New algorithm for fetal QRS detection in surface abdominal records

The proposed method detects fetal R waves on abdominal non-invasive records. An exponentially averaged pattern of the mother PQRST segment is obtained and subtracted. Subsequently the fetal R detector based on a Smoothed Nonlinear Energy Operator (SNEO) is applied to the residual signal. Finally, criteria about amplitude, heart rate and backward search are settled to correct false detections. To evaluate the fetal R detector, 10 multichannel records were used, acquired between gestation week 22 and 40. The position of the fetal R waves were manually marked (N=1490), and these reference marks were compared with the ones from the detector. It was obtained a 88.83% of sensitivity and a 91.32% of positive prediction value. The application of the detector to all the abdominal channels will probably allow improving the obtained results

A novel technique for fetal heart rate estimation from Doppler ultrasound signal

<p>Abstract</p> <p>Background</p> <p>The currently used fetal monitoring instrumentation that is based on Doppler ultrasound technique provides the fetal heart rate (FHR) signal with limited accuracy. It is particularly noticeable as significant decrease of clinically important feature - the variability of FHR signal. The aim of our work was to develop a novel efficient technique for processing of the ultrasound signal, which could estimate the cardiac cycle duration with accuracy comparable to a direct electrocardiography.</p> <p>Methods</p> <p>We have proposed a new technique which provides the true beat-to-beat values of the FHR signal through multiple measurement of a given cardiac cycle in the ultrasound signal. The method consists in three steps: the dynamic adjustment of autocorrelation window, the adaptive autocorrelation peak detection and determination of beat-to-beat intervals. The estimated fetal heart rate values and calculated indices describing variability of FHR, were compared to the reference data obtained from the direct fetal electrocardiogram, as well as to another method for FHR estimation.</p> <p>Results</p> <p>The results revealed that our method increases the accuracy in comparison to currently used fetal monitoring instrumentation, and thus enables to calculate reliable parameters describing the variability of FHR. Relating these results to the other method for FHR estimation we showed that in our approach a much lower number of measured cardiac cycles was rejected as being invalid.</p> <p>Conclusions</p> <p>The proposed method for fetal heart rate determination on a beat-to-beat basis offers a high accuracy of the heart interval measurement enabling reliable quantitative assessment of the FHR variability, at the same time reducing the number of invalid cardiac cycle measurements.</p

Comparison of Abdominal Fetal Electrocardiography and Doppler Ultrasound for FHR Variability Evaluation

Cílem této práce je porovnání dvou neinvazivních metod monitorace plodu, konkrétně fetální elektrografie (fECG) a kardiotokografie (CTG). Teoretická část je zaměřena na rešeřši dané problematiky, popisuje současný stav a jednotlivé metody monitorace plodu využívané v klinické praxi. V praktické části je uvedena kapitola věnující se problematice digitalizace kadiotokografického záznamu. Druhá část se věnuje srovnání KTG a fEKG z pohledu plodové srdeční frekvence. V práci byla využita reálně naměřená data od 5 subjektů. K extrakci fetálního EKG z abdominálního záznamu byla využita neadaptivní metoda, vycházející z analýzy nezávislých komponent, konkrétně metoda JADE. Při zpracování bylo použito vývojové prostředí MATLAB. Na konci práce je uvedeno statistické zhodnocení výsledků pomocí Bland-Altmanových grafů.The purpose of my thesis is the comparison of two non-invasive methods of fetal monitoring - a fetal electrography (fEKG) and a cardiotocography (KTG). The theoretical part of the thesis introduces my research of the topic theory and describes the current state and individual methods of fetal monitoring used in clinical practice. The first part of the experimental section of the thesis inquires into the problematics of the cardiotocographic record digitalization. The second part deals with the comparison of KTG and fEKG in terms of fetal heart rate based on the measurement of data from five tested subjects. The nonadaptive JADE method, based on the analysis of independent components, was used to extract the fetal ECG from the abdominal recording. The MATLAB software development environment was used for the data processing. The conclusion of the work focuses on the evaluation of the results using Bland-Altman graphs.450 - Katedra kybernetiky a biomedicínského inženýrstvídobř

Welche Aussage zum autonomen Reifungsstand erlaubt das konventionelle CTG im Vergleich zur fetalen Magnetkardiographie?

