Дисертації з теми "Inverse Problems in Imaging"
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Leung, Wun Ying Valerie. "Inverse problems in astronomical and general imaging." Thesis, University of Canterbury. Electrical and Computer Engineering, 2002. http://hdl.handle.net/10092/7513.
Повний текст джерелаSzasz, Teodora. "Advanced beamforming techniques in ultrasound imaging and the associated inverse problems." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30221/document.
Повний текст джерелаUltrasound (US) allows non-invasive and ultra-high frame rate imaging procedures at reduced costs. Cardiac, abdominal, fetal, and breast imaging are some of the applications where it is extensively used as diagnostic tool. In a classical US scanning process, short acoustic pulses are transmitted through the region-of-interest of the human body. The backscattered echo signals are then beamformed for creating radiofrequency(RF) lines. Beamforming (BF) plays a key role in US image formation, influencing the resolution and the contrast of final image. The objective of this thesis is to model BF as an inverse problem, relating the raw channel data to the signals to be recovered. The proposed BF framework improves the contrast and the spatial resolution of the US images, compared with the existing BF methods. To begin with, we investigated the existing BF methods in medical US imaging. We briefly review the most common BF techniques, starting with the standard delay-and-sum BF method and emerging to the most known adaptive BF techniques, such as minimum variance BF. Afterwards, we investigated the use of sparse priors in creating original two-dimensional beamforming methods for ultrasound imaging. The proposed approaches detect the strong reflectors from the scanned medium based on the well-known Bayesian Information Criteria used in statistical modeling. Furthermore, we propose a new way of addressing the BF in US imaging, by formulating it as a linear inverse problem relating the reflected echoes to the signal to be recovered. Our approach offers flexibility in the choice of statistical assumptions on the signal to be beamformed and it is robust to a reduced number of pulse emissions. At the end of this research, we investigated the use of the non-Gaussianity properties of the RF signals in the BF process, by assuming alpha-stable statistics of US images
Gregson, James. "Applications of inverse problems in fluids and imaging." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54081.
Повний текст джерелаScience, Faculty of
Computer Science, Department of
Graduate
Lecharlier, Loïc. "Blind inverse imaging with positivity constraints." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209240.
Повний текст джерелаDoctorat en Sciences
info:eu-repo/semantics/nonPublished
Zhang, Wenlong. "Forward and Inverse Problems Under Uncertainty." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE024/document.
Повний текст джерелаThis thesis contains two different subjects. In first part, two cases are considered. One is the thin plate spline smoother model and the other one is the elliptic boundary equations with uncertain boundary data. In this part, stochastic convergences of the finite element methods are proved for each problem.In second part, we provide a mathematical analysis of the linearized inverse problem in multifrequency electrical impedance tomography. We present a mathematical and numerical framework for a procedure of imaging anisotropic electrical conductivity tensor using a novel technique called Diffusion Tensor Magneto-acoustography and propose an optimal control approach for reconstructing the cross-property factor relating the diffusion tensor to the anisotropic electrical conductivity tensor. We prove convergence and Lipschitz type stability of the algorithm and present numerical examples to illustrate its accuracy. The cell model for Electropermeabilization is demonstrated. We study effective parameters in a homogenization model. We demonstrate numerically the sensitivity of these effective parameters to critical microscopic parameters governing electropermeabilization
Zhu, Sha. "A Bayesian Approach for Inverse Problems in Synthetic Aperture Radar Imaging." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00844748.
Повний текст джерелаAlfowzan, Mohammed Fowzan, and Mohammed Fowzan Alfowzan. "Solutions to Space-Time Inverse Problems." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621791.
Повний текст джерелаRückert, Nadja. "Studies on two specific inverse problems from imaging and finance." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-91587.
Повний текст джерелаSom, Subhojit. "Topics in Sparse Inverse Problems and Electron Paramagnetic Resonance Imaging." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282135281.
Повний текст джерелаZamanian, Sam Ahmad. "Hierarchical Bayesian approaches to seismic imaging and other geophysical inverse problems." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92970.
Повний текст джерелаThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 189-196).
