scholarly journals Untangling the Effect of Head Acceleration on Brain Responses to Blast Waves

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Haojie Mao ◽  
Ginu Unnikrishnan ◽  
Vineet Rakesh ◽  
Jaques Reifman
Keyword(s):  
Quantitative Description ◽  
Blast Waves ◽  
Head Model ◽  
Maximum Pressure ◽  
Head Acceleration ◽  
Brain Responses ◽  
Biomechanical Response ◽  
The Individual ◽  
The Brain ◽  
Brain Pressure

Multiple injury-causing mechanisms, such as wave propagation, skull flexure, cavitation, and head acceleration, have been proposed to explain blast-induced traumatic brain injury (bTBI). An accurate, quantitative description of the individual contribution of each of these mechanisms may be necessary to develop preventive strategies against bTBI. However, to date, despite numerous experimental and computational studies of bTBI, this question remains elusive. In this study, using a two-dimensional (2D) rat head model, we quantified the contribution of head acceleration to the biomechanical response of brain tissues when exposed to blast waves in a shock tube. We compared brain pressure at the coup, middle, and contre-coup regions between a 2D rat head model capable of simulating all mechanisms (i.e., the all-effects model) and an acceleration-only model. From our simulations, we determined that head acceleration contributed 36–45% of the maximum brain pressure at the coup region, had a negligible effect on the pressure at the middle region, and was responsible for the low pressure at the contre-coup region. Our findings also demonstrate that the current practice of measuring rat brain pressures close to the center of the brain would record only two-thirds of the maximum pressure observed at the coup region. Therefore, to accurately capture the effects of acceleration in experiments, we recommend placing a pressure sensor near the coup region, especially when investigating the acceleration mechanism using different experimental setups.

scholarly journals In silico investigation of biomechanical response of a human subjected to primary blast

2021 ◽  
Author(s):  
Sunil Sutar ◽  
Shailesh Ganpule
Keyword(s):  
White Matter ◽  
Blast Wave ◽  
Rotational Motion ◽  
Blast Waves ◽  
Primary Blast ◽  
Body Model ◽  
The Past ◽  
Biomechanical Response ◽  
The Brain ◽  
Full Body

The response of the brain to the explosion induced primary blast waves is actively sought. Over the past decade, reasonable progress has been made in the fundamental understanding of bTBI using head surrogates and animal models. Yet, the current understanding of how blast waves interact with the human is in nascent stages, primarily due to lack of data in humans. The biomechanical response in human is critically required so that connection to the aforementioned bTBI models can be faithfully established. Here, using a detailed, full-body human model, we elucidate the biomechanical cascade of the brain under a primary blast. The input to the model is incident overpressure as achieved by specifying charge mass and standoff distance through ConWep. The full-body model allows to holistically probe short- (<5 ms) and long-term (200 ms) brain biomechanical responses. The full-body model has been extensively validated against impact loading in the past. In this work, we validate the head model against blast loading. We also incorporate structural anisotropy of the brain white matter. Blast wave human interaction is modeled using a conventional weapon modeling approach. We demonstrate that the blast wave transmission, linear and rotational motion of the head are dominant pathways for the biomechanical loading of the brain, and these loading paradigms generate distinct biomechanical fields within the brain. Blast transmission and linear motion of the head govern the volumetric response, whereas the rotational motion of the head governs the deviatoric response. We also observe that blast induced head rotation alone produces a diffuse injury pattern in white matter fiber tracts. Lastly, we find that the biomechanical response under blast is comparable to the impact event. These insights will augment laboratory and clinical investigations of bTBI and help devise better blast mitigation strategies.

The Strain Rates of the Brain and Skull Under Dynamic Loading

2018 ◽  
Author(s):  
Mohammad Hosseini Farid ◽  
Ashkan Eslaminejad ◽  
Mohammadreza Ramzanpour ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Material Properties ◽  
Brain Injuries ◽  
Human Head ◽  
Element Model ◽  
Blast Waves ◽  
Cranial Bone ◽  
Strain Rates ◽  
Head Acceleration ◽  
Blunt Impact ◽  
The Brain

