LOCALIZATION OF INVASIVE ELECTRODES IN RELATION TO CORTICAL SURFACE ANATOMY
Abstract number :
1.220
Submission category :
Year :
2003
Submission ID :
1054
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Alexandre Bastos, Blaise M. Wheatley, Roch Comeau, Donald W. Gross Department of Radiology, University of Alberta, Edmonton, AB, Canada; Department of Surgery, University of Alberta, Edmonton, AB, Canada; Rogue Research Inc., Montreal, QC, Canada; Departm
Subdural grid electrodes are commonly used for localization of the seizure generator and cortical mapping in epilepsy patients being considered for resective surgery. A potential drawback of this method however, relates to the difficulty in identifying the position of electrodes in relation to brain surface anatomy. Previous studies using Curvilinear Multiplanar Reformatting (CMPR) have successfully addressed this issue. Nonetheless, local fluid collection and brain displacement still may prevent satisfactory electrode demonstration. This study aims to further improve grid localization by using technical advances in image acquisition and processing.
Two patients who were investigated with subdural grid electrodes had an MR examination following electrode placement. A 3.0 mm thick T2 weighted gradient-echo sequence was acquired along the axial plane, with no gap. The images were transferred to a workstation and resampled into 1 mm thickness. CMPR was then performed using a software implementation that provided minimal intensity projection of curved image slabs. In a subsequent step, the electrodes identified on the grid MRI dataset were registered into a pre-implantation volumetric MRI.
In both patients the images obtained allowed for accurate localization of the electrode grid, which was confirmed during surgery for removal of epileptogenic tissue.
The developed implementations helped to overcome common technical difficulties associated with demonstration of intracranial electrodes. Because of its simplicity and effectiveness, this method has become a routine procedure at our institution, allowing for accurate localization of grid electrodes thus enhancing interpretation of neurophysiologic data.