An improved configuration for the reduction of EMG in electrode cuff recordings: a theoretical approach

A theoretical investigation of different electroneurogram recording techniques using electrode cuffs is presented. A new screened tripole arrangement is proposed with a higher inherent signal to interference ratio than the true tripole, which also allows the nulling of the residual electromyogram signal. The reduction in interference is small because the electrode impedance is large compared to the source resistance.     

A spiral nerve cuff electrode for peripheral nerve stimulation

A novel type of nerve cuff electrode consisting of conductive segments embedded within a self-curling sheath of biocompatible insulation has been developed. This spiral nerve cuff is biased to self-wrap around peripheral nerves and possesses a 'self-sizing' property, presenting an alternative to present commercially available, fixed-size nerve cuffs that are manually wrapped around nerves and sutured shut ('split-cylinder' cuffs). Spiral cuff design and manufacture are described. The authors hypothesize that unlike traditional cuffs, the spiral cuff potentially can be implanted safely when sized to fit peripheral nerves snugly. Theoretical pressure analyzes of traditional and spiral cuffs that support this hypothesis are presented. These analyses are designed to predict the minimum CNR (cuff diameter/nerve diameter ratio) at which there is no interference with intraneural blood flow. Results of a preliminary experiment in which snug spiral cuffs were implanted on feline peripheral nerve support the prediction that they may be safe.<>     

An Asymmetric Two Electrode Cuf for Generation of Unidirectionally Propagated Action Potentials

An asymmetric two electrode cuff (ATEC) for generation of unidirectionally propagated action potentials (UPAP's) has been tested in animals. Results indicate that the design is well suited for applications of "collision block" of peripheral nerve transmission. This electrode cuff differs from a standard bipolar electrode cuff in that the anode is enclosed by an insulating sheath of larger diameter than the cuff's cathode and the electrodes are asymmetrically placed within the cuff. In all 13 animals studied, ATEC's with anodes of 1.6 or 3.4 mm diameter and with cathodes of 1.2 mm diameter generated UPAP's when used on a nerve trunk of approximately 1 mm diameter. The cuff length used was 16 mm and the cuff length asymmetry (i. e., distance from cathode to proximal end over distance from cathode to distal end) was 1.7:1. Stimuli were regulated-current rectangular pulses with exponential trailing phases. For pulse widths of 100-500 ?s, exponential (90-10 percent) fall-times of 100-500 f4s minimized total charge injection. The virtual cathode excitation typically seen in standard bipolar electrode cuffs was always adequately suppressed with the ATEC configuration. ATEC's generated UPAP's over a larger window of current amplitudes than monopolar electrodes of similar dimensions.     

On cuff imbalance and tripolar ENG amplifier configurations

Electroneurogram (ENG) recording techniques benefit from the use of tripolar cuffs because they assist in reducing interference from sources outside the cuff. However, in practice the performance of ENG amplifier configurations, such as the quasi-tripole and the true-tripole, has been widely reported to be degraded due to the departure of the tripolar cuff from ideal behavior. This paper establishes the presence of cuff imbalance and investigates its relationship to cuff asymmetry, cuff end-effects and interference source proximity. The paper also presents a comparison of the aforementioned amplifier configurations with a new alternative, termed the adaptive-tripole, developed to automatically compensate for cuff imbalance. The output signal-to-interference ratio of the three amplifier configurations were compared in vivo for two interference signals (stimulus artifact and M-wave) superimposed on compound action potentials. The experiments showed (for the first time) that the two interference signals result in different cuff imbalance values. Nevertheless, even with two distinct cuff imbalances present, the adaptive-tripole performed better than the other two systems in 61.9% of the trials.     

