Neuromagnetic recordings of the human peripheral nerve with planar SQUID gradiometers

• Published in: Physics in medicine & biology 1998-08, Vol.43 (8), p.2379-2384
• Main Authors: Lang, G, Shahani, U, Weir, A I, Maas, P, Pegrum, C M, Donaldson, G B
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biothermics. Biomagnetism. Bioelectricity; Equipment Design; Fundamental and applied biological sciences. Psychology; Humans; Magnetics; Neuroradiography - instrumentation; Neuroradiography - methods; Peripheral Nerves - diagnostic imaging; Peripheral Nerves - physiology; Tissues, organs and organisms biophysics; Ulnar Nerve - diagnostic imaging; Ulnar Nerve - physiology
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/0031-9155/43/8/027

Magnetic fields produced by a travelling volley in the human ulnar nerve have been successfully measured in a lightly shielded environment. Recordings of the tangential component of the magnetic field were made using a planar second-order gradiometer integrated with a first-order gradiometric superconducting quantum interference device (SQUID). Devices were fabricated in our clean-room facility at the University of Strathclyde and measurements taken in an eddy-current shielded room at the Wellcome Biomagnetism Unit. We use no additional shielding and no electronic differencing or field-nulling techniques. Evoked magnetic fields of 60 fT peak-to-peak were obtained after 1536 averages but they could be seen easily as early as 512 averages. Measurements were made over four points above the ulnar nerve on the upper arm and from these the conduction velocity was calculated as 60 m s(-1).