Iterative Methods for the Elasticity Imaging Inverse Problem

Iterative Methods for the Elasticity Imaging Inverse Problem
Author: Brian C. Winkler
Publisher:
Total Pages: 192
Release: 2014
Genre: Diagnostic ultrasonic imaging
ISBN:

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"Cancers of the soft tissue reign among the deadliest diseases throughout the world and effective treatments for such cancers rely no early and accurate detection of tumors within the interior of the body. One such diagnostic tool, known as elasticity imaging or elastography, uses measurements of tissue displacement to reconstruct the variable elasticity between healthy and unhealthy tissue inside the body. This gives rise to a challenging parameter identification inverse problem, that of identifying the Lamé parameter [mu] in a system of partial differential equations in linear elasticity. Due to the near incompressibility of human tissue, however, common techniques for solving the direct and inverse problems are rendered ineffective due to a phenomenon known as the 'locking effect.' Alternative methods, such as mixed finite element methods, must be applied to overcome this complication. Using these methods, this work reposes the problem as a generalized saddle point problem along with a presentation of several optimization formulations, including the modified output least squares (MOLS), energy output least squares (EOLS), and equation error (EE) frameworks, for solving the elasticity imaging inverse problem. Subsequently, numerous iterative optimization methods, including gradient, extragradient, and proximal point methods, are explored and applied to solve the related optimization problem. Implementations of all of the iterative techniques under consideration are applied to all of the developed optimization frameworks using a representative numerical example in elasticity imaging. A thorough analysis and comparison of the methods is subsequently presented."--Abstract.

Inverse Problems In Dynamic Elasticity Imaging

Inverse Problems In Dynamic Elasticity Imaging
Author: Christoph Moosbauer
Publisher: Anchor Academic Publishing (aap_verlag)
Total Pages: 118
Release: 2015-03-25
Genre: Technology & Engineering
ISBN: 395489906X

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Since the early 1990’s, elasticity imaging techniques are developed as a powerful supplement of the medical toolbox in diagnostic analysis and computer aided surgery. By solving a so-called inverse problem, information about the spatial variation of material parameters of soft (human) tissue are derived from displacement data, which can be measured noninvasively using standard imaging devices such as ultrasound or magnetic resonance tomography. The terms of quasi-static and dynamic elastography refer to the type of load situation, by which the tissue in question is excited. The extension of the theoretical formulation and implementation of the underlying inverse problem in quasi-static elastography to time-harmonic approaches poses several additional challenges, which are addressed in detail within the course of this study. We propose a robust strategy for the reconstruction, which takes advantage of the high sensitivity of the accuracy in harmonic elastography to the choice of the starting point. While not being reported in the literature up to now, the quite competing claims of quasi-static and time-harmonic elastography motivate a comprehensive comparison of these two techniques. Via a spectral decomposition of the curvature information of the underlying inverse problem, a clear explanation for an improved robustness of time- harmonic elastography in the presence of inaccuracies due to noise and/or numerical approximations can be given. Several numerical examples confirm these findings as well as the efficiency of the proposed reconstruction strategy. In particular, it is shown that for moderately low frequencies, it is sufficient to use very coarse finite element meshes, so that the only additional computational cost stems from the worse conditioning of the system matrix.

Iterative Optimization in Inverse Problems

Iterative Optimization in Inverse Problems
Author: Charles Byrne
Publisher: CRC Press
Total Pages: 298
Release: 2014-02-12
Genre: Business & Economics
ISBN: 1482222345

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Iterative Optimization in Inverse Problems brings together a number of important iterative algorithms for medical imaging, optimization, and statistical estimation. It incorporates recent work that has not appeared in other books and draws on the author's considerable research in the field, including his recently developed class of SUMMA algorithms

Mathematical Methods in Elasticity Imaging

Mathematical Methods in Elasticity Imaging
Author: Habib Ammari
Publisher: Princeton University Press
Total Pages: 240
Release: 2015-04-05
Genre: Mathematics
ISBN: 1400866626

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This book is the first to comprehensively explore elasticity imaging and examines recent, important developments in asymptotic imaging, modeling, and analysis of deterministic and stochastic elastic wave propagation phenomena. It derives the best possible functional images for small inclusions and cracks within the context of stability and resolution, and introduces a topological derivative–based imaging framework for detecting elastic inclusions in the time-harmonic regime. For imaging extended elastic inclusions, accurate optimal control methodologies are designed and the effects of uncertainties of the geometric or physical parameters on stability and resolution properties are evaluated. In particular, the book shows how localized damage to a mechanical structure affects its dynamic characteristics, and how measured eigenparameters are linked to elastic inclusion or crack location, orientation, and size. Demonstrating a novel method for identifying, locating, and estimating inclusions and cracks in elastic structures, the book opens possibilities for a mathematical and numerical framework for elasticity imaging of nanoparticles and cellular structures.

Iterative Methods for Approximate Solution of Inverse Problems

Iterative Methods for Approximate Solution of Inverse Problems
Author: A.B. Bakushinsky
Publisher: Springer Science & Business Media
Total Pages: 298
Release: 2007-09-28
Genre: Mathematics
ISBN: 140203122X

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This volume presents a unified approach to constructing iterative methods for solving irregular operator equations and provides rigorous theoretical analysis for several classes of these methods. The analysis of methods includes convergence theorems as well as necessary and sufficient conditions for their convergence at a given rate. The principal groups of methods studied in the book are iterative processes based on the technique of universal linear approximations, stable gradient-type processes, and methods of stable continuous approximations. Compared to existing monographs and textbooks on ill-posed problems, the main distinguishing feature of the presented approach is that it doesn’t require any structural conditions on equations under consideration, except for standard smoothness conditions. This allows to obtain in a uniform style stable iterative methods applicable to wide classes of nonlinear inverse problems. Practical efficiency of suggested algorithms is illustrated in application to inverse problems of potential theory and acoustic scattering. The volume can be read by anyone with a basic knowledge of functional analysis. The book will be of interest to applied mathematicians and specialists in mathematical modeling and inverse problems.

Inverse Problems in Transcient [sic] Elastography

Inverse Problems in Transcient [sic] Elastography
Author: Yat Tin Chow
Publisher:
Total Pages: 204
Release: 2012
Genre: Diagnostic ultrasonic imaging
ISBN:

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Multi-dimensional coefficient inverse problem (MCIP) in linear elasticity has found many applications, such as crack detection, oil/salt/ore detection, medical imaging. Transient elastography is among one of the most useful applications, providing a fast and safe medical imaging technique which can be used to detect tumors or abnormal tissue in fast-moving organs such as the liver. In this thesis focus is casted on two of the numerical algorithms to solve inverse problems related to transient elastography, namely the level-set inversion method and the approximate globally convergent method. The derivations of both methods and numerical results are presented. In particular, the approximate globally convergent method is a newly developed stable method to solve coefficient determination inverse problem for hyperbolic partial differential equation proposed by Beilina and Klibanov in [6]. It achieves pproximately a global convergence by avoiding construction of a least squares functional, thus averting some of the well-known problems of trapping in the neighborhoods of local minima when one minimizes such a nonlinear functional. The results of the approximate globally convergent method have shown its strong stability and robustness. This suggests a good way for the reconstruction of the distribution of the shear modulus in the coefficient inverse problem of linear elasticity.

Essays in Mathematics and its Applications

Essays in Mathematics and its Applications
Author: Themistocles M. Rassias
Publisher: Springer
Total Pages: 659
Release: 2016-06-14
Genre: Mathematics
ISBN: 331931338X

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This volume, dedicated to the eminent mathematician Vladimir Arnold, presents a collection of research and survey papers written on a large spectrum of theories and problems that have been studied or introduced by Arnold himself. Emphasis is given to topics relating to dynamical systems, stability of integrable systems, algebraic and differential topology, global analysis, singularity theory and classical mechanics. A number of applications of Arnold’s groundbreaking work are presented. This publication will assist graduate students and research mathematicians in acquiring an in-depth understanding and insight into a wide domain of research of an interdisciplinary nature.

