Measurements of biomagnetic fields using a high-resolution dc superconducting quantum interference device magnetometer

We have developed a multichannel high-resolution superconducting quantum in terference device magnetometer for measuring biomagnetic fields produced by small animals. We measured the magnetocardiogram produced by a rat. Topogr aphies of the P wave, QRS wave, and T wave of the rat magnetocardiogram wer e obtained. We also measured the magnetoretinogram, visually evoked magneti c fields, and auditory evoked magnetic fields of the rat. The signals of th e magnetoretinogram appeared at 60 ms latency and the field intensities wer e about 0.6 pT. It was not possible to obtain the clear visually evoked fie lds because those signals were hidden behind the magnetoretinogram. It was possible to obtain auditory evoked magnetic fields of the rat. The signific ant differences of the wave forms were observed in both sides of the right ear, which are separated by 15 mm. Our system has adequate spatial resoluti on for measurement of the magnetocardiogram and auditory evoked magnetic fi elds produced by small animals. (C) 1998 American Institute of Physics. [S0 021-8979(98)39211-7].