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Biomedical Engineering, IEEE Transactions on

Issue 4 • Date April 1992

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Displaying Results 1 - 14 of 14
  • Neural-network-based adaptive matched filtering for QRS detection

    Publication Year: 1992 , Page(s): 317 - 329
    Cited by:  Papers (73)  |  Patents (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    The authors have developed an adaptive matched filtering algorithm based upon an artificial neural network (ANN) for QRS detection. They use an ANN adaptive whitening filter to model the lower frequencies of the electrocardiogram (ECG) which are inherently nonlinear and nonstationary. The residual signal which contains mostly higher frequency QRS complex energy is then passed through a linear matched filter to detect the location of the QRS complex. The authors developed an algorithm to adaptively update the matched filter template from the detected QRS complex in the ECG signal itself so that the template can be customized to an individual subject. This ANN whitening filter is very effective at removing the time-varying, nonlinear noise characteristic of ECG signals. The detection rate for a very noisy patient record in the MIT/BIH arrhythmia database is 99.5% with this approach, which compares favorably to the 97.5% obtained using a linear adaptive whitening filter and the 96.5% achieved with a bandpass filtering method. View full abstract»

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  • Data compression of ECG's by high-degree polynomial approximation

    Publication Year: 1992 , Page(s): 330 - 337
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (625 KB)  

    A method for the compression of ECG (electrocardiogram) data is presented. The method is based on high-degree polynomial expansions. Data rules of about 350 b/s are achievable at an acceptable signal quality. The high compression is obtained by a carefully selected subdivision of the ECG signal into intervals that make optimal use of the special properties of the polynomial base functions. Each interval corresponds to one ECG period. The method is compared to the discrete cosine transform and is found to yield a significantly higher data compression for a given signal quality (quantified by mean squared error and peak error). View full abstract»

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  • Weighted averaging of evoked potentials

    Publication Year: 1992 , Page(s): 338 - 345
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (675 KB)  

    Weighted averages of brain evoked potentials (EPs) are obtained by weighting each single EP sweep prior to averaging. These weights are shown to maximize the signal-to-noise ratio (SNR) of the resulting average if they satisfy a generalized eigenvalue problem involving the correlation matrices of the underlying signal and noise components. The signal and noise correlation matrices are difficult to estimate and the solution of the generalized eigenvalue problem is often computationally impractical for real-time processing. Correspondingly, a number of simplifying assumptions about the signal and noise correlation matrices are made which allow an efficient method of approximating the maximum SNR weights. Experimental results are given using actual auditory EP data which demonstrate that the resulting weighted average has estimated SNRs that are up to 21% greater than the conventional ensemble average SNR. View full abstract»

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  • Probabilistic inference-based classification applied to myoelectric signal decomposition

    Publication Year: 1992 , Page(s): 346 - 355
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (965 KB)  

    A probabilistic inference-based classification (IBC) technique for classifying motor unit action potentials (MUAPs) is presented. This technique discovers statistically significant relationships in the data and uses them to generate classification rules. The technique was applied to the classification of MUAPs extracted from simulated myoelectric signals. Its performance was compared to that of classical template-based classification algorithms (TBC). It was found that the IBC-based technique performed significantly better than the TBC algorithms. As the size of the training set was reduced or as increasing numbers of random classification errors were introduced into the training data, the performance of the IBC and TBC techniques declined similarly. IBC performance remained superior until very small training sets or training sets with large numbers of errors were used. Because the technique can utilize nominal data it has the potential to use declarative problem domain knowledge, which conceivably could improve its performance. View full abstract»

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  • Goodness-of-fit and local identifiability of a receptor-binding radio-pharmacokinetic system

    Publication Year: 1992 , Page(s): 356 - 367
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (982 KB)  

