scholarly journals Cerebral Vasculature Influences Blast-Induced Biomechanical Responses of Human Brain Tissue

2021 ◽  
Vol 9 ◽  
Author(s):  
Dhananjay Radhakrishnan Subramaniam ◽  
Ginu Unnikrishnan ◽  
Aravind Sundaramurthy ◽  
Jose E. Rubio ◽  
Vivek Bhaskar Kote ◽  
...  
Keyword(s):  
Human Brain ◽  
Shock Tube ◽  
Brain Tissue ◽  
Human Head ◽  
Cerebral Veins ◽  
Fe Model ◽  
Cerebral Vasculature ◽  
Tissue Properties ◽  
Biomechanical Responses ◽  
The Brain

Multiple finite-element (FE) models to predict the biomechanical responses in the human brain resulting from the interaction with blast waves have established the importance of including the brain-surface convolutions, the major cerebral veins, and using non-linear brain-tissue properties to improve model accuracy. We hypothesize that inclusion of a more detailed network of cerebral veins and arteries can further enhance the model-predicted biomechanical responses and help identify correlates of blast-induced brain injury. To more comprehensively capture the biomechanical responses of human brain tissues to blast-wave exposure, we coupled a three-dimensional (3-D) detailed-vasculature human-head FE model, previously validated for blunt impact, with a 3-D shock-tube FE model. Using the coupled model, we computed the biomechanical responses of a human head facing an incoming blast wave for blast overpressures (BOPs) equivalent to 68, 83, and 104 kPa. We validated our FE model, which includes the detailed network of cerebral veins and arteries, the gyri and the sulci, and hyper-viscoelastic brain-tissue properties, by comparing the model-predicted intracranial pressure (ICP) values with previously collected data from shock-tube experiments performed on cadaver heads. In addition, to quantify the influence of including a more comprehensive network of brain vessels, we compared the biomechanical responses of our detailed-vasculature model with those of a reduced-vasculature model and a no-vasculature model for the same blast-loading conditions. For the three BOPs, the predicted ICP values matched well with the experimental results in the frontal lobe, with peak-pressure differences of 4–11% and phase-shift differences of 9–13%. As expected, incorporating the detailed cerebral vasculature did not influence the ICP, however, it redistributed the peak brain-tissue strains by as much as 30% and yielded peak strain differences of up to 7%. When compared to existing reduced-vasculature FE models that only include the major cerebral veins, our high-fidelity model redistributed the brain-tissue strains in most of the brain, highlighting the importance of including a detailed cerebral vessel network in human-head FE models to more comprehensively account for the biomechanical responses induced by blast exposure.

scholarly journals Does Blast Exposure to the Torso Cause a Blood Surge to the Brain?

2020 ◽  
Vol 8 ◽  
Author(s):  
Jose E. Rubio ◽  
Maciej Skotak ◽  
Eren Alay ◽  
Aravind Sundaramurthy ◽  
Dhananjay Radhakrishnan Subramaniam ◽  
...  
Keyword(s):  
Brain Injury ◽  
Carotid Artery ◽  
Brain Tissue ◽  
Shear Stresses ◽  
Fe Model ◽  
Cerebral Vasculature ◽  
Blast Exposure ◽  
Indirect Mechanism ◽  
Wall Shear ◽  
The Brain

The interaction of explosion-induced blast waves with the torso is suspected to contribute to brain injury. In this indirect mechanism, the wave-torso interaction is assumed to generate a blood surge, which ultimately reaches and damages the brain. However, this hypothesis has not been comprehensively and systematically investigated, and the potential role, if any, of the indirect mechanism in causing brain injury remains unclear. In this interdisciplinary study, we performed experiments and developed mathematical models to address this knowledge gap. First, we conducted blast-wave exposures of Sprague-Dawley rats in a shock tube at incident overpressures of 70 and 130 kPa, where we measured carotid-artery and brain pressures while limiting exposure to the torso. Then, we developed three-dimensional (3-D) fluid-structure interaction (FSI) models of the neck and cerebral vasculature and, using the measured carotid-artery pressures, performed simulations to predict mass flow rates and wall shear stresses in the cerebral vasculature. Finally, we developed a 3-D finite element (FE) model of the brain and used the FSI-computed vasculature pressures to drive the FE model to quantify the blast-exposure effects in the brain tissue. The measurements from the torso-only exposure experiments revealed marginal increases in the peak carotid-artery overpressures (from 13.1 to 28.9 kPa). Yet, relative to the blast-free, normotensive condition, the FSI simulations for the blast exposures predicted increases in the peak mass flow rate of up to 255% at the base of the brain and increases in the wall shear stress of up to 289% on the cerebral vasculature. In contrast, our simulations suggest that the effect of the indirect mechanism on the brain-tissue-strain response is negligible (<1%). In summary, our analyses show that the indirect mechanism causes a sudden and abundant stream of blood to rapidly propagate from the torso through the neck to the cerebral vasculature. This blood surge causes a considerable increase in the wall shear stresses in the brain vasculature network, which may lead to functional and structural effects on the cerebral veins and arteries, ultimately leading to vascular pathology. In contrast, our findings do not support the notion of strain-induced brain-tissue damage due to the indirect mechanism.

