IMG-124. BrainTRACE enables reliable electrocorticography localization in patients with brain tumors

BACKGROUND Precise localization of intra-operative electrocorticography (ECoG) electrodes is essential for functional mapping during brain tumor surgery. Traditional methods for ECoG electrode localization include extra-operative computed tomography (CT) scans, standard in epilepsy cases. However, this method is impractical and error-prone in tumor patients with distorted neuroanatomy or without chronically implanted electrodes. To address this, we developed BrainTRACE (Brain Tumor Registration and Cortical Electrocorticography), an open-source MATLAB software that integrates pre-operative MRI, vascular reconstructions, and intraoperative photographs to register subdural grids without extra-operative imaging. METHODS Ten adults with diffuse glioma or brain metastasis undergoing awake craniotomy were recorded using 20- or 96-contact subdural electrode arrays. Three experts (including a research technician and two faculty) and four novices (including an undergraduate student and three medical students) localized electrodes with BrainTRACE, guided by sulcal and vascular landmarks on intraoperative photos. Accuracy (mean Euclidean distance to expert consensus), inter-rater reliability (intraclass correlation, ICC), and placement time were quantified. Three cortical-reconstruction pipelines (FreeSurfer recon-all, recon-all-clinical, ANTsBrainExtraction) were evaluated for performance. RESULTS Expert users achieved 4.3 mm mean deviation from consensus (ICC = 0.934), whereas novices showed 16.3 mm mean deviation (ICC = 0.399). Novice speed improved from 59.2 min on the first case to 31 min on the tenth, approaching expert times (28.8 min). FreeSurfer recon-all-clinical yielded the most anatomically faithful cortical surface reconstruction. Add-ons enabling alignment of “grid-on” and “grid-off” photographs further enhanced accuracy in complex cortical geometries. CONCLUSION BrainTRACE enables sub-5 mm, CT-free ECoG localization in tumor patients and supports rapid user training. However, the low inter-rater reliability among novice users highlights the non-trivial nature of this task. BrainTRACE addresses a critical gap in standardizing high-fidelity electrode localization across institutions, facilitating the acquisition of high-quality electrophysiological data that can improve our understanding of neural processes and pathological conditions in research contexts.