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Biomedical Engineering, IEEE Transactions on

Issue 7 • Date July 1990

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Displaying Results 1 - 12 of 12
  • Identifiability analysis and parameter identification of an in vivo ligand-receptor model from PET data

    Publication Year: 1990 , Page(s): 653 - 661
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (901 KB)  

    The identification of the model parameters from data obtained with a single tracer injection leads to disappointing numerical results, since most of the parameters have to be considered as unidentifiable. A protocol including two injections, a first injection of the labeled ligand and a second injection of the cold ligand (displacement experiment), leads to two very different numerical solutions, which is surprising, since such multiplicity of solutions was not indicated by a preliminary theoretical identifiability study. It is shown that a three-injections protocol, including both a displacement and a coinjection experiment, makes it possible to determine which of these two solutions is biologically valid. View full abstract»

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  • Model reference adaptive control with constraints for postoperative blood pressure management

    Publication Year: 1990 , Page(s): 679 - 687
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (782 KB)  

    An approach for adaptive control of blood pressure using sodium nitroprusside is presented. A modified stochastic model reference adaptive control algorithm with a time-varying reference model is developed and used for this purpose. An automatic adjustment of the reference model is proposed in order to optimize the performance of the closed-loop system while meeting clinical constraints imposed on the infusion rate and the mean arterial pressure. Extensive computer simulations show the robustness of the proposed controller in the presence of relatively high noise levels, over the full range of plant parameters and for large parameter variations. View full abstract»

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  • Theoretical basis for controlling minimal tumor temperature during interstitial conductive heat therapy

    Publication Year: 1990 , Page(s): 662 - 672
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1249 KB)  

    A description is given of the simulation of steady-state intratumoral temperatures achieved by a simple modality of local heat therapy: interstitial treatment with parallel arrays of warmed, conductive heating elements. During conductive heating power is directly deposited only in the interstitial probes. Adjacent tissue is warmed by heat conduction. Simulations of interstitial conductive heating involved solution of the bioheat transfer equation on a digital computer using a finite difference model of the treated tissue. The simulations suggest that when the complete temperature distributions for conductive interstitial hyperthermia are examined in detail, substantial uniformity of the temperature distributions is evident. Except for a thin sleeve of tissue surrounding each heating element, a broad, flat central valley of temperature elevation is achieved, with a well-defined minimum temperature, very close to modal and median tissue temperatures. Because probes are inserted directly in tumor tissue, the thin sleeve of overheated tissue would not be expected to cause normal tissue complications. The temperature of the heated probes must be continuously controlled and increased in the face of increased blood flow in order to maintain minimum tumor temperature. View full abstract»

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  • A nonlinear model of the arterial system incorporating a pressure-dependent compliance

    Publication Year: 1990 , Page(s): 673 - 678
    Cited by:  Papers (20)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    An examination is made of the consequences of incorporating a pressure dependent compliance in a modified arterial system model. This nonlinear model is evaluated under control and acute pressure-loading conditions. Results show that the nonlinear compliance model in general can more accurately predict the measured pressure waveforms during control and during acute pressure loading. The difference between the predicted waveforms is more pronounced when blood pressure is high and when the pulse pressure is large. View full abstract»

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  • Point source nerve bundle stimulation: effects of fiber diameter and depth on simulated excitation

    Publication Year: 1990 , Page(s): 688 - 698
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1070 KB)  

    Excitation response of different diameter myelinated nerve fibers situated at various depths within a cylindrical nerve bundle from the applied field of a point source electrode are analytically evaluated. For the potential field calculation, the fiber bundle is considered to be immersed in an infinite isotropic conductive medium and is idealized as an infinitely extending cylinder represented as an anisotropic bidomain (where electrical coupling from interstitial to intracellular space is included). Myelinated nerve fiber excitation is determined from a core-conductive nerve model, whose nodal currents are described by the Frankenhaeuser-Huxley kinetics and the aforementioned field providing the applied potentials. The stimulation level necessary for a nerve fiber to reach threshold is quantified in response to four descriptions of the volume conductor: the isotropic homogeneous case, the monodomain case, the bidomain case, and the modified monodomain case. Model results indicate the importance of a bidomain representation of the nerve bundle and provide insight into the relationship between the physical medium and the physiological properties of nerve fiber excitation. View full abstract»

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  • An improved method for localizing electric brain dipoles

    Publication Year: 1990 , Page(s): 699 - 705
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (657 KB)  

    An improved method for noninvasive localization of equivalent dipoles in the brain is presented and evaluated. The method has been tested and evaluated on humans in vivo. The head is represented by a three-layer spherical model. The potential on any point on the scalp due to any source is found by a closed formula, which is not based on matrix rotations. The formulas will accept any surface electrode as the reference electrode. The least-squares procedure is based on optimal dipoles, reducing the number of unknowns in the iterations from six to three. The method was evaluated by localizing five implanted dipolar sources in the human sensorimotor cortex. The distances between the locations of the sources as calculated by the method and the actual locations were between 0.4 and 2.0 cm. The sensitivity of the method to uncertainties encountered whenever a real head has to be modeled by a three-layer model has also been assessed. View full abstract»