Animal Orientation Affects Brain Biomechanical Responses to Blast-Wave Exposure

2021 ◽  
Author(s):  
Ginu Unnikrishnan ◽  
Haojie Mao ◽  
Sujith Sajja ◽  
Stephen van Albert ◽  
Aravind Sundaramurthy ◽  
...  
Keyword(s):  
Shock Tube ◽  
Blast Wave ◽  
Peak Pressure ◽  
Sagittal Plane ◽  
The Other ◽  
Peak Strain ◽  
Cerebral Vasculature ◽  
Biomechanical Responses ◽  
The Brain ◽  
Animal Orientation

Abstract In this study, we investigated how animal orientation within a shock tube influences the biomechanical responses of the brain and cerebral vasculature of a rat when exposed to a blast wave. Using three-dimensional finite-element models, we computed the biomechanical responses when the rat was exposed to the same blast-wave overpressure (100 kPa) in a prone (P), vertical (V), or head-only (HO) orientation. We validated our model by comparing the model-predicted and the experimentally measured brain pressures at the lateral ventricle. For all three orientations, the maximum difference between the predicted and measured pressures was 11%. Animal orientation markedly influenced the predicted peak pressure at the anterior position along the mid-sagittal plane of the brain (P = 187 kPa; V = 119 kPa; and HO = 142 kPa). However, the relative differences in the predicted peak pressure between the orientations decreased at the medial (21%) and posterior (7%) positions. In contrast to the pressure, the peak strain in the prone orientation relative to the other orientations at the anterior, medial, and posterior positions was 40-88% lower. Similarly, at these positions, the cerebral vasculature strain in the prone orientation was lower than the strain in the other orientations. These results show that animal orientation in a shock tube influences the biomechanical responses of the brain and the cerebral vasculature of the rat, strongly suggesting that a direct comparison of changes in brain tissue observed from animals exposed at different orientations can lead to incorrect conclusions.

scholarly journals A 3-D Finite-Element Minipig Model to Assess Brain Biomechanical Responses to Blast Exposure

2021 ◽  
Vol 9 ◽  
Author(s):  
Aravind Sundaramurthy ◽  
Vivek Bhaskar Kote ◽  
Noah Pearson ◽  
Gregory M. Boiczyk ◽  
Elizabeth M. McNeil ◽  
...  
Keyword(s):  
Brain Tissue ◽  
Material Properties ◽  
Laboratory Experiments ◽  
Scaling Laws ◽  
Brain Injuries ◽  
Blast Waves ◽  
High Fidelity ◽  
Fe Model ◽  
Cerebral Vasculature ◽  
Biomechanical Responses

Despite years of research, it is still unknown whether the interaction of explosion-induced blast waves with the head causes injury to the human brain. One way to fill this gap is to use animal models to establish “scaling laws” that project observed brain injuries in animals to humans. This requires laboratory experiments and high-fidelity mathematical models of the animal head to establish correlates between experimentally observed blast-induced brain injuries and model-predicted biomechanical responses. To this end, we performed laboratory experiments on Göttingen minipigs to develop and validate a three-dimensional (3-D) high-fidelity finite-element (FE) model of the minipig head. First, we performed laboratory experiments on Göttingen minipigs to obtain the geometry of the cerebral vasculature network and to characterize brain-tissue and vasculature material properties in response to high strain rates typical of blast exposures. Next, we used the detailed cerebral vasculature information and species-specific brain tissue and vasculature material properties to develop the 3-D high-fidelity FE model of the minipig head. Then, to validate the model predictions, we performed laboratory shock-tube experiments, where we exposed Göttingen minipigs to a blast overpressure of 210 kPa in a laboratory shock tube and compared brain pressures at two locations. We observed a good agreement between the model-predicted pressures and the experimental measurements, with differences in maximum pressure of less than 6%. Finally, to evaluate the influence of the cerebral vascular network on the biomechanical predictions, we performed simulations where we compared results of FE models with and without the vasculature. As expected, incorporation of the vasculature decreased brain strain but did not affect the predictions of brain pressure. However, we observed that inclusion of the cerebral vasculature in the model changed the strain distribution by as much as 100% in regions near the interface between the vasculature and the brain tissue, suggesting that the vasculature does not merely decrease the strain but causes drastic redistributions. This work will help establish correlates between observed brain injuries and predicted biomechanical responses in minipigs and facilitate the creation of scaling laws to infer potential injuries in the human brain due to exposure to blast waves.

