Electric field measurement of two commercial active/sham coils for transcranial magnetic stimulation.

Journal Article (Journal Article)

OBJECTIVE: Sham TMS coils isolate the ancillary effects of their active counterparts but typically induce low-strength electric fields (E-fields) in the brain, which could be biologically active. We measured the E-fields induced by two pairs of commonly-used commercial active/sham coils. APPROACH: E-field distributions of the active and sham configurations of the Magstim 70 mm AFC and MagVenture Cool-B65 A/P coils were measured over a 7 cm-radius, hemispherical grid approximating the cortical surface. Peak E-field strength was recorded over a range of pulse amplitudes. MAIN RESULTS: The Magstim and MagVenture shams induce peak E-fields corresponding to 25.3% and 7.72% of their respective active values. The MagVenture sham has an E-field distribution shaped like its active counterpart. The Magstim sham induces nearly zero E-field under the coil's center, and its peak E-field forms a diffuse oval 3-7 cm from the center. Electrical scalp stimulation paired with the MagVenture sham is estimated to increase the sham E-field in the brain up to 10%. SIGNIFICANCE: Different commercial shams induce different E-field strengths and distributions in the brain, which should be considered in interpreting outcomes of sham stimulation.

Full Text

Duke Authors

Cited Authors

  • Smith, JE; Peterchev, AV

Published Date

  • October 2018

Published In

Volume / Issue

  • 15 / 5

Start / End Page

  • 054001 -

PubMed ID

  • 29932429

Pubmed Central ID

  • PMC6125221

Electronic International Standard Serial Number (EISSN)

  • 1741-2552

Digital Object Identifier (DOI)

  • 10.1088/1741-2552/aace89


  • eng

Conference Location

  • England