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In a variety of biomedical applications, cavitation occurs in soft tissue. Although significant amounts of research have been performed on cavitation in water, bubble dynamics, and related bioeffects remain poorly understood. We use numerical simulations of spherical bubble dynamics in soft tissue to assess the extent to which viscoelasticity affects "known" and introduces "new" damage mechanisms. We find that deviatoric stresses - although not an important damage mechanism in water - are significantly enhanced and could be an important bioeffect mechanism in tissue. Both the viscoelastic properties and the nonlinear, large-collapse radius contribute to stress amplification in the surroundings. In addition, temperatures in the surrounding medium increase more in the Zener tissue than in water, due to viscous heating. [ABSTRACT FROM AUTHOR]

The cornea is a transparent soft tissue at the front of the eye and is mainly responsible for refracting the incoming light and protecting the internal contents of the eye. Although the cornea is composed of different components, it is well-known that its biomechanical properties are due to the structure and function of its extracellular matrix, called stroma. The stroma is composed of regularly arranged collagen fibers embedded in a hydrated proteoglycans matrix. From a mechanics viewpoint, the stroma can be considered as a composite structure in which the collagen fibrils and the hydrated matrix take tensile and compressive forces, respectively. In this work, experimental and computational studies conducted to fully characterize the mechanical properties of the cornea in compression and tension. The unconfined compression experiments were conducted on corneal disks while uniaxial tensile tests were performed on corneal rectangular strips. A transversely isotropic constitutive model was used to numerically analyze the experimental measurements and determine the material constants of the cornea. It is shown that the material properties of the cornea in tension and compression are hydration dependent. Therefore, careful attention must be taken in corneal hydration during material characterization experiments. [ABSTRACT FROM AUTHOR]

In this work we numerically implement a previously developed large deformation model for porous fibre-reinforced materials with statistically oriented fibres, including the effect of the presence of the fibres on both the elastic properties and the permeability. The model is microstructural, based on observations made at different length-scales: the microscopic scale of the porous matrix, the mesoscopic scale of the reinforcing fibres, and the macroscopic scale of the system as a whole, and makes use of upscaling techniques. The implementation makes use of the open-source Finite Element package FEBio, which allows for full customisation of the constitutive equations. We first study a benchmark test in which only the effect of the fibre orientation on the permeability is accounted for. Then we simulate an unconfined compression test on a sample of articular cartilage, with realistic histological features, such as the volumetric fractions of the matrix and collagen fibres and fibre orientation. [ABSTRACT FROM AUTHOR]

Ultrasound (US) image segmentation can be a challenging task due to signal dropouts, missing boundaries, and presence of speckle. Typically, purely intensity-based methods do not lead to a good segmentation of the structures of interest. Prior work has shown that local phase and feature asymmetry, derived from the monogenic signal, extract structural information from US images. This paper proposes a novel US segmentation approach based on the fuzzy connectedness framework. The approach uses local phase and feature asymmetry to define the so-called affinity function, which drives the segmentation algorithm, incorporates a shape-based object completion step, and regularises the result by mean curvature flow. Identifying new image-based biomarkers of fetal nutrition across gestation is essential to characterise the well-being of a fetus at an early stage. Results are presented on US images of the fetal arm taken at multiple gestational ages, the adipose tissue being an indicator of the fetal nutritional state. [ABSTRACT FROM PUBLISHER]

In order to reduce deflection of the stabbing needle and increase the accuracy of the robot-assisted needle insertion into soft tissue, A physical model of stabbing needle is built with elastic beam. We put forward a algorithm to analyze force added on stabbing needle and got the deflection and angle of element node. The theoretical calculation and experimental simulation shows the validation and consistency of the algorithm. The dynamic process of the soft tissue deformation during needle insertion is decomposed into a set of discrete quasi-static stages. We got every note's displacement and force distribution of the soft tissue by simulating needle insertion into two and three dimensional tissue, which provide significant reference with predicting soft tissue deformation and planning before surgery. [ABSTRACT FROM PUBLISHER]

