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Biomedical Engineering, IEEE Transactions on

Issue 3 • Date March 2004

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Displaying Results 1 - 25 of 26
  • Table of contents

    Publication Year: 2004 , Page(s): c1 - c4
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  • IEEE Transactions on Biomedical Engineering publication information

    Publication Year: 2004 , Page(s): c2
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  • Finite-element analysis for lumbar interbody fusion under axial loading

    Publication Year: 2004 , Page(s): 393 - 400
    Cited by:  Papers (15)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (587 KB) |  | HTML iconHTML  

    A parametric study was conducted to evaluate axial stiffness of the interbody fusion, compressive stress, and bulging in the endplate due to changes in the spacer position with/without fusion bone using an anatomically accurate and validated L2-L3 finite-element model exercised under physiological axial compression. The results show that the spacer plays an important role in initial stability for fusion, and high compressive force is predicted at the ventral endplate for the models with the spacer and fusion bone together. By varying the positioning of the spacer anteriorly along anteroposterior axis, no significant change in terms of axial stiffness, compressive stress, and bulging of the endplate are predicted for the implant model. The findings suggest that varying the spacer position in surgical situations does not affect the mechanical behavior of the lumbar spine after interbody fusion. View full abstract»

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  • Deep entry of defibrillating effects into homogeneous cardiac tissue

    Publication Year: 2004 , Page(s): 401 - 407
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    A simple, idealized mathematical model of cardiac tissue is used to show that electrical fields applied with the intent of defibrillating the heart can be effective deep within (that is, many space constants into) cardiac tissue, even in cases when the tissue is assumed to have completely homogeneous electrical properties. This conclusion is drawn from the analysis of the two eigenmodes present in the model, which have fundamentally different characteristics. One mode decays very rapidly with space, implying that the associated membrane potential is only present with appreciable amplitude within a few space constants of the tissue surface. The other mode, however, is not directly dependent on the value of the space constant, and allows deep penetration of the membrane potential and, by implication, its associated defibrillating effects. For deep membrane potentials to be generated by this mechanism, the intracellular and extracellular resistivity anisotropy ratios must be unequal, as is typically the case in cardiac tissue. The model also predicts that this mechanism is most effective for a given applied field strength when the electrode size and separation, or spatial features of the externally applied field at the heart surface, are characterized by scalelengths that are commensurate with approximately two times the heart wall thickness. View full abstract»

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  • On nonoscillation and monotonicity of solutions of nonnegative and compartmental dynamical systems

    Publication Year: 2004 , Page(s): 408 - 414
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB) |  | HTML iconHTML  

    Nonnegative and compartmental dynamical system models are widespread in biological, physiological, and ecological sciences and play a key role in understanding these processes. In the specific field of pharmacokinetics involving the study of drug concentrations (in various tissue groups) as a function of time and dose, nonnegative and compartmental models are vital in understanding system wide effects of pharmacological agents. Since drug concentrations are often assumed to monotonically decline after discontinuation of drug administration, standard pharmacokinetic modeling may ignore the possibility of system oscillation. However, nonnegative and compartmental system models may exhibit nonmonotonic solutions resulting in differences between model predictions and experimental data. In this paper, we present necessary and sufficient conditions for identifying nonnegative and compartmental systems that only admit nonoscillatory and monotonic solutions. View full abstract»

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  • A surface EMG generation model with multilayer cylindrical description of the volume conductor

    Publication Year: 2004 , Page(s): 415 - 426
    Cited by:  Papers (43)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    We propose a model for surface electromyography (EMG) signal generation with cylindrical description of the volume conductor. The model is more general and complete with respect to previous approaches. The volume conductor is described as a multilayered cylinder in which the source can be located either along the longitudinal or the angular direction, in any of the layers. The source is represented as a spatio-temporal function which describes the generation, propagation, and extinction of the intracellular action potential at the end-plate, along the fiber, and at the tendons, respectively. The layers are anisotropic. The volume conductor effect is described as a two-dimensional spatial filtering. Electrodes of any shape or dimension are simulated, forming structures which are described as spatial filters. The analytical derivation which leads to the signal in the temporal domain is performed in the spatial and temporal frequency domains. Numerical issues related to the frequency-based approach are discussed. The descriptions of the volume conductor and of the source are applied to the cases of signal generation from a limb and a sphincter muscle. Representative simulations of both cases are provided. The resultant model is based on analytical derivations and constitutes a step forward in surface EMG signal modeling, including features not described in any other analytical approach. View full abstract»