In many geophysical inverse problems, smoothness assumptions on the underlying geologic model are utilized to mitigate the effects of poor data coverage and observational noise and to improve the quality of the inferred model parameters. In the context of Bayesian inference, these smoothness assumptions take the form of a prior distribution on the model parameters. Conventionally, the regularization parameters defining these assumptions are fixed independently from the data or tuned in an ad hoc manner. However, it is often the case that the smoothness properties of the true earth model are not known a priori, and furthermore, these properties may vary spatially. In the seismic imaging problem, for example, where the objective is to estimate the earth's reflectivity, the reflectivity model is smooth along a particular reflector but exhibits a sharp contrast in the direction orthogonal to the reflector. In such cases, defining a prior using predefined smoothness assumptions may result in posterior estimates of the model that incorrectly smooth out these sharp contrasts. In this thesis, we explore the application of Bayesian inference to different geophysical inverse problems and seek to address issues related to smoothing by appealing to the hierarchical Bayesian framework. We capture the smoothness properties of the prior distribution on the model by defining a Markov random field (MRF) on the set of model parameters and assigning weights to the edges of the underlying graph; we refer to these parameters as the edge strengths of the MRF. We investigate two cases where the smoothing is specified a priori and introduce a method for estimating the edge strengths of the MRF. In the first part of this thesis, we apply a Bayesian inference framework (where the edge strengths of the MRF are predetermined) to the problem of characterizing the fractured nature of a reservoir from seismic data. Our methodology combines different features of the seismic data, particularly P-wave reflection amplitudes and scattering attributes, to allow for estimation of fracture properties under a larger physical regime than would be attainable using only one of these data types. Through this application, we demonstrate the capability of our parameterization of the prior distribution with edge strengths to both enforce smoothness in the estimates of the fracture properties and capture a priori information about geological features in the model (such as a discontinuity that may arise in the presence of a fault). We solve the inference problem via loopy belief propagation to approximate the posterior marginal distributions of the fracture properties, as well as their maximum a posteriori (MAP) and Bayes least squares estimates. In the second part of the thesis, we investigate how the parameters defining the prior distribution are connected to the model covariance and address the question of how to optimize these parameters in the context of the seismic imaging problem. We formulate the seismic imaging problem within the hierarchical Bayesian setting, where the edge strengths are treated as random variables to be inferred from the data, and provide a framework for computing the marginal MAP estimate of the edge strengths by application of the expectation-maximization (E-M) algorithm. We validate our methodology on synthetic datasets arising from 2-D models. The images we obtain after inferring the edge strengths exhibit the desired spatially-varying smoothness properties and yield sharper, more coherent reflectors. In the final part of the thesis, we shift our focus and consider the problem of timelapse seismic processing, where the objective is to detect changes in the subsurface over a period of time using repeated seismic surveys. We focus on the realistic case where the surveys are taken with differing acquisition geometries. In such situations, conventional methods for processing time-lapse data involve inverting surveys separately and subtracting the inversion models to estimate the change in model parameters; however, such methods often perform poorly as they do not correctly account for differing model uncertainty between surveys due to differences in illumination and observational noise. Applying the machinery explored in the previous chapters, we formulate the time-lapse processing problem within the hierarchical Bayesian setting and present a framework for computing the marginal MAP estimate of the time-lapse change model using the E-M algorithm. The results of our inference framework are validated on synthetic data from a 2-D time-lapse seismic imaging example, where the hierarchical Bayesian estimates significantly outperform conventional time-lapse inversion results.
by Sam Ahmad Zamanian.
Ph. D.
Bhandari, Ayush. "Inverse problems in time-of-flight imaging : theory, algorithms and applications." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/95867.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 100-108).
Time-of-Fight (ToF) cameras utilize a combination of phase and amplitude information to return real-time, three dimensional information of a scene in form of depth images. Such cameras have a number of scientific and consumer oriented applications. In this work, we formalize a mathematical framework that leads to unifying perspective on tackling inverse problems that arise in the ToF imaging context. Starting from first principles, we discuss the implications of time and frequency domain sensing of a scene. From a linear systems perspective, this amounts to an operator sampling problem where the operator depends on the physical parameters of a scene or the bio-sample being investigated. Having presented some examples of inverse problems, we discuss detailed solutions that benefit from scene based priors such sparsity and rank constraints. Our theory is corroborated by experiments performed using ToF/Kinect cameras. Applications of this work include multi-bounce light decomposition, ultrafast imaging and fluorophore lifetime estimation.
by Ayush Bhandari.
S.M.
Yin, Ke. "New algorithms for solving inverse source problems in imaging techniques with applications in fluorescence tomography." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48945.
