Model Of Biological Tissue Research Articles

Investigation of Epidermal Loop Antennas for Biotelemetry IoT Applications

The Quadruple Loop (QL) antenna was designed and investigated to deliver a robust body-worn antenna for bio-medical applications. The QL antenna is a very thin single-layer groundless structure which allows for the installation of neighboring electronics and sensors which need to be extremely close to the epidermis layer. The performance of the proposed antennas was investigated for three main standards: GSM-900, GSM-1800, and Bluetooth low energy (BLE). Radiation pattern measurements were conducted to compare their results with their simulation counterparts. Moreover, data communication tests showed that the acquired BER readings could qualify the BLE and GSM-900 antennas to work as part of 4-QAM wireless links. Besides these hands-on endeavors, an equivalent and more efficient mathematical model of biological tissues which make up the human arm was computed. The equivalent model was tested in software and has the practical potential to be realized in physical phantom making.

No unjamming transition in a Voronoi model of biological tissue.

Vertex models are a popular approach to simulating the mechanical and dynamical properties of dense biological tissues, describing the tissue as a network of polygons. Recently a class of two-dimensional vertex models was shown to exhibit a disordered rigidity transition controlled by the preferred cellular geometry, which was subsequently echoed by experimental findings. An attractive variant of these models uses a Voronoi tessellation to describe the cells, which reduces the number of degrees of freedom as compared the original vertex model. The Voronoi model was also endowed with a non-equilibrium model of cellular motility, leading to rich, glassy behavior. This glassy behavior was suggested to be inextricably linked to an underlying jamming transition. We test this conjecture, exploring the low-effective-temperature limit of the 2D Voronoi model by studying cell trajectories from detailed dynamical simulations in combination with rigidity measurements of energy-minimized disordered cell configurations. We find that the zero-temperature limit of this model has no unjamming transition. We show that this absence of an unjamming transition is intimately linked to the marginality of the model, i.e. the fact that the constraints imposed on cell areas and perimeters precisely balance the number of degrees of freedom in the model. Our work suggests that constraint counting arguments are useful to understand rigidity in a broad class of models of dense biological tissues.

First use of electron swarm technique on THF informs refinement of interaction cross-sections

The first experimental transport coefficients for electrons in gaseous THF make headway in defining previously unknown cross-sections, highlighting opportunities in biological tissue modeling.

Prostate Cancer Detection with a Tactile Resonance Sensor-Measurement Considerations and Clinical Setup.

Tumors in the human prostate are usually stiffer compared to surrounding non-malignant glandular tissue, and tactile resonance sensors measuring stiffness can be used to detect prostate cancer. To explore this further, we used a tactile resonance sensor system combined with a rotatable sample holder where whole surgically removed prostates could be attached to detect tumors on, and beneath, the surface ex vivo. Model studies on tissue phantoms made of silicone and porcine tissue were performed. Finally, two resected human prostate glands were studied. Embedded stiff silicone inclusions placed 4 mm under the surface could be detected in both the silicone and biological tissue models, with a sensor indentation of 0.6 mm. Areas with different amounts of prostate cancer (PCa) could be distinguished from normal tissue (p < 0.05), when the tumor was located in the anterior part, whereas small tumors located in the dorsal aspect were undetected. The study indicates that PCa may be detected in a whole resected prostate with an uneven surface and through its capsule. This is promising for the development of a clinically useful instrument to detect prostate cancer during surgery.

Oral Mucosa Model for Electrochemotherapy Treatment of Dog Mouth Cancer: Ex Vivo, In Silico, and In Vivo Experiments.

