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Biomedical Engineering, IEEE Transactions on

Issue 8 • Date Aug. 2005

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Displaying Results 1 - 18 of 18
  • Table of contents

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

    Page(s): c2
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  • The course of tissue permeabilization studied on a mathematical model of a subcutaneous tumor in small animals

    Page(s): 1373 - 1381
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (804 KB) |  | HTML iconHTML  

    One of the ways to potentiate antitumor effectiveness of chemotherapeutic drugs is by local application of short intense electric pulses. This causes an increase of the cell membrane permeability and is called electropermeabilization. In order to study the course of tissue permeabilization of a subcutaneous tumor in small animals, a mathematical model was built with the commercial program EMAS, which uses the finite element method. The model is based on the tissue specific conductivity values found in literature, experimentally determined electric field threshold values of reversible and irreversible tissue permeabilization, and conductivity changes in the tissues. The results obtained with the model were then compared to experimental results from the treatment of subcutaneous tumors in mice and a good agreement was obtained. Our results and the reversible and irreversible thresholds used coincide well with the effectiveness of the electrochemotherapy in real tumors where experiments show antitumor effectiveness for amplitudes higher than 900 V/cm ratio and pronounced antitumor effects at 1300 V/cm ratio. View full abstract»

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  • An adaptive detector of genioglossus EMG reflex using Berkner transform for time latency measurement in OSA pathophysiological studies

    Page(s): 1382 - 1389
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (647 KB) |  | HTML iconHTML  

    To investigate obstructive sleep apnea syndrome mechanisms, we developed a device to measure the surface electromyogram (EMG) time latency reflex of the genioglossus muscle stimulated by time and amplitude calibrated negative pharyngeal pressure drops. The reflex signals were found to be disturbed by transient signals that generate false alarms. Thus, to reduce false alarm occurrences we designed an adaptive multiscale method. Continuous wavelet transform (CWT) is widely used in biomedical signal event detection processes. The Berkner transform is an approximation of a CWT that is based on a hierarchical scheme similar to discrete wavelet transform. We used the Berkner transform to build a multiscale detector because it offers the possibility of maxima coefficients linkage that leads to good accuracy in reflex onset localization. As a contribution to this novel approach we used a reconstruction formula to develop an adaptive method for scale range determination in our surface EMG reflex detector. Finally, we characterized our detector in terms of accuracy and robustness, first on synthesized signals and second, on signals acquired on apneic patients and healthy subjects. Preliminary results showed a significant difference (p<0.01) between the two populations regarding the genioglossus muscle mean latency time. These physiological findings may partly explain why the upper airway protective reflex occurring when a negative pressure is applied to the upper airway is ineffective in OSA patients, leading to pharyngeal collapse. View full abstract»

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  • Detection of rapid-eye movements in sleep studies

    Page(s): 1390 - 1396
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (489 KB) |  | HTML iconHTML  

    One of the key features of rapid-eye movement (REM) sleep is the presence of bursts of REMs. Sleep studies routinely use REMs to classify sleep stages. Moreover, REM count or density has been used in studies involving learning and various psychiatric disorders. Most of these studies have been based on the visual identification of REMs, which is generally a very time-consuming task. This and the varying definitions of REMs across scorers have warranted the development of automatic REM detection methodologies. In this paper, we present a new detection scheme that combines many of the intrinsic properties of REMs and requires minimal parameter adjustments. In the proposed method, a single parameter can be used to control the REM detection sensitivity and specificity tradeoff. Manually scored training data are used to develop the method. We assess the performance of the method against manual scoring of individual REM events and present validation results using a separate data set. The ability of the method to discriminate fast horizontal ocular movement in REM sleep from other types of events is highlighted. A key advantage of the presented method is the minimal a priori information requirement. The results of training data (recordings from five subjects) show an overall sensitivity of 78.8% and specificity of 81.6%. The performance on the testing data (recording from five subjects different from the training data) showed overall sensitivity of 67.2% and specificity of 77.5%. View full abstract»

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  • Single-trial dynamical estimation of event-related potentials: a Kalman filter-based approach

