Electrocorticogram (ECoG) signals are acquired from electrodes that are surgically implanted into the subdural space of the brain. Although this procedure is usually performed for clinical purposes such as defining seizure locations and/or brain mapping, ECoG signals can also be used for characterizing the electrophysiology underlying various behaviors or for brain-computer interface applications. Therefore, defining the anatomical location of ECoG electrodes is an important process for contextual interpretation of the results. Current techniques utilize semi-automated statistical methods to co-register ECoG electrodes from either post-implantation X-rays or computer tomography (CT) images with a pre-implantation magnetic resonance imaging (MRI) of the brain. However, due to brain deformation caused by surgical electrode implantation, ECoG electrode locations must be projected onto the brain surface of the pre-implantation MRI, which may result in error. The authors present an exploratory study where post-implantation MRI images were successfully used for co-registration with post-implantation CT images of ECoG electrodes without the need for projection. By using postimplantation CT and MRI images which preserve the brain deformation, error in defining ECoG electrode locations may be reduced or eliminated.
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