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1

Evaluating the fetal heart rate baseline estimation algorithms by their influence on detection of clinically important patterns

Jezewski J., Horoba K., Roj D., Wrobel J., Kupka T., Matonia A.

Biocybernetics and Biomedical Engineering

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2016

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Vol. 36, no. 4

562--573

EN

A correctly estimated component of fetal heart rate signal (FHR) – so called baseline – is a precondition for proper recognition of acceleration and deceleration patterns. A number of various algorithms for estimating the FHR baseline was proposed so far. However, there is no reference standard enabling their objective evaluation, and thus no methodology of comparing the different algorithms still exists. In this paper we propose a method for evaluation of automatically determined baseline in reference to a set of experts, based on ten separate groups of signals comprising typical variability patterns observed in the fetal heart rate. As it was proposed earlier [1], the given algorithm is evaluated based on the characteristic patterns detected using the obtained baseline, instead of direct analysis of the baseline shape. For the purpose of quantitative assessment of the estimated baseline a new synthetic inconsistency coefficient was applied. The proposed methodology enabled to evaluate eleven well-known algorithms. We believe that the method will be a valuable tool for assessment of the existing algorithms, as well as for developing the new ones.

2

Early predicting a risk of preterm labour by analysis of antepartum electrohysterograhic signals

Horoba K., Jezewski J., Matonia A., Wrobel J., Czabanski R., Jezewski M.

Biocybernetics and Biomedical Engineering

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2016

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Vol. 36, no. 4

574--583

EN

This study is aimed at evaluation of the capability to indicate the preterm labour risk by analysing the features extracted from the signals of electrical uterine activity. Free access database was used with 300 signals acquired in two groups of pregnant women who delivered at term (262 cases) and preterm (38 cases). Signal features comprised classical time domain description, spectral parameters and nonlinear measures of contractile activity. Their mean values were calculated for all the contraction episodes detected in each record and their statistical significance for recognition of two groups of recordings was provided. Obtained results were related to the previous study where the same features were applied but they were determined for entire signals. Influence of electrodes location, band-pass filter settings and gestation week was investigated. The obtained results showed that a spectral parameter – the median frequency was the most promising indicator of the preterm labour risk.

3

Analysis of electrical uterine contractile activity for prediction of preterm delivery

Horoba K., Jezewski J., Matonia A., Wrobel J., Czabanski R., Jezewski M.

Journal of Medical Informatics & Technologies

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2015

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Vol. 24

199--205

EN

This study is aimed at evaluation of the capability to indicate the preterm delivery risk analysing the features extracted from signals of electrical uterine activity. Free access database was used with signals acquired in two groups of pregnant women who delivered at term and preterm. Signal features comprised classical time domain and spectral parameters of contractile activity, as well as the sample entropy. Their mean values were calculated over all contraction episodes detected in each record and their statistical significance for separating the two groups of recordings was provided. Influence of electrodes location, band-pass filter settings and gestation week was investigated. The obtained results showed that a spectral parameter – the median frequency was the most promising indicator of the preterm delivery risk.

4

A novel approach to comparison of the fetal heart rate baseline estimation algorithms

Jezewski J., Horoba K., Roj D., Wrobel J., Kupka T., Matonia A.

Journal of Medical Informatics & Technologies

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2015

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Vol. 24

231--238

EN

A number of algorithms for estimating the so called fetal heart rate baseline was proposed so far. However, there is no reference pattern enabling their objective evaluation, and thus no methodology of comparing the competing algorithms still exists. In this paper we propose a method for evaluation of automatically determined baseline in reference to a group of experts, basing on ten separate groups of signals comprising typical patterns observed in the fetal heart rate. For the purpose of quantitative assessment of the estimated baseline a new synthetic inconsistency coefficient is presented. The proposed methodology was applied to evaluate ten well-known algorithms. We believe that the method will be a valuable tool for assessment of the existing algorithms, as well as for developing new ones.

5

Smart selection of signal analysis algorithms for telecare of high-risk pregnancy

Wróbel J., Matonia A., Horoba K., Jeżewski J., Czabański R., Pawlak A., Porwik P.

Journal of Medical Informatics & Technologies

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2014

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Vol. 23

27--33

EN

Telemedical system for fetal home monitoring with smart selection of signal analysis algorithms is presented in this paper. Fetal monitoring signals are provided by a mobile instrumentation consisting of bioelectrical signal recorder and tablet PC which retrieves and processes the data as well as provides wireless data transmission based on Internet. The fetal surveillance system enables analysis, dynamic presentation and archiving of acquired signals and medical data. Novelty of the proposed approach relies on smart fitting of the algorithms for analysis of the abdominal signals in mobile instrumentation, as well as on controlling of the fetal monitoring session from the surveillance center. These actions are performed automatically through continuous analyzing of the signal quality and the reliability of the quantitative parameters determined for the acquired signals. Using that approach the amount and content of data transmitted through remote channels to the surveillance center can be controlled to ensure the most reliable assessment of the fetal well-being.