Accurate material properties of the brain and skull are needed to examine the biomechanics of head injury during highly dynamic loads such as blunt impact or blast. In this paper, a validated Finite Element Model (FEM) of a human head is used to study the biomechanics of the head in impact and blast leading to traumatic brain injuries (TBI). We simulate the head under various direction and velocity of impacts, as well as helmeted and un-helmeted head under blast waves. It is shown that the strain rates for the brain at impacts and blast scenarios are usually in the range of 36 to 241 s−1. The skull was found to experience a rate in the range of 14 to 182 s−1 under typical impact and blast cases. Results show for impact incidents the strain rates of brain and skull are approximately 1.9 and 0.7 times of the head acceleration. Also, this ratio of strain rate to head acceleration for the brain and skull was found to be 0.86 and 0.43 under blast loadings. These findings provide a good insight into measuring the brain tissue and cranial bone, and selecting material properties in advance for FEM of TBI.

scholarly journals Cortical responses to natural speech reflect probabilistic phonotactics

2018 ◽  
Author(s):  
Giovanni M. Di Liberto ◽  
Daniel Wong ◽  
Gerda Ana Melnik ◽  
Alain de Cheveigné
Keyword(s):  
Low Frequency ◽  
English Word ◽  
Natural Speech ◽  
Neural Encoding ◽  
Individual Subject ◽  
Brain Responses ◽  
Learning Development ◽  
The Individual ◽  
The Brain

AbstractHumans comprehend speech despite the various challenges of real-world environments, such as loud noise and mispronunciation. Our auditory system is robust to these thanks to the integration of the upcoming sensory input with prior knowledge and expectations built on language-specific regularities. One such regularity regards the permissible phoneme sequences, which determine the likelihood that a word belongs to a given language (phonotactic probability; “blick” is more likely to be an English word than “bnick”). Previous research suggested that violations of these rules modulate brain evoked responses such as the N400 and the late positive complex. Yet several fundamental questions remain unresolved, especially regarding the neural encoding and integration strategy of phonotactic information. Here, we used linear modelling approaches to assess the influence of phonotactic probabilities on the brain responses to narrative speech measured with non-invasive EEG. We found that the relationship between continuous speech and EEG responses is best described when the speech descriptor includes phonotactic probabilities. This provides us with a methodology to isolate and measure the brain responses to phonotactics using natural speech at the individual subject-level. Furthermore, such low-frequency signals showed the strongest speech-EEG interactions at latencies of 100-400 ms, supporting a pre-lexical role of phonotactic information.Significance StatementSpeech is composed of basic units, called phonemes, whose combinations comply with language-specific regularities determining whether a sequence “sounds” as a plausible word. Our ability to detect irregular combinations requires matching incoming sequences with our internal expectations, a process that supports speech segmentation and learning. However, the neural mechanisms underlying this phenomenon have not yet been established. Here, we examine this in the human brain using narrative speech. We identified a brain signal reflecting the likelihood that a word belongs to the language, which may offer new opportunities to investigate speech perception, learning, development, and impairment. Our data also suggest a pre-lexical role of this phenomenon, thus supporting and extending current mechanistic perspectives.

Computation of Blast-Induced Traumatic Brain Injury

2009 ◽  
Author(s):  
M. S. Chafi ◽  
G. Karami ◽  
M. Ziejewski
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Blast Wave ◽  
Human Head ◽  
Propagation Model ◽  
Head Model ◽  
Brain Response ◽  
Brain Responses ◽  
The Impact ◽  
The Brain

In this paper, an integrated numerical approach is introduced to determine the human brain responses when the head is exposed to blast explosions. The procedure is based on a 3D non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock wave propagation, and blast-brain interaction of the confronting human head. Due to the fact that there is no reported experimental data on blast-head interactions, several important checkpoints should be made before trusting the brain responses resulting from the blast modeling. These checkpoints include; a) a validated human head FEM subjected to impact loading; b) a validated air-free blast propagation model; and c) the verified blast waves-solid interactions. The simulations presented in this paper satisfy the above-mentioned requirements and checkpoints. The head model employed here has been validated again impact loadings. In this respect, Chafi et al. [1] have examined the head model against the brain intracranial pressure, and brain’s strains under different impact loadings of cadaveric experimental tests of Hardy et al. [2]. In another report, Chafi et al. [3] has examined the air-blast and blast-object simulations using Arbitrary Lagrangian Eulerian (ALE) multi-material and Fluid-Solid Interaction (FSI) formulations. The predicted results of blast propagation matched very well with those of experimental data proving that this computational solid-fluid algorithm is able to accurately predict the blast wave propagation in the medium and the response of the structure to blast loading. Various aspects of blast wave propagations in air as well as when barriers such as solid walls are encountered have been studied. With the head model included, different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80cm (2.62 feet) from the explosion core. The impact of brain response due to severity of the blast under different amounts of the explosive material, TNT (0.0838, 0.205, and 0.5lb) is examined. The accuracy of the modeling can provide the information to design protection facilities for human head for the hostile environments.

