Brain tissue biomechanics in cortical contusion injury: a finite element analysis

The controlled cortical impact model has been used extensively to study focal traumatic brain injury. Although the impact variables can be well defined, little is known about the biomechanical trauma as delivered to different brain regions. This knowledge however could be valuable for interpretation of experiment (immunohistochemistry etc.), especially regarding the comparison of the regional biomechanical severity level to the regional magnitude of the trauma sequel under investigation. We used finite element (FE) analysis, based on high resolution T2-weighted MRI images of rat brain, to simulate displacement, mean stress, and shear stress of brain during impact. Young's Modulus E, to describe tissue elasticity, was assigned to each FE in three scenarios: in a constant fashion (E = 50 kPa), or according to the MRI intensity in a linear (E = [10, 100] kPa) and inverse-linear fashion (E = [100, 10] kPa). Simulated tissue displacement did not vary between the 3 scenarios, however mean stress and shear stress were largely different. The linear scenario showed the most likely distribution of stresses. In summary, FE analysis seems to be a suitable tool for biomechanical simulation, however, to be closest to reality tissue elasticity needs to be determined with a more specific approach, e.g. by means of MRI elastography.