    A four-state nonlinear model describing a radiopharmacokinetic system for a hepatic receptor-binding radiopharmaceutical, ( 99mTc)-galactosyl-neoglycoalbumin, (TcNGA), was tested for goodness-of-fit and local identifiability using scanning data from nine healthy subjects and seven patients with severe liver disease. Based on standard deviations of liver and heart imaging data at equilibria as a measure of observational error, the reduced chi-square ranged from 0.5 to 2.6. Values above 1.2 occurred when the subject moved during the 30 min study. Relative standard errors for each parameter were determined. The highest standard errors occurred when the amount of TcNGA injected exceeded the total amount of receptor. Therefore, when TcNGA functional imaging was performed without excess patient motion and receptor saturation, the kinetic model provided data fits of low systematic error and yielded high precision estimates of receptor concentration and forward binding rate constant. View full abstract»

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  • Nonlinear joint angle control for artificially stimulated muscle

    Publication Year: 1992 , Page(s): 368 - 380
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1115 KB)  

    Designs of both open- and closed-loop controllers of electrically stimulated muscle that explicitly depend on a nonlinear mathematical model of muscle input-output properties are presented and evaluated. The muscle model consists of three factors: a muscle activation dynamics factor, an angle-torque relationship factor, and an angular velocity torque relationship factor. These factors are multiplied to relate output torque to input simulation and joint angle. An experimental method for the determination of the parameters of this model was designed, implemented, and evaluated. An open-loop nonlinear compensator, based upon this model, was tested in an animal model. Its performance in the control of joint angle in the presence of a known load was compared with a PID (proportional-integral-derivative) controller, and with a combination of the PID controller and the nonlinear compensator. The results are presented. View full abstract»

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  • Improved safety and efficacy in adaptive control of arterial blood pressure through the use of a supervisor

    Publication Year: 1992 , Page(s): 381 - 388
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (735 KB)  

    A dual approach to adaptive control of arterial blood pressure using sodium nitroprusside is presented. In the clinical environment, a controller must be aggressive to achieve specific step response characteristics (less than 10 min setting time, less than 10 mm Hg overshoot), yet conservative enough to prevent overreactions to large disturbances, which are common in both the operating room and the intensive care unit. These mutually exclusive requirements make it difficult to design a closed-loop controller for this environment. To prevent possible overreactions while maintaining proper step response, an aggressive adaptive controller has been designed to achieve the desired step response, and a supervisor has been designed around the adaptive controller to limit potential overreactions in the presence of disturbances. Simulations and dog experiments demonstrate the potential for increased safety and efficacy using this dual approach to the control of a complex physiological system. View full abstract»

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  • Supervisory adaptive control of arterial pressure during cardiac surgery

    Publication Year: 1992 , Page(s): 389 - 393
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    A supervisory adaptive controller has been designed for the closed-loop control of mean arterial pressure during cardiac surgery, using sodium nitroprusside. This controller consists of a pole-placement and proportional-plus-integral feedback regulator, multiple-model adaptation, and a supervisor. The pole-placement and proportional-plus-integral regulator was designed to meet aggressive step response characteristics. Multiple-model adaptation was chosen to ensure rapid and stable adjustments for changes in key patient parameters. The supervisor was designed to provide safety and efficacy of control during disturbances that are common during cardiac surgery. The authors studied the ability of this supervisory adaptive controller to regulate arterial pressure during cardiac surgery on nineteen patients. The controller, through the action of the supervisor, detected and responded appropriately to the great majority of disturbances. This study demonstrated that supervisory adaptive control has the potential to provide clinically acceptable regulation, of arterial pressure. View full abstract»

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  • An optimal controller for an electric ventricular-assist device: Theory, implementation, and testing

    Publication Year: 1992 , Page(s): 394 - 403
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (841 KB)  

    The authors address the development and testing of an optimal position feedback controller for the Penn State electric ventricular-assist device (EVAD). The control law is designed to minimize the expected value of the EVAD's power consumption for a targeted patient population. The closed-loop control law is implemented on an Intel 8096 microprocessor, and in vitro test runs show that this controller improves the EVAD's efficiency by 15-21% compared with the performance of the currently used feedforward control scheme. View full abstract»

