106
K. H. Yang and H. Mao
of skull thickness, brain radius, and snout length in addition to the peak incident
pressure when analysing bTBI using a decision tree data mining method based on a
highly simplified FE pig model.
In addition, the rate at which strain increases or decreases was found to be
correlated to mTBI observed in NFL games [111]. In this study, the product
of the strain rate and strain was found to be a better predictor of injury risk
than the strain alone. All aforementioned studies suggested that TBI mechanisms
may be more complex than those reported in literatures. As computational head
models, especially FE head models, are expected to thoroughly reveal regional
brain responses during impact that are correlated with brain injuries, proper injury
mechanisms should be identified prior to using such models to design protection
equipment.
5.3 Challenges of Developing a Biofidelic FE Head Model
The four key constituents of any FE model are the model geometry, material properties, boundary conditions, and loading conditions. Medical images are typically
segmented to acquire various anatomical features within the brain. The segmented
data can then be used to develop model geometry, or mesh. Detailed descriptions of
brain imaging and segmentation can be found in Chap. 3 and will not be discussed
here. In this chapter, emphasis will be placed on selecting the anatomical features
of the brain for inclusion in an FE head model, boundary conditions, and loading
conditions. Nevertheless, readers are advised of the fact that accurate material
properties are key to model the brain accurately.
5.3.1 Selection of Anatomical Features
In terms of selecting the anatomical features, the skin and scalp layers need to be
included in an FE head model even though these structures are not needed when
simulating a closed-head injury in which skull deformation is of no concern. In these
cases, it is a common practice to apply all three components of linear and angular
accelerations to the centre of gravity of the head model to determine intracranial
tissue responses (e.g. [97, 111]). If simulation time is of concern, these layers can
be assigned as rigid materials to reduce the computational cost. On the other hand, a
model with skin and scalp representation can be used directly if a real-world direct
impact scenario is to be considered. This same approach is also recommended for
facial bones.
The bony skull plays a vital role in the protection of the brain from external
loading. Mechanically, the rigidity of the skull (in terms of its modulus and
thickness) determines the magnitude of the intracranial pressure due to direct impact
or inertial loading. The adult human skull is made up of eight bones that are rigidly
K. H. Yang and H. Mao
of skull thickness, brain radius, and snout length in addition to the peak incident
pressure when analysing bTBI using a decision tree data mining method based on a
highly simplified FE pig model.
In addition, the rate at which strain increases or decreases was found to be
correlated to mTBI observed in NFL games [111]. In this study, the product
of the strain rate and strain was found to be a better predictor of injury risk
than the strain alone. All aforementioned studies suggested that TBI mechanisms
may be more complex than those reported in literatures. As computational head
models, especially FE head models, are expected to thoroughly reveal regional
brain responses during impact that are correlated with brain injuries, proper injury
mechanisms should be identified prior to using such models to design protection
equipment.
5.3 Challenges of Developing a Biofidelic FE Head Model
The four key constituents of any FE model are the model geometry, material properties, boundary conditions, and loading conditions. Medical images are typically
segmented to acquire various anatomical features within the brain. The segmented
data can then be used to develop model geometry, or mesh. Detailed descriptions of
brain imaging and segmentation can be found in Chap. 3 and will not be discussed
here. In this chapter, emphasis will be placed on selecting the anatomical features
of the brain for inclusion in an FE head model, boundary conditions, and loading
conditions. Nevertheless, readers are advised of the fact that accurate material
properties are key to model the brain accurately.
5.3.1 Selection of Anatomical Features
In terms of selecting the anatomical features, the skin and scalp layers need to be
included in an FE head model even though these structures are not needed when
simulating a closed-head injury in which skull deformation is of no concern. In these
cases, it is a common practice to apply all three components of linear and angular
accelerations to the centre of gravity of the head model to determine intracranial
tissue responses (e.g. [97, 111]). If simulation time is of concern, these layers can
be assigned as rigid materials to reduce the computational cost. On the other hand, a
model with skin and scalp representation can be used directly if a real-world direct
impact scenario is to be considered. This same approach is also recommended for
facial bones.
The bony skull plays a vital role in the protection of the brain from external
loading. Mechanically, the rigidity of the skull (in terms of its modulus and
thickness) determines the magnitude of the intracranial pressure due to direct impact
or inertial loading. The adult human skull is made up of eight bones that are rigidly