Non-Lethal Blasts can Generate Cavitation in Cerebrospinal Fluid While Severe Helmeted Impacts Cannot: A Novel Mechanism for Blast Brain Injury

Yu, Xiancheng; Nguyen, Thuy-Tien; Wu, Tianchi; Ghajari, Mazdak

doi:10.3389/fbioe.2022.808113

Cited by 3 publications

(3 citation statements)

References 35 publications

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“…Particularly, the anatomical features of the grey and white matter, such as sulci and gyri, are represented in detail, ensuring that the effects of these anatomical details are considered in the simulations. The material models and parameters of the various tissues are explained in detail in our previous study [ 18 , 25 , 27 ]. Using this head model, we simulated two tests that best replicated the damage on cyclist’s helmet.…”

Section: Methodsmentioning

confidence: 99%

In-Depth Bicycle Collision Reconstruction: From a Crash Helmet to Brain Injury Evaluation

Baker

Brown³

et al. 2023

Bioengineering

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Traumatic brain injury (TBI) is a prevalent injury among cyclists experiencing head collisions. In legal cases, reliable brain injury evaluation can be difficult and controversial as mild injuries cannot be diagnosed with conventional brain imaging methods. In such cases, accident reconstruction may be used to predict the risk of TBI. However, lack of collision details can render accident reconstruction nearly impossible. Here, we introduce a reconstruction method to evaluate the brain injury in a bicycle–vehicle collision using the crash helmet alone. Following a thorough inspection of the cyclist’s helmet, we identified a severe impact, a moderate impact and several scrapes, which helped us to determine the impact conditions. We used our helmet test rig and intact helmets identical to the cyclist’s helmet to replicate the damage seen on the cyclist’s helmet involved in the real-world collision. We performed both linear and oblique impacts, measured the translational and rotational kinematics of the head and predicted the strain and the strain rate across the brain using a computational head model. Our results proved the hypothesis that the cyclist sustained a severe impact followed by a moderate impact on the road surface. The estimated head accelerations and velocity (167 g, 40.7 rad/s and 13.2 krad/s2) and the brain strain and strain rate (0.541 and 415/s) confirmed that the severe impact was large enough to produce mild to moderate TBI. The method introduced in this study can guide future accident reconstructions, allowing for the evaluation of TBI using the crash helmet only.

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Section: Methodsmentioning

confidence: 99%

In-Depth Bicycle Collision Reconstruction: From a Crash Helmet to Brain Injury Evaluation

Baker

Brown³

et al. 2023

Bioengineering

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“…To evaluate the brain deformation from the tests, we used the Imperial College finite element (FE) model of the human head ( Ghajari et al, 2017 ; Yu et al, 2022b ) ( Figure 2D ). This model has a detailed definition of the head anatomy, including sulci and gyri, and its predictions of brain displacement have been validated against recent well-controlled experiments on postmortem human subject heads ( Fahlstedt et al, 2021 ; Zimmerman et al, 2021 ).…”

Section: Methodsmentioning

confidence: 99%

Oblique impact responses of Hybrid III and a new headform with more biofidelic coefficient of friction and moments of inertia

Halldin

Ghajari

2022

Front. Bioeng. Biotechnol.

