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Spinal cord injury (SCI) results in the inability to empty the bladder voluntarily, and neurogenic detrusor overactivity (NDO) and detrusor sphincter dyssynergia (DSD) negatively impact both the health and quality of life of persons with SCI. Current approaches to treat bladder dysfunction in persons with SCI, including self-catheterisation and anticholinergic medications, are inadequate, and novel approaches are required to restore continence with increased bladder capacity, as well as to provide predictable and efficient on-demand voiding. Improvements in bladder function following SCI have been documented using a number of different modalities of spinal cord stimulation (SCS) in both persons with SCI and animal models, including SCS alone or SCS with concomitant activity-based training. Improvements include increased volitional voiding, voided volumes, bladder capacity, and quality of life, as well as decreases in NDO and DSD. Further, SCS is a well-developed therapy for chronic pain, and existing Food And Drug Administration (FDA)-approved devices provide a clear pathway to sustainable commercial availability and impact. However, the effective stimulation parameters and the appropriate timing and location of stimulation for SCS-mediated restoration of bladder function require further study, and studies are needed to determine underlying mechanisms of action.

Implantable motor neuroprosthetic systems can restore function to individuals with significant disabilities, such as spinal cord injury, stroke, cerebral palsy, and multiple sclerosis. Neuroprostheses provide restored functionality by electrically activating paralysed muscles in coordinated patterns that replicate (enable) controlled movement that was lost through injury or disease. It is important to consider the general topology of the implanted system itself. The authors demonstrate that the wired multipoint implant technology is practical and feasible as a basis for the development of implanted multi-function neuroprosthetic systems. The advantages of a centralised power supply are significant. Heating due to recharge can be mitigated by using an actively cooled external recharge coil. Using this approach, the time required to perform a full recharge was significantly reduced. This approach has been demonstrated as a practical option for regular clinical use of implanted neuroprostheses.

This work proposes and computationally investigate the use of magnetic neural stimulation as an alternative to electrical stimulation to achieve selective activation of rat sciatic nerve. In particular, they assess the effectiveness of an array of small coils to obtain selective neural stimulation, as compared to a single coil. Specifically, an array of four mm-sized coils is used to stimulate rat sciatic nerve, targeting the regions of fascicles that are associated with different muscles of the leg. To evaluate the selectivity of activation, a three-dimensional heterogeneous multi-resolution nerve model is implemented using the impedance method for the computation of the magnetic and electric fields in the nerve. The performance metric ‘selectivity index’ is defined that measures the recruitment of the targeted region compared to other non-targeted regions of the nerve. The selectivity index takes values between −1 (least selective) and 1 (most selective). For each targeted region, a selectivity index of 0.75 or better is predicted for the proposed array configuration. The results suggest that an array of coils can provide superior spatial control of the electric field induced in the neural tissue compared to traditional extraneural electrode arrays, thus opening the possibility to applications where selective neurostimulation is of interest.

One of the efficient methods in controlling the Parkinson's tremor is Deep Brain Stimulation (DBS) therapy. The stimulation of Basal Ganglia (BG) by DBS brings no feedback though the existence of feedback reduces the additional stimulatory signal delivered to the brain. So this study offers a new adaptive architecture of a closed‐loop control system in which two areas of BG are stimulated simultaneously to decrease the following three indicators: hand tremor, the level of a delivered stimulation signal in the disease condition, and the level of a delivered stimulation signal in health condition to the disease condition. One area (STN: subthalamic nucleus) is stimulated with an adaptive sliding mode controller and the other area (GPi: Globus Pallidus internal) with partial state feedback controller. The simulation results of stimulating two areas of BG showed satisfactory performance. [ABSTRACT FROM AUTHOR]

Sacral nerve stimulation (SNS) is an established treatment for faecal incontinence involving the implantation of a quadripolar electrode into a sacral foramen, through which an electrical stimulus is applied. Little is known about the induced spread of electric current around the SNS electrode and its effect on adjacent tissues, which limits optimisation of this treatment. The authors constructed a 3-dimensional imaging based finite element model in order to calculate and visualise the stimulation induced current and coupled this to biophysical models of nerve fibres. They investigated the impact of tissue inhomogeneity, electrode model choice and contact configuration and found a number of effects. (i) The presence of anatomical detail changes the estimate of stimulation effects in size and shape. (ii) The difference between the two models of electrodes is minimal for electrode contacts of the same length. (iii) Surprisingly, in this arrangement of electrode and neural fibre, monopolar and bipolar stimulation induce a similar effect. (iv) Interestingly when the active contact is larger, the volume of tissue activated reduces. This work establishes a protocol to better understand both therapeutic and adverse stimulation effects and in the future will enable patient-specific adjustments of stimulation parameters.

