title: EEG-fMRI using z-shimming in patients with temporal lobe epilepsy.
abstract: OBJECTIVE
  To use z-shimming, a technique that reduces signal loss due to susceptibility artifacts that can result in reduced or absent activation in electroencephalography (EEG) functional MRI (fMRI) sessions in patients with temporal lobe epilepsy (TLE), to determine whether it would result in an increased ability to detect significant regions of blood oxygenation level-dependent (BOLD) signal change.
  
  
  METHODS
  Eight patients with TL EEG spikes underwent an EEG-fMRI scanning session using z-shimming. The signal intensities in the z-shimmed images were compared with those in the standard images. BOLD activation maps were created from the two sets of images using the timings of the spikes observed on the EEG.
  
  
  RESULTS
  The mean signal increase in the TLs as a result of z-shimming was 45.9%+/-4.5%. The percentage of TL voxels above a brain intensity threshold rose from 66.1%+/-7.6% to 77.6%+/-5.7%. This appreciable increase in signal did not lead to any significant differences in the statistical maps created with the two sets of functional images.
  
  
  CONCLUSIONS
  The results suggest that loss of signal is not the limiting factor for the detection of spike-related BOLD signal changes in patients with TLE activity.
authors.affiliation: School of Psychology, University of Birmingham, Birmingham, United Kingdom. a.p.bagshaw@bham.ac.uk
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Bagshaw
authors.forename: Leili
authors.initials: L
authors.lastname: Torab
authors.forename: Eliane
authors.initials: E
authors.lastname: Kobayashi
authors.forename: Colin
authors.initials: C
authors.lastname: Hawco
authors.forename: François
authors.initials: F
authors.lastname: Dubeau
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
authors.forename: Jean
authors.initials: J
authors.lastname: Gotman
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity