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Volume conduction is a major problem in spatial-temporal electroencephalogram (EEG) signals. We propose a frequency dependent subtraction approach to address the volume conduction problem in EEG signals. We validate the proposed approach using simulated data and discuss the application of the approach to the EEG data recorded from three sick infants. The frequency dependent subtraction mitigated the...
Non-invasive recordings of fetal heart and brain have been possible for almost a decade with the advancement in biomagnetic sensors using the SQUID (Superconducting Quantum Interference Device) technology. Techniques such as orthogonal projection and ICA have been applied to attenuate interference from other biological sources such as maternal heart. Successful application of such techniques among...
We propose a novel approach to calculate the conduction velocity (CV) of the uterine contraction bursts in magnetomyogram (MMG) signals measured using a multichannel SQUID array. For this purpose, we partition the sensor coordinates into four different quadrants and identify the contractile bursts using a previously proposed Hilbert-wavelet transform approach. If contractile burst is identified in...
Using a phase plane analysis (PPA) of the spatial spread of trajectories of the fetal heart rate and its time-derivative we characterize the fetal heart rate patterns (fHRP) as defined by Nijhuis. For this purpose, we collect 22 fetal magnetocardiogram using a 151 SQUID system from 22 low-risk fetuses in gestational ages ranging from 30 to 37 weeks. Each study lasted for 30 minutes. After the attenuation...
The fetal magnetoencephalogram (fMEG) is measured in the presence of large interference from maternal and fetal magnetocardiograms (mMCG and fMCG). These cardiac interferences can be attenuated by orthogonal projection (OP) technique of the corresponding spatial vectors. However, the OP technique redistributes the fMEG signal among the channels and also leaves some cardiac residuals (partially attenuated...
We propose a novel approach based on Hilbert phase to identify the burst in the uterine myometrial activity. We apply this approach to 24 serial magnetomyographic signals recorded from four pregnant women using a 151 SQUID array system. The bursts identified with this approach are evaluated for duration and are correlated with the gestational age. In all four subjects, we find a decrease in the duration...
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