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  • Biomagnetic source detection by maximum entropy and graphical models

    Publication Year: 2004 , Page(s): 427 - 442
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1293 KB) |  | HTML iconHTML  

    This article presents a new approach for detecting active sources in the cortex from magnetic field measurements on the scalp in magnetoencephalography (MEG). The solution of this ill-posed inverse problem is addressed within the framework of maximum entropy on the mean (MEM) principle introduced by Clarke and Janday. The main ingredient of this regularization technique is a reference probability measure on the random variables of interest. These variables are the intensity of current sources distributed on the cortical surface for which this measure encompasses all available prior information that could help to regularize the inverse problem. This measure introduces hidden Markov random variables associated with the activation state of predefined cortical regions. MEM approach is applied within this particular probabilistic framework and simulations show that the present methodology leads to a practical detection of cerebral activity from MEG data. View full abstract»

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  • The biomechanics of lumbar graded facetectomy under anterior-shear load

    Publication Year: 2004 , Page(s): 443 - 449
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    In this paper, an anatomically accurate three-dimensional finite-element (FE) model of the human lumbar spine (L2-L3) was used to study the biomechanical effects of graded bilateral and unilateral facetectomies of L3 under anterior shear. The intact L2-L3 FE model was validated under compression, tension, and shear loading and the predicted responses matched well with experimental data. The gross external (translational and coupled) responses, flexibilities, and facet load were delineated for these iatrogenic changes. Results indicted that unilateral facetectomy of greater than 75% and bilateral facetectomy of 75% or more resection markedly alter the translational displacement and flexibilities of the motion segment. This study suggests that fixation or fusion to restore strength and stability of the lumbar spine may be required for surgical intervention of greater than 75% facetectomy. View full abstract»

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  • Modeling extracellular space electrodiffusion during Lea˜o's spreading depression

    Publication Year: 2004 , Page(s): 450 - 458
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (511 KB) |  | HTML iconHTML  

    Computational modeling of spreading depression (SD) has been used increasingly to study the different mechanisms that are involved in this phenomenon. One of them that is still under discussion involves the mechanisms that originate the extracellular electrical field responsible for the dc potential shift. The main goal of this paper is to present a mathematical derivation for the extracellular electric field that is incorporated in a SD model that has the basic structure of Tuckwell and Miura's model, but with the ionic variations calculated electrochemically. Electrodiffusion equations were used to describe the ionic movement of the four ions Na+, K+, Cl-, and Ca2+. These are mutually coupled by the electric field within the extracellular space (ECS). The results from the simulations show that the model is able to calculate the effect of the ionic changes along the ECS on the electric field, and to reproduce the SD in respect to the most important features that characterize the phenomenon experimentally in the retina or hippocampus. It is suggested that the extracellular negative field-potential shift during SD is due to an electrical field generated by a Goldman-Hodgkin-Katz equation acting within the ECS. View full abstract»

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  • Coupling of radial-basis network and active contour model for multispectral brain MRI segmentation

    Publication Year: 2004 , Page(s): 459 - 470
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3088 KB) |  | HTML iconHTML  

    Magnetic resonance (MR) has been accepted as the reference image study in the clinical environment. The development of new sequences has allowed obtaining diverse images with high clinical importance and whose interpretation requires their joint analysis (multispectral MRI). Recent approaches to segment MRI point toward the definition of hybrid models, where the advantages of region and contour-based methods can be exploited to look for the integration or fusion of information, thus enhancing the performance of the individual approaches. Following this perspective, a hybrid model for multispectral brain MRI segmentation is presented. The model couples a segmenter, based on a radial basis network (RBFNNcc), and an active contour model, based on a cubic spline active contour (CSAC) interpolation. Both static and dynamic coupling of RBFNNcc and CSAC are proposed; the RBFNNcc stage provides an initial contour to the CSAC; the initial contour is optimally sampled with respect to its curvature variations; multispectral information and a restriction term are included into the CSAC energy equation. Segmentations were compared to a reference stack, indicating high-quality performance as measured by Tanimoto indexes of 0.74±0.08. View full abstract»