Electrochemotherapy (EQT) is a local cancer treatment well established to cutaneous and subcutaneous tumors. Electric fields are applied to biological tissue in order to improve membrane permeability for cytotoxic drugs. This phenomenon is called electroporation or electropermeabilization. Studies have reported that tissue conductivity is electric field dependent. Electroporation numerical models of biological tissues are essential in treatment planning. Tumors of the mouth are very common in dogs. Inadequate EQT treatment of oral tumor may be caused by significant anatomic variations between dogs and tumor position. Numerical models of oral mucosa and tumor allow the treatment planning and optimization of electrodes for each patient. In this work, oral mucosa conductivity during electroporation was characterized by measuring applied voltage and current of ex vivo rats. This electroporation model was used with a spontaneous canine oral melanoma. The model outcomes of oral tumor EQT is applied in different parts of the oral cavity including near bones and the hard palate. The numerical modeling for treatment planning will help the development of new electrodes and increase the EQT effectiveness.

Research on adaptive quasi-linear viscoelastic model for nonlinear viscoelastic properties of in vivo soft tissues

The mechanical behavior modeling of human soft biological tissues is a key issue for a large number of medical applications, such as surgery simulation, surgery planning, diagnosis, etc. To develop a biomechanical model of human soft tissues under large deformation for surgery simulation, the adaptive quasi-linear viscoelastic (AQLV) model was proposed and applied in human forearm soft tissues by indentation tests. An incremental ramp-and-hold test was carried out to calibrate the model parameters. To verify the predictive ability of the AQLV model, the incremental ramp-and-hold test, a single large amplitude ramp-and-hold test and a sinusoidal cyclic test at large strain amplitude were adopted in this study. Results showed that the AQLV model could predict the test results under the three kinds of load conditions. It is concluded that the AQLV model is feasible to describe the nonlinear viscoelastic properties of in vivo soft tissues under large deformation. It is promising that this model can be selected as one of the soft tissues models in the software design for surgery simulation or diagnosis.

Improvement of the model of temperature distribution and registration of native radiation of biological objects

Temperature is a reliable indicator of most physiological pathologies, since they are accompanied by disturbance of temperature balance. Non-invasive control of deep temperatures makes it possible to increase the efficiency of diagnosis. One of the promising methods of non-invasive measurement of deep temperatures is the method of radiothermometry, based on measuring the power of native radiation of the electromagnetic field on the surface of the human body. The model of the temperature distribution in the biological tissue has been improved in the case of a region of lower temperature taking into account the physiological processes of formation of thermal fields. During the analysis of the model, it has been established that at a depth of the temperature anomaly up to 2–3 cm, the temperature spots on the surface of the skin are distinguishable by the methods of infrared thermography. With this in mind, and also taking into account the penetrating power of electromagnetic waves, it is reasonable to choose the operating frequencies of the radiometer to 1.8 GHz. An improved model of temperature distribution makes it possible to estimate the integral temperature of a layer of biological tissue by electromagnetic radiation. It has been shown that it is possible to determine the characteristics of the temperature anomaly region by numerical modeling of the formation of own electromagnetic radiation. The determination of two or more parameters of the temperature anomaly region is possible using a system of two or more equations, which is achieved by measuring the radiation power at different frequencies. A principle possibility of simultaneous determination of several parameters of the temperature anomaly, using a system of equations, has been considered very important. A working mathematical model has been created that makes it possible to solve the inverse problem of finding two parameters of the temperature anomaly with respect to the noise temperature measured at two frequencies. The next step is to study the multilayer model of biological tissue

A family of hyperelastic models for human brain tissue

Experiments on brain samples under multiaxial loading have shown that human brain tissue is both extremely soft when compared to other biological tissues and characterized by a peculiar elastic response under combined shear and compression/tension: there is a significant increase in shear stress with increasing axial compression compared to a moderate increase with increasing axial tension. Recent studies have revealed that many widely used constitutive models for soft biological tissues fail to capture this characteristic response. Here, guided by experiments of human brain tissue, we develop a family of modeling approaches that capture the elasticity of brain tissue under varying simple shear superposed on varying axial stretch by exploiting key observations about the behavior of the nonlinear shear modulus, which can be obtained directly from the experimental data.

Plum pudding random medium model of biological tissue toward remote microscopy from spectroscopic light scattering.