scholarly journals Scatterometry Measurements With Scattered Light Imaging Enable New Insights Into the Nerve Fiber Architecture of the Brain

2021 ◽  
Vol 15 ◽  
Author(s):  
Miriam Menzel ◽  
Marouan Ritzkowski ◽  
Jan A. Reuter ◽  
David Gräßel ◽  
Katrin Amunts ◽  
...  
Keyword(s):  
Human Brain ◽  
Nerve Fiber ◽  
Brain Tissue ◽  
Scattered Light ◽  
Polar Angle ◽  
Nerve Fibers ◽  
Fiber Architecture ◽  
Whole Brain ◽  
Tissue Samples ◽  
The Brain

The correct reconstruction of individual (crossing) nerve fibers is a prerequisite when constructing a detailed network model of the brain. The recently developed technique Scattered Light Imaging (SLI) allows the reconstruction of crossing nerve fiber pathways in whole brain tissue samples with micrometer resolution: the individual fiber orientations are determined by illuminating unstained histological brain sections from different directions, measuring the transmitted scattered light under normal incidence, and studying the light intensity profiles of each pixel in the resulting image series. So far, SLI measurements were performed with a fixed polar angle of illumination and a small number of illumination directions, providing only an estimate of the nerve fiber directions and limited information about the underlying tissue structure. Here, we use a display with individually controllable light-emitting diodes to measure the full distribution of scattered light behind the sample (scattering pattern) for each image pixel at once, enabling scatterometry measurements of whole brain tissue samples. We compare our results to coherent Fourier scatterometry (raster-scanning the sample with a non-focused laser beam) and previous SLI measurements with fixed polar angle of illumination, using sections from a vervet monkey brain and human optic tracts. Finally, we present SLI scatterometry measurements of a human brain section with 3 μm in-plane resolution, demonstrating that the technique is a powerful approach to gain new insights into the nerve fiber architecture of the human brain.

scholarly journals Spontaneous glioma-induced seizures recorded in a living human brain tissue preparation

2019 ◽  
Vol 21 (Supplement_4) ◽  
pp. iv16-iv16
Author(s):  
Alastair Kirby ◽  
Jose Pedro Lavrador ◽  
Christian Brogna ◽  
Francesco Vergani ◽  
Bassel Zebian ◽  
...  
Keyword(s):  
Human Brain ◽  
Brain Tissue ◽  
Aminolevulinic Acid ◽  
Brain Slices ◽  
Low Grade ◽  
Tissue Preparation ◽  
Spontaneous Seizure ◽  
Human Brain Tissue ◽  
Who Grade ◽  
The Brain

Abstract Gliomas often present clinically with seizures. Tumour-associated seizures can be difficult to control with medication. A deeper understanding of the cellular mechanisms underlying tumour-associated seizures would provide a basis for developing new treatments. Here, we investigate epileptic discharges in peritumoral cortex using living human brain tissue donated by people having a craniotomy for glioma resection (REC approval, 18/SW/002). The brain tissue was cut into thin slices, which preserved the architecture of the glioma and the adjacent healthy brain. The brain slices were incubated in 5-aminolevulinic acid to make the glioma cells fluorescent. This enabled us to make electrophysiological recordings of brain activity across the boundary between glioma and brain. We recorded from brain slices of 5 participants with glioblastoma and 4 participants with oligodendroglioma (WHO grade II – III). Spontaneous “seizure-like” discharges were recorded in brain slices from 5/8 participants (3 GBM, 2 oligodendroglioma) who reported seizures and from one participant (GBM) who had not had any clinical seizures. Further analysis of the seizure-like discharges revealed that they could be subdivided into two distinct types based on the major frequencies in the discharge. We concluded that human brain slices from people with either a low-grade or a high-grade glioma can generate spontaneous seizure-like discharges. The living human brain tissue preparation gives us a platform to study the mechanisms of tumour-associated seizures and how abnormal neural activity affects glioma growth.

