[Magnetoencephalography: its principles and clinical application].
This review attempts to provide the basis of neuromagnetism and its clinical applications. The progress in this field has been connected with the introduction of SQUID (superconducting quantum interference device) magnetometer which was produced by the progress of low temperature physics. A magnetic field is generated by an electric current in accordance with 'the right hand law', and the magnetic field pattern inevitably crosses orthogonally that of the electric field. A SQUID magnetometer is able to only detect the magnetic field which is generated by the current dipole orientated parallel to the skull surface. Magnetoencephalography (MEG) has several advantages compared to electroencephalography (EEG). One is its more excellent spatial resolution than that of EEG, and the other is a non-contact measurement, i. e., a noninvasive method. Therefore, MEG measurement could not interfere with sweating on the skull skin or a depolarization between skin and electrodes. This advantage allows it to record the magnetic field generated by the direct current potential in the cortical surface, and one example, that is, direct current magnetic fields evoked by slow potential changes in rat brain during asphyxia, are shown.
Takanashi
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Department of Neurology and Gerontology, Kyoto Prefectural University of Medicine.
D000818:Animals; D002540:Cerebral Cortex / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials; D006801:Humans; D015225:Magnetoencephalography / Q000295:instrumentation; D051381:Rats