Повний текст джерелаJavanmard, Mehdi. "Inverse problem approach to ultrasound medical imaging." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/NQ31933.pdf.
Повний текст джерелаWintz, Timothée. "Super-resolution in wave imaging." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE052/document.
Повний текст джерелаDifferent modalities in wave imaging each present limitations in terms of resolution or contrast. In this work, we present a mathematical model of the ultrafast ultrasound imaging modality and reconstruction methods which can improve contrast and resolution in ultrasonic imaging. We introduce two methods which allow to improve contrast and to locate blood vessels belowthe diffraction limit while simultaneously estimating the blood velocity. We also present a reconstruction method in electrical impedance tomography which allows reconstruction of microscopic parameters from multi-frequency measurements using the theory of homogenization
Li, Xiaobei. "Instrumentation and inverse problem solving for impedance imaging /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/5973.
Повний текст джерелаHugelier, Siewert. "Approaches to inverse problems in chemical imaging : applications in super-resolution and spectral unmixing." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10144/document.
Повний текст джерелаBesides the chemical information, chemical imaging also offers insights in the spatial distribution of the samples. Within this thesis, we distinguish between two different types of images: spatial-temporal images (super-resolution fluorescence microscopy) and spatial-spectral images (unmixing). In early super-resolution fluorescence microscopy, a low number of fluorophores were active per image. Currently, the field evolves towards high-density imaging that requires new ways of analysis. We propose SPIDER, an image deconvolution approach with multiple penalties. These penalties directly translate the properties of the blinking emitters used in super-resolution fluorescence microscopy imaging. SPIDER allows investigating highly dynamic structural and morphological changes in biological samples with a high fluorophore density. We applied the method on live-cell imaging of a HEK-293T cell labeled with DAKAP-Dronpa and demonstrated a spatial resolution down to 55 nm and a time sampling of 0.5 s. Unmixing hyperspectral images with MCR-ALS provides spatial and spectral information of the individual contributions in the mixture. Due to loss of the pixel neighborhood during the unfolding of the hyperspectral data cube to a two-way matrix, spatial information cannot be added as a constraint during the analysis We therefore propose an alternative approach in which an additional refolding/unfolding step is performed in each iteration. This data manipulation allows global spatial features to be added to the palette of MCR-ALS constraints. From this idea, we also developed several constraints and show their application on experimental data
Wei, Hsin-Yu. "Magnetic induction tomography for medical and industrial imaging : hardware and software development." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558901.
Повний текст джерелаGUASTAVINO, SABRINA. "Learning and inverse problems: from theory to solar physics applications." Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/998315.
Повний текст джерелаBurvall, Anna. "Axicon imaging by scalar diffraction theory." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3736.
Повний текст джерелаAxicons are optical elements that produce Bessel beams,i.e., long and narrow focal lines along the optical axis. Thenarrow focus makes them useful ine.g. alignment, harmonicgeneration, and atom trapping, and they are also used toincrease the longitudinal range of applications such astriangulation, light sectioning, and optical coherencetomography. In this thesis, axicons are designed andcharacterized for different kinds of illumination, using thestationary-phase and the communication-modes methods.
The inverse problem of axicon design for partially coherentlight is addressed. A design relation, applicable toSchell-model sources, is derived from the Fresnel diffractionintegral, simplified by the method of stationary phase. Thisapproach both clarifies the old design method for coherentlight, which was derived using energy conservation in raybundles, and extends it to the domain of partial coherence. Thedesign rule applies to light from such multimode emitters aslight-emitting diodes, excimer lasers and some laser diodes,which can be represented as Gaussian Schell-model sources.
Characterization of axicons in coherent, obliqueillumination is performed using the method of stationary phase.It is shown that in inclined illumination the focal shapechanges from the narrow Bessel distribution to a broadasteroid-shaped focus. It is proven that an axicon ofelliptical shape will compensate for this deformation. Theseresults, which are all confirmed both numerically andexperimentally, open possibilities for using axicons inscanning optical systems to increase resolution and depthrange.
Axicons are normally manufactured as refractive cones or ascircular diffractive gratings. They can also be constructedfrom ordinary spherical surfaces, using the sphericalaberration to create the long focal line. In this dissertation,a simple lens axicon consisting of a cemented doublet isdesigned, manufactured, and tested. The advantage of the lensaxicon is that it is easily manufactured.
