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Biomedical Engineering, IEEE Transactions on

Issue 12 • Date Dec. 1994

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Displaying Results 1 - 10 of 10
  • Macromolecular bioactivity: is it resonant interaction between macromolecules?-theory and applications

    Page(s): 1101 - 1114
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    Biological processes in any living organism are based on selective interactions between particular biomolecules. In most cases, these interactions involve and are driven by proteins which are the main conductors of any living process within the organism. The physical nature of these interactions is still not well known. The authors represent a whole new view to biomolecular interactions, in particular protein-protein and protein-DNA interactions, based on the assumption that these interactions are electromagnetic in their nature. This new approach is incorporated in the Resonant Recognition Model (RRM), which was developed over the last 10 years. It has been shown initially that certain periodicities within the distribution of energies of delocalized electrons along a protein molecule are critical for protein biological function, i.e., interaction with its target. If protein conductivity was introduced, then a charge moving through protein backbone can produce electromagnetic irradiation or absorption with spectral characteristics corresponding to energy distribution along the protein. The RRM enables these spectral characteristics, which were found to be in the range of infrared and visible light, to be calculated. These theoretically calculated spectra were proved using experimentally obtained frequency characteristics of some light-induced biological processes. Furthermore, completely new peptides with desired spectral characteristics, and consequently corresponding biological activities, were designed. View full abstract»

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  • Long-term intramuscular electrical activation of the phrenic nerve: safety and reliability

    Page(s): 1115 - 1126
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    The safety and reliability of a system for long-term intramuscular electrical activation of the phrenic nerve was evaluated in seven dogs. In this system, electrodes are implanted bilaterally into the diaphragm without directly contacting the phrenic nerve using a laparoscope to direct placement. Five dogs underwent chronic bilateral intramuscular diaphragm stimulation (IDS) for 61 to 183 days at stimulus parameters selected to evoke at least 120% of the animal's basal ventilation. Two dogs maintained as controls did not undergo chronic stimulation. The safety and reliability of the system was evaluated in terms of tissue responses to the electrode, alterations in diaphragm muscle, pulmonary function, electrode reliability, and cardiac activation. No adverse responses to the electrode or stimulation were found. The histochemistry of chronically stimulated diaphragm suggested transformation towards type I (oxidative metabolism) muscle fibers. Two IDS electrodes dislodged out of a total of 32 IDS electrodes implanted. Both electrodes dislodged within seven days of implant. All IDS electrodes had stable and repeatable recruitment properties. No IDS electrode mechanical failures were found and no electrode corrosion was observed. It is concluded from these experiments that intramuscular activation of the phrenic nerve will present a minimal risk to human patients who are good candidates for clinical studies using this technique. View full abstract»

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  • Long-term intramuscular electrical activation of the phrenic nerve: efficacy as a ventilatory prosthesis

    Page(s): 1127 - 1135
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    The efficacy of a system for long-term intramuscular activation of the phrenic nerve as a ventilatory prosthesis was evaluated in seven dogs. Five dogs underwent chronic bilateral intramuscular diaphragm stimulation (IDS) for 61 to 183 days at stimulus parameters selected to evoke at least 120% of the animal's basal ventilation. Two dogs maintained as controls did not undergo chronic stimulation. The ability of IDS to provide long-term ventilation without diaphragm fatigue was evaluated in terms of the ventilatory capacity of IDS, the effects of chronic IDS on diaphragm contractile properties, and the phrenic nerve recruitment properties of chronic IDS electrodes. Hemi-diaphragms with electrodes placed within 2 cm of the phrenic nerve trunk could be completely activated by 25 mA pulses having a 100 μs pulse width. The tidal volume evoked by IDS in this study was 167% (±48 s.d.) of that required for full-time basal ventilation without diaphragm fatigue. Evoked tidal volume increased after 8 to 9 weeks of chronic IDS for stimulus pulse intervals longer than 50 ms. Electrode recruitment properties were stable for both active and passive implanted electrodes. It is concluded from these studies that with properly placed electrodes IDS is capable of providing reliable full-time ventilatory support without fatiguing the diaphragm. View full abstract»

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  • A three-dimensional microelectrode array for chronic neural recording

    Page(s): 1136 - 1146
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    Describes a 3-D microelectrode array for the chronic recording of single-unit activity in the central nervous system. The array is formed by a microassembly of planar silicon multishank microprobes, which are precisely positioned in a micromachined platform that resides on the surface of the cortex. Interconnects between the probes and the platform are formed using electroplated nickel lead transfers, implemented using automated computer control. All dimensions are controlled to ±1 μm and shank/probe separations as small as 100 μm are possible. Four-probe 16-shank prototype arrays have been tested chronically in guinea pig cortex. After three months in vivo, no significant tissue reaction has been observed surrounding these structures when they remain free to move with the brain, with normal appearing tissue between shanks spaced at 150 μm to 200 μm intervals. The array structure is compatible with the use of signal processing circuitry both on the probes and on the platform. A platform-based signal processing system has been designed to interface with several active probes, providing direct analog access to the recording sites, performing on-chip analog-to-digital conversion of neural activity, and providing simple binary-output recognition of single-unit spike events using a user-input threshold voltage. View full abstract»

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  • Hermite expansions of compact support waveforms: applications to myoelectric signals

