TY  - THES
T1  - Characterization of Labor: a Magnetomyography Approach
T3  - published in: Physiological Measurement, 2009, vol. 30, num. 10, p. 1051-1060, PMID: 19738317, http://dx.doi.org/10.1088/0967-3334/30/10/006 ; Conference Proceedings: IEEE Engineering in Medicine and Biology Society, Aug. 2011, p. 6025-6028, PMID: 22255713; European Journal of Obstetrics, Gynecology, and Reproductive Biology, 2009, vol. 144 Suppl 1, p. S96-100, PMID: 19303190.
A1  - Furdea,Adrian
Y1  - 2012/10/01
N2  - Premature labor and delivery is a major cause of infant mortality and morbidity. Advances in the fields of medicine and engineering together with a better understanding of the preterm birth related risk factors have successfully reduced their incidence. Despite such advances, in most developed countries the preterm birth rate is still high, accounting for about 85% of infant mortality and more than 50% of the surviving infant's morbidity. The timely prediction of premature labor and delivery can improve the effectiveness of the required treatments. Unfortunately, the techniques employed in current obstetrical practice proved to be inaccurate for the prediction of premature labor and delivery.
The contractile element of the uterus is the myometrium, which consists of smooth muscle cells. The electrical activity (always accompanied by magnetic activity) in form of action potentials (AP) propagates through the myometrial cells causing the contraction of the uterus. Magnetomyography (MMG) is the noninvasive measurement of the uterine magnetic activity by means of equally spaced magnetic sensors arranged in a concave array. The MMG recordings display advantages which renders them suitable for the analysis and characterization of the uterine activity. Compared to electromyography signals, the MMG signals are detectable outside the boundary of the skin without making any contact with the body. Also they are independent on conductivity geometry, i.e. tissue conductivity. The measured electrical activity arises from volume currents  owing (in the body) to the electrode sites and not directly due to the primary current generators.
The current work presents a set of methods designated to identify and characterize uterine contractile activity and its dynamics in MMG signals. The basic process controlling the uterine contraction is the underlying electrical activity in the form of APs which propagate between muscle cells and open ion channels allowing the influx of calcium ions to produce a contraction. APs occur in groups and form a burst of activity which in humans can last more than a minute. The ultimate goal is to provide a timely prediction of delivery. More precisely, a multi-sensor analysis of the spatial propagation properties of the MMG signals is carried out to identify time segments of uterine burst activity. This type of analysis is of particular relevance because the spreading of magnetic activity in the myometrium results in coordinated contractions (close to term), capable to push the fetus into the birth canal and ultimately lead to delivery. Therefore, the analysis of the spatial propagation properties (within segments of contractile activity), i.e. conduction velocity (CV), could provide a fundamental contribution for the prediction of delivery.
It could be shown that the HTWD approach can be used for the successful identification of uterine contractions. To mark the contractile intervals, a discrete-time binary decision signal was created in each magnetic sensor. The information provided by this approach was further used to determine the CV of the uterine contraction bursts and it was shown that the increase in the CV can be considered as a possible predictor of preterm labor. Significant benefits could be expected from the introduction of MMG signal analysis for routine contraction monitoring. Further clinical validations are required to assess the robustness of the presented methods and to account for physiological differences among subjects.
KW  - Wehen
KW  - Zeit-Frequenz-Analyse
KW  - Signalanalyse
CY  - Tübingen
PB  - Universitätsbibliothek Tübingen
AD  - Wilhelmstr. 32, 72074 Tübingen
UR  - http://tobias-lib.uni-tuebingen.de/volltexte/2012/6457
ER  -