Pulse Generator Output Research Articles

Tissue Temperature Increases by a 10 kHz Spinal Cord Stimulation System: Phantom and Bioheat Model

A recently introduced Spinal Cord Stimulation (SCS) system operates at 10 kHz, faster than conventional SCS systems, resulting in significantly more power delivered to tissues. Using a SCS heat phantom and bioheat multi-physics model, we characterized tissue temperature increases by this 10 kHz system. We also evaluated its Implanted Pulse Generator (IPG) output compliance and the role of impedance in temperature increases. The 10 kHz SCS system output was characterized under resistive loads (1-10 KΩ). Separately, fiber optic temperature probes quantified temperature increases (ΔTs) around the SCS lead in specially developed heat phantoms. The role of stimulation Level (1-7; ideal pulse peak-to-peak of 1-7mA) was considered, specifically in the context of stimulation current Root Mean Square (RMS). Data from the heat phantom were verified with the SCS heat-transfer models. A custom high-bandwidth stimulator provided 10 kHz pulses and sinusoidal stimulation for control experiments. The 10 kHz SCS system delivers 10 kHz biphasic pulses (30-20-30 μs). Voltage compliance was 15.6V. Even below voltage compliance, IPG bandwidth attenuated pulse waveform, limiting applied RMS. Temperature increased supralinearly with stimulation Level in a manner predicted by applied RMS. ΔT increases with Level and impedance until stimulator compliance was reached. Therefore, IPG bandwidth and compliance dampen peak heating. Nonetheless, temperature increases predicted by bioheat multi-physic models (ΔT = 0.64°C and 1.42°C respectively at Level 4 and 7 at the cervical segment; ΔT = 0.68°C and 1.72°C respectively at Level 4 and 7 at the thoracic spinal cord)-within ranges previously reported to effect neurophysiology. Heating of spinal tissues by this 10 kHz SCS system theoretically increases quickly with stimulation level and load impedance, while dampened by IPG pulse bandwidth and voltage compliance limitations. If validated in vivo as a mechanism of kHz SCS, bioheat models informed by IPG limitations allow prediction and optimization of temperature changes.

Research on Multiple Wires Electrochemical Micromachining with Ultra-Short Voltage Pulses

Wire electrochemical micromachining (WECMM) with ultra-short voltage pulses has presented its great potential in the fabrication of micro structures in difficult to cut materials because of its tiny etch resolution and good surface integrity. However, this micromachining method has not been well applied as its current machining efficiency is unsuitable for mass production. In this paper, multiple wires electrochemical micromachining (MWECMM) is proposed to increase the productivity in machining arrayed micro structures. The principle of MWECMM has been analyzed to study the influence of ultrashort voltage pulse and the wire electrode amount on the machining process. Results indicated that the charging potential is significantly influenced by voltage pulse on time and the wire electrode amount. As the wire electrode amount increased, the maximum charged potential and the potential charging rate was obviously decreased. Besides, the actual applied voltage between the electrodes decreased because of the pulse generator's output characteristics. Thus, larger voltage amplitude and pulse on time are demanded to obtain a stable MWECMM process with more wire electrodes. In this paper, the optimal wire electrode amount was three when the voltage pulse on time was 80ns and the voltage amplitude was 8V. And the machining efficiency using three wire electrodes was enhanced to be twice that using a wire electrode. Finally, an arrayed tree-like microstructure was successfully fabricated by MWECMM using three wire electrodes simultaneously.

A Wireless-Powered IR-UWB Transmitter for Long-Range Passive RFID Tags in 90-nm CMOS

An impulse radio ultrawideband (IR-UWB) transmitter (TX) intended for long-range passive radio-frequency (RF) identification tags is presented. It is wirelessly powered by an ultrahigh-frequency (UHF) signal. A 128-bit pseudonoise code is transmitted when enough energy is harvested. A new on-off-keying multicycle energy-efficient IR-UWB pulse generator (PG) is proposed, and a co-design with power management circuits is introduced to improve the system supply noise performance. A novel injection-locking divider co-designed with an RF voltage rectifier is proposed to eliminate the injection input resistive load that exists in some designs; otherwise, the input sensitivity would be degraded. A proof-of-concept prototype is fabricated in a TSMC 90-nm CMOS process. Measurements show the TX input sensitivity to be approximately -17.5 dBm with a 900-MHz UHF input. The measured PG output swing is 195 mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> with a -10 dB bandwidth of approximately 3.4 GHz.

