Brain tissue elastic behavior and experimental brain compression

1988 ◽  
Vol 255 (5) ◽  
pp. R799-R805 ◽  
Author(s):  
A. Schettini ◽  
E. K. Walsh
Keyword(s):  
Brain Tissue ◽  
Mechanical Response ◽  
Fluid Pressure ◽  
Elastic Parameter ◽  
Elastic Behavior ◽  
Present Observation ◽  
Tissue Elasticity ◽  
Tissue Pressure ◽  
Brain Compression ◽  
Nonlinear Elastic

This study was designed to test the hypothesis that the progressive expansion of an extradural mass causes detectable changes in brain mechanical response properties, in particular the nonlinear elastic behavior, before any significant changes in intracranial cerebrospinal fluid pressure can be detected. In 10 chronically prepared and anesthetized dogs, incremental inflation (0.07 ml/s) of an extradural balloon caused 1) a progressive fall in the brain nonlinear elastic parameter (G0, mmHg/mm2), 2) nonsignificant changes in brain tissue elasticity (G0, mmHg/mm), 3) a disproportionate progressive rise in subpial tension, and 4) a progressive fall in local cerebral blood flow (H2 clearance), despite a modest decrease in cerebral perfusion pressure (extracranial). In previous brain compression experiments (Brain Res. 305: 141-143, 1984) we have shown that the compression site becomes compacted and stiffer (increased G0) and its nonlinear elastic parameter (G0) increases markedly. These earlier findings, coupled with the present observation of a loss in tissue nonlinearity distally to the compression site, are most likely the major mechanisms by which, with a rapidly expanding intracranial mass, tissue pressure gradients and brain displacement, including transtentorial herniation, develop.

Analysis of Nonlinear Responses of Adherent Epithelial Cells Probed by Magnetic Bead Twisting: A Finite Element Model Based on a Homogenization Approach

2004 ◽  
Vol 126 (6) ◽  
pp. 685-698 ◽  
Author(s):  
Jacques Ohayon ◽  
Philippe Tracqui ◽  
Redouane Fodil ◽  
Sophie Fe´re´ol ◽  
Vale´rie M. Laurent ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Mechanical Response ◽  
Cell Model ◽  
Element Model ◽  
Magnetic Bead ◽  
Homogenization Method ◽  
Elastic Behavior ◽  
Spatially Distributed ◽  
Homogenization Approach ◽  
Nonlinear Elastic

An original homogenization method was used to analyze the nonlinear elastic properties of epithelial cells probed by magnetic twisting cytometry. In this approach, the apparent rigidity of a cell with nonlinear mechanical properties is deduced from the mechanical response of the entire population of adherent cells. The proposed hyperelastic cell model successfully accounts for the variability in probe-cell geometrical features, and the influence of the cell–substrate adhesion. Spatially distributed local secant elastic moduli had amplitudes ranging from 10 to 400 Pa. The nonlinear elastic behavior of cells may contribute to the wide differences in published results regarding cell elasticity moduli.

Effect of central venous pressure on brain tissue pressure and brain volume

1976 ◽  
Vol 45 (1) ◽  
pp. 89-94 ◽  
Author(s):  
Jochen Cuypers ◽  
Frank Matakas ◽  
Sam J. Potolicchio
Keyword(s):  
Central Venous Pressure ◽  
Water Content ◽  
Brain Tissue ◽  
Brain Volume ◽  
Venous Pressure ◽  
Fluid Pressure ◽  
Venous Hypertension ◽  
Central Venous ◽  
Tissue Pressure ◽  
The Brain

✓ In cats, brain tissue pressure (BTP) was measured by the wick-catheter method. The BTP was positive, but lower than cerebrospinal fluid pressure. Elevation of central venous pressure led only to a transient proportional increase of BTP. When the calvaria and dura of one hemisphere were removed, the rise of BTP was even less. Water content of the brain was normal in either case, even after prolonged venous hypertension. Venous hypertension led in all cases to a marked increase of the brain volume which was caused by vessel dilatation. In brain edema, produced by rinsing the brain surface with ouabain and concentrated saline, BTP was increased permanently by venous hypertension. The water content of the brain was much greater than normal. From these results it was concluded that congestive edema does not occur in the brain unless the tissue is damaged. However, venous hypertension does cause brain swelling.

scholarly journals How to characterize a nonlinear elastic material? A review on nonlinear constitutive parameters in isotropic finite elasticity

2017 ◽  
Vol 473 (2207) ◽  
pp. 20170607 ◽  
Author(s):  
L. Angela Mihai ◽  
Alain Goriely
Keyword(s):  
Elastic Material ◽  
Mechanical Response ◽  
Finite Elasticity ◽  
Experimental Tests ◽  
Elastic Parameter ◽  
Hyperelastic Materials ◽  
Poisson Function ◽  
Elastic Responses ◽  
Nonlinear Elastic ◽  
Constitutive Parameters