    Page(s): 1397 - 1406
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1612 KB) |  | HTML iconHTML  

    A method for single-trial dynamical estimation of event-related potentials (ERPs) is presented. The method is based on recursive Bayesian mean square estimation and the estimators are obtained with a Kalman filtering procedure. We especially focus on the case that previous trials contain prior information of relevance to the trial being analyzed. The potentials are estimated sequentially using the previous estimates as prior information. The performance of the method is evaluated with simulations and with real P300 responses measured using auditory stimuli. Our approach is shown to have excellent capability of estimating dynamic changes form stimulus to stimulus present in the parameters of the ERPs, even in poor signal-to-noise ratio (SNR) conditions. View full abstract»

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  • Automated 3-D reconstruction of the surface of live early-stage amphibian embryos

    Page(s): 1407 - 1414
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1420 KB) |  | HTML iconHTML  

    Although three-dimensional (3-D) reconstructions of the surfaces of live embryos are vital to understanding embryo development, morphogenetic tissue movements and other factors have prevented the automation of this task. Here, we report an integrated set of software algorithms that overcome these challenges, making it possible to completely automate the reconstruction of embryo surfaces and other textured surfaces from multiview images. The process involves: 1) building accurate point correspondences using a robust deformable template block matching algorithm; 2) removing outliers using fundamental matrix calculations in conjunction with a RANSAC algorithm; 3) generating 3-D point clouds using a bundle adjustment algorithm that includes camera position and distortion corrections; 4) meshing the point clouds into triangulated surfaces using a Tight Cocone algorithm that produces water tight models; 5) refining surfaces using midpoint insertion and Laplacian smoothing algorithms; and 6) repeating these steps until a measure of convergence G, the rms difference between successive reconstructions, is below a specified threshold. Reconstructions were made of 2.2-mm diameter, neurulation-stage axolotl (amphibian) embryos using 44 multiview images collected with a robotic microscope. A typical final model (sixth iteration) contained 3787 points and 7562 triangles and had an error measure of G=5.9 μm. View full abstract»

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  • Image overlay guidance for needle insertion in CT scanner

    Page(s): 1415 - 1424
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1900 KB) |  | HTML iconHTML  

    We present an image overlay system to aid needle insertion procedures in computed tomography (CT) scanners. The device consists of a display and a semitransparent mirror that is mounted on the gantry. Looking at the patient through the mirror, the CT image appears to be floating inside the patient with correct size and position, thereby providing the physician with two-dimensional (2-D) "X-ray vision" to guide needle insertions. The physician inserts the needle following the optimal path identified in the CT image rendered on the display and, thus, reflected in the mirror. The system promises to reduce X-ray dose, patient discomfort, and procedure time by significantly reducing faulty insertion attempts. It may also increase needle placement accuracy. We report the design and implementation of the image overlay system followed by the results of phantom and cadaver experiments in several clinical applications. View full abstract»

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  • Fast tracking of cardiac motion using 3D-HARP

    Page(s): 1425 - 1435
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1092 KB) |  | HTML iconHTML  

    Magnetic resonance (MR) tagging is capable of accurate, noninvasive quantification of regional myocardial function. Routine clinical use, however, is hindered by cumbersome and time-consuming postprocessing procedures. We propose a fast, semiautomatic method for tracking three-dimensional (3-D) cardiac motion from a temporal sequence of short- and long-axis tagged MR images. The new method, called 3-D-HARmonic Phase (3D-HARP), extends the HARP approach, previously described for two-dimensional (2-D) tag analysis, to 3-D. A 3-D material mesh model is built to represent a collection of material points inside the left ventricle (LV) wall at a reference time. Harmonic phase, a material property that is time-invariant, is used to track the motion of the mesh through a cardiac cycle. Various motion-related functional properties of the myocardium, such as circumferential strain and left ventricular twist, are computed from the tracked mesh. The correlation analysis of 3D-HARP and FINDTAGS + Tag Strain(E) Analysis (TEA), which are well-established tag analysis techniques, shows that the regression coefficients of circumferential strain (ECC) and twist angle are r2=0.8605 and r2=0.8645, respectively. The total time required for tracking 3-D cardiac motion is approximately 10 min in a 9 timeframe tagged MRI dataset and has the potential to be much faster. View full abstract»

