Biplanar Nulling Coil System for OPM-MEG Using Printed Circuit Boards.

Area of Science:

• Biophysics
• Neuroscience
• Electrical Engineering

Background:

• Optically pumped magnetometers (OPMs) are a promising technology for magnetoencephalography (MEG).
• Previous OPM systems required expensive, manually wound background field-nulling coils.
• These coils were difficult to produce and prone to errors.

Purpose of the Study:

• To develop a precise, reproducible, and cost-effective manufacturing process for biplanar background field-nulling coils for OPM-MEG.
• To enable OPM-MEG systems to operate effectively in lightly shielded rooms.

Main Methods:

• Fabricated biplanar nulling coils on two-layer printed circuit boards (PCBs).
• Utilized open-source software (bfieldtools) to optimize current loops and create a continuous conducting path across PCB layers.
• Assembled coils from pairs of PCBs and mounted them on an aluminum frame.

Main Results:

• Achieved coil efficiencies of 1.3-7.1 nT/mA, comparable or superior to previous designs.
• Reduced the largest background magnetic field component from 21 nT to 2 nT.
• Recorded somatosensory evoked fields (SEFs) with OPMs in a lightly shielded room, achieving results comparable to SQUID-MEG.

Conclusions:

• The developed PCB coil system offers a cheaper, open-source alternative to commercial coils.
• This facilitates more affordable background field nulling for OPM-MEG.
• The technology enhances the accessibility of OPM-MEG for human neuroscience research.