347 results on '"Bergmans, J.W.M."'
Search Results
2. Cognitive deterioration in adult epilepsy: Does accelerated cognitive ageing exist?
- Author
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Breuer, L.E.M., Boon, P., Bergmans, J.W.M., Mess, W.H., Besseling, R.M.H., de Louw, A., Tijhuis, A.G., Zinger, S., Bernas, A., Klooster, D.C.W., and Aldenkamp, A.P.
- Published
- 2016
- Full Text
- View/download PDF
3. System study on nonlinear suppression of varying-envelope local interference in multimode transceivers
- Author
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Habibi, H., Janssen, E.J.G., Yan, Wu, Bergmans, J.W.M., and Baltus, P.G.M.
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- 2015
- Full Text
- View/download PDF
4. Enhanced illumination sensing using multiple harmonics for LED lighting systems
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Hongming Yang, Schenk, T.C.W., Bergmans, J.W.M., and Pandharipande, A.
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Frequency modulation -- Analysis ,Harmonic functions -- Usage ,Light-emitting diodes -- Usage ,Signal processing -- Innovations ,Digital signal processor ,Business ,Computers ,Electronics ,Electronics and electrical industries - Published
- 2010
5. Noninvasive estimation of the electrohysterographic action-potential conduction velocity
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Rabotti, C., Mischi, M., Oei, S.G., and Bergmans, J.W.M.
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Electromyography -- Usage ,Electromyography -- Analysis ,Electrophysiology -- Research ,Fetal heart rate -- Measurement ,Maximum likelihood estimates (Statistics) -- Usage ,Biological sciences ,Business ,Computers ,Health care industry - Published
- 2010
6. Bayesian approach to patient-tailored vectorcardiography
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Vullings, R., Peters, C.H.L., Mossavat, I., Oei, S.G., and Bergmans, J.W.M.
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Bayesian statistical decision theory -- Usage ,Cardiography -- Innovations ,Fetal monitoring -- Technology application ,Signal processing -- Analysis ,Digital signal processor ,Technology application ,Biological sciences ,Business ,Computers ,Health care industry - Published
- 2010
7. Illumination sensing in LED lighting systems based on frequency-division multiplexing
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Hongming Yang, Bergmans, J.W.M., and Schenk, T.
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Light-emitting diodes -- Analysis ,Electric lighting -- Analysis ,Lighting -- Analysis ,Modulation (Electronics) -- Analysis ,Business ,Computers ,Electronics ,Electronics and electrical industries - Published
- 2009
8. On the optimality of the null subcarrier placement for blind carrier offset estimation in OFDM systems
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Wu, Yan, Attallah, Samir, and Bergmans, J.W.M.
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Mathematical optimization -- Research ,Estimation theory -- Research ,Business ,Electronics ,Electronics and electrical industries ,Transportation industry - Abstract
Liu and Tureli proposed a blind carrier frequency offset (CFO) estimation method for orthogonal frequency-division multiplexing (OFDM) systems, making use of null subcarriers. The optimal subcarrier placement that minimizes the Cramer-Rao bound (CRB) of the CFO estimation was reported by Ghogho et al. In this paper, we study the optimality of the null subcarrier placement from another perspective. We first show that the SNR of the CFO estimation using null subcarriers is a function of the null subcarrier placement. We then formulate the CFO-SNR optimization for the null subcarrier placement as a convex optimization problem for small CFO values and derive the optimal placement when the number of subcarriers is a multiple of the number of null subcarriers. In addition, we show that the SNR-optimal null subcarrier placement also minimizes the theoretical mean square error in the high SNR region. When the number of subcarriers is not a multiple of the number of null subcarriers, we propose a heuristic method for the null subcarrier placement that still achieves good performance in the CFO estimation. We also discuss the optimality of the null subcarrier placement in practical OFDM systems, where guard bands are required at both ends of the spectrum. Index Terms--Blind carrier offset estimation, convex optimization, orthogonal frequency-division multiplexing (OFDM).
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- 2009
9. Pilot-aided angle-domain channel estimation techniques for MIMO-OFDM systems
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Huang, Li, Ho, Chin Keong, Bergmans, J.W.M., and Willems, Frans M.J.
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MIMO communications -- Research ,Communications circuits -- Design and construction ,Spatial analysis (Statistics) -- Methods ,Business ,Electronics ,Electronics and electrical industries ,Transportation industry - Abstract
Early multiple-input multiple-output with orthogonal frequency division multiplexing (MIMO-OFDM) channel estimation techniques treat channels as spatially uncorrelated. However, in many situations, MIMO-OFDM channels tend to be spatially correlated, for example, due to limited scattering. For such channels, estimation performance can be improved through exploitation of prior knowledge of the channel spatial correlation, for example, by means of the linear multiple mean square error (MMSE) technique. This knowledge is, however, not always available. As an alternative, we investigate techniques in the angle domain, where the MIMO-OFDM channel model lends itself to a physical interpretation. Our theoretical analysis and simulation results indicate that the proposed angle-domain approximated MMSE (AMMSE) channel estimation technique performs well in terms of the mean square error (mse) for various channel models representing different indoor environments. When a suitable threshold is chosen, we can use the angle-domain most-significant-taps selection technique instead of the angle-domain AMMSE technique to simplify the channel estimation procedure with little performance loss. Index Terms--Channel estimation, multiple-input multiple-output (MIMO), orthogonal frequency division multiplexing (OFDM), spatial correlation.
- Published
- 2008
10. Minimum-latency tracking of rapid variations in two-dimensional storage systems
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Van Beneden, S., Riani, J., Bergmans, J.W.M., and Immink, A.H.J.
