Apparatus for monitoring fetal heart-beat
First Claim
1. Apparatus for the detection of a fetal electrocardiogram (fECG), the apparatus (30, 44, 48) comprising:
- a plurality of low-noise electrodes (1-3, R) for external skin (40) placement during pregnancy, each electrode (1-3, R) being connectable to low-noise signal recording and processing means (34, 36, 46, 47) wherein, when in use, the signal recording and processing means (34, 36, 46, 47) is arranged;
to record signals indicative of voltages developed between pairs of electrodes (1-3, R) in a plurality of signal channels (60);
to process digitised data within the plurality of signal channels (60) in order to generate at least one source signal (3.4, 0.2) which relates to the fECG of a single fetus; and
on identification of the at least one source signal (3.4, 0.2) relating to the single-fetus fECG, to reconstruct, for at least one signal channel, that component of the digitised data within the channel which is attributable to that fetus, and therefore corresponds to a single-channel fECG.
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Accused Products
Abstract
Apparatus for monitoring a fetal heart-beat is able to extract one or more fetal electrocardiograms (fECGs) from a composite signal detected at the abdomen of a pregnant woman. The apparatus includes specific low-noise components; a plurality of low-noise electrodes (1-3, R) for placement on the abdomen during pregnancy and a low-noise signal recording and processing means (34). Screened leads are also used, as required. Signals indicative of voltages developed between each abdominal electrode (1-3) and a reference electrode (R) are recorded in a plurality of signal channels. Data within each channel is digitized and processed in order to generate a plurality of separated source signals, at least one of which relates to the fECG of a single fetus. Single-channel fECGs may be reconstructed using the source signals identified as belonging to the same fetus.
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Citations
27 Claims
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1. Apparatus for the detection of a fetal electrocardiogram (fECG), the apparatus (30, 44, 48) comprising:
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a plurality of low-noise electrodes (1-3, R) for external skin (40) placement during pregnancy, each electrode (1-3, R) being connectable to low-noise signal recording and processing means (34, 36, 46, 47) wherein, when in use, the signal recording and processing means (34, 36, 46, 47) is arranged;
to record signals indicative of voltages developed between pairs of electrodes (1-3, R) in a plurality of signal channels (60);
to process digitised data within the plurality of signal channels (60) in order to generate at least one source signal (3.4, 0.2) which relates to the fECG of a single fetus; and
on identification of the at least one source signal (3.4, 0.2) relating to the single-fetus fECG, to reconstruct, for at least one signal channel, that component of the digitised data within the channel which is attributable to that fetus, and therefore corresponds to a single-channel fECG. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of recording a fetal electrocardiogram (fECG) comprising the steps of:
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(a) Attaching a plurality of abdominal electrodes (1-3) to skin (40) in an abdominal area during pregnancy;
(b) Attaching a common reference electrode (R) to the skin;
(c) Measuring skin impedance at each electrode (1-3, R) and, if the skin impedance is greater than 5 kΩ
, reattaching that electrode;
(d) observing electrical skin potentials developed between each abdominal electrode (1-3) and the reference electrode (R) through a plurality of signal channels (60);
(e) if the noise on any raw data composite signal channel is greater than 10 μ
V, reducing environmental noise contributory factors, including that due to muscle noise;
(f) collecting electrical skin potentials through the plurality of signal channels (60);
(g) processing data within the plurality of signal channels (60) to generate a plurality of separated source signals (62);
(h) identifying within the plurality of source signals (62) those (3.4, 0.2) which relate to the fECG of one among one or more fetuses; and
(i) reconstructing, for at least one of the plurality of signal channels (60) respective components of the data within that channel which are attributable to each of the one or more fetuses, thereby generating a single-channel fECG for each individual fetus. - View Dependent Claims (21, 22, 23)
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24. A computer system (36) configured to extract one or more fetal electrocardiograms from composite signals detected at electrodes (R, 1-3) distributed over a pregnant woman'"'"'s abdomen, the system comprising:
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filtering means for filtering digitised composite signals, each signal corresponding to a difference between a voltage developed at a signal electrode (1-3) and that developed at a reference electrode (R), in order to remove unwanted frequency components;
processing means arranged to generate a plurality of separated source signals (62) from the corresponding plurality of filtered composite signals, wherein each composite data signal is assumed to be a linear mixture of the unknown source signals (X=SM);
selection means (64) for identifying those source signal(s) (3.4, 0.2) which correspond to a single-fetus ECG;
reconstruction means arranged, for each single-fetus ECG identified, to reconstruct, for at least one signal channel, that component of the filtered composite signal within the channel which is attributable to that fetus and therefore corresponds to a single-channel fECG; and
display means arranged to display each fECG.
