Modified lambert beer for bilirubin concentration and blood oxygen saturation prediction

Noninvasive measurement of health parameters such as blood oxygen saturation and bilirubin concentration predicted via an appropriate light reflectance model based on the measured optical signals is of eminent interest in biomedical research. This is to replace the use of conventional invasive blood sampling approach. This study aims to investigate the feasibility of using Modified Lambert Beer model (MLB) in the prediction of one’s bilirubin concentration and blood oxygen saturation value, SO2. This quantification technique is based on a priori knowledge of extinction coefficients of bilirubin and hemoglobin derivatives in the wavelength range of 440 – 500 nm. The validity of the prediction was evaluated using light reflectance data from TracePro raytracing software for a single-layered skin model with varying bilirubin concentration. The results revealed some promising trends in the estimated bilirubin concentration with mean ± standard deviation (SD) error of 0.255 ± 0.025 g/l. Meanwhile, a remarkable low mean ± SD error of 9.11 ± 2.48 % was found for the predicted SO2 value. It was concluded that these errors are likely due to the insufficiency of the MLB at describing changes in the light attenuation with the underlying light absorption processes. In addition, this study also suggested the use of a linear regression model deduced from this work for an improved prediction of the required health parameter values

Human retinal oximetry using hyperspectral imaging

The aim of the work reported in this thesis was to investigate the possibility of measuring human retinal oxygen saturation using hyperspectral imaging. A direct non-invasive quantitative mapping of retinal oxygen saturation is enabled by hyperspectral imaging whereby the absorption spectra of oxygenated and deoxygenated haemoglobin are recorded and analysed. Implementation of spectral retinal imaging thus requires ophthalmic instrumentation capable of efficiently recording the requisite spectral data cube. For this purpose, a spectral retinal imager was developed for the first time by integrating a liquid crystal tuneable filter into the illumination system of a conventional fundus camera to enable the recording of narrow-band spectral images in time sequence from 400nm to 700nm. Postprocessing algorithms were developed to enable accurate exploitation of spectral retinal images and overcome the confounding problems associated with this technique due to the erratic eye motion and illumination variation. Several algorithms were developed to provide semi-quantitative and quantitative oxygen saturation measurements. Accurate quantitative measurements necessitated an optical model of light propagation into the retina that takes into account the absorption and scattering of light by red blood cells. To validate the oxygen saturation measurements and algorithms, a model eye was constructed and measurements were compared with gold-standard measurements obtained by a Co-Oximeter. The accuracy of the oxygen saturation measurements was (3.31%± 2.19) for oxygenated blood samples. Clinical trials from healthy and diseased subjects were analysed and oxygen saturation measurements were compared to establish a merit of certain retinal diseases. Oxygen saturation measurements were in agreement with clinician expectations in both veins (48%±9) and arteries (96%±5). We also present in this thesis the development of novel clinical instrument based on IRIS to perform retinal oximetry.Al-baath University, Syri

Diffuse Reflectance Spectroscopy to Quantify In Vivo Tissue Optical Properties: Applications in Human Epithelium and Subcutaneous Murine Colon Cancer

Colorectal cancer is the 4th most common and 2nd deadliest cancer. Problems exist with predicting which patients will respond best to certain therapy regimens. Diffuse reflectance spectroscopy has been suggested as a candidate to optically monitor a patient’s early response to therapy and has been received favorably in experimentally managing other cancers such as breast and skin. In this dissertation, two diffuse reflectance spectroscopy probes were designed: one with a combined high-resolution microendoscopy modality, and one that was optimized for acquiring data from subcutaneous murine tumors. For both probes, percent errors for estimating tissue optical properties (reduced scattering coefficient and absorption coefficient) were less than 5% and 10%, respectively. Then, studies on tissue-simulating phantoms were performed to test probe sensitivity and to serve as testing platforms for investigators in biomedical optics. Next, the diffuse reflectance spectroscopy probe was applied to subcutaneous murine colon tumors (n=61) undergoing either antibody immunotherapy or standard 5-fluorouracil chemotherapy. Mice treated with a combination of these therapies showed reduced tumor growth compared to saline control, isotype control, immunotherapy, and chemotherapy groups (p\u3c0.001, \u3c0.001, \u3c0.001, and 0.046, respectively) 7 days post-treatment. Additionally, at 7 days post-treatment, oxyhemoglobin, a marker currently being explored as a functional prognostic cancer marker, trended to increase in immunotherapy, chemotherapy, and combination therapy groups compared to controls (p=0.315, 0.149, and 0.190). Also of interest, an oxyhemoglobin flare (averageincrease of 1.44x from baseline, p=0.03 compared to controls) was shown in tumors treated with chemotherapy, indicating that diffuse reflectance spectroscopy may be useful as a complimentary tool to monitor early tumor therapeutic response in colon cancer. However, subject-to-subject variability was high and studies correlating survival to early oxyhemoglobin flares are suggested