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  • An interference cancellation algorithm for noninvasive extraction of transabdominal fetal electroencephalogram (TaFEEG)

    Publication Year: 2004 , Page(s): 471 - 483
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (711 KB) |  | HTML iconHTML  

    The electroencephalogram is a noninvasive method of demonstrating cerebral function. The fetal electroencephalogram (FEEG) contains important information regarding the status of a fetus. It is believed that disorganization of normal FEEG development may help detect the onset of cerebral palsy and mental retardation syndromes. Unfortunately, noninvasive methods of monitoring FEEG are not currently available. Noninvasively obtained abdominal surface electrical recordings include FEEG components, but are dominated by large interfering components, and, thus, have very low signal to noise ratio. In this paper, we propose a multistep extraction procedure to separate the four main components in transabdominal recordings: 1) maternal ECG; 2) FECG; and 3) FEEG signals as well as 4) interfering baseline wander. The algorithm is tested on simulated and real transabdominal recordings. This study shows that the proposed method successfully extracts the desired FEEG signal. View full abstract»

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  • On-line segmentation algorithm for continuously monitored data in intensive care units

    Publication Year: 2004 , Page(s): 484 - 492
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    An on-line segmentation algorithm is presented in this paper. It is developed to preprocess data describing the patient's state, sampled at high frequencies in intensive care units, with a further purpose of alarm filtering. The algorithm splits the signal monitored into line segments-continuous or discontinuous-of various lengths and determines on-line when a new segment must be calculated. The delay of detection of a new line segment depends on the importance of the change: the more important the change, the quicker the detection. The linear segments are a correct approximation of the structure of the signal. They emphasise steady-states, level changes and trends occurring on the data. The information returned by the algorithm, which is the time at which the segment begins, its ordinate and its slope, is sufficient to completely reconstruct the filtered signal. This makes the algorithm an interesting tool to provide a processed time history record of the monitored variable. It can also be used to extract on-line information on the signal, such as its trend, in the short or long term. View full abstract»

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  • Dynamical resetting of the human brain at epileptic seizures: application of nonlinear dynamics and global optimization techniques

    Publication Year: 2004 , Page(s): 493 - 506
    Cited by:  Papers (47)  |  Patents (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB) |  | HTML iconHTML  

    Epileptic seizures occur intermittently as a result of complex dynamical interactions among many regions of the brain. By applying signal processing techniques from the theory of nonlinear dynamics and global optimization to the analysis of long-term (3.6 to 12 days) continuous multichannel electroencephalographic recordings from four epileptic patients, we present evidence that epileptic seizures appear to serve as dynamical resetting mechanisms of the brain, that is the dynamically entrained brain areas before seizures disentrain faster and more frequently (p<0.05) at epileptic seizures than any other periods. We expect these results to shed light into the mechanisms of epileptogenesis, seizure intervention and control, as well as into investigations of intermittent spatiotemporal state transitions in other complex biological and physical systems. View full abstract»

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  • Solving the inverse problem of electrocardiography using a Duncan and Horn formulation of the Kalman filter

    Publication Year: 2004 , Page(s): 507 - 515
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (385 KB) |  | HTML iconHTML  

