A 4 × 4 array multichannel magnetic stimulation system using submillimeter sized planar square spiral coils: The spatial distribution of electromagnetic field

Multi-coil magnetic stimulation has advantages over single-coil magnetic stimulation, such as more accurate targeting and larger stimulation range. In this paper, a 4 × 4 array multichannel magnetic stimulation system based on a submillimeter planar square spiral coil is proposed. The effects of multiple currents with different directions on the electromagnetic field strength and the focusing zone of the array-structured magnetic stimulation system are studied. The spatial distribution characteristics of the electromagnetic field are discussed. In addition, a method is proposed that can predict the spatial distributions of the electric and magnetic fields when currents in different directions are applied to the array-structured magnetic stimulation system. The study results show that in the section of z = 2 μm, the maximum and average magnetic field strengths of the array-structured magnetic stimulation system are 6.39 mT and 2.68 mT, respectively. The maximum and average electric field strengths are 614.7 mV/m and 122.82 mV/m, respectively, where 84.39% of the measured electric field values are greater than 73 mV/m. The average magnetic field strength of the focusing zone, i.e., the zone in between the two coils, is 3.38 mT with a mean square deviation of 0.18. Therefore, the array-structured multi-channel magnetic stimulation system based on a planar square spiral coil can have a small size of 412 μm × 412 μm × 1.7 μm, which helps improving the spatial distribution of electromagnetic field and increase the effectiveness of magnetic stimulation. The main contribution of this paper is a method for designing multichannel micro-magnetic stimulation devices.

Development of a High-Power Capacity Open Source Electrical Stimulation System to Enhance Research into FES-Assisted Devices: Validation of FES Cycling

Since the first Cybathlon 2016, when twelve teams competed in the FES bike race, we have witnessed a global effort towards the development of stimulation and control strategies to improve FES-assisted devices, particularly for cycling, as a means to practice a recreational physical activity. As a result, a set of technical notes and research paved the way for many other studies and the potential behind FES-assisted cycling has been consolidated. However, engineering research needs instrumented devices to support novel developments and enable precise assessment. Therefore, some researchers struggle to develop their own FES-assisted devices or find it challenging to implement their instrumentation using commercial devices, which often limits the implementation of advanced control strategies and the possibility to connect different types of sensor. In this regard, we hypothesize that it would be advantageous for some researchers in our community to enjoy access to an entire open-source FES platform that allows different control strategies to be implemented, offers greater adaptability and power capacity than commercial devices, and can be used to assist different functional activities in addition to cycling. Hence, it appears to be of interest to make our proprietary electrical stimulation system an open-source device and to prove its capabilities by addressing all the aspects necessary to implement a FES cycling system. The high-power capacity stimulation device is based on a constant current topology that allows the creation of biphasic electrical pulses with amplitude, width, and frequency up to 150 mA, 1000 µs, and 100 Hz, respectively. A mobile application (Android) was developed to set and modify the stimulation parameters of up to eight stimulation channels. A proportional-integral controller was implemented for cadence tracking with the aim to improve the overall cycling performance. A volunteer with complete paraplegia participated in the functional testing of the system. He was able to cycle indoors for 45 min, accomplish distances of more than 5 km using a passive cycling trainer, and pedal 2400 m overground in 32 min. The results evidenced the capacity of our FES cycling system to be employed as a cycling tool for individuals with spinal cord injury. The methodological strategies used to improve FES efficiency suggest the possibility of maximizing pedaling duration through more advanced control techniques.

Analyzing the Effects of Parameters for Tremor Modulation via Phase-Locked Electrical Stimulation on a Peripheral Nerve

(1) Background: Non-invasive neuromodulation is a promising alternative to medication or deep-brain stimulation treatment for Parkinson’s Disease or essential tremor. In previous work, we developed and tested a wearable system that modulates tremor via the non-invasive, electrical stimulation of peripheral nerves. In this article, we examine the proper range and the effects of various stimulation parameters for phase-locked stimulation. (2) Methods: We recruited nine participants with essential tremor. The subjects performed a bean-transfer task that mimics an eating activity to elicit kinetic tremor while using the wearable stimulation system. We examined the effects of stimulation with a fixed duty cycle, at different stimulation amplitudes and frequencies. The epochs of stimulation were locked to one of four phase positions of ongoing tremor, as measured with an accelerometer. We analyzed stimulation-evoked changes of the frequency and amplitude of tremor. (3) Results: We found that the higher tremor amplitude group experienced a higher rate of tremor power reduction (up to 65%) with a higher amplitude of stimulation when the stimulation was applied at the ±peak of tremor phase. (4) Conclusions: The stimulation parameter can be adjusted to optimize tremor reduction, and this study lays the foundation for future large-scale parameter optimization experiments for personalized peripheral nerve stimulation.

