Method and system for detection of cardiac sounds

• US 9,226,726 B1
• Filed: 11/25/2014
• Issued: 01/05/2016
• Est. Priority Date: 11/25/2014
• Status: Active Grant

• Current Assignee: John L. Semmlow
• Original Assignee: John L. Semmlow
• Inventors: Semmlow, John L
• Primary Examiner(s): Stice, Paula J
• Application Number:
  US14/552,842
• Time in Patent Office: 406 Days
• Field of Search: 600/528
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0204 Acoustic sensors
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 7/026 comprising more than one sound collector
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

The present invention is a method and system for detection of high-frequency heart sounds for diagnosing heart diseases. One embodiment utilizes an accelerometer-based detector that presents a light load to the chest, is sensitive to the desired high frequency range, and provides a quantitative measurement of the quality of the acquired signal. Two thin piezoelectric flexible sensors, supported by a lightweight mechanical structure, are center-loaded so that they respond to the same mechanical energy and will produce identical electrical signals in the absence of noise. A signal processing system compares the signals from the two sensors to produce an estimate of the signal-to-noise ratio. The two signals can be combined to further improve the signal-to-noise ratio. The invention is designed to be light weight, to have a sensitive sensor mechanism, to provide an estimate of the signal-to-noise ratio of the detected signal, and to be relatively immune to noise.

Claims

1. A computer implemented system for determining cardiac acoustic signal quality, the system comprising:

a cardiac acoustic signal detector connected to an amplifier;

an analog-to-digital converter connected to said amplifier;

a computing device connected to said analog to digital converter;

and

computer executable instructions operative on said computing device configured to;

perform a correlation function to calculate a maximum correlation between said cardiac acoustic signals;

convert said maximum correlation to a signal-to-noise ratio for said cardiac acoustic signals;

delivering a quantitative measurement of said signal-to-noise ratio to an output device;

wherein the output device includes a user interface for visual representation of the quality of said cardiac acoustic signals;

wherein said quality of said cardiac acoustic signal can be accurately verified.

2. The system of claim 1, further comprising normalizing said maximum correlation using a Pearson normalization.

3. The system of claim 1, wherein converting said maximum correlation comprises using a lookup table to convert said maximum correlation to said signal-to-noise ratio.

4. The system of claim 1, wherein said signal-to-noise ratio is measured in decibels.

5. The system of claim 1, further comprising initially band-limiting said cardiac acoustic signals using a filter bank tuned to appropriate frequencies such that the signal-to-noise ratio is determined as a function of signal frequency.

6. The system of claim 5 further comprising displaying graphically at a user interface said signal-to-noise ratio as a function of frequency.

7. The system of claim 1, wherein determining said maximum correlation comprises applying a cross-correlation function to said cardiac acoustic signals.

8. The system of claim 1, further including combining said cardiac acoustic signals to produce an improved signal-to-noise ratio in a resultant combined signal.

9. The system of claim 1, wherein said cardiac acoustic signal detector comprises a cardiac accelerometer detector.

10. A computer implemented method for determining cardiac acoustic signal quality, the method comprising:

amplifying at least two cardiac acoustic signals received from a cardiac acoustic signal detector;

performing an analog-to-digital conversion on said cardiac acoustic signals;

receiving said cardiac acoustic signals at a computing device;

wherein the computing device performs a correlation function to calculate a maximum correlation between said cardiac acoustic signals;

convert said maximum correlation to a signal-to-noise ratio for said cardiac acoustic signals;

deliver a quantitative measurement of said signal-to-noise ratio to an output device;

wherein the output device includes a user interface for visual representation of the quality of said cardiac acoustic signals;

wherein said quality of said cardiac acoustic signal can be accurately verified.

11. The method of claim 10, further comprising normalizing said maximum correlation using a Pearson normalization.

12. The method of claim 10, wherein converting said maximum correlation comprises using a lookup table to convert said maximum correlation to said signal-to-noise ratio.

13. The method of claim 10, wherein said signal-to-noise ratio is measured in decibels.

14. The method of claim 10, further comprising initially band-limiting said cardiac acoustic signals using a filter bank tuned to appropriate frequencies such that the signal-to-noise ratio is determined as a function of signal frequency.

15. The method of claim 14, further comprising displaying graphically at a user interface said signal-to-noise ratio as a function of signal frequency.

16. The method of claim 10, wherein determining said maximum correlation comprises applying a cross-correlation function to said cardiac acoustic signals.

17. The method of claim 10, further including combining said cardiac acoustic signals to produce an improved signal-to-noise ratio in a resultant combined signal.

18. The method of claim 10, wherein said cardiac acoustic signal detector comprises a cardiac accelerometer detector.