Phantom Quantification of Magnetoencephalography Source Imaging Distortion Caused by Deep Brain Stimulation

Objective: Previous studies of deep brain stimulation-related (DBS) artifacts in magnetoencephalography (MEG) have largely focused on the sensor level. In contrast, far less is known about their effects at the source level, where neuroscientific interpretations are typically derived. This study aims to quantify how DBS artifacts distort source-level MEG imaging. Methods: The study used a phantom-based experimental setup to assess dipole-fitting accuracy while systematically varying the stimulation amplitude, DBS electrode configuration, and the distance between the dipole and the DBS electrode. Results: Dipole location, angle, and amplitude errors remained within modest ranges, with the largest location and angle errors occurring at 5 mA ring-electrode stimulation (6.19 mm and 8.31 deg, respectively) and the largest amplitude errors at 15 mA ring electrodes (13.05 nAm). Location and angle errors increased significantly as the dipole moved closer to the DBS electrode, while amplitude error showed no such relationship. Continuous head position indicator coil signal quality remained stable and reliable at DBS on condition, compared to DBS off. Conclusions: The stimulation itself does not significantly impair MEG dipole estimation, as fitting errors are similar with DBS on and off. The study introduces a quantitative framework to systematically assess DBS-related distortion via dipole-fitting error, which can also be extended to evaluate noise from other implanted or external devices.