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Increased Anatomical Specificity of Neuromodulation via Modulated Focused Ultrasound  [PDF]
Edin Mehi?, Julia M. Xu, Connor J. Caler, Nathaniel K. Coulson, Chet T. Moritz, Pierre D. Mourad
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0086939
Abstract: Transcranial ultrasound can alter brain function transiently and nondestructively, offering a new tool to study brain function now and inform future therapies. Previous research on neuromodulation implemented pulsed low-frequency (250–700 kHz) ultrasound with spatial peak temporal average intensities (ISPTA) of 0.1–10 W/cm2. That work used transducers that either insonified relatively large volumes of mouse brain (several mL) with relatively low-frequency ultrasound and produced bilateral motor responses, or relatively small volumes of brain (on the order of 0.06 mL) with relatively high-frequency ultrasound that produced unilateral motor responses. This study seeks to increase anatomical specificity to neuromodulation with modulated focused ultrasound (mFU). Here, ‘modulated’ means modifying a focused 2-MHz carrier signal dynamically with a 500-kHz signal as in vibro-acoustography, thereby creating a low-frequency but small volume (approximately 0.015 mL) source of neuromodulation. Application of transcranial mFU to lightly anesthetized mice produced various motor movements with high spatial selectivity (on the order of 1 mm) that scaled with the temporal average ultrasound intensity. Alone, mFU and focused ultrasound (FUS) each induced motor activity, including unilateral motions, though anatomical location and type of motion varied. Future work should include larger animal models to determine the relative efficacy of mFU versus FUS. Other studies should determine the biophysical processes through which they act. Also of interest is exploration of the potential research and clinical applications for targeted, transcranial neuromodulation created by modulated focused ultrasound, especially mFU’s ability to produce compact sources of ultrasound at the very low frequencies (10–100s of Hertz) that are commensurate with the natural frequencies of the brain.
Implantable Microimagers  [PDF]
David C. Ng,Takashi Tokuda,Sadao Shiosaka,Yasuo Tano,Jun Ohta
Sensors , 2008, DOI: 10.3390/s8053183
Abstract: Implantable devices such as cardiac pacemakers, drug-delivery systems, and defibrillators have had a tremendous impact on the quality of live for many disabled people. To date, many devices have been developed for implantation into various parts of the human body. In this paper, we focus on devices implanted in the head. In particular, we describe the technologies necessary to create implantable microimagers. Design, fabrication, and implementation issues are discussed vis-à-vis two examples of implantable microimagers; the retinal prosthesis and in vivo neuro-microimager. Testing of these devices in animals verify the use of the microimagers in the implanted state. We believe that further advancement of these devices will lead to the development of a new method for medical and scientific applications.
Implantable Microimagers
David C. Ng,Takashi Tokuda,Sadao Shiosaka,Yasuo Tano
Sensors , 2008,
Abstract: Implantable devices such as cardiac pacemakers, drug-delivery systems, and defibrillators have had a tremendous impact on the quality of live for many disabled people. To date, many devices have been developed for implantation into various parts of the human body. In this paper, we focus on devices implanted in the head. In particular, we describe the technologies necessary to create implantable microimagers. Design, fabrication, and implementation issues are discussed vis- -vis two examples of implantable microimagers; the retinal prosthesis and in vivo neuro-microimager. Testing of these devices in animals verify the use of the microimagers in the implanted state. We believe that further advancement of these devices will lead to the development of a new method for medical and scientific applications.
Implantable CMOS Biomedical Devices  [PDF]
Jun Ohta,Takashi Tokuda,Kiyotaka Sasagawa,Toshihiko Noda
Sensors , 2009, DOI: 10.3390/s91109073
Abstract: The results of recent research on our implantable CMOS biomedical devices are reviewed. Topics include retinal prosthesis devices and deep-brain implantation devices for small animals. Fundamental device structures and characteristics as well as in vivo experiments are presented.
Neuromodulation: present and emerging methods  [PDF]
Song Luan,Ian Williams,Konstantin Nikolic,Timothy G. Constandinou
Frontiers in Neuroengineering , 2014, DOI: 10.3389/fneng.2014.00027
Abstract: Neuromodulation has wide ranging potential applications in replacing impaired neural function (prosthetics), as a novel form of medical treatment (therapy), and as a tool for investigating neurons and neural function (research). Voltage and current controlled electrical neural stimulation (ENS) are methods that have already been widely applied in both neuroscience and clinical practice for neuroprosthetics. However, there are numerous alternative methods of stimulating or inhibiting neurons. This paper reviews the state-of-the-art in ENS as well as alternative neuromodulation techniques—presenting the operational concepts, technical implementation and limitations—in order to inform system design choices.
