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Author: Michelle Kyaw Nyein Publisher: ISBN: Category : Languages : en Pages : 167
Book Description
Since the beginning of the military conflicts in Iraq and Afghanistan, there have been over 250,000 diagnoses of traumatic brain injury (TBI) in the U.S. military, with the majority of incidents caused by improvised explosive devices (IEDs). Despite the urgent need to understand blast-induced TBI in order to devise strategies for protection and treatment, much remains unknown about the mechanism of injury, the effects of personal protective equipment (PPE) such as helmets, and injury metrics and thresholds. In order to help address these gaps, this thesis has four objectives: 1) to present a comprehensive computational framework for investigating the mechanical response of the human head to blasts that includes blast-structure interaction codes, a detailed, three-dimensional model of a human head generated from high-resolution medical imaging data, and an experimentally-validated constitutive model for brain tissue; 2) to validate the framework against a broad range of experiments, including free-field blast tests involving physical human head surrogates and laboratory-scale shock tube tests involving animals and human cadavers; 3) to use the computational framework to investigate the effect of PPE on the propagation of stress waves within the brain following blast events and evaluate their blast protection performance; and 4) to develop interspecies scaling laws for the blast response of the brain that would allow translation of injury metrics from animals to humans.
Author: Michelle Kyaw Nyein Publisher: ISBN: Category : Languages : en Pages : 167
Book Description
Since the beginning of the military conflicts in Iraq and Afghanistan, there have been over 250,000 diagnoses of traumatic brain injury (TBI) in the U.S. military, with the majority of incidents caused by improvised explosive devices (IEDs). Despite the urgent need to understand blast-induced TBI in order to devise strategies for protection and treatment, much remains unknown about the mechanism of injury, the effects of personal protective equipment (PPE) such as helmets, and injury metrics and thresholds. In order to help address these gaps, this thesis has four objectives: 1) to present a comprehensive computational framework for investigating the mechanical response of the human head to blasts that includes blast-structure interaction codes, a detailed, three-dimensional model of a human head generated from high-resolution medical imaging data, and an experimentally-validated constitutive model for brain tissue; 2) to validate the framework against a broad range of experiments, including free-field blast tests involving physical human head surrogates and laboratory-scale shock tube tests involving animals and human cadavers; 3) to use the computational framework to investigate the effect of PPE on the propagation of stress waves within the brain following blast events and evaluate their blast protection performance; and 4) to develop interspecies scaling laws for the blast response of the brain that would allow translation of injury metrics from animals to humans.
Author: Michelle Kyaw Nyein Publisher: ISBN: Category : Languages : en Pages : 113
Book Description
Blast-induced TBI has gained prominence in recent years due to the conflicts in Iraq and Afghanistan, yet little is known about the mechanical effects of blasts on the human head; no injury thresholds have been established for blast effects on the head, and even direct transmission of the shock wave to the intracranial cavity is disputed. Still less is known about how personal protective equipment such as the Advanced Combat Helmet (ACH) affect the brain's response to blasts. The goal of this thesis is to investigate the mechanical response of the human brain to blasts and to study the effect of the ACH on the blast response of the head. To that end, a biofidelic computational model of the human head consisting of 11 distinct structures was developed from high-resolution medical imaging data. The model, known as the DVBIC/MIT Full Head Model (FHM), was subjected to blasts with incident overpressures of 6 atm and 30 atm and to a 5 m/s lateral impact. Results from the simulations demonstrate that blasts can penetrate the intracranial cavity and generate intracranial pressures that exceed the pressures produced during impact; the results suggest that blasts can plausibly directly cause traumatic brain injury. Subsequent investigation of the effect of the ACH on the blast response of the head found that the ACH provided minimal mitigation of blast effects. Results from the simulations conducted with the FHM extended to include the ACH suggest that the ACH can slightly reduce peak pressure magnitudes and delay peak pressure arrival times, but the benefits are minimal because the ACH does not protect the main pathways of load transmission from the blast to brain tissue. A more effective blast mitigation strategy might involve altering the helmet design to more completely surround the head in order to protect it from direct exposure to blast waves.
