Computational models are often used as tools to study traumatic brain injury. The fidelity of such models depends on the incorporation of an appropriate level of structural detail, the accurate representation of the material behavior, and the use of an appropriate measure of injury. In this study, an axonal strain injury criterion is used to estimate the probability of diffuse axonal injury (DAI), which accounts for a large percentage of deaths due to brain trauma and is characterized by damage to neural axons in the deep white matter regions of the brain. We present an analytical and computational model that treats the white matter as an anisotropic, hyperelastic material. Diffusion tensor imaging is used to incorporate the structural orientation of the neural axons into the model. It is shown that the degree of injury that is predicted in a computational model of DAI is highly dependent on the incorporation of the axonal orientation information and the inclusion of anisotropy into the constitutive model for white matter.

An axonal strain injury criterion for traumatic brain injury

A major role for the cerebrospinal fluid (CSF) is to provide effective damping against sudden intracranial brain motions during dynamic head impact. This paper examines the roles of CSF pro...

A finite element method parametric study of the dynamic response of the human brain with different cerebrospinal fluid constitutive properties.

Primary Objective: Closed brain injuries are a common danger in contact sports and motorized vehicular collisions. Mild closed brain injuries, such as concussions, are not easily visualized by comp...

Fluid-structure interaction analysis of cerebrospinal fluid with a comprehensive head model subject to a rapid acceleration and deceleration.

The rostral-caudally aligned fiber-reinforced structure of spinal cord white matter (WM) gives rise to transverse isotropy in the material. Stress and strain patterns generated in the spinal cord parenchyma following spinal cord injury (SCI) are multidirectional and dependent on the mechanism of the injury. Our objective was to develop a WM constitutive model that captures the material transverse isotropy under dynamic loading. The WM mechanical behavior was extracted from the published tensile and compressive experiments. Combinations of isotropic and fiber-reinforcing models were examined in a conditional quasi-linear viscoelastic (QLV) formulation to capture the WM mechanical behavior. The effect of WM transverse isotropy on SCI model outcomes was evaluated by simulating a nonhuman primate (NHP) contusion injury experiment. A second-order reduced polynomial hyperelastic energy potential conditionally combined with a quadratic reinforcing function in a four-term Prony series QLV model best captured the WM mechanical behavior (0.89 < R2 < 0.99). WM isotropic and transversely isotropic material models combined with discrete modeling of the pia mater resulted in peak impact forces that matched the experimental outcomes. The transversely isotropic WM with discrete pia mater resulted in maximum principal strain (MPS) distributions which effectively captured the combination of ipsilateral peripheral WM sparing, ipsilateral injury and contralateral sparing, and the rostral/caudal spread of damage observed in in vivo injuries. The results suggest that the WM transverse isotropy could have an important role in correlating tissue damage with mechanical measures and explaining the directional sensitivity of the spinal cord to injury.

The Transverse Isotropy of Spinal Cord White Matter Under Dynamic Load

Primary Objective: The interaction of cerebrospinal fluid with the brain parenchyma in an impact scenario is studied. Research Design: A computational fluid-structure interaction model is used to simulate the interaction of cerebrospinal fluid with a comprehensive brain model. Methods and Procedures: The method of smoothed particle hydrodynamics is used to simulate the fluid flow, induced by the impact, simultaneously with finite element analysis to solve the large deformations in the brain model. Main Outcomes and Results: Mechanism of injury resulting in concussion is demonstrated. The locations with the highest stress values on the brain parenchyma are shown. Conclusions: Our simulations found that the damage to the brain resulting from the contrecoup injury is more severe than that resulting from the coup injury. Additionally, we show that the contrecoup injury does not always appear on the side opposite from where impact occurs.

Mechanism of Coup and Contrecoup Injuries Induced by a Knock-Out Punch

The brain is the most important organ for life activity and humanity and is also an organ that tends to have residual disabilities after an accident because neuron cells cannot repair themselves. Therefore, protecting the brain from serious damage should be one of the most important objectives in automotive safety design for both passengers and pedestrians. For this reason, the Seikei University Graduate School and others have examined head impacts and the subsequent responses.

