Real-time E-field dosimetry for E-field informed neuronavigation of transcranial magnetic stimulation

Background. Transcranial Magnetic Stimulation (TMS) coil placement and pulse waveform current are often chosen to achieve a specified E-field dose on targeted brain regions.

Objective. Our goal is to improve TMS neuronavigation targeting by including real-time accurate distributions of the E-field dose on the cortex. 

Approach. We introduced a method and developed software for computing brain E-field distributions in real-time (under 4 ms) enabling easy integration into neuronavigation and with the same accuracy as 1st order finite element method (FEM) solvers. 

Main results. We conducted a comparative analysis of E-fields computed by FEM and in real-time for eight subjects, utilizing two head model types (SimNIBS’s ‘headreco’ and ‘mri2mesh’ pipeline), three coil types (circular, double-cone, and Figure-8), and 1000 coil placements (48,000 simulations). The real-time computation for any coil placement is within 4 milliseconds (ms), for 400 modes, and requires less than 4 GB of memory on a GPU. Our 

Significance. Our solver is capable of computing E-fields within 4 ms, making it a practical approach for integrating E-field information into the neuronavigation systems without imposing a significant overhead on frame generation (20 and 50 frames per second within 50 and 20 ms, respectively).

Ongoing work. We are working on integrating our solver with existing neuronavigation tools.

[J14]      L. J. Gomez, M. Dannhauer and A. Peterchev, " Fast computational optimization of TMS coil placement for individualized electric field targeting," NeuroImage, vol. 228, no. 3, pp. 1-13, 2021. 

Preprint: https://doi.org/10.1101/2023.10.25.564044