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Optical storage devices -- Research ,Business ,Electronics ,Electronics and electrical industries - Abstract
The trend of increasing storage densities results in growing sensitivity of system performance to variations of storage channel parameters. To counteract these variations, more adaptivity is needed in the data receiver. Accurate tracking of rapid variations is limited by latencies in the adaptation loops. These latencies are largely governed by delays of the bit detector. In two-dimensional storage systems, data are packaged in a group of adjacent tracks or rows, and for some of the rows the detection delays can increase dramatically with respect to one-dimensional systems. As a result, the effective latencies in the adaptation loops preclude the tracking of rapid variations and really limit the performance of the system. In this paper, a scheme is proposed that overcomes this problem and that can be used for timing recovery, automatic gain control, and other adaptive circuits. Rapid variations for all the rows are tracked using control information from rows for which detector latency is smallest. This works properly if rapid variations are common across the rows as is the case, for example, for the two-dimensional optical storage (TwoDOS) system. Experimental results for TwoDOS confirm that the scheme yields improved performance with respect to conventional adaptation schemes. Index Terms--Adaptation, minimum latency, rapid variations, two-dimensional storage.
- Published
- 2007
11. Data-aided timing recovery for recording channels with data-dependent noise
- Author
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Riani, J., Bergmans, J.W.M., van Beneden, S., and Immink, A.
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Computer storage devices -- Analysis ,Maximum likelihood estimates (Statistics) -- Usage ,Digital filters -- Design and construction ,Data storage device ,Business ,Electronics ,Electronics and electrical industries - Abstract
In high-density data storage systems, noise becomes highly correlated and data dependent as a result of media noise, channel nonlinearities, and front-end filters. In such environments, conventional timing recovery schemes will exhibit large residual timing jitter and, especially, data-dependent timing jitter. This paper presents a new data-aided timing recovery algorithm for data storage systems with data-dependent noise. We derive a maximum-likelihood timing recovery scheme based on a data-dependent Gauss-Markov model of the noise. The timing recovery algorithm incorporates data-dependent noise prediction parameters in the form of linear prediction filters and prediction error variances. Moreover, because noise can be nonstationary in practice, we propose an adaptive algorithm to estimate and track the noise prediction parameters. Simulation results, for an idealized optical storage channel incorporating a simple model of media noise, illustrate the merits of our algorithm. Index Terms--Data-dependent noise, digital recording, partial-response techniques, timing-recovery.
- Published
- 2006
12. Cancellation of linear intersymbol interference for two-dimensional storage systems
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Van Beneden, S., Riani, J., Bergmans, J.W.M., and Immink, A.H.J.
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Optical storage devices -- Research ,Electromagnetism -- Research ,Business ,Electronics ,Electronics and electrical industries - Abstract
This paper discusses the cancellation of linear intersymbol interference (ISI) in two-dimensional (2-D) systems. It develops a theory for the error rate of receivers that use tentative decisions to cancel ISI. It also formulates precise conditions under which such ISI cancellation can be applied effectively. For many 2-D systems, these conditions are easily met, and therefore the application of ISI cancellation is of significant interest. The theory and the conditions are validated by simulation results for a 2-D channel model. Furthermore, results for an experimental 2-D optical storage system show that, for a single-layer disk with a capacity of 50 GB, a substantial performance improvement may be obtained by applying ISI cancellation. Index Terms--Cross-talk cancellation, intersymbol interference cancellation, residual intersymbol interference, two-dimensional optical storage.
- Published
- 2006
13. Structure and adjustment of a novel write-precomposition scheme
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Bergmans, J.W.M., Voorman, J.O., and Wong-Lam, H.W.
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Magnetic recorders and recording -- Research ,Digital recording -- Research ,Magnetic fields -- Research ,Business ,Electronics ,Electronics and electrical industries - Abstract
At high data rates and information densities, recorded data patterns in digital magnetic recording systems can exhibit severe nonlinearities. Key causes for these nonlinearities are bandwidth limitations of the write path and demagnetizing fields in the recording medium. The present note reviews the structure of these nonlinearities, develops a simple yet generic write-precompensation scheme that is capable of counteracting them, and derives a technique for adjusting this scheme according to information extracted within the data receiver. Index Terms - Nonlinearities, recording channels, system theory and modeling
- Published
- 1999
14. Dual-DFE read/write channel IC for hard-disk drives
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Bergmans, J.W.M., Voorman, J.O., Groenewold, G., Hollmann, H.D.L., Jong, G.W. de, Lugthart, M.L., Pothast, J., Ramaekers, J.A.M., Ramalho, J.N.V., Riel, L.F.H. van, Veenstra, H., Wong-Lam, H.W., Medley, D.H., Dakshinamurthy, R., Davis, P.F., Mosqueda, G.S., Raman, S., and Wang, J.
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Disk drives -- Design and construction ,Read/write heads -- Research ,Integrated circuits -- Design and construction ,Business ,Electronics ,Electronics and electrical industries - Abstract
The channel IC described here achieves data rates of 360 Mb/s at performance levels that improve in various directions upon the state of the art. It accomplishes these feats in a mature 1 [[micro]meter] CBiCMOS technology at a readmode power consumption of only 800 mW. The paper discusses some of the underlying architectural concepts.
- Published
- 1998
15. Dual decision feedback equalizer
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Bergmans, J.W.M., Voorman, J.O., and Wong-Lam, H.W.
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Decoders -- Models ,Signal detection (Electronics) -- Research ,Digital recording -- Research ,Magnetic recorders and recording -- Research - Abstract
The detector of Dahlman and Gudmundson ranks among the simplest known extensions of the decision feedback equalizer (DFE). The present note develops a simplification of this detector, and evaluates its performance vis-a-vis other near maximum likelihood detectors. Comparable performances are observed at much lower complexity levels. Index Terms - Decision-feedback equalization, detection, digital recording, equalization, magnetic recording, Viterbi detection.
- Published
- 1997
16. Decision feedback equalization for run-length-limited codes with d = 1
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Bergmans, J.W.M.
- Subjects
Feedback control systems -- Models ,Feedback (Electronics) -- Analysis ,Modulation (Electronics) -- Analysis ,Business ,Electronics ,Electronics and electrical industries - Abstract
This paper provides a survey of decision feedback equalization for runlength-limited modulation codes with minimum run-length parameter d = 1. The survey covers existing approaches such as the zero-forcing and multi-level decision feedback equalizer, as well as a novel one which exploits two pre-cursive intersymbol interference components. Performances of these approaches are analyzed mathematically, and are pitted against those of (1,7)ML and EEPRML for a Lorentzian channel.
