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Biomedical Engineering, IEEE Transactions on

Issue 9 • Date Sept. 2005

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Displaying Results 1 - 21 of 21
  • 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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  • A mathematical model for source separation of MMG signals recorded with a coupled microphone-accelerometer sensor pair

    Page(s): 1493 - 1501
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (514 KB) |  | HTML iconHTML  

    Recent advances in sensor technology for muscle activity monitoring have resulted in the development of a coupled microphone-accelerometer sensor pair for physiological acoustic signal recording. This sensor can be used to eliminate interfering sources in practical settings where the contamination of an acoustic signal by ambient noise confounds detection but cannot be easily removed [e.g., mechanomyography (MMG), swallowing sounds, respiration, and heart sounds]. This paper presents a mathematical model for the coupled microphone-accelerometer vibration sensor pair, specifically applied to muscle activity monitoring (i.e., MMG) and noise discrimination in externally powered prostheses for below-elbow amputees. While the model provides a simple and reliable source separation technique for MMG signals, it can also be easily adapted to other applications where the recording of low-frequency (<1 kHz) physiological vibration signals is required. View full abstract»

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  • Simulating pathological gait using the enhanced linear inverted pendulum model

    Page(s): 1502 - 1513
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB) |  | HTML iconHTML  

    In this paper, we propose a new method to simulate human gait motion when muscles are weakened. The method is based on the enhanced version of three-dimensional linear inverted pendulum model that is used for generation of gait in robotics. After the normal gait motion is generated by setting the initial posture and the parameters that decide the trajectories of the center of mass and angular momentum, the muscle to be weakened is specified. By minimizing an objective function based on the force exerted by the specified muscle during the motion, the set of parameters that represent the pathological gait was calculated. Since the number of parameters to describe the motion is small in our method, the optimization process converges much more quickly than in previous methods. The effects of weakening the gluteus medialis, the gluteus maximus, and vastus were analyzed. Important similarities were noted when comparing the predicted pendulum motion with data obtained from an actual patient. View full abstract»

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  • Simulation of the biomechanical behavior of the skin in virtual surgical applications by finite element method

    Page(s): 1514 - 1521
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1261 KB) |  | HTML iconHTML  

    The objective of this study was to develop a software application that is able to support plastic surgeons interested in applying simulations and soft tissue modeling during presurgical planning activities. By using our user-friendly interface and force-displacement graphs, users can analyze scalp skin behaviors when subjected to stress. Users can 1) determine the dynamic of a general point of scalp skin after the application of a specific force, 2) predict the force needed for displacement of a point, and 3) study the deformation of all the points of the entire scalp based on the force applied. Results showed how users are able to manipulate and analyze mechanical behaviors on a mechanical model rather than on a pure geometric qualitative physiological model. The entire application was developed on a Silicon Graphics workstation. View full abstract»

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  • Contributions of Purkinje-myocardial coupling to suppression and facilitation of early afterdepolarization-induced triggered activity

    Page(s): 1522 - 1531
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    Electrical loading by ventricular myocardium modulates conduction system repolarization near Purkinje-ventricular junctions (PVJs). We investigated how that loading suppresses and facilitates early afterdepolarizations (EADs) under conditions where there is a high degree of functional coupling between tissue types, which is consistent with the anatomic arrangement at the peripheral conduction system-myocardial interface. Experiments were completed in eight rabbit right ventricular (RV) free wall preparations. Free-running Purkinje strands were locally superfused, and action potentials were recorded from strands. RV free walls were bathed in normal solution. Surface electrograms were recorded near strand insertions into downstream free wall myocardium. Detailed histology was performed to assemble a computer model with interspersed Purkinje and ventricular myocytes weakly coupled throughout the region. Delays from Purkinje upstrokes to downstream peripheral conduction system and myocardial activation were comparable between experiments and simulations, supporting model node-to-node electrical coupling, i.e., the functional coupling. Purkinje action potential duration (APD) prolongation with localized isoproterenol in experiments and calcium current enhancement in simulations failed to establish EADs. With myocardial APD prolongation by delayed rectifier potassium current inhibition or L-type calcium current enhancement accompanying Purkinje APD prolongation in simulations, however, EAD-induced triggered activity developed. Collectively, our findings suggest competing contributions of the myocardial sink when there is a high degree of functional coupling between tissue types, with the transition from suppression to facilitation of EAD-induced triggered activity depending critically upon myocardial APD prolongation. View full abstract»

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  • Application of a neuro-fuzzy network for gait event detection using electromyography in the child with Cerebral palsy

