In Vivo Measurement of Brain Biomechanics

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DESCRIPTION (provided by applicant): The overall objectives of this study are to develop and enhance technology to obtain in vivo data on acceleration-induced brain deformation, tissue mechanical properties, and brain-skull interaction. Computer models of head-brain biomechanics offer enormous potential for developing strategies to prevent or reduce traumatic brain injury (TBI), and for understanding the neurological sequelae of different mechanical insults. However existing models remain controversial because computer predictions have yet to be validated in vivo. The primary barrier to validation is the difficulty of direct measurement of brain deformation. The proposed project responds to PA-04-006 Neurotechnology Research, Development, and Enhancement by developing technology to improve our understanding of a major neurological health problem: TBI. The project is need-driven: the technological advances will provide much-needed data on brain biomechanics for the development and validation of reliable computer models of brain injury. Two Specific Aims are proposed: Aim 1: Obtain quantitative measurements of tissue deformation (strain) induced by head acceleration, using MR tagging in human and animal studies. Tagged MR images will be obtained during controlled accelerations of the in vivo human and porcine brains. Brain deformation (strain), as well as relative motion between the brain and skull, will be measured by tracking intersections of tag lines. Studies will also be performed in the in situ and isolated porcine brain for comparison to in vivo measurements. Aim 2: Obtain improved estimates of brain tissue mechanical parameters from MR elastography (MRE), combined with diffusion tensor imaging (DTI) of tissue anisotropy. The dynamic stiffness of brain tissue can be estimated non-invasively, in vivo, from MR measurement of elastic wave propagation. Mechanical parameters may be anisotropic. Anisotropy data obtained via DTI will be combined with MR elastography data to enable robust estimation of direction-dependent properties. Technology transfer: Experiments and data processing procedures will be designed to maximize accessibility and usefulness to the finite element (FE) modeling research community. The project involves a multi- disciplinary research team from Washington University and the University of Pennsylvania with expertise in solid mechanics, biomechanics, MR imaging, MR instrumentation, and FE modeling of TBI.