Journal articles on the topic 'Blood-vessels Electric properties Mathematical models'
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1
Lv, Yanpeng, Yanfang Zhang, Jianwei Huang, Yunlong Wang, and Boris Rubinsky. "A Study on Nonthermal Irreversible Electroporation of the Thyroid." Technology in Cancer Research & Treatment 18 (January 1, 2019): 153303381987630. http://dx.doi.org/10.1177/1533033819876307.
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Background: Nonthermal irreversible electroporation is a minimally invasive surgery technology that employs high and brief electric fields to ablate undesirable tissues. Nonthermal irreversible electroporation can ablate only cells while preserving intact functional properties of the extracellular structures. Therefore, nonthermal irreversible electroporation can be used to ablate tissues safely near large blood vessels, the esophagus, or nerves. This suggests that it could be used for thyroid ablation abutting the esophagus. This study examines the feasibility of using nonthermal irreversible electroporation for thyroid ablation. Methods: Rats were used to evaluate the effects of nonthermal irreversible electroporation on the thyroid. The procedure entails the delivery of high electric field pulses (1-3 kV/cm, 100 microseconds) between 2 surface electrodes bracing the thyroid. The right lobe was treated with various nonthermal irreversible electroporation pulse sequences, and the left was the control. After 24 hours of the nonthermal irreversible electroporation treatment, the thyroid was examined with hemotoxylin and eosin histological analysis. Mathematical models of electric fields and the Joule heating-induced temperature raise in the thyroid were developed to examine the experimental results. Results: Treatment with nonthermal irreversible electroporation leads to follicular cells damage, associated with cell swelling, inflammatory cell infiltration, and cell ablation. Nonthermal irreversible electroporation spares the trachea structure. Unusually high electric fields, for these types of tissue, 3000 V/cm, are needed for thyroid ablation. The mathematical model suggests that this may be related to the heterogeneous structure of the thyroid-induced distortion of local electric fields. Moreover, most of the tissue does not experience thermal damage inducing temperature elevation. However, the heterogeneous structure of the thyroid may cause local hot spots with the potential for local thermal damage. Conclusion: Nonthermal irreversible electroporation with 3000 V/cm can be used for thyroid ablation. Possible applications are treatment of hyperthyroidism and thyroid cancer. The highly heterogeneous structure of the thyroid distorts the electric fields and temperature distribution in the thyroid must be considered when designing treatment protocols for this tissue type.
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Łebkowski, Andrzej, and Wojciech Koznowski. "Analysis of the Use of Electric and Hybrid Drives on SWATH Ships." Energies 13, no. 24 (December 8, 2020): 6486. http://dx.doi.org/10.3390/en13246486.
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The article presents issues related to the possibility of using electric and hybrid systems to drive Small Waterplane Area Twin Hull (SWATH) vessels. Ships of this type have significantly less sway and heave compared to monohull crafts and catamarans. Thanks to the synergistic combination of the hydrodynamic properties of SWATH hull and electric drive systems, they can be an interesting proposition for use in transport of passengers and offshore wind farms service crews. The paper presents comparative test results of an electric drive system powered by Hybrid Energy Storage System, which are a combination of systems consisting of batteries (BAT), hydrogen fuel cells (FC) and diesel generators (D). For the presented configurations of propulsion systems, mathematical models taking into account the hydrodynamic resistance of the hull of the vessel have been developed and implemented in the Modelica simulation environment. The tests carried out for various configurations of the drive system have shown reduced energy consumption by the DIESEL-ELECTRIC drive system (by approx. 62%), as well as the reduction of harmful greenhouse gas emissions to the atmosphere (by approx. 62%) compared to the conventional DIESEL drive.
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Kuchumov, A. G., M. R. Kamaltdinov, A. R. Khairulin, M. V. Kochergin, and M. I. Shmurak. "Patient-specific 0D–3D modeling of blood flow in newborns to predict risks of complications after surgery." Health Risk Analysis, no. 4 (December 2022): 159–67. http://dx.doi.org/10.21668/health.risk/2022.4.15.
