Measurement of brain biomechanics in vivo by magnetic resonance imaging

Computer models of head-brain biomechanics offer enormous potential for improved understanding and prevention of traumatic brain injury (TBI). However existing computer models remain controversial because their predictions have yet to be rigorously compared to measured biomechanical data. The nonlinear, anisotropic, viscoelastic, heterogeneous character of brain tissue, and the intricate connections between the brain and skull, all complicate modeling efforts. In order to make progress toward the goal of accurate simulation of TBI, experimental techniques to address these issues must be developed. In this paper we describe two magnetic resonance (MR) imaging techniques to characterize brain deformation, estimate brain material properties, and illuminate the boundary conditions between brain and skull. MR tagging is used to estimate displacement and strain fields in response to rigid-body acceleration of the skull, and MR elastography is used to visualize shear wave propagation induced by oscillatory loading at the surface of the skull.