1,720,961 research outputs found
Investigating biological optical transparency windows in the near and shortwave infrared for diagnosis and therapy
No full textOsteoarthritis (OA) is the most common degenerative joint disease and a leading cause of disability worldwide, presenting as the loss of the lubricating and shock absorbing layer of articular cartilage. This results in pain and loss of mobility, and in the absence of definitive cures requires early detection and intervention. Current clinical imaging paradigms fall short and rely on heuristic markers (pain, inflammation), ionising radiation (CT), and/or exogenous contrast (MRI). Radiologically presenting tissue changes are only indicative of advanced and irreversible degradation. Alternatively, vibrational spectroscopy utilising non-ionising near- and shortwave infrared (NIR, SWIR) light offers deep penetration into tissue and label free “chemical fingerprinting”. This utilises empirically derived “biological transparency windows” wherein NIR-SWIR light experiences reduced scattering and regions of reduced absorption. Raman scattering and absorption spectroscopy in this range offer potent tools for the detection of OA. Selectively targeting the absorption of certain NIR-SWIR chromophores can also allow for efficient and highly precise photoablation for therapeutic microsurgery applications. A novel approach for improved detection of OA in human femoral head cartilage by fusing Raman scattering and NIR-SWIR absorption spectral data, termed “spectromics”, is explored first. In this proof-of-concept, tissue was classified to high precision under multivariate statistical analysis (100 % class segregation) and supervised machine learning (80% OA, 95% control), where the enhanced spectromics fingerprint consistently outperformed Raman and NIR-SWIR alone. Clinically relevant tissue components were identified through discriminatory spectral features and proposed as OA spectromics biomarkers. A first demonstration of a novel 3D multimodal hyperspectral scanning system is presented next, with colocalised Raman and NIR-SWIR spectral measurements across the surface of human OA osteochondral samples. The system was proven suitable sensitive to OA associated spectral features and capable to map natural and pathological heterogeneities in 3D, proffered as a platform to further understand the complex effects of OA. Finally, an advance in NIR-SWIR mediated photoablation is presented demonstrating single-cell scale ablation of human cell samples on a microsurgery system enabled by a nano-second pulsed thulium-doped fibre laser. Precise control of pulse parameters achieved unprecedented precision of 31.3 ± 0.1 μm on onion epidermal and 19.9 ± 0.1 μm on SH-SY5Y cells with such a laser. The research presented in this thesis focuses on new methodologies for the diagnostic assessment and therapeutic treatment of tissues harnessing the NIR-SWIR optical regime, proposed for paradigm shift in current clinical practices. A general report for concept and delivery of public outreach and science communication activities during my candidature with the Molecular Biophotonics and Imaging group is also include
Harnessing Raman spectroscopy and multimodal imaging of cartilage for osteoarthritis diagnosis
No full textOsteoarthritis (OA) is a complex disease of cartilage characterised by joint pain, functional limitation, and reduced quality of life with affected joint movement leading to pain and limited mobility. Current methods to diagnose OA are predominantly limited to X-ray, MRI and invasive joint fluid analysis, all of which lack chemical or molecular specificity and are limited to detection of the disease at later stages. A rapid minimally invasive and non-destructive approach to disease diagnosis is a critical unmet need. Label-free techniques such as Raman Spectroscopy (RS), Coherent anti-Stokes Raman scattering (CARS), Second Harmonic Generation (SHG) and Two Photon Fluorescence (TPF) are increasingly being used to characterise cartilage tissue. However, current studies are based on whole tissue analysis and do not consider the different and structurally distinct layers in cartilage. In this work, we use Raman spectroscopy to obtain signatures from the superficial (top) and deep (bottom) layer of healthy and osteoarthritic cartilage samples from 64 patients (19 control and 45 OA). Spectra were acquired both in the ‘fingerprint’ region from 700 to 1720 cm− 1 and high-frequency stretching region from 2500 to 3300 cm− 1. Principal component and linear discriminant analysis was used to identify the peaks that contributed significantly to classification accuracy of the different samples. The most pronounced differences were observed at the proline (855 cm− 1 and 921 cm− 1) and hydroxyproline (877 cm− 1 and 938 cm− 1), sulphated glycosaminoglycan (sGAG) (1064 cm− 1 and 1380 cm− 1) frequencies for both control and OA as well as the 1245 cm− 1 and 1272 cm− 1, 1320 cm− 1 and 1345 cm− 1, 1451 cm− 1 collagen modes were altered in OA samples, consistent with expected collagen structural changes. Classification accuracy based on Raman fingerprint spectral analysis of superficial and deep layer cartilage for controls was