Systematic dry phantom design for OPM-MEG source localization evaluation

A phantom is an essential tool for evaluating the localization accuracy of magnetoencephalography (MEG) systems. However, the structures of the phantom coils can introduce additional measurement errors during MEG localization testing. Despite its significance, optimal strategies for designing dry phantoms that are specifically adapted to different MEG systems and capable of minimizing such errors have not been fully explored. This study employed a simulation model based on an optically pumped magnetometer MEG (OPM-MEG) system to quantitatively characterize the spatial distribution of localization errors and to guide the design of coil placement. To assess the influence of reference location accuracy on source localization, a comprehensive analysis of error sources in phantom-based MEG testing was conducted, focusing on the role of phantom design in localization outcomes. The impact of reference location coordinate accuracy on localization performance was further validated through experimental testing. Based on the simulation and experimental results, a systematic design methodology for a dry phantom system using triangular coils is proposed. This approach includes both a coil placement strategy adapted to the OPM array and a structural design framework for the triangular coil assembly. The methodology improves the accuracy of MEG calibration tests and establishes a reproducible quality-control framework for pre-clinical OPM-MEG deployment and cross-site comparability.