Lead Design and Initial Applications of a New Lead for Long‐Term Endovascular Vagal Stimulation

Vagal nerve stimulation (VNS) has negative chronotropic and dromotropic effects. We developed and tested an endovascular spiral vagal stimulation lead (ESVL) designed to follow the projection of the cardiac branches of the vagus nerve around the superior vena cava (SVC) to optimize VNS. ESVL contained six 5-mm coil electrodes, spaced 5-mm apart with a spiral guidewire to provide shape. The tightness and diameter of the guidewire were changed before each placement to simulate different lead designs. Various 2-, 3-, and 4-electrode combinations were used and several lead positions were tested each time. Each VNS protocol included 2-12 V, 15-second pulse trains at 20 Hz, with 2 ms pulse duration. A basket catheter (BC) was used as control and to approximate the initial VNS location. The VNS protocol was performed at the optimal location, using first the BC and then several ESVL configurations. VNS caused a voltage-dependent decrease in heart rate (HR). Using the optimal ESVL configuration at 7 V, HR decreased by 30.4% (37.2 bpm) in dog no. 1 and 12.4% (16.6 bpm) in dog no. 2, versus 15.5% (16.6 bpm) and 16.7% (19.5 bpm) with the BC. A new endovascular spiral lead that takes advantage of the anatomy of the cardiac branches of the vagus nerve in the SVC was developed. VNS using ESVL produced significant HR slowing at voltages slightly below the highest pulse generator output of 7.5 V, which may be suitable for long-term implantation.

New 0.18‐μm CMOS pulse generator for impulse radio ultra‐wideband communication systems

AbstractThis article presents a new circuit to generate a higher‐order derivative Gaussian pulse for the impulse radio ultra‐wideband (IR‐UWB) communication systems. This IR‐UWB pulse generator is designed and measured with the TSMC 0.18‐μm CMOS process. The circuit is able to generate a symmetrical and low‐ringing pulse in a frequency band from 3.1 to 10.6 GHz. Our work shows that the pulse generator's output pulse width is 500 ps with an amplitude of 40 mV (peak to peak). The measurement results validate our design and the circuit functionality. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 342–345, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22132

Dynamic Voltage-Current Characteristics of Unipolar Pulse Glow Discharge

Introduction of pulse plasma power supply is one of the major contributions to plasma surface engineering. The voltage and current waveforms of nitrogen and nitrogen/hydrogen glow discharges in the vacuum total pressure range from 0.1 to 15 mbar were recorded and analyzed concerning the shape, typical operating values and the influence of surface treatment process parameters. It was found that the waveform shape of the voltage and current contains information on pulse generator output parameters and vacuum system properties during normal glow, hollow cathode discharge and arcing. We have also performed the scoping of dynamic parameters and static characteristic, in order to obtain information for the generator and chamber modeling, to be used in a future plasma materials treatment processes control. The influence of process parameters such as total pressure, cathode temperature and biasing voltage on current-voltage characteristics was also considered.

Effect of modern pacing algorithms on generator longevity: a predictive analysis.

Pulse generator (PG) longevity is of major importance to the quality of care of pacemaker patients. A series of automatic algorithms affect PG longevity. This study investigated the individual and combined effects of three algorithms incorporated in the Medtronic Kappa 700 pacemaker series: Capture Management periodically measures the stimulation threshold and adjusts the PG output, Sinus Preference allows the sinus rate to prevail in a specified range below the sensor rate, and Search AV allows an extension of the AV interval if spontaneous conduction is observed. The effects of Capture Management, Sinus Preference, and Search AV on device longevity were studied in 21 consecutive patients treated in the VDD and DDDR modes. Patients were followed for 1 year. The data were analyzed using an equation provided by the manufacturer. Capture Management was activated in 20 patients. For 11 PGs at the basic settings, longevity was extended by 5.2%, whereas reprogrammed PGs had no gain. Sinus Preference was active in four DDDR patients, who gained 12.0 +/- 5.3%atrial sensing from it, with a resultant longevity gain of1.4 +/- 0.45 months(NS). Search AV was active in 19 patients and 8 responders gained 7.8 +/- 4.4 months PG longevity. The overall longevity in this study was 106.3 +/- 8.4 months with all features as programmed, whereas the longevity without Capture Management and Search AV algorithms would be 98.2 +/- 4.9 months, saving 8.1 +/- 5.8 months(range 0-18) of battery life. Thus, two algorithms: Capture Management and Search AV, have clinical relevance in the extension of PG longevity.