found to be 97% and 93% on using individual/all spectra and, 100% and 95% on using mean spectra per patient, respectively. OA diseased cartilage was classified with an accuracy of 88% and 84% for individual/all spectra, and 96% and 95% for mean spectra per patient based on analysis of the superficial and the deep layers, respectively. Raman spectra from the C-H stretching region (2500–3300 cm− 1) resulted in high classification accuracy for identification of different layers and OA diseased cartilage but low accuracy for controls. Differential changes in superficial and deep layer cartilage signatures were observed with age (under 60 and over 60 years), in contrast, less significant differences were observed with gender. Prominent chemical changes in the different layers of cartilage were preliminarily imaged using CARS, SHG and TPF. Cell clustering was observed in OA together with differences in pericellular matrix and collagen structure in the superficial and the deep layers correlating with the Raman spectral analysis. The current study demonstrates the potential of Raman Spectroscopy and multimodal imaging to interrogate cartilage tissue and provides insight into the chemical and structural composition of its different layers with significant implications for OA diagnosis for an increasing aging demographic
Dataset for Doctoral Thesis "Investigating Biological Optical Transparency Windows in the Near and Shortwave Infrared for Diagnosis and Therapy"
No full textDataset for Doctoral Thesis, "Investigating Biological Optical Transparency Windows in the Near and Shortwave Infrared for Diagnosis and Therapy". Dataset is structured per results chapter (Chapters 5 - 7) including spectroscopic measurements and photo-ablation results.</span
Design and synthesis of quadrupolar A-D-A photon absorbing molecules: an investigation into their optical and bioimaging properties
No full textWe herein report on the design and synthesis and optical properties of 4 novel chromophores based on a quadrupole acceptor-donor-acceptor system. These quadrupoles were designed using a fluorene core, coupled to thienyl and thienyl acetylene bridges, to either two 3-dicycanovinylindan-1-ones or two 1,3-bis(dicyanomethylidene)-indanes as strong electron-withdrawing moieties. The structure-property relationships were investigated by computational modelling and photophysical studies, with the fluorophores giving red-emission with large Stokes shifts. The bridged alkynyl units, rather than enhancing conjugation, dramatically reduced fluorescence intensities and wavelength of emission. Notably, two-photon absorption studies revealed cross-section values of δ = 1720 and 780 GM for two of the fluorophores. The fluorophores were explored in one-photon and two-photon fluorescence biological imaging, including the staining of chick bones.</p
Holistic vibrational spectromics assessment of human cartilage for osteoarthritis diagnosis
Full text linkOsteoarthritis (OA) is the most common degenerative joint disease, presented as wearing down of articular cartilage and resulting in pain and limited mobility for 1 in 10 adults in the UK [Osteoarthr. Cartil. 28(6), 792 (2020) [CrossRef] ]. There is an unmet need for patient friendly paradigms for clinical assessment that do not use ionizing radiation (CT), exogenous contrast enhancing dyes (MRI), and biopsy. Hence, techniques that use non-destructive, near- and shortwave infrared light (NIR, SWIR) may be ideal for providing label-free, deep tissue interrogation. This study demonstrates multimodal “spectromics”, low-level abstraction data fusion of non-destructive NIR Raman scattering spectroscopy and NIR-SWIR absorption spectroscopy, providing an enhanced, interpretable “fingerprint” for diagnosis of OA in human cartilage. This is proposed as method level innovation applicable to both arthro- or endoscopic (minimally invasive) or potential exoscopic (non-invasive) optical approaches. Samples were excised from femoral heads post hip arthroplasty from OA patients (n = 13) and age-matched control (osteoporosis) patients (n = 14). Under multivariate statistical analysis and supervised machine learning, tissue was classified to high precision: 100% segregation of tissue classes (using 10 principal components), and a classification accuracy of 95% (control) and 80% (OA), using the combined vibrational data. There was a marked performance improvement (5 to 6-fold for multivariate analysis) using the spectromics fingerprint compared to results obtained from solely Raman or NIR-SWIR data. Furthermore, clinically relevant tissue components were identified through discriminatory spectral features – spectromics biomarkers – allowing interpretable feedback from the enhanced fingerprint. In summary, spectromics provides comprehensive information for early OA detection and disease stratification, imperative for effective intervention in treating the degenerative onset disease for an aging demographic. This novel and elegant approach for data fusion is compatible with various NIR-SWIR optical devices that will allow deep non-destructive penetration
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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