Dielectric spectroscopy (DS) is a non‐invasive, label‐free, and promising technique for measuring dielectric properties of biological cells. Recent developments in microfabrication techniques made it possible to perform DS measurements with minute volume of cell suspensions. However, when the cell size approaches the size of the measurement chamber, especially, for single cell measurements, the analytical models [Maxwell–Wagner and Bruggeman–Hanai (BH) mixture models] to extract cell parameters lose their accuracy. Moreover, variations in the cell position relative to the measurement electrodes decrease the accuracy of the analytical solutions. Impedance spectrum of a typical eukaryotic mammalian cell is generated for different geometrical configurations using finite element. The generated data are fitted to the analytical models and extracted cell parameters are compared with the original values. The results show that BH model works more effectively when chamber to cell radius ratio is <3.5 and chamber height to cell radius ratio is <3. Moreover, it is observed that analytical models estimate cell parameters with major errors when the cells are in the vicinity of the electrodes. However, for high‐volume fraction simulations, the BH model was able to predict cell parameters better even in the vicinity of the electrodes. [ABSTRACT FROM AUTHOR]

This work reports the first of its kind custom implantable cathodic voltage controlled electrical stimulator (iCVCES) for use with implanted orthopaedic devices. The iCVCES allows researchers to study DC cathodic voltage controlled electrical stimulation (CVCES) in vivo with no percutaneous leads. The iCVCES is a microcontroller‐based potentiostat circuit with wireless (bluetooth) communication that controls the DC cathodic stimulation and monitors the environment around the implant. Comprising a single PCB with a coin cell battery, the device is able to hold a constant voltage as large as −1.8 V in a dynamic impedance environment. In vitro tests demonstrate functionality comparable to bench‐top systems, and in vivo tests demonstrate operation in live rats, for up to 8 days, with the ability to provide constant stimulation with a maximum variation of 2 mV. [ABSTRACT FROM AUTHOR]

We report how the impedance presented by a platinum electrode scales with the concentration of phosphate buffered saline (PBS). We measure the response in various dilutions of PBS with an electrode array as is commonly used in spinal cord stimulator (SCS) implants. We match the parameters of a non-linear electrode-electrolyte interface model to these measurements. We find that the constant phase element of the model scales with approximately the log of concentration, whereas the resistivity is inversely proportional. Using a novel DC measurement technique we show that the onset of Faradaic conduction for a platinum electrode, and thus the safe exposure limit, does not scale with concentration. We compare objective measurements made in saline to those made in the spinal cavity of live sheep. We comment upon the appropriateness of using PBS as a substitute for in-vivo measurements. [ABSTRACT FROM PUBLISHER]

The cuff electrode provides a stable interface with the peripheral nerve, which has been widely utilized in both basic research and clinical practice over the past few decades. In this paper, we present a microfabricated, parylene-based self-locking cuff electrode. The cuff diameter can be adjusted to accommodate the nerve properly during implantation. This type of cuff electrodes is easy to implant and the cuff was made of the thin, flexible, and biocompatible parylene substrate. Moreover, the integrated parylene cable and pads facilitate the connection with external circuits. Electrochemical properties of electrode sites were characterized by impedance spectroscopy and cyclic voltammetry. The average impedance magnitude and average charge delivery capacity of the Pt electrodes are 8.3 kQ (at 1 kHz) and 2.8 mC/cm2, respectively. Using the proposed cuff electrodes, the evoked compound action potentials of the rat sciatic nerve were successfully recorded. Electrical stimulation tests proved the feasibility of selective stimulation of tibial and peroneal fascicles within the rat sciatic nerve. This type of cuff electrodes induced only a benign foreign body reaction and did not damage the axons within the rat sciatic nerve over 11 weeks of an implantation period. [ABSTRACT FROM AUTHOR]

