Noise-free magnetoencephalography recordings of brain function

Area of Science:

• Biophysics
• Neuroimaging
• Biomedical Engineering

Background:

• High-quality magnetoencephalography (MEG) recordings are often hindered by ambient magnetic field noise.
• Existing MEG systems face challenges in effectively mitigating environmental magnetic interference.

Purpose of the Study:

• To develop and evaluate a novel whole-head MEG system designed to overcome ambient magnetic field noise.
• To enhance the signal-to-noise ratio (SNR) of MEG recordings through advanced shielding and noise cancellation techniques.

Main Methods:

• Implementation of a whole-head MEG system featuring a superconducting imaging surface (SIS) enclosing an array of superconducting quantum interference device (SQUID) magnetometers.
• Utilizing SQUID reference sensors on the exterior of the SIS for ambient field measurement.
• Employing an adaptive algorithm to estimate and subtract ambient noise contributions from MEG sensor data.

Main Results:

• The SIS passively shields the SQUID array, achieving 25-60 dB noise reduction.
• Demonstrated total ambient noise reduction factors exceeding 10^6 (> 120 dB).
• Achieved residual noise levels at or near the intrinsic SQUID noise floor (2-3 fT Hz-1/2), surpassing equivalent electroencephalography (EEG) SNR.

Conclusions:

• The developed whole-head MEG system effectively mitigates ambient magnetic field noise.
• This technology enables MEG recordings with significantly improved signal-to-noise ratios compared to conventional methods.
• The system holds promise for advancing neuroimaging research by providing cleaner and more precise brain activity measurements.