Past Event: Oden Institute Seminar

Development of a Biofidelic Material Model for Brain Tissue to Model the Response of Human Head to Impact Loads

David Littlefield, Professor, Mechanical Engineering, University of Alabama at Birmingham

Abstract

The development of a finite element model capable of predicting brain injury sustained as a result of an impact load to the head is of considerable importance not only for the development of adequate protection systems but also in deciding an appropriate mode of treatment for an individual. With advancements in imaging technologies, it is now possible to visualize the neuron fiber structures in the brain. A microscale model was developed from the individual isotropic behaviors of the CSF and brain tissue present in the brain such that the resultant behavior of the material is transverse isotropic. To capture the presence of neuron fibers in the brain, the data obtained from Diffusion Tensor MRI(DTI) was incorporated into the finite element model so that, based on the fiber direction in each voxel, the material model was suitably applied to behave as a transverse isotropic material. The use of DTI data in conjunction with the transverse isotropic material model is a novel approach that has not been attempted so far because the material data available for brain tissue are mostly isotropic in character. Use of the model immediately remedies some of the most basic flaws present in simpler isotropic elastic or viscoelastic material descriptions of brain tissue. For example, the wave speed in brain tissue is typically an order of magnitude faster than predicted by simple isotropic descriptions (this is an artifact caused by the artificial compliance enhancement needed to achieve reasonable deformation behavior). The current model, however, faithfully reproduces the correct wave speed. As a first step towards achieving our goal of having an anatomically correct and detailed finite element model, we have applied this microscale model to a simplified geometry of the human brain. Loading conditions from literature where experiments have been done on cadavers were used as a means of comparing predicted strains with the observed values.