6

Automated detection of fetal movements in Doppler ultrasound signals versus maternal perception

Wróbel J., Kupka T., Horoba K., Matonia A., Roj D., Jeżewski J.

Journal of Medical Informatics & Technologies

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2014

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Vol. 23

43--50

EN

Analysis of movement activity is important since it enables detection of nonreactive fetal heart rate recordings. The aim of the study was to develop an algorithm for automated detection of the fetal movement activity (actogram), based on analysis of the Doppler ultrasound signal, and to evaluate a reliability of the actogram as a source of information about the fetal movements. Bandpass filtering (20-80 Hz) was used to separate the actogram signal describing the fetal movement activity. Simultaneously there were recorded the markers of fetal movements perceived by mother, being the reference information. For the determination of the binary actogram, the authors proposed an algorithm in which the classification threshold was estimated at the beginning of each recording and was adaptively modified during its duration. The algorithm ensured detection of up to 89% of movement episodes corresponding to movements perceived by mother. At the same time almost as high number of episodes not related to the reference information was recognized. Obtained results revealed that the automated analysis of fetal movements is characterized by much higher sensitivity of movement episode detection compared to the maternal perception.

7

Reconstruction of FHR series recorded via ultrasound - method validation using abdominal fetal electrocardiography

Kupka T., Horoba K., Roj D., Matonia A., Czabanski R., Jezewski M.

Journal of Medical Informatics & Technologies

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2013

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Vol. 22

135--141

EN

Analysis of variability of the fetal heart rate (FHR) is very important for fetal wellbeing assessment. The beat-to-beat variability is described quantitatively by the indices originated from invasive fetal electrocardiography which provides the FHR signal in a form of time event series. Nowadays, monitoring instrumentation is based on Doppler ultrasound technology. The fetal monitors provide the output signal in a form of evenly spaced measurements. The goal of this work is to present a new method for the FHR signal processing, which enables extraction of time series of consecutive heartbeat intervals from the evenly repeated values. The proposed correction algorithm enables recognition and removal of the duplicated measurements. Reliable evaluation of the algorithm requires the reference event series, thus the FHR signals were obtained from abdominal fetal electrocardiograms to be used in this research study.

8

Projective filtering based on L1-norm PC

Przybyła T., Wróbel J., Pander T., Czabański R., Jeżewski J., Matonia A.

Journal of Medical Informatics & Technologies

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2013

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Vol. 22

79--86

EN

The paper presents a modification of nonlinear state-space projections (NSSP) method. The proposed approach deals with the sub-space estimation problem. In the original NSSP method, the principal component analysis (PCA) is used for the subspace determination. The classical PCA uses L2-norm. It is well known that the L2-norm is sensitive to outliers. Thus, in this paper the L1-norm PCA is proposed a subspace determination. In numerical experiments an analytic signal and real ECG signals are processed with the proposed method. The signals are contaminated with Gaussian distributed noise with different signal to noise ratio (SNR). Obtained results confirm the usefulness of the proposed modification.

9

Comparison of instantaneous fetal heart rate extracted from abdominal and direct fetal electrocardiograms

Matonia A., Kupka T., Jezewski J., Momot A., Jeżewski M., Bernys M.

Journal of Medical Informatics & Technologies

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2012

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Vol. 19

101--107

EN

This work is an attempt to assess the reliability of indirect abdominal electrocardiography as an alternative technique of fetal monitoring. As a reference signal we used the simultaneously acquired direct fetal electrocardiogram. Each recording consisted of four signals acquired from maternal abdomen and the reference signal acquired directly from fetal head. The first stage of our study concerned the signal loss episodes. In order to reduce the influence of incorrectly detected R-waves, some certain validation rules were applied. In the second stage, the corresponding intervals determined on basis of both acquisition methods were matched and the accuracy of fetal heart rate measurement was evaluated. Although the accuracy of abdominal electrocardiography turned out to be slightly lower than reported for ultrasound method, it still has some unique features deciding of its prevalence in a certain circumstances.

10

An approach to unsupervised classification

Przybyła T., Pander T., Horoba K., Kupka T., Matonia A.

