title: Transcranial Magnetic Stimulation: An Automated Procedure to Obtain Coil-specific Models for Field Calculations.
abstract: BACKGROUND
  Field calculations for transcranial magnetic stimulation (TMS) are increasingly implemented online in neuronavigation systems and in more realistic offline approaches based on finite-element methods. They are often based on simplified and/or non-validated models of the magnetic vector potential of the TMS coils.
  
  
  OBJECTIVE
  To develop an approach to reconstruct the magnetic vector potential based on automated measurements.
  
  
  METHODS
  We implemented a setup that simultaneously measures the three components of the magnetic field with high spatial resolution. This is complemented by a novel approach to determine the magnetic vector potential via volume integration of the measured field.
  
  
  RESULTS
  The integration approach reproduces the vector potential with very good accuracy. The vector potential distribution of a standard figure-of-eight shaped coil determined with our setup corresponds well with that calculated using a model reconstructed from x-ray images.
  
  
  CONCLUSIONS
  The setup can supply validated models for existing and newly appearing TMS coils.
authors: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Cognitive Systems, DTU Compute, Technical University of Denmark, Kgs. Lyngby, Denmark. Electronic address: kristofferm@drcmr.dk.
authors: Kristoffer H
authors: KH
authors: Madsen
authors: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark.
authors: Lars
authors: L
authors: Ewald
authors: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg, Denmark.
authors: Hartwig R
authors: HR
authors: Siebner
authors: Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Biomedical Engineering Section, Technical University of Denmark, Kgs. Lyngby, Denmark; Max-Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors: Axel
authors: A
authors: Thielscher
mesh_terms: D060526:Magnetic Fields; D015233:Models, Statistical; D012984:Software; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: Electric field calculations; Magnetic vector potential; Stimulation coils; Transcranial magnetic stimulation