scholarly journals A simplified human head finite element model for brain injury assessment of blunt impacts

2020 ◽  
Vol 14 (2) ◽  
pp. 6538-6547 ◽  
Author(s):  
M.H.A. Hassan ◽  
Z. Taha ◽  
I. Hasanuddin ◽  
A.P.P.A. Majeed ◽  
H. Mustafa ◽  
...  
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Human Head ◽  
Brain Trauma ◽  
Head Model ◽  
Human Cadaver ◽  
Brain Responses ◽  
Dimensional Models ◽  
The Brain ◽  
Head Neck

Blunt impacts contribute more than 95% of brain trauma injuries in Malaysia. Modelling and simulation of these impacts are essential in understanding the mechanics of the injuries to develop a protective equipment that might prevent brain trauma. Various finite element models of human head have been developed, ranging from two-dimensional models to very complex three-dimensional models. The aim of this study is to develop a simplified three-dimensional human head model with low computational cost, yet capable of producing reliable brain responses. The influence of different head-neck boundary conditions on the brain responses were also examined. Our model was validated against an experimental work on human cadaver. The model with free head-neck boundary condition was found to be in good agreement with experimental results. The head-neck joint was found to have a significant influence on the brain responses upon impact. Further investigations on the head-neck joint modelling are needed. Our simplified model was successfully validated against experimental data on human cadaver and could be used in simulating blunt impact scenarios.

scholarly journals The Strain Rates in the Brain, Brainstem, Dura, and Skull under Dynamic Loadings

2020 ◽  
Vol 25 (2) ◽  
pp. 21 ◽  
Author(s):  
Mohammad Hosseini-Farid ◽  
MaryamSadat Amiri-Tehrani-Zadeh ◽  
Mohammadreza Ramzanpour ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Dura Mater ◽  
Material Properties ◽  
Brain Injuries ◽  
Human Head ◽  
Biological Tissues ◽  
Cranial Bone ◽  
Head Model ◽  
Strain Rates ◽  
Head Acceleration ◽  
The Brain

Knowing the precise material properties of intracranial head organs is crucial for studying the biomechanics of head injury. It has been shown that these biological tissues are significantly rate-dependent; hence, their material properties should be determined with respect to the range of deformation rate they experience. In this paper, a validated finite element human head model is used to investigate the biomechanics of the head in impact and blast, leading to traumatic brain injuries (TBI). We simulate the head under various directions and velocities of impacts, as well as helmeted and unhelmeted head under blast shock waves. It is demonstrated that the strain rates for the brain are in the range of 36 to 241 s−1, approximately 1.9 and 0.86 times the resulting head acceleration under impacts and blast scenarios, respectively. The skull was found to experience a rate in the range of 14 to 182 s−1, approximately 0.7 and 0.43 times the head acceleration corresponding to impact and blast cases. The results of these incident simulations indicate that the strain rates for brainstem and dura mater are respectively in the range of 15 to 338 and 8 to 149 s−1. These findings provide a good insight into characterizing the brain tissue, cranial bone, brainstem and dura mater, and also selecting material properties in advance for computational dynamical studies of the human head.

Effects of Head Orientation on the Intracranial Pressure of Rats Exposed to Shock Waves

2012 ◽  
Author(s):  
Alessandra Dal Cengio Leonardi ◽  
Nickolas Keane ◽  
Cynthia Bir ◽  
Pamela VandeVord
Keyword(s):  
Shock Wave ◽  
Intracranial Pressure ◽  
Experimental Studies ◽  
Head Orientation ◽  
Blast Exposure ◽  
Plate Elements ◽  
Biomechanical Response ◽  
Response Modes ◽  
The Individual ◽  
The Brain

