Methods and systems for discriminating bands in scalograms

• US 8,077,297 B2
• Filed: 10/03/2008
• Issued: 12/13/2011
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James, Clifton, David
• Primary Examiner(s): Lauchman, Layla
• Application Number:
  US12/245,232
• Publication Number:
  US 20100014761A1
• Time in Patent Office: 1,166 Days
• Field of Search: 356/41, 356/42, 600/323, 600/324, 600/310, 600/508, 600/484, 600/529
• US Class Current: 356/41
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: G06F 2218/06 by applying a scale-space analysis, e.g. using wavelet analysis

Abstract

The present disclosure is directed towards embodiments of systems and methods for discriminating (e.g., masking out) scale bands that are determined to be not of interest from a scalogram derived from a continuous wavelet transform of a signal. Techniques for determining whether a scale band is not of interest include, for example, determining whether a scale band'"'"'s amplitude is being modulated by one or more other bands in the scalogram. Another technique involves determining whether a scale band is located between two other bands and has energy less than that of its neighboring bands. Another technique involves determining whether a scale band is located at about half the scale of another, more dominant (i.e., higher energy) band.

Claims

1. A method comprising:

receiving a signal using a processor;

generating a scalogram using the processor based at least in part on a continuous wavelet transform of the signal;

determining whether at least one band of scales from the scalogram is not of interest using the processor; and

discriminating the at least one band of scales if it is determined to be not of interest using the processor.

2. The method of claim 1, wherein the determining is performed at least in part by a mod-max discriminator.

3. The method of claim 1, wherein the determining comprises determining whether the at least one band'"'"'s energy amplitude is being modulated by another band.

4. The method of claim 3, wherein the determining whether the at least one band'"'"'s energy amplitude is being modulated by another band comprises:

computing a transform of the amplitude of a profile ridge candidate; and

comparing the computed transform to at least one scale value of a source ridge candidate.

5. The method of claim 3, wherein the determining whether the at least one band'"'"'s energy amplitude is being modulated by another band comprises filtering the signal at one scale of interest.

6. The method of claim 1, wherein the determining comprises determining whether the at least one band is a coupled band.

7. The method of claim 6, wherein the determining whether the at least one band is a coupled band comprises:

computing the energy of a source ridge candidate;

determining a threshold from the computed energy of the source ridge candidate;

computing the energy of a profile ridge candidate; and

comparing the computed energy of the profile ridge candidate to the threshold.

8. The method of claim 6, wherein the coupled band is located on the scalogram between a first band of interest and a second band of interest.

9. The method of claim 1, wherein the determining comprises determining whether the at least one band is a half scale band.

10. The method of claim 1, wherein the discriminating comprises masking the at least one band.

11. A system for discriminating at least one band of scales, the system comprising:

a processor capable of;

receiving an input signal;

generating a scalogram based at least in part on a continuous wavelet transform of the input signal;

determining whether at least one band of scales from the scalogram is not of interest; and

discriminating the at least one band of scales if it determined to be not of interest.

12. The system of claim 11, wherein the processor is coupled to a pulse oximeter.

13. The system of claim 12, wherein the input signal is a photoplethysmograph signal.

14. The system of claim 11, wherein the determining comprises determining whether the at least one band'"'"'s energy amplitude is being modulated by another band.

15. The system of claim 11, wherein the determining comprises determining whether the at least one band is a coupled band.

16. The system of claim 11, wherein the determining comprises determining whether the at least one band is a half scale band.

17. The system of claim 11, wherein the discriminating comprises masking the at least one band.

18. A computer-readable medium having computer program instructions stored thereon, if executed by a machine are capable of:

generating a scalogram based at least in part on a continuous wavelet transform of an input signal;

determining whether at least one band of scales from the scalogram is not of interest to a pulse rate or a breathing rate of the patient; and

discriminating the at least one band of scales if it is determined to be not of interest.

19. The computer-readable medium of claim 18, wherein the input signal comprises a photoplethysmograph signal, and the computer readable instructions are executed at least in part by a pulse oximeter.

20. The computer-readable medium of claim 18, wherein the determining comprises determining whether the at least one band'"'"'s energy amplitude is being modulated by another band.