Continuous cardiac pulse rate estimation from multi-channel source video data

• US 8,855,384 B2
• Filed: 06/20/2012
• Issued: 10/07/2014
• Est. Priority Date: 06/20/2012
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Kyal, Survi, Mestha, Lalit Keshav, Xu, Beilei
• Primary Examiner(s): SHAH, UTPAL D
• Application Number:
  US13/528,307
• Publication Number:
  US 20130343614A1
• Time in Patent Office: 839 Days
• Field of Search: 382/128
• US Class Current: 382/128
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: G06F 18/21 Design or setup of recognition systems or techniques; Extraction of features in feature space; Blind source separation
• CPC Class Codes: G06F 2218/22 Source localisation; Inverse modelling
• CPC Class Codes: G06V 2201/03 Recognition of patterns in medical or anatomical images

Abstract

What is disclosed is a computationally efficient system and method for estimating a subject'"'"'s cardiac pulse rate from multi-channel source video data. In one embodiment, A time-series signal is received. A sliding window is used to define overlapping segments of the time-series signal. Signal segments are processed by performing constrained independent component analysis (cICA) until convergence to obtain an estimated source signal. A frequency of each estimated source signal obtained by the cICA at convergence is determined to be the subject'"'"'s estimated cardiac pulse rate for each signal segment. A seed reference signal used by the cICA is repeatedly updated. A sliding window is shifted to define a next time-series signal segment for processing. The method repeats for each signal segment until a termination criteria is met. In such a manner, the subject'"'"'s cardiac pulse rate is estimated from a video of the subject on a continuous basis.

Claims

1. A method for continuous cardiac pulse rate estimation from video images captured of a subject of interest being monitored for cardiac function, the method comprising:

receiving a time-series signal of a subject of interest being monitored for cardiac function;

overlaying said received time-series signal with a sliding window, said sliding window defining segments of said received time-series signal for processing, each successive position of said sliding window defining a next segment of said time-series signal for processing;

defining a seed reference signal with a frequency range that approximates a frequency range of said subject'"'"'s cardiac pulse; and

processing segments of said received time-series signal by repeatedly;

performing constrained source separation (cICA) on said signal segment using said seed reference signal to obtain an estimated source signal, said cICA converging on an occurrence of one of;

an error between said estimated source signal and said seed reference signal being less than a threshold, and a pre-defined number of iterations having occurred;

A) in response to said error being less than said threshold;

determining a frequency of said estimated source signal as said subject'"'"'s estimated cardiac pulse rate for this time-series signal segment;

using said estimated source signal as said seed reference signal for processing a next time-series signal segment on a next iteration; and

shifting said sliding window to define a next segment of said time-series signal, said next segment at least partially overlapping a previous time-series signal segment defined by said window on a last iteration; and

B) in response to said pre-defined number of iterations having occurred, performing one of;

updating said seed reference signal by changing any of;

a frequency, an amplitude, a phase, and a waveform of said seed reference signal, and using said updated reference signal as said seed reference signal to re-process said time-series signal segment; and

selecting an estimated source signal obtained from having processed a previous time-series signal segment and using said selected estimated source signal as said seed reference signal to re-process said time-series signal segment.

2. The method of claim 1, wherein said time-series signal is received on a continuous basis and processed as said time-series signal is being received.

3. The method of claim 1, wherein said received time-series signal comprises any of:

RGB signals, IR signals, RGB and IR signals, multi-spectral signals, and hyperspectral signals.

4. The method of claim 1, wherein, in advance of using said estimated source signal as said seed reference signal, further comprising conditioning said estimated source signal to remove artifacts.

5. The method of claim 1, wherein said waveform comprises any of:

a sine wave, a square wave, a user-defined shape obtained from an ECG signal, and a cardiac pulse waveform derived from said subject.

6. The method of claim 1, wherein said time-series signal comprises one of:

stored values, and values generated from a streaming video.

7. The method of claim 1, wherein at least two of said time-series signal segments are defined by windows with a different size.

8. The method of claim 1, further comprising providing said subject'"'"'s estimated cardiac pulse rate to a display device.

