Using a continuous wavelet transform to generate a reference signal

• US 9,066,691 B2
• Filed: 10/03/2008
• Issued: 06/30/2015
• Est. Priority Date: 07/15/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Primary Examiner(s): Senfi, Behrooz
• Assistant Examiner(s): Jebari, Mohammed
• Application Number:
  US12/245,425
• Publication Number:
  US 20100016696A1
• Time in Patent Office: 2,461 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

According to embodiments, systems and methods for generating reference signals are provided. A signal may be transformed using a continuous wavelet transform. Regions of interest may be selected from a transform or the resulting scalogram that may be used to generate a reference signal to use in filtering the signal or other signals. Cross-correlation techniques may be used to cancel noise components or isolate non-noise components from the signal. A physiological parameter may then be determined from the filtered signal or isolated components in the signal.

Claims

1. A method for generating a noise reference signal, the method comprising:

receiving a first input signal;

receiving a second input signal, wherein the second input signal is different from the first input signal;

performing, using processing equipment, a continuous wavelet transform of the first input signal to produce a first transformed input signal;

performing, using processing equipment, a continuous wavelet transform of the second input signal to produce a second transformed input signal;

generating, using processing equipment, a first scalogram from the first transformed input signal;

generating, using processing equipment, a second scalogram from the second transformed input signal, wherein the first scalogram is generated based at least in part on the second scalogram;

identifying, using processing equipment, regions in the first scalogram that exceed a predetermined threshold; and

performing, using processing equipment, an inverse continuous wavelet transform on at least part of the first transformed input signal, based at least in part on the identified regions, to generate the noise reference signal.

2. The method of claim 1, wherein identifying regions in the first scalogram comprises identifying, using processing equipment, at least one noise component in the first scalogram.

3. The method of claim 1, wherein identifying regions in the first scalogram comprises identifying, using processing equipment, at least one non-noise component in the first scalogram.

4. The method of claim 1, wherein the first input signal comprises a photoplethysmograph (PPG) signal.

5. The method of claim 1 further comprising outputting, using processing equipment, the noise reference signal to an adaptive filter.

6. The method of claim 5 further comprising filtering, using processing equipment, the first input signal using at least the adaptive filter and the noise reference signal to produce a filtered input signal.

7. The method of claim 6 wherein filtering the first input signal comprises cross correlating, using processing equipment, the noise reference signal with the first input signal.

8. The method of claim 6 further comprising determining, using processing equipment, a physiological parameter based at least in part on the filtered input signal.

9. The method of claim 1 further comprising processing, using processing equipment, the received first input signal together with the noise reference signal.

10. The method of claim 1 further comprising extracting, using processing equipment, the identified regions from the first scalogram, wherein the noise reference signal is generated from the extracted identified regions.

11. The method of claim 1, wherein the predetermined threshold is adjusted dynamically.

12. The method of claim 11, wherein the predetermined threshold is adjusted dynamically based at least in part on the first scalogram.

13. A system for generating a noise reference signal, comprising:

an input capable of receiving a first input signal and a second input signal, wherein the second input signal is different from the first input signal; and

a processor capable of;

performing a continuous wavelet transform of the first input signal to produce a first transformed input signal;

performing a continuous wavelet transform of the second input signal to produce a second transformed input signal;

generating a first scalogram from the first transformed input signal;

generating a second scalogram from the second transformed input signal, wherein the first scalogram is generated based at least in part on the second scalogram;

identifying regions in the first scalogram that exceed a predetermined threshold; and

performing an inverse continuous wavelet transform on at least part of the first transformed input signal, based at least in part on the identified regions, to generate the noise reference signal.

14. The system of claim 13, wherein the processor is capable of identifying at least one noise component in the first scalogram.

15. The system of claim 13, wherein the processor is capable of identifying at least one non-noise component in the first scalogram.

16. The system of claim 13, wherein the first input signal comprises a photoplethysmograph (PPG) signal.

17. The system of claim 13 wherein the processor is capable of outputting the noise reference signal to an adaptive filter.

18. The system of claim 17 wherein the processor is capable of filtering the first input signal using at least the adaptive filter and/or the noise reference signal to produce a filtered input signal.

19. The system of claim 18 wherein the processor is capable of cross correlating the noise reference signal with the first input signal.

20. The system of claim 18 wherein the processor is capable of determining a physiological parameter based at least in part on the filtered input signal.

21. The system of claim 13, wherein the processor is capable of processing the received first input signal together with the noise reference signal.

22. The system of claim 13, wherein the processor is capable of:

extracting the identified regions from the first scalogram; and

generating the noise reference signal from the extracted identified regions.

23. The system of claim 13, wherein the predetermined threshold is adjusted dynamically.

24. The system of claim 23, wherein the predetermined threshold is adjusted dynamically based at least in part on the first scalogram.