Model Of Biological Tissue Research Articles

Effect of the Combination of Different Electrode Spacings and Power on Bipolar Radiofrequency Fat Dissolution: A Computational and Experimental Study.

The finite element method was used, and experiments were performed to analyze the effect of different electrode spacings and power combinations on the electrical and thermal aspects of biological tissues during bipolar radiofrequency (RF) fat dissolution. Through these efforts, this study also attempted to develop a reasonable electrode spacing and power combination that can achieve fat dissolution effects,the RF energy of which will not thermally damage the tissue. COMSOL was adopted to conduct a finite element analysis for bio-thermoelectric coupling, and a two-dimensional time-domain model of biological tissue was built. A self-developed single-channel bipolar RF device was employed to load RF energy on the ex vivo porcine abdominal tissue. The thermal characteristics of the tissue were characterized and analyzed with athermal imager and thermocouple probes. Under a power of 5 W combined with the electrode spacings of 1, 2, and 3 cm, the temperature in the tissue could not reach that required for fat dissolution. Under a power of 15 W combined with the electrode spacings of 1, 2, and 3 cm, the RF energy would thermally damage part of the skin areas. Besides this, the combination of apower of 10 W and the electrode spacing of 1 cm would thermally damage the skin areas. The combination of apower of 10 W and the electrode spacing of 2 or 3 cm made part of the fat layer of the tissue satisfy the requirements of fat dissolution, and the fat dissolution area caused by the former was 118% larger than that of the latter; in the meantime, no heat damage to the skin layer was found. Different electrode spacings and power combinations significantly affect the electrical and thermal properties of bipolar RF energy loaded on biological tissue, a reasonable electrode spacing and power combination is one of the critical factors leading to the success of bipolar RF fat dissolution. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

Development of a 3D Anthropomorphic Phantom Generator for Microwave Imaging Applications of the Head and Neck Region.

The development of 3D anthropomorphic head and neck phantoms is of crucial and timely importance to explore novel imaging techniques, such as radar-based MicroWave Imaging (MWI), which have the potential to accurately diagnose Cervical Lymph Nodes (CLNs) in a neoadjuvant and non-invasive manner. We are motivated by a significant diagnostic blind-spot regarding mass screening of LNs in the case of head and neck cancer. The timely detection and selective removal of metastatic CLNs will prevent tumor cells from entering the lymphatic and blood systems and metastasizing to other body regions. The present paper describes the developed phantom generator which allows the anthropomorphic modelling of the main biological tissues of the cervical region, including CLNs, as well as their dielectric properties, for a frequency range from 1 to 10 GHz, based on Magnetic Resonance images. The resulting phantoms of varying complexity are well-suited to contribute to all stages of the development of a radar-based MWI device capable of detecting CLNs. Simpler models are essential since complexity could hinder the initial development stages of MWI devices. Besides, the diversity of anthropomorphic phantoms resulting from the developed phantom generator can be explored in other scientific contexts and may be useful to other medical imaging modalities.

CLASSIFICATION OF MULTIDIMENSIONAL POLARIZATION MICROSCOPY RESULTS IN THE TECHNOLOGY OF FORENSIC INTELLECTUAL MONITORING OF HEART DISEASES

The work combines methods of multidimensional polarization microscopy, statistical processing of data and inductive modeling with the purpose of constructing a methodology for creation of intelligent systems for multi-level forensic medical monitoring based on the example of the post-mortem diagnosis of coronary heart disease and acute coronary insufficiency. The task of classifying the results of the study of biological materials for obtaining a diagnosis was solved. To obtain informative features, a model of biological tissue of the myocardium was developed and the main diagnostic parameters were determined (statistical moments of 1–4 orders of coordinate distributions of the values of azimuths and the ellipticity of polarization and their autocorrelation functions, as well as wavelet coefficients of the corresponding distributions), which are dynamic due to its necrotic changes. The classification of these data was provided by constructing a deciding rule in the multi – raw algorithm of the GMDH. The effectiveness of the described methodology has been experimentally proved.

An experimental study of nonlinear rate-dependent behaviour of skeletal muscle to obtain passive mechanical properties.

