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Biomedical Engineering, IEEE Transactions on

Issue 12 • Date Dec. 1998

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Displaying Results 1 - 9 of 9
  • Vectorcardiographic loop alignment and morphologic beat-to-beat variability

    Publication Year: 1998 , Page(s): 1401 - 1413
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB)  

    The measurement of subtle morphologic beat-to-beat variations in the electrocardiogram is complicated by the presence of respiration-induced movements of the heart. A statistical signal model is developed which accounts for such movements by means of scaling, rotation, and time synchronization of vector-cardiographic loops. The maximum-likelihood estimator of the parameters describing these three transformations is presented and is extended to the case of multiple loop alignment. The performance of the method is assessed by measuring morphologic variability before and after loop alignment. It is shown that the effects of respiration on morphologic variability can be considerably reduced by the new method. Measurements on morphologic variability were typically reduced by a factor of 0.53 after loop alignment. The results show also that beat-to-beat measurements are strongly dependent on the selected sampling rate and that a rate of 1 kHz is too low. View full abstract»

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  • A wavelet transform-based ECG compression method guaranteeing desired signal quality

    Publication Year: 1998 , Page(s): 1414 - 1419
    Cited by:  Papers (40)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (158 KB)  

    This paper presents a new electrocardiogram (ECG) compression method based on orthonormal wavelet transform and an adaptive quantization strategy, by which a predetermined percent root mean square difference (PRD) can be guaranteed with high compression ratio and low implementation complexity. View full abstract»

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  • Estimation of cardiac function from computer analysis of the arterial pressure waveform

    Publication Year: 1998 , Page(s): 1420 - 1428
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (289 KB)  

    This paper presents a method for estimating parameters of a cardiovascular model, including the left-ventricular function, using the sequential quadratic programming (SQP) and the least minimum square (LMS) algorithms. In a first stage, a radial arterial-pressure waveform with corresponding cardiac output are used to automatically seek the set of parameters of the diastolic model. Computer simulation of the model using these parameters generate a pressure waveform and a cardiac output very close to those used for the estimation. In a second stage, the estimated arterial load parameters are used to select the best left-ventricular model function, from four different possibilities, and to estimate its optimum parameter values. The method has been tested numerically and applied to real cases, using data obtained from cardiovascular patients. It has also been subjected to preliminary validation using data obtained from laboratory dogs, in which cardiovascular function was artificially altered. View full abstract»

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  • Evaluation of compartmental and spectral analysis models of [/sup 18/F]FDG kinetics for heart and brain studies with PET

    Publication Year: 1998 , Page(s): 1429 - 1448
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (655 KB)  

    Various models have been proposed to quantitate from [ 18F]-Fluoro-Deoxy-Glucose ([ 18F]FDG) positron emission tomography (PET) data glucose regional metabolic rate. The authors evaluate here four models, a three-rate constants (3 K) model, a four-rate constants (4 K) model, an heterogeneous model (TH) and a spectral analysis (SA) model. The data base consists of [ 18F]FDG dynamic data obtained in the myocardium and brain gray and white matter. All models were identified by nonlinear weighted least squares with weights chosen optimally. The authors show that: 1) 3 K and 4 K models are indistinguishable in terms of parsimony criteria and choice should be made on parameter precision and physiological plausibility; in the gray matter a more complex model than the 3 K one is resolvable; 2) the TH model is resolvable in the gray but not in the white matter; 3) the classic SA approach has some unnecessary hypotheses built in and can be in principle misleading; the authors propose here a new SA model which is more theoretically sound; 4) this new SA approach supports the use of a 3 K model in the heart with a 60 min experimental period; it also indicates that heterogeneity in the brain is modest in the white matter; 5) [ 18F]FDG fractional uptake estimates of the four models are very close in the heart, but not in the brain; 6) a higher than 60 min experimental time is preferable for brain studies. View full abstract»

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  • Electrical stimulation of cardiac tissue by a bipolar electrode in a conductive bath