Author: Publisher: ISBN: Category : Languages : en Pages : 17
Book Description
The finite element simulation of blast wave formation, wave interactions with the head and subsequent response in the brain to blast exposure various conditions were carried out. Based on Bowen's curve, the maximum peak pressure transmitted to the scalp, skull and brain were about 3, 12 and 4 times respectively higher than the blast pressure received by the head. Increasing levels of overpressure produced higher intracranial pressure and strain. In contrast, increasing levels of impulse had adverse effects on the brain pressure. A person in a prone head-on position subjected to the ground explosion would sustain a greater damage in the brain as compared to one standing in a free blast condition. The effects of being adjacent to a reflecting wall were noticeable only on the region of the brain closer to the wall. The blast threats based on Bowen iso-damage curve of short duration regimen do not always produce the same level of compressive stress responses in the brain. These variations in tissue response predict potential multi-level damage outcomes rather than the same level estimated using the blast input-based tolerance curve of Bowen.
Author: Tyler Haladuick Publisher: ISBN: Category : Languages : en Pages :
Book Description
In Operations Enduring Freedom and Iraqi Freedom, explosions accounted for 81% of all injuries; this is a higher casualty percentage than in any previous wars. Blast wave overpressure has recently been associated with varying levels of traumatic brain injury in soldiers exposed to blast loading. Presently, the injury mechanism behind primary blast brain injury is not well understood due to the complex interactions between the blast wave and the human body. Despite these limitations in the understanding of head injury thresholds, head kinematics are often used to predict the overall potential for head injury. The purpose of this study was to investigate head kinematics, and predict injury from a range of simulated blast loads at varying standoff distances and differing heights of bursts. The validated Generator of body data multi-body human surrogate model allows for numerical kinematic data simulation in explicit finite element method fluid structure interaction blast modeling. Two finite element methods were investigated to simulate blast interaction with humans, an enhanced blast uncoupled method, and an Arbitrary Lagrangian Eularian fully coupled method. The enhanced blast method defines an air blast function through the application of a blast pressure wave, including ground reflections, based on the explosives relative location to a target; the pressures curves are based on the Convention Weapons databases. LBE model is efficient for parametric numerical studies of blast interaction where the target response is the only necessary result. The ALE model, unlike classical Lagrangian methods, has a fixed finite element mesh that allows material to flow through it; this enables simulation of large deformation problems such as blast in an air medium and its subsequent interaction with structures. The ALE model should be used when research into a specific blast scenario is of interest, since this method is more computationally expensive. The ALE method can evaluate a blast scenario in more detail including: explosive detonation, blast wave development and propagation, near-field fireball effects, blast wave reflection, as well as 3D blast wave interaction, reflection and refraction with a target. Both approaches were validated against experimental blast tests performed by Defense Research and Development Valcartier and ConWep databases for peak pressure, arrival time, impulse, and curve shape. The models were in good agreement with one another and follow the experimental data trend showing an exponential reduction in peak acceleration with increasing standoff distance until the Mach stem effect reached head height. The Mach stem phenomenon is a shock front formed by the merging of the incident and reflected shock waves; it increases the applied peak pressure and duration of a blast wave thus expanding the potential head injury zone surrounding a raised explosive. The enhanced blast model was in good agreement with experimental data in the near-field, and mid-field; however, overestimated the peak acceleration, and head injury criteria values in the far-field due to an over predicted pressure impulse force. The ALE model also over predicted the response based on the head injury criteria at an increased standoff distance due to smearing of the blast wave over several finite elements leading to an increased duration loading. According to the Abbreviated Injury Scale, the models predicted a maximal level 6 injury for all explosive sizes in the near-field, with a rapid acceleration of the head over approximately 1 ms. There is a drastic exponential reduction in the insult force and potential injury received with increasing standoff distance outside of the near-field region of an explosive charge.
Author: Robbin Elizabeth Bertucci Publisher: ISBN: Category : Languages : en Pages : 180
Book Description
Explosives have become increasingly common on the battlefield worldwide. Military personnel and civilians often experience blast loading to the lower extremity due to its direct contact with the ground and floor of vehicles. The pressure and axial loading from these incidents often lead to detrimental injuries. These injuries can be due to a number of mechanisms terming them primary, secondary, tertiary, or quaternary blast injuries. Of these injuries, this study will focus on primary and tertiary injuries, specifically bone fractures, compartment syndrome, and soft tissue disruption which often result from blast loading due to these mechanisms. However, the pressure and load levels causing these injuries are unknown. Currently, the methodologies, which study the injury criteria and design of blast mitigating structures, are limited. The main limitations are the lower rates of testing (automobile), specimen limitation (cadavers, surrogates, etc.), cost, and testing repeatability. Consequently, the goal of this dissertation is to develop a realistic computational model which can be used to improve the injury criteria, personal protective equipment (PPE), and vehicular structure in a cost effective and timely manner. Three Aims were thus pursued. For Specific Aim 1, a standing lower extremity was developed, verified, and simulated with several open-air blast loading conditions. Specific Aim 2 focused on validating the lower extremity model using experimental drop tower test results. In the drop tower simulation, the lower extremity model was successfully converted into a seated posture model and setup with similar loading and boundary conditions as the experiment. Specific Aim 3 involved incorporating a boot into the standing lower extremity model and evaluating its ability to mitigate pressure waves. In summary, Specific Aims 1 and 2 developed, verified, and validated a realistic human lower extremity model for the use in blast simulations. Specific Aim 3 further confirmed the models use in developing PPE.
