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Biomedical Engineering, IEEE Transactions on

Issue 10 • Date Oct. 1991

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Displaying Results 1 - 14 of 14
  • A 16-channel 8-parameter waveform electrotactile stimulation system

    Page(s): 933 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (985 KB)  

    A general-purpose electrotactile (electrocutaneous) stimulation system has been developed as a research tool for studying psychophysiological performance associated with various stimulation waveforms. An experimenter-defined command file specifies the stimulation current and waveform of each of the 16 channels. The system provides a burst onset delay of 0-20 ms, a phase current of 0-50 mA, an interphase interval of 0-1000 mu s, 1-100 pulses per burst, a pulse repetition rate of 0.1-25 kHz, a phase width of 2-1000 mu s, and functionally monophasic pulses (with zero DC current) or balanced-biphasic pulses (with equal positive and negative phases). The system automatically delivers the desired stimulation, prompts the subject for responses, and then logs subject responses. Key features of the system are (1) the very flexible choice of bursts of pulsatile waveforms, (2) the real-time control of all of the waveform parameters as mathematical functions of external analog inputs, and (3) the high-performance electrode-driver circuitry. View full abstract»

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  • Peripheral vision lipreading aid

    Page(s): 944 - 952
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (858 KB)  

    A pair of eyeglasses with a commercially available two-dimensional red LED array (5*7), and its associated electronics was developed. The display is visible only to the wearer, and is located in the temporal field and the horizontal meridian of the right eye. Selected speech features were encoded as visual patterns for presentation to the lipreader. These features of the speech signal (the fundamental frequency of the speech, high-frequency energy, and low-passed speech signal or total energy envelope) were presented with the objective of providing information about voicing and plosion/frication. Experiments demonstrate the capability of the peripheral display in conveying speech information. Presenting vowel-consonant-vowel syllables, the performance was in excess of 76% with aided lipreading as compared to 41% by lipreading only. View full abstract»

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  • Control of end-point forces of a multijoint limb by functional neuromuscular stimulation

    Page(s): 953 - 965
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    A multivariable feedback controller was designed and tested for regulating the magnitude and orientation of the force vector at the end point of a multijoint limb in contact with an isometric load. The force vector was produced by electrical stimulation of muscles. Two coupling issues must be dealt with by the control system. First, there is a geometric coupling between the end-point force vector and joint torques on which amplitude and orientation of the force vector depend. Second, torques at two joints may be coupled due to activation of muscles that cross them (biarticular coupling). To eliminate the geometric coupling, a transformation of controller error from the Cartesian space to the joint space was employed. A multivariable proportional-plus-integral (PI) control law was used to calculate muscle activation based on the transformed controller error. Centralized and decentralized controls were investigated for decoupling the effects of biarticular muscles. Test results show that the magnitude and orientation of end-point forces could be regulated by this controller. View full abstract»

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  • Tunable diode laser spectroscopy for isotope analysis-detection of isotopic carbon monoxide in exhaled breath

    Page(s): 966 - 973
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    A high resolution tunable infrared diode laser spectroscopy system was developed for isotope analysis with sensitivity at parts per billion levels. Such a system is ideally suited for detection and measurement of minute amounts of infrared active compounds present in a huge noninfrared active background such as air. The operation and capabilities of the system were demonstrated by measuring physiological levels of isotopic carbon monoxide, 12C 16O and 13C 16O, naturally present in exhaled human breath with essentially no sample preparation. The simplicity in obtaining such data suggests that fundamental physiological information may be derived from noninvasive measurements. This makes the system potentially useful for many biomedical applications. View full abstract»

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  • Development of medical pressure and temperature sensors employing optical spectrum modulation

    Page(s): 974 - 981
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    Fiber optic Fabry-Perot sensors have been developed whose optical reflectance varies with optical cavity depth (pressure) or with change in a material's refractive index (temperature). These sensors employ a unique combination of features: they are interrogated by an LED; they are designed to operate within a single reflectance cycle; and their returned light is analyzed by a dichroic ratio technique. The sensors use a step index glass fiber and are relatively insensitive to absolute light levels and fiber bending. They have an expanded linear operating range and can be built for low cost disposable applications. Sensor performance meets or exceeds established medical requirements. View full abstract»

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  • Computer simulations of activation in an anatomically based model of the human ventricular conduction system

    Page(s): 982 - 996
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    Simulations of the electrical activity during excitation were performed in an anatomically based model of the human ventricular conduction system. Each of the 33000 elements of this model represented a unit bundle of Purkinje or atrioventricular nodal tissue. The Ebihara-Johnson model for sodium defined the active membrane characteristics. Using a combination of new and existing modeling techniques, simulations of excitation were completed in approximately 5 min CPU time on an IBM 3090 at the Cornell National Supercomputer Facility. Activation times at sites in the model were compared to experimental measurements for the excitation of the ventricular myocardium on the endocardial surface. After the times were scaled to adjust for conduction velocity and ventricular latency effects, the match between simulation and experimentally obtained times was good. View full abstract»

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  • Structural complexity effects on transverse propagation in a two-dimensional model of myocardium

    Page(s): 997 - 1009
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    A thin sheet of cardiac tissue was modeled as a set of resistively coupled excitable cables with membrane dynamics described by the modified Beeler Reuter model. Transverse connections have a resistance R n and are regularly distributed with a spacing Delta on any given cable, to provide alternating input and output junctions. Flat wave longitudinal propagation corresponds to propagation along a single continuous cable since all units of the network are functionally isolated due to the absence of transverse current flow. Overall, the behavior of the network model is in good agreement with available structural and electrophysiological data on myocardium. The network topology allows parameters governing propagation to be addressed more easily and avoids very large and computationally costly matrices. View full abstract»