Combining Action Observation Treatment with a Brain–Computer Interface System: Perspectives on Neurorehabilitation

Action observation treatment (AOT) exploits a neurophysiological mechanism, matching an observed action on the neural substrates where that action is motorically represented. This mechanism is also known as mirror mechanism. In a typical AOT session, one can distinguish an observation phase and an execution phase. During the observation phase, the patient observes a daily action and soon after, during the execution phase, he/she is asked to perform the observed action at the best of his/her ability. Indeed, the execution phase may sometimes be difficult for those patients where motor impairment is severe. Although, in the current practice, the physiotherapist does not intervene on the quality of the execution phase, here, we propose a stimulation system based on neurophysiological parameters. This perspective article focuses on the possibility to combine AOT with a brain–computer interface system (BCI) that stimulates upper limb muscles, thus facilitating the execution of actions during a rehabilitation session. Combining a rehabilitation tool that is well-grounded in neurophysiology with a stimulation system, such as the one proposed, may improve the efficacy of AOT in the treatment of severe neurological patients, including stroke patients, Parkinson’s disease patients, and children with cerebral palsy.

Wireless Coiled Tubing Disrupts the Industry by Enabling Use of Conventional Coil Tubing for Access and Matrix Acidizing of Multilaterals and Extended Reach Carbonate Reservoirs

As the number of Extended Reach Wells (ERW) with multilaterals and restricted access due to electric submersible pumps (ESP) increases, so does the challenge to enable access and stimulation to these wells to maintain production rates. This paper describes a Slim Access and Stimulation System (SASS) development program launched to develop a game changing technology to give operators the ability to maintain high production rates in unconventional developments. There is available technology today to accurately access extended reach lateral wells, even with restricted access. But the technology is limited to logging only, as the tools and/or control wire are not acid resistant and would limit the pump rate through the coil tubing for pumping acid. The new system would require a tool suite which was acid resistant, enable slim access to the laterals, and have the ability to perform multiple stimulation jobs in one run, with monitoring and control from surface without a wire inside the coiled tubing. The SASS development program gave birth to three separate and revolutionary new technologies: two-way wireless communication and energy harvesting with integrated production logging suite, slim and high-power open hole tractor with a wire bypass to power the tool string, and semi-autonomous lateral access sub, which finds, enters, and confirms the lateral access. The three game changing technologies have application as standalone products, however the real value occurs when they combined as a Slim Access and Stimulation System, run on conventional coiled tubing. The paper will describe working methods and technology incorporated to provide access to restricted extended reach laterals and perform multiple stimulation jobs in a single run. The SASS development program is a testament of how the industry can tackle complex challenges, introducing new technologies across in multiple domains while still adapting to conventional methods. The paper highlights the full system design approach method used to understand and combine features of downhole tools, surface equipment, and operational and handling routines to achieve the overall design goal.

Closing the Loop With Cortical Sensing: The Development of Adaptive Deep Brain Stimulation for Essential Tremor Using the Activa PC+S

Deep Brain Stimulation (DBS) is an important tool in the treatment of pharmacologically resistant neurological movement disorders such as essential tremor (ET) and Parkinson's disease (PD). However, the open-loop design of current systems may be holding back the true potential of invasive neuromodulation. In the last decade we have seen an explosion of activity in the use of feedback to “close the loop” on neuromodulation in the form of adaptive DBS (aDBS) systems that can respond to the patient's therapeutic needs. In this paper we summarize the accomplishments of a 5-year study at the University of Washington in the use of neural feedback from an electrocorticography strip placed over the sensorimotor cortex. We document our progress from an initial proof of hardware all the way to a fully implanted adaptive stimulation system that leverages machine-learning approaches to simplify the programming process. In certain cases, our systems out-performed current open-loop approaches in both power consumption and symptom suppression. Throughout this effort, we collaborated with neuroethicists to capture patient experiences and take them into account whilst developing ethical aDBS approaches. Based on our results we identify several key areas for future work. “Graded” aDBS will allow the system to smoothly tune the stimulation level to symptom severity, and frequent automatic calibration of the algorithm will allow aDBS to adapt to the time-varying dynamics of the disease without additional input from a clinician. Additionally, robust computational models of the pathophysiology of ET will allow stimulation to be optimized to the nuances of an individual patient's symptoms. We also outline the unique advantages of using cortical electrodes for control and the remaining hardware limitations that need to be overcome to facilitate further development in this field. Over the course of this study we have verified the potential of fully-implanted, cortically driven aDBS as a feasibly translatable treatment for pharmacologically resistant ET.