9. A system for continuous cardiac pulse rate estimation from video images captured of a subject of interest being monitored for cardiac function, the system comprising:

a memory; and

a processor in communication with said memory, said processor executing machine readable instructions for performing;

receiving a time-series signal of a subject of interest being monitored for cardiac function;

overlaying said received time-series signal with a sliding window, said sliding window defining segments of said received time-series signal for processing, each successive position of said sliding window defining a next segment of said time-series signal for processing;

defining a seed reference signal with a frequency range that approximates a frequency range of said subject'"'"'s cardiac pulse; and

processing segments of said received time-series signal by repeatedly;

performing constrained source separation (cICA) on said signal segment using said seed reference signal to obtain an estimated source signal, said cICA converging on an occurrence of one of;

an error between said estimated source signal and said seed reference signal being less than a threshold, and a pre-defined number of iterations having occurred;

A) in response to said error being less than said threshold;

determining a frequency of said estimated source signal as said subject'"'"'s estimated cardiac pulse rate for this time-series signal segment;

using said estimated source signal as said seed reference signal for processing a next time-series signal segment on a next iteration; and

shifting said sliding window to define a next segment of said time-series signal, said next segment at least partially overlapping a previous time-series signal segment defined by said window on a last iteration; and

B) in response to said pre-defined number of iterations having occurred, performing one of;

updating said seed reference signal by changing any of;

a frequency, an amplitude, a phase, and a waveform of said seed reference signal, and using said updated reference signal as said seed reference signal to re-process said time-series signal segment; and

selecting an estimated source signal obtained from having processed a previous time-series signal segment and using said selected estimated source signal as said seed reference signal to re-process said time-series signal segment.

10. The system of claim 9, wherein said time-series signal is received on a continuous basis and processed as said time-series signal is being received.

11. The system of claim 9, wherein said received time-series signal comprises any of:

RGB signals, IR signals, RGB and IR signals, multi-spectral signals, and hyperspectral signals.

12. The system of claim 9, wherein, in advance of using said estimated source signal as said seed reference signal, further comprising conditioning said estimated source signal to remove artifacts.

13. The system of claim 9, wherein said waveform comprises any of:

a sine wave, a square wave, a user-defined shape obtained from an ECG signal, and a cardiac pulse waveform derived from said subject.

14. The system of claim 9, wherein at least two of said time-series signal segments are defined by windows with a different size.

15. The system of claim 9, wherein said time-series signal comprises one of:

stored values, and values generated from a streaming video.

16. The system of claim 9, further comprising providing said subject'"'"'s estimated cardiac pulse rate to a display device.

17. A non-transitory computer readable media containing machine readable program instructions for performing a method comprising:

receiving a time-series signal of a subject of interest being monitored for cardiac function;

overlaying said received time-series signal with a sliding window, said sliding window defining segments of said received time-series signal for processing, each successive position of said sliding window defining a next segment of said time-series signal for processing;

defining a seed reference signal with a frequency range that approximates a frequency range of said subject'"'"'s cardiac pulse; and

processing segments of said received time-series signal by repeatedly;

performing constrained source separation (cICA) on said signal segment using said seed reference signal to obtain an estimated source signal, said cICA converging on an occurrence of one of;

an error between said estimated source signal and said seed reference signal being less than a threshold, and a pre-defined number of iterations having occurred;

A) in response to said error being less than said threshold;

determining a frequency of said estimated source signal as said subject'"'"'s estimated cardiac pulse rate for this time-series signal segment;

using said estimated source signal as said seed reference signal for processing a next time-series signal segment on a next iteration; and

shifting said sliding window to define a next segment of said time-series signal, said next segment at least partially overlapping a previous time-series signal segment defined by said window on a last iteration; and

B) in response to said pre-defined number of iterations having occurred, performing one of;

updating said seed reference signal by changing any of;

a frequency, an amplitude, a phase, and a waveform of said seed reference signal, and using said updated reference signal as said seed reference signal to re-process said time-series signal segment; and

selecting an estimated source signal obtained from having processed a previous time-series signal segment and using said selected estimated source signal as said seed reference signal to re-process said time-series signal segment.

18. The non-transitory computer readable media of claim 17, wherein said time-series signal is received on a continuous basis and processed as said time-series signal is being received.

19. The non-transitory computer readable media of claim 17, wherein said received time-series signal comprises any of:

RGB signals, IR signals, RGB and IR signals, multi-spectral signals, and hyperspectral signals.

20. The non-transitory computer readable media of claim 17, wherein, in advance of using said estimated source signal as said seed reference signal, further comprising conditioning said estimated source signal to remove artifacts.

21. The non-transitory computer readable media of claim 17, wherein said waveform comprises any of:

a sine wave, a square wave, a user-defined shape obtained from an ECG signal, and a cardiac pulse waveform derived from said subject.

22. The non-transitory computer readable media of claim 17, wherein said time-series signal comprises one of:

stored values, and values generated from a streaming video.

23. The non-transitory computer readable media of claim 17, wherein at least two of said time-series signal segments are defined by windows with a different size.

24. The non-transitory computer readable media of claim 17, further comprising providing said subject'"'"'s estimated cardiac pulse rate to a display device.