    Page(s): 1532 - 1540
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    An adaptive neuro-fuzzy inference system (ANFIS) with a supervisory control system (SCS) was used to predict the occurrence of gait events using the electromyographic (EMG) activity of lower extremity muscles in the child with cerebral palsy (CP). This is anticipated to form the basis of a control algorithm for the application of electrical stimulation (ES) to leg or ankle muscles in an attempt to improve walking ability. Either surface or percutaneous intramuscular electrodes were used to record the muscle activity from the quadriceps muscles, with concurrent recording of the gait cycle performed using a VICON motion analysis system for validation of the ANFIS with SCS. Using one EMG signal and its derivative from each leg as its inputs, the ANFIS with SCS was able to predict all gait events in seven out of the eight children, with an average absolute time differential between the VICON recording and the ANFIS prediction of less than 30 ms. Overall accuracy in predicting gait events ranged from 98.6% to 95.3% (root mean-squared error between 0.7 and 1.5). Application of the ANFIS with the SCS to the prediction of gait events using EMG data collected two months after the initial data demonstrated comparable results, with no significant differences between gait event detection times. The accuracy rate and robustness of the ANFIS with SCS with two EMG signals suggests its applicability to ES control. View full abstract»

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  • Spatio-spectral filters for improving the classification of single trial EEG

    Page(s): 1541 - 1548
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (669 KB) |  | HTML iconHTML  

    Data recorded in electroencephalogram (EEG)-based brain-computer interface experiments is generally very noisy, nonstationary, and contaminated with artifacts that can deteriorate discrimination/classification methods. In this paper, we extend the common spatial pattern (CSP) algorithm with the aim to alleviate these adverse effects. In particular, we suggest an extension of CSP to the state space, which utilizes the method of time delay embedding. As we will show, this allows for individually tuned frequency filters at each electrode position and, thus, yields an improved and more robust machine learning procedure. The advantages of the proposed method over the original CSP method are verified in terms of an improved information transfer rate (bits per trial) on a set of EEG-recordings from experiments of imagined limb movements. View full abstract»

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  • Automated design of robust discriminant analysis classifier for foot pressure lesions using kinematic data

    Page(s): 1549 - 1562
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1092 KB) |  | HTML iconHTML  

    In the recent years, the use of motion tracking systems for acquisition of functional biomechanical gait data, has received increasing interest due to the richness and accuracy of the measured kinematic information. However, costs frequently restrict the number of subjects employed, and this makes the dimensionality of the collected data far higher than the available samples. This paper applies discriminant analysis algorithms to the classification of patients with different types of foot lesions, in order to establish an association between foot motion and lesion formation. With primary attention to small sample size situations, we compare different types of Bayesian classifiers and evaluate their performance with various dimensionality reduction techniques for feature extraction, as well as search methods for selection of raw kinematic variables. Finally, we propose a novel integrated method which fine-tunes the classifier parameters and selects the most relevant kinematic variables simultaneously. Performance comparisons are using robust resampling techniques such as Bootstrap 632+ and k-fold cross-validation. Results from experimentations with lesion subjects suffering from pathological plantar hyperkeratosis, show that the proposed method can lead to ∼96% correct classification rates with less than 10% of the original features. View full abstract»

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  • SVD-based optimal filtering for noise reduction in dual microphone hearing aids: a real time implementation and perceptual evaluation

    Page(s): 1563 - 1573
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    In this paper, the first real-time implementation and perceptual evaluation of a singular value decomposition (SVD)-based optimal filtering technique for noise reduction in a dual microphone behind-the-ear (BTE) hearing aid is presented. This evaluation was carried out for a speech weighted noise and multitalker babble, for single and multiple jammer sound source scenarios. Two basic microphone configurations in the hearing aid were used. The SVD-based optimal filtering technique was compared against an adaptive beamformer, which is known to give significant improvements in speech intelligibility in noisy environment. The optimal filtering technique works without assumptions about a speaker position, unlike the two-stage adaptive beamformer. However this strategy needs a robust voice activity detector (VAD). A method to improve the performance of the VAD was presented and evaluated physically. By connecting the VAD to the output of the noise reduction algorithms, a good discrimination between the speech-and-noise periods and the noise-only periods of the signals was obtained. The perceptual experiments demonstrated that the SVD-based optimal filtering technique could perform as well as the adaptive beamformer in a single noise source scenario, i.e., the ideal scenario for the latter technique, and could outperform the adaptive beamformer in multiple noise source scenarios. View full abstract»

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  • Application of an objective method for localizing bilateral cortical FDG PET abnormalities to guide the resection of epileptic foci