Biological tissue has a complex structure and exhibits rich spectroscopic behavior. There has been no tissue model until now that has been able to account for the observed spectroscopy of tissue light scattering and its anisotropy. Here we present, for the first time, a plum pudding random medium (PPRM) model for biological tissue which succinctly describes tissue as a superposition of distinctive scattering structures (plum) embedded inside a fractal continuous medium of background refractive index fluctuation (pudding). PPRM faithfully reproduces the wavelength dependence of tissue light scattering and attributes the "anomalous" trend in the anisotropy to the plum and the powerlaw dependence of the reduced scattering coefficient to the fractal scattering pudding. Most importantly, PPRM opens up a novel venue of quantifying the tissue architecture and microscopic structures on average from macroscopic probing of the bulk with scattered light alone without tissue excision. We demonstrate this potential by visualizing the fine microscopic structural alterations in breast tissue (adipose, glandular, fibrocystic, fibroadenoma, and ductal carcinoma) deduced from noncontact spectroscopic measurement.

Generation and measurement of shear waves in micellar fluids using ultrasound-based methods

Wormlike micellar fluids are viscoelastic and their mechanical properties have been evaluated with mechanically generated shear waves combined with optical detection as well as rheological testing. In this work, we describe the use of acoustic radiation force and ultrafast ultrasound imaging to generate shear waves and measure their propagation, respectively. This shear wave elastography (SWE) method has been used to measure the viscoelastic mechanical properties in tissue-mimicking phantoms and soft tissues. We tested micellar fluids made from cetrimonium bromide (CTAB) and sodium salicylate (NaSAL) with a 5:3 ratio with different concentrations (100, 200, 300, and 400 mM). We fit an extended Maxwell model to the rheological test data (0.001-15.91Hz) and used the model parameters to calculate the shear wave phase velocity in the range of the SWE data (100-500 Hz). The phase velocities calculated from the rheology testing compared well with the SWE results. The mean absolute error was less than 0.02 m/s for all the micellar fluids tested. The SWE method is nondestructive and can be used for characterization of the viscoelasticity of micellar fluids, which could be used as a model for biological tissues. [This work was supported in part by grant R01DK092255.]

Nonlinear Rheology in a Model Biological Tissue.

The rheological response of dense active matter is a topic of fundamental importance for many processes in nature such as the mechanics of biological tissues. One prominent way to probe mechanical properties of tissues is to study their response to externally applied forces. Using a particle-based model featuring random apoptosis and environment-dependent division rates, we evidence a crossover from linear flow to a shear-thinning regime with an increasing shear rate. To rationalize this nonlinear flow we derive a theoretical mean-field scenario that accounts for the interplay of mechanical and active noise in local stresses. These noises are, respectively, generated by the elastic response of the cell matrix to cell rearrangements and by the internal activity.

Examples of multiscale and multiphysics numerical modeling of biological tissues.

Predictive theoretical-numerical modeling of the behavior and evolution of biological tissue is a difficult task since many of the required knowledge tools (experimental, theoretical and numerical) are still not well understood. We present here some methodologies and results specific to multiscale and multiphysics numerical modeling of biological tissues applied to the predictive behavior of cortical veins depending on their local constituents' microstructure and for bone remodeling and reconstruction as a function of the local mechanobiology. Although further work is required to improve the accuracy of the developed models, the proposed approaches highlight their potential usefulness for understanding the mechanical-biological couplings, short and long term predictions of biological evolutions as well as possible further transfer to medical applications.

Analysis of specific absorption rate and internal electric field in human biological tissues surrounding an air-core coil-type transcutaneous energy transmission transformer.

In this study, we analyzed the internal electric field E and specific absorption rate (SAR) of human biological tissues surrounding an air-core coil transcutaneous energy transmission transformer. Using an electromagnetic simulator, we created a model of human biological tissues consisting of a dry skin, wet skin, fat, muscle, and cortical bone. A primary coil was placed on the surface of the skin, and a secondary coil was located subcutaneously inside the body. The E and SAR values for the model representing a 34-year-old male subject were analyzed using electrical frequencies of 0.3-1.5MHz. The transmitting power was 15W, and the load resistance was 38.4Ω. The results showed that the E values were below the International Commission on Non-ionizing Radiation Protection (ICNIRP) limit for the general public exposure between the frequencies of 0.9 and 1.5MHz, and SAR values were well below the limit prescribed by the ICNIRP for the general public exposure between the frequencies of 0.3 and 1.2MHz.

