A TMS coil positioning/holding system for MR image-guided TMS interleaved with fMRI.
OBJECTIVE
Transcranial magnetic stimulation (TMS) can be interleaved with fMRI to visualize regional brain activity in response to direct, non-invasive, cortical stimulation, making it a promising tool for studying brain function. A major practical difficulty is accurately positioning the TMS coil within the MRI scanner for stimulating a particular area of brain cortex. The objective of this work was to design and build a self-contained hardware/software system for MR-guided TMS coil positioning in interleaved TMS/fMRI studies.


METHODS
A compact, manually operated, articulated TMS coil positioner/holder with 6 calibrated degrees of freedom was developed for use inside a cylindrical RF head coil, along with a software package for transforming between MR image coordinates, MR scanner space coordinates, and positioner/holder settings.


RESULTS
Phantom calibration studies gave an accuracy for positioning within setups of dx=+/-1.9 mm, dy=+/-1.4 mm, dz=+/-0.8 mm and a precision for multiple setups of dx=+/-0.8 mm, dy=+/-0.1 mm, dz=+/-0.1 mm.


CONCLUSIONS
This self-contained, integrated MR-guided TMS system for interleaved TMS/fMRI studies provides fast, accurate location of motor cortex stimulation sites traditionally located functionally, and a means of consistent, anatomy-based TMS coil positioning for stimulation of brain areas without overt response.
Center for Advanced Imaging Research, Department of Radiology, Medical University of South Carolina, 169 Ashley Avenue, Charleston, SC 29425, USA. bohninde@musc.edu
Daryl E
DE
Bohning
S
S
Denslow
P A
PA
Bohning
J A
JA
Walker
M S
MS
George
D002138:Calibration; D003201:Computers; D004558:Electric Stimulation / Q000295:instrumentation*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D008280:Magnetics / Q000295:instrumentation*; D015203:Reproducibility of Results; D012984:Software