The ratio indicated a dramatic difference in brain deformation in response to lateral skull motion (“no” rotation) compared to occipital excitation (“yes” nodding). Okamoto and her co-authors found that the ratio SE/KE was a revealing index for how vulnerable the brain is to skull motion. The research team imaged the waves produced at different vibration frequencies and determined the kinetic energy (KE), how much energy was transferred to the head, and the strain energy (SE), the energy of brain deformation. (Credit: Bayly lab)ĭuring the experiment, volunteers had their skulls vibrated either from the back of the head, as in a “yes” nodding motion, or from the right side of the head, as in a “no” neck rotation. SE/KE is also higher at low-frequency vibrations. The ratio of strain energy to kinetic energy (SE/KE) is higher for lateral motion or shaking the head “no” (C) than for occipital motion or nodding “yes” (B). It’s the same kind of thing, except in our case the waves come inward from the skull.” “When we jiggle your head in the MRI machine, we can actually see motion of the brain, and it looks like waves, like when you throw a pebble in the water and the waves move outward. “In this experiment, we’re doing a safe test - gently vibrating your head back and forth like a bowl of gelatin - to gather information about how stiff the brain is and how it moves so we can make better computer models,” Okamoto said. Bayly, the Lee Hunter Distinguished Professor and chair of the Department of Mechanical Engineering & Materials Science, and their collaborators present new data about what happens when the head is jiggled at various frequencies in two directions. In new research published online July 11 in the ASME Journal of Biomechanical Engineering, Okamoto, Philip V. Instead, Okamoto and her colleagues use magnetic resonance elastography (MRE), a non-invasive imaging technique that can map the elastic properties and stiffness of soft tissues, to illuminate key mechanical characteristics of the brain’s response to skull motion. “You can’t study traumatic brain injury by running around hitting people on the head,” said Ruth Okamoto, teaching professor in mechanical engineering & materials science in the McKelvey School of Engineering at Washington University in St. Researchers are learning more about what leads to traumatic brain injury, though they have to be creative to work around limited access to the brain.
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