Patient-specific brain modelling for deep brain stimulation simulations

A patient-specific modelling technique for simulation of the electric field surrounding deep brain stimulation (DBS) electrodes has been adapted to T1 and T2-weigthed, proton density (PrD) and spoiled gradient echo (SPGR) magnetic resonance imaging (MRI) sequences. Electrical conductivity (σ) assignment of gray and white matter was made dependent on the neuromodulator settings. Nine brain models with different σ were created. Four PrD/SPGR images tuned differently were fused. Five models based on the same T2 batch of MRI were set up with different σ. Finite element simulations (2, 3, 4, 5 V) of bilateral DBS electrodes positioned in the globus pallidus internus (GPi) were created. The electric field volumes were calculated for isosurfaces of 0.2V/mm and 0.1V/mm. A reference T2-model was used for comparison. At 0.1V/mm white matter had a larger influence when set to ten times the original value. Homogenous models responded similar. It was found that the method was sensitive to very small electrical conductivity variations and consequently to the corresponding anatomical variations in tissue type.