Constitutive model for brain tissue under finite compression

Laksari, Kaveh; Shafieian, Mehdi; Darvish, Kurosh

doi:10.1016/j.jbiomech.2011.12.023

Cited by 107 publications

(65 citation statements)

References 11 publications

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“…We have not attempted to apply to our data any complex mathematical models such as quasi-linear viscoelasticity. 17 The practical value of our data lies in the relative changes in mechanical properties and the extent to which they might aid in the understanding of technologies applied to the human situation. An example of one such technology is handheld mechanical testing devices, which can be used to obtain quantitative data from palpation.…”

Section: Fig 3 Uppermentioning

confidence: 99%

Intracranial biomechanics following cortical contusion in live rats

Alfasi¹,

Shulyakov

Bigio

2013

JNS

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Object. The goal of this study was to examine the mechanical properties of living rat intracranial contents and corresponding brain structural alterations following parietal cerebral cortex contusion.Methods. After being anesthetized, young adult rats were subjected to parietal craniotomy followed by cortical contusion using a calibrated weight-drop method. Magnetic resonance imaging was used to visualize the contusion. At the site of contusion, instrumented force-controlled indentation was performed 2 hours to 21 days later on the intact dural surface. The force-deformation (stress-strain) relationship was used to calculate elastic (indentation modulus) and strain changes over time, and constant hold or cyclic stress was used to evaluate viscoelastic deformation. These measurements were followed by histological studies.Results. At contusion sites, the indentation modulus was significantly decreased at 1-3 days and tended to be above control values at 21 days. Multicycle indentation showed that the brain tended to accumulate more strain (an indicator of viscosity) by 1 day after the contusion. Imaging and histological studies showed local edema and hemorrhage at 6 hours to 3 days and accumulation of reactive astrocytes, which began at 3 days and was pronounced by 21 days.Conclusions. The viscoelastic properties of living rat brain change following contusion. Initially, edema and tissue necrosis occur, and the brain becomes less elastic and less viscous. Later, along with undergoing reactive astroglial changes, the brain tends to become stiffer than normal. These quantitative data, which are related to the physical changes in the brain following trauma and which reflect subjective impressions upon palpation, will be useful for understanding emerging diagnostic tools such as magnetic resonance elastography.

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Section: Fig 3 Uppermentioning

confidence: 99%

Intracranial biomechanics following cortical contusion in live rats

Alfasi¹,

Shulyakov

Bigio

2013

JNS

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“…3 and 5). Viscoelastic behavior of brain tissue has been reported in a number of studies, 8,9,13,20,24,26,29 but standard methods for calculating the R 0 do not take viscoelasticity into account. Taken together, these observations support our hypothesis that the clinically observed underestimation of R 0 is due to methods that do not account for the viscoelasticity of the brain.…”

Section: Possible Causes Of Underestimation Of the Rmentioning

confidence: 99%

“…The data that do not consider viscoelasticity were generated using the Marmarou equation. Two sets of viscoelastic properties based on experimental data from rat 8 (green) and bovine 20 (blue) brain tissue were considered. Viscoelasticity affected the initial phase of the ICP change caused by infusion of the CSF through constant flow (A) or at constant pressure (B).…”

Section: How Viscoelasticity Influences R 0 Calculationsmentioning

confidence: 99%

“…8,20 Although the brain evidently contributes to the mechanical response of the craniospinal space, it is not the only structure to do so. This means that the most suitable viscoelastic parameters for in vivo use will have to be determined in clinical studies.…”

Section: Limitations and Outlookmentioning

confidence: 99%

“…The visco elastic nature of brain tissue has been demonstrated and quantified ex vivo in animal experiments 8,20,29 and in vivo using MR elastography on healthy volunteers. 13,18,26 Chang es of viscoelastic properties in hydrocephalic patients have been characterized by the latter method both before and after shunting.…”

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confidence: 99%

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Assessment of intracranial dynamics in hydrocephalus: effects of viscoelasticity on the outcome of infusion tests