Accurate modelling of biological tissues has been a significant need for analysis of the human body. In this article, a comprehensive in vitro experimental study has been done on the fresh bovine skeletal muscle before the onset of rigour mortis in order to provide an experimental description of passive skeletal muscle properties in three dimensions. Different situations including various deformation modes, different loading rates and loading directions are tested to consider all features of skeletal muscle behaviour. Based on the nonlinear continuum mechanics, a three-dimensional visco-hyperelastic model is introduced which considers all aspects of skeletal muscle's features such as nonlinear hyperelastic, time-dependent behaviour, anisotropy and quasi-incompressibility. Visco-hyperelastic material constants are obtained for passive behaviour of the muscle based on genetic algorithm optimization method via comparing the theoretical and experimental results. Experiments show that the rate of loading affects the configuration of experimental curves considerably. It could be also concluded that compression-tension asymmetry, as well as anisotropic behaviour, of the muscle is due to fibres orientation. Obtained experimental results help to achieve a better understanding of mechanical properties and nonlinear behaviour of the skeletal muscles.

Sensibility analysis of the electrical impedance parameters by the Monte Carlo method

Electrical properties of biological tissues are used to analyze its state in different practical applications, e.g., assessing the risk of cancer. The modeling of electrical properties usually is performed by circuital models or semiempirical models as Cole-Cole. Still, another option is available, the application of the generalized effective medium theory of induced polarization. In the framework of the effective medium theory, we proposed a model for biological tissues which we called MOPET. This model links physiological parameters of tissues with their electrical properties. However, it has a higher number of parameters than the Cole-Cole and circuital models. This large number of parameters is a limitation for the use of effective medium theory to describe the electrical properties of tissue and also suggests that some of these parameters have negligible effects. We used a Monte Carlo simulation to study the effect of each MOPET parameter on the electrical impedance spectra, where uniform random variables were used to simulate the variability of the parameters of this model. We found that the heterogeneity coefficient is the most sensible parameter, i.e., a variation above 1% in this parameter alters enormously the impedance spectra.

A complementary energy approach accommodates scale differences in soft tissues

The mechanics of biological entities, from single molecules to the whole organ, has been extensively analyzed during the last decades. At the smaller scales, statistical mechanics has fostered successful physical models of proteins and molecules, which have been later incorporated within constitutive models of rubber-like materials and biological tissues. At the macroscopic scale, the additive decomposition of energy functions i.e., a parallel arrangement of the tissue constituent, has been recurrently used to account for the internal heterogeneity of soft biological materials. However, it has not yet been possible to unite the mechanics at the tissue level with the actual response of the tissue components. Here, we exemplify our approach using cardiovascular tissue where the mechanical response at the tissue scale is in the range of kPa whereas the elastic modulus of collagen, the main component of the vascular tissue, is in the range of MPa GPa. In this work we develop a novel theoretical framework based on a complementary strain energy function that builds-up on a full network model. The complementary strain energy function introduces naturally an additive decomposition of the deformation gradient for the tissue constituents, i.e an arrangement in series of the constituents. We demonstrate that the macroscopic response of the tissue can be reproduced by just introducing the underlying mechanical and structural features of the micro-constituents, improving in a fundamental manner previous attempts in the mechanical characterization of soft biological tissues. The proposed theoretical framework unveils a new direction in the mechanical modeling of soft tissues and biological networks.

Bioreactor With Electrically Deformable Curved Membranes for Mechanical Stimulation of Cell Cultures

Physiologically relevant in vitro models of stretchable biological tissues, such as muscle, lung, cardiac and gastro-intestinal tissues, should mimic the mechanical cues which cells are exposed to in their dynamic microenvironment in vivo. In particular, in order to mimic the mechanical stimulation of tissues in a physiologically relevant manner, cell stretching is often desirable on surfaces with dynamically controllable curvature. Here, we present a device that can deform cell culture membranes without the current need for external pneumatic/fluidic or electrical motors, which typically make the systems bulky and difficult to operate. We describe a modular device that uses elastomeric membranes, which can intrinsically be deformed by electrical means, producing a dynamically tuneable curvature. This approach leads to compact, self-contained, lightweight and versatile bioreactors, not requiring any additional mechanical equipment. This was obtained via a special type of dielectric elastomer actuator. The structure, operation and performance of early prototypes are described, showing preliminary evidence on their ability to induce changes on the spatial arrangement of the cytoskeleton of fibroblasts dynamically stretched for 8 h.