Author: Raj K. Narayan Publisher: McGraw-Hill ISBN: 9780070456624 Category : Medical Languages : en Pages : 1558
Book Description
This reference is a comprehensive work in the field of neurotrauma and critical care. It incorporates the fields of head injury, spinal injury and basic neurotrauma research into one source. The major emphasis is on the treatment of patients with head and spinal cord injury, including the management of all other problems that bear upon the care of these patients.
Author: Daniel Laskowitz Publisher: CRC Press ISBN: 1498766579 Category : Medical Languages : en Pages : 388
Book Description
Traumatic brain injury (TBI) remains a significant source of death and permanent disability, contributing to nearly one-third of all injury related deaths in the United States and exacting a profound personal and economic toll. Despite the increased resources that have recently been brought to bear to improve our understanding of TBI, the developme
Author: Talat Kiris Publisher: Springer Science & Business Media ISBN: 321175718X Category : Medical Languages : en Pages : 454
Book Description
This comprehensive volume is the current final word on the subject. It contains more than 90 papers, giving a summary of clinical and basic studies on cerebral vasospasm. It includes reviews by leading researchers in the field. Several new subjects are proposed for future research that will not only promote research from neurosurgery and neurology but also from other interconnecting fields of emergency medicine, electrophysiology, molecular biology, and vascular biology.
Author: National Research Council Publisher: National Academies Press ISBN: 0309288037 Category : Medical Languages : en Pages : 215
Book Description
In the past decade, few subjects at the intersection of medicine and sports have generated as much public interest as sports-related concussions - especially among youth. Despite growing awareness of sports-related concussions and campaigns to educate athletes, coaches, physicians, and parents of young athletes about concussion recognition and management, confusion and controversy persist in many areas. Currently, diagnosis is based primarily on the symptoms reported by the individual rather than on objective diagnostic markers, and there is little empirical evidence for the optimal degree and duration of physical rest needed to promote recovery or the best timing and approach for returning to full physical activity. Sports-Related Concussions in Youth: Improving the Science, Changing the Culture reviews the science of sports-related concussions in youth from elementary school through young adulthood, as well as in military personnel and their dependents. This report recommends actions that can be taken by a range of audiences - including research funding agencies, legislatures, state and school superintendents and athletic directors, military organizations, and equipment manufacturers, as well as youth who participate in sports and their parents - to improve what is known about concussions and to reduce their occurrence. Sports-Related Concussions in Youth finds that while some studies provide useful information, much remains unknown about the extent of concussions in youth; how to diagnose, manage, and prevent concussions; and the short- and long-term consequences of concussions as well as repetitive head impacts that do not result in concussion symptoms. The culture of sports negatively influences athletes' self-reporting of concussion symptoms and their adherence to return-to-play guidance. Athletes, their teammates, and, in some cases, coaches and parents may not fully appreciate the health threats posed by concussions. Similarly, military recruits are immersed in a culture that includes devotion to duty and service before self, and the critical nature of concussions may often go unheeded. According to Sports-Related Concussions in Youth, if the youth sports community can adopt the belief that concussions are serious injuries and emphasize care for players with concussions until they are fully recovered, then the culture in which these athletes perform and compete will become much safer. Improving understanding of the extent, causes, effects, and prevention of sports-related concussions is vitally important for the health and well-being of youth athletes. The findings and recommendations in this report set a direction for research to reach this goal.
Author: Michelle Kyaw Nyein
Author: Michelle Kyaw Nyein
Author: Michelle Kyaw Nyein
Author: 
Author: Tyler Haladuick
Author: Robbin Elizabeth Bertucci
Author: Raj K. Narayan
Author: Cristina Morganti-Kossmann
Author: Daniel Laskowitz
Author: Talat Kiris
Author: National Research Council