Deformation Of Biological Tissues Research Articles

Sex differences in body composition and shock attenuation during running

Running-related impact shock is absorbed via biological tissue deformation. Given known sex differences in body composition, shock attenuation may also differ between sexes thereby influencing sex-specific running-related injury risk. This study examined sex differences in body composition and shock attenuation during running. Seventeen female (mean ± 1SD age: 34.7 ± 16.1) and twenty-one male runners (age: 29.0 ± 13.8) ran overground as inertial measurement units with triaxial accelerometers measured impact shock at the distal tibia and low-back. Frequency-domain axial and resultant shock attenuation were calculated between the low-back relative to the tibia using a transfer function of the power spectral density within 9–20, 21–35, and 36–50 Hz. Bone mineral density and content, fat and lean mass were measured in the lower extremity and pelvis/gynoid regions using dual x-ray absorptiometry. The association between sex and shock attenuation was tested using age-adjusted linear regression models, adjusted and unadjusted for body composition as a post-hoc analysis (α = 0.05). Body composition variables normalized to body mass were compared between sexes using independent samples t-tests (α = 0.05). Body composition differed between sexes (p-range: <0.001–0.01, Cohen’s d range: 0.17–2.41). Before adjusting for body composition, sex was not significantly associated with axial or resultant shock attenuation (p > 0.05), but adjusting for select body composition variables like lower extremity lean and bone mass revealed greater attenuation in females than males (β-range: −124.76 to −46.42, negative indicates greater attenuation; p-range = 0.004–0.04). Sex may not influence shock attenuation during running, but body composition must be accounted for to better understand this association and consequently sex-specific tissue capacities relative to applied loads.

An asymptotically consistent morphoelastic shell model for compressible biological structures with finite-strain deformations

We derive an asymptotically consistent morphoelastic shell model to describe the finite deformations of biological tissues using the variational asymptotic method. Biological materials may exhibit remarkable compressibility when under large deformations, and we take this factor into account for accurate predictions of their morphoelastic changes. The morphoelastic shell model combines the growth model of Rodriguez et al. and a novel shell model developed by us. We start from the three-dimensional (3D) morphoelastic model and construct the optimal shell energy based on a series expansion around the middle surface. A two-step variational method is applied that retains the leading-order expansion coefficient while eliminating the higher-order ones. The main outcome is a two-dimensional (2D) shell energy depending on the stretching and bending strains of the middle surface. The derived morphoelastic shell model is asymptotically consistent with three-dimensional morphoelasticity and can recover various shell models in literature. Several examples are shown for the verification and illustration.

Numerical study on thermal and deformation analysis of biological tissue during thawing process

Knowledge of the temperature and deformation of biological tissue during cryosurgical re-warming is critical for the survival of healthy tissues. But few theoretical efforts are made to analyze the re-warming process of frozen biological tissue. To better understand the mechanisms involved, a 2D numerical example is used to simulating the thawing process of frozen biological tissue in the context of generalized bio-thermoelastic theory which can predict heat travels at finite speed. The effective heat capacity method and finite element method are used to obtain the temperature, deformation and the phase change process of biological tissue during thawing. The effects of relaxation time, initial temperature and surface heating temperature on the responses are discussed and illustrated graphically.

High-accuracy optical coherence elastography digital volume correlation methods to measure depth regions with low correlation.

The decreasing correlation of optical coherence tomography (OCT) images with depth is an unavoidable problem for the depth measurement of the digital volume correlation (DVC) based optical coherence elastography (OCE) method. We propose an OCE-DVC method to characterize biological tissue deformation in deeper regions. The method proposes a strategy based on reliability layer guided displacement tracking to achieve the OCE-DVC method for the deformation measurement in deep regions of OCT images. Parallel computing solves the computational burden associated with the OCE-DVC method. The layer-by-layer adaptive data reading methods are used to guarantee the parallel computing of high-resolution OCT images. The proposed method shown in this study nearly doubles the depth of quantitative characterization of displacement and strain. At this depth, the standard deviation of displacement and strain measurements is reduced by nearly 78%. Under nonuniform deformation field, OCE-DVC method tracked the displacement with large strain gradient in depth region.