- Published
- 1996
17. Baud-rate data-aided timing recovery for digital magnetic recording systems with quadra-phase modulation code
- Author
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Bergmans, J.W.M.
- Subjects
Phase modulation -- Research ,Magnetic recorders and recording -- Research ,Coincidence circuits -- Research - Abstract
Quadra-Phase (QP) is a binary modulation code with desirable features for use in digital magnetic recording. This letter describes simple data-aided timing acquisition and tracking techniques for QP that do not involve any oversampling and automatically achieve word synchronization.
- Published
- 1995
18. Effect of binary modulation codes with rate R= 1/N on equivalent discrete-time models for channels with intersymbol interference
- Author
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Bergmans, J.W.M.
- Subjects
Data communications -- Research ,Modulation (Electronics) -- Research ,Signal theory (Telecommunication) -- Research - Abstract
For a data transmission system with intersymbol interference and noise in which signaling occurs by means of nonoverlapping rectangular pulses, a relation between the equivalent discrete-time models for uncoded and coded transmission is derived. It applies to binary modulation codes with rate R = 1 / N, where N is a positive integer. Examples suggest that these models are often affected by coding in a manner that is incompatible with a commonly adopted definition of coding gain.
- Published
- 1992
19. Transition detector for CD and DVD
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Bergmans, J.W.M., Coene, W.M.J., Otte, R., and Bramwell, S.
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Detectors -- Testing ,Compact discs -- Testing ,Digital video disk -- Testing ,Business ,Electronics and electrical industries ,Engineering and manufacturing industries - Abstract
This bit detector for d = 2 modulation codes is remarkably simple, supports very high data rates, can be adaptive, and is capable of handling nonlinearities. Performance approaches that of a full-fledged maximum-likelihood sequence detector. Keywords--optical recording, run-length-limited codes, bit-detection, maximum-likelihood sequence detection, CD, DVD.
- Published
- 2000
20. Dynamic T2* and S0 mapping towards real-time multi-echo fMRI denoising
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Heunis, J.S., Besseling, R.M.H., Lamerichs, R.M.J.N., de Louw, A.J.A., Aldenkamp, A.P., Bergmans, J.W.M., and Signal Processing Systems
- Published
- 2018
21. Robust reconstruction of sensor swarms floating through enclosed environments
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Duisterwinkel, E., Dubbelman, G., Demi, L., Talnishnikh, Elena, Wörtche, H.J., Bergmans, J.W.M., Duisterwinkel, E., Dubbelman, G., Demi, L., Talnishnikh, Elena, Wörtche, H.J., and Bergmans, J.W.M.
- Abstract
A novel type of application for the exploration of enclosed or otherwise difficult to access environments requires large quantities of miniaturized sensor nodes to perform measurements while they traverse the environment in a “go with the flow” approach. Examples of these are the exploration of underground cavities and the inspection of industrial pipelines or mixing tanks, all of which have in common that the environments are difficult to access and do not allow position determination using e.g. GPS or similar techniques. The sensor nodes need to be scaled down towards the millimetre range in order to physically fit through the narrowest of parts in the environments and should measure distances between each other in order to enable the reconstruction of their positions relative to each other in offline analysis. Reaching those levels of miniaturization and enabling reconstruction functionality requires: 1) novel reconstruction algorithms that can deal with the specific measurement limitations and imperfections of millimetre-sized nodes, and 2) improved understanding of the relation between the highly constraint hardware design space of the sensor nodes and the reconstruction algorithms. To this end, this work provides a novel and highly robust sensor swarm reconstruction algorithm and studies the effect of hardware design trade-offs on its performance. Our findings based on extensive simulations, which push the reconstruction algorithm to its breaking point, provide important guidelines for the future development of millimetre-sized sensor nodes.
- Published
- 2018
22. On the generalizability of ECG-based obstructive sleep apnea monitoring: merits and limitations of the Apnea-ECG database
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Papini, G.B., Fonseca, P., Margarito, J., Gilst, M.M. van, Overeem, S., Bergmans, J.W.M., Vullings, R., Papini, G.B., Fonseca, P., Margarito, J., Gilst, M.M. van, Overeem, S., Bergmans, J.W.M., and Vullings, R.
- Abstract
Contains fulltext : 200282.pdf (publisher's version ) (Closed access), Obstructive sleep apnea syndrome (OSAS) is a sleep disorder that affects a large part of the population and the development of algorithms using cardiovascular features for OSAS monitoring has been an extensively researched topic in the last two decades. Several studies regarding automatic apneic event classification using ECG derived features are based on the public Apnea-ECG database available on PhysioNet. Although this database is an excellent starting point for apnea topic investigations, in our study we show that algorithms for apneic-epochs classification that are successfully trained on this database (sensitivity < 85%, false detection rate <20%) perform poorly (sensitivity\textit<55%, false detection rate < 40%) in other databases which include patients with a broader spectrum of apneic events and sleep disorders. The reduced performance can be related to the complexity of breathing events, the increased number of non-breathing related sleep events, and the presence of non-OSAS sleep pathologies.
- Published
- 2018
23. Detection rate of fetal distress using contraction-dependent fetal heart rate variability analysis
- Author
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Warmerdam, G.J.J., Vullings, R., Laar, J.O.E.H. van, Hout-van der Jagt, M.B. van der, Bergmans, J.W.M., Schmitt, L., Oei, S.G., Warmerdam, G.J.J., Vullings, R., Laar, J.O.E.H. van, Hout-van der Jagt, M.B. van der, Bergmans, J.W.M., Schmitt, L., and Oei, S.G.