We introduce a new 3-D flexible microelectrode array for high performance electrographic neural signal recording and stimulation. The microelectrode architecture maximizes the number of channels on each shank and minimizes its footprint. The electrode was implemented on flexible polyimide substrate using microfabrication and thin-film processing. The electrode has a planar layout and comprises multiple shanks. Each shank is three mm in length and carries six gold pads representing the neuro-interfacing channels. The channels are used in recording important precursors with potential clinical relevance and consequent electrical stimulation to perturb the clinical condition. The polyimide structure satisfied the mechanical characteristics required for the proper electrode implantation and operation. Pad postprocessing technique was developed to improve the electrode electrical performance. The planar electrodes were used for creating 3-D “Waterloo Array” microelectrode with controlled gaps using custom designed stackers. Electrode characterization and benchmarking against commercial equivalents demonstrated the superiority of the Flex electrodes. The Flex and commercial electrodes were associated with low-power implantable responsive neuro-stimulation system. The electrodes performance in recording and stimulation application was quantified through in vitro and in vivo acute and chronic experiments on human brain slices and freely-moving rodents. The Flex electrodes exhibited remarkable drop in the electric impedance (100 times at 100 Hz), improved electrode-electrolyte interface noise (dropped by four times) and higher signal-to-noise ratio (3.3 times). [ABSTRACT FROM AUTHOR]

We describe the construction of a model of the electrode-electrolyte interface and surrounding electrolyte in the case of a platinum-electrode array intended for spinal-cord stimulation (SCS) application. We show that a finite, two-dimensional, resistor array provides a satisfactory model of the bulk electrolyte, and we identify the complexity required of that resistor array. The electrode-electrolyte interface is modelled in a fashion suitable for commonly-available, compact simulators using a nonlinear extension of the model of Franks (IEEE Trans. Biomed. Eng., vol. 52 , no. 7 , pp. 1295–1302, Jul. 2005) that incorporates diodes and a memristor. The electrode-electrolyte interface model accounts for the nonlinear current-overpotential characteristic and diffusion-limiting effects. We characterise a commercial, implantable, electrode array, fit the model to it, and show that the model successfully predicts subtle operational characteristics. [ABSTRACT FROM PUBLISHER]

Previous studies have indicated that electrodes placed between fascicles can provide nerve recruitment with high topological selectivity if the areas of interest in the nerve are separated with passive elements. In this study, we investigated if this separation of fascicles also can provide topologically selective nerve recordings and compared the performance of mono-, bi-, and tripolar configurations for stimulation and recording with an intra-neural interface. The interface was implanted in the sciatic nerve of 10 rabbits and achieved a median selectivity of Ŝ=0.98-0.99 for all stimulation configurations, while recording selectivity configurations was in the range of Ŝ=0.70-0.80 with the monopolar configuration providing the lowest and the average reference configuration the highest recording selectivity. Interfascicular electrodes could provide an interesting addition to the bulk of peripheral nerve interfaces available for neural prosthetic devices. The separation of the nerve into chambers by the passive elements of the electrode could ensure a higher selectivity than comparable cuff electrodes and the intra-neural location could provide an option of targeting mainly central fascicles. Further studies are, however, still required to develop biocompatible electrodes and test their stability and safety in chronic experiments. [ABSTRACT FROM AUTHOR]

A novel microdevice for electrical impedance spectroscopy is presented to differentiate between normal and cancerous cells at the single cell level with a high sensitivity. The device utilizes a microfluidic tunnel structure, whose height is smaller than the cell diameters, to squeeze the target cells. Thus, the tight contact between the cells and electrodes allows the device to measure the intrinsic electrical properties of the cells with a higher sensitivity than through noncontact methods. Three-dimensional interdigitated electrodes (3-D IDE) are also employed to confine most of the electric field into the cell membrane, which contains the meaningful electrical properties. Consequently, the variance of the measured values could be reduced because the position of target cells is almost the same in every cell assay. The device well distinguishes normal human breast cells (MCF-10A) from early-stage human breast cancer cells (MCF-7) by means of electrical impedances at 500 kHz; the average differences of the real part and phase angle between the target cells are 44.4 and 1.41 , respectively. The proposed device also shows a high repeatability for the deionized (DI) water test conducted before and after each cell assay; the variances of the real part and phase angle of electrical impedance at 500 kHz are as small as 9.07 and 0.27 , respectively. [ABSTRACT FROM PUBLISHER]