The longitudinal resolution of the axicon varies. The methodof communication modes, earlier used for analysis ofinformation content for e.g. line or square apertures, isapplied to the axicon geometry and yields an expression for thelongitudinal resolution. The method, which is based on abi-orthogonal expansion of the Green function in the Fresneldiffraction integral, also gives the number of degrees offreedom, or the number of information channels available, forthe axicon geometry.
Keywords:axicons, diffractive optics, coherence,asymptotic methods, communication modes, information content,inverse problems
Camargo, Erick Darío León Bueno de. "Desenvolvimento de algoritmo de imagens absolutas de tomografia por impedância elétrica para uso clínico." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-26062014-205827/.
Повний текст джерелаElectrical Impedance Tomography is a non invasive imaging technique that can be used in clinical applications to infer living tissue impeditivity from boundary electrical measurements. Mathematically this is an non-linear ill-posed inverse problem. Usually a spatial high-pass Gaussian filter is used as a regularization method for solving the inverse problem. The main objective of this work is to propose the use of physiological and anatomical priors of tissue resistivity distribution within the thorax, also known as anatomical atlas, in conjunction with the Gaussian filter as regularization methods. The proposed methodology employs the finite element method and the Gauss-Newton algorithm in order to reconstruct three-dimensional resistivity images. The Approximation Error Theory is used to reduce discretization effects and mesh size errors. Electrical impedance tomography data and computed tomography images of physiological pulmonary changes collected in vivo in a swine were used to validate the proposed method. The images obtained are compatible with atelectasis, pneumothorax, pleural effusion and different ventilation pressures during mechanical ventilation. The results show that image reconstruction from swines with clinically significant information is feasible when both the Gaussian filter and the anatomical atlas are used as regularization methods.
Alberti, Giovanni S. "On local constraints and regularity of PDE in electromagnetics : applications to hybrid imaging inverse problems." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:1b30b3b7-29b1-410d-ae30-bd0a87c9720b.
Повний текст джерелаCao, Xiande. "Volume and Surface Integral Equations for Solving Forward and Inverse Scattering Problems." UKnowledge, 2014. http://uknowledge.uky.edu/ece_etds/65.
Повний текст джерелаKim, Yong Yook. "Inverse Problems In Structural Damage Identification, Structural Optimization, And Optical Medical Imaging Using Artificial Neural Networks." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11111.
Повний текст джерелаPh. D.
Nicu, Ana-Maria. "Approximation and representation of functions on the sphere : applications to inverse problems in geodesy and medical imaging." Nice, 2012. http://www.theses.fr/2012NICE4007.
Повний текст джерелаThis work concerns the representation and approximation of functions on a sphere with applications to source localization inverse problems in geodesy and medical imaging. The thesis is structured in 6 chapters as follow : Chapter 1 presents an introduction to the geodesy and M/EGG inverse problems. The inverse problem (IP) consists in recovering a density inside the ball (Earth, human brain) from partially known data on the surface. Chapter 2 gives the mathematical background used along the thesis. The resolution of the inverse problem (IP) involves the resolution of two steps : the transmission data problem (TP) and the density recovery (DR) problem. In practice, the data are only available on some region of the sphere, as a spherical cap, like the north hemisphere of the head (M/EGG) or continent (geodesy). For this purpose, in chapter 3, we give an efficient method to build the appropriate Slepian basis on which we express the data. This is set up by using Gauss-Legendre quadrature. The transmission data problem (chapter 4) consists in estimating the data (spherical harmonic expansion) over the whose sphere from noisy measurements expressed in Slepian basis. The second step, density recovery (DR) problem, is detailed in chapter 5 where we study three density models (monopolar, dipolar and inclusions). For the resolution of (DR), we use a best quadratic rational approximation method on planar sections. We give also some properties of the density and the operator which links it to the generated potential. In chapter 6, we study the chapter 3, 4 and 5 from numerical point of view. We present some numerical tests to illustrate source localization results for geodesy and M/EGG problems when we dispose of partial data on the sphere
Hart, Vern Philip II. "The Application of Tomographic Reconstruction Techniques to Ill-Conditioned Inverse Problems in Atmospheric Science and Biomedical Imaging." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1354.
Повний текст джерелаDupuy, Clément. "Reconstruction d'image pour l'acousto-optique vers une imagerie quantitative." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET034.
