NIR) spectral region. Therefore, structural and compositional variations in meat may lead to relative differences in the absorption of light. Utilizing typical fiber-optic probes and integrating sphere, a degradation of pork samples freshness was observed at room temperature referring to the relative changes in absorbance of main meat chromophores. The application of principal component analysis (PCA) used for examination of measured absorbance spectra revealed more detailed sub-stages of freshness, which are not observed by the conventional analysis of the reflectance spectra. The results show a great potential of the combined application of optical-NIR spectroscopy with complementary use of PCA approach for assessing meat quality and monitoring relative absorbance alternation of oxymyoglobin and myoglobin in visible, and fat, water, collagen in NIR spectral ranges

Collagen fiber arrangement in normal and diseased cartilage studied by polarization sensitive nonlinear microscopy

Jessica C. Mansfield ; C. Peter Winlove ; Julian Moger and Steve J. Matcher "Collagen fiber arrangement in normal and diseased cartilage studied by polarization sensitive nonlinear microscopy", J. Biomed. Opt. 13(4), 044020 (July 15, 2008). Copyright © 2008 Society of Photo-Optical Instrumentation EngineersSecond harmonic generation (SHG) and two-photon fluorescence (TPF) microscopy is used to image the intercellular and pericellular matrix in normal and degenerate equine articular cartilage. The polarization sensitivity of SHG can be used directly to determine fiber orientation in the superficial 10 to 20 microm of tissue, and images of the ratio of intensities taken with two orthogonal polarization states reveal small scale variations in the collagen fiber organization that have not previously been reported. The signal from greater depths is influenced by the birefringence and biattenuance of the overlying tissue. An assessment of these effects is developed, based on the analysis of changes in TPF polarization with depth, and the approach is validated in tendon where composition is independent of depth. The analysis places an upper bound on the biattenuance of tendon of 2.65 x 10(-4). Normal cartilage reveals a consistent pattern of variation in fibril orientation with depth. In lesions, the pattern is severely disrupted and there are changes in the pericellular matrix, even at the periphery where the tissue appears microscopically normal. Quantification of polarization sensitivity changes with depth in cartilage will require detailed numerical models, but in the meantime, multiphoton microscopy provides sensitive indications of matrix changes in cartilage degeneration

Translating optical coherence tomography technologies from clinical studies to botany : real time imaging of long-distance signaling in plants

The time has now come to expand the use of optical coherence tomography and apply it in botany where the technology’s key advantages enable visualization of plant’s communication as it was never done before

Microbial Community Responses to Alterations in Historical Fire Regimes in Montane Grasslands

The influence of fire regimes on soil microbial diversity in montane grasslands is a relatively unexplored area of interest. Understanding the belowground diversity is a crucial stepping-stone toward unravelling community dynamics, nutrient sequestration, and overall ecosystem stability. In this study, metabarcoding was used to unravel the impact of fire disturbance regimes on bacterial and arbuscular mycorrhizal fungal community structures in South African montane grasslands that have been subjected to an intermediate (up to five years) term experimental fire-return interval gradient. Bacterial communities in this study exhibited a shift in composition in soils subjected to annual and biennial fires compared to the controls, with carbon and nitrogen identified as significant potential chemical drivers of bacterial communities. Shifts in relative abundances of dominant fungal operational taxonomic units were noted, with Glomeromycota as the dominant arbuscular mycorrhiza observed across the fire-return gradient. A reduction in mycorrhizal root colonisation was also observed in frequently burnt autumnal grassland plots in this study. Furthermore, evidence of significant mutualistic interactions between bacteria and fungi that may act as drivers of the observed community structure were detected. Through this pilot study, we can show that fire regime strongly impacts bacterial and fungal communities in southern African montane grasslands, and that changes to their usually resilient structure are mediated by seasonal burn patterns, chemical drivers, and mutualistic interactions between these two groups

