脳の力学特性と軸索の機能損傷のモデル化

概要

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Finite element analyses of brain are effective for investigation of traumatic brain injury mechanism. In past analyses, brain parenchyma has been generally modeled as isotropic materials with viscoelastic properties, and damage in axon, which is one of main causes of higher brain dysfunction, has not been modeled. In this study, we developed a new constitutive model representing the mechanical properties of the brain parenchyma and the evolution equation for the functional damage of the axon. A free energy function is described as the sum of volumetric elastic, isochoric elastic and isochoric viscoelastic parts. The isochoric viscoelastic part is modeled as a three-dimensional model constructed by extending the one-dimensional generalized Maxwell model. The functional damage of the axon was defined as the reduction of the conduction function of an axial fiber and modeled to reproduce the reduction of the action potential area under tensile tests. The proposed model well reproduced the properties reported by experimental researchers: anisotropy in cerebral white matter, strain rate dependency, tension-compression asymmetry, and functional damage of axon. The proposed model has the potential for better understanding of mechanism of traumatic brain injuries.