A nine channel DC SQUID system for biomagnetism

In the last few years several multi-channel systems for biomagnetic measurements have been developed. The first examples featured four-five sensors (Ilmoniemi et al., 1984; Romani, 1984; Williamson et al., 1984), whereas more recently a seven-channel system became commercially available, also in a configuration which endowes simultaneous investigation at 14 scalp sites with two twin systems (Biomagnetic Technologies Inc.). However several projects aimed to develop larger systems are being carried on in several countries both by groups involved in fundamental research and by industries. In general, these systems are designed to be used for neuromagnetic studies, even if efforts are being made also to setup large size cardiomagnetometers (Erne', personal communication). A common feature is that all systems are planned to work in shielded environments.