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Biomedical Engineering, IEEE Transactions on

Issue 11 • Date Nov. 1993

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Displaying Results 1 - 12 of 12
  • Multiresolution wavelet analysis of evoked potentials

    Publication Year: 1993 , Page(s): 1085 - 1094
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    Neurological injury, such as from cerebral hypoxia, appears to cause complex changes in the shape of evoked potential (EP) signals. To characterize such changes we analyze EP signals with the aid of scaling functions called wavelets. In particular, we consider multiresolution wavelets that are a family of orthonormal functions. In the time domain, the multiresolution wavelets analyze EP signals at coarse or successively greater levels of temporal detail. In the frequency domain, the multiresolution wavelets resolve the EP signal into independent spectral bands. In an experimental demonstration of the method, somatosensory EP signals recorded during cerebral hypoxia in anesthetized cats are analyzed. Results obtained by multiresolution wavelet analysis are compared with conventional time-domain analysis and Fourier series expansions of the same signals. Multiresolution wavelet analysis appears to be a different, sensitive way to analyze EP signal features and to follow the EP signal trends in neurologic injury. Two characteristics appear to be of diagnostic value: the detail component of the MRW displays an early and a more rapid decline in response to hypoxic injury while the coarse component displays an earlier recovery upon reoxygenation. View full abstract»

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  • ECG data compression with time-warped polynomials

    Publication Year: 1993 , Page(s): 1095 - 1101
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Presents a new adaptive compression method for ECGs. The method represents each R-R interval by an optimally time-warped polynomial. It achieves a high-quality approximation at less than 250 bits/s. The author shows that the corresponding rates for other transform based schemes (the DCT and the DLT) are always higher. Also, the new method is less sensitive to errors in QRS detection and it removes more (white) noise from the signal. The reconstruction errors are distributed more uniformly in the new scheme and the peak error is usually lower. The reconstruction method is also useful for adaptive filtering of noisy ECG signals. View full abstract»

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  • Cross-correlation analyses of nonlinear systems with spatiotemporal inputs (visual neurons)

    Publication Year: 1993 , Page(s): 1102 - 1113
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB)  

    Methods are presented for analyzing the low-order stimulus-response cross-correlation functions (or kernels) of visual neurons studied with spatiotemporal white noise. In particular, formulas are derived that relate the low-order kernels of a cell to its responses to single-drifting, double-drifting, and counterphase gratings. The harmonic response terms contributed by the low-order kernels include a mean response term, first- and second-harmonic terms, and sum- and difference-harmonic terms. Using the formulas given, one can obtain kernel-based predictions for the spatiotemporal-frequency tuning of each harmonic. These kernel-based predictions can then be compared with harmonic tuning data obtained in experiments with real grating stimuli. The methods are illustrated using data recorded from one simple and one complex cell from the primary visual cortex of the monkey. The approach of transforming low-order kernels into predicted harmonic tuning functions provides a useful data reduction technique as well as providing insight into the interpretation of kernels. View full abstract»

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  • Peptides secondary structure prediction with neural networks: a criterion for building appropriate learning sets

    Publication Year: 1993 , Page(s): 1114 - 1121
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (677 KB)  

    Artificial neural networks have been recently applied with success for protein secondary structure prediction. So far, one of the two main aspects on which neural net performance depends, the topology of the net, has been considered. The present work addresses the other main aspect, the building up of the learning set. The author presents a criterion to build up suitable learning sets based on the alpha -helix percentage. Starting from a set of several well known proteins, the author formed 7 groups of proteins with similar helix percentages and used them for the learning of the same neural net. The author found that the best secondary structure prediction for each of the tested proteins (not belonging to the initial set) was the one obtained using the learning set whose helix percentage was closest to that of the tested protein. The accuracy of correct prediction of the author's method on 3 types of secondary structure ( alpha -helix, beta -sheet and coil), has been compared with the accuracy of other secondary structure prediction methods. View full abstract»

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  • Measurement of acetylcholine receptor function in microcircuit-coupled myoblasts

    Publication Year: 1993 , Page(s): 1122 - 1126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB)  

    An electrophysiological measurement principle for long-term, noninvasive monitoring of the nicotinic acetylcholine receptor function is described. The measurement is based on the ability to record agonist-induced depolarizations of clonal myoblasts that have formed high impedance seals with extracellular microcircuit electrodes. The technique appears promising for several types of assays and environmental monitoring applications. View full abstract»

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  • An optical fiber transducer for single myofibril force measurement

    Publication Year: 1993 , Page(s): 1127 - 1132
    Cited by:  Papers (2)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (483 KB)  

    A force transducer has been developed for use in force measurement of skeletal muscle myofibrils. The transducer is suitable for measurement of passive and contractile forces in a range up to 200 mu g, with 1 mu g resolution. It is based upon the operating principle of the deflection of an optical fiber of known compliance, sensed by the differential illumination of two phototransistors. Attractive features include ease of operation and specimen mounting, high bandwidth, adaptability for different force ranges, and simple and inexpensive construction. View full abstract»

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  • A robust controller for insulin pumps based on H-infinity theory

    Publication Year: 1993 , Page(s): 1133 - 1137
    Cited by:  Papers (13)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (375 KB)  

