Virtual Simulation of the Effects of Intracranial Fluid Cavitation in Blast-Induced Traumatic Brain Injury PDF Download
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Languages : en
Pages : 8
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Languages : en
Pages : 8
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Category :
Languages : en
Pages : 25
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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: Michelle Kyaw Nyein
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Category :
Languages : en
Pages : 113
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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.
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Languages : en
Pages : 1
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Author: Aravind Sundaramurthy
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ISBN: 9781321115475
Category : Brain
Languages : en
Pages : 197
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Blast induced neurotrauma (BINT) has been designated as the "signature injury" to warfighters in the recent military conflicts. In the past decade, conflicts in Iraq (operation Iraqi freedom) and Afghanistan (operation enduring freedom) as well as the increasing burden of the terrorism around the world resulted in an increased number of cases with blast Traumatic Brain Injury (bTBI). Recently, a lot of research has been done to study the neurological and neurochemical degenerations resulting from BINT using animal models especially rat models. However, it is not clear how and whether the biological outcomes from animal models can be translated to humans; this work is aimed to address this issue.
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Languages : en
Pages : 18
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Category :
Languages : en
Pages : 9
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Author: Suhas Vidhate
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Category : Electronic dissertations
Languages : en
Pages : 176
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Blast-induced traumatic brain injury (bTBI) has been widely accepted as a "signature" wound affecting military service members in modern conflicts. When a blast-wave generated by an improvised explosive device explosion propagates through the human head, it is hypothesized to cause direct mechanical damage to the brain tissue leading to vascular injury, cerebral edema as well as less detectable but persistent deficits. However, the exact mechanisms and pathophysiology of bTBI still remain poorly understood. One of the main reasons for such poor understanding is the technical challenge of reproducing the typical time-varying loading cycles induced on brain tissue after a blast event under controlled laboratory conditions. Blast events have a sub-millisecond onset of high pressure followed by complex dynamics resulting from the interaction between the blast wave and the intricate anatomical structure of the human head. This interaction gives rise to time-varying intracranial pressure profiles, dynamic shear loads, and cavitation events, which are hypothesized to cause mechanical insults to the brain tissue.To tackle these experimental challenges, we have developed four experimental devices that can reproduce the dominant intracranial effects induced by blast loading onto the brain. These experimental devices are: (1) Multi-material Hopkinson bar (MMHB) actuator, (2) Generator of broadband pressure cycles, (3) Rig for controlled-cavitation events, and (4) Generator of dynamic shear cycles. This dissertation details the design and development of the aforementioned experimental systems along with the preliminary ex-vivo and in-vitro experiments performed to test their applicability.The designed apparatuses are comparably inexpensive, compact, easily portable, and highly controllable, making them well suited for biomedical applications. These devices can be used to conduct ex-vivo and in-vitro experiments involving animal brain tissue specimens, cell cultures, and organoids to explore their pathophysiological response to the blast-like loadings observed during a bTBI event.
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Category :
Languages : en
Pages : 18
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Author:
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Category :
Languages : en
Pages : 17
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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.