    Numeric regularization methods most often used to solve the ill-posed inverse problem of electrocardiography are spatial and ignore the temporal nature of the problem. In this paper, a Kalman filter reformulation incorporated temporal information to regularize the inverse problem, and was applied to reconstruct left ventricular endocardial electrograms based on cavitary electrograms measured by a noncontact, multielectrode probe. These results were validated against in situ electrograms measured with an integrated, multielectrode basket-catheter. A three-dimensional, probe-endocardium model was determined from multiplane fluoroscopic images. The boundary element method was applied to solve the boundary value problem and determine a linear relationship between endocardial and probe potentials. The Duncan and Horn formulation of the Kalman filter was employed and was compared to the commonly used zero- and first-order Tikhonov spatial regularization as well as the Twomey temporal regularization method. Endocardial electrograms were reconstructed during both sinus and paced rhythms. The Paige and Saunders solution of the Duncan and Horn formulation reconstructed endocardial electrograms at an amplitude relative error of 13% (potential amplitude) which was superior to solutions obtained with zero-order Tikhonov (relative error, 31%), first-order Tikhonov (relative error, 19%), and Twomey regularization (relative error, 44%). Likewise, activation time error in the inverse solution using the Duncan and Horn formulation (2.9 ms) was smaller than that of zero-order Tikhonov (4.8 ms), first-order Tikhonov (5.4 ms), and Twomey regularization (5.8 ms). Therefore, temporal regularization based on the Duncan and Horn formulation of the Kalman filter improves the solution of the inverse problem of electrocardiography. View full abstract»

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  • Estimation of nonstationary EEG with Kalman smoother approach: an application to event-related synchronization (ERS)

    Publication Year: 2004 , Page(s): 516 - 524
    Cited by:  Papers (42)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (797 KB) |  | HTML iconHTML  

    An adaptive spectrum estimation method for nonstationary electroencephalogram by means of time-varying autoregressive moving average modeling is presented. The time-varying parameter estimation problem is solved by Kalman filtering along with a fixed-interval smoothing procedure. Kalman filter is an optimal filter in the mean square sense and it is a generalization of other adaptive filters such as recursive least squares or least mean square. Furthermore, by using the smoother the unavoidable tracking lag of adaptive filters can be avoided. Due to the properties of Kalman filter and benefits of the smoothing the time-frequency resolution of the presented Kalman smoother spectra is extremely high. The presented approach is applied to estimation of event-related synchronization/desynchronization (ERS/ERD) dynamics of occipital alpha rhythm measured from three healthy subjects. With the Kalman smoother approach detailed spectral information can be extracted from single ERS/ERD samples. View full abstract»

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  • Implementation of multichannel sensors for remote biomedical measurements in a microsystems format

    Publication Year: 2004 , Page(s): 525 - 535
    Cited by:  Papers (57)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (566 KB) |  | HTML iconHTML  

    A novel microelectronic "pill" has been developed for in situ studies of the gastro-intestinal tract, combining microsensors and integrated circuits with system-level integration technology. The measurement parameters include real-time remote recording of temperature, pH, conductivity, and dissolved oxygen. The unit comprises an outer biocompatible capsule encasing four microsensors, a control chip, a discrete component radio transmitter, and two silver oxide cells (the latter providing an operating time of 40 h at the rated power consumption of 12.1 mW). The sensors were fabricated on two separate silicon chips located at the front end of the capsule. The robust nature of the pill makes it adaptable for use in a variety of environments related to biomedical and industrial applications. View full abstract»

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  • Implementation of an optical method for the real-time determination of uniaxial strain and vessel mechanics

    Publication Year: 2004 , Page(s): 536 - 538
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (159 KB) |  | HTML iconHTML  

    The determination of the mechanical properties of vascular growth substrates has seen increasing interest in the bioengineering field. Mechanical features such as rupture strength, compliance characteristics, and viscoelastic properties of vascular grafts are important for their design and are indicative of their success in vivo. Thus a simple inexpensive measurement technique for these parameters would be useful. In this report we describe the implementation of an optical method for the measurement of vessel distention under a transluminal pressure gradient. It is based on the concept of laser light occlusion and allows for real time noncontact diameter measurements of hollow vessels ≤2 cm. We demonstrate precise and reproducible measurements of diameter changes of less than 10 μm and, further, with the simultaneous determination of both strain and luminal pressure, were able to determine the elastic modulus of commercially available polymeric vessels. Comparison of the manufacturer specifications and our own measurement of the elastic modulus of these vessels, validate the effectiveness of our system. The advantages of this technique are its relative low cost, ease of implementation, high resolution, and flexibility stemming from its modular setup. View full abstract»

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  • Field stimulation of 2-D sheets of excitable tissue

    Publication Year: 2004 , Page(s): 539 - 540
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (87 KB) |  | HTML iconHTML  