Electrical stimulation of arm and hand muscles can be a functional tool for patients with motor dysfunction. Sufficient stimulation of finger and thumb musculature can support natural grasping function. Yet it remains unclear how different grasping movements can be selectively supported by electrical stimulation. The goal of this study is to determine to what extent activation of individual fingers is possible with surface electrical stimulation for the purpose of rehabilitation following stroke. The extensor digitorum communis (EDC) muscle, flexor pollicis longus (FPL) muscle, and the thenar muscle group, all involved in grasp and release, were selected for stimulation. The evoked forces in individual fingers were measured. Stimulation thresholds and selective ranges were determined for each subject. Electrode locations where the highest selective range occurred were compared between subjects and influences of different isometric wrist positions were assessed. In all subjects selective stimulation of middle finger extension and thumb flexion was possible. In addition, selective stimulation of index and ring finger extension was possible in most cases. In nine out of the ten EDC subjects we were able to stimulate three or all four fingers selectively. However, large variability in electrode locations for high selectivity was observed between the subjects. Within the designs of grasping prostheses and grasping rehabilitation devices, the variability of electrode locations should be taken into account. The results of our study facilitate the optimization of such designs and favour a design which allows individualized stimulation locations. [ABSTRACT FROM AUTHOR]

The brain-computer interface (BCI) system has been developed to assist people with motor disability. To make the system more user-friendly, it is a challenge to reduce the electrode preparation time and have a good reliability. This study aims to find a minimal set of electrodes for an individual stroke subject for motor imagery to control an assistive device using functional electrical stimulation for 20 sessions with accuracy higher than 90%. The characteristics of this minimal electrode set were evaluated with two popular algorithms: Fisher's criterion and support-vector machine recursive feature elimination (SVM-RFE). The number of calibration sessions for channel selection required for robust control of these 20 sessions was also investigated. Five chronic stroke patients were recruited for the study. Our results suggested that the number of calibration sessions for channel selection did not have a significant effect on the classification accuracy. A performance index devised in this study showed that one training day with 12 electrodes using the SVM-RFE method achieved the best balance between the number of electrodes and accuracy in the 20-session data. Generally, 8-36 channels were required to maintain accuracy higher than 90% in 20 BCI training sessions for chronic stroke patients. [ABSTRACT FROM AUTHOR]

A new form of deep brain stimulation (DBS) electrode was proposed that was made of carbon nanotube yarns (CNTYs). Electrode interface properties were examined using cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS). The CNTY electrode interface exhibited large charge storage capacity (CSC) of 12.3 mC/cm2 which increased to 98.6 mC/cm2 after acid treatment, compared with 5.0 mC/cm2 of Pt-Ir. Impedance spectrum of both untreated and treated CNTY electrodes showed that finite diffusion process occurred at the interface due to their porous structure and charge was delivered through capacitive mechanism. To evaluate stability electrical stimulus was exerted for up to 72 h and CV and EIS results of CNTY electrodes revealed little alteration. Therefore CNTY could make a good electrode material for DBS. [ABSTRACT FROM AUTHOR]

Development of drugs requires electrophysiological studies of small animals like mice, rats or guinea pigs. Electrocardiography (ECG) of hirsute animals is time-consuming. We have developed a micro magnetometer array with a 9-channel superconducting quantum interference device (SQUID) with a 2.5-mm diameter pickup-coil for noncontacting measurement of magnetocardiograms (MCGs) in small animals. The micro-MCG successfully recorded the PQRST complex in mice, rats and guinea pigs. A regional myocardial injury was made in rat hearts with a cryoinjury probe, and the characteristic pattern of the injury was recorded in the MCG. An anterior myocardial injury created a QS pattern in the MCG, and a posterior myocardial injury created a QR pattern in the MCG. Quinidine-induced QT prolongation was successfully detected by micro-MCG in mice and rats. Simultaneous recording of ECG and MCG was conducted after intraperitoneal administration of quinidine (60 mg/kg) in guinea pigs. QT interval corrected for heart rate (QTc) in both ECG and MCG correlated well. The newly developed micro-MCG may facilitate electrophysiological studies of small animals, and may enable high-throughput screening of drug-induced QT abnormality. [ABSTRACT FROM PUBLISHER]

