Abstract: An MRI system includes a detector system which receives an ECG signal from a patient being scanned and produces a gating signal. The gating signal is produced when a detected peak in the ECG signal meets a set of R-wave criteria which includes a specified positive slope on the leading segment of the detected peak, a minimum duration of the leading segment, specified negative slope on the segment trailing the detected peak and a minimum peak amplitude.

Abstract: An adaptive filtering system is used to reduce the electrical noise on low power ECG signals and the like as generated by rapidly switched magnetic gradient fields in magnetic resonance imaging. A correlated noise reference signal is derived from the inputs to the gradient coils by a combination differentiator and low pass filter. The noise reference signal is received by a filter having adjustable coefficients and the result subtracted from the low power signal to produce an error signal used to adjust the coefficients of the filter. Three separate adaptive filters may be placed in series each with a separate correlated noise reference signal to reduce the noise from three gradient coils.