A 7-Channel High-[Formula: see text] SQUID-Based On-Scalp MEG System

Area of Science:

• Biophysics
• Neuroscience
• Sensor Technology

Background:

• Magnetoencephalography (MEG) traditionally requires bulky, magnetically shielded rooms.
• On-scalp MEG offers potential for more portable and accessible brain activity monitoring.
• High critical temperature (high-Tc) superconducting quantum interference devices (SQUIDs) are promising for compact sensor development.

Purpose of the Study:

• To present the technical design of a multi-channel on-scalp MEG system.
• To demonstrate the feasibility of using high-Tc SQUIDs for on-scalp magnetoencephalography.
• To characterize the performance of a 7-channel system for brain activity recordings.

Main Methods:

• Developed a liquid nitrogen-cooled cryostat housing seven YBCO SQUID magnetometers.
• Arranged sensors in a dense, head-aligned array with minimal scalp standoff (1-3 mm).
• Characterized system performance, including noise levels and crosstalk, and recorded brain activity.

Main Results:

• Achieved sensor spacing of 12.0-13.4 mm with a 1-3 mm scalp distance.
• Cryostat provided 16-hour operation with a single liquid nitrogen fill.
• Demonstrated sensitive detection of evoked auditory fields and alpha modulation with low noise levels (50-130 fT/Hz^1/2 at 10 Hz).

Conclusions:

• The 7-channel high-Tc SQUID system meets the requirements for on-scalp MEG.
• The system enables sensitive neuromagnetic field sampling with minimal scalp distance.
• This represents the first multi-channel high-Tc SQUID-based on-scalp MEG system, paving the way for future research.