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Abnormal developments of the cardiovascular system are common congenital malformations. Computational fluid dynamics and mathematical modeling can be used to perform quantitative predictive assessments of hemodynamic properties in varied conditions. This article addresses the development of a coupled 0D–3D model of blood flow in newborns to predict risks of complications after surgery. The 0D-model of systemic circulations is created by using the analogy between the blood flow in vessels and the flow of current through an electric circuit. A shunted section of the aorta and pulmonary artery is replaced with a 3D-model with two-way fluid-solid interaction (FSI).A section in a vessel with the aortic valve is examined in a separate 3D-model. Three-dimensional geometry is based on real CT-scans of a patient. The algorithm for coupling models of different levels relies on meeting the condition that pressures and volumetric blood flows are equal at the interaction boundary. We have developed an algorithm for identifying personal parameters from the results obtained by solving an optimization problem. Computational experiments with different individual geometry of the aorta and aortic valve made it possible to analyze blood flow velocities, near-wall stresses, flows, and valve deformations. Observable near-wall stresses can be considered risk factors that could cause calcification on valve leaflets and other valve diseases. Computational solutions in the “aorta – shunt – pulmonary artery” 3D-system allowed obtaining spatial distributions of velocities, pressures, near-wall stresses and other parameters that are significant in respect to probable pathology development. The developed approaches are primarily relevant for decision-making in surgical practice to predict risks of postoperative complications. In future, our plans are to develop the model so that it covers also saturation and oxygen exchange. This is necessary for assessing whether oxygen supply to the lungs is adequate.
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Antonova, N. M., V. K. Paskova, and I. V. Velcheva. "Blood rheological and electrical properties and relationships with the microvascular tone regulation in patients with diabetes mellitus type 2." Regional blood circulation and microcirculation 20, no. 1 (March 22, 2021): 25–33. http://dx.doi.org/10.24884/1682-6655-2021-20-1-25-33.
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Aim. The study aims to evaluate impairment of the rheological and electrical properties of blood, plasma viscosity and blood conductivity in patients with type 2 diabetes mellitus (T2DM) in comparison with the data of the control group of healthy individuals. It also aims to investigate the changes of the skin blood flow responses to cold stress in T2DM patients through wavelet analysis of the peripheral skin temperature pulsations and to estimate their relationships with the blood viscosity and blood conductivity parameters, obtained from the simulation of experimental data with mathematical equations.Materials and methods. The whole blood viscosity was measured by Contraves LS30 viscometer (Switzerland) at a steady flow in 9 healthy individuals and in 13 patients with type 2 diabetes mellitus. Time variation of whole blood conductivity σ under transient flow at rectangular and trapezium shaped Couette viscometric flow and under electric field of 2 kHz was determined. The amplitudes of the skin temperature pulsations (ASTP) were monitored by «Microtest» device («FM-Diagnostics», Russia). To analyze the temperature fluctuations, wavelet transformation analysis of the low amplitude oscillations of skin temperature in accordance with myogenic (0.05–0.14 Hz), neurogenic (0.02–0.05 Hz), and endothelial (0.0095–0.02 Hz) control mechanisms of the vascular tone (WAST method) was applied.Results. Blood viscosity was increased in the T2DM patients’ group, while blood conductivity decreased in comparison to controls. Two sigmoidal equations were applied to describe the kinetics of blood conductivity. Both models include conductivity indices (σ1 , σ2 , σ3 ) and time indices too. The Pearson correlations between these parameters and the ASTP in the frequency ranges, corresponding to the myogenic, neurogenic and endothelial mechanisms of the microcirculation tone regulation were analyzed. The correlation analysis revealed good ASTP–(σ1 , σ2 , σ3 ) relationships in the neurogenic range 3 minutes after the cold test, while the ASTP–(σ1 , σ2 , σ3 ) correlation in the myogenic frequency range before the cold test was negative (r<–0.8, p<0.5).Conclusion. The results complement the studies of the microvascular regulatory mechanisms and endothelial dysfunction in patients with type 2 diabetes mellitus, as well as their relationships with the rheological and electrical properties of blood.
