Agnieszka Kitlas

Uterine contraction signals―Application of the linear synchronization measures

OBJECTIVE In physiological research, there are not too many studies on multivariate data sets, containing two or more simultaneously recorded time series. It is important to examine synchronization in these kinds of signals. The aim of this study is to present the linear measures: the cross-correlation function, the coherence function, the wavelet cross-correlation and the wavelet coherence to assess synchronization between contractions in different topographic regions of the uterus. STUDY DESIGN Spontaneous uterine activity was recorded directly by a dual micro-tip catheter (Millar Instruments, Inc., USA). The device consisted of two ultra-miniature pressure sensors. One sensor was placed in the fundus, the other one in the cervix. For this analysis, a healthy patient with normal contractions, a patient with dysmenorrhea, a patient with fibromyomas in the follicular phase, and the patient with endometriosis were selected. RESULTS For each method the values of synchronization parameters for normal contractions were higher than the values of these parameters for other pairs of signals. The differences between these four groups of the uterine contraction signals were clear. The lowest values of the synchronization measures were in the case of dysmenorrheic patient. CONCLUSION The analysis of synchronization of the uterine contractions signals may have a diagnostic value. For intrauterine pressure signals results obtained by means of different synchronization methods are different, but consistent.

Nonlinear Dynamics in Uterine Contractions Analysis

Analysis of the uterine contractility in non-pregnant women provides information about physiological changes during menstrual cycle. Spontaneous uterine activity was recorded directly by a micro-tip catheter (Millar Instruments, Inc. USA). The sensor produced an electrical signal, which varied in direct proportion to the magnitude of measured pressure. The study was approved by the regional ethics committee. We used the techniques of surrogate data analysis to testing for nonlinearity in the uterine contraction signals. Approximate entropy was the test statistic. For this analysis a healthy patient with normal contractions, a patient with dysmenorrhea and a patient with fibromyomas in the follicular phase were selected. The results showed that the spontaneous uterine contractions are considered to contain nonlinear features.

Fractal analysis of medical images in the irregular regions of interest

For medical images diagnostically important information often lies in the texture. Fractal dimension may be used as an index of irregularity. In this paper we describe the adaptation of the intensity difference scaling method for assessment of the fractal dimension D in the irregular regions of interest (irregular ROIs). This is of great importance because the investigated regions are often small. It is difficult to fit entire regular region of interest within the examined organ with simultaneous inclusion of the relevant fragment, and at the same time to avoid the influence of boundaries. Fractal analysis of various kinds of medical images: panoramic radiography and nuclear medicine scan showed the validity of assessment of D in irregular ROIs.

Fractal Analysis of Dental Radiographic Images in the Irregular Regions of Interest

The irregularity or ”roughness” of medical images is quantified by means of fractal dimension D. For medical images diagnostically important information often lies in the texture. In this paper we describe the application of the intensity difference scaling method for assessment of the fractal dimension D in the irregular regions of interest (irregular ROI-s). Near boundary between different tissues or structures the values of fractal dimensions changed significantly. It is difficult to fit entire regular region of interest within the examined organ with simultaneous inclusion of the relevant fragment, and at the same time to avoid the influence of boundaries.

Fractal Analysis of the Uterine Contractions.

The fractal dimension D may be calculated in many ways, since its strict definition, the Hausdorff definition is too complicated for practical estimation. In this paper we perform a comparative study often methods of fractal analysis of time series. In Benoit, a commercial program for fractal analysis, five methods of computing fractal dimension of time series (rescaled range analysis, power spectral analysis, roughness-length, variogram methods and wavelet method) are available. We have implemented some other algorithms for calculating D: Higuchis fractal dimension, relative dispersion analysis, running fractal dimension, method based on mathematical morphology and method based on intensity differences. For biomedical signals results obtained by means of different algorithms are different, but consistent.

Uterine contractility: visualization of synchronization measures in two simultaneously recorded signals.

Abstract:  The analysis of the uterine contraction signals in nonpregnant states gives information about physiological changes during the menstrual cycle. Spontaneous uterine activity was recorded directly by a dual microtip catheter. The device consisted of two ultra‐miniature pressure sensors. One sensor was placed in the fundus, the other in the cervix. It was important to identify time delays between contractions in two topographic locations, which may be of potential diagnostic significance in various pathologies: dysmenorrhea, endometriosis, and fecundity disorders. In this study the following synchronization measures—the cross‐correlation, the semblance, the mutual information—were used to visualize the time delay changes over time. These measures were computed in a moving window with a width corresponding to approximately two or three contractions. As a result, the running synchronization functions were obtained. The running synchronization functions visualize changes in the propagation of the two simultaneously recorded signals. The propagation% parameter assessed from these functions allows for quantitative description of synchronization. Finally, we illustrate the use of running synchronization functions to investigate the effect of treatment with tamoxifen on primary dysmenorrhea.

Signal Processing Methods in the Analysis of the Uterine Contractility

The aim of this study is to evaluate synchronization of signals representing uterine contraction activity by means of linear signal processing methods – power spectrum, coherence measure, wavelet power spectrum and wavelet coherence measure. We present results of this analysis for patients with primary dysmenorrhea, uterine myomas, endometriosis and for a healthy woman. Using these methods we have found that primary dysmenorrhea, endometriosis and uterine myomas are accompanied by the uterine contraction disorders. Our analysis will allow more precise diagnostics and better control of treatment.

Synchronization in the bivariate intrauterine pressure signals' nonlinear dynamics methods.

It was shown earlier that nonlinear processes probably generate uterine contractions. In this study, the nonlinear synchronization measures (the mutual correlation dimension, the cross-approximate entropy, the mutual information and the nonlinear interdependencies) were employed to analyze the association between two time series representing the uterine contraction activity. Here the notion of synchronization is used in a loose sense as the synonym of correlation, the similarity of the signals or the similarity of their dynamics. The signals were recorded from the different topographic regions of the uterus: the cervix and the fundus. The results obtained by means of different algorithms are different but qualitatively similar for the checked methods.