Brain Deformation under Mild Impact: Magnetic Resonance Imaging-based Assessment and Finite Element Study

The knowledge of in vivo human brain deformation within the skull is essential in understanding brain injury mechanisms. Such measurements have become possible only in recent years thanks to the advancement of magnetic resonance imaging (MRI) technique. In this paper, we first study in vivo human brain deformation under mild impact induced by a 2cm head drop using tagged MRI and the harmonic phase (HARP) imaging analysis technique originally developed for cardiac motion analysis. A finite element (FE) simulation of mild impact is then carried out using a patient-specific 3-D head model. A reasonably good correlation is found between the predicted deformation field from FE modelling and the results from MRI-based assessment. It is found that the maximum deformations occur within a few milliseconds following the impact, which is during the first oscillation of the brain within the skull, with the maximum displacements of 2-3 mm and the maximum strains of 5-10%. To our knowledge, this study is the first attempt where the deformation field obtained by MRI-based assessment is correlated with the prediction of a corresponding FE model, and it is also the first validation of a FE brain injury model on in vivo human brain deformation data.