A finite element for soft tissue deformation based on the absolute nodal coordinate formulation

This paper introduces an implementation of the absolute nodal coordinate formulation (ANCF) that can be used to model fibrous soft tissue in cases of three-dimensional elasticity. It is validated against results from existing incompressible material models. The numerical results for large deformations based on this new ANCF element are compared to results from analytical and commercial software solutions, and the relevance of the implementation to the modeling of biological tissues is discussed. Also considered is how these results relate to the classical results seen in Treloar’s rubber experiments. All the models investigated are considered from both elastic and static points of view. For isotropic cases, neo-Hookean and Mooney–Rivlin models are examined. For the anisotropic case, the Gasser–Ogden–Holzapfel model, including a fiber dispersion variation, is considered. The results produced by the subject ANCF models agreed with results obtained from the commercial software. For the isotropic cases, in fact, the numerical solutions based on the ANCF element were more accurate than those produced by ANSYS.

Linear and nonlinear mechanical responses can be quite different in models for biological tissues.

The fluidity of biological tissues - whether cells can change neighbors and rearrange - is important for their function. In traditional materials, researchers have used linear response functions, such as the shear modulus, to accurately predict whether a material will behave as a fluid. Similarly, in disordered 2D vertex models for confluent biological tissues, the shear modulus becomes zero precisely when the cells can change neighbors and the tissue fluidizes, at a critical value of control parameter s0* = 3.81. However, the ordered ground states of 2D vertex models become linearly unstable at a lower value of control parameter (3.72), suggesting that there may be a decoupling between linear and nonlinear response. We demonstrate that the linear response does not correctly predict the nonlinear behavior in these systems: when the control parameter is between 3.72 and 3.81, cells cannot freely change neighbors even though the shear modulus is zero. These results highlight that the linear response of vertex models should not be expected to generically predict their rheology. We develop a simple geometric ansatz that correctly predicts the nonlinear response, which may serve as a framework for making nonlinear predictions in other vertex-like models.

Hyperuniformity and density fluctuations at a rigidity transition in a model of biological tissues.

The suppression of density fluctuations at different length scales is the hallmark of hyperuniformity. Here, we explore the presence of this hidden order in a manybody interacting model of biological tissue, known to exhibit a transition, or sharp crossover, from a solid to a fluid like phase. We show that the density fluctuations in the rigid phase are only suppressed up to a finite lengthscale. This length scale monotonically increases and grows rapidly as we approach the fluid phase reminiscent to divergent behavior at a critical point, such that the system is effectively hyperuniform in the fluid phase. Furthermore, complementary behavior of the structure factor across the critical point also indicates that hyperuniformity found in the fluid phase is stealthy.

Применение люминесценции апконверсионных наночастиц NaYF-=SUB=-4-=/SUB=- : Yb,Er для исследования динамики коагуляции белков

A method to measure the dynamics of the internal temperature of biological tissues and the thickness of the denatured layer during laser thermolysis is presented. The method is based on intensity measurements of three luminescence bands of upconversion NaYF4: Yb, Er nanoparticles in the green and red parts of the visible spectrum. Ovalbumine is used as a model biological tissue. The general patterns of denaturation of ovalbumine is also studied by the method of plasmon resonance photothermotherapy.

Hexatic phase in a model of active biological tissues.

In many biological processes, such as wound healing, cell tissues undergo an epithelial-to-mesenchymal transition, which is a transition from a more rigid to a more fluid state. Here, we investigate the solid/fluid transition of cell tissues within the framework of the self-propelled Voronoi model, which accounts for the deformability of the cells, for their many-body interactions, and for their polarized motility. The transition is controlled by two parameters, respectively accounting for the strength of the self-propelling force of the cells, and for the mechanical rigidity of the cells. We find the melting transition to occur via a continuous solid-hexatic transition followed by a continuous hexatic-liquid transition, as in the Kosterlitz, Thouless, Halperin, Nelson, and Young scenario. This finding indicates that the hexatic phase may have an unexpected biological relevance.

