title: Application of polymer sensitive MRI sequence to localization of EEG electrodes.
abstract: The growing popularity of simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) opens up the possibility of imaging EEG electrodes while the subject is in the scanner. Such information could be useful for improving the fusion of EEG-fMRI datasets.
  
  
  
  Here, we report for the first time how an ultra-short echo time (UTE) MR sequence can image the materials of an MR-compatible EEG cap, finding that electrodes and some parts of the wiring are visible in a high resolution UTE. Using these images, we developed a segmentation procedure to obtain electrode coordinates based on voxel intensity from the raw UTE, using hand labeled coordinates as the starting point.
  
  
  
  We were able to visualize and segment 95% of EEG electrodes using a short (3.5min) UTE sequence. We provide scripts and template images so this approach can now be easily implemented to obtain precise, subject-specific EEG electrode positions while adding minimal acquisition time to the simultaneous EEG-fMRI protocol.
  
  
  
  T1 gel artifacts are not robust enough to localize all electrodes across subjects, the polymers composing Brainvision cap electrodes are not visible on a T1, and adding T1 visible materials to the EEG cap is not always possible. We therefore consider our method superior to existing methods for obtaining electrode positions in the scanner, as it is hardware free and should work on a wide range of materials (caps).
  
  
  
  EEG electrode positions are obtained with high precision and no additional hardware.
authors.affiliation: Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Science, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre d'imagerie moléculaire de Sherbrooke (CIMS), Centre de Recherche CHUS, Canada. Electronic address: russell.buttler@usherbrooke.ca.
authors.forename: Russell
authors.initials: R
authors.lastname: Butler
authors.affiliation: MR Clinical Science, Philips Healthcare Canada, 281 H illmount Road, Markham, Ontario, L6C 2S3, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Gilbert
authors.affiliation: Sherbrooke Connectivity Imaging Lab (SCIL), Computer Science department, Science Faculty, Université de Sherbrooke, Canada; Centre d'imagerie moléculaire de Sherbrooke (CIMS), Centre de Recherche CHUS, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Descoteaux
authors.affiliation: Department of Kinanthropology, University of Sherbrooke, Sherbrooke, Quebec, Canada.
authors.forename: Pierre-Michel
authors.initials: PM
authors.lastname: Bernier
authors.affiliation: Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Science, Université de Sherbrooke, Sherbrooke, Québec, Canada; Department of Diagnostic Radiology, Faculty of Medicine and Health Science, Université de Sherbrooke, 12e Avenue Nord, Sherbrooke, QC, J1H 5N4, Canada; Centre d'imagerie moléculaire de Sherbrooke (CIMS), Centre de Recherche CHUS, Canada.
authors.forename: Kevin
authors.initials: K
authors.lastname: Whittingstall
mesh_terms: D000328:Adult; D016477:Artifacts; D004566:Electrodes; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods*; D011108:Polymers; D013997:Time Factors; D055815:Young Adult
chemical_list: D011108:Polymers
keywords: EEG; Electrode location; FMRI; Simultaneous EEG-FMRI; UTE