Mit der Analyse der fetalen Herzfrequenz (fHR) ist es möglich den fetalen Zustand und die Entwicklung des autonomen Nervensystems (ANS) einzuschätzen. Die fHR lässt sich mit verschiedenen Methoden nicht-invasiv erfassen. Die Einschätzung der autonomen Regulation erfolgt hierbei mittels Herzfrequenzvariabilitätsanalyse (HRV-Analyse). Es wurde eine Vielzahl von Parametern entwickelt, die verschiedene Aspekte der Herzfrequenzvariabilität (HRV) beschreiben können. Das Magnetkardiogramm (MKG) kann die einzelnen Herzschläge genau erfassen und schnelle Änderungen der fHR darstellen. Als elektrophysiologische Methode stellt es den Goldstandard zur fetalen HRV-Analyse dar, ist jedoch weltweit wenig etabliert, methodisch sehr aufwändig und damit klinisch nicht praktikabel. Das Kardiotokogramm (CTG) ist die technisch einfachere, in der Klinik etablierte Methode, geht aber mit einer methodisch bedingten, geringeren zeitlichen Auflösung der Herzschlagreihe einher. In dieser Arbeit soll die Vergleichbarkeit der HRV-Analyse in MKG und CTG geprüft werden, um zu ermitteln welches Potential dem CTG bei der Einschätzung der fetalen autonomen Funktion zukommt. Erwartet werden eine bedingte Vergleichbarkeit und in Teilen direkte Übertragbarkeit, insbesondere in Bezug auf globale und sympathisch dominierte Parameter der HRV. Es wurden intraindividuell bei 80 Patientinnen am selben Schwangerschaftstag aufeinanderfolgend fetale MKG- und CTG-Aufzeichnungen durchgeführt. Zur Vergleichbarkeit wurde der fetale Aktivitätszustand anhand der graphischen Darstellung des Herzfrequenzverlaufes ermittelt. Die Herzschlagreihen wurden aufbereitet und die HRV-Analyse semi-automatisch durchgeführt. Hierbei wurde neben den Ergebnissen von MKG und CTG eine dritte Signalkategorie erstellt, indem die Herzzeitreihe des MKG technisch auf die zeitliche Auflösung des CTG reduziert wurde („downsampling“). ..

Symbolic Dynamics Analysis: a new methodology for foetal heart rate variability analysis

Cardiotocography (CTG) is a widespread foetal diagnostic methods. However, it lacks of objectivity and reproducibility since its dependence on observer's expertise. To overcome these limitations, more objective methods for CTG interpretation have been proposed. In particular, many developed techniques aim to assess the foetal heart rate variability (FHRV). Among them, some methodologies from nonlinear systems theory have been applied to the study of FHRV. All the techniques have proved to be helpful in specific cases. Nevertheless, none of them is more reliable than the others. Therefore, an in-depth study is necessary. The aim of this work is to deepen the FHRV analysis through the Symbolic Dynamics Analysis (SDA), a nonlinear technique already successfully employed for HRV analysis. Thanks to its simplicity of interpretation, it could be a useful tool for clinicians. We performed a literature study involving about 200 references on HRV and FHRV analysis; approximately 100 works were focused on non-linear techniques. Then, in order to compare linear and non-linear methods, we carried out a multiparametric study. 580 antepartum recordings of healthy fetuses were examined. Signals were processed using an updated software for CTG analysis and a new developed software for generating simulated CTG traces. Finally, statistical tests and regression analyses were carried out for estimating relationships among extracted indexes and other clinical information. Results confirm that none of the employed techniques is more reliable than the others. Moreover, in agreement with the literature, each analysis should take into account two relevant parameters, the foetal status and the week of gestation. Regarding the SDA, results show its promising capabilities in FHRV analysis. It allows recognizing foetal status, gestation week and global variability of FHR signals, even better than other methods. Nevertheless, further studies, which should involve even pathological cases, are necessary to establish its reliability.La Cardiotocografia (CTG) è una diffusa tecnica di diagnostica fetale. Nonostante ciò, la sua interpretazione soffre di forte variabilità intra- e inter- osservatore. Per superare tali limiti, sono stati proposti più oggettivi metodi di analisi. Particolare attenzione è stata rivolta alla variabilità della frequenza cardiaca fetale (FHRV). Nel presente lavoro abbiamo suddiviso le tecniche di analisi della FHRV in tradizionali, o lineari, e meno convenzionali, o non-lineari. Tutte si sono rivelate efficaci in casi specifici ma nessuna si è dimostrata più utile delle altre. Pertanto, abbiamo ritenuto necessario effettuare un’indagine più dettagliata. In particolare, scopo della tesi è stato approfondire una specifica metodologia non-lineare, la Symbolic Dynamics Analysis (SDA), data la sua notevole semplicità di interpretazione che la renderebbe un potenziale strumento di ausilio all’attività clinica. Sono stati esaminati all’incirca 200 riferimenti bibliografici sull’analisi di HRV e FHRV; di questi, circa 100 articoli specificamente incentrati sulle tecniche non-lineari. E’ stata condotta un’analisi multiparametrica su 580 tracciati CTG di feti sani per confrontare le metodologie adottate. Sono stati realizzati due software, uno per l’analisi dei segnali CTG reali e l’altro per la generazione di tracciati CTG simulati. Infine, sono state effettuate analisi statistiche e di regressione per esaminare le correlazioni tra indici calcolati e parametri di interesse clinico. I risultati dimostrano che nessuno degli indici calcolati risulta più vantaggioso rispetto agli altri. Inoltre, in accordo con la letteratura, lo stato del feto e le settimane di gestazione sono parametri di riferimento da tenere sempre in considerazione per ogni analisi effettuata. Riguardo la SDA, essa risulta utile all’analisi della FHRV, permettendo di distinguere – meglio o al pari di altre tecniche – lo stato del feto, la settimana di gestazione e la variabilità complessiva del segnale. Tuttavia, sono necessari ulteriori studi, che includano anche casi di feti patologici, per confermare queste evidenze

