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.
Bohning
Daryl E
DE
Center for Advanced Imaging Research, Department of Radiology, Medical University of South Carolina, 169 Ashley Avenue, Charleston, SC 29425, USA. bohninde@musc.edu
Denslow
S
S
Bohning
P A
PA
Walker
J A
JA
George
M S
MS
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