Advanced Pipeline for Designing Multi-Locus TMS Coils with Current Density Constraints

Ilkka J. Rissanen, Victor H. Souza, Jaakko O. Nieminen, Lari M. Koponen, Risto J. Ilmoniemi

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Abstract

Objective : This work aims for a method to design manufacturable windings for transcranial magnetic stimulation (TMS) coils with fine control over the induced electric field (E-field) distributions. Such TMS coils are required for multi-locus TMS (mTMS).

Methods : We introduce a new mTMS coil design workflow with increased flexibility in target E-field definition and faster computations compared to our previous method. We also incorporate custom current density and E-field fidelity constraints to ensure that the target E-fields are accurately reproduced with feasible winding densities in the resulting coil designs. We validated the method by designing, manufacturing, and characterizing a 2-coil mTMS transducer for focal rat brain stimulation.

Results : Applying the constraints reduced the computed maximum surface current densities from 15.4 and 6.6 kA/mm to the target value 4.7 kA/mm, yielding winding paths suitable for a 1.5-mm-diameter wire with 7-kA maximum currents while still replicating the target E-fields with the predefined 2.8% maximum error in the FOV. The optimization time was reduced by two thirds compared to our previous method. Conclusion : The developed method allowed us to design a manufacturable, focal 2-coil mTMS transducer for rat TMS impossible to attain with our previous design workflow.

Significance : The presented workflow enables considerably faster design and manufacturing of previously unattainable mTMS transducers with increased control over the induced E-field distribution and winding density, opening new possibilities for brain research and clinical TMS.

Original languageEnglish
Pages (from-to)1-9
Number of pages9
JournalIEEE Transactions on Biomedical Engineering
Early online date4 Jan 2023
DOIs
Publication statusE-pub ahead of print - 4 Jan 2023

Bibliographical note

Publisher Copyright: Author

Keywords

  • Coil design
  • coil optimization
  • Coils
  • Current density
  • current density
  • mTMS
  • multi-locus TMS
  • Optimization
  • TMS
  • transcranial magnetic stimulation
  • Transcranial magnetic stimulation
  • Transducers
  • Windings
  • Wires

ASJC Scopus subject areas

  • Biomedical Engineering

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