Methods and systems for discriminating bands in scalograms

• US 8,462,321 B2
• Filed: 10/15/2012
• Issued: 06/11/2013
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennet Ireland
• Inventors: Addison, Paul Stanley, Watson, James Nicholas, Clifton, David
• Primary Examiner(s): LAUCHMAN, LAYLA G
• Application Number:
  US13/652,398
• Publication Number:
  US 20130041240A1
• Time in Patent Office: 239 Days
• Field of Search: 356/41, 600/323, 600/324, 600/309, 600/502, 702/141, 702/66, 702/119
• 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 light intensity signal indicative of light attenuated by body tissue of a subject;

performing, using a processor, a wavelet transform based at least in part on the light intensity signal;

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

identifying, using the processor, first and second candidate bands in the scalogram;

comparing, using the processor, at least one feature of the first and second bands;

identifying, using the processor and based on the comparison, one of the first and second candidate bands as a band not of interest;

discriminating, using the processor, the band not of interest; and

calculating, using a processor, a physiological parameter of the subject based at least in part on the scalogram.

2. The method of claim 1, wherein the physiological parameter is one of pulse rate and breathing rate.

3. The method of claim 1, wherein the at least one feature comprises a distribution of maximum turning points in time along a scale of the scalogram.

4. The method of claim 1, wherein comparing the at least one feature comprises:

determining a modulation frequency of the first candidate band; and

comparing the modulation frequency with a feature of the second candidate band.

5. The method of claim 1, wherein comparing the at least one feature comprises:

filtering the light intensity signal based on a first scale associated with the first candidate band to generate a first filtered signal;

filtering the light intensity signal based on a second scale associated with the second candidate band to generate a second filtered signal; and

comparing the first filtered signal and the second filtered signal.

6. The method of claim 1, wherein discriminating comprises masking the band not of interest in the scalogram.

7. The method of claim 1, wherein discriminating comprises removing the band not of interest from the scalogram.

8. The method of claim 1, wherein discriminating comprises ignoring the band not of interest in the calculation of the physiological parameter.

9. The method of claim 1, wherein identifying one of the first and second candidate bands comprises identifying one of the first and second candidate bands as a band not of interest using a first technique, the method further comprising:

identifying one of the first and second candidate bands as a band not of interest using a second technique, wherein the band not of interest is discriminated only when the first and second techniques identify the same band.

10. The method of claim 1, further comprising displaying the physiological parameter.

11. A system for calculating a physiological parameter, comprising:

a processor configured for;

receiving a light intensity signal indicative of light attenuated by body tissue of a subject;

performing a wavelet transform based at least in part on the light intensity signal;

generating a scalogram based at least in part on the wavelet transform of the light intensity signal;

identifying first and second candidate bands in the scalogram;

comparing at least one feature of the first and second bands;

identifying, based on the comparison, one of the first and second candidate bands as a band not of interest;

discriminating the band not of interest; and

calculating a physiological parameter of the subject based at least in part on the scalogram.

12. The system of claim 11, wherein the physiological parameter is one of pulse rate and breathing rate.

13. The system of claim 11, wherein the at least one feature comprises a distribution of maximum turning points in time along a scale of the scalogram.

14. The system of claim 11, wherein comparing the at least one feature comprises:

determining a modulation frequency of the first candidate band; and

comparing the modulation frequency with a feature of the second candidate band.

15. The system of claim 11, wherein comparing the at least one feature comprises:

filtering the light intensity signal based on a first scale associated with the first candidate band to generate a first filtered signal;

filtering the light intensity signal based on a second scale associated with the second candidate band to generate a second filtered signal; and

comparing the first filtered signal and the second filtered signal.

16. The system of claim 11, wherein discriminating comprises masking the band not of interest in the scalogram.

17. The system of claim 11, wherein discriminating comprises removing the band not of interest from the scalogram.

18. The system of claim 11, wherein discriminating comprises ignoring the band not of interest in the calculation of the physiological parameter.

19. The system of claim 11, wherein identifying one of the first and second candidate bands comprises identifying one of the first and second candidate bands as a band not of interest using a first technique, the processor further configured for:

identifying one of the first and second candidate bands as a band not of interest using a second technique, wherein the band not of interest is discriminated only when the first and second techniques identify the same band.

20. The system of claim 11, further comprising a display for displaying the physiological parameter.