EXTRACTION OF FETAL CARDIAC SIGNALS

• US 20100137727A1
• Filed: 11/23/2009
• Published: 06/03/2010
• Est. Priority Date: 11/21/2008
• Status: Active Grant

• Current Assignee: Institut Polytechnique De Grenoble, Massachusetts Institute of Technology, Universite Joseph Fourier
• Original Assignee: Institut Polytechnique De Grenoble, Massachusetts Institute of Technology, Universite Joseph Fourier
• Inventors: Clifford, Gari D., Sameni, Reza, Jutten, Christian, Shamsollahi, Mohammad B.
• Granted Patent: US 8,805,485 B2
• Time in Patent Office: Days
• US Class Current: 600/511
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/344 Foetal cardiography
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/4362 Assessing foetal parameters
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence

Abstract

A method for processing cardiac signals includes accepting, from a sensor system, a set of one or more signals, the signals including components of a desired cardiac signal and components of a substantially periodic interfering signal. The method is applicable for extraction of desired fetal cardiac signals from signals with interference from the maternal cardiac signal. A periodicity of the interfering signal is determined, and one or more iterations of mitigating an effect of a component of the signals that exhibit periodicity at the determined periodicity of the interfering signal are performed. In some examples, the method further includes determining a periodicity of the desired cardiac signal, and performing one or more iterations of enhancing an effect of a component of the signals that exhibit periodicity at the determined periodicity of the desired cardiac signal.

Claims

1. A method for processing signals comprising:

accepting, from a sensor system, a set of one or more signals, the signals including components of a desired signal and components of a interfering signal having a periodicity;

determining, by a processing engine, the periodicity of the interfering signal; and

performing, by the processing engine, one or more iterations of mitigating an effect of a component of the signals that exhibits periodicity at the determined periodicity of the interfering signal to form a processed signal.

2. The method of claim 1 further comprising:

providing, to a display system, the processed signal.

3. The method of claim 1 wherein the interfering signal includes at least one of a substantially periodic and a pseudo periodic signal.

4. The method of claim 1 wherein determining the periodicity of the interfering signal includes determining a time varying period of said signal.

5. The method of claim 1 further comprising:

determining a periodicity of the desired signal; and

performing one or more iterations of enhancing an effect of a component of the signals that exhibits periodicity at the determined periodicity of the desired signal.

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

7. The method of claim 6 wherein the interfering signal comprises a second cardiac signal.

8. The method of claim 7, wherein the periodicity of the interfering signal comprises a quantity characterizing a heartbeat period of the second cardiac signal.

9. The method of claim 8 wherein the quantity characterizing the heartbeat period of the second cardiac signal comprises an estimated R-R interval.

10. The method of claim 6 wherein the desired cardiac signal comprises a fetal cardiac signal and wherein the interfering signal comprises a maternal cardiac signal.

11. The method of claim 6, wherein the desired cardiac signal comprises a cardiac signal of a first fetus and the interfering signal comprises a cardiac signal of a second fetus.

12. The method of claim 11, wherein the interfering signal further comprises a maternal cardiac signal.

13. The method of claim 1 wherein mitigating the effect of a component of the signals that exhibit periodicity at the determined periodicity of the interfering signal includes:

identifying a relative contribution of the component of the signals that exhibit periodicity at the determined periodicity; and

processing the signals according to the identified relative contribution.

14. The method of claim 13 wherein identifying the relative contribution of the component of the signals that exhibit periodicity at the determined periodicity includes computing a generalized eigenvalue based on correlation of the signals at the determined periodicity of the interfering signal.

15. The method of claim 13 wherein processing the signals according to the identified relative contribution includes applying a Bayesian filtering approach.

16. A cardiac monitoring system comprising:

an input subsystem for accepting signals, the signals including components of a desired signal and components of an interfering signal having a periodicity;

a data processing system for processing the accepted signals, the data processing system being configured to perform the steps of;

determining the periodicity of the interfering signal, and

performing one or more iterations of mitigating an effect of a component of the signals that exhibits periodicity at the determined periodicity of the interfering signal; and

a data output subsystem for providing information determined from the processed signals.

17. The cardiac monitoring system of claim 16, wherein the desired signal is a cardiac signal.

18. Software embodied on a computer-readable medium comprising instructions for causing a data processing system to

accept a set of one or more signals, the signals including components of a desired signal and components of a interfering signal having a periodicity;

determine the periodicity of the interfering signal; and

perform one or more iterations of mitigating an effect of a component of the signals that exhibits periodicity at the determined periodicity of the interfering signal.

19. A method for processing a input signal that includes a pseudo-periodic signal present with another signal, the method comprising:

accepting the input signal, the input signal being representable as a vector signal in a multidimensional vector space;

forming a phase signal representing a time-varying periodicity of the pseudo-periodic signal;

identifying a subspace of the vector space that exhibits correlation at the time-varying periodicity;

forming a component of the input signal according to the identified subspace; and

processing the input signal to either enhance or to mitigate and effect of the formed component to produce a processed signal.

20. The method of claim 19 wherein accepting the input signal comprises accepting a biosignal, the pseudo-periodic signal having a periodicity related a periodic biological process.

21. The method of claim 20 wherein the biosignal comprises signal acquired by sensing a signal from a human body, and wherein the periodic biological process comprises a cardiac process.

22. The method of claim 19 further comprising presenting the processed signal on a display.

23. The method of claim 19 wherein

forming the phase representation includes identifying repetitions of a signal characteristic in the input signal;

identifying the subspace includes determining a generalized eigenspace from a correlation of the input signal at a time varying lag determined from the phase representation and from a correlation of the input signal at zero lag;

forming the component of the input signal according to the identified subspace includes projecting the input signal onto the eigenspace; and

processing the input signal to either enhance or to mitigate and effect of the formed component to produce a processed signal includes at least one of adding or subtracting the projection of the signal onto the eigenspace.