Экспериментальное обоснование выбора режима лазерного излучения с длиной волны 980 нм для рассечения рубцов верхних дыхательных путей

The aim of our work was the experimental development of the optimal laser radiation regime (laser wavelength 980 nm) for dissecting scars of the upper respiratory tract in terms of lateral thermal damage to surrounding tissues. Thermal damage is of fundamental importance when exposed to scar tissue, since it leads to inflammation in the dissection zone, which increases the risk of restenosis. The study was conducted on the basis of the Chair of Otorhinolaryngology with a clinic of Pavlov First Saint Petersburg State Medical University. A pork tendon was chosen as a model of biological tissue due to the similar optical and mechanical properties of scar tissue. The incision was made in the continuous contact mode at a power of 7 W and in the contact pulse mode at a power of 15 W (pulse – 20 ms, pause – 60 ms). The impact on the tissue in these modes was carried out in two directions: from the proximal edge of the tendon to the distal and vice versa. The measurement of the width of the ablation and coagulation zones was carried out under microscopic conditions using an eyepiece micrometer with an increase of ×40. The average width of the zone of lateral tissue damage when exposed in the contact pulse mode in the distal direction is 355±19 nm, which is comparable with the results of a CO2-laser in the superpulse mode. Keywords: diode laser, laryngeal cicatricial stenosis model.

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.

Wristwatch-Style Wearable Dielectric Resonator Antennas for Applications on Limps

A wristwatch-style wearable dielectric resonator antenna (DRA) is proposed for the 2.45-GHz ISM band and sub-6 GHz 5G NR bands around 2.5 GHz, such as the commercial band for China Mobile Communications Corporation. The antenna is designed for applications on forearms and ankles. Practical concerns, including the aligning method, platform size, specific absorption rate, and user effects are investigated. Coplanar feeding structure is applied for alignment and isolation. Analysis of the watchband-like substrate is highlighted to avoid performance degradation. Given that platform configurations are not discretionary in actual devices, parasitic loading is introduced to attain desirable substrate effects and suppress unwanted ones. The user-device interplay is studied in light of actual application scenarios. The specific absorption rate is calculated through multilayer biological tissue models. Meanwhile, radiation variation caused by users is estimated based on human phantom models and measurements.

Three-dimensional spatial reconstruction of the gunshot injuries in the practice of forensic medicine

During the recent years the number of the wounded and killed due to firearms use both in Ukraine and in the majority of the world countries has increased. Therefore, examination of gunshot injuries is rather topical issue now in forensic medicine, and it is a considerable comprehensive question.Transience of incidences with the use of firearms in the majority of cases does not enable to find a real picture of circumstances when these incidences occur. Therefore, the issues of traumatic factor identification in these cases, especially with perforating and tangential injuries, are very important in forensic medicine, but remain elucidated insufficiently.
 At the same time, a dynamic development of upto-date computer technologies enables to increase the level of visualization, forensic diagnostics of injuries and substantiation of expert conclusions in case of gunshot injuries.
 Purpose of the study. To study diagnostic possibilities of three-dimensional spatial reconstruction method for forensic identification of the main traumatic factor in case of gunshot injuries.
 Materials and methods. Ballistic plasticine and gel, fragments of pig skin with subcutaneous fat, fragments of biological tissues with gunshot injuries were used as the material for the study. The obtained experimental gunshot injuries (45 cases) and cases of injuries from the expert practice (30 cases) were subjected to photogrammetric with possibility to obtain a three-dimensional spatial model of every injury by means of the computer program Agisoft Photoscan.
 Results. The studies conducted differ from the existing ones by their novelty, higher inventive and scientific-practical level. Three-dimensional spatial digital models of the injured biological tissues and their imitators will be designed, examined and analyzed for the first time, and the diagnostic criteria for forensic identification of the main traumatic factor of gunshot body injuries will be developed. The obtained textured models of gunshot injuries in «Obj» format can be imported into the program 3dsMax, which enables to examine linear sizes of every fragment of a wound canal with higher accuracy (to 0,001 cm) in comparison with classical methods of examination.
 The results obtained while conducting the study enable not only to develop computer threedimensional digital models of gunshot body injuries, but examine their character and morphologic peculiarities in forensic practice on an up-to-date scientific level. All the mentioned above enables to formulate and substantiate new, more accurate forensic diagnostic identification criteria of the main traumatic factor of gunshot body injuries.
 Conclusion. Introduction of up-to date computer technologies into the practice of forensic medicine will enable to determine identifying peculiarities of the main traumatic factor in case of gunshot injuries with a higher accuracy.