Повний текст джерелаThe optical properties of biological tissues are of significant clinical interest. Such media are highly scattering to the near-infrared light which offers the required contrast, and consequently purely optical approaches to imaging tissues at depth suffer from limited spatial resolution. Acousto-optic imaging is a multi-modal technique which overcomes this problem by combining the optical contrast of near infra-red light with the spatial resolution of ultrasound, permitting millimetre resolution at depths of several centimetres. Raw measurements made using the acousto-optic technique are corrupted by the varying optical fluence in the medium. By using inverse problem base reconstructions algorithms, it is possible to reconstruct a map of the absorption coefficient inside the medium. My PhD is conducted between Institut Langevin, in Paris, where my acousto- optics imaging setup is and the Medical Physics and Bioengineering lab in UCL, in London where I work on the reconstruction algorithms in order to achieve quantitative measurement
Travis, Clive Hathaway. "The inverse problem and applications to optical and eddy current imaging." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/804869/.
Повний текст джерелаVeras, Johann. "Electrical Conductivity Imaging via Boundary Value Problems for the 1-Laplacian." Doctoral diss., University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6377.
Повний текст джерелаPh.D.
Doctorate
Mathematics
Sciences
Mathematics
Paleo, Pierre. "Méthodes itératives pour la reconstruction tomographique régularisée." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT070/document.
Повний текст джерелаIn the last years, there have been a diversification of the tomography imaging technique for many applications. However, experimental constraints often lead to limited data - for example fast scans, or medical imaging where the radiation dose is a primary concern. The data limitation may come as a low signal to noise ratio, scarce views or a missing angle wedge.On the other hand, artefacts are detrimental to reconstruction quality.In these contexts, the standard techniques show their limitations.In this work, we explore how regularized tomographic reconstruction methods can handle these challenges.These methods treat the problem as an inverse problem, and the solution is generally found by the means of an optimization procedure.Implementing regularized reconstruction methods entails to both designing an appropriate regularization, and choosing the best optimization algorithm for the resulting problem.On the modelling part, we focus on three types of regularizers in an unified mathematical framework, along with their efficient implementation: Total Variation, Wavelets and dictionary-based reconstruction. On the algorithmic part, we study which state-of-the-art convex optimization algorithms are best fitted for the problem and parallel architectures (GPU), and propose a new algorithm for an increased convergence speed.We then show how the standard regularization models can be extended to take the usual artefacts into account, namely rings and local tomography artefacts. Notably, a novel quasi-exact local tomography reconstruction method is proposed
Pereira, Antonio. "Acoustic imaging in enclosed spaces." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0066/document.
Повний текст джерелаThis thesis is concerned with the problem of noise source identification in closed spaces. The main motivation was to propose a technique which allows to locate and quantify noise sources within industrial vehicles, in a time-effective manner. In turn, the technique might be used by manufacturers for noise abatement purposes such as to provide quieter vehicles. A simplified model based on the equivalent source formulation was used to tackle the problem. It was shown that the problem is ill-conditioned, in the sense that it is very sensitive to errors in measurement data, thus regularization techniques were required. A detailed study of this issue, in particular the tuning of the so-called regularization parameter, was of importance to ensure the stability of the solution. In particular, a Bayesian regularization criterion was shown to be a very robust approach to optimally adjust the regularization parameter in an automated way. The target application concerns very large interior environments, which imposes additional difficulties, namely: (a) the positioning of the measurement array inside the enclosure; (b) a number of unknowns ("candidate" sources) much larger than the number of measurement positions. An iterative weighted formulation was then proposed to overcome the above issues by: first correct for the positioning of the array within the enclosure and second iteratively solve the problem in order to obtain a correct source quantification. In addition, the iterative approach has provided results with an enhanced spatial resolution and dynamic range. Several numerical studies have been carried out to validate the method as well as to evaluate its sensitivity to modeling errors. In particular, it was shown that the approach is affected by non-anechoic conditions, in the sense that reflections are identified as "real" sources. A post-processing technique which helps to distinguish between direct and reverberant paths has been discussed. The last part of the thesis was concerned with experimental validations and practical applications of the method. A custom spherical array consisting of a rigid sphere and 31 microphones has been built for the experimental tests. Several academic experimental validations have been carried out in semi-anechoic environments, which illustrated the advantages and limits of the method. Finally, the approach was tested in a practical application, which consisted in identifying noise sources inside a bus at driving conditions
Lu, Wei. "Hough transforms for shape identification and applications im medical image processing /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115568.
Повний текст джерелаFromenteze, Thomas. "Développement d'une technique de compression passive appliquée à l'imagerie microonde." Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0061/document.
