Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Mao, Haojie

Abstract

To better understand traumatic brain injury (TBI), it is necessary to correlate with injuries, which are observed from in vivo laboratory experiments, to brain mechanical responses, which can so far be best predicted by finite element (FE) models. Firstly, a previously validated FE model was improved to investigate the effect of repeated impacts and lateral movements on brain responses to ensure the accuracy and reproducibility of controlled cortical impact (CCI) across different labs. Then, a new FE mouse brain model with the detailed three-dimensional (3D), non-linear vasculature was developed to study how the vasculature affected brain response in CCI and predicted vasculature responses. Lastly, the correlation between brain mechanical strains and microvessel injury induced by CCI was investigated. In summary, the biomechanics of CCI was further characterized and a new mouse brain model with detailed vasculature was developed to understand brain mechanics and microvessel damage.

Summary for Lay Audience

To better understand traumatic brain injury (TBI), it is necessary to correlate with injuries, which are observed from in vivo laboratory experiments, to brain mechanical responses, which can so far be best predicted by finite element (FE) models. The efforts of developing high-quality finite element (FE) head models have been conducted to increase the understanding of brain injury mechanism. In previous FE models, the brain was modeled without the whole three-dimensional (3D) vasculature and the result of the structural influence of the vasculature was contradictory, mainly because the brain vasculature network is of high complexity and is difficult to investigate. Also, very little was known on how the vasculature affects brain response under the open-skull controlled cortical impact (CCI), which is one of the most widely used in vivo laboratory neurotrauma models to observe focal brain injuries. In order to better understand CCI, a previously validated FE mouse brain model was improved to investigate the effect of repeated impacts and lateral movements on brain responses during CCI. The repeated impacts had minimal effect on peak strains. The lateral movements of the tip, however, greatly increased brain strains and affected large brain regions. Hence, it is necessary to monitor and control lateral movements to ensure the accuracy and reproducibility of CCI, for which no existing CCI devices can deliver, posting an opportunity for future developments. Then, a new FE mouse brain model with the detailed 3D, non-linear vasculature was developed to study how the vasculature affected brain response in CCI and predicted vasculature responses. Interestingly, the contribution of the vasculature on brain strains in CCI was limited, with less than 5% of changes by comparing brain models with and without vasculature. Lastly, CCI is a focal injury that induces microvessel damage in the cortical region. Hence, the correlation between brain mechanical strains and microvessel injury in CCI was investigated. In summary, the biomechanics of CCI was further characterized and a new mouse brain model with detailed vasculature was developed to understand brain mechanics and microvessel damage.

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