Superconducting quantum interference device (SQUID)-based magnetoencephalography (MEG) holds substantial clinical value in epilepsy examination but is limited by the high costs. The optically pumped magnetometer (OPM)-based MEG appears promising in overcoming these limitations. This study aims to explore the consistency of interictal epileptiform discharge (IED) detection and source localization between OPM-MEG and SQUID-MEG in a large cohort of patients with epilepsy. Patients with epilepsy underwent SQUID-MEG and 128-channel whole-scalp OPM-MEG examinations. IED detection, amplitude, signal-to-noise ratio (SNR), sensor-scalp distance, and source localization results were compared between OPM-MEG and SQUID-MEG through statistical analysis. The cohort comprised 46 patients with epilepsy (mean age, 23.7 ± 8.7 [SD] years; 29 male). McNemar χ² test indicated no significant difference for IED detection between two systems. OPM-MEG achieved a detection accuracy of 91.3% compared with SQUID-MEG; a Gwet's first-order agreement coefficient (AC₁) of 0.892 suggested good consistency. Among 39 patients with IEDs detected by both systems, OPM-MEG demonstrated closer sensor-scalp distance (p < 0.001), higher IED amplitude (p < 0.001) and SNR (p = 0.003) compared with SQUID-MEG. At the sublobar level, OPM-MEG and SQUID-MEG exhibited nearly consistent source localization results. Among 24 patients with single dipole clusters, the average centroid distance between dipole clusters of OPM-MEG and SQUID-MEG was 12.16 ± 5.90 mm. This real-world study demonstrated that OPM-MEG had comparable applicability in IED detection and source localization, compared with SQUID-MEG. Additionally, OPM-MEG performed better in terms of IED amplitude and SNR. Lower costs and user-friendly features highlight the clinical potential of OPM-MEG in epilepsy assessments.

Accurately localizing brain motor areas is vital for protecting motor function during neurosurgical procedures. Magnetoencephalography (MEG) based on optically pumped magnetometer (OPM) improves the availability of MEG in clinical applications. The aim of this study is to evaluate the availability, accuracy and precision of "OPM-MEG" for localizing motor areas in brain tumor patients and healthy individuals. Participants were enrolled and subjected to primary motor area localization by both 3T-fMRI and 128-channel OPM-MEG examinations. The localization accuracy (ability of mapping on the anatomical location) and precision (activation signal centralization) were compared between the two methods, and accuracy was further validated by intraoperative direct cortical electrical stimulation (DCS) on the localized area with assistance of neuro-navigation system. A total of 12 participants (7 brain tumor patients and 5 healthy individuals) were enrolled and all had successful localization for motor areas by both methods. The average time of OPM-MEG examination for each limb function was approximately 9 minutes. The localizations by both methods mainly covered the anatomical location of primary motor cortex and were partially overlapped. The motor activation signal identified by OPM-MEG was more centralized than fMRI did. The centroid of motor area localized by the OPM-MEG deviated from it by fMRI, with a median distance of 19.7 mm and 27.48 mm for hand or foot localization, respectively. Furthermore, the OPM-MEG centroid for hand movement successfully triggered corresponding hand response by DCS. In this first-in-human study exploring the potential of OPM-MEG in functional localization of motor areas, we revealed its availability and reliability in mapping motor areas, demonstrating it as a promising tool in assisting neurosurgical practice and neuroscience research.

The channel count in an Optically Pumped Magnetometer Magnetoencephalography (OPM-MEG) system plays a pivotal role in determining its overall performance. While existing research consistently highlights that a greater number of channels enhances system capabilities, practical constraints such as sensor placement on the head, inter-channel interference, and cost-efficiency impose limitations on channel scalability. Additionally, the optimal channel count required for clinical applications of OPM-MEG remains unclear. In this study, we systematically investigate the impact of channel count on OPM-MEG performance by integrating simulations, phantom experiments, and human MEG experiments. Four configurations with varying channel counts (16, 32, 64, and 128) are evaluated. Specifically, systems with fewer channels (e.g., 16 channels) encounter significant challenges in meeting the demands of clinical MEG applications. In contrast, a 64-channel OPM-MEG system demonstrates performance metrics-such as signal-to-noise ratio (SNR) and localization accuracy-that are comparable to those of a 306-channel Superconducting Quantum Interference Device MEG (SQUID-MEG) system. Notably, a 128-channel OPM-MEG system surpasses the 306-channel SQUID-MEG system, achieving superior results. This work provides a detailed exploration of the relationship between channel count and OPM-MEG system performance, analyzing how many channels of the OPM-MEG system are suitable for clinical applications. By combining simulation-based evaluations with empirical measurements, we found that it is crucial to carefully select the appropriate number of channels based on the specific usage requirements in clinical applications.