To investigate the effects of bony structure simplification methods on the biomechanics of knee's cartilage and menisci under compression and torsion effects in series of flexion angles, the MRI images of the normal human knee at flexion angles of 0¡ã/25¡ã/60¡ã/80¡ã were developed through SONATA MAESTRO 1.5T, then through the technology of threshold segmentation and registration assembly, bone tissue distinguished models and single material models were built based on these images. The results show that: (1) Under three kinds of loads, the effects of bony structure simplification methods on the maximum equivalent stress of the cartilage in series of flexion angles were significant. At 0¡ãand 80¡ã, the maximum equivalent stresses of bone tissue distinguished models were much bigger than single material models. (2) The bearing load on cruciate ligaments of bone tissue distinguished models reduced. At 0¡ã~60¡ã, the maximum equivalent stress on ACL decreased with the more detailed bony structure. (3) The maximum equivalent stress of bone tissue distinguished models were chiefly bigger than single material models in series of flexion angles. The menisci of bone tissue distinguished models will bear more loads than single material models. (4) The stresses on soft tissue of two kinds of models all elevated with the increase of flexion angle, so bony structure simplification methods did not affect the stress trends with the change of flexion angle. But at 0¡ãand 80¡ã, the effects of bony structure simplification methods on biomechanics of knee's cartilage, ligaments and menisci were significant. The study provided techniques and data for definition of tibiofemoral joint material properties during the mechanical analysis of knee motion. [ABSTRACT FROM PUBLISHER]

Although the mechanical behaviour of soft tissue has been extensively studied, the interaction between the collagen fibres and the ground matrix has not been well understood and is therefore ignored by most constitutive models of soft tissue. In this paper, the human annulus fibrosus is used as an example and the potential fibre-matrix interaction is identified by careful investigation of the experimental results of biaxial and uniaxial testing of the human annulus fibrosus. First, the uniaxial testing result of the HAF along the axial direction is analysed and it is shown that the mechanical behaviour of the ground matrix can be well simulated by the incompressible neo-Hookean model when the collagen fibres are all under contraction. If the collagen fibres are stretched, the response of the ground matrix can still be described by the incompressible neo-Hookean model, but the effective stiffness of the matrix depends on the fibre stretch ratio. This stiffness can be more than 10 times larger than the one obtained with collagen fibres under contraction. This phenomenon can only be explained by the fibre-matrix interaction. Furthermore, we find that the physical interpretation of this interaction includes the inhomogeneity of the soft tissue and the fibre orientation dispersion. The dependence of the tangent stiffness of the matrix on the first invariant of the deformation tensor can also be explained by the fibre orientation dispersion. The significant effect of the fibre-matrix interaction strain energy on mechanical behaviour of the soft tissue is also illustrated by comparing some simulation results. [ABSTRACT FROM AUTHOR]

Mammography is the primary method for screening and detecting breast cancers. However, it frequently fails to detect small tumors and is not quite specific in terms of tumor benignity and malignancy. The objective of this paper is to develop a new imaging modality called elasto-mammography that generates the modulus elastograms based on conventional mammographs. A new elastic reconstruction method is described based on elastography and mammography for breast tissues. Elastic distribution can be reconstructed through the measurement of displacement provided by mammographic projection. It is shown that the proposed elasto-mammography provides higher sensitivity and specificity than the conventional mammography on its own for breast cancer diagnosis. [ABSTRACT FROM AUTHOR]

An analytical representation of the structural stress tensor which describes the fiber dispersion in soft biological tissue has been represented. The mathematical form is computationally efficient compared to the angular integration schemes and it interelates the cellular scale fiber rotation concept with macroscopic deformation of the tissue. It has been shown that, based on well known cellular rotation concepts, the steady state second Piola-Kirschoff stress tensor can be described by a set of structural and remodeling variables, and the current strain tensor. [ABSTRACT FROM AUTHOR]

STATEMENT OF PURPOSE Diaphragm is composed of a peripheral part (muscular fiber) and a central part (tendon). The tendon is the upper part of the diaphragm, in contact with the lungs and is closer to the front than to the back of the thorax, so that the posterior muscular fibers are longer. The central tendon is composed of several planes of fibers, whose arrangement gives strength and rigidity to the membrane (1-3). In this study a comparison between the tensile mechanical properties of tendon part of diaphragm and electrospun PA-6 nanofibers has been done. [ABSTRACT FROM AUTHOR]