- Abstract
Item does not contain fulltext, OBJECTIVE: Monitoring of the fetal condition during labor is currently performed by cardiotocograpy (CTG). Despite the use of CTG in clinical practice, CTG interpretation suffers from a high inter- and intra-observer variability and a low specificity. In addition to CTG, analysis of fetal heart rate variability (HRV) has been shown to provide information on fetal distress. However, fetal HRV can be strongly influenced by uterine contractions, particularly during the second stage of labor. Therefore, the aim of this study is to examine if distinguishing contractions from rest periods can improve the detection rate of HRV features for fetal distress during the second stage of labor. APPROACH: We used a dataset of 100 recordings, containing 20 cases of fetuses with adverse outcome. The most informative HRV features were selected by a genetic algorithm and classification performance was evaluated using support vector machines. MAIN RESULTS: Classification performance of fetal heart rate segments closest to birth improved from a geometric mean of 70% to 79%. If the classifier was used to indicate fetal distress over time, the geometric mean at 15 minutes before birth improved from 60% to 72%. SIGNIFICANCE: Our results show that combining contraction-dependent HRV features with HRV features calculated over the entire fetal heart rate signal improves the detection rate of fetal distress.
- Published
- 2018
24. On the generalizability of ECG-based obstructive sleep apnea monitoring: merits and limitations of the Apnea-ECG database
- Author
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Papini, G., Fonseca, P., Margarito, Jenny, van Gilst, M.M., Overeem, S., Bergmans, J.W.M., Vullings, R., Papini, G., Fonseca, P., Margarito, Jenny, van Gilst, M.M., Overeem, S., Bergmans, J.W.M., and Vullings, R.
- Abstract
Obstructive sleep apnea syndrome (OSAS) is a sleep disorder that affects a large part of the population and the development of algorithms using cardiovascular features for OSAS monitoring has been an extensively researched topic in the last two decades. Several studies regarding automatic apneic event classification using ECG derived features are based on the public Apnea-ECG database available on PhysioNet. Although this database is an excellent starting point for apnea topic investigations, in our study we show that algorithms for apneic-epochs classification that are successfully trained on this database (sensitivity < 85%, false detection rate <20%) perform poorly (sensitivity\textit<55%, false detection rate < 40%) in other databases which include patients with a broader spectrum of apneic events and sleep disorders. The reduced performance can be related to the complexity of breathing events, the increased number of non-breathing related sleep events, and the presence of non-OSAS sleep pathologies.
- Published
- 2018
25. Effect of loop delay on stability of discrete-time PLL
- Author
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Bergmans, J.W.M.
- Subjects
Phase-locked loops -- Research ,Discrete-time systems -- Research ,Business ,Computers and office automation industries ,Electronics ,Electronics and electrical industries - Abstract
The stability regions of the first- and second-order discrete-time PLL in the presence of a loop delay are analyzed. The region of the second-order PLL is compared with that of its continuous-time counterpart.
- Published
- 1995
26. Photoplethysmography beat detection and pulse morphology quality assessment for signal reliability estimation
- Author
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Papini, G.B., Fonseca, P., Aubert, X.L., Overeem, S., Bergmans, J.W.M., Vullings, R., Papini, G.B., Fonseca, P., Aubert, X.L., Overeem, S., Bergmans, J.W.M., and Vullings, R.
- Abstract
Contains fulltext : 182367.pdf (publisher's version ) (Closed access), Photoplethysmography (PPG) is one of the key technologies for unobtrusive physiological monitoring, with ongoing attempts to use it in several medical fields, ranging from night to night sleep analysis to continuous cardiac arrhythmia monitoring. However, the PPG signals are susceptible to be corrupted by noise and artifacts, caused, e.g., by limb or sensor movement. These artifacts affect the morphology of PPG waves and prevent the accurate detection and localization of beats and subsequent cardiovascular feature extraction. In this paper a new algorithm for beat detection and pulse quality assessment is described. The algorithm segments the PPG signal in pulses, localizes each beat and grades each segment with a quality index. The obtained index results from a comparison between each pulse and a template derived from the surrounding pulses, by mean of dynamic time warping barycenter averaging. The quality index is used to discard corrupted pulse beats. The algorithm is evaluated by comparing the detected beats with annotated PPG signals and the results are published over the same data. The described method achieves an improved sensitivity and a higher predictive value.
- Published
- 2017
27. Improved ultrasound transducer positioning by fetal heart location estimation during Doppler based heart rate measurements
- Author
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Hamelmann, P., Vullings, R., Schmitt, L., Kolen, A.F., Mischi, M., van Laar, J.O.E.H., Bergmans, J.W.M., Hamelmann, P., Vullings, R., Schmitt, L., Kolen, A.F., Mischi, M., van Laar, J.O.E.H., and Bergmans, J.W.M.
- Abstract
OBJECTIVE: Doppler ultrasound (US) is the most commonly applied method to measure the fetal heart rate (fHR). When the fetal heart is not properly located within the ultrasonic beam, fHR measurements often fail. As a consequence, clinical staff need to reposition the US transducer on the maternal abdomen, which can be a time consuming and tedious task.APPROACH: In this article, a method is presented to aid clinicians with the positioning of the US transducer to produce robust fHR measurements. A maximum likelihood estimation (MLE) algorithm is developed, which provides information on fetal heart location using the power of the Doppler signals received in the individual elements of a standard US transducer for fHR recordings. The performance of the algorithm is evaluated with simulations and in vitro experiments performed on a beating-heart setup.MAIN RESULTS: Both the experiments and the simulations show that the heart location can be accurately determined with an error of less than 7 mm within the measurement volume of the employed US transducer.SIGNIFICANCE: The results show that the developed algorithm can be used to provide accurate feedback on fetal heart location for improved positioning of the US transducer, which may lead to improved measurements of the fHR.
- Published
- 2017
28. Comparing inter beat and inter pulse intervals from ECG and PPG signals
- Author
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Nano, M., Papini, G., Fonseca, P., Vullings, R., Overeem, S., Bergmans, J.W.M., Aarts, R.M., Nano, M., Papini, G., Fonseca, P., Vullings, R., Overeem, S., Bergmans, J.W.M., and Aarts, R.M.
- Published
- 2017
29. Pulse-by-pulse photoplethysmography quality index for signal reliability assessment based on pulse morphology
- Author
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Papini, G., Fonseca, P., Vullings, R., Overeem, S., Bergmans, J.W.M., Papini, G., Fonseca, P., Vullings, R., Overeem, S., and Bergmans, J.W.M.
