Jeffrey M Politsky, MD FRCP(C)

Northeast Regional Epilepsy Group

Atlantic Neuroscience institute

Windows to the human brainWindows 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)

Summary

3-T MRI V-EEG (at least 5 seizures separated

over time) PET MEG Functional Mapping Intra-cranial Monitoring

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MEGf MRI

CTMRI

PET

SPECTEEG

Temporal Resolution

Comparison of Methods

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

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

Failed ideas

Dual 14 (28)-Channel MEG System (1987)

Historical Development

1983by HUT4 channels30 mm in diameter(coverage: 7 cm2)Axial

1986by HUT7 channels93 mm in diameter(coverage: 68 cm2)Axial

1989by HUT24 channels125 mm in diameter(coverage:123 cm2)Planar

1992by Neuromag122 channelswhole head(coverage:1100 cm2)Planar12 Deliveries

1998by Neuromag306 channelswhole head(coverage:1220 cm2)Planar gradiometers &Magnetometers

Patient undergoing MEG

MEG door

Magnetic fields

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