System Maintenance:
There may be intermittent impact on performance while updates are in progress. We apologize for the inconvenience.
By Topic

Biomedical Engineering, IEEE Transactions on

Issue 6 • Date June 1991

Filter Results

Displaying Results 1 - 14 of 14
  • A controller for regulation of mean arterial blood pressure using optimum nitroprusside infusion rate

    Publication Year: 1991 , Page(s): 513 - 521
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (675 KB)  

    An integrating self-tuning control strategy for control of mean arterial blood pressure using sodium nitroprusside is presented. Next to robust performance, the most attractive feature of the controller is its capability to optimize the quantity of infused medication without introducing a bias in the blood pressure level, a problem that exists in some of the other adaptive control strategies that have been proposed previously. Further, the controller design requires only the knowledge of the pure delay and the order of the transfer function describing the patient's response to the medication; it does not require that the entire transfer function be specified. The derivation of the controller is not based on the patient response to sodium nitroprusside; indeed, it is a general adaptive control strategy for control of systems with transport delay. The controller performs robustly in the presence of variations in the patient response and successfully controls the pressure at the desired level. The ability of this strategy to reduce the amount of infused medication makes it potentially attractive for use in clinical applications, as large doses or long-term use of sodium nitroprusside can adversely affect central nervous system and hematopoietic tissues. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A simple analytical solution to the three-compartment pharmacokinetic model suitable for computer-controlled infusion pumps

    Publication Year: 1991 , Page(s): 522 - 525
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The disposition of many drugs following an intravenous bolus injection can be described by a biexponential or triexponential equation. Computer-controlled infusion pumps have been developed which dose intravenous drugs based on models of drug disposition. These pumps can maintain steady plasma drug concentrations and facilitate controlled increases and decreases in drug concentration, enhancing titration of intravenous drugs. Several investigators have proposed analytical solutions to the biexponential and triexponential disposition functions for use in computer-controlled infusion pumps. Because of the complexity of these analytical solutions, other investigators have used numerical techniques to approximate the analytical solution. The authors have derived an extremely simple analytical solution to polyexponential disposition functions. This solution simplifies both the prediction of the plasma drug concentration by a computer-controlled infusion pump and the stepwise calculation of the infusion rate required to maintain constant plasma drug concentrations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Model studies of extracellular electrograms arising from an excitation wave propagating in a thin layer

    Publication Year: 1991 , Page(s): 526 - 531
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (561 KB)  

    Extracellular potentials were calculated for a wave of activation propagating through a thin layer of tissue. Sources were represented on the basis of the bidomain model, with the observation point at the tissue surface. Calculated potentials were found to be insensitive to the length of the wavefront if it passed under the recording electrode provided its length exceeded 1 mm, but to decrease rapidly when the wave passed to a side of the electrode. Contributions of source regions with a lateral displacement from the electrode greater than about 0.3 mm were substantially diminished. The effects of the thickness of the layer and velocity of propagation on amplitude were investigated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A nystagmus strategy to linearize the vestibulo-ocular reflex

    Publication Year: 1991 , Page(s): 532 - 543
    Cited by:  Papers (17)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1067 KB)  

    Two important aspects of the vestibulo-ocular reflex (VOR) are addressed. First, the linear range of ocular responses is much more extensive than expected from the characteristics of central pathways (CNS), and this is shown to result directly from early convergence of fast and slow premotor signals in the central processes, associated with significant and intermittent changes in functional connectivity (effective structural modulation). Second, the presence of such structural modulation implies that responses must be analyzed using transient analysis techniques, rather than previous steady state approaches, in order to properly evaluate reflex dynamics. Simulation results with a recent model of the VOR are used to illustrate the arguments. Relying on known interconnections between saccadic burst circuits in the brainstem, and the ocular premotor areas of the vestibular nuclei, a viable strategy for the timing of nystagmus events is proposed. The strategy easily reproduces the characteristic changes in vestibular nystagmus with the amplitude of head velocities, and with the frequency of passive head oscillation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The estimation of tube wall compliance using acoustic input impedance

    Publication Year: 1991 , Page(s): 544 - 550
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (539 KB)  