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  • Impedance analysis applicable to cardiac muscle and smooth muscle bundles

    Page(s): 1010 - 1022
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    An electrical equivalent circuit was constructed to represent a chain of five myocardial cells in a cardiac muscle bundle with various degrees of cell-to-cell coupling, and an impedance analysis was performed. The impedance across the entire network was measured at frequencies ranging from 10 1 to 10 6 Hz. The total tissue resistivity (R t) increased as a function R 0. Thus, in low coupling cases, almost all of the applied current passes through the interstitial space; e.g., at 1 tunnel (10 Hz), 1.0% of the current passes through the cell pathway (R cell). It is concluded that it is difficult to determine the degree of cell coupling from such impedance analysis, unless the same tissue can be used for its own control, i.e., before and after a large change in cell coupling is introduced. View full abstract»

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  • A reduced sampling schedule for estimating the parameters of the glucose minimal model from a labeled IVGTT

    Page(s): 1023 - 1029
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    In the minimal model of tracer glucose disappearance, 30 blood samples are usually drawn to measure the insulin and the labeled glucose concentration time courses, which provide the database for the model identification. The problem of reducing the number of blood samples withdrawn without, however, deteriorating parameter estimation is addressed. By using a stepwise approach, largely based on optimal experiment design theory, the authors have derived a reliable reduced sampling schedule, which comprises only 14 total samples. The practical application of this reduced schedule has been validated by applying it in a new set of human experiments, completely independent of the ones used in the design phase. View full abstract»

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  • A three-dimensional thermal and electromagnetic model of whole limb heating with a MAPA

    Page(s): 1030 - 1039
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    A realistically shaped, three-dimensional finite element model of a tumor-bearing human lower leg was constructed and was 'attached' mathematically to the whole body thermal model of man described in previous studies by the authors. The central as well as local thermoregulatory feedback control mechanisms which determine blood perfusion to the various tissues and rate of evaporation by sweating were input into the limb model. In addition, the temperature of the arterial blood which feeds into the most proximal section of the lower leg was computed by the whole body thermal model. Results indicate that proper positioning of the limb relative to the miniannular phased array (MAPA) is a significant factor in determining the effectiveness of the treatment. A patient-specific hyperthermia protocol can be designed using this coupled electromagnetic and thermal model. View full abstract»

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  • A device to measure the cross-sectional area of soft connective tissues

    Page(s): 1040 - 1042
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    A device has been designed and fabricated to measure the cross-sectional area of soft connective tissues ex vivo. It consists of two displacement transducers: one sensing tissue thickness and the other sensing width. Outputs are recorded (via an analog to digital interface) using a personal computer. Numerical integration of a thickness versus width plot computes cross-sectional area. This plot also provides a quality check of acquired data. The data were successfully used in biomechanical studies of rabbit patellar tendons, rat medial collateral ligaments, and dissected specimens of human fascia. View full abstract»

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  • Sound velocity inversion in layered media with band-limited and noise-corrupted data (clinical diagnostic ultrasonics application)

    Page(s): 1042 - 1047
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (422 KB)  

    With reflection data measured from two different incident angles, it is possible to make them 'nearly the same' by stretching or contracting the time axis of one of them. In this way, a correspondence is built up between the two travel times, which can be used to calculate the one-dimensional sound velocity profile of the medium. For the special case that the impulse response of the medium consists of sparse spikes, a spectral fitting procedure is developed which deconvolves the received signal, and gives the exact positions of the spikes. The stepwise sound velocity profile can then be calculated from these positions. In experimental measurements the plane wave assumption made in the analysis is not true, but this can be accommodated with some modifications of the calculation. Results of both computer simulation and of measurements are presented, indicating the validity of these processings. View full abstract»

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  • Inspiration produced by bilateral electromagnetic, cervical phrenic nerve stimulation in man

    Page(s): 1047 - 1048
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (161 KB)  

    Eddy-current stimulation of both phrenic nerves at the base of the neck in human subjects was carried out to provide inspiration resulting from tetanic diaphragm contraction. The inspired volume obtained was in excess of spontaneous tidal volume. In a practical application of the method to provide artificial respiration, the trains of stimuli would be applied rhythmically. The train rate determines the respiratory rate. The frequency of the pulse in the train needs to be 25/s or slightly higher and the duration of each train should be long enough so that the inspired air velocity will fall to zero; typically requiring about 0.5-0.7 s. View full abstract»

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  • The effect of CO/sub 2/ laser pulse repetition rate on tissue ablation rate and thermal damage

    Page(s): 1049 - 1052
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    The ablation rate and thermal damage in skin produced by a superpulsed CO 2 laser operating at pulse repetition rates between 1 and 900 Hz were measured. When delivering a fixed number of pulses (20 or 30) of equal energy, a 55-60% increase in the amount of tissue ablated was observed when the pulse repetition rate rose from 10 to 200 Hz. At pulse repetition rates greater than 200 Hz no further increase was seen. Under identical conditions, an 80% increase in the zone of thermal damage was observed when the pulse repetition rate was increased from 1 to 60 Hz. The large increases in tissue ablation and tissue damage may indicate the existence of a layer of mixed-phase (ie., liquid and vapor) or metastable liquid which can store significant amounts of thermal energy between pulses. The data suggest that CO 2 lasers should be operated at relatively low repetition rates for optimal performance. 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