    The feedback control of insulin pumps for diabetic patients is discussed. Because the parameters in the mathematical model of the blood glucose dynamics present a considerable amount of uncertainty, the H- infinity framework is well suited for the design of controllers that take into account a nice compromise between robust closed-loop regulation of a constant set point and performance expressed in terms of peak values of the plasma glucose concentration. View full abstract»

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  • The four-electrode resistivity technique in anisotropic media: theoretical analysis and application on myocardial tissue in vivo

    Publication Year: 1993 , Page(s): 1138 - 1148
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB)  

    Several aspects of the 4-electrode resistivity technique were studied with special emphasis on the theoretical determination of penetration depth and sample volume in anisotropic media such as (cardiac) muscle. Moreover, the presence of a thin disturbing layer on top of the medium under study was analyzed. A 4-electrode sensor was developed for the measurement of local myocardial resistivity in 2 orthogonal directions. The sensor was applied to the epicardium of anesthetized open chest dogs and, as an example, results are given on the frequency dependence (5-60 kHz) and the changes during the cardiac cycle of longitudinal and transverse myocardial resistivity. View full abstract»

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  • Modeling of neural systems by use of neuronal modes

    Publication Year: 1993 , Page(s): 1149 - 1158
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (850 KB)  

    A methodology for modeling spike-output neural systems from input-output data is proposed, which makes use of "neuronal modes" (NM) and "multi-input threshold" (MT) operators. The modeling concept of NMs was introduced in a previously published paper (V.Z. Marmarelis, ibid., vol.36, p.15-24, 1989) in order to provide concise and general mathematical representations of the nonlinear dynamics involved in signal transformation and coding by a class of neural systems. The authors present and demonstrate (with computer simulations) a method by which the NMs are determined using the 1stand 2nd-order kernel estimates of the system, obtained from input-output data. The MT operator (i.e., a binary operator with multiple real-valued operands which are the outputs of the NMs) possesses an intrinsic refractory mechanism and generates the sequence of output spikes. The spike-generating characteristics of the MT operator are determined by the "trigger regions" defined on the basis of data. This approach is offered as a reasonable compromise between modeling complexity and prediction accuracy, which may provide a common methodological framework for modeling a certain class of neural systems. View full abstract»

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  • Quantitative colorimetric analysis of liquid crystal films (LCF) for phantom dosimetry in microwave hyperthermia

    Publication Year: 1993 , Page(s): 1159 - 1165
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (575 KB)  

    A fully quantitative analysis of liquid crystal film (LCF) color patterns, in phantom thermal dosimetry for microwave hyperthermia, is presented. An accurate determination of absorption rate density (ARD) is achieved by color image computer processing. This work is proven to be an improvement upon the semi-quantitative or qualitative descriptions of LCF colors performed essentially by visual analysis of photographs. Temperature-induced chromatic distributions are acquired as R, G, B (red, green, blue) signals by a CCD camera connected to a PC frame grabber board. These data, stored onto three 512*512 memory buffers, are then converted to H, S, I (hue, saturation, intensity) colorimetric system. Provided a suitable calibration of the LCF, the H quantity can be transformed to temperature using a monotonic relationship. In this way, a temperature accuracy lower than 0.2 degrees C and a spatial resolution less than 1 mm are obtained. A sequence of thermal maps can be acquired and stored on disk at a maximum rate of 1 image/2 s, and then the ARD is calculated at each pixel of the map using the least squares method. View full abstract»

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  • A fast method to compute the potential in the multisphere model (EEG application)

    Publication Year: 1993 , Page(s): 1166 - 1174
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    A series expansion is derived for the potential distribution, caused by a dipole source in a multilayered sphere with piecewise constant conductivity. When the radial coordinate of the source approaches the radial coordinate of the field point the spherical harmonics expansion converges only very slowly. It is shown how the convergence can be improved by first calculating an asymptotic approximation of the potential and using the so-called addition-subtraction method. Since the asymptotic solution is an approximation of the true solution, it gives some insight on the dependence of the potential on the conductivities. The formulas are given in Cartesian coordinates, so that difficulties with coordinate transformations are avoided. Attention is paid to the (fast) computation of the partial derivatives of the potential, which is useful for inverse algorithms. View full abstract»

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  • Effects of induced electric fields on finite neuronal structures: a simulation study

    Publication Year: 1993 , Page(s): 1175 - 1188
    Cited by:  Papers (41)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1185 KB)  

    An analysis is presented of magnetic stimulation of finite length neuronal structures using computer simulations. Models of finite neuronal structures in the presence of extrinsically applied electric fields indicate that excitation can be characterized by two driving functions: one due to field gradients and the other due to fields at the boundaries of neuronal structures. It is found that boundary field driving functions play an important role in governing excitation characteristics during magnetic stimulation. Simulations indicate that axons whose lengths are short compared to the spatial extent of the induced field are easier to excite than longer axons of the same diameter. Simulations also indicate that independent cellular dendritic processes are probably not excited during magnetic stimulation. Analysis of the temporal distribution of induced fields indicates that the temporal shape of the stimulus waveform modulates excitation thresholds and propagation of action potentials. 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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Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering