Application of Diffusion Tensor Imaging in Modeling Diffuse Axonal Injury

Traumatic brain injury (TBI) is a debilitating injury that has received a lot of attention within the past few years partly as a result of the increased number of TBI incidents arising from military conflicts. Of the incidences of TBI, diffuse axonal injury (DAI) accounts for the second largest percentage of deaths [1]. DAI is caused by sudden inertial loads to the head, and it is characterized by damage to neural cells [2]. These inertial loads at the macroscale result in functional and structural damage at the cellular level. To understand the coupling between the mechanical forces and the functional damage of neurons, an analytical model that accurately represents the mechanics of brain deformation under inertial loads must be developed. It has been shown in clinical and experimental studies that the deep white matter of the brain is highly susceptible to injury [2]. Unlike the gray matter of the brain, the white matter structures contain an organized arrangement of neural axons and therefore can be considered anisotropic (Figure 1). To account for the anisotropic nature of the white matter in finite element simulations, the orientation of the neural axons must be incorporated into a material model for brain tissue. In this study, the use of diffusion tensor imaging (DTI) as a tool to provide fiber orientation information to continuum models is investigated. By incorporating fiber orientation data into a material model for white matter, the strains experienced by neural axons in the white matter tracts of the brain are computed, and this strain is related to cellular stretch thresholds of diffuse axonal injury.