一种离子选择电极前置放大器的设计

采用离子选择电极法测量溶液中某种离子的离子浓度时,离子选择电极与参比电极间产生一个电势差。基于电势差信号的低频率、低幅值和输入高阻抗的特点,设计了一种用于离子选择电极信号采集的前置放大器。该放大器主要由传感器电极、低通滤波电路、超高输入阻抗放大电路、差分式放大电路和50Hz陷波电路等组成。该前置放大器提供了高达10^12Ω 的输入阻抗,并且很好的降低了共模信号的干扰以及工频干扰,可以较好的采集到离子选择电极的微弱信号。     

Pacemaker interference and low-frequency electric induction in humans by external fields and electrodes

The possibility of interference by low-frequency external electric fields with cardiac pacemakers is a matter of practical concern. For pragmatic reasons, experimental investigations into such interference have used contact electrode current sources. However, the applicability to the external electric field problem remains unclear. The recent development of anatomically based electromagnetic models of the human body, together with progress in computational electromagnetics, enable the use of numerical modeling to quantify the relationship between external field and contact electrode excitation. This paper presents a comparison between the computed fields induced in a 3.6-mm-resolution conductivity model of the human body by an external electric field and by several electrode source configurations involving the feet and either the head or shoulders. The application to cardiac pacemaker interference is also indicated.     

LiNbO3 M-Z干涉仪式强度调制器电极设计研究

介绍了LiNbO3 M-Z干涉仪式强度调制器共面波导(对称三电极结构)行波电极的电极宽度、电极间隙、电极厚度以及电极长度的优化设计.     

Reducing Motion Artifacts and Interference in Biopotential Recording

The application of engineering principles and techniques to biopotential recording has resulted in a continual improvement both in the type and the quality of recorded signals. Physical placement of electrodes has enabled improved discrimination of the biopotential of interest (such as the ECG) from unwanted biopotentials (such as the EMG). Understanding that the major motion artifact in ECG recording arises from the skin and not the electrode has resulted in techniques that reduce this artifact, such as skin abrasion and mechanical stabilization. However, skin abrasion makes the skin more subject to irritation, so mild gels are required. The development of the floating silver/silver chloride electrode has eliminated motion artifact and noise caused by the electrode. The development of the driven-right-leg circuit has greatly reduced interference due to power lines. Adaptive filters have reduced the difficult-to-eliminate interference due to spark-gap electrosurgical units.     

A polyimide pressure-contact multielectrode array for implantation along a submillimeter neural process in small animals

We describe a microelectrode system for recordings from nerve bundles with diameters ranging from 20-200 microm. A novel polyimide structure allows for a planar microfabricated device to constrain a free neural process against several recording sites. This polyimide array contains multiple zigzag vias through which a small nerve process may be woven while remaining functionally intact in a live preparation. Our electrode construct features the benefits of nerve cuffs (evenly spaced electrodes in a polymer) and the functionality of a nerve hook (ability to connect to submillimeter processes). The device records extracellular action potentials in the red-swamp crayfish, Procambarus clarkii. Action potential propagation is monitored at several sites along a constrained nerve in this model organism's peripheral nervous system. Details of temporal accuracy and error sources in absolute conduction velocity measurements from microelectrode arrays are discussed.     

Transverse versus longitudinal tripolar configuration for selective stimulation with multipolar cuff electrodes

The ability to stimulate subareas of a nerve selectively is highly desirable, since it has the potential of simplifying surgery to implanting one cuff on a large nerve instead of many cuffs on smaller nerves or muscles, or alternatively can improve function where surgical access to the smaller nerves is limited. In this paper, stimulation was performed with a four-channel multipolar cuff electrode implanted on the sciatic nerve of nine rabbits to compare the extensively researched longitudinal tripolar configuration with the transverse tripolar configuration, which has received less interest. The performance of these configurations was evaluated in terms of selectivity in recruitment of the three branches of the sciatic nerve. The results showed that the transverse configuration was able to selectively activate the sciatic nerve branches to a functionally relevant level in more cases than the longitudinal configuration (20/27 versus 11/27 branches) and overall achieved a higher mean selectivity [0.79 ± 0.13 versus 0.61 ± 0.09 (mean ± standard deviation)]. The transverse configuration was most successful at recruiting the small cutaneous and medium-sized peroneal branches, and less successful at recruiting the large tibial nerve.     

A low-noise front-end for multiplexed ENG recording using CMOS technology

Multi-electrode cuffs have been proposed as a means for the parallel recording of naturally-occurring neural signals. Compared to a conventional tripole cuff providing a single channel signal, additional information about the velocity and direction of nerve signals can be extracted from the multi-electrode recordings. Moreover, interference suppression is improved and overall power consumption reduced, as the analysis shows. In this paper a new recording system is proposed, each channel of which consists of a low-noise preamplifier employing lateral bipolar transistors to provide an impedance match to the tissue and a path to ground for the switching currents of a single high-gain amplifier, which is multiplexed between the channels. The proposed system provides low-noise, low-power operation and practically identical channel gains and is suitable for integration in a larger CMOS-based system.     

Chronic measurement of the stimulation selectivity of the flat interface nerve electrode

The flat interface nerve electrode (FINE) is an attempt to improve the stimulation selectivity of extraneural electrodes. By reshaping peripheral nerves into elliptical cylinders, central fibers are moved closer to the nerve-electrode interface, and additional surface area is created for contact placement. The goals of this study were to test the hypothesis that greater nerve reshaping leads to improved selectivity and to examine the chronic recruitment properties of the FINE. Three FINEs were developed to reshape peripheral nerves to different degrees. Four electrodes of each type were implanted on the sciatic nerves of 12 cats and tested for selectivity over at least three months. There was physiologic evidence of nerve injury in two cats with the tightest cuffs, but the other animals behaved normally. All cuff types were capable of selectively activating branches of the sciatic nerve, as well as groups of fibers within branches. The electrodes that moderately reshaped the nerves demonstrated the most selectivity. Both the selectivity measurements and the recruitment curve characteristics were stable throughout the implant period. From an electrophysiological standpoint, the FINE is a viable alternative for neuroprosthetic devices. A histological analysis of the nerves is under way to evaluate the safety of the FINE.     

Electrocatalytic Determination of Glucose in a Ringer''s Solution by Pulse-Voltammetry

Improvement of the electrocatalytic method of glucose determination was achieved by applying the pulse voltammetry technique. This technique, compared. to previously applied cyclic voltammetry, enhances selectivity of a platinum-black working electrode for glucose measurement. A low catalytic load working electrode has been used which is less susceptible to poisoning and has longer term stability. With cyclic voltammetry previously applied, those electrodes were limited by their narrow concentration range for glucose detection. By applying a pulsing technique, these electrodes exhibit linearity up to a glucose concentration 200 mg/dl with correlation coefficients greater than 0.9. The pulse voltammetry diminishes interference by low molecular weight serum components such as serum urea. Concentrations from 20. to 40 mg/di had an interference of 4 percent compared to 40 percent with cyclic voltammetry. Further investigations are carried on to adopt pulse voltammetry for direct measurements of glucose in body fluids.     

Selectivity of multiple-contact nerve cuff electrodes: a simulation analysis

Advances in functional neuromuscular stimulation (FNS) have increased the need for nerve cuff designs that can control multiple motor functions through selective stimulation of selected populations of axons. This selectivity has proved to be difficult to achieve. Recent experiments suggest that it is possible to slowly reshape peripheral nerve without affecting its physiological function. Using computer simulations we have tested the hypothesis that changing the cross section of a nerve from a round to a flat configuration can significantly improve the selectivity of a nerve cuff. We introduce a new index to estimate selectivity to evaluate the various designs. This index is based on the ability of a nerve electrode to stimulate a target axon without stimulating any other axons. The calculations involve a three-dimensional finite element model to represent the electrical properties of the nerve and cuff and the determination of the firing properties of individual axons. The selectivity rating was found to be significantly higher for the Flat Cuff than the Round Cuff. The result was valid with uniform or random distribution of axons and with a random distribution of fascicles diameters. Flattening of individual fascicles also improved the selectivity of the Flat Cuff but only when the number of contacts used was increased to maintain uniform contact density. Therefore, cuff designs that can reshape the nerve into flatter configurations should yield better cuff performance than the cylindrical cuffs but will require higher contact density.     

Ground-Free ECG Recording with Two Electrodes

ECG recordings normally use three electrodes?two for the differential inputs of the ECG amplifier and the third for ground. We analyze those situations where the ground electrode can be eliminated. We propose a model for the source of electrical interference and determine various parameter values. Making use of experimentally obtained data for the model parameters we suggest optimal design for a two-electrode amplifier. The two-electrode design is useful for biotelemetry, portable Holter monitors, and portable arrhythmia monitors. Under certain circumstances it may be useful for grounded monitoring equipment. The two-electrode technique has the advantage that it improves patient safety by eliminating the ground electrode. Fewer electrodes make patient attachment easier and lower electrode costs.     