The mechanical response of a homogeneous isotropic linearly elastic material can be fully characterized by two physical constants, the Young’s modulus and the Poisson’s ratio, which can be derived by simple tensile experiments. Any other linear elastic parameter can be obtained from these two constants. By contrast, the physical responses of nonlinear elastic materials are generally described by parameters which are scalar functions of the deformation, and their particular choice is not always clear. Here, we review in a unified theoretical framework several nonlinear constitutive parameters, including the stretch modulus, the shear modulus and the Poisson function, that are defined for homogeneous isotropic hyperelastic materials and are measurable under axial or shear experimental tests. These parameters represent changes in the material properties as the deformation progresses, and can be identified with their linear equivalent when the deformations are small. Universal relations between certain of these parameters are further established, and then used to quantify nonlinear elastic responses in several hyperelastic models for rubber, soft tissue and foams. The general parameters identified here can also be viewed as a flexible basis for coupling elastic responses in multi-scale processes, where an open challenge is the transfer of meaningful information between scales.

Strain Energy Descriptions of Biological Swelling I: Single Fluid Compartment Models

1987 ◽  
Vol 109 (3) ◽  
pp. 252-256 ◽  
Author(s):  
D. K. Bogen
Keyword(s):  
Strain Energy ◽  
Fluid Pressure ◽  
Elastic Stability ◽  
Elastic Behavior ◽  
Tissue Fluid ◽  
Tissue Pressure ◽  
Energy Functions ◽  
Fluid Compartment ◽  
Strain Energy Functions ◽  
Tissue Models

Strain energy functions are derived from biphasic soft tissue models in order to describe large-deformation, large-swelling, elastic behavior of nonlinear materials. The resulting analysis leads to calculations of stress-extension relations and tissue fluid pressure. Also explored are the elastic stability of the biphasic tissue models and the manner in which tissue pressure is altered by material deformation.

Constitutive Modeling of Brain Tissue: Current Perspectives

2016 ◽  
Vol 68 (1) ◽  
Author(s):  
Rijk de Rooij ◽  
Ellen Kuhl
Keyword(s):  
Brain Tissue ◽  
Mechanical Response ◽  
Deformation Gradient ◽  
Constitutive Models ◽  
Time Dependent ◽  
Elastic Behavior ◽  
Integral Approach ◽  
Mechanical Stimuli ◽  
The Past ◽  
The Brain

Modeling the mechanical response of the brain has become increasingly important over the past decades. Although mechanical stimuli to the brain are small under physiological conditions, mechanics plays a significant role under pathological conditions including brain development, brain injury, and brain surgery. Well calibrated and validated constitutive models for brain tissue are essential to accurately simulate these phenomena. A variety of constitutive models have been proposed over the past three decades, but no general consensus on these models exists. Here, we provide a comprehensive and structured overview of state-of-the-art modeling of the brain tissue. We categorize the different features of existing models into time-independent, time-dependent, and history-dependent contributions. To model the time-independent, elastic behavior of the brain tissue, most existing models adopt a hyperelastic approach. To model the time-dependent response, most models either use a convolution integral approach or a multiplicative decomposition of the deformation gradient. We evaluate existing constitutive models by their physical motivation and their practical relevance. Our comparison suggests that the classical Ogden model is a well-suited phenomenological model to characterize the time-independent behavior of the brain tissue. However, no consensus exists for mechanistic, physics-based models, neither for the time-independent nor for the time-dependent response. We anticipate that this review will provide useful guidelines for selecting the appropriate constitutive model for a specific application and for refining, calibrating, and validating future models that will help us to better understand the mechanical behavior of the human brain.

Brain tissue pressure in focal cerebral ischemia

1985 ◽  
Vol 62 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Fausto Iannotti ◽  
Julian T. Hoff ◽  
Gerald P. Schielke
Keyword(s):  
Blood Flow ◽  
Pressure Gradient ◽  
Brain Tissue ◽  
Focal Cerebral Ischemia ◽  
Fluid Pressure ◽  
Artery Occlusion ◽  
Tissue Pressure ◽  
Edema Formation ◽  
Content Type ◽  
Ischemic Brain Edema

✓ Twenty-three anesthetized cats underwent permanent middle cerebral artery occlusion in a study of the relationships of regional cerebral blood flow, ventricular fluid pressure, brain tissue pressure, and ischemic edema formation. A pressure gradient of 8 mm Hg developed between ischemic tissue and normally perfused tissue during a 4-hour observation period after occlusion. Brain water accumulated as tissue pressure rose, while blood flow in the same area fell. The data suggest, but do not prove, that ischemic brain edema causes tissue pressure to rise focally, and that blood flow to the ischemic zone is compromised further by the resultant hydrostatic pressure gradient.

