In silico investigation of brain tissue responses associated with mild blast traumatic brain injury

Blast induced traumatic brain injury (bTBI) is a significant concern in the era of tactical warfare. The biomechanical response of the human head to blast loading is actively sought. While blast wave propagation through brain tissue is reasonably well understood, the direct relationship between external blast parameters and brain biomechanical responses remains unclear. In this study, a 3D computational human model was used to investigate these relationships under free-field blast conditions relevant to mild bTBI, with peak incident pressure (IOP:70-145 kPa) and positive phase duration (PPD:2-8 ms). The blast wave head interactions were modeled using the conventional weapon (ConWep) technique for a duration of 80 ms. Front and side orientations were considered. The interaction of the blast wave with the human head induced a biomechanical cascade within the brain, which can be broadly categorized into wave propagation and inertial effects. Each of these effects had a peculiar timescale and induced distinct biomechanical signatures. The relationship between external blast parameters and brain biomechanical parameters indicated that brain pressure and the maximum principal strain rate (MPSR) were correlated with peak IOP, whereas equivalent stress and the maximum principal strain (MPS) were correlated with blast impulse. These correlations were specifically governed by the wave propagation and inertial effects, respectively. An increase in PPD had a more deleterious effect than an increase in peak IOP. Brain biomechanical responses produced higher values in the side orientation than in the front orientation, particularly affecting midbrain regions, including the corpus callosum (CC). Brain region specific analysis revealed that pressure was concentrated in the cerebrum (C), whereas equivalent stress and MPS were concentrated in CC. Comparison with blunt TBI suggested similarities in the spatiotemporal evolution of equivalent stress and MPS, but differences in pressure evolution. Overall, these results provide important new insights into the brain's response to the blast and enhance the overall mechanistic understanding of bTBI.