Повний текст джерелаThis work is focused on the development of a compressive technique applied to the simplification of microwave imaging systems. This principle is based on the study of passive devices able to compress transmitted and received waves, allowing for the reduction of the hardware complexity required by radar systems. This approach exploits the modal diversity in the developed components, making it compatible with ultra wide bandwidth. Several proofs of concept are presented using different passive devices, allowing this technique to be adapted to a large variety of architectures and bandwidths
Zeitler, Armin. "Investigation of mm-wave imaging and radar systems." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00832647.
Повний текст джерелаGuerrero, prado Patricio. "Reconstruction tridimensionnelle des objets plats du patrimoine à partir du signal de diffusion inélastique." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV035/document.
Повний текст джерелаThree-dimensional characterization of flat ancient material objects has remained a challenging activity to accomplish by conventional X-ray tomography methods due to their anisotropic morphology and flattened geometry.To overcome the limitations of such methodologies, an imaging modality based on Compton scattering is studied in this work. Classical X-ray tomography treats Compton scattering data as noise in the image formation process, while in Compton scattering tomography the conditions are set such that Compton data become the principal image contrasting agent. Under these conditions, we are able to avoid relative rotations between the sample and the imaging setup. Mathematically this problem is addressed by means of the conical Radon transform. A model of the direct problem is presented where the output of the system is the spectral image obtained from an input object. The inverse problem is addressed to estimate the 3D distribution of the electronic density of the input object from the spectral image. The feasibility of this methodology is supported by numerical simulations
Rückert, Nadja [Verfasser], Bernd [Akademischer Betreuer] Hofmann, Bernd [Gutachter] Hofmann, and Christine [Gutachter] Böckmann. "Studies on two specific inverse problems from imaging and finance / Nadja Rückert ; Gutachter: Bernd Hofmann, Christine Böckmann ; Betreuer: Bernd Hofmann." Chemnitz : Universitätsbibliothek Chemnitz, 2012. http://d-nb.info/1214244068/34.
Повний текст джерелаSambolian, Serge. "Tomographie des pentes à cohérence cinématique fondée sur des solveurs eikonals et la méthode de l’état adjoint : Théorie et applications à la construction de modèles de vitesses et localisation d'événements." Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4002.
Повний текст джерелаVelocity model building is a key step of seismic imaging since inferring high-resolution subsurface model by migration or full waveform inversion (FWI) is highly dependent on the kinematic accuracy of the retrieved velocity model. Stereotomography, a slope tomographic method that exploits well the density of the data, was proposed as an alternative to conventional reflection traveltime tomography. The latter is based on interpretive tracking of laterally-continuous reflections in the data volume whereas stereotomography relies on automated picking of locally coherent events. The densely picked attributes, namely the traveltimes and their spatial derivatives with respect to the source and receiver positions, are tied to scatterers in depth. More recently, a slope tomography variant was proposed under a framework based on eikonal solvers as an alternative to ray tracing and the adjoint-state method instead of Fréchet-derivative matrix inversion. This revamped stereotomography provides a scalable and flexible framework for large-scale applications. On the other hand, similarly to previous works, the scatterer positions and the subsurface parameters are updated jointly. In this thesis, I propose a new formulation of slope tomography that handles more effectively the ill-famed velocity-position coupling inherently present in reflection tomography. Through a kinematic migration, the scatterer position sub-problem is solved and projected into the main sub-problem for wavespeed estimation. Enforcing the kinematic consistency between the two kinds of variable, that is not guaranteed in the joint inversion, mitigates the ill-posedness generated by the velocity-position coupling. This variable projection leads to a reduced-parametrization inversion where the residuals of a single data class being a slope are minimized to update the subsurface parameters.I introduce this parsimonious strategy in the framework of eikonal solvers and the adjoint-state method for tilted transversely isotropic (TTI) media. I benchmark the method against the Marmousi model and present a field data case study previously tackled with the joint inversion strategy. Both case studies confirm that the parsimonious approach leads to a better-posed problem, with an improved robustness to the initial guess and convergence speed.Slope tomography is mainly used for streamer data due to the requirement of finely-sampled sources and receivers. To exploit cutting-edge long-offset datasets, I involve in the inversion first arrivals extracted from streamer or ocean bottom seismometer data. Before showing the complementarity between reflections and first arrivals, I examine the added value of introducing slopes in first-arrival traveltime tomography (FATT). Using a FWI workflow for quality control, I show with the Overthrust benchmark and a real data case study from the Nankai trough (Japan) how the joint inversion of slopes and traveltimes mitigates the ill-posedness of FATT. I also examine with the BP Salt model the limits of FATT to build an initial model for FWI in complex media. The results show how tomography suffers even with proper undershooting of the imaging targets due to the poor illumination of the subsalt area. On a crustal-scale benchmark, I first show the limits of reflection slope tomography induced by the limited streamer length before highlighting the added-value of the joint inversion of first-arrival and reflection picks.Finally, I introduce the same variable projection technique to tackle the velocity-hypocenter problem, which finds application in earthquake seismology and microseismic imaging. I propose a formulation where the hypocenter is located through the inversion of subsurface parameters and an origin time correction, both of them being used as a proxy and validate the proof of concept on two synthetic examples
Henriksson, Tommy. "CONTRIBUTION TO QUANTITATIVE MICROWAVE IMAGING TECHNIQUES FOR BIOMEDICAL APPLICATIONS." Doctoral thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-5882.