Journal of Medical Informatics & Technologies

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2011

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Vol. 17

105--111

EN

Classification methods can be divided into supervised and unsupervised methods. The supervised classifier requires a training set for the classifier parameter estimation. In the case of absence of a training set, the popular classifiers (e.g. K-Nearest Neighbors) can not be used. The clustering methods are considered as unsupervised classification methods. This paper presents an idea of the unsupervised classification with the popular classifiers. The fuzzy clustering method is used to create a learning set. The learning set includes only these patterns that are the best representative of each class in the input dataset. The numerical experiment uses an artificial dataset as well as the medical datasets (PIMA, Wisconsin Breast Cancer) and illustrates the usefulness of the proposed method.

11

Generalized fuzzy clustering method

Przybyła T., Roj D., Jeżewski J., Matonia A.

Journal of Medical Informatics & Technologies

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2010

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Vol. 16

69--76

EN

This paper presents a new hybrid fuzzy clustering method. In the proposed method, cluster prototypes are values that minimize the introduced generalized cost function. The proposed method can be considered as a generalization of fuzzy c–means (FCM) method as well as the fuzzy c–median (FCMed) clustering method. The generalization of the cluster cost function is made by applying the Lp norm. The values that minimize the proposed cost function have been chosen as the group prototypes. The weighted myriad is the special case of the group prototype, when the Lp norm is the L2 (Euclidean) norm. The cluster prototypes are the weighted meridians for the L1 norm. Artificial data set is used to demonstrate the performance of proposed method.

12

State-space averaging for maternal ECG suppression

Kotas M., Jeżewski J., Kupka T., Matonia A.

Journal of Medical Informatics & Technologies

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2009

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Vol. 13

194--200

EN

In this paper a new method of maternal electrocardiogram suppression for fetal component extraction from one-channel maternal abdominal bioelectric signals is proposed. The method performs maternal ECG estimation by application of state-space averaging. The estimated signal is subtracted from the original one and this way suppressed. The method parameters allow us to balance between the precision of maternal ECG suppression and the necessity not to attenuate the fetal QRS complexes. A small database of the maternal abdominal bioelectric signals is used to investigate the developed system for fetal heart rate determination. The final assessment is based on the detection performance index. It is shown that by proper choice of the parameters we can tune the system so that it is more effective than the classical approach based on template subtraction.

13

The prognostic value of electrohysterography in prediction of premature labour

Sikora J., Matonia A., Horoba K., Ziętek J., Jeżewski J.

Journal of Medical Informatics & Technologies

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2008

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Vol. 12

71--76

EN

Premature birth is the leading cause of a neonatal death, so, it is extremely important to distinguish the pregnancy at risk of preterm threatening labour. The electrohysterography seems very promising as a method which enables noninvasive recording of readable bioelectrical signal of uterine muscle. The developed instrumentation enabled simultaneous recording of bioelectrical signals by means of electrodes attached to abdominal wall and mechanical activity of uterine muscle using fetal monitor. Material comprised 27 patients in physiological pregnancy (27 ÷ 40 week), and 21 patients (23 ÷ 36 week) with the symptoms of threatening premature labour. The obtained results showed that quantitative parameters of detected uterine contractions: amplitude and contraction area, obtained both for mechanical and electrical activity, were statistically significant (p < 0.05) to distinguish the patients at risk of premature labour. However, their reliability is low because they strongly depend on individual patient features. We consider the parameters characteristic for electrohysterogram exclusively e.g. contraction power and its median frequency as more useful (p < 0.05). Noninvasive electrohysterography ensures higher sensitivity and specificity for recognition of uterine contraction activity in comparison to classical mechanical method.

14

The influence of window size of autocorrelation function on fetal heart rate variability measurement using the Doppler ultrasound signal

Roj D., Fuchs T., Przybyła T., Jeżewski M., Matonia A., Gacek A.

Journal of Medical Informatics & Technologies

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2008

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Vol. 12

111--116

EN

Commonly used noninvasive fetal monitoring is based on fetal heart rate (FHR) variability analysis of the Doppler ultrasound signal coming from the mechanical activity of the fetal heart. Estimation of periodicity of acquired signals using the autocorrelation technique is very important. The determination of cardiac intervals using the Doppler signal is more difficult than in electrocardiography, where the R-waves are evident. We investigated the influence of the autocorrelation window size on the FHR variability analysis. The indices describing the FHR variability calculated for signals obtained using two different autocorrelation techniques with various window lengths were compared with the reference ones obtained from fetal electrocardiogram. The optimal window was a compromise between artifacts resistance and the averaging level of instantaneous variability.

15

Telemedical system for home fetal monitoring with online analysis of bioelectricalabdominal signals

Wróbel J., Jeżewski J., Matonia A., Kupka T., Gacek A., Roj D.