A Computational Model for Biological Tissues Considering the Influence of Injury on Growth and Remodelling

AbstractBiological tissues adapt to changed loading conditions through growth and remodelling (G&R) to reestablish a so‐called homeostatic state. On the other hand, loading conditions above their physiological limits, as during trauma or surgical procedures, cause injury and can initiate pathological G&R. Herein, a modelling approach for G&R influenced by injury is presented combining the theories of plasticity and homogenised constrained mixtures. The results show that injury has a significant impact on the G&R behaviour and thus on the accomplishment of homeostasis.

Enhanced catalyst performance through compartmentalization exemplified by colloidal l-proline modified microgel catalysts

Exploring and controlling chemical reactions in compartments opens new platforms for designing bioinspired catalysts and energy-autonomous systems. Aqueous polymer networks or hydrogels serve as a perfect model for biological tissues, allowing systematic investigations of chemical transformations in compartments. Herein, we report the synthesis of a versatile, colloidal microgel catalyst containing covalently bound l-proline as an organocatalyst. The key finding of our work is that the catalytic activity can be tuned by adjusting the distribution of the organocatalyst in the microgel network as well as the properties of the solvent. We demonstrate that l-proline groups integrated into microgels enable the reaction of 4-nitrobenzaldehyde and cyclohexanone in a heterogeneous reaction mixture in which free l-proline is not active. By controlling the localization of the l-proline groups within the microgel network (core or corona), the rate of the aldol reaction in homogenous and heterogeneous reaction mixtures can be modulated. Furthermore, microgels with covalently attached catalysts can be recycled and reused in sequential catalytic runs without deterioration of the catalyst performance in terms of activity and selectivity. The internal structure of the microgel in heterogeneous reaction mixtures was studied by computer simulations.

FDM-based 2D Numerical Study of Hyperthermia Cancer Treatment by Micro/Nano-Phase-Change Materials

Hyperthermia is one of the methods for cancer therapies by creating artificial fever. Protection of healthy tissues around the tumor tissue, which has a high temperature, is one of the major issues in this treatment. In present study, the two-dimensional transient model of biological tissue with a tumor is taken into account. The area of the tumor is embedded with micro/nano superparamagnetic materials, and the surrounding healthy tissues are embedded with microcapsules of micro/nano-phase-change materials (PCMs). The effect of concentrations, the radius of the microcapsule, the melting temperature and latent heat of phase-change nanoparticles and also superparamagnetic nanoparticles on thermal protection were examined numerically by using the finite difference method. The results showed that the use of PCMs causes sensible decreases in temperatures of the healthy tissue around the cancerous cells (in some places up to 3 ℃) that leads to treatment complications reduction. If the protection of healthy tissues is well done, it is possible to raise the temperature of the cancerous tissue to achieve more favorable treatment.

Investigation of thermal wave propagation within the model of biological tissue and the possibility of thermal imaging of vasomotor activity of peripheral vessels

Presently, investigation of relationships between biomechanical processes of regulation of the lumen of peripheral vessels, blood flow dynamics and changes in skin temperature with the aim of imaging of hemodynamic dysfunction is an actual problem of biomedical engineering and diagnostics. Experimental dependences of the velocity and damping of a periodic thermal perturbation in pig skin as a model of human skin have been established in this work. The solution of the heat equation in the case of periodic heating has been used to describe the propagation of thermal perturbation (heat waves) in a human skin model. Assuming proportional changes in the volume blood flow and temperature in the depth of the skin, this will allow restoring the signal of blood flow dynamics based on data of skin surface temperature variation. The latter experimentally justifies the possibility of thermal imaging of the processes of regulation of the vascular lumen of peripheral vessels during the diagnostics and therapy of vascular complications.