Specific Absorption Rate Analysis of Aperture Coupled Antenna for Wireless Body Area Network Applications

Objective: This work presents the design and analysis of miniaturized aperture coupled antenna. The proposed antenna is designed to operate at 2.45GHz of Industrial Scientific Medical (ISM) band and intended to use for Wireless Body Area Network Applications (WBAN). Methods/Statistical analysis: The H shaped patch with aperture coupled feeding is incorporated to get symmetrical radiation pattern. By adjusting the dimensions of ground plane notch and feed line the miniaturization and desired operating frequency is achieved. The antenna’s performance is simulated at the vicinity of human arm biological tissue model to measure Specific Absorption Rate (SAR). Findings: The proposed antenna has compact form factor of 0.32λo x 0.3λo x 0.021λo. The electromagnetic numerical simulation software shows the SAR of 2.71 W/Kg. The antenna’s performance in terms of bandwidth, gain, radiation pattern is found invariable in presence of human arm tissue model. Application/Improvements: The result shows the proposed antenna possesses low SAR and small compact form factor which can be applicable for WBAN applications.

Mechanical characterization of biological tissues: Experimental methods based on mathematical modeling

To illustrate a systematic procedure for mechanical characterization or mechanical behavior of biological tissues with a semi-empirical method based on mathematical models. The method is composed of a series of procedures: construction of cell elements on the specimen, image processing, continuum mechanics, hyperelasticity and so on. An element used in the method, which is similar to finite element methods, is defined by placing markers on the specimen. The change of the locations of the element during a motion is monitored to calculate the displacement for stress estimation owing to external impacts or forces. The validity of the method for mechanical characterization or mechanical behavior of biological tissues is shown through material test simulations with mathematical models, resulting in good agreement overall. A general review of mathematical modeling of biological tissues is served and a semi-empirical method, which makes good use of both finite element methods and mathematical models based on the phenomenological modeling technique, is introduced to assess the stress-strain responses of biological tissues subjected mechanical loadings.

Massive Intracellular Biodegradation of Iron Oxide Nanoparticles Evidenced Magnetically at Single-Endosome and Tissue Levels.

Quantitative studies of the long-term fate of iron oxide nanoparticles inside cells, a prerequisite for regenerative medicine applications, are hampered by the lack of suitable biological tissue models and analytical methods. Here, we propose stem-cell spheroids as a tissue model to track intracellular magnetic nanoparticle transformations during long-term tissue maturation. We show that global spheroid magnetism can serve as a fingerprint of the degradation process, and we evidence a near-complete nanoparticle degradation over a month of tissue maturation, as confirmed by electron microscopy. Remarkably, the same massive degradation was measured at the endosome level by single-endosome nanomagnetophoretic tracking in cell-free endosomal extract. Interestingly, this spectacular nanoparticle breakdown barely affected iron homeostasis: only the genes coding for ferritin light chain (iron loading) and ferroportin (iron export) were up-regulated 2-fold by the degradation process. Besides, the magnetic and tissular tools developed here allow screening of the biostability of magnetic nanomaterials, as demonstrated with iron oxide nanocubes and nanodimers. Hence, stem-cell spheroids and purified endosomes are suitable models needed to monitor nanoparticle degradation in conjunction with magnetic, chemical, and biological characterizations at the cellular scale, quantitatively, in the long term, in situ, and in real time.

