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On the synchronization of transcranial magnetic stimulation and functional echo-planar imaging

Bestmann, S; Baudewig, J; Frahm, J; (2003) On the synchronization of transcranial magnetic stimulation and functional echo-planar imaging. J MAGN RESON IMAGING , 17 (3) 309 - 316. 10.1002/jmri.10260.

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Abstract

Purpose: To minimize artifacts in echo-planar imaging (EPI) of human brain function introduced by simultaneous transcranial magnetic stimulation (TMS).Materials and Methods: Distortions due to TMS pulses (0.25 msec, 2.0 T) were studied at 2.0 T before and during EPI.Results: Best results were obtained if both the EPI section orientation and the frequency-encoding gradient were parallel to the plane of the TMS coil. Under these conditions, a TMS pulse caused image distortions when preceding the EPI sequence by less than 100 msec. Recordings with a magnetic field gradient pick-up coil revealed transient magnetic fields after TMS, which are generated by eddy currents in the TMS coil. TMS during image acquisition completely spoiled all transverse magnetizations and induced disturbances ranging from image corruption to mild image blurring, depending on the affected low and high spatial frequencies. Simultaneous TMS and radio-frequency (RF) excitation gave rise to T1-dependent signal changes that lasted for several seconds and yielded pronounced false-positive activations during functional brain mapping.Conclusion: To ensure reliable and robust combinations, TMS should be applied at least 100 msec before EPI while completely avoiding any pulses during imaging.

Type: Article
Title: On the synchronization of transcranial magnetic stimulation and functional echo-planar imaging
DOI: 10.1002/jmri.10260
Keywords: magnetic resonance imaging, transcranial magnetic stimulation, human brain, BOLD, RF excitation, functional echo-planar imaging, BRAIN ACTIVATION, MOTOR CORTEX, BOLD-FMRI, TMS
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences
URI: http://discovery.ucl.ac.uk/id/eprint/146225
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