    Page(s): 1147 - 1159
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    Nonstationary signals with finite time support are frequently encountered in electrophysiology and other fields of biomedical research. It is often desirable to have a compact description of their shape and of their time evolution. For this purpose, Fourier analysis is not necessarily the best tool. The Hermite-Rodriguez and Associated Hermite basis functions are applied in this work. Both are based on the product of Hermite polynomials and Gaussian functions. Their general properties relevant to biomedical signal processing are reviewed. Preliminary applications are described concerning the analysis and description of: a) test signals such as a square pulse and a single cycle of a sinewave, b) electrically evoked myoelectric signals, and c) power spectra of either voluntary or evoked signals. It is shown that expansions with only five to ten terms provide an excellent description of the computer simulated and real signals. It is shown that these two families of Hermite functions are well suited for the analysis of nonstationary biological evoked potentials with compact time support. An application to the estimation of scaling factors of electrically evoked myoelectric signals is described. The Hermite functions show advantages with respect to the more traditional spectral analysis, especially in the case of signal truncation due to stimulation with interpulse intervals smaller than the duration of the evoked response. Finally, the Hermite approach is found to be suitable for classification of spectral shapes and compression of spectral information of either voluntary or evoked signals. The approach is very promising for neuromuscular diagnosis and assessment because of its capability for information compression and waveform classification. View full abstract»

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  • Combined statistical study of joint angles and ground reaction forces using component and multiple correspondence analysis

    Page(s): 1160 - 1167
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    The purpose of this research is to propose a general methodology to draw gait patterns when including hip, knee and ankle angle excursions in the sagital plane and the three components of the ground reaction force. The multidimensional signal analysis procedure is divided into three main stages: 1) describing the six signals of each step through sliding averages computed for successive time windows, 2) analyzing separately the six step-by-window tables obtained for each signal through principal component analysis to reduce the excessive quantity of data, and 3) analyzing the most informative time windows of the six signals at the same time. To emphasize both linear and nonlinear relationships between the respective time windows, the signal range within a window is cut into fuzzy modalities such as, "low" "medium" and "large." The resulting table is investigated using multiple correspondence analysis. The outcomes are gait patterns combining both time and space aspects. The factor planes obtained from multiple correspondence analysis constitute initial data models so that new data obtained from pathological gait can be directly projected onto them. Such an operation can be used to show how the rehabilitation of a particular subject evolves in relation to normal gait patterns. View full abstract»

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  • Improved beat-to-beat timing measurements of His-bundle signal

    Page(s): 1168 - 1177
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    A simplified bioelectric model of the atrioventricular (AV) junction is proposed to better understand the underlying biophysical generation of intracardiac His-bundle signal and to analyze the effects of electrocatheter displacements on waveform morphology and estimation of AV node conduction time (AVCT). Based on this model, an inverse problem approach has been developed to estimate electrode displacements occurring in real recordings. A measurement correction method is proposed to improve estimation of AVCT. Results illustrate autonomic influences on AVCT, a phenomenon hardly measured with common techniques. View full abstract»

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  • Design and experimental evaluation of an intracavitary ultrasound phased array system for hyperthermia

    Page(s): 1178 - 1187
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    For evaluating the feasibility of treating prostate cancer, a 64-element linear ultrasound phased array applicator for intracavitary hyperthermia was designed and constructed. A 64-channel ultrasound driving system including amplifiers, phase shifters, and RF power meters was also developed to drive the array. The design of the array and driving equipment are presented, as are the results of acoustical field measurements and in vitro perfused phantom studies performed with the array. Several techniques for heating realistically sized tumor volumes were also investigated, including single focus scanning and two techniques for producing multiple stationary foci. The results show that the operation of the array correlated closely with the theoretical model. When producing a single stationary focus, the array was able to increase tissue temperature by 12°C in vitro in perfused phantom. With some minor improvements in array design, intracavitary phased arrays could be evaluated in a clinical environment. View full abstract»

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  • Effects of strong pulsed magnetic fields on the cardiac activity of an open chest dog

    Page(s): 1188 - 1191
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    The heart of an open chest dog was stimulated by strong magnetic fields which were damped sinusoidal pulses with the one-cycle period of 1.47 ms. Stimulation effects were detected by electrocardiograph (ECG) and arterial blood pressure as a function of the strength of the field, the triggering point in the cardiac cycle, and the position of a stimulating coil. The threshold for arrhythmias was a minimum for the stimuli triggered at the apex of the T wave and on the P wave in the ECG. Premature ventricular and premature atrial contractions occurred according to whether the coil was placed over the ventricles or the atria. Ventricular defibrillation can not be attained by the magnetic stimulus with the flux density of 9.2 T which was the maximum field used. View full abstract»

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  • Two-point electrical-fluorescence recording from heart with optical fibers

    Page(s): 1191 - 1194
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    Optical recordings from frog myocardium, stained with a voltage-sensitive dye, have been made through a fiber optic system that uses fiber couplers to provide two excitation/detection paths and to separate excitation light from the fluorescence signal. The excitation light, from a green He-Ne laser (543 nm), is focused into a 100 μm-core fiber then is split 1:1 to two other fibers. Each of these two fibers transmits part of the excitation light through a fiber coupler (1:15 transmittance ratio) to the heart preparation which is stained with the voltage-sensitive dye RH237. The returning red fluorescence is split at the same fiber coupler (15:1 transmittance ratio) and is directed to a photomultiplier tube through a longpass filter. With this two-point mapping method, differences in action potential shape and timing have been observed. 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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Editor-in-Chief
Bin He
Department of Biomedical Engineering