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Bali, Rekha, Bhawini Prasad, and Swati Mishra. "A REVIEW ON MATHEMATICAL MODELS FOR NANOPARTICLE DELIVERY IN THE BLOOD." International Journal of Advanced Research 10, no. 04 (April 30, 2022): 130–46. http://dx.doi.org/10.21474/ijar01/14526.
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One of the ubiquitous causes of deaths are the Cardio Vascular Diseases or CVDs. The implementation of nanotechnology in the treatment of CVDs has evinced better bio-compatibility and enhanced cell interactions. This provides a strong potential for their mathematical modeling with the diseased blood vessels. In our current study we have reported various mathematical models used for the treatment of CVDs employing nanotechnology. Mathematical modeling provides a tool to comprehend the type, shape and size of the nanoparticles that can be employed as possible drug delivery systems. Mathematical models help to predict how nano-drugs have many improvements like expanded drug loading capacity and programmable pharmo-kinetic properties over the conventional drugs. The amalgamation of mathematical models with clinical data provides for designing these optimal therapies. This review encapsulates the current state of mathematical modeling approaches to treat CVDs using nanoparticle targeted drug delivery.
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Bali, Rekha, Bhawini Prasad, and Swati Mishra. "A REVIEW ON MATHEMATICAL MODELS FOR NANOPARTICLE DELIVERY IN THE BLOOD." International Journal of Advanced Research 10, no. 04 (April 30, 2022): 130–46. http://dx.doi.org/10.21474/ijar01/14526.
Full textAbstract:
One of the ubiquitous causes of deaths are the Cardio Vascular Diseases or CVDs. The implementation of nanotechnology in the treatment of CVDs has evinced better bio-compatibility and enhanced cell interactions. This provides a strong potential for their mathematical modeling with the diseased blood vessels. In our current study we have reported various mathematical models used for the treatment of CVDs employing nanotechnology. Mathematical modeling provides a tool to comprehend the type, shape and size of the nanoparticles that can be employed as possible drug delivery systems. Mathematical models help to predict how nano-drugs have many improvements like expanded drug loading capacity and programmable pharmo-kinetic properties over the conventional drugs. The amalgamation of mathematical models with clinical data provides for designing these optimal therapies. This review encapsulates the current state of mathematical modeling approaches to treat CVDs using nanoparticle targeted drug delivery.
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HERRERO, MIGUEL Á., ÁLVARO KÖHN, and JOSÉ M. PÉREZ-POMARES. "MODELLING VASCULAR MORPHOGENESIS: CURRENT VIEWS ON BLOOD VESSELS DEVELOPMENT." Mathematical Models and Methods in Applied Sciences 19, supp01 (August 2009): 1483–537. http://dx.doi.org/10.1142/s021820250900384x.
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In this work we present a comprehensive account of our current knowledge on vascular morphogenesis, both from a biological and a mathematical point of view. To this end, we first describe the basic steps in the known mechanisms of blood vessel morphogenesis, whose structure, function and unfolding properties are examined. We then provide a wide, although by no means exhaustive, account of mathematical models which are used to describe and discuss particular aspects of the overall biological process considered. We finally summarize the approaches presented, and suggest possible directions for future research. Details about some of the major signalling molecules involved are included in a first Appendix at the end of the paper. A second Appendix provides a brief overview of design principles for vascular nets, a subject that has deserved considerable attention over the years.
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Sánchez-Molina, David, Silvia García-Vilana, Jordi Llumà, Ignasi Galtés, Juan Velázquez-Ameijide, Mari Carmen Rebollo-Soria, and Carlos Arregui-Dalmases. "Mechanical Behavior of Blood Vessels: Elastic and Viscoelastic Contributions." Biology 10, no. 9 (August 26, 2021): 831. http://dx.doi.org/10.3390/biology10090831.
