ECG enhancement by adaptive cancellation of electrosurgical interference
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorBernard Widrow
Life of this patent
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Abstract
A technique utilizing a combination of adaptive noise cancelling and conventional signal processing is developed to enhance electrocardiographic monitoring in the operating room by reducing the noise interference that is created by an electrosurgical instrument. Significant amounts of interference are eliminated by radio frequency shielding, passive and active lowpass filtering and optical isolation. A digital adaptive canceller using the least-mean-square algorithm is used to reduce the remainder of the interference, yielding an improvement in signal-to-noise ratio of approximately 100 dB.
Claims11
In a patient monitoring system, means for improving the signal-to-noise ratio, comprising
- (a) means for detecting primary signals from a patient comprising a desired signal and a noise signal,
- (b) means for detecting a reference signal from the patient comprising substantially only said noise,
- (c) means for filtering said patient originated signals;
- and
- (d) adaptive filter means comprising
- (i) adaptive means responsive to the reference signal for continuously generating a reference noise signal comprising an estimate of the noise in the primary signal received at an input of said adaptive filter;
- and
- (ii) means for subtracting said reference noise signal from said primary patient originated signal to provide an accurate representation of said desired signal.
A method of reducing noise in signals detected on a patient being monitored, comprising
- (a) connecting a first pair of electrodes to the patient to detect a primary patient signal comprising both interference and a desired signal;
- (b) connecting a second pair of electrodes to the patient in a position to detect a reference patient signal comprising approximately only the interference signal;
- (c) filtering said primary and reference patient signals to reduce RF interference;
- (d) filtering the reference signal to obtain a signal representing the remaining interference component of said primary signal;
- (e) subtracting said remaining interference representing signal from said filtered patient signal to remove interference components from said patient signal.
Dependencies are inferred from the claim text.