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St. Louis, MO, United States

Clayton E.H.,Aerospace and Structural Engineering | Wang Q.,Aerospace and Structural Engineering | Song S.K.,Brookings Biomedical | Okamoto R.J.,Aerospace and Structural Engineering | And 2 more authors.
Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2010 | Year: 2010

Magnetic resonance elastography (MRE) is a novel experimental technique for estimating the dynamic shear modulus of biological tissue in vivo and non-invasively. Propagating acoustic frequency shear waves are launched into biologic tissue via external mechanical actuator and a conventional magnetic resonance imaging (MRI) scanner is used to acquire spatial-temporal measurements of the wave displacement field with micron precision. Local shear modulus estimates are obtained by inverting the equations governing shear wave motion. Changes in tissue pathology may be accompanied by a stark change in tissue elasticity. As a result, MRE has appeal to healthcare practitioners as a non-invasive diagnostic tool. Recently, MRE-based modulus estimates have been obtained in animal liver, brain, and heart [2-7]. Here, for the first time, MRE was used to probe the shear modulus of mouse eye vitreous humor in vivo and non-invasively. © 2010 Society for Experimental Mechanics Inc.

Feng Y.,Aerospace and Structural Engineering | Abney T.M.,Aerospace and Structural Engineering | Okamoto R.J.,Aerospace and Structural Engineering | Pless R.B.,St. Louis | And 2 more authors.
Journal of the Royal Society Interface | Year: 2010

This study describes the measurement of fields of relative displacement between the brain and the skull in vivo by tagged magnetic resonance imaging and digital image analysis. Motion of the brain relative to the skull occurs during normal activity, but if the head undergoes high accelerations, the resulting large and rapid deformation of neuronal and axonal tissue can lead to long-term disability or death. Mathematical modelling and computer simulation of acceleration-induced traumatic brain injury promise to illuminate the mechanisms of axonal and neuronal pathology, but numerical studies require knowledge of boundary conditions at the brain-skull interface, material properties and experimental data for validation. The current study provides a dense set of displacement measurements in the human brain during mild frontal skull impact constrained to the sagittal plane. Although head motion is dominated by translation, these data show that the brain rotates relative to the skull. For these mild events, characterized by linear decelerations near 1.5g (g = 9.81 m s-2) and angular accelerations of 120-140 rad s-2, relative brain-skull displacements of 2-3 mm are typical; regions of smaller displacements reflect the tethering effects of brain-skull connections. Strain fields exhibit significant areas with maximal principal strains of 5 per cent or greater. These displacement and strain fields illuminate the skull-brain boundary conditions, and can be used to validate simulations of brain biomechanics. © 2010 The Royal Society.

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