Statistical shape analysis of gravid uteri throughout pregnancy by a ray description technique.

In order to study the anatomical variability of the uterus induced by pregnancy, a parametrization of gravid uterine geometry based on principal component analysis (PCA) is proposed. Corresponding meshes used for PCA are created by a ray description technique applied to a reference mesh. A smoothed voxel-based methodology is applied to determine the reference mesh from a database of 11 real shapes produced by the FEMONUM project.

Performance comparison of coupling-evaluation methods in discriminating between pregnancy and labor EHG signals.

Background: Recent years have seen an increased interest in electrohysterogram (EHG) signals as a means to evaluate the synchronization of uterine contractions. Several studies have pointed out that the quality of signal processing - and hence the interpretation of measurement results - is affected significantly by the choice of measurement technique and the presence of non-stationary frequency content in EHG signals. To our knowledge, the effect of time variance on the quality of EHG signal processing has never been fully investigated.

An Automatic Method for the Segmentation and Classification of Imminent Labor Contraction From Electrohysterograms.

Objective: Preterm birth is the first cause of perinatal morbidity and mortality. Despite continuous clinical routine improvements, the preterm rate remains steady. Moreover, the specificity of the early diagnosis stays poor as many hospitalized women for preterm delivery threat finally deliver at term.

Multi-scale and multi-physics model of the uterine smooth muscle with mechanotransduction.

Preterm labor is an important public health problem. However, the efficiency of the uterine muscle during labor is complex and still poorly understood. This work is a first step towards a model of the uterine muscle, including its electrical and mechanical components, to reach a better understanding of the uterus synchronization.

Variation-based sparse source imaging in localizing uterine activity.

Electrohysterogram source imaging, i.e., moving from the electrode/sensor space to the source space using EHG signals, provide an estimate of spatial distributions of uterine activity at millisecond scale.

An electro-mechanical multiscale model of uterine pregnancy contraction.

Detecting preterm labor as early as possible is important because tocolytic drugs are much more likely to delay preterm delivery if administered early. Having good information on the real risk of premature labor also leads to fewer women who do not need aggressive treatment for premature labor threat. Currently, one of the most promising ways to diagnose preterm labor threat is the analysis of the electrohysterogram (EHG).

Effect of filtering on the classification rate of nonlinear analysis methods applied to uterine EMG signals.

Nonlinear time series analysis can provide useful information regarding nonlinear features of biological signals. The effect of filtering on the performance of nonlinear methods is not well-understood. In this work, we investigate the effects of signal filtering on the sensitivity of four nonlinear methods: Time reversibility, Sample Entropy, Lyapunov Exponents and Delay Vector Variance.

The Icelandic 16-electrode electrohysterogram database.

External recordings of the electrohysterogram (EHG) can provide new knowledge on uterine electrical activity associated with contractions. Better understanding of the mechanisms underlying labor can contribute to preventing preterm birth which is the main cause of mortality and morbidity in newborns. Promising results using the EHG for labor prediction and other uses in obstetric care are the drivers of this work.

Performance analysis of four nonlinearity analysis methods using a model with variable complexity and application to uterine EMG signals.

Several measures have been proposed to detect nonlinear characteristics in time series. Results on time series, multiple surrogates and their z-score are used to statistically test for the presence or absence of non-linearity. The z-score itself has sometimes been used as a measure of nonlinearity.

Surface EMG-force modelling for the biceps brachii and its experimental evaluation during isometric isotonic contractions.

The aim of this study was to evaluate a surface electromyography (sEMG) signal and force model for the biceps brachii muscle during isotonic isometric contractions for an experimental set-up as well as for a simulation. The proposed model includes a new rate coding scheme and a new analytical formulation of the muscle force generation. The proposed rate coding scheme supposes varying minimum and peak firing frequencies according to motor unit (MU) type (I or II).

A multiscale model of the electrohysterogram the BioModUE_PTL project.

The electrohysterogram (EHG) is a promising means of monitoring pregnancy and of detecting a risk of preterm labor. To improve our understanding of the EHG as well as its relationship with the physiologic phenomena involved in uterine contractility, we plan to model these phenomena in terms of generation and propagation of uterine electrical activity. This activity can be realistically modeled by representing the principal ionic dynamics at the cell level, the propagation of electrical activity at the tissue level and then the way it is reflected on the skin surface through the intervening tissue.

Windowed multivariate autoregressive model improving classification of labor vs. pregnancy contractions.

Analyzing the propagation of uterine electrical activity is poised to become a powerful tool in labor detection and for the prediction of preterm labor. Several methods have been proposed to investigate the relationship between signals recorded externally from several sites on the pregnant uterus. A promising recent method is the multivariate autoregressive (MVAR) model.

Preliminary global sensitivity analysis of a uterine electrical activity model.

A comprehensive multiscale model of the uterine muscle electrical activity would permit understanding the important link between the genesis and evolution of the action potential at the cell level and the process leading to labor. Understanding this link can open the way to more effective tools for the prediction of labor and prevention of preterm delivery.

