Patient-Specific Simulations of Deep Brain Stimulation Electric Field with Aid of In-house Software ELMA

Abstract

Deep brain stimulation (DBS) is an established technique for reduction of symptoms in movement disorders. Finite element method (FEM) simulations of the electric field magnitude (EF) are useful for estimating the affected tissue around the DBS lead and this can help optimize the therapy. This paper describes how patient-specific FEM models can be set up with the aid of the Matlab-based in-house software tool ELMA. Electrode placement is determined from two coordinates in postoperative medical imaging and electric conductivity is assigned from preoperative magnetic resonance imaging (MRI) and patient-specific DBS data. Simulations are performed using the equation for steady currents in Comsol Multiphysics (CM). The simulated EF is superimposed on the preoperative MRI for evaluation of affected structures. The method is demonstrated with patient-specific simulations in the zona incerta and a globus pallidus example containing cysts with higher conductive which causes considerable distortion of the EF. The improved software modules and precise lead positioning simplifies and reduces the time for DBS EF modelling and simulation.

Postoperative Lead Movement after Deep Brain Stimulation Surgery and the Change of Stimulation Volume

“…This gave 2 positions per time point, the tip and 10 mm above AC-PC along the lead. These coordinates were used to place the DBS lead in a patient-specific brain model [15,27].…”

“…Models of the Medtronic 3389 lead were made in Comsol Multiphysics 5.2 (Comsol AB, Sweden). The electric field magnitude EF was calculated from the equation for steady currents with the electric conductivity taken from tissue classification with in-house software ELMA [15,27,28] of the T2-weighted preoperative 3 T MRI. The tissue was classified into gray matter, white matter, blood, or CSF, and their conductivities were assigned from tabulated values [29,30].…”

White matter tracing combined with electric field simulation – A patient-specific approach for deep brain stimulation

“…The first two models, assuming a bulk of homogenous and isotropic tissue, were created by applying conductivities ( σ ) corresponding to grey matter (Model I, σ GM = 0.123 S/m) and white matter (Model II, σ WM = 0.0754 S/m) respectively. A heterogenous isotropic model (Model III) was created, according to previously described method (Åström et al., 2009), to include the effect of varying conductivity properties in the brain using an inhouse developed MATLAB software, ELMA (Johansson et al., 2019). The software performs a tissue segmentation based on the intensities in the T 2 images.…”

Distribution of electric field in patients with obsessive compulsive disorder treated with deep brain stimulation of the bed nucleus of stria terminalis

“…EF t has been estimated to be 0.20 V/mm at the pulse width of 60 µs to 0.14 V/mm at the pulse width of 150 µs based on experimental studies by Alexis Kuncel et al [38] and Mario Rizzone et al [52]. For details, see reference [34]. This threshold has been used in several previous studies [4,7,28].…”