Extraction of foetal ECG that is embedded in the maternal ECG is a challenging problem. This paper presents a combined system to extract foetal ECG from maternal abdominal ECG. The system uses a combination of singular value decomposition (SVD) and a neuro-fuzzy inference system. The SVD is used to construct two reference signals, while the fuzzy system is used as an adaptive canceller. The algorithm is applied on synthetic as well as real data and the results are presented. In addition, the paper presents an example of using the same system as a noise removal tool.
Multiple intraluminal impedance measurement is used to investigate the esophagus condition. This procedure provides information about the esophagus status, reflux occurrence and clearance mechanism. This paper presents finite-element approximation of the forward problem of the catheter inside the esophagus, relating the real data obtained from multiple intraluminal impedance to the solution obtained from the finite-element approximation. Investigation of the effect of the esophagus status on the impedance, and the correlation between various factors that affect the impedance are presented. The results of this paper provide theoretical bases for relating the esophagus condition to the impedance waveforms.
An edge detection-based approach to estimate the order of an autoregressive moving average (ARMA) model process is presented. The proposed method performs edge detection to select the ARMA order by extracting the outlines of a data covariance matrix derived from the observed data sequence. The method is based on the minimum eigenvalue (MEV) criterion developed by Liang et al., IEEE Trans. Signal Process., 41(10): 3003-3009, 1993. The algorithm transforms the MEV covariance matrix into an image by normalizing and resizing the original covariance matrix. Then, a search is performed to locate changes in the intensity function, i.e., pixels where the brightness changes abruptly. Examples are presented to demonstrate the performance of this algorithm.
The measurement of the electrical impedance inside the esophagus provides information about its status, and is being explored in the study of the gastroesophageal reflux. This paper presents theoretical computation of impedance inside the esophagus. The results of the numerical solution for a simple geometry are compared against the solution formulated from the Green's function approach. The effect of the electrode configuration on the resulting impedance is studied as an application of the methodology developed in this paper. The results of this paper will be useful in the design of an intraluminal impedance catheter as well as in the interpretation of the resulting impedance signals.
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