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The mechanical properties of the cerebral bridging veins (CBVs) were studied using advanced microtensile equipment. Detailed high-quality curves were obtained at different strain rates, showing a clearly nonlinear stress–strain response. In addition, the tissue of the CBVs exhibits stress relaxation and a preconditioning effect under cyclic loading, unequivocal indications of viscoelastic behavior. Interestingly, most previous literature that conducts uniaxial tensile tests had not found significant viscoelastic effects in CBVs, but the use of more sensitive tests allowed to observe the viscoelastic effects. For that reason, a careful mathematical analysis is presented, clarifying why in uniaxial tests with moderate strain rates, it is difficult to observe any viscoelastic effect. The analysis provides a theoretical explanation as to why many recent studies that investigated mechanical properties did not find a significant viscoelastic effect, even though in other circumstances, the CBV tissue would clearly exhibit viscoelastic behavior. Finally, this study provides reference values for the usual mechanical properties, as well as calculations of constitutive parameters for nonlinear elastic and viscoelastic models that would allow more accurate numerical simulation of CBVs in Finite Element-based computational models in future works.
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Strigel, R. M., D. J. Schutt, J. G. Webster, D. M. Mahvi, and D. Haemmerich. "An Electrode Array for Limiting Blood Loss During Liver Resection: Optimization via Mathematical Modeling." Open Biomedical Engineering Journal 4, no. 1 (February 4, 2010): 39–46. http://dx.doi.org/10.2174/1874120701004020039.
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Liver resection is the current standard treatment for patients with both primary and metastatic liver cancer. The principal causes of morbidity and mortality after liver resection are related to blood loss (typically between 0.5 and 1 L), especially in cases where transfusion is required. Blood transfusions have been correlated with decreased long-term survival, increased risk of perioperative mortality and complications. The goal of this study was to evaluate different designs of a radiofrequency (RF) electrode array for use during liver resection. The purpose of this electrode array is to coagulate a slice of tissue including large vessels before resecting along that plane, thereby significantly reducing blood loss. Finite Element Method models were created to evaluate monopolar and bipolar power application, needle and blade shaped electrodes, as well as different electrode distances. Electric current density, temperature distribution, and coagulation zone sizes were measured. The best performance was achieved with a design of blade shaped electrodes (5 × 0.1 mm cross section) spaced 1.5 cm apart. The electrodes have power applied in bipolar mode to two adjacent electrodes, then switched sequentially in short intervals between electrode pairs to rapidly heat the tissue slice. This device produces a ~1.5 cm wide coagulation zone, with temperatures over 97 ºC throughout the tissue slice within 3 min, and may facilitate coagulation of large vessels.
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Lee, J., E. P. Salathe, and G. W. Schmid-Schonbein. "Fluid exchange in skeletal muscle with viscoelastic blood vessels." American Journal of Physiology-Heart and Circulatory Physiology 253, no. 6 (December 1, 1987): H1548—H1556. http://dx.doi.org/10.1152/ajpheart.1987.253.6.h1548.
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A mathematical model of capillary-tissue fluid exchange in a viscoelastic blood vessel is presented, and the Landis occlusion experiment is simulated. The model assumes that the fluid exchange is governed by Starling's law and that the protein and red blood cells are conserved in the capillary. Before occlusion, in the steady flow state, the pressure in the capillary decreases from the arterial to venous end due to viscous dissipation. After occlusion a constant pressure is established along the capillary. We assume the capillary to be distensible with viscoelastic wall properties. Immediately following occlusion an instantaneous distension of the capillary occurs. The vessel continues to expand viscoelastically while fluid is filtered for a period of several minutes, until it reaches an equilibrium state. A full numerical solution of the governing equations has been obtained. We use this model to compute the distance variation between two labeled erythrocytes as obtained in the Landis occlusion experiment and compare the results with experimental data obtained recently for the spinotrapezius muscle in our laboratory. The new model can fit the experimental data better than previous models that neglect the distensibility of the capillaries.
