1. Jeffrey M Politsky, MD FRCP(C) Northeast Regional Epilepsy Group Atlantic Neuroscience institute

2. Windows to the human brain Anatomical Computerized X-ray Tomography (CT) Magnetic Resonance Imaging (MRI) Functional, metabolic activity/blood flow Positron Emission Tomography (PET) Functional MRI (fMRI) Near Infrared Spectroscopy (NIRS) Functional, information processing Electroencephalography (EEG) Magnetoencephalography (MEG)

3. Summary  3-T MRI  V-EEG (at least 5 seizures separated over time)  PET  MEG  Functional Mapping  Intra-cranial Monitoring

4. Comparison of Methods

5. Comprehensive Epilepsy Center  MEG a technique for mapping brain activity by recording magnetic fields produced by inherently occurring electrical currents in the brain using arrays of SQUIDS (superconducting quantum interference devices); Main Clinical Applications: ○ Epilepsy Localization ○ Functional brain mapping prior to brain tumor/lesion resection; Clinical Research Applications: perceptual and cognitive brain processes; Psychiatric conditions, Autism Traumatic brain injury

6. First MEG (MIT – 1970’s) David Cohen and Jim Zimmerman

7. Failed ideas Dual 14 (28)-Channel MEG System (1987)

8. Historical Development 1983 by HUT 4 channels 30 mm in diameter (coverage: 7 cm 2 ) Axial 1986 by HUT 7 channels 93 mm in diameter (coverage: 68 cm 2 ) Axial 1989 by HUT 24 channels 125 mm in diameter (coverage: 123 cm 2 ) Planar 1992 by Neuromag 122 channels whole head (coverage: 1100 cm 2 ) Planar 12 Deliveries 1998 by Neuromag 306 channels whole head (coverage: 1220 cm 2 ) Planar gradiometers & Magnetometers

9. Patient undergoing MEG

10. MEG door

11. Magnetic fields

12. The MEG (and EEG) signals derive from the net effect of ionic currents flowing in neuronal dendrites during synaptic transmission.