Exploring tentativeness: risk, uncertainty and ambiguity in first time pregnancy

This thesis explores fifteen women’s accounts of pregnancy over the course of gestation. It highlights the fluidity and dynamism of these women’s experiences, placing these in the context of the breadth of medical interventions they engaged with. Much existing literature concerning pregnancy focuses on specific instances of contact with medical professionals or technological interventions. This study explores the mundane and routine elements of the everyday practice of pregnancy, including during the first trimester. This is a period rarely addressed in academic literature. The thesis draws on data from in-depth interviews with women in Scotland, experiencing a continuing pregnancy for the first time. These were conducted at three points over the course of gestation. Interviews aimed to explore women’s interactions with medical interventions, their conceptualisations of the foetus, and changing experiences of embodiment. Analysis took place in several stages, incorporating three ‘readings’ of interviews and the development of a case study for each participant. This was inspired by the voice centred relational method of analysis. Themes were then identified and developed within, and between, individual women’s accounts. Participants’ narratives, particularly in early pregnancy, resonated with Rothman’s (1988) concept of the ‘tentative pregnancy’, originally developed to describe pregnancy in the wake of amniocentesis. Tentativeness emerged as a key theme characterising women’s experiences. Tentativeness was especially evident during the first trimester, largely due to women’s understanding that the risk of miscarriage was at its highest during this period. Women described managing their emotions at this time, in order to balance excitement about their wanted pregnancy with the possibility that it may end in a pregnancy loss. One aspect of this emotion work, explored in this thesis, was the effort made by women to keep their pregnancy a secret from wider family and friends for the first twelve weeks of gestation. Medical intervention and its associated technologies played a key role in both constructing pregnancy as tentative, but paradoxically, also provided a means to resolve this through reassurance. Women engaged with these interventions flexibly. In contrast to much existing literature, this thesis highlights that while contact with prenatal technologies cemented the reality of the pregnancy for some, they also had the power to add to the ambiguity of participants’ status as a ‘pregnant woman’. In later pregnancy, women’s shifting embodied experiences contributed to a reduction in tentativeness. The ability to feel definite foetal movements, coupled with medical and popular discourses of foetal viability, allowed women to feel less anxious about the safety of the pregnancy and the foetus. As a result, women reported changed interactions with health professionals and advice during the final trimester of pregnancy. This thesis, engaging with literature from sociology, science and technology studies (STS) and anthropology, makes theoretical contributions in three areas. First, its consideration of gestation over time nuances discussions of pregnancy in terms of risk. Second, this research further contributes to literature regarding pregnant embodiment, and conceptualisations of the foetus. Third, the thesis demonstrates that relationships between forms of knowledge mobilised by participants during pregnancy were complex, shifting over the course of gestation, and reflective of women’s experiences of pregnancy as tentative