Co-Registration Error Analysis and Array Calibration for OPM-MEG System

Optically pumped magnetometer (OPM-magneto- encephalography (MEG) source localization necessitates precise co-registration of the MRI and MEG sensor array. The co-registration error decreases the spatial resolution of MEG source estimation. To clarify and reduce the co-registration error, the data acquisition and co-registration processes are theoretically modeled and analyzed in this article. The results show that the error caused by the substituting of the designed sensor array model for the manufactured array in data acquisition is widely ignored. The amount of data used for transformation calculation is a decisive factor for the transformation accuracy. The error sources of co-registration in the OPM-MEG system are analyzed. The position error and orientation error of the sensitive axis of the sensor are two main error sources. In the range of 250 mm, the calibration experiment achieves a position accuracy of 2.5 mm and an orientation accuracy of 2° of the sensor sensitive axis. Real-time acquisition and correction of sensor position and orientation in the OPM-MEG array can be realized by optimizing the configuration of calibration scheme, and the accuracy of the OPM-MEG source localization can be improved.