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Optimized monophasic pulses with equivalent electric field for rapid-rate transcranial magnetic stimulation.

Publication ,  Journal Article
Wang, B; Zhang, J; Li, Z; Grill, WM; Peterchev, AV; Goetz, SM
Published in: J Neural Eng
June 6, 2023

Objective.Transcranial magnetic stimulation (TMS) with monophasic pulses achieves greater changes in neuronal excitability but requires higher energy and generates more coil heating than TMS with biphasic pulses, and this limits the use of monophasic pulses in rapid-rate protocols. We sought to design a stimulation waveform that retains the characteristics of monophasic TMS but significantly reduces coil heating, thereby enabling higher pulse rates and increased neuromodulation effectiveness.Approach.A two-step optimization method was developed that uses the temporal relationship between the electric field (E-field) and coil current waveforms. The model-free optimization step reduced the ohmic losses of the coil current and constrained the error of the E-field waveform compared to a template monophasic pulse, with pulse duration as a second constraint. The second, amplitude adjustment step scaled the candidate waveforms based on simulated neural activation to account for differences in stimulation thresholds. The optimized waveforms were implemented to validate the changes in coil heating.Main results.Depending on the pulse duration and E-field matching constraints, the optimized waveforms produced 12%-75% less heating than the original monophasic pulse. The reduction in coil heating was robust across a range of neural models. The changes in the measured ohmic losses of the optimized pulses compared to the original pulse agreed with numeric predictions.Significance.The first step of the optimization approach was independent of any potentially inaccurate or incorrect model and exhibited robust performance by avoiding the highly nonlinear behavior of neural responses, whereas neural simulations were only run once for amplitude scaling in the second step. This significantly reduced computational cost compared to iterative methods using large populations of candidate solutions and more importantly reduced the sensitivity to the choice of neural model. The reduced coil heating and power losses of the optimized pulses can enable rapid-rate monophasic TMS protocols.

Duke Scholars

Published In

J Neural Eng

DOI

EISSN

1741-2552

Publication Date

June 6, 2023

Volume

20

Issue

3

Location

England

Related Subject Headings

  • Transcranial Magnetic Stimulation
  • Neurons
  • Motor Cortex
  • Electric Stimulation
  • Biomedical Engineering
  • 1109 Neurosciences
  • 1103 Clinical Sciences
  • 0903 Biomedical Engineering
 

Citation

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Wang, B., Zhang, J., Li, Z., Grill, W. M., Peterchev, A. V., & Goetz, S. M. (2023). Optimized monophasic pulses with equivalent electric field for rapid-rate transcranial magnetic stimulation. J Neural Eng, 20(3). https://doi.org/10.1088/1741-2552/acd081
Wang, Boshuo, Jinshui Zhang, Zhongxi Li, Warren M. Grill, Angel V. Peterchev, and Stefan M. Goetz. “Optimized monophasic pulses with equivalent electric field for rapid-rate transcranial magnetic stimulation.J Neural Eng 20, no. 3 (June 6, 2023). https://doi.org/10.1088/1741-2552/acd081.
Wang B, Zhang J, Li Z, Grill WM, Peterchev AV, Goetz SM. Optimized monophasic pulses with equivalent electric field for rapid-rate transcranial magnetic stimulation. J Neural Eng. 2023 Jun 6;20(3).
Wang, Boshuo, et al. “Optimized monophasic pulses with equivalent electric field for rapid-rate transcranial magnetic stimulation.J Neural Eng, vol. 20, no. 3, June 2023. Pubmed, doi:10.1088/1741-2552/acd081.
Wang B, Zhang J, Li Z, Grill WM, Peterchev AV, Goetz SM. Optimized monophasic pulses with equivalent electric field for rapid-rate transcranial magnetic stimulation. J Neural Eng. 2023 Jun 6;20(3).
Journal cover image

Published In

J Neural Eng

DOI

EISSN

1741-2552

Publication Date

June 6, 2023

Volume

20

Issue

3

Location

England

Related Subject Headings

  • Transcranial Magnetic Stimulation
  • Neurons
  • Motor Cortex
  • Electric Stimulation
  • Biomedical Engineering
  • 1109 Neurosciences
  • 1103 Clinical Sciences
  • 0903 Biomedical Engineering