With the increasing number of military personnel returning from conflicts with neurological manifestations of traumatic brain injury (TBI), there has been a great focus on the effects resulting from blast exposure (Okie 2005; Hicks et al. 2010). Recently, experimental studies have been reported which investigated the biomechanical response of the rat head exposed to a shock wave. The results indicated that the imparted shock wave may induce multiple response modes of the skull, including global flexure, which may have a significant contribution to the mechanism of injury (Bolander et al. 2011; Dal Cengio Leonardi et al. 2011). However, the question of whether head orientation could play a role in the level of energy imparted on the brain is still of concern. This study quantitatively measured the effect of head orientation on intracranial pressure (ICP) of rats exposed to a shock wave. Furthermore, the study examined how skull maturity affects ICP response at various orientations. It was hypothesized firstly that skull flexural modes dominate the ICP response, hence varying head orientation would be expected to alter this imparted stress waveform. The head orientation affects not only the shape and size of the “presented area” exposed to the incident wave, but the degree and nature of the response of the individual skull plate elements due to the variance of skull physiology. As such, this has a significant influence on the stress that the shock wave imparts on the brain due to changes in skull dynamics.

Development of a Finite Element Human Head Model Partially Validated With Thirty Five Experimental Cases

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Haojie Mao ◽  
Liying Zhang ◽  
Binhui Jiang ◽  
Vinay V. Genthikatti ◽  
Xin Jin ◽  
...  
Keyword(s):  
Human Head ◽  
Head Model ◽  
Facial Bone ◽  
Brain Contusion ◽  
Technical Paper ◽  
Brain Motion ◽  
Car Crash ◽  
Injury Mechanisms ◽  
The Brain ◽  
Brain Pressure

This study is aimed to develop a high quality, extensively validated finite element (FE) human head model for enhanced head injury prediction and prevention. The geometry of the model was based on computed tomography (CT) and magnetic resonance imaging scans of an adult male who has the average height and weight of an American. A feature-based multiblock technique was adopted to develop hexahedral brain meshes including the cerebrum, cerebellum, brainstem, corpus callosum, ventricles, and thalamus. Conventional meshing methods were used to create the bridging veins, cerebrospinal fluid, skull, facial bones, flesh, skin, and membranes—including falx, tentorium, pia, arachnoid, and dura. The head model has 270,552 elements in total. Thirty five loading cases were selected from a range of experimental head impacts to check the robustness of the model predictions based on responses including the brain pressure, relative skull-brain motion, skull response, and facial response. The brain pressure was validated against intracranial pressure data reported by Nahum et al. (1977, “Intracranial Pressure Dynamics During Head Impact,” Proc. 21st Stapp Car Crash Conference, SAE Technical Paper No. 770922) and Trosseille et al. (1992, “Development of a F.E.M. of the Human Head According to a Specific Test Protocol,” Proc. 36th Stapp Car Crash Conference, SAE Technical Paper No. 922527). The brain motion was validated against brain displacements under sagittal, coronal, and horizontal blunt impacts performed by Hardy et al. (2001, “Investigation of Head Injury Mechanisms Using Neutral Density Technology and High-Speed Biplanar X-Ray,” Stapp Car Crash Journal, 45, pp. 337–368; and 2007, “A Study of the Response of the Human Cadaver Head to Impact,” Stapp Car Crash Journal, 51, pp. 17–80). The facial bone responses were validated under nasal impact (Nyquist et al. 1986, “Facial Impact Tolerance and Response,” Proc. 30th Stapp Car Crash Conference, SAE Technical Paper No. 861896), zygoma and maxilla impact (Allsop et al. 1988, “Facial Impact Response – A Comparison of the Hybrid III Dummy and Human Cadaver,” Proc. 32nd Stapp Car Crash Conference, SAE Technical Paper No. 881719)]. The skull bones were validated under frontal angled impact, vertical impact, and occipital impact (Yoganandan et al. 1995, “Biomechanics of Skull Fracture,” J Neurotrauma, 12(4), pp. 659–668) and frontal horizontal impact (Hodgson et al. 1970, “Fracture Behavior of the Skull Frontal Bone Against Cylindrical Surfaces,” 14th Stapp Car Crash Conference, SAE International, Warrendale, PA). The FE head model was further used to study injury mechanisms and tolerances for brain contusion (Nahum et al. 1976, “An Experimental Model for Closed Head Impact Injury,” 20th Stapp Car Crash Conference, SAE International, Warrendale, PA). Studies from 35 loading cases demonstrated that the FE head model could predict head responses which were comparable to experimental measurements in terms of pattern, peak values, or time histories. Furthermore, tissue-level injury tolerances were proposed. A maximum principal strain of 0.42% was adopted for skull cortical layer fracture and maximum principal stress of 20 MPa was used for skull diploë layer fracture. Additionally, a plastic strain threshold of 1.2% was used for facial bone fracture. For brain contusion, 277 kPa of brain pressure was calculated from reconstruction of one contusion case.