Bottan

Daners

Zélicourt

et al. 2013

JNS

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Object The treatment of hydrocephalus requires insight into the intracranial dynamics in the patient. Resistance to CSF outflow (R0) is a clinically obtainable parameter of intracranial fluid dynamics that quantifies the apparent resistance to CSF absorption. It is used as a criterion for the selection of shunt candidates and serves as an indicator of shunt performance. The R0 is obtained clinically by performing 1 of 3 infusion tests: constant flow, constant pressure, or bolus infusion. Among these, the bolus infusion method has the shortest examination times and provides the shortest time of exposure of patients to artificially increased intracranial pressure (ICP) levels. However, for unknown reasons, the bolus infusion method systematically underestimates the R0. Here, the authors have tested and verified the hypothesis that this underestimation is due to lack of accounting for viscoelasticity of the craniospinal space in the calculation of the R0. Methods The authors developed a phantom model of the human craniospinal space in order to reproduce in vivo pressure-volume (PV) relationships during infusion testing. The phantom model followed the Marmarou exponential PV equation and also included a viscoelastic response to volume changes. Parameters of intracranial fluid dynamics, such as the R0, could be controlled and set independently. In addition to the phantom model, the authors designed a computational framework for virtual infusion testing in which viscoelasticity can be turned on or off in a controlled manner. Constant flow, constant pressure, and bolus infusion tests were performed on the phantom model, as well as on the virtual computational platform, using standard clinical protocols. Values for the R0 were derived from each infusion test by using both a standard method based on the Marmarou PV equation and a novel method based on a system identification approach that takes into account viscoelastic behavior. Results Experiments with the phantom model confirmed clinical observations that both the constant flow and constant pressure infusion tests, but not the bolus infusion test, yield correct R0 values when they are determined with the standard method according to Marmarou. Equivalent results were obtained using the computational framework. When the novel system identification approach was used to determine the R0, all of the 3 infusion tests yielded correct values for the R0. Conclusions The authors' investigations demonstrate that intracranial dynamics have a substantial viscoelastic component. When this viscoelastic component is taken into account in calculations, the R0, is no longer underestimated in the bolus infusion test.

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Measurement of the nonlinear mechanical properties of a poly(vinyl alcohol) sponge under longitudinal and circumferential loading

Karimi

Navidbakhsh

2013

J of Applied Polymer Sci

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Poly(vinyl alcohol) sponges (P‐sponges) have been used as a potential implant material for the replacement and repair of soft tissues, including cartilage, liver, and kidney. However, the application of P‐sponges as tissue replacement materials is almost entirely bounded because of a lack of sufficient mechanical properties. In this study, we characterized the mechanical properties of a fabricated poly(vinyl alcohol) sponge (P‐sponge) under a series of longitudinal and circumferential uniaxial loadings. The nonlinear mechanical behavior of the P‐sponge was also computationally investigated with hyperelastic strain energy density functions, that is, the Ogden, Yeoh, Mooney–Rivlin, and Neo‐Hookean models. A hyperelastic constitutive model was selected to best fit the axial behavior of the sponge. The results reveal that the Young's modulus and maximum stress of the P‐sponge in the longitudinal direction were 16 and 17% greater than that in the circumferential direction, respectively. The Yeoh model, in addition, was selected to represent the nonlinear behavior of the poly(vinyl alcohol) material and could be used in future biomechanical simulations of the soft tissues. These results can be used to understand the mechanical properties of spongy materials in different loading directions. In addition, they have implications for ophthalmic and plastic surgeries and wound healing and tissue engineering purposes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40257.

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Constitutive model for brain tissue under finite compression

Cited by 107 publications

References 11 publications

Intracranial biomechanics following cortical contusion in live rats

Intracranial biomechanics following cortical contusion in live rats

Assessment of intracranial dynamics in hydrocephalus: effects of viscoelasticity on the outcome of infusion tests

Measurement of the nonlinear mechanical properties of a poly(vinyl alcohol) sponge under longitudinal and circumferential loading

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