Viscoelastic Properties of a Hierarchical Model of Soft Biological Tissue: Two-Dimensional and Three-Dimensional Cases

The measuring of viscoelastic response is widely used for revealing information about soft matter and biological tissue noninvasively. This information encodes intrinsic dynamic correlations and depends on relations between macroscopic viscoelasticity and structure at the mesoscopic scale. Here we show numerically that the frequency dependent dynamical shear moduli distinguish between the mesoscopic architectural complexities and sensitive to the Euclidean dimensionality. Our approach enables the explanation of two- and three-dimensional viscoelastic experiments by objectively choosing and modeling the most relevant architectural features such as the concentration of compounds and intra-model hierarchical characteristics of physical parameters. Current work provides a link between the macroscopical effective viscoelastic properties to viscoelastic constants and network geometry on the mesoscale. Besides of this we also pay attention to the analytical properties of generalized susceptibility function of considered constitutive model accounting principles of causality.

A New Deformation Model of Biological Tissue for Surgery Simulation.

A novel meshless deformation model of biological soft tissue, which is mainly based on the radial basis function point interpolation, is presented for interactive simulation applications such as virtual surgery simulators. Compared with conventional mesh models, the proposed model is particularly suitable for simulating large deformation, sucking and cutting tasks since there is no need to maintain grid information. Kelvin viscoelasticity, which represents relaxation, creep, and hysteresis of soft tissue, is integrated into the proposed model, making the simulation much more realistic than many existing meshless models. To verify the validity of the proposed model, a biomechanical test was performed on real-life biological tissue and the results show that the maximum relative error between the forces from the biomechanical test and those obtained from the model is less than 5.8%. The proposed model was also implemented on a neurosurgery simulator, which showed that the deformation of the brain tumor can be simulated in a high degree of accuracy with real-time performance. In particular, the error and distortion from the remeshing process inherited in conventional mesh models when deformation is large are avoided.

Logarithmic rate based elasto-viscoplastic cyclic constitutive model for soft biological tissues

Based on the logarithmic rate and piecewise linearization theory, a thermodynamically consistent elasto-viscoplastic constitutive model is developed in the framework of finite deformations to describe the nonlinear time-dependent biomechanical performances of soft biological tissues, such as nonlinear anisotropic monotonic stress–strain responses, stress relaxation, creep and ratchetting. In the proposed model, the soft biological tissue is assumed as a typical composites consisting of an isotropic matrix and anisotropic fiber aggregation. Accordingly, the free energy function and stress tensor are divided into two parts related to the matrix and fiber aggregation, respectively. The nonlinear biomechanical responses of the tissues are described by the piecewise linearization theory with hypo-elastic relations of fiber aggregation. The evolution equations of viscoplasticity are formulated from the dissipation inequalities by the co-directionality hypotheses. The anisotropy is considered in the hypo-elastic relations and viscoplastic flow rules by introducing some material parameters dependent on the loading direction. Then the capability of the proposed model to describe the nonlinear time-dependent deformation of soft biological tissues is verified by comparing the predictions with the corresponding experimental results of three tissues. It is seen that the predicted monotonic stress–strain responses, stress relaxation, creep and ratchetting of soft biological tissues are in good agreement with the corresponding experimental ones.

A general framework for application of prestrain to computational models of biological materials

It is often important to include prestress in computational models of biological tissues. The prestress can represent residual stresses (stresses that exist after the tissue is excised from the body) or in situ stresses (stresses that exist in vivo, in the absence of loading). A prestressed reference configuration may also be needed when modeling the reference geometry of biological tissues in vivo. This research developed a general framework for representing prestress in finite element models of biological materials. It is assumed that the material is elastic, allowing the prestress to be represented via a prestrain. For prestrain fields that are not compatible with the reference geometry, the computational framework provides an iterative algorithm for updating the prestrain until equilibrium is satisfied. The iterative framework allows for enforcement of two different constraints: elimination of distortion in order to address the incompatibility issue, and enforcing a specified in situ fiber strain field while allowing for distortion. The framework was implemented as a plugin in FEBio (www.febio.org), making it easy to maintain the software and to extend the framework if needed. Several examples illustrate the application and effectiveness of the approach, including the application of in situ strains to ligaments in the Open Knee model (simtk.org/home/openknee). A novel method for recovering the stress-free configuration from the prestrain deformation gradient is also presented. This general purpose theoretical and computational framework for applying prestrain will allow analysts to overcome the challenges in modeling this important aspect of biological tissue mechanics.