Повний текст джерелаA dissertation prepared through an international convention for a joint supervision thesis with Université Paris-SUD 11, France
Microwaves in biomedicine
Moffitt, Michael Adam. "Functional Imaging of the Mammalian Spinal Cord." Case Western Reserve University School of Graduate Studies / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1081363883.
Повний текст джерелаGunnarsson, Tommy. "MICROWAVE IMAGING OF BIOLOGICAL TISSUES: applied toward breast tumor detection." Licentiate thesis, Västerås : Department of Computer Science and Electronics, Mälardalen University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-204.
Повний текст джерелаWörmann, Julian [Verfasser], Martin [Akademischer Betreuer] Kleinsteuber, Martin [Gutachter] Kleinsteuber, and Walter [Gutachter] Stechele. "Structured Co-sparse Analysis Operator Learning for Inverse Problems in Imaging / Julian Wörmann ; Gutachter: Martin Kleinsteuber, Walter Stechele ; Betreuer: Martin Kleinsteuber." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1205069437/34.
Повний текст джерелаBendjador, Hanna. "Correction d'aberrations et quantification de vitesse du son en imagerie ultrasonore ultrarapide." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLS011.
Повний текст джерелаEchography relies on the transmission of ultrasound signals through biological tissues, and the processing of backscattered echoes. The rise of ultrafast ultrasound imaging gave access to physiological events faster than 10 000 frames per second. It allowed therefore the development of high-end techniques such as organs elasticity imaging or sensitive quantification of blood flows. During its propagation through complex or heterogeneous media, the acoustic wavefront may still suffer strong distorsions; hindering both the image quality and the ensuing quantitative assessments. Correcting such aberrations is the ultimate goal of the research work conducted during this PhD. By studying statistical properties of interferences between scatterers, a matrix formalism has been developed to optimise the angular coherence of backscattered echoes. Importantly, we succeeded for the first time, in correcting images and quantifying locally the speed of sound at ultrafast frame rates. Sound speed was proven to be a unique biomarker in the example of hepatic steatosis, and possibly separation of brain white and black matter. The phase correction method will be an interesting contribution to motion correction in the case of 3D tomography and vascular imaging, offering thus new horizons to ultrasound imaging
Salahieh, Basel, Jeffrey J. Rodriguez, Sean Stetson, and Rongguang Liang. "Single-image full-focus reconstruction using depth-based deconvolution." SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2016. http://hdl.handle.net/10150/624372.
Повний текст джерелаWonus, Julie L. (Julie Lynn). "A circuit model for diffusive breast imaging and a numerical algorithm for its inverse problem." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38172.
Повний текст джерелаIncludes bibliographical references (leaves 67-70).
by Julie L. Wonus.
M.Eng.
Dekdouk, Bachir. "Image reconstruction of low conductivity material distribution using magnetic induction tomography." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/image-reconstruction-of-low-conductivity-material-distribution-using-magnetic-induction-tomography(44d6769d-59b1-44c2-a01e-835f8916f69c).html.
Повний текст джерелаBerdeu, Anthony. "Imagerie sans lentille 3D pour la culture cellulaire 3D." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAS036/document.
