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Biomedical Engineering, IEEE Transactions on

Issue 10 • Date Oct. 1992

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Displaying Results 1 - 12 of 12
  • Estimation of the spatio-temporal correlations of biological electrical sources from their magnetic fields

    Publication Year: 1992 , Page(s): 997 - 1004
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    A general formulation linking the spatial and temporal coherence of measurable magnetic fields with the corresponding spatial and temporal coherence of the inaccessible current sources is derived in the quasi-static model. A method for reconstructing the spatial and temporal coherence of the source distribution is presented. Such coherence maps would be useful descriptors of physiological processes occurring over time and space, and would represent more information than an image of the current sources frozen in time, or even a temporal sequence of such images. View full abstract»

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  • Origin of changes in the epigastric impedance signal as determined by a three-dimensional model

    Publication Year: 1992 , Page(s): 1005 - 1010
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (479 KB)  

    The impedance technique can be used for the noninvasive monitoring of the stomach, with the epigastric impedance signal being a function of the positon and configuration of the electrodes. The changes observed could be due to meal resistivity, meal volume, and contractions of the gastric smooth muscles. The effect of these various factors on the epigastric impedance signal was determined for several electrode configurations using a three-dimensional model of the abdomen. When the voltage sensing electrodes are located close to the current electrodes, the signal varies linearly with meal volume. The relationship between meal resistivity and the epigastric impedance signal is nonlinear. The impedance signal varies linearly with the contractions of the circular smooth muscles of the stomach. View full abstract»

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  • Microwave effects on input resistance and action potential firing of snail neurons

    Publication Year: 1992 , Page(s): 1011 - 1021
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    Effects of microwave (MW) fields (continuous wave, 2.45 GHz, specific absorption rates 12.5 or 125 mW/g) on input resistances and action potential (AP) intervals of neurons in ganglia of snails (Helix aspersa), at 20.9+or-0.1 degrees C were studied. At 12.5 mW/g, input resistance did not change during irradiation, but increased (p<0.05) afterward. At 125 mW/g, input resistance during irradiation was lower than in unirradiated controls. Serial correlograms changed marginally more frequently in MW experiments than in controls, but the changes had no consistent pattern. The AP firing rate was affected by MW, but the direction was not consistent across cells. When AP generation was modeled as being due to a neuronal input current, MW did not affect its mean, standard deviation, or autocorrelation. Unlike MW, temperature changes caused neurons to respond robustly and reversibly. The data suggest that MW may enhance degenerative effects such as metabolic rundown or loss of ion channel patency, but do not indicate a specific mechanism for MW interaction with neurons. View full abstract»

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  • Calculation of Doppler spectral power density functions

    Publication Year: 1992 , Page(s): 1022 - 1031
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (755 KB)  

    A volume integral method for the calculation of Doppler ultrasound spectral power density (SPD) functions is described. Axisymmetric flow in a circular tube with a power law velocity profile is assumed. The SPD function is regarded as a probability density function for scatterer velocity, and the assumptions under which this is justified are considered. It is shown that the SPD function is independent of Doppler angle, except in the presence of wall reflection effects. A coordinate system centered on the beam is used enabling irregularly shaped and nonuniform beams to be treated. For the common flow and beam patterns, which exhibit symmetry, the volume integrals can often be reduced to a single integral and evaluated directly. Results are obtained for uniform rectangular and circular insonating beams, and for nonuniform beams with Gaussian, jinc, and sinc profiles. The effects of narrow beams and wall reflection are shown. The method may be readily applied to more complicated beam and flow patterns. View full abstract»

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  • Adaptive filter for event-related bioelectric signals using an impulse correlated reference input: comparison with signal averaging techniques

    Publication Year: 1992 , Page(s): 1032 - 1044
    Cited by:  Papers (48)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1067 KB)  

    An adaptive impulse correlated filter (AICF) for event-related signals that are time-locked to a stimulus is presented. This filter estimates the deterministic component of the signal and removes the noise uncorrelated with the stimulus, even if this noise is colored, as in the case of evoked potentials. The filter needs two inputs: the signal (primary input) and an impulse correlated with the deterministic component (reference input). The LMS algorithm is used to adjust the weights in the adaptive process. It is shown that the AICF is equivalent to exponentially weighted averaging (FWA) when using the LMS algorithm. A quantitative analysis of the signal-to-noise ratio improvement, convergence, and misadjustment error is presented. A comparison of the AICF with ensemble averaging (EA) and moving window averaging (MWA) techniques is also presented. The adaptive filter is applied to real high-resolution ECG signals and time-varying somatosensory evoked potentials. View full abstract»

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  • A comparative study of simultaneous vibromyography and electromyography with active human quadriceps

    Publication Year: 1992 , Page(s): 1045 - 1052
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (946 KB)  

    Vibromyographic (VMG) signals, which are low-frequency vibration signals generated during muscle contraction, were studied in comparison with electromyographic (EMG) signals recorded simultaneously during isometric contraction of the human quadriceps muscles. It was found that the VMG and EMG under the same conditions on the same muscle group are, in general, equally sensitive to the levels of muscle contraction. Results show that the RMS value of the VMG signal increases linearly, in a manner similar to the EMG RMS/% maximal voluntary contraction (MVC) relationship, with increasing muscle contraction levels. Furthermore, the study indicates that the averaged mean frequency and peak frequency of the VMG signals are much lower than those of the EMG signals. The results also indicate that certain relationships for the VMG signal, like those of the EMG, may reflect muscle activation patterns, while the difference in frequency content between the VMG and the EMG reflects the morphological differences between the mechanical and electrical responses to muscle activation. The signals exhibit a feature of joint angle dependence. View full abstract»

