Browsing by Author "Meglinski, Igor"
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Item Open Access Characterization of Flow Dynamics in Vessels with Complex Geometry using Doppler Optical Coherence Tomography(Cranfield University, 2008-01) Bonesi, Marco; Meglinski, IgorThe study of flow dynamics in complex geometry vessels is highly important in many biomedical applications where the knowledge of the mechanic interactions between the moving fluid and the housing media plays a key role for the determination of the parameters of interest, including the effect of blood flow on the possible rupture of atherosclerotic plaques. Doppler Optical Coherence Tomography (DOCT) is an optic, non-contact, non-invasive technique able to achieve detailed analysis of the flow/vessel interactions, allowing simultaneously high resolution imaging of the morphology and composition of the vessel and of the flow velocity distribution along the measured cross-section. DOCT system was developed to image high-resolution one-dimensional and multi-dimensional velocity distribution profiles of Newtonian and non-Newtonian fluids flowing in vessels with complex geometry, including Y-shaped and T-shaped vessels, vessels with aneurism, bifurcated vessels with deployed stent and scaffolds. The phantoms were built to study the interaction of the flow dynamics with different channel geometries and to map the related velocity profiles at several inlet volume flow rates. Feasibility studies for quantitative observation of the turbulence of flows arising within the complex geometry vessels are discussed. In addition, optical clearing of skin tissues has been utilized to achieve DOCT imaging of human blood vessels in vivo, at a depth up to 1.7 mm. Two-dimensional OCT images of complex flow velocity profiles in blood vessel phantom and in vivo subcutaneous human skin tissues are presented. The effect of optical clearing on in vivo images is demonstrated and discussed. DOCT was also applied for imaging scaffold structures and for mapping flow distributions within the scaffold.Item Open Access Low coherenсe optiсal methods for express noninvasive bio-mediсal diagnostiсs(Cranfield University, 2010-01) Veksler, Boris; Meglinski, IgorСoherenсe is the fundamental property of optiсal radiation. Methods based on this сharaсteristiс are employed in different areas of researсh even in NASA and European spaсe agenсy. However, сoherenсe properties of light сan be suссessfully applied in life sсienсes for the purposes of diagnostiсs and treatment. The subjeсt of сurrent researсh is the development and improvement of the quantitative performanсe of non-invasive low сoherenсe optiсal diagnostiс whiсh is a novel modern biomediсal teсhnique uniquely suited for the measurements of partiсles distribution within the topiсal layers of biologiсal tissues and other сomplex media, suсh as polymers, сolloids, сomposite materials, etс. This approaсh is based on the illumination of a medium by optiсal radiation with a low сoherenсe both spatial and temporal, and analysis of the baсk-sсattering signal. Reсently introduсed this teсhnique is not сurrently used. The main diffiсulty in the developing of praсtiсal low-сoherenсe systems in biomediсal diagnostiсs is assoсiated with the сomplexity of biotissues struсture. For example, the human skin has very сomplex struсture and сonsists with several layers of cells with unique optiсal properties in eaсh layer. External boundary and internal boundaries between layers are rough and wavy. Thus, the most aссurate desсription of optiсal radiation propagation is extremely сompliсated to aсhieve and сan be performed only as a сomputer simulation. All further investigations of the optical methods of biotissues diagnostics can be enhanced using such computer models.Item Open Access New approach in multipurpose optical diagnostics: fluorescence based assay for simultaneous determination of physicochemical parameters(Cranfield University, 2009-09) Moczko, Ewa; Meglinski, Igor; Piletsky, Sergey A.The development of sensors assays for comprehensive characterisation of biological samples and effective minimal-invasive diagnostics is highly prioritised. Last decade this research area has been actively developing due to possibility of simultaneous, real- time, in vivo detection and monitoring of diverse physicochemical parameters and analytes. The new approach which has been introduced in this thesis was to develop and examine an optical diagnostic assay consisting of a mixture of environmental-sensitive fluorescent dyes. The operating principle of the system has been inspired by electronic nose and tongue devices which combine nonspecific (or semispecific) sensing elements and chemometric techniques for multivariate data analysis. The performance of the optical assay was based on the analysis of the spectrum of selected dyes with discreet reading of their emission maxima. The variations in peaks intensities caused by environmental changes provided distinctive fluorescence patterns, which could be handled similar to the signals collected from nose/tongue devices. The analytical capability of the assay was engendered by changes in fluorescence signal of the dye mixture in response to changes in pH, temperature, ionic strength and the presence of oxygen. Further findings have also proved the ability of optical assay to estimate development phases and to discriminate between different strains of growing cell cultures as well as identify various gastrointestinal diseases in human. This novel fluorescence-based diagnostic tool offers a promising alternative to electrochemical systems providing high sensitive measurements with broad dynamic range, easy, inexpensive measurements and the possibility of remote sensing and extreme assay miniaturisation. Additionally it does not require reference signal. This