Localizing ECoG electrodes on the cortical anatomy without post-implantation imaging.
BACKGROUND
Electrocorticographic (ECoG) grids are placed subdurally on the cortex in people undergoing cortical resection to delineate eloquent cortex. ECoG signals have high spatial and temporal resolution and thus can be valuable for neuroscientific research. The value of these data is highest when they can be related to the cortical anatomy. Existing methods that establish this relationship rely either on post-implantation imaging using computed tomography (CT), magnetic resonance imaging (MRI) or X-Rays, or on intra-operative photographs. For research purposes, it is desirable to localize ECoG electrodes on the brain anatomy even when post-operative imaging is not available or when intra-operative photographs do not readily identify anatomical landmarks.


METHODS
We developed a method to co-register ECoG electrodes to the underlying cortical anatomy using only a pre-operative MRI, a clinical neuronavigation device (such as BrainLab VectorVision), and fiducial markers. To validate our technique, we compared our results to data collected from six subjects who also had post-grid implantation imaging available. We compared the electrode coordinates obtained by our fiducial-based method to those obtained using existing methods, which are based on co-registering pre- and post-grid implantation images.


RESULTS
Our fiducial-based method agreed with the MRI-CT method to within an average of 8.24 mm (mean, median = 7.10 mm) across 6 subjects in 3 dimensions. It showed an average discrepancy of 2.7 mm when compared to the results of the intra-operative photograph method in a 2D coordinate system. As this method does not require post-operative imaging such as CTs, our technique should prove useful for research in intra-operative single-stage surgery scenarios. To demonstrate the use of our method, we applied our method during real-time mapping of eloquent cortex during a single-stage surgery. The results demonstrated that our method can be applied intra-operatively in the absence of post-operative imaging to acquire ECoG signals that can be valuable for neuroscientific investigations.
Dept. of Neurology, Albany Medical College, Albany, NY, USA ; Neural Injury and Repair, Wadsworth Center, New York State Dept. of Health, Albany, NY, USA ; Early Brain Injury and Motor Recovery Lab, Burke-Cornell Medical Research Institute, White Plains, NY, USA.
Disha
D
Gupta
Neural Injury and Repair, Wadsworth Center, New York State Dept. of Health, Albany, NY, USA ; Translational Neurological Research Laboratory, Helen Hayes Hospital, West Haverstraw, NY, USA.
N Jeremy
NJ
Hill
Dept. of Neurosurgery, Albany Medical Center, Albany, NY, USA.
Matthew A
MA
Adamo
Dept. of Neurology, Albany Medical College, Albany, NY, USA.
Anthony
A
Ritaccio
Dept. of Neurology, Albany Medical College, Albany, NY, USA ; Neural Injury and Repair, Wadsworth Center, New York State Dept. of Health, Albany, NY, USA ; Dept. of Neurosurgery, Washington University, St. Louis, MO, USA ; Dept. of Biomed. Eng., Rensselaer Polytechnic Institute, Troy, NY, USA ; Dept. of Biomed. Sci., State Univ. of New York at Albany, Albany, NY, USA ; Dept. of Elec. and Comp. Eng., Univ. of Texas at El Paso, El Paso, TX, USA.
Gerwin
G
Schalk
D000328:Adult; D001863:Bone Screws; D001931:Brain Mapping / Q000295:instrumentation* / Q000379:methods; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D002648:Child; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods
Auditory processing; Electrocorticography (ECoG); Electrode localization; Fiducials; interaoperative localization