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  • Phase delay of pulmonary acoustic transmission from trachea to chest wall

    Publication Year: 1992 , Page(s): 1053 - 1059
    Cited by:  Papers (4)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (722 KB)  

    The frequency-dependent propagation time, or phase delay tau (f), of sonic noise transmission from the trachea to the chest wall was estimated over the 100-600 Hz frequency range using a phase estimation technique from measurements performed on eight healthy subjects. Since tau (f) can be greater than one period of the input signal at frequencies greater than 100 Hz, the unambiguous phase estimate at 100 Hz was used as a starting point to determine the phase not View full abstract»

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  • Fuzzy control of mean arterial pressure in postsurgical patients with sodium nitroprusside infusion

    Publication Year: 1992 , Page(s): 1060 - 1070
    Cited by:  Papers (26)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (858 KB)  

    A fuzzy control system to provide closed-loop control of mean arterial pressure (MAP) in postsurgical patients in a cardiac surgical intensive care unit setting by regulating sodium nitroprusside (SNP) infusion is discussed. The fuzzy controller, originally expert-system-based, was analytically converted to ten nonfuzzy control algorithms, which reduced execution time dramatically. The core of the control algorithms was a nonlinear proportional-integral (PI) controller whose proportional gain and integral gain adjusted continuously according to error and rate change of error of the process output. The gains become larger when process output was far from desired setpoint and smaller when process output was close to desired setpoint, resulting in more dynamic and stable control performance than the regular PI controller, especially when a linear process with time-delay or a nonlinear process was involved. The control algorithms, encoded in C programming language, were implemented to control MAP in patients. Preliminary clinical results showed that the average percentage of time in which MAP stayed between 90% and 110% of the MAP setpoint was 89.31%, with a standard deviation of 4.96%. These were calculated based on 12 patient trials, with total trial time of 95 and 13 min. View full abstract»

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  • Adaptive control of multiplexed closed-circuit anesthesia

    Publication Year: 1992 , Page(s): 1071 - 1080
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (767 KB)  

    The design of an adaptive closed-circuit anesthesia controller based on a multiplexed mass spectrometer system is described. The controller deals with measurement deterioration caused by measurement delay and rise time through a long catheter as well as long sampling times due to the multiplexed measurements. Measurement data are extrapolated between sampling periods to increase the estimation convergence rate. A multiple-step-ahead predictive control algorithm is used to calculate intermediate control inputs between sampling intervals. Simulations are used to validate the designed controller. View full abstract»

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  • A worst-case optimal parameter selection model of cancer chemotherapy

    Publication Year: 1992 , Page(s): 1081 - 1085
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (426 KB)  

    An optimal parameter selection model of cancer chemotherapy in which two system parameters are unknown is formulated as a worst-case optimal parameter selection model. The model assumes that the unknown parameters lie within a known set. The system constraints must be satisfied over this entire set, and the objective function minimized in the worst case. The continuous dependence of the objective function and the system constraints upon the unknown parameters can be removed, making a numerical solution tractable. For the data considered it is proven that a cure is impossible no matter what the values of the unknown parameters in the parameter set. The optimal policy is shown to be relatively low dose intensity for the majority of the treatment, with remaining drug delivered towards the end of the treatment interval. View full abstract»

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  • Evaluation of microwave and radio frequency catheter ablation in a myocardium-equivalent phantom model

    Publication Year: 1992 , Page(s): 1086 - 1095
    Cited by:  Papers (21)  |  Patents (75)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1097 KB)  

    The use of 2450-MHz microwave energy applied via a miniature coaxial cable-mounted helical coil antenna was investigated as a means to increase the treated volume of cardiac tissue in a saline-perfused, tissue-equivalent manner during ablation. Using an array of fiber-optic temperature probes implanted in a saline-perfused, tissue-equivalent gel phantom model designed to simulate the myocardium during ablation, the heating pattern from the microwave antenna was characterized and compared to that induced by a commercial RF electrode catheter at 550 kHz. Effects of variable contact angle between the heat source and heart wall were assessed. Heating patterns from the RF electrodes dropped off much more abruptly both radially and axially than the microwave antenna. The volume of effectively heated tissue was more than ten times larger for the microwave antenna when the heat sources were well-coupled to the tissue, and more than four times larger for the microwave antenna when the sources were angled 30 degrees away from the tissue surface. View full abstract»

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  • Clinical application of an active electrode using an operational amplifier

    Publication Year: 1992 , Page(s): 1096 - 1099
    Cited by:  Papers (19)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB)  

    An active electrode (d10 mm, t6 mm) that functions as an impedance transformer (with an input impedance >10 G Omega and an output impedance <1 Omega ) by means of which one can derive surface EMG without any skin preparation and paste is presented. This electrode was compared with a conventional one, and it was ascertained that the electrode could replace the conventional one and was preferable because it required less preparation time and was less affected by environmental noise. View full abstract»

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Aims & Scope

IEEE Transactions on Biomedical Engineering contains basic and applied papers dealing with biomedical engineering. Papers range from engineering development in methods and techniques with biomedical applications to experimental and clinical investigations with engineering contributions.

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Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering