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| Author | : Sevan Goenezen |
| Publisher | : |
| Total Pages | : 208 |
| Release | : 2011 |
| Genre | : |
| ISBN | : |
| Author | : Christoph Moosbauer |
| Publisher | : Anchor Academic Publishing (aap_verlag) |
| Total Pages | : 118 |
| Release | : 2015-03-25 |
| Genre | : Technology & Engineering |
| ISBN | : 395489906X |
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.
| Author | : Nachiket Hemant Gokhale |
| Publisher | : |
| Total Pages | : 490 |
| Release | : 2007 |
| Genre | : |
| ISBN | : |
Abstract: It is well known that the mechanical properties of soft tissue can change with tissue pathology. For example, it is observed that the elastic (shear) modulus of malignant breast masses is typically an order of magnitude higher than the back ground of normal glandular tissue. In addition it is also known that with increasing applied strain the stiffness of cancerous soft tissues increases more rapidly than the background of non-malignant soft tissues. Medical imaging techniques such as ultrasound imaging, combined with novel displacement estimation techniques enable the calculation of the displacement field in the interior of soft tissue. While many attempts have been made to use this information to map the linear elastic properties of soft tissue, relatively few attempts have been made that account for both large deformation and material non-linearity in reconstructing the elastic properties. In this dissertation, new algorithms are developed, implemented, and tested to reconstruct the material parameters in non-linear, large deformation hyperelastic tissue models. The overall computational problem is formulated as a constrained minimization problem where the difference between a measured and a predicted displacement field is minimized. Upon discretization, the constraint takes the form of a finite element (FEN) model for the hyperelastic tissue response. In the forward FEM model, due consideration is given to issues of mesh locking which are avoided by the use of enhanced strain and higher order finite elements. The optimization problem is solved efficiently using a quasi-Newton method and adjoint gradient calculation, which significantly reduces the computational costs compared to more traditional approaches. A novel technique based on continuation in the material properties is used to further accelerate the inverse problem solution.
| Author | : Themistocles M. Rassias |
| Publisher | : Springer |
| Total Pages | : 932 |
| Release | : 2018-06-29 |
| Genre | : Mathematics |
| ISBN | : 3319898159 |
New applications, research, and fundamental theories in nonlinear analysis are presented in this book. Each chapter provides a unique insight into a large domain of research focusing on functional equations, stability theory, approximation theory, inequalities, nonlinear functional analysis, and calculus of variations with applications to optimization theory. Topics include: Fixed point theory Fixed-circle theory Coupled fixed points Nonlinear duality in Banach spaces Jensen's integral inequality and applications Nonlinear differential equations Nonlinear integro-differential equations Quasiconvexity, Stability of a Cauchy-Jensen additive mapping Generalizations of metric spaces Hilbert-type integral inequality, Solitons Quadratic functional equations in fuzzy Banach spaces Asymptotic orbits in Hill’sproblem Time-domain electromagnetics Inertial Mann algorithms Mathematical modelling Robotics Graduate students and researchers will find this book helpful in comprehending current applications and developments in mathematical analysis. Research scientists and engineers studying essential modern methods and techniques to solve a variety of problems will find this book a valuable source filled with examples that illustrate concepts.
| Author | : Barry Doyle |
| Publisher | : Springer |
| Total Pages | : 141 |
| Release | : 2015-04-25 |
| Genre | : Technology & Engineering |
| ISBN | : 3319155032 |
The Computational Biomechanics for Medicine titles provide an opportunity for specialists in computational biomechanics to present their latest methodologiesand advancements. Thisvolumecomprises twelve of the newest approaches and applications of computational biomechanics, from researchers in Australia, New Zealand, USA, France, Spain and Switzerland. Some of the interesting topics discussed are:real-time simulations; growth and remodelling of soft tissues; inverse and meshless solutions; medical image analysis; and patient-specific solid mechanics simulations. One of the greatest challenges facing the computational engineering community is to extend the success of computational mechanics to fields outside traditional engineering, in particular to biology, the biomedical sciences, and medicine. We hope the research presented within this book series will contribute to overcoming this grand challenge.