    An acoustic-electric analog and transmission line theory have been used to examine acoustic wave propagation in a tube with a compliant wall. The input impedance (i.e. input pressure-flow) has been simulated using a distributed element model. A relative minimum and maximum, denoted by f r and f 2, respectively, that are independent of tube length have been identified theoretically and confirmed experimentally from input impedance measurements on a compliant tube. A method has been devised which uses measured values of f f and f 2 to deduce the tube wall properties from the theoretical model. This method has been validated on a tube with known wall properties determined using standard methods. In practice, the input impedance is measured through a short section of rigid connecting pipe. In this case f r remains constant while f 2 is reduced. This reduction can be accounted for by the volume compliance of the gas within the lumen of the rigid pipe. The theory could have useful applications such as estimating the wall properties of the airways from noninvasive measurements made through the mouth. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A simple electrical-mechanical model of the heart applied to the study of electrical-mechanical alternans

    Publication Year: 1991 , Page(s): 551 - 560
    Cited by:  Papers (2)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    Recent evidence has shown that a subtle alternation in the surface ECG (electrical alternans) may be correlated with the susceptibility to ventricular fibrillation. In the present work, the author presents evidence that a mechanical alternation in the heartbeat (mechanical alternans) generally accompanies electrical alternans. A simple finite-element computer model which emulates both the electrical and the mechanical activity of the heart is presented. A pilot animal study is also reported. The computer model and the animal study both found that (1) there exists a regime of combined electrical-mechanical alternans during the transition from a normal rhythm towards a fibrillatory rhythm, (2) the detected degree of alternation is correlated with the relative instability of the rhythm, and (3) the electrical and mechanical alternans may result from a dispersion in local electrical properties leading to a spatial-temporal alternation in the electrical conduction process. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A comparison of four new time-domain techniques for discriminating monomorphic ventricular tachycardia from sinus rhythm using ventricular waveform morphology

    Publication Year: 1991 , Page(s): 561 - 570
    Cited by:  Papers (36)  |  Patents (40)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (879 KB)  

    The authors have designed four new computationally efficient time-domain algorithms for distinguishing ventricular electrograms during monomorphic ventricular tachycardia (VT) from those during sinus rhythm using direct analysis of the ventricular electrogram morphology. All four techniques are independent of amplitude fluctuations and three of the four are independent of baseline changes. These new techniques were compared to correlation waveform analysis, a previously proposed method for distinction of VT from sinus rhythm. Evaluation of these four new algorithms was performed on data from 19 consecutive patients with 31 distinct monomorphic ventricular tachycardia morphologies. Three of the algorithms performed as well as or better than correlation waveform analysis but with one-tenth to one-half the computational demands. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Alignment methods for averaging of high-resolution cardiac signals: a comparative study of performance

    Publication Year: 1991 , Page(s): 571 - 579
    Cited by:  Papers (35)  |  Patents (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (701 KB)  

    A comparative study of the performance of three alignment methods (the double-level method, a new time-delay estimation method based on normalized integrals, and matched filtering) is presented. A real signal and additive random noise for several signal-to-noise ratios (SNRs) are selected to make an ensemble of computer-simulated beats. The relation between the standard deviation of temporal misalignment versus SNR is discussed. A second study with real ECG signals is also presented. Several morphologies of QRS and P waves are tested. The results are in agreement with the computer simulation study. Nevertheless, the power spectrum of the noise process can affect the results. Matched filter estimation has been tested in the presence of power line interferences (50 Hz), with poor results. An application of the three alignment methods as a function of the SNR is proposed. The new time-delay estimation method has been observed to be robust, even in the presence of nonwhite noise. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Statistical analysis of collagen alignment in ligaments by scale-space analysis

    Publication Year: 1991 , Page(s): 580 - 588
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (846 KB)  

    The authors propose a computational technique for statistical analysis of collagen alignment in ligament images using the scale-space approach. In this method, a ligament image is preprocessed by a sequence of filters which are second derivatives of two-dimensional Gaussian functions with different scales. This gives a set of zero-crossing maps (the scale space) from which a stability map is generated. Significant linear patterns are captured by analyzing the stability map. The directional information in terms of orientation distributions of the collagen fibrils in the image and the area covered by the fibrils in specific directions is extracted for statistical analysis. Examples illustrating the performance of this method with scanning electron microscope images of the collagen fibrils in healing rabbit medial collateral ligaments are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modern spectral analysis techniques for blood flow velocity and spectral measurements with pulsed Doppler ultrasound

