At Sandia, researchers created a computer model of a man's head and neck. The model includes the jaw, because a lot of blasts come from improvised explosive devices (IEDs) at ground level, sending waves traveling at the speed of sound through the jaw and facial structure before they reach the brain, Taylor said.
Sandia's team used the National Library of Medicine's Visible Human Project, which was established in 1989 to build a digital image library of volumetric data representing complete, normal adult male and female anatomy.
The researchers created geometric models of the seven tissue types in the human head—scalp, bone, white and gray brain matter, membranes, cerebral spinal fluid, and air spaces. Over a year, they catalogued each of the tissue types seen in about 300 "slices" of the cadaver's head, dividing what they saw into one-millimeter cubes and assigning each a tissue type for the computer simulation.
Computer simulations of a human's head viewed from above looking down (top row) and from the side (bottom row). The images show the deposition of compressive energy in the brain during frontal, rear and side blasts.
Credit: Sandia National Labs
Taylor also imported digitally processed, computed tomography scans of various helmet designs into the simulations to assess the protective merits of each against blast loading.
In a typical blast simulation, 96 processors on Sandia's Red Sky supercomputer take about a day to process a millisecond of simulated time and at least 5 milliseconds are required to capture a single blast event, Taylor said.
The 3-D simulations are visualized using two-dimensional multi-colored images of a man's head that record an enormous amount of data.
On the clinical side, Ford studied 13 subjects who suffered mild TBI after IEDs exploded near them. Some were stunned, most lost consciousness at least briefly, and most cannot hold a job, he said.
The research partners hope to recruit more patients, especially military veterans, who were exposed to blasts that did not penetrate the skin and who suffered a loss of consciousness, Ford says. Candidates must have no other history of significant blunt traumas.
Once Taylor and Ford determine exactly how and where the wave energy deposited in the brain gives rise to injuries, they can provide thresholds of stress and energy levels that cause TBI for consideration by helmet designers, Taylor said.
"I want us to be able to understand the physical mechanisms that lead to TBI. It would also be useful if we could make the connection between blast loading and blunt impact trauma," Taylor said. "Once we understand that we can be more comprehensive in how we protect both our warfighters and athletes against these sorts of injuries."
View a simulation of a traumatic brain injury below.