SU‐E‐I‐90: Magnetoencephalography (MEG): Quantitative Comparison of Oscillations and Synchronization Differences/similarities in Post‐Surgery/pre‐Irradiation Patients and Control Subjects

Abstract

Purpose: To evaluate brain synchronization and connectivity differences in post‐surgery/per‐irradiation patients and healthy controls with two different MEG approaches: ECD (equivalent current dipole) and SAM (synthetic aperture magnetometry). Methods: An 8 min resting state scan was collected from 5 post‐surgery/pre‐irradiation patients and 5 sex/age‐matched control subjects. Scans were collected on a CTF MEG 275‐sensors system. All subjects were scanned in upright, open‐eyes position in a magnetically shielded room. MRI whole brain volume was divided into 4mm voxels allowing sensor signal space to be mapped into brain space. Measured signals were filtered into Δ, o/, α and β bandwidths and localized by ECD and SAM. SAM is a type of beamforming, a signal processing technique for sensor array data; the method works like a digital filter by focusing on each voxel while attenuating the majority of signal from all other voxels. Resultant SAM waveforms were evaluated to reject muscle and/or non‐physiological artifacts. The ECD method was applied to the same data and bandwidths to localize sources, its orientations and strengths. Statistical analysis evaluated connectivity and synchronization using dPLI (direct phase lag index) and IC (imaginary coherence). Resultant SAM and ECD maps were compared for differences and similarities. Results: Currently the project is collecting data. The full per‐irradiation data is expected to be completed by June 2013. The study goal is to establish the best method/approach to evaluate resting state MEG data. Conclusion: We expect 3 possible outcomes of the study: no difference, subtle difference, statistically significant difference in resting state analysis between these two methods. The two first outcomes are easy to address by choosing the most time‐efficient method. The last case will require further investigation of both methods to establish the ground of the difference and the most appropriate method analysis for the resting state. Partial support by Radiation Oncology and Neurology Departments at Wake Forest Baptist Health System and by Dalton McMichael Fund in Cancer Research. No conflict of interest is reported.