High-Resolution Measurements of Biomagnetic Fields

Attempts to understand the fundamental determinants of magnetic fields produced by bioelectric activity have been hindered by the low spatial resolution and 1 cm or greater Dewar thickness of conventional SQUID biomagnetometers. To overcome this and provide data for our model studies of the relationship of bioelectric and biomagnetic fields, we have built both superconducting and semiconductor magnetometers with small, room-temperature, toroidal pickup coils. We can readily measure cellular action currents in isolated nerve and muscle preparations, and are evaluating this instrument for use during neurosurgical repair of damaged peripheral nerves in humans. To analyze the 2 and 3-dimensional current distributions in the exposed, in vivo heart and brain, we are considering high-resolution SQUID systems, hopefully with coil diameters of only several millimeters and a similar coil-to-animal spacing.

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