2D and 3D high-speed multispectral optical imaging systems for in-vivo biomedical research

Functional optical imaging encompasses the use of optical imaging techniques to study living biological systems in their native environments. Optical imaging techniques are well-suited for functional imaging because they are minimally-invasive, use non ionizing radiation, and derive contrast from a wide range of biological molecules. Modern transgenic labeling techniques, active and inactive exogenous agents, and intrinsic sources of contrast provide specific and dynamic markers of in-vivo processes at subcellular resolution. A central challenge in building functional optical imaging systems is to acquire data at high enough spatial and temporal resolutions to be able to resolve the in-vivo process(es) under study. This challenge is particularly highlighted within neuroscience where considerable effort in the field has focused on studying the structural and functional relationships within complete neurovascular units in the living brain. Many existing functional optical techniques are limited in meeting this challenge by their imaging geometries, light source(s), and/or hardware implementations. In this thesis we describe the design, construction, and application of novel 2D and 3D optical imaging systems to address this central challenge with a specific focus on functional neuroimaging applications. The 2D system is an ultra-fast, multispectral, wide-field imaging system capable of imaging 7.5 times faster than existing technologies. Its camera-first design allows for the fastest possible image acquisition rates because it is not limited by synchronization challenges that have hindered previous multispectral systems. We present the development of this system from a bench top instrument to a portable, low-cost, modular, open source, laptop based instrument. The constructed systems can acquire multispectral images at >75 frames per second with image resolutions up to 512 x 512 pixels. This increased speed means that spectral analysis more accurately reflects the instantaneous state of tissues and allows for significantly improved tracking of moving objects. We describe 3 quantitative applications of these systems to in-vivo research and clinical studies of cortical imaging and calcium signaling in stem cells. The design and source code of the portable system was released to the greater scientific community to help make high-speed, multispectral imaging more accessible to a larger number of dynamic imaging applications, and to foster further development of the software package. The second system we developed is an entirely new, high-speed, 3D fluorescence microscopy platform called Laser-Scanning Intersecting Plane Tomography (L-SIPT). L-SIPT uses a novel combination of light-sheet illumination and off-axis detection to provide en-face 3D imaging of samples. L-SIPT allows samples to move freely in their native environments, enabling a range of experiments not possible with previous 3D optical imaging techniques. The constructed system is capable of acquiring 3D images at rates >20 volumes per second (VPS) with volume resolutions of 1400 x 50 x 150 pixels, over a 200 fold increase over conventional laser scanning microscopes. Spatial resolution is set by choice of telescope design. We developed custom opto-mechanical components, computer raytracing models to guide system design and to characterize the technique's fundamental resolution limits, and phantoms and biological samples to refine the system's performance capabilities. We describe initial applications development of the system to image freely moving, transgenic Drosophila Melanogaster larvae, 3D calcium signaling and hemodynamics in transgenic and exogenously labeled rodent cortex in-vivo, and 3D calcium signaling in acute transgenic rodent cortical brain slices in-vitro