    Publication Year: 1991 , Page(s): 589 - 596
    Cited by:  Papers (23)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (737 KB)  

    Four spectral analysis techniques were applied to pulsed Doppler ultrasonic quadrature signals to compare the relative merits of each technique for estimation of flow velocity and Doppler spectra. The four techniques were (1) the fast Fourier transform method, (2) the maximum likelihood method, (3) the Burg autoregressive algorithm, and (4) the modified covariance approach to autoregressive modeling. Both simulated signals and signals obtained from an in vitro flow system were studied. Optimal parameter values (e.g. model orders) were determined for each method, and the effects of signal-to-noise ratio and signal bandwidth were investigated. The modern spectral analysis techniques were shown to be superior to Fourier techniques in most circumstances, provided the model order was chosen appropriately. Robustness considerations tended to recommend the maximum likelihood method for both velocity and spectral estimation. Despite the restrictions of steady laminar flow, the results provide important basic information concerning the applicability of modern spectral analysis techniques to Doppler ultrasonic evaluation of arterial disease. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mean-square error due to gradiometer field measuring devices

    Publication Year: 1991 , Page(s): 597 - 601
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (331 KB)  

    It is pointed out that unless the gradiometer baseline is at least several times the source depth significant error will result from any attempt at detailed analysis of the magnetic fields arising from current sources of interest. Although many investigators have been impressed with the effectiveness of spatial mode rejection, the data collected have been in many cases severely distorted. Attempts to correct these errors through decorrelation using the inverse transform of 1/T( alpha , beta ) will not be possible because its inverse does not exist, and because it is a highpass function its use in an inverse transform technique will emphasize high spatial frequency noise components. It is concluded that the goals of a design for a facility for measuring biomagnetic fields should be an effective shielded room and a field detector employing a first-order gradiometer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Servo-controlled indenter for determining the transverse stiffness of ventricular muscle

    Publication Year: 1991 , Page(s): 602 - 607
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (541 KB)  

    A dynamic indentation system has been developed that can determine transverse stiffness of ventricular muscle in as little as 10 ms, allowing estimation of wall stress over a single contraction cycle. The apparatus consists of an indentation probe coupled to a linear motor. This indentation system was tested on two beating canine ventricular septa that were mounted in a biaxial system that could apply strains in the plane of the septa and measure the resulting in-plane stresses. The probe indented the septa with peak displacements of 0.1-0.5 mm at frequencies of 20 and 50 Hz. The transverse stiffness was calculated as the slope of the relation between the indentation stress and the indentation strain during each high-frequency indentation. Consistent with earlier studies, the transverse stiffness was related to the in-plane stress. In contrast to earlier studies, however, these dynamic transverse stiffness determinations could be made during a single contraction. Thus, dynamic transverse stiffness determinations allow estimation of wall stress in the isolated septa by minimal surface contact, and may lead to methods for estimating wall stress in the intact heart. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A programmable data acquisition and control system for magnetic resonance imaging: application to mutually coupled surface coil arrays and temperature monitoring

    Publication Year: 1991 , Page(s): 608 - 613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (567 KB)  

    A programmable data acquisition and control system was developed for use in conjunction with magnetic resonance imaging (MRI). The controller consists of two functional blocks: a host system and a remote system. The remote system resides inside the shielded room housing the magnet. The host, an IBM compatible personal computer, is located at the technician's console. Communication between these devices is implemented over a fiber optic RS-232 data link. This configuration allows experiments to be performed remotely by using a series of keyboard typed commands, by programming the remote system. As an example of its capabilities, the controller was used to tune and match arrays of receiver coils for localized imaging and to record the rectal temperature of a sedated rat during image acquisition. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An active feedback system for isotonic studies of smooth muscle

    Publication Year: 1991 , Page(s): 614 - 616
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    A feedback system used to perform isotonic studies of smooth muscle is presented. This system is capable of applying a constant force to muscle samples regardless of their contractile activities. The force applied to the tissue is controlled using a proportional integral control system that drives a linear motor. The device is integrated into a sucrose gap tissue bath apparatus where measurements of displacement and electrical activity are also possible. The frequency of canine colonic smooth-muscle electrical oscillations was found to be positively related to applied force. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering