Modular multilevel TMS device with wide output range and ultrabrief pulse capability for sound reduction

Zhiyong Zeng, Lari M Koponen, Rena Hamdan, Zhongxi Li, Stefan M Goetz*, Angel V Peterchev*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Objective. This article presents a novel transcranial magnetic stimulation (TMS) pulse generator with a wide range of pulse shape, amplitude, and width.

Approach. Based on a modular multilevel TMS (MM-TMS) topology we had proposed previously, we realized the first such device operating at full TMS energy levels. It consists of ten cascaded H-bridge modules, each implemented with insulated-gate bipolar transistors, enabling both novel high-amplitude ultrabrief pulses as well as pulses with conventional amplitude and duration. The MM-TMS device can output pulses including up to 21 voltage levels with a step size of up to 1100 V, allowing relatively flexible generation of various pulse waveforms and sequences. The circuit further allows charging the energy storage capacitor on each of the ten cascaded modules with a conventional TMS power supply.

Main results. The MM-TMS device can output peak coil voltages and currents of 11 kV and 10 kA, respectively, enabling suprathreshold ultrabrief pulses (>8.25 μs active electric field phase). Further, the MM-TMS device can generate a wide range of near-rectangular monophasic and biphasic pulses, as well as more complex staircase-approximated sinusoidal, polyphasic, and amplitude-modulated pulses. At matched estimated stimulation strength, briefer pulses emit less sound, which could enable quieter TMS. Finally, the MM-TMS device can instantaneously increase or decrease the amplitude from one pulse to the next in discrete steps by adding or removing modules in series, which enables rapid pulse sequences and paired-pulse protocols with variable pulse shapes and amplitudes.

Significance. The MM-TMS device allows unprecedented control of the pulse characteristics which could enable novel protocols and quieter pulses.
Original languageEnglish
Article number026008
Number of pages16
JournalJournal of Neural Engineering
Volume19
Issue number2
Early online date17 Mar 2022
DOIs
Publication statusPublished - 1 Apr 2022

Bibliographical note

Funding Information:
Research reported in this publication was supported by the National Institute of Mental Health of the National Institutes of Health under award numbers R01MH111865 and RF1MH124943 as well as by hardware donations from Magstim. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Publisher Copyright:
© 2022 IOP Publishing Ltd.

Keywords

  • transcranial magnetic stimulation
  • modular multilevel converter
  • cascaded H-bridge
  • pulse shape
  • sound
  • loudness

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