- Abstract
In the last decades, photoplethysmography (PPG) has been employed in a wide spectrum of applications, ranging from consumer devices to medical equipment. The pulsatile PPG signal recorded contains valuable information on the cardio-vascular and -respiratory system. Several features can be derived from the PPG and these can be used to infer physiological states of the human system, for instance to estimate the sleep structure or the fitness level of a subject [1]. As every sensing technology, the PPG can be corrupted by artifacts so it needs to be enhanced and, sometimes, parts of it have to be rejected. The rejection becomes fundamental especially when features are based on the shape of the signal. In literature, several methods are available to determine a quality index (QI) of parts of the PPG and use this QI as criterion for segment rejection. However, these methods exclude entire segments of the signal rather than single pulses, or they calculate a QI susceptible to the physiological PPG variation. In this study, a new algorithm for single PPG pulse QI calculation is proposed. This QI ranges between 0 and 1 and it is assessed by comparing each pulse with a template. The template is derived from PPG by using dynamic time warping (DTW) barycenter averaging [2]. Each pulse is warped, using DTW, to maximize the match with the template and the QI is calculated as a normalized root mean square error of the remaining mismatch. The QI is resilient to physiological pulse deformations, but still able to quantify the pulse morphology corruption and to recognize artifacts. The algorithm is validated on the Complex System Laboratory database [3], according to the ANSI/AAMI standards. For each pulse the beat location is calculated and it is rejected if QI is lower than 0.5. The positive predictive value and sensitivity (PPV, SEN) are calculated with respect to human beat annotations, with a true positive detection criterion of 30 ms distance from the annotated beat. T
- Published
- 2017
30. A fixed-lag Kalman smoother to filter power line interference in electrocardiogram recordings
- Author
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Warmerdam, G.J.J., Vullings, R., Schmitt, L., van Laar, J.O.E.H., Bergmans, J.W.M., Warmerdam, G.J.J., Vullings, R., Schmitt, L., van Laar, J.O.E.H., and Bergmans, J.W.M.
- Abstract
Objective: Filtering power line interference (PLI) from electrocardiogram (ECG) recordings can lead to significant distortions of the ECG and mask clinically relevant features in ECG waveform morphology. The objective of this study is to filter PLI from ECG recordings with minimal distortion of the ECG waveform. Methods: In this paper, we propose a fixed-lag Kalman smoother with adaptive noise estimation. The performance of this Kalman smoother in filtering PLI is compared to that of a fixed-bandwidth notch filter and several adaptive PLI filters that have been proposed in the literature. To evaluate the performance, we corrupted clean neonatal ECG recordings with various simulated PLI. Furthermore, examples are shown of filtering real PLI from an adult and a fetal ECG recording. Results: The fixed-lag Kalman smoother outperforms other PLI filters in terms of step response settling time (improvements that range from 0.1 to 1 s) and signal-to-noise ratio (improvements that range from 17 to 23 dB). Our fixed-lag Kalman smoother can be used for semi real-time applications with a limited delay of 0.4 s. Conclusion and Significance: The fixed-lag Kalman smoother presented in this study outperforms other methods for filtering PLI and leads to minimal distortion of the ECG waveform.
- Published
- 2017
31. Ultrasound transducer positioning feedback for fetal heart rate monitoring
- Author
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Hamelmann, P.C., Kolen, A., Schmitt, L., Vullings, R., van Assen, H.C., Mischi, M., Demi, L., van Laar, J.O.E.H., Bergmans, J.W.M., Signal Processing Systems, Eindhoven MedTech Innovation Center, and Biomedical Diagnostics Lab
- Published
- 2016
32. Estimating the error in spectral analysis of fetal heart rate variability
- Author
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Warmerdam, G.J.J., Vullings, R., Bergmans, J.W.M., Oei, S.G., Signal Processing Systems, Eindhoven MedTech Innovation Center, and Biomedical Diagnostics Lab
- Subjects
ComputingMilieux_LEGALASPECTSOFCOMPUTING - Published
- 2015
33. Using an injection signal to reduce the effect of capacitance changes in capacitive ECG recordings
- Author
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Serteyn, A.A.M., Vullings, R., Meftah, M., Bergmans, J.W.M., Signal Processing Systems, and Biomedical Diagnostics Lab
- Abstract
Capacitive sensors allows to record the electrocardiogram (ECG) of patients in a more comfortable and unobtrusive manner than the conventional adhesive electrodes; they allow the recording of an ECG through insulating materials, e.g. textiles, and can thus be embedded in everyday objects like beds or car seats. Capacitive ECG sensing however still suffers from motion artifacts. More specifically, any distance change at the body-sensor interface (e.g. due to motion) causes a change of the coupling capacitance, which directly affects the recording. The motion artifact consists of a multiplicative and an additive artefact component. The latter dominates since it is proportional to the DC voltage across the coupling capacitor and often masks the features of interest of the ECG signal. Our on-going work consists in injecting a known signal through the recording system to track and compensate for the changes of the coupling capacitance and therefore reduce the motion artifact. A first method was proposed based-on a single-frequency injection signal. An identification scheme derived from a model of the capacitive sensing system was used to estimate the additive artefact and subtract it from the recording. An alternative method consists in reconstructing the ECG with a filter whose parameters are estimated based on a multi-frequency injection signal. The two proposed methods assume that the body-sensor interface is purely capacitive and that the motion causes a significant capacitance change. Some preliminary tests in simulation and lab environment showed that both methods lead to a significant improvement of the quality of the ECG recordings. The developed methods are currently further evaluated and compared in terms of performance and robustness for different recording scenarios. Motion artifacts due to capacitance changes are not the only interferences corrupting capacitive biopotential recordings. However, a proper understanding and reduction of these artifacts is a first step towards a robust capacitive system enabling unobtrusive ECG recordings on dressed patients at the hospital or at home.
