A brain sits on a pedestal, exploding into parts and particles as a polymer rod slams into it. Gray and white matter crumple against the wall. Splat. The mist that hangs in the air is very distinct since the video is shown in slow motion on a large projection screen.
“So that’s an actual experiment to show how traumatic impact affects the brain,” Raj Prabhu explained, chuckling at the horrified look on my face.
The group has developed a virtual model of the human brain and surrounding structures that shows how shockwaves travel through the hard skull, as well as the soft tissue. This challenges the accepted model of brain injury that has been in place for more than 20 years.
“Current thinking is that the vibrations from a head injury go through the skull at the point of impact then reverberate through the soft tissue until they dissipate,” Prabhu said. “Our model has been able to capture a level of detail that shows these waves actually travel around the skull then through the brain, which changes our understanding of where, when and how injuries occur.”
Associate professor Jun Liao added, “This changes the paradigm around brain injury.”
Experiments like the one in the video typically use animal models or synthetic materials to approximate the reaction that would occur in human tissue. These results are good for showing an overview of the damage—this is your brain; this is your brain in a helmetless collision—but they don’t capture the more subtle injuries that occur within the cranium.
“These alternative models lack the geometrical and biochemical processes that are present in human bodies,” Prabhu explained. “We wanted to study what happens to actual human tissue at each scale, from the individual atoms to the tissue as a whole, and that’s exactly what we’re doing.”
The Bagley College team’s model depicts the structures of the human brain, from the smallest atom at the microscale to the tissue that can be seen with the naked eye. By applying the physical properties of human tissue to its digital double, the researchers can then run simulations of different types of trauma to see exactly how it affects the brain at all levels.
“Our virtual brain is the most accurate solution to show what happens to all of the tissue when a trauma occurs,” Prabhu said. “By using multiscale modeling, we’ve been able to capture the physics and biomechanics that occur across the board, which will allow us to see what kinds of impacts cause injury and where those injuries occur.”
Multiscale modeling is a common practice in studies of composite materials and automotive structures, but has not been widely applied to developing high-fidelity human models. Because it is so new to the field, biological researchers are required to learn a whole new language and approach to their studies.
Prabhu pulls up the model on the screen to help me understand exactly what I’m hearing. It looks like a head that has been constructed using tiny versions of a kid’s toy building blocks. Known as a mesh, it is an illustration of layers and layers of the “tiny blocks,” that are correctly known as elements.
Each layer of the mesh represents a biological structural level—from the molecules that form the cells that form the nerves, veins, neurons, fat, and cartilage that form the brain, skull and surrounding tissue. The mesh contains 10 of these levels and is composed of one million elements.
At that rate, a whole human body constructed using the team’s method would contain close to 10 million elements. By comparison, a similar body model used by a car company contains 100,000.
Simulations using the current BCoE-developed model take approximately 10 hours to run and have to be processed through parallel computing—a process that requires the processors of multiple computers to analyze complex computational problems.
“We’re going against the grain and some people won’t see the need for these complex models since there are other models in existence, but those are very simplistic. Our models will help us understand so much more,” said Lakiesha Williams, an assistant professor.
Williams, Prabhu and Liao serve as co-leaders of the human body simulation team, each providing different biological engineering expertise, which helps ensure that their findings are thorough and fully validated. In the case of the virtual brain, the team members combined their research specialties and laboratories at Mississippi State’s agricultural and biological engineering department and the Center for Advanced Vehicular Systems to prepare the development for publication.
Prabhu, now an assistant research professor, began the multiscale modeling process as a doctoral student under the guidance of Mark F. Horstemeyer, a professor in mechanical engineering. Liao, who specializes in tissue engineering, then helped ensure the accuracy of the biological properties assigned to the model in simulations. The virtual model was validated through physical experiments conducted by Williams, who researches tissue and organ mechanics.
“We’ve been validating the model at every step along the way so that we can be confident in our model by the time we get to the full-scale,” Williams said.
The team’s work has been supported by approximately $2 million from various agencies and organizations, including the Department of Defense, which also is supporting their work to develop similar models of the lower extremities: legs, ankles and feet. Williams serves as principal investigator on that project.
The group’s goal is to eventually complete a multiscale-model of the whole human body.
“We’ve developed the science and engineering framework that will allow us to develop a virtual human that can be used in simulating any traumatic situation,” Williams said. “And ultimately, these high fidelity models will help us develop more effective safety counter-measures.”
She continued, “Crash-test dummies are made of plastic and steel. Those materials don’t react like the human would. Our models will allow for bio-inspired design that takes into account actual human properties from the beginning of the product design process, and that will lead to safer conditions for all of us.”