Development of repetitive traumatic brain injury risk function based on real-world accident reconstruction and wavelet packet energy analysis

Tao Xiong ¹ Qinghang Luo ¹ Qiuju Chen ¹ Liangliang Shi ² Aowen Duan ³ Shengxiong Liu ^1* Kui Li ^4*

• ¹ School of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, China
• ² China Automotive Engineering Research Institute Co., Ltd, Chongqing, China
• ³ Department of Medical Engineering, Daping Hospital, Army Medical University, Chongqing, China
• ⁴ College of Medical Information, Chongqing Medical University, Chongqing, China

Existing evaluation criteria for pedestrian head impact injury only focus on single impact, and less attention has been paid to repetitive traumatic brain injury (rTBI), which is common in motor vehicle collisions, falls, and sports.Improving pedestrian collision protection safety requires a complete understanding of the tolerance of the repeated collisions of the human brain to injury. Therefore,this study was to collect data from 72 pedestrian collisions that were reconstructed using MADYMO and THUMS finite element head models(version 4.0.2). The evaluation metrics for rTBI were developed by integrating brain injury criteria based on time-domain features, including the Head Injury Criterion (HIC), Brain Injury Criterion (BrIC), Diffuse Axonal Multi-Axis General Evaluation (DAMAGE), and Maximum Principal Strain (MPS), with frequency-domain features obtained from wavelet packet transform energy analysis of head motion responses.The proposed brain tolerance for mild and severe rTBI was estimated through parametric survival analysis and presented as injury risk curves based on the selected injury metrics. Results showed a significant difference in brain injury tolerance between repetitive and single collisions. For the 50% probability of mild and severe brain injury in real accidents, the thresholds for rTBI metrics based on BrIC and DAMAGE were 1.085 and 1.513, and 0.494 and 0.678, respectively, all higher than the thresholds of single-impact reported in previous studies. However, the thresholds for repetitive head injury criteria based on MPS were 0.604 and 0.838, lower than the thresholds of single-impact reported in previous studies, which implies that the prediction of tolerance to repetitive brain injury is more consistent with tissue kinematics than head kinematics. This study developed injury risk functions (IRFs) for rTBI by integrating the amplitude-frequency characteristics of head responses and brain injury criteria. This knowledge further provides crucial support for understanding the tolerance to rTBI and enhancing pedestrian safety.