- Published
- 2015
34. Fetal heart rate variability analysis for detection of asphyxia can be improved by including uterine activity information
- Author
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Warmerdam, G.J.J., Vullings, R., van Laar, J.O.E.H., van der Hout-van der Jagt, M.B., Bergmans, J.W.M., Schmitt, L., Oei, S.G., Signal Processing Systems, Eindhoven MedTech Innovation Center, and Biomedical Diagnostics Lab
- Subjects
ComputingMilieux_LEGALASPECTSOFCOMPUTING - Published
- 2015
35. Contactless neonatal ECG and respiration
- Author
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Serteyn, A.A.M., Meftah, M., Vullings, R., Atallah, N.L., Osagiator, A., Schellekens, M., Bambang Oetomo, S., Bergmans, J.W.M., Signal Processing Systems, Biomedical Diagnostics Lab, and Eindhoven MedTech Innovation Center
- Published
- 2015
36. Using uterine activity to improve fetal heart rate variability analysis for detection of asphyxia during labor
- Author
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Warmerdam, G.J.J., Vullings, R., van Laar, Judith O.E.H., van der Hout-van der Jagt, M.B., Bergmans, J.W.M., Schmitt, L., Oei, S.G., Warmerdam, G.J.J., Vullings, R., van Laar, Judith O.E.H., van der Hout-van der Jagt, M.B., Bergmans, J.W.M., Schmitt, L., and Oei, S.G.
- Abstract
During labor, uterine contractions can cause temporary oxygen deficiency for the fetus. In case of severe and prolonged oxygen deficiency this can lead to asphyxia. The currently used technique for detection of asphyxia, cardiotocography (CTG), suffers from a low specificity. Recent studies suggest that analysis of fetal heart rate variability (HRV) in addition to CTG can provide information on fetal distress. However, interpretation of fetal HRV during labor is difficult due to the influence of uterine contractions on fetal HRV. The aim of this study is therefore to investigate whether HRV features differ during contraction and rest periods, and whether these differences can improve the detection of asphyxia. To this end, a case-control study was performed, using 14 cases with asphyxia that were matched with 14 healthy fetuses. We did not find significant differences for individual HRV features when calculated over the fetal heart rate without separating contractions and rest periods (p > 0.30 for all HRV features). Separating contractions from rest periods did result in a significant difference. In particular the ratio between HRV features calculated during and outside contractions can improve discrimination between fetuses with and without asphyxia (p < 0.04 for three out of four ratio HRV features that were studied in this paper).
- Published
- 2016
37. Ultrasound transducer positioning aid for fetal heart rate monitoring
- Author
-
Hamelmann, P.C., Kolen, A., Schmitt, L., Vullings, R., van Assen, H.C., Mischi, M., Demi, L., van Laar, J.O.E.H., Bergmans, J.W.M., Hamelmann, P.C., Kolen, A., Schmitt, L., Vullings, R., van Assen, H.C., Mischi, M., Demi, L., van Laar, J.O.E.H., and Bergmans, J.W.M.
- Abstract
Fetal heart rate (fHR) monitoring is usually performed by Doppler ultrasound (US) techniques. For reliable fHR measurements it is required that the fetal heart is located within the US beam. In clinical practice, clinicians palpate the maternal abdomen to identify the fetal presentation and then the US transducer is fixated on the maternal abdomen where the best fHR signal can be obtained. Finding the optimal transducer position is done by listening to the strength of the Doppler audio output and relying on a signal quality indicator of the cardiotocographic (CTG) measurement system. Due to displacement of the US transducer or displacement of the fetal heart out of the US beam, the fHR signal may be lost. Therefore, it is often necessary that the obstetrician repeats the tedious procedure of US transducer positioning to avoid long periods of fHR signal loss. An intuitive US transducer positioning aid would be highly desirable to increase the work flow for the clinical staff. In this paper, the possibility to determine the fetal heart location with respect to the transducer by exploiting the received signal power in the transducer elements is shown. A commercially available US transducer used for fHR monitoring is connected to an US open platform, which allows individual driving of the elements and raw US data acquisition. Based on the power of the received Doppler signals in the transducer elements, the fetal heart location can be estimated. A beating fetal heart setup was designed and realized for validation. The experimental results show the feasibility of estimating the fetal heart location with the proposed method. This can be used to support clinicians in finding the optimal transducer position for fHR monitoring more easily.
- Published
- 2016
38. Adaptation and Timing Recovery for Two-Dimensional Optical Storage
- Author
-
Immink, A.H.J., Riani, J., Beneden, van, S.J.L, Bergmans, J.W.M., Ciacci, M., Nowbakht, A., Coene, W.M.J., Lee, van der, A.M., Bruls, D.M., Vijaya Kumar, B.V.K., Kobori, H., Signal Processing Systems, and Signal processing for communications
- Subjects
Signal processing ,Computer science ,business.industry ,Distortion ,Computer data storage ,Detector ,Electronic engineering ,Optical storage ,Spiral (railway) ,business ,Optical disc ,Clock recovery - Abstract
This paper discusses several issues related to adaptation and timing recovery for two-dimensional (2D) optical storage. In the TwoDOS format bits are stored on a 2D hexagonal lattice which is formed by recording multiple bit rows with a fixed phase relation in a so-called broad spiral or meta-spiral. Besides a large increase in data rate by reading out with multiple spots, also a density increase by a factor of two compared to Blu-ray Disc is targeted. To increase the storage density, 2D signal processing is proposed including 2D PRML detection in the form of a stripe-wise Viterbi detector. This detector introduces an increasing detection delay when going from the outer rows towards the center of the broad spiral. For fast control loops in a decision-directed mode, special measures are needed to avoid instability due to this delay. Another issue is the large span of the 2D inter-symbol interference at higher densities and tilt, leading to a large 2D equalizer. Furthermore, in case the broad spiral is recorded with a multiple-pass mastering technology (e.g. for ROM TwoDOS discs), write-channel imperfections such as time-varying lattice distortion require independent timing recovery on each row within the broad spiral.
