New coil positioning method for interleaved transcranial magnetic stimulation (TMS)/functional MRI (fMRI) and its validation in a motor cortex study.
OBJECTIVE
To develop and test a novel method for coil placement in interleaved transcranial magnetic stimulation (TMS)/functional MRI (fMRI) studies.


METHODS
Initially, a desired TMS coil position at the subject's head is recorded using a neuronavigation system. Subsequently, a custom-made holding device is used for coil placement inside the MR scanner. The parameters of the device corresponding to the prerecorded position are automatically determined from a fast structural image acquired directly before the experiment. The spatial accuracy of our method was verified on a phantom. Finally, in a study on five subjects, the coil was placed above the cortical representation of a hand muscle in M1 and the blood oxygenation level-dependent (BOLD) responses to short repetitive TMS (rTMS) trains were assessed using echo-planar imaging (EPI) recordings.


RESULTS
The spatial accuracy of our method is in the range of 2.9 +/- 1.3 (SD) mm. Motor cortex stimulation resulted in robust BOLD activations in motor- and auditory related brain areas, with the activation in M1 being localized in the hand knob.


CONCLUSIONS
We present a user-friendly method for TMS coil positioning in the MR scanner that exhibits good spatial accuracy and speeds up the setup of the experiment. The motor-cortex study proves the viability of the approach and validates our interleaved TMS/fMRI setup.
Moisa
Marius
M
High-Field Magnetic Resonance Center, Max Planck Institute (MPI) for Biological Cybernetics, Tübingen, Germany.
Pohmann
Rolf
R
Ewald
Lars
L
Thielscher
Axel
A
D000328:Adult; D004867:Equipment Design; D019544:Equipment Failure Analysis; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008280:Magnetics / Q000295:instrumentation*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050781:Transcranial Magnetic Stimulation / Q000295:instrumentation* / Q000379:methods