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Kynning á doktorsverkefni - Ahmad Diab

  • 29.1.2015, 14:00 - 15:00

Dr. Ahmad Diab mun kynna doktorsverkefni sitt  „Study of the Nonlinear Properties and Propagation Characteristics of the Uterine Electrical Activity During Pregnancy and Labor“  29. janúar kl. 14 í stofu M208.
Ahmad varði doktorsritgerð sína 11. júlí 2014 við Université de Technology de Compiègne í Frakklandi. Verkefnið var unnið við Háskólann í Reykjavík og Université de Technology de Compiègne háskóla undir leiðsögn Brynjars Karlssonar og Catherine Marque. 

Abstract

The uterine EMG -called Electrohysterogramme (EHG)- has temporal, frequency, and time-frequency characteristics which have been used before in attempts for the prediction of preterm labor. The investigation of aspects of synchronization and propagation of EHG has more recently become the centre of attention for research on how to adequately predict labor. Results of previous studies have however not shown satisfactory performance for clinical use. The objective of this thesis is the analysis of the propagation as well as of the nonlinear characteristics of EHG signals during pregnancy and labor in view of future clinical application. A monovariate analysis of single electrodes was done to investigate the nonlinearity of the signals and the sensibility of several methods of detecting non-linearity to different characteristics of the signals. An innovative bivariate analysis was then done for the investigation of the propagation of EHG by measuring the coupling between channels, as well as the direction of coupling. In this analysis we propose a new approach to improve the methods of coupling and direction estimation. Another innovation of this thesis is the implementation of a tool for EHG source localization to investigate the dynamic of the uterus at the source level, not at the detection or electrode level as previously done. Results show that nonlinear methods are better for classifying pregnancy and labor contractions than linear ones and that time reversibility method is the least sensitive to sampling frequency and frequency content of the signal. Results also indicate an increase in coupling and a concentration of coupling direction toward the cervix when going from pregnancy to labor. We also proposed to respect the nonstationarity of EHG signal and to recover the effect of variable fat filtering along pregnancy, by segmenting and filtering the EHG in its FWL component. This filtering-windowing approach permits us to improve the performances of the connectivity methods used. Finally, we show that the intensity of localized sources and their number is higher in labor than in pregnancy contractions. The sources identified are more active and more propagated in labor whereas in pregnancy they remain weak and local. An improvement in the electrode matrix of a rat experimental protocol has also been done by developing a suction electrode. This protocol can then be used for the validation of our methods in a rat model and of an electrophysiological computational model. 



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