Three-Dimensional Accuracy of ECOG Strip Electrode Localization Using Coregistration of Preoperative MRI and Intraoperative Fluoroscopy

Abstract

Background/Aims: Algorithms that estimate implanted cortical strip electrode coordinates using postoperative skull X-ray coregistration with preoperative magnetic resonance imaging (MRI) have been proposed. However, when cortical strip electrodes are inserted for temporary use and removed prior to closure, intraoperative imaging - either fluoroscopy or computed tomography (CT) - must be substituted. Objectives: To measure the accuracy of temporarily inserted subdural strip electrode coordinates using intraoperative fluoroscopic coregistration with preoperative MRI compared to intraoperative CT coregistration with preoperative MRI. Methods: In 5 patients undergoing movement disorder surgery, preoperative MRI was used to generate a three-dimensional cortical surface manually scaled to fit an intraoperative skull fluorogram with an in situ six-contact subdural electrode strip. Individual contact coordinates were estimated using subjacent gyral and sulcal patterns. Estimated coordinates were compared to reference coordinates obtained by preoperative MRI coregistration with intraoperative CT in the same patients. Results: Mean electrode coordinate distances between estimated and reference locations were 6.0 ± 0.8 (x-axis, mediolateral), 3.3 ± 0.5 (y-axis, anterior-posterior) and 4.0 ± 0.5 mm (z-axis, superior-inferior; n = 30). Conclusions: Localization of temporarily inserted subdural electrodes can be accomplished using preoperative MRI and intraoperative fluoroscopy. The accuracy of this approach is verified by preoperative MRI and intraoperative CT coregistration in the same patients.