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SMITH, NICOLAS, CAREY STEVENS, ANDREW PULLAN, PETER HUNTER, and PETER MULQUINEY. "NEW DEVELOPMENTS IN AN ANATOMICAL FRAMEWORK FOR MODELING CARDIAC ISCHEMIA." International Journal of Bifurcation and Chaos 13, no. 12 (December 2003): 3717–22. http://dx.doi.org/10.1142/s0218127403008818.
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A new, anatomically accurate, mathematical model of the right and left porcine ventricular myocardium is described based on measurements of the geometry and fibrous-sheet structure. Passive and active properties of the myocardium are calculated using an orthotropic constitutive law based on the fibrous-sheet structure and a biophysical cellular based model of cardiac contraction. Using Galerkin finite element techniques, the equations of finite deformation are solved to determine deformation and regional wall stress through the heart cycle. The mechanics model is coupled via myocardial wall stress, to a one-dimensional coronary blood flow model embedded in the myocardium. Bidomain electrical activation of the myocardium is also modeled, with ionic current based electrophysiological equations and reaction–diffusion equations based on orthotropic conductivity tensors referred to the fibrous-sheet material axes. Metabolic models are used to couple energy supply to contraction and excitation in the heart, and at the body surface, a framework for quantifying the effect of ischemic heart disease is developed.
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Caccavo, Diego, Sara Cascone, Gaetano Lamberti, Annalisa Dalmoro, and Anna Angela Barba. "Modeling of the Behavior of Natural Polysaccharides Hydrogels for Bio-pharma Applications." Natural Product Communications 12, no. 6 (June 2017): 1934578X1701200. http://dx.doi.org/10.1177/1934578x1701200609.
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Hydrogels, even if not exclusively obtained from natural sources, are widely used for pharmaceuticals and for biomedical applications. The reasons for their uses are their biocompatibility and the possibility to obtain systems and devices with different properties, due to variable characteristics of the materials. In order to effectively design and produce these systems and devices, two main ways are available: i) trial-and-error process, at least guided by experience, during which the composition of the system and the production steps are changed in order to get the desired behavior; ii) production process guided by the a-priori simulation of the systems’ behavior, thanks to proper tuned mathematical models of the reality. Of course the second approach, when applicable, allows tremendous savings in term of human and instrumental resources. In this mini-review, several modeling approaches useful to describe the behavior of natural polysaccharide-based hydrogels in bio-pharma applications are reported. In particular, reported case histories are: i) the size calculation of micro-particles obtained by ultrasound assisted atomization; ii) the release kinetics from core-shell micro-particles, iii) the solidification behavior of blends of synthetic and natural polymers for gel paving of blood vessels, iv) the drug release from hydrogel-based tablets. This material can be seen as a guide toward the use of mathematical modeling in bio-pharma applications.
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Raghu, Rashmi, Irene E. Vignon-Clementel, C. Alberto Figueroa, and Charles A. Taylor. "Comparative Study of Viscoelastic Arterial Wall Models in Nonlinear One-Dimensional Finite Element Simulations of Blood Flow." Journal of Biomechanical Engineering 133, no. 8 (August 1, 2011). http://dx.doi.org/10.1115/1.4004532.
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It is well known that blood vessels exhibit viscoelastic properties, which are modeled in the literature with different mathematical forms and experimental bases. The wide range of existing viscoelastic wall models may produce significantly different blood flow, pressure, and vessel deformation solutions in cardiovascular simulations. In this paper, we present a novel comparative study of two different viscoelastic wall models in nonlinear one-dimensional (1D) simulations of blood flow. The viscoelastic models are from papers by Holenstein et al. in 1980 (model V1) and Valdez-Jasso et al. in 2009 (model V2). The static elastic or zero-frequency responses of both models are chosen to be identical. The nonlinear 1D blood flow equations incorporating wall viscoelasticity are solved using a space-time finite element method and the implementation is verified with the Method of Manufactured Solutions. Simulation results using models V1, V2 and the common static elastic model are compared in three application examples: (i) wave propagation study in an idealized vessel with reflection-free outflow boundary condition; (ii) carotid artery model with nonperiodic boundary conditions; and (iii) subject-specific abdominal aorta model under rest and simulated lower limb exercise conditions. In the wave propagation study the damping and wave speed were largest for model V2 and lowest for the elastic model. In the carotid and abdominal aorta studies the most significant differences between wall models were observed in the hysteresis (pressure-area) loops, which were larger for V2 than V1, indicating that V2 is a more dissipative model. The cross-sectional area oscillations over the cardiac cycle were smaller for the viscoelastic models compared to the elastic model. In the abdominal aorta study, differences between constitutive models were more pronounced under exercise conditions than at rest. Inlet pressure pulse for model V1 was larger than the pulse for V2 and the elastic model in the exercise case. In this paper, we have successfully implemented and verified two viscoelastic wall models in a nonlinear 1D finite element blood flow solver and analyzed differences between these models in various idealized and physiological simulations, including exercise. The computational model of blood flow presented here can be utilized in further studies of the cardiovascular system incorporating viscoelastic wall properties.
