A modified electrode cap for EEG recordings in MRI scanners

A stretchable electrode cap containing 64 electrodes was modified to make it compatible for functional magnetic resonance imaging (fMRI). Metallic components were individually tested for magnetic susceptibility, and those that perturbed a free-swinging magnet or moved in a strong magnetic field were replaced with non-ferromagnetic components. Studies with a phantom indicate that placement of the cables carrying signals from the cap to the amplifiers can significantly affect MR image quality. Anatomical and functional images obtained with the modified electrode cap show modest signal loss, but not enough to substantially interfere with the low-noise images required for fMRI. The cap enables faster application of large arrays of electrodes in conjunction with MRI studies, and thus makes combined EEG/fMRI studies more practical, especially those with EEG source localization as one of the goals.