Phantom-Based Approach for Comparing Conventional and Optically Pumped Magnetometer Magnetoencephalography Systems.

Area of Science:

• Neuroscience
• Biophysics
• Biomedical Engineering

Background:

• Magnetoencephalography (MEG) measures neural activity via magnetic fields.
• Superconducting Quantum Interference Devices (SQUIDs) and Optically Pumped Magnetometers (OPMs) are key MEG sensor technologies.
• Direct hardware-level comparisons of SQUID and OPM systems using controlled phantoms are lacking.

Purpose of the Study:

• To establish a framework for direct hardware-level comparison of SQUID-MEG and OPM-MEG systems.
• To evaluate sensor performance using a dry phantom simulating neuronal activity.
• To identify factors influencing source localization accuracy in both MEG systems.

Main Methods:

• A dry phantom designed to emulate neuronal activity was used.
• Data were acquired simultaneously from SQUID and OPM-MEG systems within a magnetically shielded room.
• Environmental noise and shielding conditions were kept consistent for both systems.

Main Results:

• OPM sensors, positioned closer to the source, yielded signal amplitudes 3-4 times greater than SQUID sensors.
• OPM-MEG systems exhibited a source localization error approximately three times larger than SQUID-MEG systems.
• Factors such as sensor-to-source distance, sensor count, SNR, and spatial coverage influenced OPM localization error.

Conclusions:

• This study provides a novel hardware-level comparison of SQUID and OPM-MEG technologies using a controlled phantom.
• While OPMs offer superior signal amplitude, SQUIDs currently provide higher source localization accuracy.
• Further research is needed to optimize OPM system configurations for improved spatial resolution in MEG.