Electromagnetic Interference in Implantable Rhythm Devices - The Indian Scenario
Johnson Francis
Indian Pacing and Electrophysiology Journal , 2002,
Abstract: Implantable rhythm device (IRD) is the generic name for the group of implantable devices used for diagnosis and treatment of cardiac arrhythmias. Devices in this category include cardiac pacemakers, implantable cardioverter defibrillators and implantable loop recorders. Since these devices have complex microelectronic circuitry and use electromagnetic waves for communication, they are susceptible to interference from extraneous sources of electromagnetic radiation and magnetic energy. Electromagnetic interference (EMI) is generally not a major problem outside of the hospital environment. The most important interactions occur when a patient is subjected to medical procedures such as magnetic resonance imaging (MRI), electrocautery and radiation therapy. Two articles in this issue of the journal discusses various aspects of EMI on IRD1,2 . Together these articles provide a good review of the various sources of EMI and their interaction with IRD for the treating physician.
Advances in Microelectronics for Implantable Medical Devices  [PDF]
Andreas Demosthenous
Advances in Electronics , 2014, DOI: 10.1155/2014/981295
Abstract: Implantable medical devices provide therapy to treat numerous health conditions as well as monitoring and diagnosis. Over the years, the development of these devices has seen remarkable progress thanks to tremendous advances in microelectronics, electrode technology, packaging and signal processing techniques. Many of today’s implantable devices use wireless technology to supply power and provide communication. There are many challenges when creating an implantable device. Issues such as reliable and fast bidirectional data communication, efficient power delivery to the implantable circuits, low noise and low power for the recording part of the system, and delivery of safe stimulation to avoid tissue and electrode damage are some of the challenges faced by the microelectronics circuit designer. This paper provides a review of advances in microelectronics over the last decade or so for implantable medical devices and systems. The focus is on neural recording and stimulation circuits suitable for fabrication in modern silicon process technologies and biotelemetry methods for power and data transfer, with particular emphasis on methods employing radio frequency inductive coupling. The paper concludes by highlighting some of the issues that will drive future research in the field. 1. Introduction Neuroengineering, the application of engineering techniques to understand, repair, replace, enhance, or otherwise exploit the properties of neural systems, is a topic that is currently generating considerable interest in the research community. The nervous system is a complex network of neurons and glial cells. It comprises the central nervous system (brain and spinal cord) and the peripheral nervous system. Injuries or diseases that affect the nervous system can result in some of the most devastating medical conditions. Conditions, such as stroke, epilepsy, spinal cord injury, and Parkinson’s disease, to name but a few, as well as more general symptoms such as pain and depression, have been shown to benefit from implantable medical devices. These devices are used to bypass dysfunctional pathways in the nervous system by applying electronics to replace lost function. The first implantable medical devices were introduced in the late 1950s with the advent of the heart pacemaker [1, 2] and subsequently the cochlear implant [3, 4]. Both have restored functionality for hundreds of thousands of patients. A pacemaker uses electronics and sensors to continuously monitor the heart’s electrical activity and when arrhythmia is detected, electrical stimulus is applied to the
Implantable Devices: Issues and Challenges  [PDF]
Kateryna Bazaka,Mohan V. Jacob
Electronics , 2013, DOI: 10.3390/electronics2010001
Abstract: Ageing population and a multitude of neurological and cardiovascular illnesses that cannot be mitigated by medication alone have resulted in a significant growth in the number of patients that require implantable electronic devices. These range from sensors, gastric and cardiac pacemakers, cardioverter defibrillators, to deep brain, nerve, and bone stimulators. Long-term implants present specific engineering challenges, including low energy consumption and stable performance. Resorbable electronics may offer excellent short-term performance without the need for surgical removal. However, most electronic materials have poor bio- and cytocompatibility, resulting in immune reactions and infections. This paper reviews the current situation and highlights challenges for future advancements.
Checks and Balances in Neuromodulation  [PDF]
Ronald M. Harris-Warrick,Bruce R. Johnson
Frontiers in Behavioral Neuroscience , 2010, DOI: 10.3389/fnbeh.2010.00047
Abstract: Neuromodulators such as monoamines and peptides play important roles in activating and reconfiguring neural networks to allow behavioral flexibility. While the net effects of a neuromodulator change the network in a particular direction, careful studies of modulatory effects reveal multiple cases where a neuromodulator will activate functionally opposing mechanisms on a single neuron or synapse. This review gives examples of such opposing actions, focusing on the lobster pyloric network, and discusses their possible functional significance. One important action of opposing modulatory actions may be to stabilize the modulated state of the network, and to prevent it from being overmodulated and becoming non-functional.
Patient Alerting Features in Implantable Defibrillators  [cached]
Dirk Vollmann,Markus Zabel,Johnson Francis
Indian Pacing and Electrophysiology Journal , 2008,
Abstract: Implantable cardioverter defibrillators (ICD) are state of the art devices for the primary and secondary prevention of sudden cardiac death.1 As a result, the use of ICDs has increased remarkably over the past years. Since they are life saving devices and because dysfunction can cause fatal pro-arrhythmia2, monitoring of their proper functioning is vital for patient welfare. To date, conventional ICD follow-up is in the form of device clinics where the ICD is interrogated and programmed periodically and the appropriate system function is ensured. Remote device monitoring has recently been introduced and may provide advantages especially for patients living further away from the implanting center.3 Another important feature of current ICDs is the ability to monitor the device function and the patient clinical status, and to alert the patient if evidence for system dysfunction or adverse clinical events is found. This article gives an overview about patient alerting features of current ICDs.
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