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Biomedical Engineering, IEEE Transactions on

Issue 2 • Date Feb. 1992

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Displaying Results 1 - 12 of 12
  • A muscle fatigue index based on the relationship between preceding background activity, and myotatic reflex response (MRR)

    Page(s): 105 - 111
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (694 KB)  

    An index of muscular fatigue was developed using the myotatic reflex response (MRR). The MRR of masseter muscles is evoked by periodical mechanical chin tapping during clenching. The MRR waveform is composed of somewhat synchronized action potentials of muscle fibers. The authors estimate the change of the MRR waveform due to fatigue using the instantaneous frequency pattern (IFP) with the Hilbert transform. As a result, the features of IFP were different from the monotonic changes that have been observed by the conventional fatigue indices. That is, a plateau IFP was observed ahead of considerable fatigue, whereas the IFP showed a monopeak pattern during the other phase of an exercise. Also, the relationship between the preceding background mean power frequency and the instantaneous frequency around the first part of the MRR waveform was nonlinear during the whole process of fatigue. These features may allow the authors to estimate the degree of fatigue at each time instant. View full abstract»

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  • An experimental system for auditory image representations

    Page(s): 112 - 121
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1014 KB)  

    An experimental system for the conversion of images into sound patterns was designed to provide auditory image representations within some of the known limitations of the human hearing systems possibly as a step towards the development of a vision substitution device for the blind. The application of an invertible (one-to-one) image-to-sound mapping ensures the preservation of visual information. The system implementation involves a pipelined special-purpose computer connected to a standard television camera. A novel design and the use of standard components have made for a low-cost portable prototype conversion system with a power dissipation suitable for battery operation. Computerized sampling of the system output and subsequent calculation of the approximate inverse (sound-to-image) mapping provided the first convincing experimental evidence for the preservation of visual information in sound representations of complicated images. View full abstract»

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  • Simulation of multipolar fiber selective neural stimulation using intrafascicular electrodes

    Page(s): 122 - 134
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1018 KB)  

    A realistic, quantitative model for the excitation of myelinated nerve fibers by intrafascicular electrodes is presented. It predicts the stimulatory regions of any configuration of any number of electrodes, positioned anywhere inside the fascicle. The model has two parts. First, the nerve fiber is represented by a lumped electrical network and its response to an arbitrary extracellular potential field, is calculated. Second, assuming a cylindrical geometry of the nerve bundle and its surroundings, an analytical expression for this field is derived. With realistic parameters, the model is applied to two cases: monopolar stimulation by a single cathode and stimulation by a specific tripolar configuration. It is shown that tripolar stimulation has the better spatial conductivity of the medium surrounding the nerve and yields a more natural recruitment order. View full abstract»

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  • Quantitative analysis of associated and disassociated phorias: linear and nonlinear static models

    Page(s): 135 - 145
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    Ogle et al. (1967) proposed two measures of oculomotor balance, called associated and disassociated phorias, which he assumed were equivalent. However, experimentally determined values of these phorias do not show a close correspondence. To analyze the rationale behind Ogle's assumption of equality, a linear static model was evaluated. It was found that the linear model predicts an exact correspondence between associated and disassociated phorias. Thus, this assumption depended on the presence of a linear model. To account for the discrepancy between the two measures, four equations for fixation disparity were derived corresponding to the four combinations of deadspace operator outputs. Only one of these four equally possible solutions for associated phoria corresponded to the disassociated phoria. This suggests that the variability in the four solutions may account for the scatter in the experimental data. The nonlinear model was analyzed further to determine its sensitivity to parameter changes and to show how such a model could generate the classical shape of the fixation disparity curve. View full abstract»

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  • Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water

    Page(s): 146 - 153
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (739 KB)  

    A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3-mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low ( epsilon r=10) and high ( epsilon r=85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may he useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase band amplitude adjustment can achieve some limited control over the distribution of radiated power. View full abstract»

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  • Computation of the potential distribution in a four-layer anisotropic concentric spherical volume conductor

    Page(s): 154 - 158
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    A method for solving the potential distribution in a multilayer anisotropic concentric spherical volume conductor has been tested and found to be numerically unstable. It is demonstrated how these numerical difficulties can be avoided. The method is extended by lifting the previously imposed restriction on the innermost region to be isotropic. A convergence criterion for determining the required number of terms in the final series expansion is proposed. The influences of radial and tangential conductivity values of the skull and brain tissue on the dipole-induced potential are investigated. View full abstract»

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  • Some imaging parameters of the oblique dipole layer cardiac generator derivable from body surface electrical potentials

    Page(s): 159 - 164
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    The goal of noninvasively imaging the cardiac electrical generator is considerably complicated by the conductive anisotropy of the cardiac muscle. The ventricular surface activation map has been previously presented as a description of the cardiac generator in image form, but the integral equation defining its relationship to the body surface potentials is valid only under the less accurate uniform dipole layer hypothesis. Using an argument from differential geometry, which allows the integral equation approach to be bypassed, it is shown that the critical points of this map can be localized on the heart surface from the body surface potential in a manner fully consistent with the oblique dipole layer model. Thus, in principle, a realistic and useful image-like output is possible in a limited way even without explicit information regarding conductivity anisotropy. The realization of this output will require improvements in the temporal resolution presently available from existing body surface potential mapping systems. View full abstract»

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  • An information flow technique for category related evoked potentials

    Page(s): 165 - 175
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    A general mathematical technique is developed for information flow among various subsystems of a system when two or more classes of stimuli are presented to the system. The technique is validated by various simulation studies and then applied to a brain system. The usefulness of the technique is demonstrated for visual event related potentials (ERPs) obtained from human subjects suffering from phobias. The stimuli are briefly flashed words and phrases. The world classes are pleasant, unpleasant, conscious, and unconscious. It demonstrated that the information flow is suppressed under supraliminal presentation of the unconscious class, but is strong under subliminal presentation. The technique has the potential of being an objective indicator of conflictual relationships in these patients. The principle of the technique can be applied to any system in which interactions among subsystems are to be analyzed. View full abstract»

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  • Application of adaptive filters to noninvasive acoustical detection of coronary occlusions before and after angioplasty

    Page(s): 176 - 184
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    Isolated diastolic heart sounds taken from recordings made at the patient's bedside were modeled using the autoregressive (AR) and autoregressive moving average (ARMA) methods after adaptive line enhancement (ALE). Decisions were made in a blind fashion without prior knowledge of whether a given recording was made before or after angioplasty. Resulting model frequency spectra showed greater high frequency components (between 400 and 800 Hz) in preangioplasty patients, and a consistent shift in amplitude of the second pole pairs of the AR and ARMA methods with surgery. Blind assessment based on frequency spectra and poles, correctly classified the diastolic recordings in 18 of 20 cases. These results provide evidence supporting the hypothesis that coronary stenoses produce detectable sounds during diastole. View full abstract»

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  • Development of a medical fiber-optic oxygen sensor based on optical absorption change

    Page(s): 185 - 193
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    A fiber-optic oxygen sensor has been developed for use in medical applications. The sensor's viologen indicator becomes strongly absorbant after brief UV stimulation, and then returns to the transparent state. The rate of indicator return to transparency is proportional to the local oxygen concentration. Indicator absorbance is monitored with a red LED and receiving photodiode, and absorbance data are processed by a dedicated CPU. The solid-state sensor system has performance comparable to existing oxygen measurement techniques, and may be applicable for both in vitro and in vivo oxygen measurements. View full abstract»

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  • The relationship of surface reflectance measurements to optical properties of layered biological media

    Page(s): 194 - 201
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    Reflectance from a turbid biological tissue is discussed for a diffusive light source illuminating the surface of the medium, and is related to the optical property distribution within the medium and to photon propagation through the medium. A three-dimensional photon diffusion model with closed form is developed to describe the photon diffuse intensity in a homogeneous medium. The solution is extended by numerical methods to the medium with layered structure. The concepts of photon flux paths and of reflectance indexes are utilized, together with reflectance data, to extract information about the internal optical properties of a medium. The flux path concept was corroborated by successfully detecting in vivo and ex vivo layered differences in optical properties within the biological medium. These studies suggest that the optical properties of subdermal tissue can be measured from light reflectance and that the effect of the upper skin layers can be eliminated. View full abstract»

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  • Temperature selective deposition of Parylene-C

    Page(s): 202 - 206
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (399 KB)  

    A method for selectively depositing conformal, biocompatible coatings of Parylene-C on implantable integrated circuit structures is described. The technique consists of using thin film or diffused resistors to electrically heat the area where an opening in the Parylene is desired. Theoretically predicted and actual Parylene-C thicknesses are compared. 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