Phantom study supports claim of accurate localization from MEG data

To evaluate the localization accuracy and precision of magnetoencephalography (MEG) for cortical and deep neural sources, we conducted a phantom experiment. We have used MEG data generated by current dipole-like sources in a spheroidal phantom. MEG signals were recorded by activating superficial and deep current generators implanted in the phantom, which were driven separately by weak, transient currents of varied strengths. The data were analyzed by four different modeling techniques. We evaluate and compare the localization accuracy obtained with the phantom data from previous studies of our laboratory. In these previous studies, we have demonstrated, by using fMRI sub-millimeter spatial resolution as a reference point that the localization accuracy of MEG with MFT, at least at the level of V1, is within a few millimeters. For the phantom data, overall high spatial resolution was demonstrated for isolated weak, transient, cortical and sub-cortical neural sources for each of the four source localization techniques. The differences between the methods were typically only a few millimeters. As expected localization, accuracy was reduced for deep sources. K eywords: MEG, localization accuracy, phantom, fMRI