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Nartsissov, Yaroslav R. "Application of a multicomponent model of convectional reaction-diffusion to description of glucose gradients in a neurovascular unit." Frontiers in Physiology 13 (August 22, 2022). http://dx.doi.org/10.3389/fphys.2022.843473.
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A supply of glucose to a nervous tissue is fulfilled by a cerebrovascular network, and further diffusion is known to occur at both an arteriolar and a microvascular level. Despite a direct relation, a blood flow dynamic and reaction-diffusion of metabolites are usually considered separately in the mathematical models. In the present study they are coupled in a multiphysical approach which allows to evaluate the effects of capillary blood flow changes on near-vessels nutrient concentration gradients evidently. Cerebral blood flow (CBF) was described by the non-steady-state Navier-Stokes equations for a non-Newtonian fluid whose constitutive law is given by the Carreau model. A three-level organization of blood–brain barrier (BBB) is modelled by the flux dysconnectivity functions including densities and kinetic properties of glucose transporters. The velocity of a fluid flow in brain extracellular space (ECS) was estimated using Darcy’s law. The equations of reaction-diffusion with convection based on a generated flow field for continues and porous media were used to describe spatial-time gradients of glucose in the capillary lumen and brain parenchyma of a neurovascular unit (NVU), respectively. Changes in CBF were directly simulated using smoothing step-like functions altering the difference of intracapillary pressure in time. The changes of CBF cover both the decrease (on 70%) and the increase (on 50%) in a capillary flow velocity. Analyzing the dynamics of glucose gradients, it was shown that a rapid decrease of a capillary blood flow yields an enhanced level of glucose in a near-capillary nervous tissue if the contacts between astrocytes end-feet are not tight. Under the increased CBF velocities the amplitude of glucose concentration gradients is always enhanced. The introduced approach can be used for estimation of blood flow changes influence not only on glucose but also on other nutrients concentration gradients and for the modelling of distributions of their concentrations near blood vessels in other tissues as well.
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Schneeweiss, Pia, Dorin Panescu, Dominik Stunder, Mark W. Kroll, Christopher J. Andrews, and Tobias Theiler. "Computational models for contact current dosimetry at frequencies below 1 MHz." Medical & Biological Engineering & Computing, December 2, 2020. http://dx.doi.org/10.1007/s11517-020-02284-9.
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AbstractElectric contact currents (CC) can cause muscle contractions, burns, or ventricular fibrillation which may result in life-threatening situations. In vivo studies with CC are rare due to potentially hazardous effects for participants. Cadaver studies are limited to the range of tissue’s electrical properties and the utilized probes’ size, relative position, and sensitivity. Thus, the general safety standards for protection against CC depend on a limited scientific basis. The aim of this study was therefore to develop an extendable and adaptable validated numerical body model for computational CC dosimetry for frequencies between DC and 1 MHz. Applying the developed model for calculations of the IEC heart current factors (HCF) revealed that in the case of transversal CCs, HCFs are frequency dependent, while for longitudinal CCs, the HCFs seem to be unaffected by frequency. HCFs for current paths from chest or back to hand appear to be underestimated by the International Electrotechnical Commission (IEC 60479-1). Unlike the HCFs provided in IEC 60479-1 for longitudinal current paths, our work predicts the HCFs equal 1.0, possibly due to a previously unappreciated current flow through the blood vessels. However, our results must be investigated by further research in order to make a definitive statement. Contact currents of frequencies from DC up to 100 kHz were conducted through the numerical body model Duke by seven contact electrodes on longitudinal and transversal paths. The resulting induced electric field and current enable the evaluation of the body impedance and the heart current factors for each frequency and current path.