Guiding deep brain stimulation neurosurgery with optical spectroscopy

Savoir différiencier les différentes types de tissus représente un aspect important lors d’interventions médicales, que ce soit pour aider au diagnostic d’une maladie ou pour le guidage chirurgical. Il est généralement très difficile de distinguer les tissus sains des tissus pathologiques à l’oeil nu et la navigation chirurgicale peut parfois être difficile dans les grands organes où la structure ciblé se trouve enfouie profondément. De nouvelles méthodes susceptibles d’accroître la réussite de telles interventions médicales suscitent actuellement de l’intérêt chez les professionnels de la santé. La spectroscopie optique, en analysant les interactions lumière-tissu dans une plage spectrale définie, est un outil permettant de différencier les tissus avec une résolution et une sensibilité bien supérieures à celles de l’oeil humain. Tout au long de cette thèse, je détaillerai comment la spectroscopie optique a été utilisée pour créer et améliorer un système de guidage optique utilisé pour la stimulation cérébrale profonde en neurochirurgie, en particulier pour le traitement de la maladie de Parkinson. Pour commencer, je montrerai comment les informations spectroscopiques peuvent fournir une rétroaction peropératoire en temps réel à un neurochirurgien, au cours de la phase d’implantation de la procédure, avec une sonde qui n’induit aucune invasion supplémentaire. Je présenterai l’investigation de deux modalités spectroscopiques différentes pour la discrimination tissulaire pour le guidage, soit la spectroscopie à réflectance diffuse et la spectroscopie de diffusion Raman anti-Stokes cohérente. Les avantages et les inconvénients des deux techniques, ainsi que leurs aptitude à la traduction prometteuse pour cette application seront abordés. Par la suite, je présenterai une nouvelle technique d’analyse de données pour extraire l’oxygénation des tissus à partir de spectres de réflectance diffus dans le but d’améliorer la précision de mesure en spectroscopie rétinienne et ultimement de porter un diagnostique. Bien que conçu pour la rétine, l’algorithme peut également être utilisé pour analyser les spectres acquis lors d’une neurochirurgie afin de fournir des informations à la fois discriminantes et diagnostiques. Finalement, je montrerai des preuves de diffusion anisotrope de la lumière dans les axones myélinisés de la moelle épinière et discuterai des conséquences que cela pourrait avoir sur les simulations actuelles de la propagation des photons dans le cerveau, qui feront partie intégrante d’un guidage optique efficace.Differentiating tissue types is an important aspect of guiding medical interventions whether it be for disease diagnosis or for surgical guidance. However, diseased and healthy tissues are often hard to discriminate by human vision alone and surgical navigation can be difficult to accomplish in large organs where the target structure lies deep within the body. New methods that can increase certainty in such medical interventions are therefore of great interest to healthcare professionals. Optical spectroscopy is a tool which can be exploited to probe discriminatory information in tissue by analyzing light-tissue interactions with a spectral range, resolution and sensitivity much greater than the human eye. Throughout this thesis, I will explain how I have leveraged optical spectroscopy to create, and improve, an optical guidance system for deep brain stimulation neurosurgery, specifically for the treatment of Parkinson’s disease. I will begin by describing how spectroscopic information can provide real-time feedback to a surgeon during the procedure, in the hopes of ultimately improving treatment outcome. To this end, I will present the investigation of two different spectroscopic modalities for optical guidance: diffuse reflectance spectroscopy, and coherent anti-Stokes Raman scattering spectroscopy. The advantages and disadvantages of both techniques will be discussed along with their promising translatability for this application. Following this, I will present a novel data analysis technique for extracting the tissue oxygenation from diffuse reflectance spectra with the aim of improved diagnostic information in retinal spectroscopy. While designed for the retina, the algorithm can also be used to analyze spectra acquired during a neurosurgery to provide both discriminatory and diagnostic information. Lastly, I will show evidence of anisotropic light scattering in the myelinated axons of the spinal cord and discuss the implications this may have on current photon propagation simulations in the brain, which will be integral for effective optical guidance

Concentradores solares luminescentes de elevado desempenho para conversão fotovoltaica baseada em guias de onda flexíveis

