Development of a 61-Channel MEG System Cooled by a GM/JT Cryocooler

Abstract

Most SQUID-based systems used for biomagnetic measurements require liquid helium to achieve a low temperature environment However, cryogenic temperatures can now be easily attained by using commercially available cryocoolers, thus eliminating the need for handling liquid helium. Sullivan et al. [1] and Kang et al. [2] successfully demonstrated that a SQUID system can be cooled using a cryocooler. We, previously developed a single- Channel system [3] and a 32-channel system [4] that are cooled by GM/JT (Gifford-McMahon/ Joule-Thomson) cryocoolers and therefore do not need liquid helium. Here we designed a new 61-Channel MEG system cooled by a GM/JT cryocooler. To demonstrate its Performance, we measured the somatosensory-evoked magnetic field in a human subject using our 32-channel MCG system [4], which has a structure similar to that for our new MEG system.