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Measuring with and against the grain

Engineers developing new way to analyze brain behavior during trauma

Learning more about how the brain responds to force could lead to better diagnosis and treatments for traumatic injuries. Engineers at Washington University in St. Louis are honing in on a new way to accurately assess the effects of forces during a traumatic brain injury, or TBI.

At left is a standard MRI image of the brain anatomy. The middle image shows a color-coded image of fiber direction in the brain, and at right is an MRI image of shear waves in the brain, induced to prove the properties of brain tissue. (Ruth Okamoto)

They’re focusing on measuring the brain’s anisotropy, or directional stiffness and strength. Much like a piece of wood, our brains have fibers which may impart extra strength along a specific direction, or grain. Researchers with the School of Engineering & Applied Science and the School of Medicine plan to use magnetic resonance imaging and focused ultrasound to better study the anisotropic behavior of brain tissue during trauma and mechanical stress.

“What we eventually want to do in brain trauma prevention is develop computer simulations which can tell us how the injury occurs, what parts of the brain get injured and what preventative measures might make a difference,” said Phil Bayly, the Lilyan & E. Lisle Hughes Professor of Mechanical Engineering at the School of Engineering & Applied Science. “To do that, you have to have a good mechanical model and to make that, you must have good measurements of a variety of factors, including anisotropy.”

The National Science Foundation recently awarded Bayly and his collaborators a 3-year $467,000 grant to develop and validate the new measurement method.

Working with Hong Chen, assistant professor of biomedical engineering and assistant professor of radiation oncology at the School of Medicine, and Joel Garbow, professor of radiology at the School of Medicine, Bayly plans to use focused ultrasound to remotely and non-invasively apply a force deep in the tissue, and then measure how the resulting acoustic waves travel. The researchers will repeat this in a variety of materials, including collagen and fibrin gels that have been magnetically aligned to mimic the anisotropy of natural tissues.

“What we plan to do is use that focused ultrasound force to generate waves deep in the tissue, and then observe the effects” Bayly said.

“It’s like throwing a pebble in a pond and watching the waves move outward. In this case, the pebble is the focused ultrasound, and we’re watching how the waves move directionally.”

By better understanding how anisotropy influences the brain’s motion, scientists believe better computer models can be developed to predict and diagnose brain trauma. The work also lays the foundation for developing new, engineered biomaterials to replace or repair soft tissues.

“We want to help modelers understand the mechanical behavior of tissue better than they do now,” said Bayly. “That’s the big picture goal.”


The School of Engineering & Applied Science at Washington University in St. Louis focuses intellectual efforts through a new convergence paradigm and builds on strengths, particularly as applied to medicine and health, energy and environment, entrepreneurship and security. With 94 tenured/tenure-track and 28 additional full-time faculty, 1,300 undergraduate students, 1,200 graduate students and 20,000 alumni, we are working to leverage our partnerships with academic and industry partners — across disciplines and across the world — to contribute to solving the greatest global challenges of the 21st century.



Collaborators

Professor
Mechanical Engineering & Materials Science

Hong Chen
Assistant Professor
Biomedical Engineering

Professor of Radiology