Low-Energy Endocardial Defibrillation Using Dual, Triple, and Quadruple Electrode Systems

The feasibility of achieving both universal application of nonthoracotomy leads and low (≤15 J) defibrillation energy requirements by optimizing lead system configuration for use with low-output (<30 J) biphasic shock pulse generators was examined. Sixteen patients (mean age 62 ± 8 years and mean left ventricular ejection fraction of 38 ± 15%) were included in the study. All patients had either experienced syncope with induced ventricular tachycardia (n = 4) or had documented sustained ventricular tachycardia (n = 7) or ventricular fibrillation (n = 5). Defibrillation threshold testing was performed in 2 stages on different days in these patients. In the first stage, 2 defibrillation catheter electrodes were positioned in the right ventricle and superior vena cava with an axillary cutaneous patch. Fifteen-joule, 10- and 5-J biphasic shocks were delivered across 3 different electrode configurations—right ventricle to superior vena cava, right ventricle to axillary patch, right ventricle to a combination of superior vena cava and axillary patch. In the second stage, an 80-ml can electrode was added subcutaneously in a pectoral location to the previous leads. Configurations compared were the right ventricle to pectoral can, and right ventricle to an “array”-combining superior vena cava, can, and axillary patch leads. The defibrillation threshold was determined using a step-down method. In stage 1, mean defibrillation threshold for the right ventricle to axillary patch (12.7 ± 5.9 J) and right ventricle to superior vena cava plus axillary patch (9.8 ± 5.2 J) configurations was lower than the right ventricle to superior vena cava configuration (14.2 ± 6.4 J, p <0.05). In stage 2, the defibrillation was higher for the right ventricle to pectoral can (9.2 ± 5.1 J) configuration compared with the right ventricle to the array (5.6 ± 3.6 J, p ≤0.05). The right ventricle to array had the lowest defibrillation threshold, whereas the right ventricle to pectoral can was the best dual electrode system. Low-energy endocardial defibrillation (≤10 J) was feasible in 72% of tested patients with >1 electrode configuration at 10 J, whereas only 53% of successful patients could be reverted at >1 electrode configuration at 5 J (p <0.05). Reduction in maximum pulse generator output to ≤25 J using these electrode configurations with bidirectional shocks is feasible and maintains an adequate safety margin.This study examines the feasibility of achieving both universal application of nonthoracotomy leads and low (≤15 J) defibrillation energy requirements by optimizing 5 different lead system configurations. Reduction in mean defibrillation threshold to 5.6 ± 3.6 J could be observed, which allowed pulse generators with a maximum output of ≤25 J and yet maintained an adequate safety margin in all patients.

Neuroendocrine mechanisms mediating awakening of the human gonadotropic axis in puberty.

The hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator presides over the pulsatile and feedback-regulated activities of the pituitary-gonadal axis. Awakening of synchronous activity of the GnRH neuronal ensemble in the earliest stages of puberty heralds the onset of full activation of the reproductive axis in girls and boys. Progression from prepuberty to adulthood in boys is directed by marked (30-fold) amplitude enhancement of pulsatile luteinizing hormone (LH) secretion, as assessed by an ultrasensitive immunofluorometric assay and deconvolution analysis. There is a much less apparent rise in LH secretory burst frequency (approximately 1.3-fold increase). Consequently, human puberty is an amplitude-driven neuroendocrine maturational process. However, less is known about pulsatile follicle-stimulating hormone (FSH) release in puberty. Multiple pathophysiologies that result in hypogonadotropic hypogonadism can converge on a final common mechanism of attenuated hypothalamic GnRH pulse generator output and hence reduced LH (and FSH) secretion. Disturbances may take the form of reduced GnRH pulse frequency and/or attenuated GnRH secretory burst mass. When the pathophysiology of hypogonadism originates exclusively in a failed GnRH pulse generator, then either treatment of the primary disease process where possible (e.g., by refeeding in starvation, improved metabolic control in diabetes mellitus, dopamine agonist treatment in hyperprolactinemia, etc) and/or treatment with pulsatile GnRH (e.g., in Kallmann's syndrome, isolated hypothalamic lesions, etc.) can provide relevant therapeutic options in children and adults.