Повний текст джерелаThis PhD work is at the interface of two fields: 3D cell culture and lens-free imaging.Providing a more realistic cell culture protocol on the physiological level, switching from single-layer (2D) cultures to three-dimensional (3D) cultures - via the use of extracellular gel in which cells can grow in three dimensions - is at the origin of several breakthroughs in several fields such as developmental biology, oncology and regenerative medicine. The study of these new 3D structures creates a need in terms of 3D imaging.On another side, 2D lens-free imaging provides a robust, inexpensive, non-labeling and non-toxic tool to study cell cultures in two dimensions over large scales and over long periods of time. This type of microscopy records the interferences produced by a coherent light scattered by the biological sample. Knowing the physics of the light propagation, these holograms are retro-propagated numerically to reconstruct the unknown object. The reconstruction algorithm replaces the absent lenses in the role of image formation.The aim of this PhD is to show the possibility of adapting this lens-free technology for imaging 3D cell culture. New lens-free microscopes are designed and built along with the development of dedicated tomographic reconstruction algorithms.Concerning the prototypes, several solutions are tested to finally converge to a scheme combining two conditions. The first requirement is the choice of simplicity of use with a cell culture in standard Petri dish and requiring no specific preparation or change of container. The second condition is to find the best possible angular coverage of lighting angles in regards of the geometric constraint imposed by the first requirement. Finally, an incubator-proof version is successfully built and tested.Regarding the algorithms, four major types of solutions are implemented, all based on the Fourier diffraction theorem, conventionally used in optical diffractive tomography. All methods aim to correct two inherent problems of a lens-free microscope: the absence of phase information, the sensor being sensitive only to the intensity of the incident wave, and the limited angular coverage. The first algorithm simply replaces the unknown phase with that of an incident plane wave. However, this method is fast but it is the source of many artifacts. The second solution tries to estimate the missing phase by approximating the unknown object by an average plane and uses the tools of the 2D lens-free microscopy to recover the missing phase in an inverse problem approach. The third solution consists in implementing a regularized inverse problem approach on the 3D object to reconstruct. This is the most effective method to deal with the two problems mentioned above but it is very slow. The fourth and last solution is based on a modified Gerchberg-Saxton algorithm with a regularization step on the object.All these methods are compared and tested successfully on numerical simulations and experimental data. Comparisons with conventional microscope acquisitions show the validity of the reconstructions in terms of shape and positioning of the retrieved objects as well as the accuracy of their three-dimensional positioning. Biological samples are reconstructed with volumes of several tens of cubic millimeters, inaccessible in standard microscopy.Moreover, 3D time-lapse data successfully obtained in incubators show the relevance of this type of imaging by highlighting large-scale interactions between cells or between cells and their three-dimensional environment
Ygouf, Marie. "Nouvelle méthode de traitement d'images multispectrales fondée sur un modèle d'instrument pour la haut contraste : application à la détection d'exoplanètes." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00843202.
Повний текст джерелаZahran, Saeed. "Source localization and connectivity analysis of uterine activity." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2469.
Повний текст джерелаThe technique of EHGI allows a noninvasive reconstruction of the electrical potential on the uterus surface based on electrical potential measured on the body surface and anatomical data of the torso. EHGI provides very precious information about the uterus condition since it is able to provide refined spatial description of the electrical wave pathway and magnitude on the uterus surface. This may help a lot in different clinical interventions. The scientific algorithms behind any EHGI tool are able to preprocess the anatomical data of the patient in order to provide a computational mesh, filter noisy measurements of the electrical potential and solve an inverse problem. The inverse problem in uterus electrohysterography (electrohysterography imaging (EHGI)) is a new and a powerful diagnosis technique. This non-invasive technology interests more and more medical industries. The success of this technology would be considered as a breakthrough in the uterus diagnosis. However, in many cases the quality of reconstructed electrical potential is not accurate enough. The difficulty comes from the fact that the inverse problem in uterus electrohysterography is well known as a mathematically ill-posed problem. Different methods based on Thikhnov regularization have been used in order to regularize the problem. We have conducted our analysis by using a realistic uterus model and have aimed at identifying the spatial extent of the sources
Shilling, Richard Zethward. "A multi-stack framework in magnetic resonance imaging." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33807.
Повний текст джерелаNilsson, Lovisa. "Data-Driven Methods for Sonar Imaging." Thesis, Linköpings universitet, Datorseende, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-176249.
Повний текст джерелаUh, Jinsoo. "Nuclear magnetic resonance imaging and analysis for determination of porous media properties." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4899.
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