The mismatch between the AM1.5G spectrum and photovoltaic cell absorption is one of the critical factors limiting their performance. To overcome it, several approaches have been proposed. Among them, emphasis is given to luminescent down-shifting layers, additive devices that are able to enhance performance under typical operation conditions, and to luminescent solar concentrators, a complementary technology to PV cells for use in urban environments. Luminescent down-shifting layers are coatings that are directly deposited on the surface of photovoltaic cells, and absorb the incident radiation that is not absorbed by photovoltaic cells, subsequently re-emitting it at a specific wavelength and refracting/reflecting it towards the photovoltaic cell. Luminescent solar concentrators are devices comprising a transparent matrix incorporating optically active centres that absorb the incident radiation, which is then re-emitted at a specific wavelength and transferred by total internal reflection to photovoltaic cells located at the edges of the matrix. This configuration enables photovoltaic devices to be embedded in building facades or windows, allowing them to be transformed into energy harvesting units, contributing for the development of zero-energy buildings. This thesis aimed to produce and characterize transparent organic- inorganic hybrids with controlled thickness and refractive index using poly(methyl methacrylate), di- and triureasils incorporating different lanthanide ions, namely Tb3+, Eu3+, Y b3+ and Nd3+, and the fol- lowing organic dyes: Rhodamine 6G and Rhodamine 800, silicon 2,3- naphthalocyaninebis(trihexylsilyloxide), chlorophyll and R- phycoerythrin molecules with emission tuned from the visible to NIR spectral regions. LSCs with planar and cylindrical geometry are studied. The use of the cylindrical geometry allows the effect of concentration to be higher when compared with the planar geometry, since the ratio between the exposed area and the area of the edges is increased. The cylindrical geometry concentrators are produced from plastic optical fibres with hollow cores, where the optically active layer was injected. The exposed area was further optimised through the production of bundles of LSCs, in which optical fibres with different cladding geometries were placed side by side. Finally, the attractive properties of natural-based dye molecules for the production of luminescent solar concentrators, which have been poorly explored, are also studied through the incorporation of chlorophyll and R- phycoerythrin as optically active centres. Key experimental results were also validated using Monte-Carlo ray-tracing simulations.O desfasamento entre o espetro AM1.5G e o espetro de absorção das células fotovoltaicas é um fator crítico que limita o desempenho das mesmas. De forma a ultrapassar isto, diversas aproximações têm sido propostas. Entre elas, têm sido enfatizadas as camadas luminescentes por desvio descendente de energia, dispositivos capazes de melhorar o desempenho em condições de operação específicas, e os concentradores solares luminescentes, considerados uma tecnologia complementar a das células fotovoltaicas para utilização em ambientes urbanos. As camadas luminescentes por desvio descendente de energia são revestimentos diretamente depositados no topo de células fotovoltaicas capazes de absorver a radiação incidente complementar à que as células fotovoltaicas absorvem e subsequentemente reemitem-na com um comprimento de onda específico que é refratado/refletido até à célula fotovoltaica. Os concentradores solares são dispositivos compostos por uma matriz transparente incorporando centros óticos ativos que absorbem a radiação incidente, que é posteriormente reemitida com um comprimento de onda específico e transportada por reflexão interna total até à célula fotovoltaica localizada nas extremidades da matriz. Esta configuração permite a produção de dispositivos fotovoltaicos embebidos em fachadas de edifícios e janelas, permitindo que estes sejam transformados em unidades de produção de energia, contribuindo para o desenvolvimento de edifícios de energia zero. O principal objetivo deste trabalho consiste no fabrico e caracterização de híbridos orgânicos-inorgânicos com espessura e índice de refração controlados utilizando polimetil-metacrilato, di- e tri-ureasil incorporando diferentes iões lantanídeos, nomeadamente Tb3+, Eu3+, Yb3+ and Nd3+, e corantes orgânicos como Rodamina 6G, Rodamina 800, Silício 2,3-naftalocianina bis(trietil siloxano), clorofila e R-ficoeritrina cuja emissão varia entre o visível e o infravermelho próximo. Concentradores solares luminescentes com geometria planares e cilíndrica foram estudados. A geometria cilíndrica permite que o efeito de concentração seja superior, quando comparado com a geometria planar, uma vez que a razão entre a área exposta e a área das extremidades aumenta. A geometria cilíndrica é explorada, através da produção de concentradores solares luminescentes em fibra ótica de plástico onde a camada ótica ativa se encontra no interior da fibra, como um preenchimento do núcleo oco. A possibilidade de aumentar a área exposta foi, também, abordada através do fabrico de uma matriz de concentradores solares luminescentes colocados lado a lado com diferentes geometrias da bainha. Para além disso, as propriedades óticas dos corantes orgânicos naturais, que têm sido pouco exploradas na literatura, foram alvo de estudo através da incorporação de moléculas de clorofila e de R-ficoeritrina como centros óticos em concentradores solares luminescentes. Os resultados experimentais mais relevantes foram validados através de simulações baseadas no método de Monte-Carlo.Programa Doutoral em Físic