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  • A nerve cuff technique for selective excitation of peripheral nerve trunk regions

    Publication Year: 1990 , Page(s): 706 - 715
    Cited by:  Papers (50)  |  Patents (54)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1045 KB)  

    The numerical modeling and experimental testing of a nerve cuff technique for selective stimulation of superficial peripheral nerve trunk regions are presented. Two basic electrode configurations ('snug' cuff monopolar and tripolar longitudinally aligned dots) have been considered. In addition, the feasibility of steering excitation into superficial nerve trunk regions using subthreshold levels of current flow from an electrode dot located on the opposite side of the nerve has been tested. The modeling objectives were to solve for the electric field that would be generated within a representative nerve trunk by each electrode configuration and to use a simple nerve cable model to predict the effectiveness of each configuration in producing localized excitation. In three acute experiments on cat sciatic nerve the objective was to characterize the effectiveness of each electrode configuration in selectively activating only the medial gastrocnemius muscle. Modeling and experimentation both suggest that longitudinally aligned tripolar dot electrodes on the surface of a nerve trunk, and bounded by a layer of insulation (such as a nerve cuff), will restrict excitation to superficial nerve trunk regions more successfully than will monopolar dot electrodes. Excitation steering will improve the spatial selectivity of monopolar and tripolar electrode configurations. View full abstract»

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  • High-efficiency coupling-insensitive transcutaneous power and data transmission via an inductive link

    Publication Year: 1990 , Page(s): 716 - 722
    Cited by:  Papers (63)  |  Patents (82)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB)  

    A new approach is presented for transmitting RF power and signal via an inductive link. Such an approach optimizes the power efficiency of the overall transmission scheme comprising the power amplifier plus the inductive link. Power amplification is based on the single ended class E concept. The power amplification stage is self-oscillating, and thus the oscillation frequency is influenced by the coupling of the coils. The resulting operating frequency offset yields improved power transmission performance of the circuit, since the oscillation frequency tracks the absolute transmission efficiency maximum. A detailed analysis is given. Realization of the approach requires a minimal number of circuit components. Experimental and theoretical results are in good agreement. View full abstract»

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  • Design for a constant peak current defibrillator

    Publication Year: 1990 , Page(s): 723 - 730
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (619 KB)  

    A damped sine wave defibrillator that is capable of delivering a constant peak discharge current over a wide range of patient thoracic impedance is shown to be theoretically possible. This is realized in practice by the technique of storing an amount of energy above that required for delivery, and dumping the excess charge when the discharge current has reached a predetermined level, the dumping being triggered by a current sensor. A larger than normal inductance assists in swamping the effect of varying impedance and produces a smooth waveform. The preselected peak current can be delivered with a variation of about +or-6% to 95% of a normal patient population. The energy expended in a simulated patient circuit is somewhat lower than for conventional defibrillators. View full abstract»

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  • Automated perimeter for binocular suppression

    Publication Year: 1990 , Page(s): 731 - 734
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (382 KB)  

    Scotomas associated with suppression amblyopia can appear or enlarge under binocular conditions. A device was designed to present an independent light-emitting diode (LED) stimulus array to each eye while both eyes fixate together through beam splitters on a common background pattern. A computer-controlled field screening examination was designed to automatically plot suppression scotomas under binocular conditions. View full abstract»

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  • Rapid assessment of electrode characteristics for impedance imaging

    Publication Year: 1990 , Page(s): 735 - 738
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (425 KB)  

    When a multiplicity of electrodes is applied in one or more rows around a body structure such as the thorax or limb, it is useful to be able to rapidly assess the general status of the electrode-body interface to determine if the skin has been suitably prepared, and that electrode and skin impedance are suitably low. In addition, assessment of the impedance of individual electrodes should precede acquisition of data for image formation. Techniques are presented for assessing the overall skin and electrode impedances relative to the impedance of the body interior and for assessing the integrity of each electrode's contact impedance. Experimental results are given. It was found that the homogeneous saline phantom has negligible skin impedance and negligible reaction impedance. The intact thigh has a high and variable reactive impedance near the skin, which is made more uniform and somewhat lowered by stripping the stratum corneum. After stripping, the real component of skin impedance has approximately half the impedance of the interior structures. View full abstract»

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  • A method for real-time processing to study recovery functions of evoked potentials

    Publication Year: 1990 , Page(s): 738 - 740
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (345 KB)  

    A method for evaluating the recovery function of the evoked potential (EP) in real time is reported. To record the test response of paired stimulation, the responses to alternate presentation of an unpaired stimulus and several kinds of paired stimuli with various interstimulus intervals were averaged, and subtraction was made in real time. The EPs obtained by the proposed method were proved to be accurate even under changing recording conditions. A formula for computing the recovery correlation factor was derived as a measure of the recovery function of the recorded EP, and the recovery curves for three subjects were obtained. 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