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New oblique impact methods for evaluating head injury mitigation effects of helmets are emerging, which mandate measuring both translational and rotational kinematics of the headform. These methods need headforms with biofidelic mass, moments of inertia (MoIs), and coefficient of friction (CoF). To fulfill this need, working group 11 of the European standardization head protection committee (CEN/TC158) has been working on the development of a new headform with realistic MoIs and CoF, based on recent biomechanics research on the human head. In this study, we used a version of this headform (Cellbond) to test a motorcycle helmet under the oblique impact at 8 m/s at five different locations. We also used the Hybrid III headform, which is commonly used in the helmet oblique impact. We tested whether there is a difference between the predictions of the headforms in terms of injury metrics based on head kinematics, including peak translational and rotational acceleration, peak rotational velocity, and BrIC (brain injury criterion). We also used the Imperial College finite element model of the human head to predict the strain and strain rate across the brain and tested whether there is a difference between the headforms in terms of the predicted strain and strain rate. We found that the Cellbond headform produced similar or higher peak translational accelerations depending on the impact location (−3.2% in the front-side impact to 24.3% in the rear impact). The Cellbond headform, however, produced significantly lower peak rotational acceleration (−41.8% in a rear impact to −62.7% in a side impact), peak rotational velocity (−29.5% in a side impact to −47.6% in a rear impact), and BrIC (−29% in a rear-side impact to −45.3% in a rear impact). The 90th percentile values of the maximum brain strain and strain rate were also significantly lower using this headform. Our results suggest that MoIs and CoF have significant effects on headform rotational kinematics, and consequently brain deformation, during the helmeted oblique impact. Future helmet standards and rating methods should use headforms with realistic MoIs and CoF (e.g., the Cellbond headform) to ensure more accurate representation of the head in laboratory impact tests.

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“…The model consists of nearly one million hexahedral elements and a quarter of a million quadrilateral elements, representing 11 tissues, including the scalp, skull, brain, meninges, subarachnoid space, and ventricles. The details of the model development, mechanical properties of different tissues, and validation of the model predictions against sonomicrometry brain displacement data and intracranial pressure data from post-mortem human subject experiments can be found in [6,40,[50][51][52][53][54]. A non-linear transient dynamic code, LS-DYNA [55], was used to set up the model and solve the equations using 20 cores of a high-performance computer and 16 GB of RAM.…”

Section: The Finite Element Model Of the Human Brainmentioning

confidence: 99%

An Instrumented Mouthguard for Real-Time Measurement of Head Kinematics under a Large Range of Sport Specific Accelerations

Jones

Austin

Augustus

et al. 2023

Sensors

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Background: Head impacts in sports can produce brain injuries. The accurate quantification of head kinematics through instrumented mouthguards (iMG) can help identify underlying brain motion during injurious impacts. The aim of the current study is to assess the validity of an iMG across a large range of linear and rotational accelerations to allow for on-field head impact monitoring. Methods: Drop tests of an instrumented helmeted anthropometric testing device (ATD) were performed across a range of impact magnitudes and locations, with iMG measures collected concurrently. ATD and iMG kinematics were also fed forward to high-fidelity brain models to predict maximal principal strain. Results: The impacts produced a wide range of head kinematics (16–171 g, 1330–10,164 rad/s2 and 11.3–41.5 rad/s) and durations (6–18 ms), representing impacts in rugby and boxing. Comparison of the peak values across ATD and iMG indicated high levels of agreement, with a total concordance correlation coefficient of 0.97 for peak impact kinematics and 0.97 for predicted brain strain. We also found good agreement between iMG and ATD measured time-series kinematic data, with the highest normalized root mean squared error for rotational velocity (5.47 ± 2.61%) and the lowest for rotational acceleration (1.24 ± 0.86%). Our results confirm that the iMG can reliably measure laboratory-based head kinematics under a large range of accelerations and is suitable for future on-field validity assessments.

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Non-Lethal Blasts can Generate Cavitation in Cerebrospinal Fluid While Severe Helmeted Impacts Cannot: A Novel Mechanism for Blast Brain Injury

Cited by 3 publications

References 35 publications

In-Depth Bicycle Collision Reconstruction: From a Crash Helmet to Brain Injury Evaluation

In-Depth Bicycle Collision Reconstruction: From a Crash Helmet to Brain Injury Evaluation

Oblique impact responses of Hybrid III and a new headform with more biofidelic coefficient of friction and moments of inertia

An Instrumented Mouthguard for Real-Time Measurement of Head Kinematics under a Large Range of Sport Specific Accelerations

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