Capabilities of a Toroid-Amplifier System for Magnetic Measurement of Current in Biological Tissue

Bioelectric current in one-dimensional tissues can be measured by using a room temperature amplifier and a wire-wound, ferrite-core toroid to detect the associated biomagnetic field. In this paper, the capabilities of such a toroid-amplifier system are discussed, with emphasis placed on the signal-to-noise ratio and the spatial resolution of the toroid. Use of this system for measuring current is studied in detail for cardiac and skeletal muscle, and myelinated and nonmyelinated nerve axons. Finally, factors affecting the sensitivity of openable toroids are considered.