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Author: Sahil Kulkarni Publisher: ISBN: Category : Languages : en Pages : 224
Book Description
The use of body armor and combat helmets has reduced fatalities from explosions and ballistic attacks. However, frequent use of improvised explosive devices and continuing efforts to reduce the weight of each combat helmet have increased the risk of ballistic-impact and blast-induced traumatic brain injuries among soldiers. The objective of this dissertation research project is to develop predictive constitutive and computational models to be used in head injury diagnosis and to aid in the development of new combat helmets that can mitigate non-penetrating head injuries. A transversely isotropic visco-hyperelastic constitutive model is provided for soft tissues, which accounts for large deformations, high strain rates, and short-memory effects. The presented model is tested for a range of strain rates and for multiple loading scenarios based on available experimental data for porcine and human brain tissues. Using this constitutive relation, a finite element model of a helmet/head assembly is developed to study non-penetrating TBI. The effects of constitutive models and blast directions on finite elements simulations of blast induced TBI are investigated. Further, the effectiveness of combat helmets against non-penetrating TBI induced by blast and ballistic impacts is studied. Two types of combat helmets are considered: the advanced combat helmet (ACH) and the enhanced combat helmet (ECH). Spatial distributions and temporal variations of the intracranial pressure and stress components obtained in the simulations reveal significant differences in brain tissue responses to different constitutive models and blast directions. It is found that these combat helmets provide some level of protection against non-penetrating TBI and that the level of protection is higher for the ECH than the ACH. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151836
Author: Sahil Kulkarni Publisher: ISBN: Category : Languages : en Pages : 224
Book Description
The use of body armor and combat helmets has reduced fatalities from explosions and ballistic attacks. However, frequent use of improvised explosive devices and continuing efforts to reduce the weight of each combat helmet have increased the risk of ballistic-impact and blast-induced traumatic brain injuries among soldiers. The objective of this dissertation research project is to develop predictive constitutive and computational models to be used in head injury diagnosis and to aid in the development of new combat helmets that can mitigate non-penetrating head injuries. A transversely isotropic visco-hyperelastic constitutive model is provided for soft tissues, which accounts for large deformations, high strain rates, and short-memory effects. The presented model is tested for a range of strain rates and for multiple loading scenarios based on available experimental data for porcine and human brain tissues. Using this constitutive relation, a finite element model of a helmet/head assembly is developed to study non-penetrating TBI. The effects of constitutive models and blast directions on finite elements simulations of blast induced TBI are investigated. Further, the effectiveness of combat helmets against non-penetrating TBI induced by blast and ballistic impacts is studied. Two types of combat helmets are considered: the advanced combat helmet (ACH) and the enhanced combat helmet (ECH). Spatial distributions and temporal variations of the intracranial pressure and stress components obtained in the simulations reveal significant differences in brain tissue responses to different constitutive models and blast directions. It is found that these combat helmets provide some level of protection against non-penetrating TBI and that the level of protection is higher for the ECH than the ACH. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151836
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 : 25
Book Description
The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm3 voxels), 5 material model of the human head was created by segmentation of color cryosections from the Visible Human Female dataset. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior and lateral directions. Three dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric (shear) stress within the first 2 milliseconds of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 msec time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.
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: Firas H. Kobeissy Publisher: CRC Press ISBN: 1466565993 Category : Medical Languages : en Pages : 718
Book Description
With the contribution from more than one hundred CNS neurotrauma experts, this book provides a comprehensive and up-to-date account on the latest developments in the area of neurotrauma including biomarker studies, experimental models, diagnostic methods, and neurotherapeutic intervention strategies in brain injury research. It discusses neurotrauma mechanisms, biomarker discovery, and neurocognitive and neurobehavioral deficits. Also included are medical interventions and recent neurotherapeutics used in the area of brain injury that have been translated to the area of rehabilitation research. In addition, a section is devoted to models of milder CNS injury, including sports injuries.
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: Soroush Assari Publisher: ISBN: Category : Languages : en Pages : 91
Book Description
The focus of this dissertation was the biomechanics of blast-induced traumatic brain injury (bTBI). This study had three specific aims. One of the specific aims was to investigate the thoracic mechanism of bTBI by characterizing the cerebral blood pressure change during local blast exposure to head or chest in a rat model. This model utilized a shock tube to simulate the blast wave. The results showed that there is a blood pressure rise with high amplitude and short duration during both Head-Only and Chest-Only exposure conditions. It was shown that cerebral blood pressure rise was significantly higher in Chest-Only exposure, and resulted in astrocyte reactivation, and infiltration of blood-borne macrophages into the brain. It was concluded that due to chest exposure to a blast wave, high amplitude pressure waves that transfer from thoracic large vessels to cerebrovasculature can lead to blood-brain barrier disruption or perivascular injury and consequently trigger secondary neuronal damage. The second and third aims were related to the viscoelasticity and heterogeneity of brain tissue respectively for blast rate loading conditions. For the second specific aim, a novel test method was developed to apply shear deformation to samples of brain tissue with strain rates in the range of 300 to 1000 s-1. The results of shear tests on cylindrical samples of bovine brain showed that the instantaneous shear modulus (about 6 kPa) increased about 3 times compared to the values reported in the literature. For the third specific aim, local viscoelastic behavior of rat brain was characterized using a micro-indentation setup with the spatial resolution of 350 mm. The results of micro-indentation tests showed that the heterogeneity of brain tissue was more pronounced in long-term shear moduli. Moreover, the inner anatomical regions were generally more compliant than the outer regions and the gray matter generally exhibited a stiffer response than the white matter. The results of this study can enhance the prediction of brain injury in finite element models of TBI in general and models of bTBI in particular. These results contribute to development of more biofidelic models that can determine the extent and severity of injury in blast loadings. Such predictions are essential for designing better injury mitigation devices for soldiers and also for improving neurosurgical procedures among other applications.
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: Institute of Medicine Publisher: National Academies Press ISBN: 0309124085 Category : Medical Languages : en Pages : 396
Book Description
The seventh in a series of congressionally mandated reports on Gulf War veterans health, this volume evaluates traumatic brain injury (TBI) and its association with long-term health affects. That many returning veterans have TBI will likely mean long-term challenges for them and their family members. Further, many veterans will have undiagnosed brain injury because not all TBIs have immediately recognized effects or are easily diagnosed with neuroimaging techniques. In an effort to detail the long term consequences of TBI, the committee read and evaluated some 1,900 studies that made up its literature base, and it developed criteria for inclusion of studies to inform its findings. It is clear that brain injury, whether penetrating or closed, has serious consequences. The committee sought to detail those consequences as clearly as possible and to provide a scientific framework to assist veterans as they return home.
Author: Sahil Kulkarni
Author: Sahil Kulkarni
Author: Michelle Kyaw Nyein
Author: 
Author: Daniel Laskowitz
Author: Firas H. Kobeissy
Author: Michelle Kyaw Nyein
Author: Cristina Morganti-Kossmann
Author: Soroush Assari
Author: Talat Kiris
Author: Institute of Medicine