Brain tissue mechanical properties are of importance to investigate child head injury using finite element (FE) method. However, these properties used in child head FE model normally vary in a large range in published literatures because of the insufficient child cadaver experiments. In this work, a head FE model with detailed anatomical structures is developed from the computed tomography (CT) data of a 6-year-old healthy child head. The effects of brain tissue mechanical properties on traumatic brain response are also analyzed by reconstruction of a head impact on engine hood according to Euro-NCAP testing regulation using FE method. The result showed that the variations of brain tissue mechanical parameters in linear viscoelastic constitutive model had different influences on the intracranial response. Furthermore, the opposite trend was obtained in the predicted shear stress and shear strain of brain tissues caused by the variations of mentioned parameters.
The epidemiological investigations showed that the craniocerebral injury caused by traffic accidents was one of the main reasons for children’s death [
It is well known that the proper brain tissue material constitutive models and accurate material parameters are the key factors of FE method to investigate craniocerebral injury. However, the mechanical properties of brain tissues varied with child age gradually [
In this study, a FE model with more detail anatomical features was developed based on head FE model created by Ruan et al. [
Based on the validated FE model created by Ruan et al. [
FE model of a 6-year-old child head with detailed head anatomical structures.
The linear viscoelastic constitutive model was commonly applied to investigate brain tissue injury in the head FE models. The Zener model for brain tissues was adopted in this research, and the constitutive equation was defined in the following equation:
Thibault and Margulies [
Brain mechanical properties found in the literature and used in the simulation.
Literature |
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|
|
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Roth et al. [ |
5.99 | 2.32 | 0.09248 | 2110 |
Nicolle et al. [ |
9.884 | 3.725 | 920 | 1125 |
Shuck and Advani [ |
49 | 16.2 | 145 | 1125 |
Lee [ |
26.9–110 | 2.87 | 50 | 1.25–5.44 |
DiMasi et al. [ |
34.474 | 17.23 | 100 | 68.948 |
Ruan [ |
528 | 168 | 35 | 127.9 |
In the table,
Material properties used in the head model.
Density/kg⋅m−3 | Poisson’s ratio |
|
|
---|---|---|---|
Meninges | 1140 | 0.45 | 31.5 |
CSF | 1040 | 0.49 | 0.012 |
Scalp | 1200 | 0.42 | 16.7 |
Cortical bone of skull | 2150 | 0.22 | 9870 |
Cancellous bone of skull | 2150 | 0.22 | 3690 |
Sutures | 2150 | 0.22 | 1100 |
From Table
To evaluate the effects of brain tissue mechanical parameters variation on intracranial response, a comprehensive parametric study was conducted. The simulation matrix with different parametric combinations is shown in Table
Detailed experiment series with different parameters.
|
|
|
|
|
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Base | 49 | 16.2 | 145 | 2190 |
Ex_1 | 4.9 | 1.62 | 145 | 2190 |
Ex_2 | 490 | 162 | 145 | 2190 |
Ex_3 | 49 | 16.2 | 1.45 | 2190 |
Ex_4 | 49 | 16.2 | 14.5 | 2190 |
Ex_5 | 49 | 16.2 | 1450 | 2190 |
Ex_6 | 4.9 | 1.62 | 145 | 219 |
Ex_7 | 4.9 | 1.62 | 145 | 21.9 |
The impact between the developed child head model and engine hood was reconstructed according to Euro-NCAP testing regulations [
Impact location beneath the engine hood.
Figure
Simulation of impact between FE head model and engine hood.
Though
The intracranial pressure time histories with different
The peak shear stress increases while shear strain decreases with the increase of
The absolute values of coup and contrecoup pressure rise with the increase of
Intracranial pressure time histories with different
The impact direction of head in the simulation is not the same as the normal direction of engine hood surface. Therefore, the resultant head acceleration includes not only linear acceleration but also rotational acceleration during the impact process, which can lead to shear effect on brain tissues. Zhang et al. suggested that the probability of mild traumatic brain injury could be 50% when shear stress reaches 0.0078 MPa, and probability could be 80% when it exceeds 0.01 MPa [
Shear stress distribution with different
Likewise, peak shear stress also increases continuously with the increase of
However, shear strain of brain tissues decreases with the increase of
Shear strain distribution with different
Simulation results in Figure
Intracranial pressure time histories with different
According to Zhang’s shear stress injury criteria with 0.0078 MPa [
Brain shear stress distribution with different
Brain shear stress distribution with different
The upper limit values of brain shear strain with different
Brain shear strain distribution with different
Though
The finite element head model of a child with detailed anatomical structures was established based on CT images of a 6-year-old healthy child head. According to Euro-NCAP testing regulation, impact simulation experiments between the child head model and engine hood were studied. The influence of brain mechanical properties on the intracranial response was analyzed systematically through a comprehensive parametric study.
Intracranial pressure and shear stress of brain tissues increase with the increase of bulk modulus
The effects of shear modulus
As for decay coefficient
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by the National Natural Science Foundation of China (81201015, 81371360, and 81471274).