This paper on "FEM as a Tool for Minimal Invasive Brain Surgery" was presented at the NAFEMS World Congress on Design, Simulation & Optimisation: Reliability & Applicability of Computational Methods - 9-11 April 1997, Stuttgart, Germany.

Summary

In this study, deformations and displacements of brain tissue are predicted in the region of interest (ROI), and thus any discrepancies between preoperative images and the actual anatomy during minimal invasive brain surgery can be eliminated. Due to the complexity of the problem. analytical solutions cannot be found. Thus, we use the finite element method (FEM) to determine the deformations and displacements of brain structures caused by changes of the direction of the vector of gravity, the discharge of liquor cerebrospinalis, and the mechanical forces exerted by the surgical instruments during the intervention. The characteristic properties of the brain structure, such as density and elasticity, are measured with an ultrasonic system, which has been developed by the authors. An anisotropic behaviour of brain tissue was found with elasticity varying by about 15% depending on direction and location. The results of this study indicate that the knowledge of the inhomogeneous and anisotropic mechanical brain properties and of the applied forces permits the calculation of the optimal, i.e. least damaging, path for the surgical instrument from skull opening to the target by means of a Finite Element Analysis.