A biocompatible neural microprobe constructed using well-established SU-8 microfabrication techniques is described that was designed to record fiber spike signals from regenerated axons within peripheral nerves. These microprobes features bipolar longitudinal gold electrodes recessed below the surface within ldquogroovesrdquo designed to guide the growth of regenerating axons along the length of the grooves and limit the number of fibers that come in contact with the longitudinal electrodes. In addition, screening microprobe toxicity using cultures of human skin fibroblasts, the biocompatibility of these SU-8 microprobes for neural interface applications, in particular, was specifically verified using primary cultures of two sensitive cell types found in peripheral nerves: purified Schwann cells and explanted dorsal root ganglion (DRG) neurons and their fibers. The SU-8 microprobes were surgically implanted into transected rat Sciatic nerves within a unique peripheral nerve regeneration tube. Long-term fiber spike signals were recorded with these SU-8 microprobes in 13 chronically implanted rats for periods from 4 to 51 weeks without any signs of tissue damage or inflammatory reaction. [ABSTRACT FROM PUBLISHER]

A platform for high spatial and temporal resolution electrophysiological recordings of in vitro electrogenic cell cultures handling 4096 electrodes at a full frame rate of 8 kHz is presented and validated by means of cardiomyocyte cultures. Based on an active pixel sensor device implementing an array of metallic electrodes, the system provides acquisitions at spatial resolutions of 42 mum on an active area of 2.67 mm times 2.67 mm, and in the zooming mode, temporal resolutions down to 8 mus on 64 randomly selected electrodes. The low-noise performances of the integrated amplifier (11 muVrms) combined with a hardware implementation inspired by image/video processing concepts enable high-resolution acquisitions with real-time preprocessing capabilities adapted to the handling of the large amount of acquired data. [ABSTRACT FROM PUBLISHER]

To fully exploit the recording capabilities provided by current and future generations of multi-electrode arrays, some means to eliminate the residual charge and subsequent artifacts generated by stimulation protocols is required. Custom electronics can be used to achieve such goals, and by making them scalable, a large number of electrodes can be accessed in an experiment. In this work, we present a system built around a custom 16-channel IC that can stimulate and record, within 3 ms of the stimulus, on the stimulating channel, and within 500 mus on adjacent channels. This effectiveness is achieved by directly discharging the electrode through a novel feedback scheme, and by shaping such feedback to optimize electrode behavior. We characterize the different features of the system that makes such performance possible and present biological data that show the system in operation. To enable this characterization, we present a framework for measuring, classifying, and understanding the multiple sources of stimulus artifacts. This framework facilitates comparisons between artifact elimination methodologies and enables future artifact studies. [ABSTRACT FROM PUBLISHER]

Time-frequency domain signal processing of neural recordings, from high-density microelectrode arrays implanted in the cortex, is highly desired to ease the bandwidth bottleneck associated with data transfer to extra-cranial processing units. Because of its energy compactness features, discrete wavelet transform (DWT) has been shown to provide efficient data compression for neural records without compromising the information content. This paper describes an area-power minimized hardware implementation of the lifting scheme for multilevel, multichannel DWT with quantized filter coefficients and integer computation. Performance tradeoffs and key design decisions for implantable neuroprosthetics are presented. A 32-channel 4-level version of the circuit has been custom designed in 0.18-mum CMOS and occupies only 0.22 mm2 area and consumes 76 muW of power, making it highly suitable for implantable neural interface applications requiring wireless data transfer. [ABSTRACT FROM PUBLISHER]

Persons with spinal cord injury (SCI) can benefit significantly from functional neuromuscular stimulation (FNS) systems for standing if manual tasks can be performed while upright. Using FNS to sufficiently activate the knee extensors to rise from a sitting position often results in inadvertent activation of the rectus femoris and/or sartorius, which flex the hip. In this study, intramuscular electrodes implanted in the vastus lateralis and medialis of four subjects with SCI were used to activate these muscles individually and simultaneously to measure knee extension moment. Support forces applied to the arms and feet were measured while upright to quantify the effects of recruiting rectus femoris and/or sartorius. In three of the four subjects, vastus lateralis, by itself, generated adequate knee extension moment for rising from a chair and to maintain static standing. Simultaneous activation of the vastus lateralis and medialis using a bifurcated electrode generated adequate knee extension moment in one subject, and was within 10% of the required moment in another. While upright, activation of the rectus femoris resulted in arm support force increases of 4-11% body weight, while deactivation resulted in arm support force decreases of 6-9% body weight. The results indicate that selective activation of the vastus lateralis, individually or in combination with vastus medialis, can improve current FNS standing systems by reducing the arm support forces required to remain upright [ABSTRACT FROM PUBLISHER]