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  • Two-electrode biopotential measurements: power line interference analysis

    Page(s): 1436 - 1442
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (331 KB) |  | HTML iconHTML  

    In this paper, an analysis of power line interference in two-electrode biopotential measurement amplifiers is presented. A model of the amplifier that includes its input stage and takes into account the effects of the common mode input impedance ZC is proposed. This approach is valid for high ZC values, and also for some recently proposed low-ZC strategies. It is shown that power line interference rejection becomes minimal for extreme ZC values ( or infinite), depending on the electrode-skin impedance's unbalance ΔZE. For low ΔZE values, minimal interference is achieved by a low ZC strategy (ZC=0), while for high ΔZE values a very high ZC is required. A critical ΔZE is defined to select the best choice, as a function of the amplifier's Common Mode Rejection Ratio (CMRR) and stray coupling capacitances. Conclusions are verified experimentally using a biopotential amplifier specially designed for this test. View full abstract»

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  • A 2-D motion detection model for low-cost embedded reconfigurable I/O devices

    Page(s): 1443 - 1449
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (703 KB) |  | HTML iconHTML  

    A low-cost reconfigurable embedded apparatus for two-dimensional (2-D) motion detection has been developed. This paper briefly outlines the embedded reconfigurable system architecture, and presents in-depth the 2-D motion detection model, which is directly mapped to reconfigurable hardware. Emphasis is placed on the hardware ability to adapt to individual needs of kinetically challenged persons by altering detection thresholds and delays, thus resulting into an efficient low-cost reconfigurable hardware implementation of the model. This paper also presents how the model detects complex motions through a vocabulary of simple motions, and how the system is trained to individual users' needs. Experimental results and integrated applications of the model for text processing are also presented. View full abstract»

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  • Automated correction of spin-history related motion artefacts in fMRI: Simulated and phantom data

    Page(s): 1450 - 1460
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1499 KB) |  | HTML iconHTML  

    This paper concerns the problem of correcting spin-history artefacts in fMRI data. We focus on the influence of through-plane motion on the history of magnetization. A change in object position will disrupt the tissue's steady-state magnetization. The disruption will propagate to the next few acquired volumes until a new steady state is reached. In this paper we present a simulation of spin-history effects, experimental data, and an automatic two-step algorithm for detecting and correcting spin-history artefacts. The algorithm determines the steady-state distribution of all voxels in a given slice and indicates which voxels need a spin-history correction. The spin-history correction is meant to be applied before standard realignment procedures. To obtain experimental data a special phantom and an MRI compatible motion system were designed. The effect of motion on spin-history is presented for data obtained using this phantom inside a 1.5-T MRI scanner. We show that the presented algorithm is capable of detecting the occurrence of a displacement, and it determines which voxels need a spin-history correction. The results of the phantom study show good agreement with the simulations. View full abstract»

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  • Selective recording of the canine hypoglossal nerve using a multicontact flat interface nerve electrode

    Page(s): 1461 - 1469
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB) |  | HTML iconHTML  

    A flat-interface nerve electrode (FINE) is presented as a potential solution for using multifascicle nerve recordings as part of a closed-loop control system. To investigate the ability of this electrode to achieve selective recordings at physiological signal-to-noise ratio (SNR), a finite-element model (FEM) of a beagle hypoglossal nerve with an implanted FINE was constructed. Action potentials (AP) were generated at various SNR levels and the performance of the electrode was assessed with a selectivity index (0≤SI≤1; ability of the electrode to distinguish two active sources). Computer simulations yielded a selective range (0.05≤SI≤0.76) that was 1) related to the interfiber distance and 2) used to predict the minimum interfiber distance (0.23 mm≤d≤1.42 mm) for selective recording at each SNR. The SI was further evaluated using recorded compound APs elicited from electrically activating the branches of the beagle hypoglossal nerve. For all experiments (n=7), the selectivity (SI=0.45±0.16) was within the range predicted by the FEM. This study suggests that the FINE can record the activity from a multifasciculated nerve and, more importantly, distinguish neural signals from pairs of fascicles at physiologic SNR. View full abstract»