Journal of Medical Informatics & Technologies

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2008

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Vol. 12

91--95

EN

This paper presents some aspects of the on-line remote fetal monitoring system based on the GPRS data transmission service and WAN network. The remote signal recording instrumentation consists of bioelectrical signal recorder and tablet PC computer. The central surveillance system located in hospital has a capability of simultaneous monitoring of up to 24 patients, both remotely and within hospital. The system enables analysis, dynamic presentation and archiving of signals and medical data. The clinical interpretation is immediately available in hospital as well as at patient's home or attending doctor office.

16

Separation of abdominal fetal electrocardiograms in twin pregnancy

Kotas M., Jeżewski J., Matonia A., Kupka T.

Journal of Medical Informatics & Technologies

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2008

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Vol. 12

83--89

EN

A combined application of independent component analysis and projective filtering of the time-aligned ECG beats is proposed to solve the problem of fetal ECG extraction from multi-channel maternal abdominal electric signals. The developed method is employed to process the four-channel abdominal signals recorded during twin pregnancy. The signals are complicated mixtures of the maternal ECG, the ECGs of the fetal twins and noise of other origin. The independent component analysis cannot separate the respective signals, but the proposed combination of the methods allows to suppress the maternal ECG and when the level of noise is low it leads to an effective separation of the twins' signals.

17

Recognition of early symptoms of fetal distress with on-line analysis of bioelectrical signals from maternal abdomen

Gacek A., Matonia A., Jeżewski J., Kupka T.

Biocybernetics and Biomedical Engineering

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2007

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Vol. 27, no. 1-2

207-216

EN

Conventional fetal monitoring for recognition of fetal distress is based on ultrasound Doppler technique. The new approach proposed in this work relies on analysis of bioelectrical signals recorded from the maternal abdominal wall. Fetal electrocardiogram and uterine electrical signal are extracted from abdominal signals using advanced instrumentation and algorithms for signal processing. Evaluation of the fetal heart rate variability with an additional analysis of fetal electrocardiogram morphology is expected to ensure early detection of fetal hypoxia symptoms and, finally, an appropriate obstetrical intervention.

18

Telemetryczny nadzór przebiegu ciąży z adaptacyjnym doborem zakresu interpretacji przenośnego monitora

Bożewicz D., Wróbel J., Jeżewski J., Matonia A., Pałko T., Gacek A., Kupka T., Horoba K.

Prace Naukowe Politechniki Warszawskiej. Elektronika

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2006

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z. 157

117-122

EN

The system was designed for medical investigation beyond hospital unit. It can be applied in all places which are within the range of mobile phone network area. It shows the signal acquired from the cardiotocograph on the patient device screen and send all received data to the Clinical Surveillance Center (CSC). The data in CSC are analysed and presented on the medical doctor PC display. This system give possibility of permanent woman monitoring without hospitalisation. If medical doctor notes something suspicious, he can remotely take decision about medical intervention. Presented system of data acquisition and teletransmission fulfils the last standards of medicine, which expect more quickly exploration, better patient comfort and make communication with a medical doctor much easier.

19

Monitoring of contraction activity of uterine muscle by the use of abdominal electrohysterography

Matonia A., Horoba K., Jeżewski J., Kupka T.

Acta of Bioengineering and Biomechanics

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2006

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Vol. 8, no. 2

27-34

EN

Monitoring of contraction activity of uterine muscle is important diagnostic tool used both during pregnancy and labour. The strain of pregnant uterus exerted on maternal abdomen is measured via external tocography. However, limitation of this approach has caused a development of other technique – electrohysterography, which is based on recording an electrical uterine activity. The comparison between electrohysterography and tocography was made due to the possibility of the simultaneous recording of mechanical and electrical uterine muscle activity. The results obtained show that both methods demonstrate high agreement in relation to the number of contractions recognized as being consistent.

20

Neonatal surveillance system based on data stream technology

Widera M., Matonia A., Wróbel J., Jeżewski J., Horoba K., Kupka T.

Journal of Medical Informatics & Technologies

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2005

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Vol. 9

93--98

EN

Pulse oximetry is a non-invasive measurement method of an arterial blood oxygen saturation. Pulse oximeter is one of the main bedside monitors used in neonatal units. The dispersed location of medical devices in such unit renders impossible to make a fast and valid decision in the case of simultaneous alarming situation. This paper present hardware and software structure of centralised neonatal monitoring system. Presented system can work as a single central station for monitoring of up to twenty four patients. Application of central monitoring system decreases the risk of undetected patients live and health threats. Thanks to this system the medical stuff is less burdened by routine procedures; therefore the medical unit is perceived as child- and mother-friendly.