    Publication Year: 1998 , Page(s): 1449 - 1458
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB)  

    A three-dimensional (3-D) computer simulation of the electrical stimulation of passive cardiac tissue from a bipolar electrode placed within a conductive bath is presented. Through the bidomain model, the syncytial and anisotropic properties of cardiac tissue are taken into account; tissues with equal anisotropy and no transverse coupling are also considered. The membrane is represented by a capacitor and passive resistor in parallel. Located within an isotropic bath, the bipolar electrode is oriented either perpendicular or parallel to the tissue surface. For anisotropic tissue with a small cathode-tissue separation, the tissue surface is highly depolarized under the cathode with the depolarization persisting a considerable distance from the electrode in the transverse fiber direction. Adjacent to this region in the longitudinal direction, areas of hyperpolarization exist. At large distances from the cathode, the tissue surface is hyperpolarized in all directions when the electrode axis is perpendicular to the tissue. In the parallel case, surface depolarization creates buried regions of hyperpolarization. For the perpendicular configuration, the ratio of the steady-state maximum depolarization to steady-state maximum hyperpolarization, an estimate of the ratio of anodal to cathodal threshold, decreases rapidly with increasing cathode-tissue separation. In the parallel case, the depth of the conductive bath significantly affected the transmembrane potential distribution in the tissue. The use of a 3-D model more realistically simulates real-life electrical stimulation (such as stimulation with an implantable pacemaker) and provides insight into the effect of the volume conductor adjacent to the tissue. View full abstract»

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  • A micromachined electrical field-flow fractionation (/spl mu/-EFFF) system

    Publication Year: 1998 , Page(s): 1459 - 1469
    Cited by:  Papers (33)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (410 KB)  

    Micromachining technologies are employed to develop a miniaturized electrical field-flow fractionation (EFFF) separation system. EFFF systems are used to separate colloidal particles such as cells, liposomes, proteins, or other particulates, and to characterize emulsions and other mixtures according to particle charge density. Macromachining techniques have been used to develop existing EFFF technologies. At the present time, the limiting factor in the development of higher precision EFFF separation systems has been the manufacturing approach. In this paper, the theory behind the operation and resolution of a micron-sized EFFF (μ-EFFF) system is described and the advantages to be gained from application of micromachining technologies are given, thus motivating the need for further miniaturization. A completely fabricated μ-EFFF system is developed, separations are performed, and the μ-EFFF system is compared to the theoretically predicted results as well as the results from current macro EFFF systems. View full abstract»

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  • Two-dimensional FDTD analysis of a pulsed microwave confocal system for breast cancer detection: fixed-focus and antenna-array sensors

    Publication Year: 1998 , Page(s): 1470 - 1479
    Cited by:  Papers (186)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB)  

    A novel focused active microwave system is investigated for detecting tumors in the breast. In contrast to X-ray and ultrasound modalities, the method reviewed here exploits the breast-tissue physical properties unique to the microwave spectrum, namely, the translucent nature of normal breast tissues and the high dielectric contrast between malignant tumors and surrounding lesion-free normal breast tissues. The system uses a pulsed confocal technique and time-gating to enhance the detection of tumors while suppressing the effects of tissue heterogeneity and absorption. Using published data for the dielectric properties of normal breast tissues and malignant tumors, the authors have conducted a two-dimensional (2-D) finite-difference time-domain (FDTD) computational electromagnetics analysis of the system. The FDTD simulations showed that tumors as small as 2 mm in diameter could be robustly detected in the presence of the background clutter generated by the heterogeneity of the surrounding normal tissue. Lateral spatial resolution of the tumor location was found to be about 0.5 cm. View full abstract»

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  • Subject index

    Publication Year: 1998 , Page(s): 7 - 20
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    Freely Available from IEEE
  • 1998 IEEE Transactions on Biomedical Engineering Vol. 45

    Publication Year: 1998 , Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    First Page of the Article
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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