- Published
- 2004
39. Feasibility study on analogue cancellation of local interference in multimode transceivers
- Author
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Habibi, H., Zamanifekri, A., Janssen, E.J.G., Wu, Y., Baltus, P.G.M., Bergmans, J.W.M., Signal Processing Systems, Electromagnetics, Integrated Circuits, Signal processing for communications, and Center for Wireless Technology Eindhoven
- Subjects
Computer Science::Information Theory - Abstract
In multimode transceivers, the transmitter for one communication standard induces a strong local interference in the receiver for another standard. Such strong interference can severely affect the receiver, if it is not suppressed at an early stage of the receiver. A widely explored method to cancel a locally induced interference is to construct its replica, using an analogue model of the interference coupling path, and subtract it from the received signal. Performance of the cancellation method mainly depends on the model accuracy which is limited by the affordable complexity. This paper performs a feasibility study on the application of the cancellation in multimode transceivers based on a simulated scenario. In contrast to previous works, the presented analysis allows an easy comparison between variations of the cancellation method with different complexities. It is found that with a practical complexity the model is not sufficiently accurate. Thus only cancellation in a narrow band is attained. Moreover, the coupling of the local transmitter noise to the local receiver increases. A more accurate model can improve the cancellation; however, it is overly complex for mobile devices. This suggests the requirement for alternative methods to successfully mitigate the local interference.
- Published
- 2014
40. Using an injection signal to reduce the effect of DC voltages and capacitance changes in capacitive biopotential measurements
- Author
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Serteyn, A.A.M., Vullings, R., Meftah, M., Bergmans, J.W.M., Signal Processing Systems, Medical signal processing, and Biomedical Diagnostics Lab
- Subjects
Journal Article - Abstract
only.
- Published
- 2014
41. Contactless Neonatal ECG & Respiration
- Author
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Serteyn, A.A.M., Meftah, M., Vullings, R., Atallah, Nicolas Louis, Osagiator, A., Schellekens, M., Bambang Oetomo, S., Bergmans, J.W.M., Medical signal processing, Signal Processing Systems, Biomedical Diagnostics Lab, and Eindhoven MedTech Innovation Center
- Subjects
ComputingMilieux_LEGALASPECTSOFCOMPUTING - Published
- 2014
42. Motion artifacts in capacitive ECG measurements : reducing the combined effect of DC voltages and capacitance changes using an injection signal
- Author
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Serteyn, A.A.M., Vullings, R., Meftah, M., Bergmans, J.W.M., Serteyn, A.A.M., Vullings, R., Meftah, M., and Bergmans, J.W.M.
- Abstract
Capacitive electrodes are a promising alternative to the conventional adhesive electrodes for ECG measurements. They provide more comfort to the patient when integrated in everyday objects (e.g., beds or seats) for long-term monitoring. However, the application of capacitive sensors is limited by their high sensitivity to motion artifacts. For example, motion at the body–electrode interface causes variations of the coupling capacitance which, in the presence of a dc voltage across the coupling capacitor, create strong artifacts in the measurements. The origin, relevance, and reduction of this specific and important type of artifacts are studied here. An injection signal is exploited to track the variations of the coupling capacitance in real time. This information is then used by an identification scheme to estimate the artifacts and subtract them from the measurements. The method was evaluated in simulations, lab environments, and in a real-life recording on an adult's chest. For the type of artifact under study, a strong artifact reduction ranging from 40 dB for simulated data to 9 dB for a given real-life recording was achieved. The proposed method is automated, does not require any knowledge about the measurement system parameters, and provides an online estimate for the dc voltage across the coupling capacitor.
- Published
- 2015
43. Nonlinear interference suppressor for varying-envelope local interference in multimode transceivers
- Author
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Habibi, H., Janssen, E.J.G., Wu, Yan, Baltus, P.G.M., Bergmans, J.W.M., Pollin, S., Perre, Van der, L., Stas, A., Signal Processing Systems, Integrated Circuits, Signal processing for communications, and Center for Wireless Technology Eindhoven
- Subjects
Computer Science::Information Theory - Abstract
In multimode transceivers, a local transmitter may induce a large interference in a local receiver, often several orders of magnitude stronger than the desired received signal. To suppress this interference by linear filtering, the receiver would need a very large dynamic range, resulting in excessive power consumption. A potentially much more power-efficient approach uses an adaptive memoryless nonlinearity that can strongly suppress the interference when adapted proportional to the envelope of the received interference. This approach has so far been limited to constant-envelope interferences owing to the difficulty of extracting accurate interference envelope information from the received signal. In this paper, we observe that in multimode transceivers the locally available baseband interference enables accurate adaptation for varying-envelope interferences. We identify and analyze nonlinear distortion products which are negligible for constant-envelope interferences. We show that adequate interference suppression can be achieved along with a negligible distortion to the desired signal.
- Published
- 2013
44. Adaptive nonlinear interference suppressor for cognitive radio applications
- Author
-
Habibi, H., Pooh Ling, E., Janssen, E.J.G., Wu, Yan, Milosevic, D., Bergmans, J.W.M., Baltus, P.G.M., Signal Processing Systems, Integrated Circuits, Signal processing for communications, RF, and Center for Wireless Technology Eindhoven
- Abstract
To utilize the radio frequency spectrum efficiently a Cognitive Radio (CR) can operate as a secondary user in a frequency band which is licensed to a primary user. To this end, the CR must sense the spectrum continuously to find empty frequency channels for its transmission. The transmitted signal by the local transmitter of the CR, however, induces a strong local interference in the local receiver of the CR. Hence a half-duplex transceiver is used where the transmit and sense operations are done in separate time slots. The time-slotted operation though, reduces the throughput of the CR. This paper proposes application of an adaptive Nonlinear Interference Suppressor (NIS) to suppress this strong local interference to enable simultaneous transmit and sense. We present experimental results of a transceiver testbed that uses an implementation of the NIS, fabricated in 140 nm CMOS technology. These experiments show that the NIS can substantially suppress the local interference with low complexity and power consumption.
- Published
- 2013
45. Closed-loop adaptation of a nonlinear interference suppressor for local interference in multimode transceivers
- Author
-
Habibi, H., Janssen, E.J.G., Wu, Yan, Baltus, P.G.M., Bergmans, J.W.M., Pollin, S., Perre, Van der, L., Stas, A., Signal Processing Systems, Integrated Circuits, Signal processing for communications, and Center for Wireless Technology Eindhoven
- Subjects
Computer Science::Information Theory - Abstract
In multimode transceivers, the transmitter for one communication standard induces a large interference in the receiver for another standard, exceeding the desired signal by many orders of magnitude. To linearly suppress this interference, the receiver should have a very large linear dynamic range, resulting in excessive power consumption. An adaptive memoryless nonlinearity, which requires an adaptation signal proportional to the envelope of the received interference, can be used to strongly suppress the interference without excessive power consumption. In this paper, we propose to digitally generate the adaptation signal using a model, which describes the adaptation signal in terms of the locally available baseband interference. The model is adapted during the transceiver operation such that the power of the residual interference at the output of the nonlinearity is minimized. Simulation results show that the proposed adaptation method can strongly suppress the interference while a symbol error rate close to that of an exactly linear receiver is achieved.
