The recent development of large multi-channel biomagnetic systems, with 20-30 adjacent magnetic sensors, is marking a significant progress in the detection and interpretation of biomagnetic signals, and definitely traces a new avenue towards a proper assessment of the technique in the clinical field. Several technological problems are being solved, mainly concerning the reliability of the SQUIDs and of the superconducting assembly, as well as the criogenic dewar. Also the choice of the geometry for the gradiometers to be coupled to the SQUIDs has a fundamental importance, not only from a technological point of view, but also in that it affects the localization properties of the system. The major attractions and drawbacks of both vertical and planar configurations will be briefly reviewed and few practical suggestions to overcome some of the difficulties will be proposed.
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