Restoration of electrophysiological signals distorted by inductive effects of magnetic field gradients during MR sequences

A generally applicable method for almost complete suppression of signal artifacts on electrophysiological signals caused by B0-gradient switching (gradient noise) is presented. The method is demonstrated for electrocardiograms (ECGs) but can also be used for other electrophysiological signals. It takes advantage of the fact that under certain conditions, the effect of switching the B0-field gradient upon an electrophysiological signal can be modeled as a linear time-invariant system and fully characterized by pulse response functions. It is shown how the system's pulse response functions of the X, Y, and Z gradients can be determined and how gradient noise can be eliminated efficiently. The elimination of gradient noise by the proposed method causes in the current arrangement a constant delay of 128 msec, which is acceptable for patient monitoring and magnetic resonance sequence triggering.