Yttrium-Iron Garnet Magnetometer in MEG: Advance towards Multi-Channel Arrays

Recently, a new kind of sensor applicable in magnetoencephalography (MEG) has been presented: a solid-state yttrium-iron garnet magnetometer (YIGM). The feasibility of yttrium-iron garnet magnetometers (YIGMs) was demonstrated in an alpha-rhythm registration experiment. In this paper, we propose the analysis of lead-field matrices for different possible multi-channel on-scalp sensor layouts using YIGMs with respect to information theory. Real noise levels of the new sensor were used to compute signal-to-noise ratio (SNR) and total information capacity (TiC), and compared with corresponding metrics that can be obtained with well-established MEG systems based on superconducting quantum interference devices (SQUIDs) and optically pumped magnetometers (OPMs). The results showed that due to YIGMs' proximity to the subject's scalp, they outperform SQUIDs and OPMs at their respective noise levels in terms of SNR and TiC. However, the current noise levels of YIGM sensors are unfortunately insufficient for constructing a multichannel YIG-MEG system. This simulation study provides insight into the direction for further development of YIGM sensors to create a multi-channel MEG system, namely, by decreasing the noise levels of sensors.

Automated summary

Recently, a new kind of sensor called solid-state yttrium-iron garnet magnetometer (YIGM) has been used in magnetoencephalography (MEG). Its feasibility was demonstrated in an experiment recording alpha-rhythm. This paper analyzes lead-field matrices for different possible on-scalp sensor layouts using YIGMs, comparing it with existing MEG systems based on SQUIDs and OPMs in terms of signal-to-noise ratio (SNR) and total information capacity (TiC). The results show that YIGMs outperform SQUIDs and OPMs at respective noise levels, but the current noise levels of YIGM sensors are insufficient for constructing a multichannel YIG-MEG system.