Karen Julia Mullinger1, Winston X. Yan1,
Takayuki Ohma1, Richard W. Bowtell1
1Sir Peter Mansfield Magnetic Resonance
Center, School of Physics and Astronomy, University of Nottingham,
Nottingham, Nottinghamshire, United Kingdom
EEG
data recorded simultaneously with fMRI acquisition are contaminated by large voltages
generated by the time-varying magnetic field gradients. Here, we show that
this gradient artefact (GA) can be reduced in magnitude by adjusting the
subjects axial position in the scanner. Experiments carried out on four
subjects show that the average GA produced by a multi-slice EPI acquisition
can be reduced by 36% by moving the subject 4 cm towards the feet, starting
with the nasion at iso-centre. A significant reduction in the residual
gradient artefact after average artefact subtraction was also found with the
subject at the optimal position.