new approach can impact on a number of applications such as routine minimal- invasive diagnostics for medical samples, biomedical analysis, pharmaceutical or cosmetic research, quality control and process monitoring of food or environmental samples.Item Open Access Reconfigurable microfluidic platform in ice(Cranfield University, 2008-04) Varejka, M.; Piletsky, Sergey A.; Meglinski, Igor; Turner, Anthony P. F.Microfluidic devices are popular tools in the biotechnology industry where they provide smaller reagent requirements, high speed of analysis and the possibility for automation. The aim of the project is to make a flexible biocompatible microfluidic platform adapted to different specific applications, mainly analytical and separations which parameters and configuration can be changed multiple times by changing corresponding computer programme. The current project has been supported by Vice Chancellor Trans-Campus Iinitiative. Channels and various design geometries can easily and rapidly be marked on ice with a CO2 laser. Within seconds a microchannel pattern of features as small as 100 µm were obtained. The channels and design cavity dimensions are governed by the ratio of laser power by the beam velocity. The channels created in ice stay open for a duration which depend on their geometry and therefore on the ratio of the laser beam power by the beam velocity. Microchannels were created with a power/velocity ratio between 0.4 and 20 W/m. In this range of settings, the channels were 300 µm wide and stayed open for 2 s. After that they refreeze and the micropattern disappears in the ice bulk. Transport inside the channel can be obtained by the laser marking process alone. It is caused by the sheer surface tension within the melted area because of the temperature gradient within. The transport observed inside the channels was of the order of 1 mm/s in the laser experimental conditions (1.25 W and 100 mm/s). The temperature increase in the channel depends on the ratio of the laser power over velocity. High temperatures above 50°C can be achieved inside ice cavities. The ii experimental data were compared to theoretical values of the cavities dimensions and temperatures. A valve adapted for a microfluidic in ice functioning upon freezing/melting promoted by laser scanning was tested. The opening of the area depends only on the power and the speed of the laser while the closing time by freezing depends on the cooler devices set temperature. A laser-assisted zone melting technique for the preconcentration of analytes demonstrated on Meldola’s Blue as a model analyte was performed. A travelling melting zone of 1.5 mm x 1.5 mm was scanned at 6% power and 150 mm/sec with 25 scans over an area of 7.5 mm x 1.5 mm. An increase in concentration in end part of the melting zone was monitored after three successive travels. Channels created in conductive frozen solution can be conductive if linked to an electrical power supply. Electrophoresic transport and electroseparation of Rhodamine B and Bromocresol Green in ice capillaries were demonstrated for analytes separation with a power supply (electrical conditions 100 V, 0.1 mA and 3 W). The experimental results were in agreement with theoretical modelling and provide proof for the feasibility of the proposed concept of reconfigurable microfluidic device developed in ice and supported by scanning computer-controlled IR laser.Item Open Access Towards automated classification of clinical optimal coherence tomography (OCT) data obtained from dense tissues(Cranfield University, 2008) Bazant-Hegemark, Florian; Meglinski, Igor; Stone, NicholasCervical cancer can be prevented if its precursors are recognised. Those lesions that justify preventive treatment are currently identified using methods that suffer from delayed results, false positives and subjective judgement. Optical coherence tomography (OCT) is a novel imaging modality that provides high-resolution backscattering data similar to ultrasonography. It could potentially provide in vivo and real-time imaging from within the entire cervical epithelium, where cervical cancer predominantly develops. In this study, we used a bench top OCT system with a 1310 nm light source. It employs fibre optics and operates in the time domain. A collection of 1387 images from 212 ex vivo tissue samples from 199 participants requiring a histopathologic examination of the cervix has been created. Images from this collection were assessed in respect to their benefit in providing markets or evidence of early developments representative of cervical cancer. In our images, the contrast in dense tissue is weak and specific markers that could be associated with a higher cancer risk were difficult to establish. For two reasons it was decided to use an algorithm for classifying the images: 1) Modern OCT systems acquire gigabytes of data per second which cannot be assessed in a clinically meaningful time. 2) An unsupervised classification tool can provide an objective assessment. There is no established method for evaluating OCT images of dense tissue. A classification algorithm was designed that uses Principal Components Analysis as means of data reduction and Linear Discriminant Analysis as a classification tool. This approach does not rely on clinical markets to be designated a priori. The algorithm was applied to the clinical data set to separate samples with mild from severe risk of cancer progression. The performance after leave-one-patient-out cross-validation reaches 61.5% (sensitivity = 66.7%, specificity = 47.3%, kappa = 0.52). These results are not convincing enough to let OCT replace current systems as clinical tools in cervical precancer assessment. Routes for improving results are suggested. This thesis provides a novel, generic algorithm for rapidly classifying OCT data obtained from dense tissues.