A pulse generator output stage suitable for very low-temperature heat capacity measurements

A low-power circuit that provides a constant-voltage output pulse is described. The stability of the pulse voltage is better than 1 part in 104 and the on/off power ratio is about 1010. The duration of the pulse is controlled by an optically isolated timing signal. The circuit has been used to drive the specimen heater in heat capacity measurements at dilution refrigerator temperatures.

A programmable Gaussian random pulse generator for automated performance measurements

This paper describes a versatile random signal generator which produces logic pulses with a Gaussian distribution for the pulse spacing. The average rate at the pulse generator output can be software-programmed, which makes it useful in performing automated measurements of dead time and CPU time performance of data acquisition systems and modules over a wide range of data rates. Hardware and software components are described and data on the input-output characteristics and the statistical properties of the pulse generator are given. Typical applications are discussed together with advantages over using radioactive test sources. Results obtained from an automated performance run on a VAX 11/785 data acquisition system are presented.

The Effects of Extracorporeal Shock Wave Lithotripsy on Pacemaker Function

Twenty-two pacemaker pulse generators were exposed to shock waves of an extracorporeal shock wave lithotripter to assess the effects of the extremely high pressure transients on pacemaker function. The pulse generator and distal aspect of the lead were positioned 5 cm from the focal point of the lithotripter and 10 cm from each other. Pulse generator function was analyzed during shock wave delivery synchronized with pulse generator output, during shock waves at a rate faster than the escape rate, and after exposure to lithotripsy. During shock waves delivered synchronously with pulse generator output, only one of 22 pulse generators malfunctioned by intermittently reverting to the magnet rate. When subjected to shock waves at a rate greater than the escape rate, 50% of the pulse generators were inhibited by electromechanical interference from the lithotripter. Both bipolar and unipolar devices were affected. However, analysis after exposure to shock waves showed that none of the pacemakers was damaged or spuriously reprogrammed. In conclusion, cardiac pacemakers do not appear to be damaged or reprogrammed by exposure to extracorporeal shock wave lithotripsy. The likelihood of false inhibition appears to be very low if shock waves are delivered synchronously with the QRS.

Electrode-heart interface: definition of the ideal electrode.

In dual-chamber pacing in order to maintain the advantages of small pulse generator size and volume, and increased longevity, it becomes necessary to reduce pulse generator output. This may be accomplished by optimizing the electrode-heart interface. New electrode designs may reduce polarization losses; perhaps even newer materials should be considered. The results of accumulated data must be applicable to long-term pacing.

Isotopic cardiac pacemaker: clinical use.

Our experience, covering two years, and the worldwide experience, covering nearly four years, indicate a high degree of reliability of the Medtronic-Laurens-Alcatel isotopic cardiac pacemaker. No nuclear battery failure and only one failure of pulse generator electronics has occurred. Recovery of devices removed at death or for other reasons has been complete. Data on radiation levels and pulse generator output indicate a potential pulse generator life of 20 years. Nonnuclear and less expensive power sources can be expected to satisfy the five-to ten-year requirements of approximately 85% of patients requiring a pacemaker. The nuclear-powered device, if released for general use, still offers definite advantages in the 15% of patients in the younger age group.

Endocardial threshold of cardiac response as a function of electrode surface area

Threshold of cardiac response to endocardial stimulation has been determined as a function of electrode surface area. A linear direct relationship between cathode surface area and threshold current and energy has been found during acute human stimulation. No electrical difference has been found between unipolar and bipolar endocardial stimulation. Conclusions have been that electrodes should be matched to the pulse generator output capacity and that an excessively large electrode will yield high acute thresholds and chronic thresholds above the output capacity of some pacemakers.