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"Computer modeling in mechanics of circulation." Bulletin of V.N. Karazin Kharkiv National University, series «Mathematical modeling. Information technology. Automated control systems», no. 41 (2019). http://dx.doi.org/10.26565/2304-6201-2019-41-04.
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Some cardiovascular pathology connected with variations in geometry, wall properties and microcirculatory disorders can be studied by computer simulations. The mathematical model that allows to calculate the parameters of blood circulation – velocities of blood and pressure, displacements of the artery walls - for a complex vascular tree in real time is proposed.The geometrical model is based on the detailed postmortem measurements on the systemic arterial trees (more than 1000 arterial segments). The aortic model consists of 32 aortic segments and 59 side branches of the aorta including the larger and medium vessels. Mathematical model of blood flow in the system is described by Womersley model of the pulsatile viscous flow in the viscoelastic tube using the pressure and volumetric rate continuity conditions at the bifurcations of arteries. The Windkessel and structured tree outflow boundary conditions at the outlets of the branches have been used. The solution has been found as superposition of the forward and backward running waves. Based on the model, blood circulation parameters were calculated in the aortic model (91 tubes). The calculation results correspond to in vivo measurements. It was shown most of the branches have zero wave reflection coefficients but the large branches like celiac, renal and iliac arteries could produce noticeable wave reflections. The smaller branches possess negative wave reflection coefficient and, thus, contribute to the blood suction effect and lower aortic resistance to the blood flow. It is shown, the individual geometry plays an essential role in the location of the positive and negative wave reflection sites along the aorta and, thus, in the pressure and flow patterns and blood distribution into the branches. The influence of occlusion of the iliac arteries, low/high wall rigidity, and total length of aorta are studied on different individual geometries. The model can be used for determination of the individual parameters for patient-specific cardiovascular models and further modeling of the outcomes of the surgical and therapeutic procedures.
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Vignali, Emanuele, Emanuele Gasparotti, Katia Capellini, Benigno Marco Fanni, Luigi Landini, Vincenzo Positano, and Simona Celi. "Modeling biomechanical interaction between soft tissue and soft robotic instruments: importance of constitutive anisotropic hyperelastic formulations." International Journal of Robotics Research, July 14, 2020, 027836492092747. http://dx.doi.org/10.1177/0278364920927476.
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Cardiovascular diseases are the leading cause of death in the western countries. Robotic surgery recently emerged as a confirmed strategy in the cardiovascular field, especially thanks to the improvement of soft robotics. These techniques have demonstrated their potential in terms of speed of execution and precision. In this context, a deeper knowledge of the material properties of the blood vessels is required, especially for computational soft robotics applications. A constitutive model including the contribution of the collagen fibers families is needed to take hyperelasticity and anisotropy into account. For this purpose, four different models are presented: two fiber families with dispersion (2FFD), two fiber families without dispersion (2FF), four fiber families with dispersion (4FFD), and four fiber families without dispersion (4FF). A set of experimental biaxial data obtained from ex-vivo specimens was used to assess the model performances. Two fitting procedures were imposed: a procedure with no weighting of scores and a procedure with a weight set to enhance the model performances in the contact range. A finite element simulation of a contact procedure was developed to evaluate the effect on the contact pressures and forces according to the different model implementations. In particular, a minimally invasive aortic valve positioning process through a previously designed soft robot was simulated. The results confirmed the overall fitting procedure. The adoption of the weighting process for the fitting was successful, as it permitted an accurate prediction in the region of interest through models with less parameters.