Improved performance of mixed single layer top-emission organic light emitting devices using capping layer

The performance of top-emission organic light emitting devices (TEOLEDs) can be improved by using a thin capping layer on top of the semitransparent metal electrode. We investigated the emission properties of inverted mixed single layer TEOLEDs with the same device structure but different capping materials. The thickness of capping layer was optimized by calculation. The power efficiency of device was 2.5 times enhanced when 45 nm TPD capping layer was added. The enhancement is not simply dependent on the transmittance and reflectance of the top contact, but also on other complex phenomena such as the interference effects in the device. The results of properties and dependence of EL spectra on viewing angle for all devices indicated that the large enhancement factor may be related to the complex interference phenomenon in our mixed single layer devices due to the emitter center and recombination region is different from conventional heterojunction devices.     

基于能陷理论的石英力敏谐振器集群的设计

石英谐振器可以作为传感器的敏感元件。为了减小温度等因素的干扰,提高石英晶体谐振器力敏特性,通过能陷理论及其厚度剪切石英晶体谐振能量分布曲线的计算,在同一圆形晶片上设计了多电极力敏谐振器集群。根据共模抑制原理,将谐振器集群输出频率信号作差频处理,以此抑制温度等因素的干扰,再将差频信号叠加以提高石英晶体谐振器集群整体力敏特性。实验结果表明,石英谐振器集群差频输出的温频特性明显优于传统的单电极谐振器,石英晶体谐振器集群整体力灵敏度系数提高到9 992 Hz/N。     

New Interference Sensing Demand Pacemaker Functions

Demand cardiac pacemaker functions are under study that provide new methods to distinguish between cardiac activity and pulsatile electromagnetic interference (PEMI). All known forms of currently marketed ventricular inhibited demand pacemaker (VVI) functions can be inhibited by high level pulsatile electromagnetic interference. The recent introduction of shielded circuitry to protect against disruptive (inhibiting) EMI has reduced pacemaker sensitivity to interference. However, EMI received via the cardiac lead/electrode can still mimic cardiac activity. This mimicing occurs as a consequence of detection by defribrillator protection structures or by amplifier saturation from RF artifacts insufficiently suppressed by input QRS bandpass filters. The new functions under development employ a separate EMI detection receiver for controlling the pacemaker mode to minimize inhibition by PEMI.     

A study of the mechanisms for ESD damage to reticles

Reticles were exposed to the fringing field from an electrode biased to a high voltage. The reticles in the study included reticles designed to benchmark the electrostatic damage (ESD) hazard of photobay and production reticles of a variety of feature sizes. It was found that without any electrical contact between the reticle and the electrode, reticle damage could be done. A wide bandwidth transient-electromagnetic interference (EMI) sensing antenna revealed that the reticle sparked when a voltage as low as 2000 V was applied to the electrode. The tests showed that the ESD threshold of reticles with smaller feature sizes was lower than for reticles with larger feature sizes. Reticles were scanned under optical and atomic force microscopes for reticle damage. It was found that when the voltage was ramped to 17 kV and returned to zero, damage to the reticle was observed. When a voltage of 7.5 kV was applied once, no damage was observed but when it was applied 100 times, reticle damage was observed. This study confirms that ESD damage is done to a reticle by charged objects in the vicinity of the reticle in contrast with the prevailing belief that reticle damage is done only by charge on reticles. The study also showed that reticles can be sufficiently damaged to cause printing errors due to the accumulated damage caused by repeated low level exposure to the fringing field of a charged object in the vicinity of the reticle     

Topical Phenomena Observed in a Short-Gap Atmospheric Discharge Using Rotor and Post Electrodes

Correlation of light emission, discharge structure, waveform of the discharge current, electrode configuration, and electromagnetic radiation is examined with the intent of obtaining an effective means for preventing electromagnetic interference (EMI) due to a short-gap discharge. The electromagnetic radiation (EMR) level resulting from a current step which, in turn, was formed by a discrete movement of a cathode spot was clearly recognized. A combination of needle rotor and needle post gave the smallest electromagnetic radiation level in the experiments.