Mechanotransduction of Head Impacts to the Brain Leading to TBI: Histology and Architecture of Subarachnoid Space
Item
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Title
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Mechanotransduction of Head Impacts to the Brain Leading to TBI: Histology and Architecture of Subarachnoid Space
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Identifier
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d_2009_2013:6fa7bce9a106:11102
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identifier
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11373
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Creator
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Saboori, Parisa,
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Contributor
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Ali Sadegh
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Date
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2011
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biomedical engineering | Mechanical engineering | Brain | Histology | Impacts | Mechanotransduction | SAS | TBI
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Abstract
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Traumas involving vehicular collisions, contact sports or falls could cause relative motion between the brain and the skull leading to Traumatic Brain Injury (TBI). It has been shown that subarachnoid space (SAS) trabeculae play an important role in damping and reducing the relative movement of the brain with respect to the skull, thereby reducing traumatic brain injuries (TBI), (Zoghi and Sadegh 2010). The histology, architecture and mechanical properties of the SAS are not well established in the literature. A few investigators have estimated the mechanical properties of trabeculae based on the collagen's properties, i.e. Zhang et al (2001-2002) and Jin X et al. (2006). There is a wide range of reported values of the elastic modulus of the trabeculae up to three orders of magnitudes. Previous investigators have over simplified the complex architecture of the SAS trabeculae and have employed soft solid materials for the SAS which may have led to unreliable results.;The goal of this thesis was to investigate the mechanotransduction of head impacts to the brain with the emphasis on the role of material modeling of the subarachnoid space. This was accomplished through three aims. The first aim of this study was to investigate the histology and architecture of the SAS and in particular the trabeculae. This step was accomplished through several experimental studies including, Micro CT Scan, Histology sectioning, Two-Photon Microscopy (TPM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It was concluded that the trabeculae are collagen based Type I, Kierszenbaum 2007, Van Der Rest (1991), and their architectures are in the form of tree-shaped rods, pillars, plates and, in some regions, in the form of a complex network.;The second aim of this study was to determine the stress/strain changes in the brain as a function of the material properties of the SAS. The 2D and 3D local models of the SAS were created and the effect of the SAS material properties on transferring the external load to the brain was investigated. A wide range of the mechanical properties of the trabeculae were employed and based on the validation of the models with experimental results of Sabet et al. (2009), the mechanical properties of the SAS trabeculae were determined. The result indicated that when we use soft material properties for the trabeculae the meningeal layers absorb and damp the impact load. It is also concluded that the trabeculae can be simulated as tension elements since they buckle with minimal compressive load. In addition, the mechanotransduction of the external load to the brain, through two basic local models was investigated. It was shown that, the tree-shaped orientation of the trabecula provides more protection (less strain) for the brain tissue when the head in subjected to impacts.;The third aim of this study was to create a 3D head model and study the effect of external head impacts on the strain in the brain, leading to traumatic brain injury. A three-dimensional (3D) model of the head-neck was created and was validated against the experimental study of Feng et al (2010). The results indicate that the elastic modules of E=1000 Pa is a realistic value for the SAS. The effect of the different types of material modeling of SAS on transferring the load to brain was studied and was compared with the experimental study of Feng et al (2010). Finally, the 3D head model was subjected to a series of impact velocities and the strain in the brain as a function of applied velocity impact were determined. It has been concluded that, for the impact velocity range of 17--27 MPH, the strain in the brain varied 12--17%. The strain range is less than the 20% threshold of Traumatic Brain Injury (TBI) addressed in the literature, Meany et al. (1995) and Bayly et al. (2003). In addition, the strain in the brain is proportional to the applied impact velocity and the severity of TBI. This thesis reveals that the choice of material modeling and material properties of the meningeal layers are significant factors in determining the strain in the brain and therefore understanding different types of the head/brain injuries.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