Spatio-Temporal Dynamics of Diffusion-Associated Deformations of Biological Tissues and Polyacrylamide Gels Observed with Optical Coherence Elastography.

In this work, we use the method of optical coherence elastography (OCE) to enable quantitative, spatially resolved visualization of diffusion-associated deformations in the areas of maximum concentration gradients during diffusion of hyperosmotic substances in cartilaginous tissue and polyacrylamide gels. At high concentration gradients, alternating sign, near-surface deformations in porous moisture-saturated materials are observed in the first minutes of diffusion. For cartilage, the kinetics of osmotic deformations visualized by OCE, as well as the optical transmittance variations caused by the diffusion, were comparatively analyzed for several substances that are often used as optical clearing agents, i.e., glycerol, polypropylene, PEG-400 and iohexol, for which the effective diffusion coefficients were found to be 7.4 ± 1.8, 5.0 ± 0.8, 4.4 ± 0.8 and 4.6 ± 0.9 × 10-6 cm2/s, respectively. For the osmotically induced shrinkage amplitude, the influence of the organic alcohol concentration appears to be more significant than the influence of its molecular weight. The rate and amplitude of osmotically induced shrinkage and dilatation in polyacrylamide gels is found to clearly depend on the degree of their crosslinking. The obtained results show that observation of osmotic strains with the developed OCE technique can be applied for structural characterization of a wide range of porous materials, including biopolymers. In addition, it may be promising for revealing alterations in the diffusivity/permeability of biological tissues that are potentially associated with various diseases.

Micro-mechanism study on tissue removal behavior under medical waterjet impact using coupled SPH-FEM.

To fully grasp the numerical characteristics of the interaction process between medical waterjet and soft tissue, the smoothed particle hydrodynamics (SPH)-finite element method (FEM) was used in the simulation of this complex process to avoid the unstable error caused by indirect measurement in experiments. The SPH was applied to the numerical simulation of medical waterjet, and a three-dimensional model of gelatin sample was proposed with the FEM. The impact process between two extremely deformed materials was reproduced, and the established model was verified by comparison with experimental data; the comparison showed relatively consistent results. The separation effect under three operating modes was deduced with the stress and strain range. For the vertical impact condition, the higher the waterjet impact pressure is, the higher the biological tissue deformation bulge height is. For oblique intrusion, the longitudinal separation rate decreases and the kerf width increases with the increase of the incident angle. For the moving impact condition, with the increase of the waterjet moving speed, the longitudinal high-stress distribution range of the impact object decreases slightly.

Time-dependent deformation of biological tissue under ultrasonic irradiation

This work proposes a theoretical model for analyzing the time-dependent deformation of poroelastic materials, as a tissue model, under the action of an ultrasonic field, which considers the diffusion fluid transport that obeys Darcy's law. An acoustomechanical constitutive law is developed, which takes into account the mechanical stress generated by poroelastic deformation based on the classical poroelastic theory and the acoustic radiation stress generated by propagating ultrasonic waves. As an example, the time-dependent deformation of a poroelastic sheet subjected to two counter-propagating waves is calculated using the theoretical model, which is also verified by our finite element model. The results show that the sheet can be stretched or compressed, which depends on the ratio of the sheet thickness to the acoustic wavelength. Additionally, by exploring the relaxation process of the acoustic deformation, the role of the sheet thickness and porosity in determining the time of poroelastic relaxation is examined. This work is very helpful for understanding the deformation of tissues under ultrasonic fields, and also provides a method to extract the mechanical properties of tissues.

Deformations of biological tissues with photothermal nanoparticles under laser irradiation

In this work, optical coherence tomography (OCT) of gel phantoms and cartilage tissue of the joint impregnated with nanoparticles was performed under laser exposure to an erbium fiber laser with a wavelength of 1.56 m. Multifunctional "magnetite + gold" nanoparticles with a "core-shell" structure were obtained by pulsed laser ablation of metals in a liquid, and oxide bronzes KxTiO2 and NaxTiO2 are formed in the processes of self-propagating high-temperature synthesis and mechanical activation. An improvement in the efficiency of the diagnostic method by introducing antireflection additives and absorbing nanoparticles due to a decrease in the irradiation intensity and an increase in the photothermal effect is shown. OCT elastography data indicate the dependence of tissue deformation on the preliminary history of tissue exposure.

