A Pre-computed Brain Response Atlas for Instantaneous Strain Estimation in Contact Sports

Abstract

Finite element models of the human head play an important role in investigating the mechanisms of traumatic brain injury, including sports concussion. A critical limitation, however, is that they incur a substantial computational cost to simulate even a single impact. Therefore, current simulation schemes significantly hamper brain injury studies based on model-estimated tissue-level responses. In this study, we investigate the feasibility of a pre-computed brain response atlas (pcBRA) to substantially increase the simulation efficiency in estimating brain strains using isolated rotational acceleration impulses parameterized with four independent variables (peak magnitude and duration, and rotational axis azimuth and elevation angles) with values determined from on-field measurements. Using randomly generated testing datasets, the partially established pcBRA achieved a 100% success rate in interpolation based on element-wise differences in accumulated peak strain (εp) according to a “double-10%” criterion or average regional εp in generic regions and the corpus callosum. A similar performance was maintained in extrapolation. The pcBRA performance was further successfully evaluated against responses directly simulating two independently measured typical real-world rotational profiles. The computational cost to estimate element-wise whole-brain or regional εp was 6 sec and <0.01 sec, respectively, vs. ~50 min directly simulating a 40 ms impulse. These findings suggest the pcBRA could substantially increase the throughput in impact simulation without significant loss of accuracy from the estimation itself and, thus, its potential to accelerate the exploration of the mechanisms of sports concussion in general. If successful, the pcBRA may also become a diagnostic adjunct in conjunction with sensors that measure head impact kinematics on the field to objectively monitor and identify tissue-level brain trauma in real-time for “return-to-play” decision-making on the sideline.

White Matter Injury Susceptibility via Fiber Strain Evaluation Using Whole-Brain Tractography

“…4a) were selected from an existing pre-computed brain response atlas (pcBRA 32,46 ). The pcBRA employs triangulated a rot impulses applied to the head center of gravity (skull, scalp, and facial components were simplified as rigid bodies).…”

“…9). In addition, a pre-computation strategy may also be effective in the context of contact sports, 32,46 because the head's impact temporal characteristics appear largely similar within or across subjects. 50,51 On the other hand, when using realistic head impacts as model inputs, tract-specific injury susceptibility indices could allow assessment of the relative injury vulnerabilities of neural pathways to identify the most vulnerable ones in real-world injury scenarios.…”

“…Second, although the baseline DHIM is subject-specific, we intend to use it for population-based studies as well-e.g., via the pre-computed brain response atlas (pcBRA 32,46,76 ). Unfortunately, a detailed population-based, ''average'' DTI or tractography atlas appears unavailable, and it is not feasible to create a subject-specific pcBRA for each athlete (e.g., hundreds), at least at present.…”

Real-time, whole-brain, temporally resolved pressure responses in translational head impact

“…by the azimuth (u) and elevation (a) angles. However, this requires 145 (13 2 -12 Â 2) unique atlas solutions to sample one-half of the symmetric parametric space (assuming a 158 sampling density for u and a, and further accounting for duplicated responses when a degenerates to +908, analogous to that in [24]). …”

“…This challenge may be addressed using a pre-computation strategy. Using a pre-computed brain response atlas ( pcBRA), (near) real-time estimation of brain strains was possible without significant loss of accuracy in the context of contact sports because of their similar temporal characteristics [24,25].…”