ECG machine including filter for feature detection

• US 10,321,837 B2
• Filed: 04/28/2017
• Issued: 06/18/2019
• Est. Priority Date: 04/28/2017
• Status: Active Grant

• Current Assignee: Biosense Webster Israel Ltd. (Johnson & Johnson)
• Original Assignee: Biosense Webster Israel Ltd. (Johnson & Johnson)
• Inventors: Shilemay, Moshe Israel, Ephrath, Yaron, Khudish, Oleg
• Primary Examiner(s): Mahmood, Nadia A
• Application Number:
  US15/582,156
• Publication Number:
  US 20180310853A1
• Time in Patent Office: 781 Days
• Field of Search: 600523
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/339 Displays specially adapted therefor
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A system and method of filtering input data to remove power line interference is disclosed. The system and method estimates the statistics of the input signal and include determining a value (R) from the ratio of a peak amplitude (A_peak) and a root-mean-square of the amplitudes of the interference harmonics (A_rms), calculate a running histogram of the determined value (R) to determine a threshold value (TH_R), comparing the determined value (R) to the determined threshold value (TH_R) to make a decision about feature existence, and outputting a feature decision. The system and method include estimating the interference level to determine if interference is low level or high level. The system and method include estimating interference using the feature detection, amplitude and phase; and removing the estimated interference from the signal to result in a signal substantially free of power line interference.

Claims

1. A system for performing an electrocardiograph (ECG), the system comprising:

a plurality of leads for attaching to a subject in order to capture electric signals;

a signal processor to process the captured electrical signals by;

applying a comb filter to the captured electrical signals to emphasize interference at a plurality of selected frequencies;

estimating an amplitude and a phase of the applied filtered signals;

performing a first stage of filtering the applied filtered signals to remove power line interference using feature detection;

performing a second stage of filtering the applied filtered signals to remove power line interference using feature detection, the second stage including estimating the interference level to determine if interference is low level or high level;

estimating interference using the feature detection, amplitude and phase; and

removing the estimated interference from the signal to generate a signal substantially free of power line interference; and

an output device to output the process captured electrical signals.

2. The system of claim 1 wherein the first stage comprises:

determining a first value (R) from a ratio of a peak amplitude (A_peak) and a root-mean-square of the amplitude (A_rms);

calculating a running a histogram of the determined first values (R) to estimate a plurality of signal statistics and determine a threshold value (TH_R) accordingly;

comparing the determined value (R) to the determined threshold value (TH_R); and

outputting an feature decision based on the comparison.

3. The system of claim 1 further comprising, on a condition that there is low level interference in the estimate:

determine a root-mean-square of the amplitudes of the interference harmonics (A_rms);

calculate a running histogram of the determined root-mean-square of the amplitude (A_rms) to determine a threshold value (TH_rms);

compare the root-mean-square of the amplitude (A_rms) to the determined threshold value (TH_rms); and

outputting an feature decision based on the comparison.

4. The system of claim 1 further comprising, on a condition that there is high level interference in the estimate:

determine a first value (R_Fil) from a ratio of (first stage) filtered signal peak amplitude (A_Filpeak) and a root-mean-square of the amplitude (A_rms);

calculate a running histogram of the values (R_Fil) to determine a threshold value (TH_Fil);

compare the value (R_Fil) to the determined threshold value (TH_Fil); and

outputting an feature decision based on the comparison.

5. The system of claim 1 wherein the captured signals are further processed by estimating the frequency of the interference.

6. The system of claim 5 wherein the estimated frequency of the interference is utilized in the application of the comb filter.

7. The system of claim 5 wherein the estimated frequency of the interference is utilized in the estimate of the amplitude and phase.

8. The system of claim 1 wherein the output device provides at least one of a screen display and printed copy of the ECG.

9. A method for use in an ECG, the method comprising:

applying a comb filter to a received signal to emphasize interference at a plurality of selected frequencies;

estimating an amplitude and a phase of the applied filtered signal;

performing a first stage of filtering on the applied filtered signals to remove power line interference using feature detection;

performing a second stage of processing to the applied filtered signals to determine if the performed first stage misclassified a feature to further remove interference using feature detection, the second stage including estimating the interference level to determine if interference is low level or high level;

estimating interference using the feature detection, amplitude and phase of the signal; and

removing the estimated interference from the signal to generate a signal substantially free of power line interference.

10. The method of claim 9 wherein the first stage comprises:

determining a value (R) from a ratio of a peak amplitude (A_peak) and a root-mean-square of the amplitudes of the interference harmonics (A_rms);

calculating a running a histogram of the determined values (R) to calculate a cumulative distribution function (CDF) to determine a threshold value (TH_R);

comparing the determined value (R) to the determined threshold value (TH_R); and

outputting a feature decision based on the comparison.

11. The method of claim 9 further comprising, on a condition that there is low level interference in the estimate:

determine a root-mean-square of the amplitudes of the interference harmonics (A_rms);

calculate a running histogram of the determined root-mean-square of the amplitude (A_rms) to calculate a cumulative distribution function (CDF) to determine a threshold value (TH_rms);

compare the root-mean-square of the amplitude (A_rms) to the determined threshold value (TH_rms); and

outputting an feature decision based on the comparison.

12. The method of claim 9 further comprising, on a condition that there is high level interference in the estimate:

determine a value (R_Fil) from a ratio of (first stage) filtered signal peak amplitude (A_Filpeak) and a root-mean-square of the amplitude (A_rms);

calculate a running histogram of the values (R_Fil) to calculate a cumulative distribution function (CDF) to determine a threshold value (TH_Fil);

compare the value (R_Fil) to the determined threshold value (TH_Fil); and

outputting an feature decision based on the comparison.

15. The method of claim 9 further comprising estimating the frequency of the interference.

16. The method of claim 15 wherein the estimated frequency of the interference is utilized in the application of the comb filter.

17. The method of claim 15 wherein the estimated frequency of the interference is utilized in the estimate of the amplitude and phase.

13. A device for performing an electrocardiograph (ECG), the system comprising:

a signal processor to process captured electrical signals from a plurality of leads configured to be attached to a subject by;

applying a comb filter to the captured electrical signals to emphasize interference at a plurality of selected frequencies;

estimating an amplitude and a phase of the applied filtered signals;

performing a first stage of filtering the applied filtered signals to remove power line interference using feature detection;

performing a second stage of filtering the applied filtered signals to remove power line interference using feature detection, the second stage including estimating the interference level to determine if interference is low level or high level;

estimating interference using the feature detection, amplitude and phase; and

removing the estimated interference from the signal to generate a signal substantially free of power line interference.

14. The device of claim 13 further comprising, on a condition that there is high level interference in the estimate:

determine a first value (R_Fil) from a ratio of (first stage) filtered signal peak amplitude (A_Filpeak) and a root-mean-square of the amplitude (A_rms);

calculate a running histogram of the values (R_Fil) to determine a threshold value (TH_Fil);

compare the value (R_Fil) to the determined threshold value (TH_Fil); and

outputting an feature decision based on the comparison.

18. The device of claim 13 further comprising, on a condition that there is low level interference in the estimate:

determine a root-mean-square of the amplitudes of the interference harmonics (A_rms);

calculate a running histogram of the determined root-mean-square of the amplitude (A_rms) to determine a threshold value (TH_rms);

compare the root-mean-square of the amplitude (A_rms) to the determined threshold value (TH_rms); and

outputting a feature decision based on the comparison.

19. The device of claim 13 further comprising estimating the frequency of the interference, wherein the estimated frequency of the interference is utilized in the application of the comb filter.

20. The device of claim 13 further comprising estimating the frequency of the interference, wherein the estimated frequency of the interference is utilized in the estimate of the amplitude and phase.