| Description |
Traumatic brain injury is a devastating medical problem worldwide. Contusion, which involves direct damage of both brain tissue and surrounding blood vessels, has been called the hallmark of head injury. Controlled cortical impact (CCI) is a commonly used experimental model to study contusion and may be useful in the study of vascular injury, but there is currently no way to measure strain in the cortex or in the cortical blood vessels. Finite element (FE) models have been utilized to characterize the deformation of brain tissue during CCI, but none have explored strains relevant to the blood vessels. Specifically, these models have reported strains relative to the global reference frame only. The objective of this research was to characterize strains tangent to the surface of the cortex in order to estimate deformations that vessels on the surface of the brain may experience during CCI. An FE model was built from coronal section images of a mouse brain. The brain, pia-arachnoid complex, dura, and skull were separately modeled along with a rigid indenter. Global strains were transformed to the local coordinate system defined by the orientation of the brain surface at the point of interest. Strain distributions were investigated in the baseline model and showed that circumferential strain is the primary contributor to principal strain, while radial strain is high in the center but contributes little to tensile strains away from the very center. In order to characterize the influence of experimental parameters on predicted deformations, indentation rate, depth, craniotomy size, indentation angle, and indenter tip shape were each varied, and the resulting strain distribution was compared to the baseline results. Tip shape was the most influential parameter, producing the highest strain concentration on the surface of the brain. Indentation depth, rate, and angle also significantly influenced the strain distribution on the brain. Based on previously reported values of failure strain for cerebral arteries, simulations consistently predicted the occurrence of vessel injury, a frequent outcome of CCI. |