Nonlinear Analysis and Optimization

Nonlinear Analysis and Optimization
Author: Boris S. Mordukhovich
Publisher: American Mathematical Soc.
Total Pages: 330
Release: 2016-02-26
Genre: Mathematics
ISBN: 1470417367

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This volume contains the proceedings of the IMU/AMS Special Session on Nonlinear Analysis and Optimization, held from June 16-19, 2014, at the Second Joint International Meeting of the Israel Mathematical Union (IMU) and the American Mathematical Society (AMS), Bar-Ilan and Tel-Aviv Universities, Israel, and the Workshop on Nonlinear Analysis and Optimization, held on June 12, 2014, at the Technion-Israel Institute of Technology. The papers in this volume cover many different topics in Nonlinear Analysis and Optimization, including: Taylor domination property for analytic functions in the complex disk, mappings with upper integral bounds for p -moduli, multiple Fourier transforms and trigonometric series in line with Hardy's variation, finite-parameter feedback control for stabilizing damped nonlinear wave equations, implicit Euler approximation and optimization of one-sided Lipschitz differential inclusions, Bolza variational problems with extended-valued integrands on large intervals, first order singular variational problem with nonconvex cost, gradient and extragradient methods for the elasticity imaging inverse problem, discrete approximations of the entropy functional for probability measures on the plane, optimal irrigation scheduling for wheat production, existence of a fixed point of nonexpansive mappings in uniformly convex Banach spaces, strong convergence properties of m-accretive bounded operators, the Reich-Simons convex analytic inequality, nonlinear input-output equilibrium, differential linear-quadratic Nash games with mixed state-control constraints, and excessive revenue models of competitive markets.

Learning Robust Data-driven Methods for Inverse Problems and Change Detection

Learning Robust Data-driven Methods for Inverse Problems and Change Detection
Author: Davis Leland Gilton
Publisher:
Total Pages: 139
Release: 2021
Genre:
ISBN:

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The field of image reconstruction and inverse problems in imaging have been revolutionized by the introduction of methods which learn to solve inverse problems. This thesis investigates a variety of methods for learning to solve inverse problems by leveraging data: first by exploring the online sparse linear bandit setting, and then by investigating modern methods for leveraging training data to learn to solve inverse problems. In addition, this thesis explores a multi-model method of leveraging human descriptions of change in time series of images to regularize a graph-cut-based change-point detection method. Recent research into learning to solve inverse problems has been dominated by "unrolled optimization" approaches, which unroll a fixed number of iterations of an iterative optimization algorithm, replacing one or more elements of that algorithm with a neural network. These methods have several attractive properties: they can leverage even limited training data to learn accurate reconstructions, they tend to have lower runtime and require fewer iterations than more standard methods which leverage non-learned regularizers, and they are simple to implement and understand. However, learned iterative methods, like most learned inverse problem solvers, are sensitive to small changes in the data measurement model; they are uninterpretable, suffering reduced reconstruction quality if run for more or fewer iterations than were used at train time; and they are limited by memory and numerical constraints to small numbers of iterations, potentially lowering the ceiling for best available reconstruction quality using these methods. This thesis proposes an alternative architecture design based on a Neumann series, which is attractive from a practical perspective for its sample complexity performance and ease to train compared to methods based on unrolled iterative optimization. In addition, this thesis proposes and tests two techniques to adapt arbitrary trained inverse problem solvers to different measurement models, enabling deployment of a single learned model on a variety of forward models without sacrificing performance or requiring potentially-costly new data. Finally, this thesis demonstrates how to train iterative solvers that are unrolled for an arbitrary number of iterations. The proposed technique for the first time permits deep iterative solvers that admit practical convergence guarantees, while allowing flexibility in trading off computation for performance.