The brain is the most critical organ of the human body as it controls motor function, information flow and body actions. Thus, the brain needs to be protected from trauma because injuries to the brain can be disastrous and cause a burden on society in terms of economy and emotions. According to the CDC data, over 280,000 people in the U.S. receive a motor vehicle induced traumatic brain injury every year. The National Highway Transportation Safety Administration (NHTSA) uses the Head Injury Criterion (HIC) as a federal rule for frontal and side impact head protection requirements. Recently by utilization of an advanced human head finite element (FE) model and simulation of animal brain injury data scaled to the human, a new BRain Injury Criterion (BrIC) was proposed by the NHTSA to complement the HIC. However, the accuracy of the methods for describing brain injury location, severity and pathology was limited and the scaling of the animal data to the human brain is questionable due to geometrical difference. To better correlate model-predicted response to rotational injury in the animal’s brain, it is required to numerically reconstruct those animal experiments to investigate the effect of angular accelerations of different planes on the severity and pathology of brain injuries with the help of the FE model of these specimens.

The objective of this thesis study was to develop tissue-level injury thresholds by using an animal FE modelling of in vivo injury which can be directly translated to a human head FE model without using scaling. The first aim of this thesis research includes the development of an anatomically detailed rhesus monkey brain FE model and the application of it to simulate in vivo (rhesus monkey) diffuse axonal injury in rotational experiments. The second aim was to develop tissue-level diffuse brain injury thresholds by correlating the FE model-predicted biomechanical response parameters to the foci of the histopathological changes sustained by in vivo (rhesus monkey) animals. The third aim was to translate the tissue-level diffuse brain injury thresholds directly to a human FE head model to predict rotational brain injury risk in human using real world injury data. Collectively, the research results questioned the validity and capability of the BrIC criterion, currently proposed by NHTSA, in predicting rotational brain injury.