Complete validation of any finite element (FE) model of the
human brain is very difficult due to the lack of adequate
experimental data. However, more animal brain injury data,
especially rat data, obtained under well-defined mechanical loading
conditions, are available to advance the understanding of the
mechanisms of traumatic brain injury. Unfortunately, internal
response of the brain in these experimental studies could not be
measured. The aim of this study was to develop a detailed FE model
of the rat brain for the prediction of intracranial responses due
to different impact scenarios. Model results were used to elucidate
possible brain injury mechanisms.
An FE model, consisting of more than 250,000 hexahedral elements
with a typical element size of 100 to 300 microns, was developed to
represent the brain of a rat. The model was first validated locally
against peak brain deformation data obtained from nine unique
dynamic cortical deformation (vacuum) tests. The model was then
used to predict biomechanical responses within the brain due to
controlled cortical impacts (CCI). A total of six different series
of CCI studies, four with unilateral craniotomy and two with
bilateral craniotomy, were simulated and the results were
systematically analyzed, including strain, strain rate and pressure
within the rat brain. In the four unilateral CCI studies,
approximately 150 rats were subjected to velocities ranging from
2.25 to 4 m/s, and cortical deformations of 1, 2 or 3 mm, with
impactor diameters of 2.5 or 5 mm. Moreover, the impact direction
varied from lateral 23 degrees to vertical. For the bilateral
craniotomy CCI studies, about 70 rats were injured at 4.7 or 6 m/s,
with deformations of 1.5 or 2.5 mm and impactor diameters of 3 or 5
mm, and at an impact direction of about 23-30 degrees laterally.
Simulation results indicate that intracranial strains best
correlate with experimentally obtained injuries.