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  • An array of microactuated microelectrodes for monitoring single-neuronal activity in rodents

    Page(s): 1470 - 1477
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1340 KB) |  | HTML iconHTML  

    Arrays of microelectrodes used for monitoring single- and multi-neuronal action potentials often fail to record from the same population of neurons over a period of time for several technical and biological reasons. We report here a novel Neural Probe chip with a 3-channel microactuated microelectrode array that will enable precise repositioning of the individual microelectrodes within the brain tissue after implantation. Thermal microactuators and associated microelectrodes in the Neural Probe chip are microfabricated using the Sandia's Ultraplanar Multi-level MEMS Technology (SUMMiTV) process, a 5-layer polysilicon micromachining technology of the Sandia National labs, Albuquerque, NM. The Neural Probe chip enables precise bi-directional positioning of the microelectrodes in the brain with a step resolution in the order of 8.8 μm. The thermal microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation in either direction was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multi-unit activity. Single unit recordings were obtained from the somatosensory cortex of adult rats over a period of three days demonstrating the feasibility of this technology. Further optimization of the microelectrode insulation and chip packaging will be necessary before this technology can be validated in chronic experiments. View full abstract»

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  • A new approach to accurate measurement of uniaxial joint angles based on a combination of accelerometers and gyroscopes

    Page(s): 1478 - 1484
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1060 KB) |  | HTML iconHTML  

    A new method of measuring joint angle using a combination of accelerometers and gyroscopes is presented. The method proposes a minimal sensor configuration with one sensor module mounted on each segment. The model is based on estimating the acceleration of the joint center of rotation by placing a pair of virtual sensors on the adjacent segments at the center of rotation. In the proposed technique, joint angles are found without the need for integration, so absolute angles can be obtained which are free from any source of drift. The model considers anatomical aspects and is personalized for each subject prior to each measurement. The method was validated by measuring knee flexion-extension angles of eight subjects, walking at three different speeds, and comparing the results with a reference motion measurement system. The results are very close to those of the reference system presenting very small errors (rms=1.3, mean=0.2, SD=1.1 deg) and excellent correlation coefficients (0.997). The algorithm is able to provide joint angles in real-time, and ready for use in gait analysis. Technically, the system is portable, easily mountable, and can be used for long term monitoring without hindrance to natural activities. View full abstract»

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  • Adaptive modeling and spectral estimation of nonstationary biomedical signals based on Kalman filtering

    Page(s): 1485 - 1489
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    We describe an algorithm to estimate the instantaneous power spectral density (PSD) of nonstationary signals. The algorithm is based on a dual Kalman filter that adaptively generates an estimate of the autoregressive model parameters at each time instant. The algorithm exhibits superior PSD tracking performance in nonstationary signals than classical nonparametric methodologies, and does not assume local stationarity of the data. Furthermore, it provides better time-frequency resolution, and is robust to model mismatches. We demonstrate its usefulness by a sample application involving PSD estimation of intracranial pressure signals (ICP) from patients with traumatic brain injury (TBI). View full abstract»

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  • Finite volume stiffness matrix for solving anisotropic cardiac propagation in 2-D and 3-D unstructured meshes

    Page(s): 1490 - 1492
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB) |  | HTML iconHTML  

    The finite volume method (FVM) has been shown recently to be an effective method for discretizing the reaction-diffusion equations that govern wavefront propagation in anisotropic cardiac tissue, as it can naturally handle both complex geometries and no flux boundary conditions without the use of ghost nodes. This communication presents an alternative formulation of FVM for triangle and tetrahedral meshes using the concept of dual basis. An algorithm based on this form is given that leads to an efficient computation of the stiffness matrix, facilitating the incorporation of space adaptive schemes and time varying material properties into numerical simulations of cardiac dynamics. View full abstract»

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  • IEEE Transactions on Biomedical Engineering information for authors

    Page(s): c3
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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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Bin He
Department of Biomedical Engineering