Understanding the Mechanics of Blast Pressure Waves Inside a Shock-Tube: Effects of Geometry Optimization on the Blast Profile

2017 ◽  
Author(s):  
Ashkan Eslaminejad ◽  
Hesam Sarvghad-Moghaddam ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Shock Tube ◽  
Cross Section ◽  
Blast Waves ◽  
Head Model ◽  
Maximum Pressure ◽  
Pressure Waves ◽  
Cfd Analysis ◽  
Shock Tubes ◽  
Ansys Cfx ◽  
Negative Impulse

While many theoretical and numerical studies have been carried out to study blast induced traumatic brain injury (bTBI), validation of simulation results is still a concern due to moral issues and experimental constraints. Shock-tubes are one of the major means for replicating blast waves in a controlled medium. North Dakota State University Shock-tube (NDSUST) has been designed to simulate the blast shockwaves in an attempt to study and investigate bTBI. However, accurate replication of a blast profile in terms of the impulse and overpressure is highly dependent on the geometrical features of the shock-tube. To this end, numerical methods such as computational fluid dynamic (CFD) analysis can help to evaluate and increase the efficiency of the current shock-tubes. The NDSUST contains three major parts, namely, driver (the high pressure container), driven cone, and the chamber to setup the head model. The driver and driven cone are separated by layers of Mylar membrane. Shockwaves are defined by three pressure-time characteristics; positive phase (positive impulse), negative phase (negative impulse), and maximum pressure (overpressure). While the current NDSUST simulated most shockwave characteristics accurately, the negative impulse was observed to be considerably long. The diameter of Mylar membrane interface, the volume of the deriver, and the chamber room cross-section connected to the driven cone, were considered as possible parameters affecting the efficiency of the shock-tube. Accordingly, NDSUST was modeled in ANSYS CFX using its actual dimensions. A transient CFD analysis was carried out using ANSYS CFX to simulate the turbulent, supersonic, and compressible flow upon rupture of the Mylar membrane in order to study the pressure wave propagation inside the shock-tube. No-slip boundary conditions were chosen for the shock-tube walls. Driver and driven sections were considered as two separate domains connected using an interface. The shockwave was generated by setting the driver and driven sections at high and low pressures, respectively and running the simulation for a total time of 1 second. The primary results revealed that the current cross-section at the interface of the driven cone and the square chamber caused the pressure disruption (pressure oscillation) upon entrance of the pressure waves into the chamber room. In addition, it was concluded that the driver volume would affect the negative impulse’s duration and the negative peak pressure.

Fit Vs Faint: Assessing Work Causation in “Idiopathic Fall” Cases

2014 ◽  
Vol 19 (5) ◽  
pp. 3-12
Author(s):  
Lorne Direnfeld ◽  
David B. Torrey ◽  
Jim Black ◽  
LuAnn Haley ◽  
Christopher R. Brigham
Keyword(s):  
Blood Flow ◽  
Electrical Activity ◽  
Loss Of Consciousness ◽  
Brain Electrical Activity ◽  
Medical Terminology ◽  
Scientific Analysis ◽  
Medical Causation ◽  
The Individual ◽  
The Brain ◽  
Current Science

Abstract When an individual falls due to a nonwork-related episode of dizziness, hits their head and sustains injury, do workers’ compensation laws consider such injuries to be compensable? Bearing in mind that each state makes its own laws, the answer depends on what caused the loss of consciousness, and the second asks specifically what happened in the fall that caused the injury? The first question speaks to medical causation, which applies scientific analysis to determine the cause of the problem. The second question addresses legal causation: Under what factual circumstances are injuries of this type potentially covered under the law? Much nuance attends this analysis. The authors discuss idiopathic falls, which in this context means “unique to the individual” as opposed to “of unknown cause,” which is the familiar medical terminology. The article presents three detailed case studies that describe falls that had their genesis in episodes of loss of consciousness, followed by analyses by lawyer or judge authors who address the issue of compensability, including three scenarios from Arizona, California, and Pennsylvania. A medical (scientific) analysis must be thorough and must determine the facts regarding the fall and what occurred: Was the fall due to a fit (eg, a seizure with loss of consciousness attributable to anormal brain electrical activity) or a faint (eg, loss of consciousness attributable to a decrease in blood flow to the brain? The evaluator should be able to fully explain the basis for the conclusions, including references to current science.

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