| Author | : Xuchen Liu |
| Publisher | : |
| Total Pages | : |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
Elasticity imaging, which is also known as Elastography, aims to determine the elastic property distribution of non-homogeneous deformable solids such as soft tissues. This can be done non-destructively using displacement fields measured with medical imaging modalities, such as ultrasound or magnetic resonance imaging. Elasticity imaging can potentially be used to detect tumors based on the stiffness contrast between different materials. This requires the solution of an inverse problem in elasticity. This field has been growing very fast in the past decade. One of the most useful applications of elasticity imaging may be in breast cancer diagnosis, where the tumor could potentially be detected and visualized by its stiffness contrast from its surrounding tissues. In this work the inverse problem will be solved for the shear modulus which is directly related to the Young's modulus through the Poisson's ratio. The inverse problem is posed as a constrained optimization problem, where the difference between a computed (predicted) and measured displacement field is minimized. The computed displacement field satisfies the equations of equilibrium. The material is modeled as an isotropic and incompressible material. The present work focuses on assessing the solution of the inverse problem for problem domains defined with a continuous and discontinuous shear modulus distribution. In particular, two problem domains will be considered: 1) a stiff inclusion in a homogeneous background representing a stiff tumor surrounded by soft tissues, 2) a layered ring model representing an arterial wall cross-section. The hypothetical "measured" displacement field for these problem domains will be created by solving the finite element forward problem. Additionally, noise will be added to the displacement field to simulate noisy measured displacement data. According to the results of my thesis work, the potential of the elasticity imaging in the medical field is emerging. The inclusion in problem domain 1, representing a stiffer tumor in a uniform background, can be found and located in the shear modulus reconstructions. Thus, these reconstructed images can potentially be used to detect tumors in the medical field. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155332
| Author | : |
| Publisher | : |
| Total Pages | : 88 |
| Release | : 2008 |
| Genre | : Biomechanics |
| ISBN | : |
This study seeks to simulate soft tissue behavior with a custom finite element analysis. It is the eventual goal of this team to explore the inverse problem of soft tissues, and this simulation study will play an integral role in that process. It is hoped that new information regarding the elastic properties of soft tissue can be used to diagnose disease processes and improve health care delivery. In this investigation, soft tissue is modeled as a linear, isotropic, elastic, and nearly incompressible material. A dynamic finite element problem was defined consistent with the experimental protocol of harmonic motion imaging, an elasticity imaging technique that utilizes acoustic radiation force to induce localized displacements within soft tissue samples. The finite element equations of motion in this investigation were solved using the Newmark method, an approach commonly used by engineers to determine the dynamic response of structures under the action of any general time-dependent loads. It was found that the displacement results obtained with the Newmark method made physical sense and agreed with the observations of other researchers in this field, suggesting that the current finite element analysis is a suitable simulation of soft tissue behavior.
| Author | : Stéphane Avril |
| Publisher | : Springer |
| Total Pages | : 161 |
| Release | : 2016-10-12 |
| Genre | : Technology & Engineering |
| ISBN | : 3319450719 |
The articles in this book review hybrid experimental-computational methods applied to soft tissues which have been developed by worldwide specialists in the field. People developing computational models of soft tissues and organs will find solutions for calibrating the material parameters of their models; people performing tests on soft tissues will learn what to extract from the data and how to use these data for their models and people worried about the complexity of the biomechanical behavior of soft tissues will find relevant approaches to address this complexity.
| Author | : Simon Chatelin |
| Publisher | : Frontiers Media SA |
| Total Pages | : 235 |
| Release | : 2022-11-23 |
| Genre | : Science |
| ISBN | : 2832506801 |
| Author | : Mathias Brieu |
| Publisher | : Academic Press |
| Total Pages | : 534 |
| Release | : 2023-04-21 |
| Genre | : Technology & Engineering |
| ISBN | : 0128236760 |
Biomechanics of the Female Reproductive System: Breast and Pelvic Organs: From Models to Patients synthesizes complementary advances in women’s reproductive biomechanics, medical imaging analysis, patient-specific characterization, and computational finite element models. The book discusses the biomechanical aspects related to the breast and female pelvic floor system at each step of development. The table of contents also covers certain events and diseases, including cancers, delivery, aging, breast, hysterectomy or prolapse surgery. It presents the main biomechanical experimental results obtained and models developed this last decade to highlight the importance of accounting for patient-specific history and aging characteristics to consider damage growth effect and impact. As part of Elsevier’s Biomechanics of Living Organs series, this book provides an opportunity for students, researchers, clinicians and engineers to study the main topics related to the biomechanics of the women’s reproductive system in a single book written by a global base of experts. Introduces fundamental aspects of breast and pelvic floor Anatomy, Physiology and Physiopathology Covers the most recent imaging techniques (such as image analysis reconstruction, elastography, tagged MRI, nondestructive inverse methods) developed to characterize patient-specific anatomy and mechanical properties characteristics Discusses the main computational studies performed this last decade for modeling the delivery process and potential induced injury
