Efficient fetal-maternal ECG signal separation from two maternal abdominal leads via diffusion-based channel selection

Patent metadata

Field	Value
Publication number	US-11622710-B2
Application number	US-201816490320-A
Country	US
Kind code	B2
Filing date	Mar 1, 2018
Priority date	Mar 1, 2017
Publication date	Apr 11, 2023
Grant date	Apr 11, 2023

Abstract

In some embodiments, techniques capable of obtaining high-quality fetal ECG (fECG) information using as few as two composite (maternal and fetal) maternal abdominal ECG (aECG) signals to derive the fetal ECG information are provided. In some embodiments, maternal ECG information and fetal ECG information are both obtained from the aECG signals, and are either presented or stored. The techniques may use novel proposed diffusion-based channel selection criteria. To validate the proposed techniques, analysis results of two publicly available databases are described, and compared with other available techniques in the literature.

First claim

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A system for non-invasive measurement of heartbeat characteristics, the system comprising:
a set of maternal abdominal leads, including a first maternal abdominal lead and a second maternal abdominal lead; and
an abdominal electrocardiogram (aECG) device communicatively coupled to the maternal abdominal leads, comprising at least one processor and a non-transitory computer-readable medium, wherein the non-transitory computer-readable medium has instructions stored thereon that, in response to execution by the at least one processor, cause the aECG device to measure heartbeat characteristics by:
creating a set of linear combinations using signals from the set of maternal abdominal leads, wherein each linear combination includes a pair of selected leads from the set of maternal abdominal leads and a θ value usable to linearly combine signals from the pair of selected leads;
determining a set of rough fECGs based on the set of linear combinations;
selecting a channel based on the set of rough fECGs, wherein the channel includes the pair of selected leads and the θ value of a linear combination; and
measuring the heartbeat characteristics using the selected channel.

2. The system of claim 1 , wherein the heartbeat characteristics are fetal R peaks or a fetal heart rate.

3. The system of claim 1 , wherein the instructions further cause the aECG device to preprocess the signals from the set of maternal abdominal leads by performing at least one of applying a low pass filter, applying one or more notch filters to suppress power line interference, and subtracting an estimated trend.

4. The system of claim 1 , wherein creating the set of linear combinations includes:
determining a set of θ values; and
for each θ value of the set of θ values, create a linear combination z θ as:
z θ =θx +√{square root over (1−θ 2 )} y

wherein x is a time series representing a signal of the first maternal abdominal lead, and y is a time series representing a signal of the second maternal abdominal lead.

5. The system of claim 1 , wherein the set of maternal abdominal leads further includes at least a third abdominal lead, and wherein creating the set of linear combinations includes:
determining a pair of leads from the set of maternal abdominal leads;
determining a set of θ values; and
for each θ value of the set of θ values, create a linear combination z θ as:
z θ =θx +√{square root over (1−θ 2 )} y

wherein x is a time series representing a signal of a first lead of the pair of leads, and y is a time series representing a signal of a second lead of the pair of leads.

6. The system of claim 5 , wherein creating the set of linear combinations further includes:
determining a new pair of leads from the set of maternal abdominal leads;
creating a linear combination for the new pair of leads for each θ value of the set of θ values; and
repeating the actions of determining a new pair of leads and creating a linear combination for the new pair of leads for each θ value of the set of θ values for each pairwise combination of leads in the set of maternal abdominal leads.

7. The system of claim 1 , wherein determining a set of rough fECGs includes, for each linear combination of the set of linear combinations:
estimating a maternal ECG based on the linear combination; and
subtracting the estimated maternal ECG from the linear combination.

8. The system of claim 7 , wherein estimating a maternal ECG based on the linear combination includes at least one of storing the maternal ECG in an ECG data store and presenting the maternal ECG on a display device.

9. The system of claim 7 , wherein estimating a maternal ECG based on the linear combination includes:
applying a de-shape short time Fourier transform (dsSTFT) to the linear combination and extracting the dominant curve to obtain an estimated maternal instantaneous heart rate (IHR);
determining a polarity of the linear combination and multiplying the linear combination by −1 if the determined polarity is negative to create a polarity-corrected linear combination;
computing locations of maternal R-peaks using the estimated maternal IHR and the polarity-corrected linear combination;
adjusting the computed locations of the maternal R-peaks by searching for a maximum in the polarity-corrected linear combination around each computed location; and
applying the nonlocal median to estimate the maternal ECG in the linear combination based on the adjusted maternal R-peak locations.

10. The system of claim 1 , wherein selecting a channel includes:
determining a signal quality index (SQI) for each rough fECG of the set of rough fECGs; and
selecting a channel associated with a rough fECG having a highest SQI.

11. The system of claim 10 , wherein the SQI is determined by:
applying an L-step lag map to the rough fECG to create an embedded point cloud χ θ,f ,
applying a 1-normalization diffusion map to χ θ,f , and
determining the SQI S θ as:

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wherein ϕ θ,1 is a first nontrivial eigenvector of a corresponding graph Laplacian;
wherein |{circumflex over (ϕ)} θ,1 | 2 is a power spectrum of ϕ θ,1 ;
wherein ξ θ,1 , ξ θ,2 , . . . , ξ θ,n cs >0, where n cs ∈ is a number of peaks chosen by a user to be frequencies associated with highest n cs peaks in |{circumflex over (ϕ)} θ,1 | 2 ;
wherein L cs >0; and
wherein θ :=U j=1 n CS [ξ θ,i −L CS , ξ 74 ,i +L CS ].

12. A non-transitory computer-readable medium, whe

Assignees

• Univ Washington
• Governing Council Univ Toronto

Inventors

• Frasch Martin G
• Wu Hau-Tieng

Classifications

• A61B5/7278 Primary

  Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals · CPC title

• A61B5/7257

  using Fourier transforms · CPC title

• A61B5/352

  Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval · CPC title

• A61B5/344 Primary

  Foetal cardiography · CPC title

• A61B5/271

  Arrangements of electrodes with cords, cables or leads, e.g. single leads or patient cord assemblies · CPC title