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  • Temporal relationship between left ventricular and arterial system elastances

    Publication Year: 1992 , Page(s): 404 - 410
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (643 KB)  

    The authors investigated the temporal relationship of arterial compliance to ventricular elastance of the left ventricle (E lv(t)) in five open-chest anesthetized dogs, where simultaneous aortic pressure and flow and left-ventricular pressure were measured. E lv(t) was derived using an elastance-resistance model of the left ventricle. The nonlinear pressure-dependent compliance (C(P)) of the arterial system was incorporated in a three-element Windkessel model and determined by accurate prediction of aortic pressure from aortic flow. The resulting arterial elastance E as(t) was computed as E as(t)=1/C(P). Results show that E as(t) reaches a minimum value at or near the start of ventricular ejection and attains its peak value at or near the time that maximum left ventricular elastance is reached, at end-systole. Numerical simulation of the model demonstrates its ability to adequately reproduce measured pressure and flow. Thus, the arterial system, in terms of elastance, is dynamically and temporally coupled to the left-ventricle during ejection. View full abstract»

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  • Electrical impedance of layered atherosclerotic plaques on human aortas

    Publication Year: 1992 , Page(s): 411 - 419
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1116 KB)  

    Electrical impedance measurements were performed on 13 atherosclerotic human aortic segments at 67 measuring spots in order to determine whether or not on the basis of these data a distinction can be made between atherosclerotic lesions and normal tissue. The experimental results show that the apparent resistivity of an atherosclerotic spot does not necessarily deviate much from the resistivity of normal tissue. This is clarified by histology, which shows that the majority of lesions have a surface layer of connective, fibrous tissue having similar conducting properties to the normal arterial wall. A physical model of an atherosclerotic lesion is presented and compared with the data. Both experimental data and theoretical considerations lead to the conclusion that only when the superficial fibrous layer is absent or very thin in relation to the size of the measuring electrode is the measured resistivity at a lesion much higher than at normal spots. View full abstract»

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  • Instantaneous characterization of time varying nonlinear systems (neurophysiological responses)

    Publication Year: 1992 , Page(s): 420 - 424
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (506 KB)  

    A nonlinear system may be characterized by an orthogonal functional power series (FPS) computed from cross correlations between input and output variables. 'Is the response changing over the course of the experiment?' is a fundamental question encountered in the analysis of both FPS and evoked potentials (EPs). Regression on closed-form functions of time produces a time-varying FPS or EP. Evaluation of these functions at a specified time point produces a system characterization for that instant. View full abstract»

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  • A model of safe levels for electrical stimulation

    Publication Year: 1992 , Page(s): 424 - 426
    Cited by:  Papers (25)  |  Patents (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (299 KB)  

    A model that represents a large body of data on safety and damage levels of electrical stimulation is presented. The predictions of the model are consistent with known principals of current flow and known mechanisms of damage around stimulating electrodes. It is proposed that limits on levels of electrical stimulation take into account the location of the electrode relative to the stimulated tissue; these limits can be computed algorithmically from the model. View full abstract»

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  • Microcomputer-based portable long-term spasticity recording system

    Publication Year: 1992 , Page(s): 426 - 431
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    A device for long-term monitoring of muscle activity (EMG) with surface electrodes and the method of its application are described. This device is called a microcomputer two-channel EMG monitor. The device can be used for up to 24-h monitoring of EMG activity, followed by data transfer to a host computer, for signal analysis. This device records amplified, rectified, and integrated EMG activity. Shorter recording time allows shorter sampling periods suitable for other EMG analysis. Recording of spontaneous EMG in complete spinal cord injured subjects was the original reason for the design of the long-term monitor. These recordings were used for estimation of spasticity in complete spinal cord patients. 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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Editor-in-Chief
Bin He
Department of Biomedical Engineering