EXPERIMENTAL MODELING OF A RESIDUAL WOUND CAVITY ON A BALISTIC PLASTICINE USING CONVENTIONAL AND HOLLOW POINT BULLETS

Relevance. Local armed conflicts of recent decades around the world are characterized by the use of hollow point (HP) bullets, which is another challenge for military surgeons. This confirms the importance for scientific research, in particular, experimental, aimed at studying the ballistic properties of various types of ammunition and the characteristics of the injuries caused by them in the wounded people. Simulation of a gunshot wound canal is an integral stage in the study of the gunshot wounds formation mechanism and is the subject of research in wound ballistics.&#x0D; Objective of the work is to develop an experimental model for ballistic imitation of the plastic deformation of biological tissues caused by the action of HP and non-HP bullets.&#x0D; Materials and methods. The studies were carried out on 40 blocks of ballistic plasticine, in each of which one shot was fired from an AKS-74 assault rifle and a ZBROYAR Z-10 carbine. Depending on the type of ammunition, the blocks of ballistic plasticine were divided into 4 groups: group I - 10 blocks, into which shots were made with non-HP military cartridges 5.45 mm with "PS" bullets with a steel core "7N6"; Group II (10 blocks) - 5.45x39 mm cartridges with V-Max HP bullets; group ІІІ (10 blocks) - with cartridges 7.62x39 mm; group IV (10 blocks) - cartridges 7.62x39 mm with HP bullets of the "SP" type.&#x0D; Results. It was found that when using non-HP bullets, the outer area of ​​the inlet ball hole correlates with the projectile caliber (1.6 times more than when using 7.62 mm bullets). For HP bullets, the caliber of the projectile does not significantly affect the area of ​​the entrance opening (P &lt;0.05). The expanding properties of the bullet significantly increase the area of ​​the bullet hole by 14.87-31.2 times compared to non-HP ammunition. An increase in the caliber of non-HP bullets leads to a significant increase in the area of ​​the sagittal section of the residual wound cavity by 1.59-2.03 times; The expanding properties of bullets of different calibers have a different effect on the volume of the residual wound cavity: for 5.45 mm bullets, the residual wound cavity increases 1.49 times, for 7.62 mm bullets it decreases 1.65 times.&#x0D; Conclusions. The type of small arms, the caliber of the cartridge, its expanding properties affect the spatial configuration of the main ballistic indicators arising in the proposed model of plastic deformation of soft tissues. The use of HP bullets leads to the formation of a larger volume of irreversible damage due to plastic deformation in comparison with non-HP analogs.

Finite-element kalman filter with state constraint for dynamic soft tissue modelling

This research work proposes a novel method for realistic and real-time modelling of deformable biological tissues by the combination of the traditional finite element method (FEM) with constrained Kalman filtering. This methodology transforms the problem of deformation modelling into a problem of constrained filtering to estimate physical tissue deformation online. It discretises the deformation of biological tissues in 3D space according to linear elasticity using FEM. On the basis of this, a constrained Kalman filter is derived to dynamically compute mechanical deformation of biological tissues by minimizing the error between estimated reaction forces and applied mechanical load. The proposed method solves the disadvantage of costly computation in FEM while inheriting the superiority of physical fidelity.

Multifunctional and Ultrathin Electronic Tattoo for On-Skin Diagnostic and Therapeutic Applications.

Epidermal electronic systems for detecting electrophysiological signals, sensing, therapy, and drug delivery are at the frontier in man-machine interfacing for healthcare. However, it is still a challenge to develop multifunctional bioapplications with minimal invasiveness, biocompatibility, and stable electrical performance under various mechanical deformations of biological tissues. In this study, a natural silk protein with carbon nanotubes (CNTs) is utilized to realize an epidermal electronic tattoo (E-tattoo) system for multifunctional applications that address these challenging issues through dispersing highly conductive CNTs onto the biocompatible silk nanofibrous networks with porous nature to construct skin-adhesive ultrathin electronic patches. Individual components that incorporate electrically and optically active heaters, a temperature sensor (temperature coefficient of resistance of 5.2 × 10-3 °C-1 ), a stimulator for drug delivery (>500µm penetration depth in skin), and real-time electrophysiological signal detectors are described. This strategy of E-tattoos integrated onto human skin can open a new route to a next-generation electronic platform for wearable and epidermal bioapplications.

Extended Kalman Filter Nonlinear Finite Element Method for Nonlinear Soft Tissue Deformation

Background and Objective: Soft tissue modelling is crucial to surgery simulation. This paper introduces an innovative approach to realistic simulation of nonlinear deformation behaviours of biological soft tissues in real time.Methods: This approach combines the traditional nonlinear finite-element method (NFEM) and nonlinear Kalman filtering to address both physical fidelity and real-time performance for soft tissue modelling. It defines tissue mechanical deformation as a nonlinear filtering process for dynamic estimation of nonlinear deformation behaviours of biological tissues. Tissue mechanical deformation is discretized in space using NFEM in accordance with nonlinear elastic theory and in time using the central difference scheme to establish the nonlinear state-space models for dynamic filtering.Results: An extended Kalman filter is established to dynamically estimate nonlinear mechanical deformation of biological tissues. Interactive deformation of biological soft tissues with haptic feedback is accomplished as well for surgery simulation.Conclusions: The proposed approach conquers the NFEM limitation of step computation but without trading off the modelling accuracy. It not only has a similar level of accuracy as NFEM, but also meets the real-time requirement for soft tissue modelling.

Електронні засоби дослідження механічних властивостей біологічних тканин

The paper shows the relevance of studying the mechanical properties of biological tissues and biocompatible materials for solving the problems of general and reconstructive surgery, transplantology, manual therapy, virtual simulation of surgical operations, robotic surgery, etc. The authors present basic information about biological tissue as an object of research and give a brief overview of the devices used for studying the mechanical characteristics of biological tissues. An experimental system for testing deformations of biological tissues and biocompatible materials during compression is described. The system is developed using modern hardware and software, as well as effective technical solutions. The results of the practical use of the developed device are presented and the obtained dependences of the mechanical stress of biological tissue samples on their deformation under pressure are analyzed. The system has high metrological characteristics and low cost, and allows performing all the necessary functions for measuring, processing and visualizing the data. The measurements obtained with this system can help form the recommendations for doctors on choosing the optimal operation mode of medical devices and instruments in each specific case. In addition, the measured data can be used to create mathematical models of biological tissues and biocompatible materials in order to further carry out virtual experiments. In further studies, the authors plan to create the mathematical models of biological tissues based on the finite element method and using the actual values characterizing the tissue, obtained with the developed system.

The decomposition of deformation: New metrics to enhance shape analysis in medical imaging.

In landmarks-based Shape Analysis size is measured, in most cases, with Centroid Size. Changes in shape are decomposed in affine and non affine components. Furthermore the non affine component can be in turn decomposed in a series of local deformations (partial warps). If the extent of deformation between two shapes is small, the difference between Centroid Size and m-Volume increment is barely appreciable. In medical imaging applied to soft tissues bodies can undergo very large deformations, involving large changes in size. The cardiac example, analyzed in the present paper, shows changes in m-Volume that can reach the 60%. We show here that standard Geometric Morphometrics tools (landmarks, Thin Plate Spline, and related decomposition of the deformation) can be generalized to better describe the very large deformations of biological tissues, without losing a synthetic description. In particular, the classical decomposition of the space tangent to the shape space in affine and non affine components is enriched to include also the change in size, in order to give a complete description of the tangent space to the size-and-shape space. The proposed generalization is formulated by means of a new Riemannian metric describing the change in size as change in m-Volume rather than change in Centroid Size. This leads to a redefinition of some aspects of the Kendall's size-and-shape space without losing Kendall's original formulation. This new formulation is discussed by means of simulated examples using 2D and 3D platonic shapes as well as a real example from clinical 3D echocardiographic data. We demonstrate that our decomposition based approaches discriminate very effectively healthy subjects from patients affected by Hypertrophic Cardiomyopathy.

A Mathematical Model of Spatial Self-Organization in a Mechanically Active Cellular Medium

A general continual model of a medium composed of mechanically active cells is proposed. The medium is considered to be formed by three phases: cells, extracellular fluid, and an additional phase that is responsible for active interaction forces between cells and, for instance, may correspond to a system of protrusions that provide the development of active contractile forces. The deformation of the medium, which is identified with the deformation of the cell phase, consists of two components: elastic deformation of individual cells and cell rearrangements. The elastic deformation is associated with stresses in the cell phase. The spherical component of the stress tensor describes the nonlinear resistance of the cellular medium, which leads to the impossibility of its excessive compression. The constitutive equation for pressure in the cell phase is taken in the form of a nonlinear dependence on the volume cell density. The rearrangement of cells is considered as a flow controlled by stresses in the cell phase, active stresses, and fluid pressure. The tensor of active stresses is assumed to be spherical and nonlocally dependent on the cell density. Assuming that the process of biological tissue deformation is slow, we obtained a reduced model that neglects the elastic deformation of cells, compared to the inelastic deformation. A linear stability analysis of a spatially uniform steady-state solution was performed. The hydrostatic pressure of fluid is present among the parameters that are responsible for the loss of stability of the steady-state solution: an increase in it has a destabilizing effect owing to the action of the component of the interphase interaction force that is determined by the fluid pressure. The model we obtained can be used to describe the process of cavity formation in an initially homogeneous cell spheroid. The role of local and nonlocal mechanisms of active stress generation in the formation of cavity is investigated.

A physics based approach to the pulse wave velocity prediction in compliant arterial segments

Pulse wave velocity (PWV) quantification commonly serves as a highly robust prognostic parameter being used in a preventative cardiovascular therapy. Being dependent on arterial elastance, it can serve as a marker of cardiovascular risk. Since it is influenced by a blood pressure (BP), the pertaining theory can lay the foundation in developing a technique for noninvasive blood pressure measurement. Previous studies have reported application of PWV, measured noninvasively, for both the estimation of arterial compliance and blood pressure, based on simplified physical or statistical models. A new theoretical model for pulse wave propagation in a compliant arterial segment is presented within the framework of pseudo-elastic deformation of biological tissue undergoing finite deformation. An essential ingredient is the dependence of results on nonlinear aspects of the model: convective fluid phenomena, hyperelastic constitutive relation, large deformation and a longitudinal pre-stress load. An exact analytical solution for PWV is presented as a function of pressure, flow and pseudo-elastic orthotropic parameters. Results from our model are compared with published in-vivo PWV measurements under diverse physiological conditions. Contributions of each of the nonlinearities are analyzed. It was found that the totally nonlinear model achieves the best match with the experimental data. To retrieve individual vascular information of a patient, the inverse problem of hemodynamics is presented, calculating local orthotropic hyperelastic properties of the arterial wall. The proposed technique can be used for non-invasive assessment of arterial elastance, and blood pressure using direct measurement of PWV, with account of hyperelastic orthotropic properties.

Technique for &lt;i&gt;In-Vivo&lt;/i&gt; Measurements of Heart Deformation Using Digital Image Correlation

Many techniques used to measure the deformation of biological tissue are inadequate for measuring deformations of hearts in vivo. Bull Frogs (Rana Catesbeiana) were double-pithed and dissected to expose the amphibian heart for the measurements conducted in this study. White titanium dioxide powder and black charcoal were applied to the surface of the heart to create an artificial surface pattern with high contrast that does not react with the heart muscle or mask surface details. This pattern was then used in conjunction with three dimensional Digital Image Correlation (DIC) to measure full field deformations of the heart through several cardiac cycles. These deformations were measured with a spatial resolution of approximately 0.4 µm and temporal resolution of 50 Hz.

Enhancing the performance of lateral shear strain estimation by using 2-D strain imaging.