Hyperspectral Imaging of the Hemodynamic and Metabolic States of the Exposed Cortex: Investigating a Commercial Snapshot Solution

Hyperspectral imaging (HSI) systems have the potential to retrieve in vivo hemodynamic and metabolic signals from the exposed cerebral cortex. The use of multiple narrow wavelength bands in the near infrared (NIR) range theoretically allows not only to image brain tissue oxygenation and hemodynamics via mapping of hemoglobin concentration changes, but also to directly quantify cerebral metabolism via measurement of the redox states of mitochondrial cytochrome-c-oxidase (CCO). The aim of this study is to assess the possibility of performing hyperspectral imaging of in vivo cerebral oxyhemoglobin (HbO2), deoxyhemoglobin (HHb) and oxidized CCO (oxCCO) using commercially available HSI devices. For this reason, a hyperspectral snapshot solution based on Cubert GmbH technology (S185 FireflEYE camera) has been tested on the exposed cortex of mice during normoxic, hypoxic and hyperoxic conditions. The system allows simultaneous acquisition of 138 wavelength bands between 450 and 998 nm, with spectral sampling and resolution of ~4 to 8 nm. From the hyperspectral data, relative changes in concentration of hemoglobin and oxCCO are estimated and hemodynamic and metabolic maps of the imaged cortex are calculated for two different NIR spectral ranges. Spectroscopic analysis at particular regions of interest is also performed, showing typical oxygen-dependent hemodynamic responses. The results highlight some of the potentials of the technology, but also the limitations of the tested commercial solution for such specific application, in particular regarding spatial resolution

In vivo measurement of skin surface strain and sub-surface layer deformation induced by natural tissue stretching.

Stratum corneum and epidermal layers change in terms of thickness and roughness with gender, age and anatomical site. Knowledge of the mechanical and tribological properties of skin associated with these structural changes are needed to aid in the design of exoskeletons, prostheses, orthotics, body mounted sensors used for kinematics measurements and in optimum use of wearable on-body devices. In this case study, optical coherence tomography (OCT) and digital image correlation (DIC) were combined to determine skin surface strain and sub-surface deformation behaviour of the volar forearm due to natural tissue stretching. The thickness of the epidermis together with geometry changes of the dermal-epidermal junction boundary were calculated during change in the arm angle, from flexion (90°) to full extension (180°). This posture change caused an increase in skin surface Lagrange strain, typically by 25% which induced considerable morphological changes in the upper skin layers evidenced by reduction of epidermal layer thickness (20%), flattening of the dermal-epidermal junction undulation (45-50% reduction of flatness being expressed as Ra and Rz roughness profile height change) and reduction of skin surface roughness Ra and Rz (40-50%). The newly developed method, DIC combined with OCT imaging, is a powerful, fast and non-invasive methodology to study structural skin changes in real time and the tissue response provoked by mechanical loading or stretching

Crafting place: Women’s everyday creativity in placemaking processes

Amid a resurgence of domestic craft, this article contends that everyday creative practices of women are part of placemaking processes in the creative city. Specifically, the research focuses on Liverpool in the Northwest of England, the so-called (and self-proclaimed) ‘centre of the creative universe’. This article utilized in-depth semi-structured interviews with members of knitting groups and the city centre Women’s Institute to explore how women use craft practice to create a sense of self and attachment to place. The idea of women gathering to craft is enduring, and is examined here to understand affective labour and the role that creativity plays in the urban experience of women. It is argued that the groups demonstrate a lack of engagement with the wider market and official placemaking processes, but instead demonstrate an element of self-valorization. The article challenges thinking around culture-led placemaking in cities like Liverpool, where discourses of creativity have been used as a driver for regeneration by shifting the emphasis onto seemingly banal settings on the edges of the so-called creative city. While urban placemakers have been more recently concerned with developing hubs of creative industries, the role of these groups that are not producing a profitable ‘product’ should not be underestimated or exploited