Modeling and Simulation of Head Trauma Utilizing White Matter Properties from Magnetic Resonance Elastography

Abstract

Tissues of the brain, especially white matter, are extremely heterogeneous—with constitutive responses varying spatially. In this paper, we implement a high-resolution Finite Element (FE) head model where heterogeneities of white matter structures are introduced through Magnetic Resonance Elastography (MRE) experiments. Displacement of white matter under shear wave excitation is captured and the material properties determined through an inversion algorithm are incorporated in the FE model via a two-term Ogden hyper-elastic material model. This approach is found to improve model predictions when compared to experimental results. In the first place, mechanical response in the cerebrum near stiff structures such as the corpus callosum and corona radiata are markedly different compared with a homogenized material model. Additionally, the heterogeneities introduce additional attenuation of the shear wave due to wave scattering within the cerebrum.

Blunt head impact causes a temperature rise in the brain

“…The model has been previously validated for the case of pure mechanical response with good agreement with experimental studies [ 2 – 5 ]. In particular, we find that our linear model in [ 2 , 3 ] accurately captures the coup and counter-coup pressure response observed in the experiments performed by Nahum et al [ 13 ].…”

“…, where C NJ is the lumped capacitance matrix, P J (i) is the applied nodal source vector and F J (i) is the internal flux vector. Our finite-element (FE) head model [4,5] is segmented into standard tissue types through image segmentation-skull, cerebrospinal fluid (CSF), white matter and grey matter. The resolution of each voxel is taken directly from the imaging resolution.…”

“…Modern models are based on magnetic resonance imaging (MRI) and, providing a sufficiently fine spatial resolution, detailed stress and displacement wave patterns can be obtained [ 3 , 4 ]. Most recently, additional aspects of TBIs have been uncovered due to the introduction of magnetic resonance elastography (MRE) [ 5 ]. Most importantly this allows models to accurately capture heterogeneities in white matter tracts of the cerebrum.…”

“…Our finite-element (FE) head model [ 4 , 5 ] is segmented into standard tissue types through image segmentation—skull, cerebrospinal fluid (CSF), white matter and grey matter. The resolution of each voxel is taken directly from the imaging resolution.…”

“…The thermal properties of the tissues are presented in table 2 .

Figure 1 Finite-element model [ 3 – 5 ]. ( a ) Transverse (axial) section depicting different element types.

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