Radio-frequency (RF) ultrasound can be used to estimate deformation of biological tissue. Decorrelation of sequentially acquired ultrasound signals resulting from the deformation imposes a limitation on the precision (elastographic signal-to-noise ratio; SNRe) of estimating these deformations; this is presented as the lateral shear strain filter. In this paper, we explore the effect of a 2-D-window-based strain estimation approach on the lateral shear strain filter and propose an extension of the 1-D theoretical lateral shear strain filter to 2-D. We compared the performance of the 2-D approach in simulated ultrasound data and a tissue-mimicking phantom with that of the 2-D lateral shear strain filter. In simulations, the 2-D-window-based approach shows an effect in the axial direction similar to the 2-D prediction. In simulations and experiments, increasing the window size in the lateral direction shows an increase in the maximum SNRe of the lateral shear strain filter. Increasing the lateral overlap has no effect on the estimation of lateral shear strain. These results were confirmed in the tissue-mimicking phantom experiments. When compared with the 2-D lateral shear strain filter, the results obtained with the 2-D-window-based approach showed an enhanced performance by incorporating the lateral window size in the lateral shear strain estimation, which was consistent with the proposed theory.

Enhancing the performance of lateral shear strain estimation by using 2-D strain imaging

Radio-frequency (RF) ultrasound can be used to estimate deformation of biological tissue. Decorrelation of sequentially acquired ultrasound signals resulting from the deformation imposes a limitation on the precision (elastographic signal-to-noise ratio; SNRe) of estimating these deformations; this is presented as the lateral shear strain filter. In this paper, we explore the effect of a 2-D-window-based strain estimation approach on the lateral shear strain filter and propose an extension of the 1-D theoretical lateral shear strain filter to 2-D. We compared the performance of the 2-D approach in simulated ultrasound data and a tissue-mimicking phantom with that of the 2-D lateral shear strain filter. In simulations, the 2-D-window-based approach shows an effect in the axial direction similar to the 2-D prediction. In simulations and experiments, increasing the window size in the lateral direction shows an increase in the maximum SNRe of the lateral shear strain filter. Increasing the lateral overlap has no effect on the estimation of lateral shear strain. These results were confirmed in the tissue-mimicking phantom experiments. When compared with the 2-D lateral shear strain filter, the results obtained with the 2-D-window-based approach showed an enhanced performance by incorporating the lateral window size in the lateral shear strain estimation, which was consistent with the proposed theory.

Nonrigid PET motion compensation in the lower abdomen using simultaneous tagged-MRI and PET imaging

We propose a novel approach for PET respiratory motion correction using tagged-MRI and simultaneous PET-MRI acquisitions. We use a tagged-MRI acquisition followed by motion tracking in the phase domain to estimate the nonrigid deformation of biological tissues during breathing. In order to accurately estimate motion even in the presence of noise and susceptibility artifacts, we regularize the traditional HARP tracking strategy using a quadratic roughness penalty on neighboring displacement vectors (R-HARP). We then incorporate the motion fields estimated with R-HARP in the system matrix of an MLEM PET reconstruction algorithm formulated both for sinogram and list-mode data representations. This approach allows reconstruction of all detected coincidences in a single image while modeling the effect of motion both in the emission and the attenuation maps. At present, tagged-MRI does not allow estimation of motion in the lungs and our approach is therefore limited to motion correction in soft tissues. Since it is difficult to assess the accuracy of motion correction approaches in vivo, we evaluated the proposed approach in numerical simulations of simultaneous PET-MRI acquisitions using the NCAT phantom. We also assessed its practical feasibility in PET-MRI acquisitions of a small deformable phantom that mimics the complex deformation pattern of a lung that we imaged on a combined PET-MRI brain scanner. Simulations showed that the R-HARP tracking strategy accurately estimated realistic respiratory motion fields for different levels of noise in the tagged-MRI simulation. In simulations of tumors exhibiting increased uptake, contrast estimation was 20% more accurate with motion correction than without. Signal-to-noise ratio (SNR) was more than 100% greater when performing motion-corrected reconstruction which included all counts, compared to when reconstructing only coincidences detected in the first of eight gated frames. These results were confirmed in our proof-of-principle PET-MRI acquisitions, indicating that our motion correction strategy is accurate, practically feasible, and is therefore ready to be tested in vivo. This work shows that PET motion correction using motion fields measured with tagged-MRI in simultaneous PET-MRI acquisitions can be made practical for clinical application and that doing so has the potential to remove motion blur in whole-body PET studies of the torso.