THE INFLUENCE OF BRAIN TISSUE MATERIAL PARAMETERS ON THE RESPONSE OF DYNAMIC CHARACTERISTICS BASED ON FINITE ELEMENT MODEL

2019 ◽  
Vol 19 (08) ◽  
pp. 1940058
Author(s):  
BIN YANG ◽  
HAO SUN ◽  
AIYUAN WANG ◽  
QUN WANG
Keyword(s):  
Finite Element ◽  
Head And Neck ◽  
Brain Tissue ◽  
Dynamic Characteristics ◽  
Human Head ◽  
Initial Parameter ◽  
Fe Model ◽  
Nasal Cartilage ◽  
Material Parameters ◽  
Tissue Material

Aiming at the uncertainty of material parameters of human brain tissue, the influence of tissue material performance sensitivity on frequency and mode shape under free vibration is studied. In this paper, the 50th percentile finite element (FE) model of human head and neck with detailed anatomical characteristics has been chosen as the research object, the parameters of skull, cerebrospinal fluid (CSF) and brain tissue materials with high sensitivity are analyzed by orthogonal test design and variance analysis. The results show that the natural frequencies of Group 7, Group 8 and Group 9 are all around 230[Formula: see text]Hz, which are basically consistent with the initial parameter of 229.18[Formula: see text]Hz, and the intracranial displacements of the three groups are also concentrated on the lateral nasal cartilage. The main reason is that the Young’s modulus of the skull used in three groups of experiments is 9780[Formula: see text]Mpa, which is close to the initial parameter of 8000[Formula: see text]Mpa. It indicates that the material parameter of the skull has the greatest influence on the dynamic characteristics of human head and neck, followed by the CSF and brain tissue. This study provides an effective method for vehicle safety and head and neck injury protection, and supplies a reference for FE analysis of head collision damage.

Nonlinear poroplastic model of ventricular dilation in hydrocephalus

2008 ◽  
Vol 109 (1) ◽  
pp. 100-107 ◽  
Author(s):  
Shahan Momjian ◽  
Denis Bichsel
Keyword(s):  
Brain Tissue ◽  
Normal Pressure ◽  
Porous Matrix ◽  
Brain Parenchyma ◽  
Plastic Behavior ◽  
Fe Model ◽  
Mechanical Behaviors ◽  
Ventricular Dilation ◽  
Numerical Finite Element ◽  
The Brain

Object The mechanism of ventricular dilation in normal-pressure hydrocephalus remains unclear. Numerical finite-element (FE) models of hydrocephalus have been developed to investigate the biomechanics of ventricular enlargement. However, previous linear poroelastic models have failed to reproduce the relatively larger dilation of the horns of the lateral ventricles. In this paper the authors instead elaborated on a nonlinear poroplastic FE model of the brain parenchyma and studied the influence of the introduction of these potentially more realistic mechanical behaviors on the prediction of the ventricular shape. Methods In the proposed model the elasticity modulus varies as a function of the distension of the porous matrix, and the internal mechanical stresses are relaxed after each iteration, thereby simulating the probable plastic behavior of the brain tissue. The initial geometry used to build the model was extracted from CT scans of patients developing hydrocephalus, and the results of the simulations using this model were compared with the real evolution of the ventricular size and shape in the patients. Results The authors' model predicted correctly the magnitude and shape of the ventricular dilation in real cases of acute and chronic hydrocephalus. In particular, the dilation of the frontal and occipital horns was much more realistic. Conclusions This finding suggests that the nonlinear and plastic mechanical behaviors implemented in the present numerical model probably occur in reality. Moreover, the availability of such a valid FE model, whose mechanical parameters approach real mechanical properties of the brain tissue, might be useful in the further modeling of ventricular dilation at a normal pressure.

Simulation of Brain Response to Noncontact Impacts Using Coupled Eulerian–Lagrangian Method

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Miao Na ◽  
Timothy J. Beavers ◽  
Abhijit Chandra ◽  
Sarah A. Bentil
Keyword(s):  
Brain Tissue ◽  
Mechanical Response ◽  
Brain Regions ◽  
Von Mises Stress ◽  
Fe Model ◽  
Brain Response ◽  
Fe Method ◽  
Angular Velocities ◽  
Von Mises ◽  
The Brain

Abstract Finite element (FE) method has been widely used for gaining insights into the mechanical response of brain tissue during impacts. In this study, a coupled Eulerian−Lagrangian (CEL) formulation is implemented in impact simulations of a head system to overcome the mesh distortion difficulties due to large deformation in the cerebrospinal fluid (CSF) region and provide a biofidelic model of the interaction between the brain and skull. The head system used in our FE model is constructed from the transverse section of the human brain, with CSF modeled by Eulerian elements. Spring connectors are applied to represent the pia-arachnoid connection between the brain and skull. Validations of the CEL formulation and the FE model are performed using the experimental results. The dynamic response of brain tissue under noncontact impacts and the brain regions susceptible to injury are evaluated based on the intracranial pressure (ICP), maximum principal strain (MPS), and von Mises stress. While tracking the critical MPS location on the brain, higher likelihood of contrecoup injury than coup injury is found when sudden brain−skull motion takes place. The accumulation effect of CSF in the ventricle system, under large relative brain−skull motion, is also identified. The FE results show that adding relative angular velocities, to the translational impact model, not only causes a diffuse high strain area, but also cause the temporal lobes to be susceptible to cerebral contusions since the protecting CSF is prone to be squeezed away at the temporal sites due to the head rotations.

A Nonlinear Reduced-Order Model of the Corpus Callosum Under Planar Coronal Excitation

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Alireza Mojahed ◽  
Javid Abderezaei ◽  
Mehmet Kurt ◽  
Lawrence A. Bergman ◽  
Alexander F. Vakakis
Keyword(s):  
Corpus Callosum ◽  
Human Brain ◽  
Strain Localization ◽  
High Frequency ◽  
Reduced Order Model ◽  
Fe Model ◽  
Order Model ◽  
Reduced Order ◽  
Biomechanical Behavior ◽  
The Brain

Abstract Traumatic brain injury (TBI) is often associated with microstructural tissue damage in the brain, which results from its complex biomechanical behavior. Recent studies have shown that the deep white matter (WM) region of the human brain is susceptible to being damaged due to strain localization in that region. Motivated by these studies, in this paper, we propose a geometrically nonlinear dynamical reduced order model (ROM) to model and study the dynamics of the deep WM region of the human brain under coronal excitation. In this model, the brain hemispheres were modeled as lumped masses connected via viscoelastic links, resembling the geometry of the corpus callosum (CC). Employing system identification techniques, we determined the unknown parameters of the ROM, and ensured the accuracy of the ROM by comparing its response against the response of an advanced finite element (FE) model. Next, utilizing modal analysis techniques, we determined the energy distribution among the governing modes of vibration of the ROM and concluded that the demonstrated nonlinear behavior of the FE model might be predominantly due to the special geometry of the brain deep WM region. Furthermore, we observed that, for sufficiently high input energies, high frequency harmonics at approximately 45 Hz, were generated in the response of the CC, which, in turn, are associated with high-frequency oscillations of the CC. Such harmonics might potentially lead to strain localization in the CC. This work is a step toward understanding the brain dynamics during traumatic injury.

scholarly journals P11.49 An electrophysiological signature of glioma infiltration in the ex vivo human brain

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii54-iii54
Author(s):  
A J Kirby ◽  
J P Lavrador ◽  
C Brogna ◽  
F Vergani ◽  
C Chandler ◽  
...  
Keyword(s):  
Human Brain ◽  
Brain Tissue ◽  
Brain Slices ◽  
Glioma Cells ◽  
Low Grade ◽  
Tissue Preparation ◽  
High Grade ◽  
Spontaneous Seizure ◽  
Human Brain Tissue ◽  
The Brain

Abstract BACKGROUND Invading glioma cells affect the physiological function of the peritumoural cortex. This may manifest clinically as seizures. Here, we investigate the effect the invading glioma cells on the electrophysiological signalling of the peritumoral cortex using living human brain tissue donated by people having a craniotomy for glioma resection (REC approval, 18/SW/002). MATERIAL AND METHODS The brain tissue was cut into thin slices, which preserved the architecture of the glioma and the adjacent healthy brain. The brain slices were incubated in 5-aminolevulinic acid to make the glioma cells fluorescent. We observed 5-ALA induced fluorescence in both low-grade and high-grade gliomas. This enabled us to make electrophysiological recordings of brain activity across the boundary between glioma and brain. RESULTS We recorded from brain slices of 5 participants with glioblastoma and 4 participants with oligodendroglioma (WHO grade II - III). Spontaneous “seizure-like” discharges were recorded in brain slices from 5/8 participants (3 GBM, 2 oligodendroglioma) who reported seizures and from one participant (GBM) who had not had any clinical seizures. Further analysis of the electrical discharges revealed that they could be subdivided into two distinct types based on the major frequencies in the discharge. CONCLUSION We concluded that human brain slices from people with either a low-grade or a high-grade glioma can generate spontaneous seizure-like discharges. This electrophysiological signature will be compared to infiltration and grade of the glioma cells in the donated sample. The living human brain tissue preparation gives us a platform to study the mechanisms of tumour-associated seizures and how abnormal neural activity affects glioma growth.

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