OCM 2015 - 2nd International Conference on Optical Characterization of Materials: March 18th - 19th, 2015, Karlsruhe, Germany

Each material has its own specific spectral signature independent if it is food, plastics, or minerals. During the conference we will discuss new trends and developments in material characterization. You also will be informed about latest highlights to identify spectral footprints and their realizations in industry

Applications of artificial neural networks in three agro-environmental systems: microalgae production, nutritional characterization of soils and meteorological variables management

La agricultura es una actividad esencial para los humanos, es altamente dependiente de las condiciones meteorológicas y foco de investigación e innovación con el objetivo de enfrentar diversos desafíos. El cambio climático, calentamiento global y la degradación de los ecosistemas agrícolas son sólo algunos de los problemas que los humanos enfrentamos para continuar con la esencial producción de alimentos. Buscando la innovación en el sector agrícola, se consideraron tres tópicos principales de investigación para esta tesis; la producción de microalgas, el color del suelo y la fertilidad, y la adquisición de datos meteorológicos. Estos temas tienen roles cada vez más importantes en la agricultura, especialmente bajo la incertidumbre del futuro de la producción de alimentos. Las microalgas son una interesante alternativa para la fertilización de cultivos y la sostenibilidad del suelo; mientras que los parámetros de fertilidad del suelo necesitan ser más estudiados para desarrollar métodos de análisis de menor costo y más rápidos para ayudar al manejo. La agricultura, como actividad altamente dependiente del clima, necesita de datos meteorológicos para anticipar eventos, planificar y manejar los cultivos eficientemente. Estos temas se seleccionaron con el propósito de mejorar el estado actual de la técnica, proponer nuevas alternativas basadas, principalmente, en la aplicación de redes neuronales artificiales (ANN) como una manera novedosa de resolver los problemas y generar conocimiento de aplicación directa en sistemas de cultivos. El objetivo principal de esta tesis fue generar modelos de ANNs capaces de abordar problemas relacionados con la agricultura, como una alternativa a los métodos tradicionales y más costosos empleados en el manejo, análisis y adquisición de datos en los sistemas agrarios.Departamento de Ingeniería Agrícola y ForestalDoctorado en Ciencia e Ingeniería Agroalimentaria y de Biosistema

Aiding the conservation of two wooden Buddhist sculptures with 3D imaging and spectroscopic techniques

The conservation of Buddhist sculptures that were transferred to Europe at some point during their lifetime raises numerous questions: while these objects historically served a religious, devotional purpose, many of them currently belong to museums or private collections, where they are detached from their original context and often adapted to western taste. A scientific study was carried out to address questions from Museo d'Arte Orientale of Turin curators in terms of whether these artifacts might be forgeries or replicas, and how they may have transformed over time. Several analytical techniques were used for materials identification and to study the production technique, ultimately aiming to discriminate the original materials from those added within later interventions

Microplastics Degradation and Characterization

In the last decade, issues related to pollution from microplastics in all environmental compartments and the associated health and environmental risks have been the focus of intense social, media, and political attention worldwide. The assessment, quantification, and study of the degradation processes of plastic debris in the ecosystem and its interaction with biota have been and are still the focus of intense multidisciplinary research. Plastic particles in the range from 1 to 5 mm and those in the sub-micrometer range are commonly denoted as microplastics and nanoplastics, respectively. Microplastics (MPs) are being recognized as nearly ubiquitous pollutants in water bodies, but their actual concentration, distribution, and effects on natural waters, sediments, and biota are still largely unknown. Contamination by microplastics of agricultural soil and other environmental areas is also becoming a matter of concern. Sampling, separation, detection, characterization and evaluating the degradation pathways of micro- and nano-plastic pollutants dispersed in the environment is a challenging and critical goal to understand their distribution, fate, and the related hazards for ecosystems. Given the interest in this topic, this Special Issue, entitled “Microplastics Degradation and Characterization”, is concerned with the latest developments in the study of microplastics