Bivariate piecewise stationary segmentation; improved pre-treatment for synchronization measures used on non-stationary biological signals.

Analysis of synchronization between biological signals can be helpful in characterization of biological functions. Many commonly used measures of synchronicity assume that the signal is stationary. Biomedical signals are however often strongly non stationary.

Better pregnancy monitoring using nonlinear correlation analysis of external uterine electromyography.

The objective of this paper is to evaluate the novel method for analyzing the nonlinear correlation of the uterine electromyography (EMG). The application of this method may improve monitoring in pregnancy, labor detection, and preterm labor detection. Uterine EMG signals recorded from a 4 × 4 matrix of electrodes on the subjects' abdomen are used here.

Toward a multiscale model of the uterine electrical activity.

A comprehensive multiscale model of the uterine muscle electrical activity would permit understanding the important link between the genesis and evolution of the action potential at the cell level and the process leading to labor. Understanding this link can open the way to more effective tools for the prediction of labor and prevention of preterm delivery. A first step toward the realization of such a model is presented here.

Combination of canonical correlation analysis and empirical mode decomposition applied to denoising the labor electrohysterogram.

The electrohysterogram (EHG) is often corrupted by electronic and electromagnetic noise as well as movement artifacts, skeletal electromyogram, and ECGs from both mother and fetus. The interfering signals are sporadic and/or have spectra overlapping the spectra of the signals of interest rendering classical filtering ineffective. In the absence of efficient methods for denoising the monopolar EHG signal, bipolar methods are usually used.

Comparison between approximate entropy, correntropy and time reversibility: application to uterine electromyogram signals.

Detection of nonlinearity should be the first step before any analysis of nonlinearity or nonlinear behavior in biological signal. The question is which method should be used in each case and which one can best respect the different characteristics of the signals under investigation. In this paper we compare three methods widely used in nonlinearity detection: approximate entropy, correntropy and time reversibility.

Shape analysis and clustering of Surface EMG Data.

Functional Data Analysis (FDA) is a recent field in data analysis and processing. It provides efficient methods and tools by considering the analyzed data as realizations of functions. In this discipline, raised shape analysis approaches.

Uterine electromyogram database and processing function interface: An open standard analysis platform for electrohysterogram signals.

The uterine electromyogram or electrohysterogram (EHG) is one of the most promising biophysical markers of preterm labor. At this time no recording parameter standard exists for EHG recordings which can be a problem for the establishment of international multicentric trials. In this paper, we present a management and processing system dedicated to storing and processing EHG signals.

Optimization of input parameters of an EMG-Force model in constant and sinusoidal force contractions.

In an electromyographic and muscle force (EMG-Force) model, the variability and uncertainty of the input muscle parameters increase the difficulty of assessing this type of model. In this study, a Monte Carlo method is used to evaluate the robustness and the sensitivity of an EMG-Force model, recently developed by our team, for two groups of simulations (constant and sinusoidal force contractions). Two existing criteria (EMG/force and force/force-variability relations) and a new criterion derived from this model (Root Mean Square error, Error(RMS), between the force command and the generated force) are used to extract relevant simulations and obtain the optimized parameter ranges in constant force contractions, while only the new criterion could be valuable in sinusoidal force contractions.

Mathematical modeling of electrical activity of uterine muscle cells.

The uterine electrical activity is an efficient parameter to study the uterine contractility. In order to understand the ionic mechanisms responsible for its generation, we aimed at building a mathematical model of the uterine cell electrical activity based upon the physiological mechanisms. First, based on the voltage clamp experiments found in the literature, we focus on the principal ionic channels and their cognate currents involved in the generation of this electrical activity.

Ridge extraction from the time-frequency representation (TFR) of signals based on an image processing approach: application to the analysis of uterine electromyogram AR TFR.

Time-frequency representations (TFRs) of signals are increasingly being used in biomedical research. Analysis of such representations is sometimes difficult, however, and is often reduced to the extraction of ridges, or local energy maxima. In this paper, we describe a new ridge extraction method based on the image processing technique of active contours or snakes.

Analysis of muscular fatigue during cyclic dynamic movement.

We have investigated the electromyographic manifestations of fatigue on the Biceps Brachii in prolonged isometric and dynamic contractions by using two spectral analyses (Fourier transform (FT) and continuous wavelet transform (CWT)) as references and a novel approach cyclostationarity analysis. The isometric fatigue test shows no deviations from what is found in the literature (increase in energy (En) and decrease in mean frequency (MF)), while the dynamic fatigue test shows a slight increase in En and no change in MF for both spectral estimation techniques. In addition, the cyclostationarity increases with the fatigue and it could provide a new index of the fatigue during cyclostationary dynamic movements.

Preterm labour detection by use of a biophysical marker: the uterine electrical activity.

Background: The electrical activity of the uterine muscle is representative of uterine contractility. Its characterization may be used to detect a potential risk of preterm delivery in women, even at an early gestational stage.

Methods: We have investigated the effect of the recording electrode position on the spectral content of the signal by using a mathematical model of the women's abdomen.