Impact Injury Analysis of the Human Head

In this paper, a three-dimensional digital human-head model was developed and several dynamic analyses on the head trauma were conducted. This model was built up by the VOXEL approach using 433 slice CT images (512×512 pixels) and made of 1.22 million parallelepiped finite elements with 10 anatomical tissue properties such as scalp, CSF, skull, brain, dura mater and so on. The numerical analyses were conducted using a finite element code the authors have developed. The main features of the code are 1) it is based on the explicit time integration method and 2) it uses the one point integration method to evaluate the equivalent nodal forces with the hourglass control proposed by Flanagan and Belytschko(1) and 3) it utilizes the parallel computation system based on MPI. In order to verify the developed model, the head impact experiment for a cadaver by Nahum et al.(2) was simulated. The calculated results showed good agreement with the experimental ones. A front and rear impact analyses were also performed to discuss on the characteristic measure of the brain injury, in which the von-Mises stress was high in the frontal lobe in both of the analyses because of the large deformations of a frontal cranial base. This result suggests that the von-Mises stress can be a good measure of the brain injury since it is empirically well known that the frontal lobe tends to get injured regardless of the impact positions.

Development of a Human Head FE Model and Impact Simulation on the Focal Brain Injury

The simulation of the head subjected to the impact acceleration was conducted to understand the mechanism of a diffuse axonal injury. It is known that the diffuse axonal injury frequently occurs in motor vehicle accidents. Gennarelli et al. proposed that a diffuse axonal injury occurs while a head is subjected to rather a lateral rotational impact than a sagittal or oblique impact. The obtained result shows that the higher stress occurred in a deep area of brain near the leading edge of a falx cerebri and tentorium cerebelli. It was confirmed that the greater stress areas of the brain matched the fact that DAI often involve the injury in a corpus callosum and a brain stem. Moreover, the brain dysfunctions due to an injury in the higher stress areas correspond to the residual disability in the diffuse axonal injury. We expect that the injury in a brain stem and cerebral limbic system is the essential of the diffuse axonal injury.

Head Impact Analysis related to the Mechanism of Diffuse Axonal Injury

In this paper, a three-dimensional digital human-head model was developed and several dynamic analyses on the head trauma were conducted. This model was built up by the VOXEL approach using 433 slice CT images (512×512 pixels) and made of 1.22 million parallelepiped finite elements with 10 anatomical tissue properties such as scalp, CSF, skull, brain, dura mater and so on. The numerical analyses were conducted using a finite element code the authors have developed. The main features of the code are 1) it is based on the explicit time integration method and 2) it uses the one point integration method to evaluate the equivalent nodal forces with the hourglass control proposed by Flanagan and Belythcko and 3) it utilizes the parallel computation with the MPI. In order to verify the developed model, the head impact experiment for a cadaver by Nahum et al. was simulated. The calculated results showed good agreement with experimental ones. A front and rear impact analyses were also performed investigate the relation between the impact direction and the positions of the high measurement of pressure and stresses in brain. The obtained results represent that brain injury has a closer relation with the Mises equivalent stress rather than the pressure. At this time, the large deformation of a frontal cranial base was observed in both frontal and occipital impact analyses. We expect that it induces the brain injury in a frontal lobe regardless of the impact positions.

https://www.jstage.jst.go.jp/article/kikaia1979/74/740/74_740_611/_pdf

Dai Watanabe

Papers

Impact Injury Analysis of the Human Head

Development of a Human Head FE Model and Impact Simulation on the Focal Brain Injury

Head Impact Analysis related to the Mechanism of Diffuse Axonal Injury

Development of a human head FE model for the impact analysis using VOXEL approach and simulation for the assessment on the focal brain injury

Injury analysis of a head subjected to the lateral rotational impact related to the mechanism of diffuse axonal injury using the voxel head model