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25. A computer-readable medium embodying instructions for execution by a processor, the instructions relating to the extraction of one or more fetal electrocardiograms from composite signals detected at electrodes (R, 1-3) distributed over a pregnant woman'"'"'s abdomen, wherein the computer-readable medium comprises:
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program code for filtering multi-channel digitised composite signals, each signal corresponding to a difference between a voltage developed at a signal electrode (1-3) and that developed at a reference electrode (R), in order to remove unwanted frequency components;
program code for generating a plurality of separated source signals (62) from the corresponding plurality of filtered composite signals, wherein each composite data signal is assumed to be a linear mixture of the unknown source signals (X=SM);
program code for identifying, either automatically or by prompting for a program code for generating a plurality of separated source signals (62) from the corresponding plurality of filtered composite signals, wherein each composite data signal is assumed to be a linear mixture of the unknown source signals (X=SM;
program code for identifying, either automatically or by prompting for a user input, those source signal(s) (3.4, 0.2) which correspond to a single-fetus ECG;
program code for reconstructing, for each single-fetus ECG identified, and for at least one signal channel, that component of the filtered composite signal within the channel which is attributable to that fetus and therefore corresponds to a single-channel fECG; and
program code for displaying at least one reconstructed fECG to a user.
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26. Apparatus for the detection of a fetal electrocardiogram (fECG), the apparatus (30, 44, 48) comprising:
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(a) a plurality of low-noise electrodes (1-3, R) for abdominal skin placement during pregnancy, the electrodes (1-3, R) having associated leads with screening to reduce noise level and being in number sufficient to enable at least eight signal sources to be monitored; and
(b) low-noise signal processing apparatus (34, 36, 46, 47) connectable to the electrodes and of sufficient sensitivity to detect signals of magnitude comparable with electroencephalography signals, the signal processing apparatus (34, 36, 46, 47) being for;
i. detecting signals developed by the electrodes; and
ii. processing electrode signals to obtain data and using a Blind Source Separation technique to process the data and distinguish independent sources and thereby to derive at least one source signal (3.4, 0.2) which relates to a single fetus fECG.
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27. A method of recording a fetal electrocardiogram (fECG) comprising the steps of:
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(a) during pregnancy, attaching a plurality of low-noise electrodes (1-3) to a patient'"'"'s skin (40) providing coverage from one side of the patient'"'"'s abdomen to the other and from pubic hairline to upper limit of uterus, the electrodes (1-3, R) having associated leads with screening to reduce noise level and being in number sufficient to enable at least eight signal sources to be monitored;
(b) reattaching any and all electrodes which do not meet a predetermined skin impedance criterion;
(c) if noise associated with any electrode does not meet a predetermined noise criterion, reducing at least one of electrical interference, magnetic pickup and patient muscle noise until the noise criterion is met;
(d) detecting signals developed by the electrodes and processing such signals to obtain data using low-noise signal processing apparatus (34, 36, 46, 47) of sufficient sensitivity to detect signals of magnitude comparable with electroencephalography signals; and
(e) processing the data with a Blind Source Separation technique to distinguish independent sources and thereby to derive at least one source signal (3.4, 0.2) relating to a single fetus fECG.
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Specification