- Published
- 2013
46. A low-power noise scalable instrumentation amplifier for fetal monitoring systems
- Author
-
Song, S., Rooijakkers, M.J., Bergmans, J.W.M., Cantatore, E., Mischi, M., Rabotti, C., Roermund, van, A.H.M., Integrated Circuits, Signal Processing Systems, Biomedical Diagnostics Lab, and Emerging Technologies
- Published
- 2012
47. Clinical decision support systems for 'Making it easy to do it right'
- Author
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Scheepers-Hoeks, A.M.J.W., Klijn, F.A.J., Linden, van der, C.M.J., Grouls, R.J.E., Ackerman, E.W., Minderman, N., Bergmans, J.W.M., Korsten, H., Chen, W., Bambang Oetomo, S., Feijs, L., Signal Processing Systems, Clinical Informatics, Medical signal processing, and Biomedical Diagnostics Lab
- Subjects
Decision engineering ,Computer science ,media_common.quotation_subject ,Intelligent decision support system ,medicine.disease ,Clinical decision support system ,R-CAST ,Business decision mapping ,Information system ,medicine ,Quality (business) ,Medical emergency ,health care economics and organizations ,Decision analysis ,media_common - Abstract
Medical guidelines and best practises are used in medicine to increase the quality of the health-care delivery system. To support implementation and application of these guidelines, clinical decision support systems (CDSS) have been developed. These systems are defined as ‘Computer-based information systems used to integrate clinical and patient information and provide support for decision-making in patient care’ (MeSH) These are integrated with so-called Electronic Health Records (EHR), which have been developed by companies and National Governmental Institutes, and are used to register and present the patient medical data. The integration of an EHR with CDSS modules will revolutionize the way medicine will be practiced. In pediatrics, as well as geriatrics, such systems might prove to be even more needed. The development, use, and maintenance of CDSS in a hospital are complex and far from trivial. This chapter focuses on several aspects and challenges of EHR’s and CDSS-modules in daily clinical practice in the hospital.
- Published
- 2012
48. Fetal autonomic response to severe acidaemia during labour
- Author
-
Laar, van, J.O.E.H., Peters, C.H.L., Vullings, R., Houterman, S., Bergmans, J.W.M., Oei, S.G., MUMC+: MA AIOS Anesthesiologie (9), Obstetrie & Gynaecologie, RS: GROW - School for Oncology and Reproduction, Signal Processing Systems, Medical signal processing, and Biomedical Diagnostics Lab
- Subjects
Fetal distress ,SDG 3 - Good Health and Well-being ,frequency analysis ,fetal heart rate variability ,spectral analysis - Abstract
Objective Spectral analysis of heart-rate variability is used to monitor autonomic nervous system fluctuations. The low-frequency component is associated with sympathetic and parasympathetic modulation and the high-frequency component is associated with parasympathetic modulation. The objective was to study whether changes in low-frequency or high-frequency power of heart-rate variability occur in case of fetal distress. Design Case-control study. Setting Obstetric unit of a tertiary-care teaching hospital. Population Twenty healthy human fetuses during labour at term of which ten had an umbilical artery pH 7.20 (controls) after birth. Methods Spectral information about fetal beat-to-beat heart rate, calculated from direct fetal electrocardiogram registrations, was obtained by using a short-time Fourier transform. Main outcome measures Absolute power and normalised power in the low-frequency and high-frequency bands. Results No differences were found between fetuses with and without acidaemia in absolute low or high frequency power (P = 0.2 and P = 0.3, respectively). During the last 30 minutes of labour, acidaemic fetuses had significantly increased normalised low-frequency power (P = 0.01) and decreased normalised high-frequency power (P = 0.03) compared with non-acidaemic fetuses. These differences were not observed from 3 to 2 hours before birth (P = 0.7 and P = 0.9, respectively). Conclusion The autonomic nervous system of human fetuses at term responds adequately to severe stress during labour. Normalised low and high frequency power of heart-rate variability might be able to discriminate between normal and abnormal fetal condition.
- Published
- 2010
49. Objective and non-invasive detection of fetal movement
- Author
-
Vullings, R., Peters, C.H.L., Laar, van, J.O.E.H., Bergmans, J.W.M., Oei, S.G., Signal Processing Systems, Medical signal processing, and Biomedical Diagnostics Lab
- Abstract
only
- Published
- 2010
50. Prototyping of a fetal ECG monitoring system
- Author
-
Vullings, R., Peters, C.H.L., Mischi, M., Oei, S.G., Bergmans, J.W.M., Signal Processing Systems, Medical signal processing, and Biomedical Diagnostics Lab
- Subjects
embryonic structures - Abstract
The fetal heart rate (fHR) and fetal electrocardiogram (fECG) are important parameters for diagnosing fetal well-being. Currently, the fECG can only be accurately recorded during labor using an electrode connected directly to the fetal scalp. Another possibility to obtain the fECG is by positioning contact electrodes on the maternal abdomen. The signals recorded by these electrodes are however corrupted by other electrophysiological signals and noise. The maternal electrocardiogram (mECG) is the predominant corruption, which has to be removed to enable detection of the fHR. In this paper a novel technique to remove the mECG from abdominal recordings has been implemented in a prototype fECG monitoring system. Moreover, a novel technique to detect the fHR and subsequently calculate an average fECG complex has been implemented as well. Implementation is performed to enable real-time monitoring of the fHR and fECG. The fHR detected from the maternal abdomen is validated by comparison to the fHR detected by a simultaneously performed recording from the fetal scalp. Preliminary results show a correlation coefficient of 0.98 between the fHR traces.
- Published
- 2010
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