IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Mar 2003
Comparative StudyA fast and reliable technique for muscle activity detection from surface EMG signals.
The estimation of on-off timing of human skeletal muscles during movement is an important issue in surface electromyography (EMG) signal processing with relevant clinical applications. In this paper, a novel approach to address this issue is proposed. The method is based on the identification of single motor unit action potentials from the surface EMG signal with the use of the continuous wavelet transform. ⋯ The resultant bias of the onset estimate is lower than 40 ms and the standard deviation lower than 30 ms in case of additive colored Gaussian noise with signal-to-noise ratio as low as 2 dB. Comparison with previously developed methods was performed, and representative applications to experimental signals are presented. The method is designed for a complete real-time implementation and, thus, may be applied in clinical routine activity.
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The capability for multisite stimulation is one of the biggest potential advantages of microelectrode arrays (MEAs). There remain, however, several technical problems which have hindered the development of a practical stimulation system. An important design goal is to allow programmable multisite stimulation, which produces minimal interference with simultaneous extracellular and patch or whole cell clamp recording. ⋯ In addition, the vibration-free solid-state switching made it possible to record whole-cell synaptic currents in one neuron, evoked from multiple sites in the network. We have used this system to visualize spatial propagation patterns of evoked responses in cultured networks of cortical neurons. This MEA-based stimulation system is a useful tool for studying neuronal signal processing in biological neuronal networks, as well as the process of synaptic integration within single neurons.
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IEEE Trans Biomed Eng · Dec 2002
Comparative StudyFlow-rate measurements and models for colloid and crystalloid flows in central and peripheral venous line infusion systems.
The resuscitation fluids, including crystalloids and colloids, were tested in an experimental module with 16-gauge central and peripheral catheters. Infusion pressures were ranged from the gravity driving 10 kPa (75 mmHg) to the pressurized driving 50 kPa (375 mmHg). The experiment results were correlated to obtain the empirical friction factors and the loss factors for the components commonly used in a fluid resuscitation system. ⋯ The modified Bernoulli equation is, therefore, applicable to evaluate the pressure-flow relationship for efficient fluid resuscitations. The coefficients of flow (F) and the square of flow (F2) for the binominal model are varied with the changes of geometry and size of the infusion components, fluid properties and the units of parameters. These coefficients for the fluids and catheters tested in this study were also listed for reference.
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IEEE Trans Biomed Eng · Dec 2002
Rigorous Green's function formulation for transmembrane potential induced along a 3-D infinite cylindrical cell.
The quasi-static electromagnetic field interaction with three-dimensional infinite-cylindrical cell is investigated for both intracellular (IPS) and extracellular (EPS) current point-source excitation. The induced transmembrane potential (TMP), expressed conventionally via Green's function, may alternatively be expanded into a faster-converging representation using a complex contour integration, consisting of an infinite-discrete set of exponentially decaying oscillating modes (corresponding to complex eigenvalues) and a continuous source-mode convolution integral. The dominant contributions for both the IPS and EPS problems are obtained in simple closed-form expressions, including well documented special mathematical functions. ⋯ Only for shorter EPS distance should the cable equation solution (i.e., the order zero dominant mode) be included in addition to the modes of order one. For on-membrane EPS location, additional modes should be included as well. In view of our EPS result, we suggest that the cable equation modeling existing in the literature and related to functional electrical stimulation for EPS problems, should be critically reviewed and corrected.
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IEEE Trans Biomed Eng · Dec 2002
Clinical Trial Controlled Clinical TrialAutomated detection and elimination of periodic ECG artifacts in EEG using the energy interval histogram method.
An automated method for electrocardiogram (ECG)-artifact detection and elimination is proposed for application to a single-channel electroencephalogram (EEG) without a separate ECG channel for reference. The method is based on three characteristics of ECG artifacts: the spike-like property, the periodicity and the lack of correlation with the EEG. The method involves a two-step process: ECG artifact detection using the energy interval histogram (EIH) method and ECG artifact elimination using a modification of ensemble average subtraction. ⋯ As a postprocessing step, we used two types of threshold adjusting algorithms that were based on the periodicity of the ECG R-peaks. The technique was applied to four whole-night sleep EEG recordings from four subjects with severe obstructive sleep apnea syndrome, from which a total of 132878 heartbeats were monitored over 31.8 h. We found that ECG artifacts were successfully detected and eliminated with FP = 0.017 and FN = 0.074 for the epochs where the elimination process is necessarily required.