Regional brain tissue pressure gradients created by expanding extradural temporal mass lesion

1997 ◽  
Vol 86 (3) ◽  
pp. 505-510 ◽  
Author(s):  
Christopher E. Wolfla ◽  
Thomas G. Luerssen ◽  
Robin M. Bowman
Keyword(s):  
Intracranial Pressure ◽  
Frontal Lobe ◽  
Brain Tissue ◽  
Temporal Lobe ◽  
Mass Lesion ◽  
Pressure Monitor ◽  
Tissue Pressure ◽  
Content Type ◽  
Regional Brain ◽  
The Right

✓ A porcine model of regional intracranial pressure was used to compare regional brain tissue pressure (RBTP) changes during expansion of an extradural temporal mass lesion. Measurements of RBTP were obtained by placing fiberoptic intraparenchymal pressure monitors in the right and left frontal lobes (RF and LF), right and left temporal lobes (RT and LT), midbrain (MB), and cerebellum (CB). During expansion of the right temporal mass, significant RBTP gradients developed in a reproducible pattern: RT > LF = LT > RF > MB > CB. These gradients appeared early, widened as the volume of the mass increased, and persisted for the entire duration of the experiment. The study indicates that RBTP gradients develop in the presence of an extradural temporal mass lesion. The highest RBTP was recorded in the ipsilateral temporal lobe, whereas the next highest was recorded in the contralateral frontal lobe. The RBTP that was measured in either frontal lobe underestimated the temporal RBTP. These results indicated that if a frontal intraparenchymal pressure monitor is used in a patient with temporal lobe pathology, the monitor should be placed on the contralateral side and a lower threshold for therapy of increased intracranial pressure should be adopted. Furthermore, this study provides further evidence that reliance on a single frontal intraparenchymal pressure monitor may not detect all areas of elevated RBTP.

Intraventricular injection of antibodies to β1-integrins generates pressure gradients in the brain favoring hydrocephalus development in rats

2009 ◽  
Vol 297 (5) ◽  
pp. R1312-R1321 ◽  
Author(s):  
Gurjit Nagra ◽  
Lena Koh ◽  
Isabelle Aubert ◽  
Minhui Kim ◽  
Miles Johnston
Keyword(s):  
Fluid Pressure ◽  
Active Role ◽  
Intraventricular Injection ◽  
Pressure Gradients ◽  
Tissue Pressure ◽  
Before And After ◽  
The Matrix ◽  
System 2 ◽  
Periventricular Area ◽  
The Brain

In some tissues, the injection of antibodies to the β1-integrins leads to a reduction in interstitial fluid pressure, indicating an active role for the extracellular matrix in tissue pressure regulation. If perturbations of the matrix occur in the periventricular area of the brain, a comparable lowering of interstitial pressures may induce transparenchymal pressure gradients favoring ventricular expansion. To examine this concept, we measured periventricular (parenchymal) and ventricular pressures with a servo-null micropipette system (2-μm tip) in adult Wistar rats before and after anti-integrin antibodies or IgG/IgM isotype controls were injected into a lateral ventricle. In a second group, the animals were kept for 2 wk after similar injections and after euthanization, the brains were removed and assessed for hydrocephalus. In experiments in which antibodies to β1-integrins ( n = 10) but not isotype control IgG/IgM ( n = 7) were injected, we observed a decline in periventricular pressures relative to the preinjection values. Under similar circumstances, ventricular pressures were elevated ( n = 10) and were significantly greater than those in the periventricular interstitium. We estimated ventricular to periventricular pressure gradients of up to 4.3 cmH2O. In the chronic preparations, we observed enlarged ventricles in many of the animals that received injections of anti-integrin antibodies (21 of 29 animals; 72%) but not in any animal receiving the isotype controls. We conclude that modulation/disruption of β1-integrin-matrix interactions in the brain generates pressure gradients favoring ventricular expansion, suggesting a novel mechanism for hydrocephalus development.

Uncertainty Quantification in Predicting Behaviour of Rubber-Like Materials in Uni-Axial Loading

2020 ◽  
Author(s):  
Aref Ghaderi ◽  
Vahid Morovati ◽  
Pouyan Nasiri ◽  
Roozbeh Dargazany
Keyword(s):  
Uncertainty Quantification ◽  
Mechanical Response ◽  
Pure Shear ◽  
Constitutive Models ◽  
Material Behavior ◽  
Elastic Behavior ◽  
Deterministic Models ◽  
Data Set ◽  
Material Parameters ◽  
Axial Extension

Abstract Material parameters related to deterministic models can have different values due to variation of experiments outcome. From a mathematical point of view, probabilistic modeling can improve this problem. It means that material parameters of constitutive models can be characterized as random variables with a probability distribution. To this end, we propose a constitutive models of rubber-like materials based on uncertainty quantification (UQ) approach. UQ reduces uncertainties in both computational and real-world applications. Constitutive models in elastomers play a crucial role in both science and industry due to their unique hyper-elastic behavior under different loading conditions (uni-axial extension, biaxial, or pure shear). Here our goal is to model the uncertainty in constitutive models of elastomers, and accordingly, identify sensitive parameters that we highly contribute to model uncertainty and error. Modern UQ models can be implemented to use the physics of the problem compared to black-box machine learning approaches that uses data only. In this research, we propagate uncertainty through the model, characterize sensitivity of material behavior to show the importance of each parameter for uncertainty reduction. To this end, we utilized Bayesian rules to develop a model considering uncertainty in the mechanical response of elastomers. As an important assumption, we believe that our measurements are around the model prediction, but it is contaminated by Gaussian noise. We can make the noise by maximizing the posterior. The uni-axial extension experimental data set is used to calibrate the model and propagate uncertainty in this research.

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