    Page(s): 1574 - 1581
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    Purpose: In order to improve the objective localization of bilateral cortical abnormalities in positron emission tomography (PET) image volumes, we developed a new three-dimensional image processing technique. The accuracy of this approach with respect to invasive subdural electroencephalography (EEG) data was assessed in a group of children with neocortical epilepsy. Methods: Glucose PET image volumes were obtained from 12 epileptic children (mean age 5.2±4.3 years). Bilateral cortical areas of abnormal glucose metabolism were objectively determined using two conditional criteria assessed against a normal database. The normal database was derived from a group of 15 adult controls (mean age 27.6 years). The spatial relationship between seizure onset electrodes and PET abnormalities was assessed using a conventional receiver operating characteristic (ROC) analysis as well as using a newly defined spatial proximity index (SPI), which characterizes the association between adjacent, but not coincident, abnormalities. Results: ROC analysis at the 2 standard deviation (SD) threshold, revealed an accuracy of 65% to detect seizure onset areas with a sensitivity of 64±17% and a specificity of 66±24%. Sensitivity decreased to 46±24% at the 3-SD threshold with a specificity of 80±21% (accuracy 75%). The average value for the SPI was determined as 3.82±1.65 which was 20% lower than the SPI value calculated using a simple in-plane two-dimensional asymmetry between homotopic cortical segments (4.52±3.82). Conclusion: The presented image processing technique improves localization of cortical abnormalities and provides valuable imaging clues for placement of subdural EEG grids prior to surgical resection. View full abstract»

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  • An inverse methodology for high-frequency RF coil design for MRI with de-emphasized B/sub 1/ fields

    Page(s): 1582 - 1587
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    An inverse methodology for the design of biologically loaded radio-frequency (RF) coils for magnetic resonance imaging applications is described. Free space time-harmonic electromagnetic Green's functions and de-emphasized B 1 target fields are used to calculate the current density on the coil cylinder. In theory, with the B 1 field de-emphasized in the middle of the RF transverse plane, the calculated current distribution can generate an internal magnetic field that can reduce the central overemphasis effect caused by field/tissue interactions at high frequencies. The current distribution of a head coil operating at 4 T (170 MHz) is calculated using an inverse methodology with de-emphasized B 1 target fields. An in-house finite-difference time-domain routine is employed to evaluate B 1 field and signal intensity inside a homogenous cylindrical phantom and then a complete human head model. A comparison with a conventional RF birdcage coil is carried out and demonstrates that this method can help in decreasing the normal bright region caused by field/tissue interactions in head images at 170 MHz and higher field strengths. View full abstract»

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  • Visual spatial attention control in an independent brain-computer interface

    Page(s): 1588 - 1596
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (585 KB) |  | HTML iconHTML  

    This paper presents a novel brain computer interface (BCI) design employing visual evoked potential (VEP) modulations in a paradigm involving no dependency on peripheral muscles or nerves. The system utilizes electrophysiological correlates of visual spatial attention mechanisms, the self-regulation of which is naturally developed through continuous application in everyday life. An interface involving real-time biofeedback is described, demonstrating reduced training time in comparison to existing BCIs based on self-regulation paradigms. Subjects were cued to covertly attend to a sequence of letters superimposed on a flicker stimulus in one visual field while ignoring a similar stimulus of a different flicker frequency in the opposite visual field. Classification of left/right spatial attention is achieved by extracting steady-state visual evoked potentials (SSVEPs) elicited by the stimuli. Six out of eleven physically and neurologically healthy subjects demonstrate reliable control in binary decision-making, achieving at least 75% correct selections in at least one of only five sessions, each of approximately 12-min duration. The highest-performing subject achieved over 90% correct selections in each of four sessions. This independent BCI may provide a new method of real-time interaction for those with little or no peripheral control, with the added advantage of requiring only brief training. View full abstract»

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  • An ultrasound wearable system for the monitoring and acceleration of fracture healing in long bones

    Page(s): 1597 - 1608
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1689 KB) |  | HTML iconHTML  

    An ultrasound wearable system for remote monitoring and acceleration of the healing process in fractured long bones is presented. The so-called USBone system consists of a pair of ultrasound transducers, implanted into the fracture region, a wearable device and a centralized unit. The wearable device is responsible to carry out ultrasound measurements using the axial-transmission technique and initiate therapy sessions of low-intensity pulsed ultrasound. The acquired measurements and other data are wirelessly transferred from the patient-site to the centralized unit, which is located in a clinical setting. The evaluation of the system on an animal tibial osteotomy model is also presented. A dataset was constructed for monitoring purposes consisting of serial ultrasound measurements, follow-up radiographs, quantitative computed tomography-based densitometry and biomechanical data. The animal study demonstrated the ability of the system to collect ultrasound measurements in an effective and reliable fashion and participating orthopaedic surgeons accepted the system for future clinical application. Analysis of the acquired measurements showed that the pattern of evolution of the ultrasound velocity through healing bones over the postoperative period monitors a dynamic healing process. Furthermore, the ultrasound velocity of radiographically healed bones returns to 80% of the intact bone value, whereas the correlation coefficient of the velocity with the material and mechanical properties of the healing bone ranges from 0.699 to 0.814. The USBone system constitutes the first telemedicine system for the out-hospital management of patients sustained open fractures and treated with external fixation devices. View full abstract»

