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 McKelvey School of Engineering at Washington University in St. Louis promotes independent inquiry and education with an emphasis on scientific excellence, innovation and collaboration without boundaries. McKelvey Engineering has top-ranked research and graduate programs across departments, particularly in biomedical engineering, environmental engineering and computing, and has one of the most selective undergraduate programs in the country. With 140 full-time faculty, 1,387 undergraduate students, 1,448 graduate students and 21,000 living alumni, we are working to solve some of society’s greatest challenges; to prepare students to become leaders and innovate throughout their careers; and to be a catalyst of economic development for the St. Louis region and beyond.