    This paper develops equations for the transmembrane potentials (Vm) that occur in two-dimensional (2-D) sheets of tissue in response to field stimulation from an electrode near but not on the surface of the tissue. Comparison of results with those for one dimension shows that an additional term is present in the 2-D equations that influences the evolution of Vm in the interval between the end of the stimulus and the active propagation that may follow. The results provide an analytical framework for understanding Vm in response to field stimulation in two dimensions, both during the tissue's critical linear phase and thereafter. View full abstract»

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  • Fuzzy logic control of FES rowing exercise in paraplegia

    Publication Year: 2004 , Page(s): 541 - 543
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    An indoor personal rowing machine (Concept 2 Inc., Morrisville, VT) has been modified for functional electrical stimulation assisted rowing exercise in paraplegia. To successfully perform the rowing maneuver, the voluntarily controlled upper body movements must be coordinated with the movements of the electrically stimulated paralyzed legs. To achieve such coordination, an automatic controller was developed that employs two levels of hierarchy. A high level finite state controller identifies the state or phase of the rowing motion and activates a low-level state-dedicated fuzzy logic controller (FLC) to deliver the electrical stimulation to the paralyzed leg muscles. A pilot study with participation of two paraplegic volunteers showed that FLC spent less muscle energy, and produced smoother rowing maneuvers than the existing On-Off constant-level stimulation controller. View full abstract»

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  • Three-dimensional nonlinear image reconstruction for microwave biomedical imaging

    Publication Year: 2004 , Page(s): 544 - 548
    Cited by:  Papers (69)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    Active microwave imaging has attracted significant interests in biomedical applications, in particular for breast imaging. However, the high electrical contrasts in breast tissue also increases the difficulty of forming an accurate image because of the increased multiple scattering. To model such strong three-dimensional (3-D) multiple scattering effects in biomedical imaging applications, we develop a full 3-D inverse scattering algorithm based on the combination of the contrast source inversion and the fast Fourier transform algorithm. Numerical results show that our algorithm can accurately invert for the high-contrast media in breast tissue. View full abstract»

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  • Multifrequency microwave thermograph for biomedical applications

    Publication Year: 2004 , Page(s): 548 - 550
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    This paper presents problems related to thermal radiation of human bodies in microwave range with respect to diagnosis of breast carcinoma. A mathematical model of thermal radiation transfer through tissues is introduced and methods of measurement of temperature, depth and size of a heat source, by means of multifrequency microwave thermograph are described. Theoretical considerations are supplemented by presentation of experimental results. View full abstract»

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  • Massively parallel classification of single-trial EEG signals using a min-max Modular neural network

    Publication Year: 2004 , Page(s): 551 - 558
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (295 KB)  

    This paper presents a method for classifying single-trial electroencephalogram (EEG) signals using min-max modular neural networks implemented in a massively parallel way. The method has three main steps. First, a large-scale, complex EEG classification problem is simply divided into a reasonable number of two-class subproblems, as small as needed. Second, the two-class subproblems are simply learned by individual smaller network modules in parallel. Finally, all the individual trained network modules are integrated into a hierarchical, parallel, and modular classifier according to two module combination laws. To demonstrate the effectiveness of the method, we perform simulations on fifteen different four-class EEG classification tasks, each of which consists of 1491 training and 636 test data. These EEG classification tasks were created using a set of non-averaged, single-trial hippocampal EEG signals recorded from rats; the features of the EEG signals are extracted using wavelet transform techniques. The experimental results indicate that the proposed method has several attractive features. 1) The method is appreciably faster than the existing approach that is based on conventional multilayer perceptrons. 2) Complete learning of complex EEG classification problems can be easily realized, and better generalization performance can be achieved. 3) The method scales up to large-scale, complex EEG classification problems. View full abstract»

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  • Discussion on Instantaneous pq Strategiesfor Control of Active Filters

    Publication Year: 2004 , Page(s): 558
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  • 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society

    Publication Year: 2004 , Page(s): 559
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    Freely Available from IEEE
  • Search for Editor-in-Chief for IEEE Transactions on NanoBioscience

    Publication Year: 2004 , Page(s): 560
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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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering