Methods and systems for discriminating bands in scalograms

• US 8,289,501 B2
• Filed: 11/09/2011
• Issued: 10/16/2012
• 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:
  US13/292,524
• Publication Number:
  US 20120123689A1
• Time in Patent Office: 342 Days
• Field of Search: 356/41, 356/39, 356/40, 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:

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

determining whether a first band of scales in the scalogram is negatively affected by a second band of scales; and

extracting the first band of scales in response to determining that the first band is negatively affected by the second band.

2. The method of claim 1 further comprising:

identifying the first band of scales from the scalogram; and

in response to determining that the first band of scales is negatively affected by the second band of scales, identifying a third band of scales from the scalogram.

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

4. The method of claim 1, wherein the first band of scales is negatively affected by the second band of scales when the first band'"'"'s energy amplitude is modulated by the second band.

5. The method of claim 1, wherein the determining further comprises:

computing energy of a source ridge candidate;

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

computing energy of a profile ridge candidate; and

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

6. The method of claim 1, wherein the signal is a photoplethysmograph signal.

7. The method of claim 1, wherein the extracting removes the first band of scales from the scalogram.

8. The method of claim 1 further comprising replacing the first band of scales with energy bands of constant amplitude.

9. The method of claim 1 further comprising replacing the first band of scales with energy bands derived dynamically according at least in part to features of the scalogram.

10. A system comprising control circuitry configured to:

generate a scalogram based at least in part on a continuous wavelet transform of a signal;

determine whether a first band of scales in the scalogram is negatively affected by a second band of scales; and

extract the first band of scales in response to determining that the first band is negatively affected by the second band.

11. The system of claim 10, wherein the control circuitry is further configured to:

identify the first band of scales from the scalogram; and

in response to determining that the first band of scales is negatively affected by the second band of scales, identify a third band of scales from the scalogram.

12. The system of claim 10, wherein the determining is performed at least in part by a mod-max discriminator.

13. The system of claim 10, wherein the first band of scales is negatively affected by the second band of scales when the first band'"'"'s energy amplitude is modulated by the second band.

14. The system of claim 10, wherein the control circuitry is further configured to:

compute energy of a source ridge candidate;

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

compute energy of a profile ridge candidate; and

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

15. The system of claim 10, wherein the signal is a photoplethysmograph signal.

16. The system of claim 10, wherein the control circuitry is further configured to remove the first band of scales from the scalogram.

17. The system of claim 10, wherein the control circuitry is further configured to replace the first band of scales with energy bands of constant amplitude.

18. The system of claim 10, wherein the control circuitry is further configured to replace the first band of scales with energy bands derived dynamically according at least in part to features of the scalogram.

19. A non-transitory 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 a signal;

determining whether a first band of scales in the scalogram is negatively affected by a second band of scales; and

extracting the first band of scales in response to determining that the first band is negatively affected by the second band.

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