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  • Development of a force amplitude- and location-sensing device designed to improve the ligament balancing procedure in TKA

    Page(s): 1609 - 1611
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    To improve the ligament balancing procedure during total knee arthroplasty a force-sensing device to intraoperatively measure knee joint forces and moments has been developed. It consists of two sensitive plates, one for each condyle, a tibial base plate and a set of spaces to adapt the device thickness to the patient-specific tibiofemoral gap. Each sensitive plate is equipped with three deformable bridges instrumented with thick-film piezoresistive sensors, which allow accurate measurements of the amplitude and location of the tibiofemoral contact forces. The net varus-valgus moment is then computed to characterize the ligamentous imbalance. The developed device has a measurement range of 0-500 N and an intrinsic accuracy of 0.5% full scale. Experimental trials on a plastic knee joint model and on a cadaver specimen demonstrated the proper function of the device in situ. The results obtained indicated that the novel force-sensing device has an appropriate range of measurement and a strong potential to offer useful quantitative information and effective assistance during the ligament balancing procedure in total knee arthroplasty. View full abstract»

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  • In vitro comparison of the charge-injection limits of activated iridium oxide (AIROF) and platinum-iridium microelectrodes

    Page(s): 1612 - 1614
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    The charge-injection limits of activated iridium oxide electrodes (AIROF) and PtIr microelectrodes with similar geometric area and shape have been compared in vitro using a stimulation waveform that delivers cathodal current pulses with current-limited control of the electrode bias potential in the interpulse period. Charge-injection limits were compared over a bias range of 0.1-0.7 V (versus Ag|AgCl) and pulse frequencies of 20, 50, and 100 Hz. The AIROF was capable of injecting between 4 and 10 times the charge of the PtIr electrode, with a maximum value of 3.9 mC/cm 2 obtained at a 0.7 V bias and 20 Hz frequency. View full abstract»

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  • Recording human evoked potentials that follow the pitch contour of a natural vowel

    Page(s): 1614 - 1618
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    We investigated whether pitch-synchronous neural activity could be recorded in humans, with a natural vowel and a vowel in which the fundamental frequency was suppressed. Small variations of speech periodicity were detected in the evoked responses using a fine structure spectrograph (FSS). A significant response (P≪0.001) was measured in all seven normal subjects even when the fundamental frequency was suppressed, and it very accurately tracked the acoustic pitch contour (normalized mean absolute error <0.57%). Small variations in speech periodicity, which humans can detect, are therefore available to the perceptual system as pitch-synchronous neural firing. These findings suggest that the measurement of pitch-evoked responses may be a viable tool for objective speech audiometry. View full abstract»

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  • Correspondence between the location of evoked potential generators and sites of maximal sensitivity to stimulation

    Page(s): 1619 - 1621
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (142 KB) |  | HTML iconHTML  

    The potential recorded by a set of electrodes as an action potential traverses a small axonal segment is proportional to the transmembrane potential produced during stimulation of that axon segment by the same set of recording electrodes, under certain circumstances. First, the membrane must have a constant thickness which is so small that the difference between the surface area of the inner and outer surfaces is minimal. Second, all media must be linear. Third, there must be a monotonically increasing relation between the mean transmembrane potential induced by a stimulus and the maximum transmembrane potential. Fourth, as each axon segment depolarizes, the transmembrane current and change in membrane potential during this time are same. This principle remains true for magnetic stimulation and recording as long as currents generated at the boundaries between regions of differing conductivity outside the axon contribute minimally to the field at the axon. This allows the identification of the point at which an action potential generates a maximal extracellular potential as the point that is stimulated with the lowest threshold. View full abstract»

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  • 28th Annual International Conference of the IEEE Engineering in Medicine and Biology Society: Engineering Revolution in BioMedicine

    Page(s): 1622 - 1623
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  • Special issue on volumetric reconstruction of medical images

    Page(s): 1624
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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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Editor-in-Chief
Bin He
Department of Biomedical Engineering