Whole cortex, 64 channel SQUID biomagnetometer system

The authors report on the development and testing of a novel, whole cortex, 64-channel superconducting quantum interference device (SQUID) biomagnetometer system operating in an unshielded environment. The essential features of this instrument, including the cryogenics system, the room-temperature digital electronics, and signal processing capabilities, are described. A noise cancellation scheme is incorporated which allows extraction of biomagnetic signals over the surface of the cortex while operating in the presence of large background magnetic interference. A system description and the results of preliminary magneto-encephalographic measurements are presented. Measurements of noise performance and human auditory evoked response in an unshielded industrial environment have largely validated the noise cancellation methods incorporated in the instrument.<
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