Magnetic resonance electrical impedance tomography (MREIT) measures the z‐component of magnetic flux density B = (Bx, By, Bz) induced by externally injected current through a pair of electrodes. MREIT visualises in‐vivo electrical current density and/or conductivity distribution in a three‐dimensional imaging object from the measured magnetic flux density Bz. MREIT techniques typically use the phase difference approach in an interleaved encoding scheme by the injection of positive and negative currents to cancel systematic phase artefacts. Developed is a method to measure Bz data using only a single scan by the injection of one current, avoiding the interleaved encoding scheme. The method separates measured multiple k‐space lines into acquired k‐space lines with and without injection currents and develops an algorithm to measure the magnetic flux density Bz using acquired k‐space lines by the injecting current. Results from phantom experiments demonstrate that the method has potential to measure magnetic flux density using only a single scan by the injection of one current. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate a “suture” type electrode for direct bladder stimulation in an animal model of a lower motor neuron lesion. During an initial surgery, 5 male cats were instrumented under anesthesia using multistranded, 316 LVM, stainless-steel, wire electrodes implanted on the bladder wall serosa above the trigone area. Electrodes were constructed with a needle attached to the end that was removed after suturing the electrode in place. Additional instrumentation included urinary bladder catheters (tubes) for pressure recording and filling, and hook type electrodes for leg and pelvic floor electromyography recording. Chronic bladder filling and stimulation studies were conducted in tethered animals 3 to 4 weeks following surgery. To test these electrodes in a spinal cord injury model, a lower motor neuron lesion was performed including the sacral cord and complete nerve roots at L6 and below. These animals were evaluated during weeks 3 and 10 after injury. Direct bladder stimulation induced active contractions and voiding both before and after spinal cord injury. Effective stimulation parameters consisted of 40 pulses per s, 300 μs to 1 ms pulse duration, a stimulation period from 3 to 4 s, and a stimulation current from 10 to 40 mA. Fluoroscopy revealed an open membranous urethra during stimulation and following stimulation. A small diameter penile urethra was observed to limit flow. Postmortem evaluation of the suture electrode revealed no abnormalities such as corrosion, migration into the bladder lumen or displacement. These findings indicate that suture electrodes are suitable and effective for short-term implantation in the lower motor neuron animal model [ABSTRACT FROM PUBLISHER]

In an effort to assess the safety and efficacy of focal intracortical microstimulation (ICMS) of cerebral cortex with an array of penetrating electrodes as might be applied to a neuroprosthetic device to aid the deaf or blind, the authors have chronically implanted 3 trained cats in primary auditory cortex with the 100-electrode Utah Intracortical Electrode Array (UIEA). Eleven of the 100 electrodes were hard-wired to a percutaneous connector for chronic access. Prior to implant, cats were trained to “lever-press” in response to pure tone auditory stimulation. After implant, this behavior was transferred to “lever-presses” in response to current injections via single electrodes of the implanted arrays. Psychometric function curves relating injected charge level to the probability of response were obtained for stimulation of 22 separate electrodes in the 3 implanted cats. The average threshold charge/phase required for electrical stimulus detection in each cat was, 8.5, 8.6, and 11.6 nC/phase respectively, with a maximum charge/phase of 26 nC/phase and a minimum of 1.5 nC/phase thresholds were tracked for varying time intervals, and 7 electrodes from 2 cats were tracked for up to 100 days. Electrodes were stimulated for no more than a few minutes each day. Neural recordings taken from the same electrodes before and after multiple electrical stimulation sessions were very similar in signal/noise ratio and in the number of recordable units, suggesting that the range of electrical stimulation levels used did not damage neurons in the vicinity of the electrodes. Although a few early implants failed, the authors conclude that ICMS of cerebral cortex to evoke a behavioral response can be achieved with the penetrating UIEA. Further experiments in support of a sensory cortical prosthesis based on ICMS are warranted [ABSTRACT FROM PUBLISHER]

In‐vivo electromagnetic field distributions of biological systems can be imaged from the measured magnetic flux density of magnetic resonance‐based electrical impedance tomography (MREIT), which was induced by the externally injected current through a pair of electrodes. Since the electromagnetic field is affected by the injected current and electrical conductivity of biological tissues, the electrode type and position are important factors for determining the voltage and current density distribution. Using a three‐dimensional finite element model, the current pathway and electric field distribution to optimise the electrode configurations in liver MREIT are estimated. [ABSTRACT FROM AUTHOR]

A novel three‐dimensional (3D) electrical impedance mammography (EIM) system, named the combined EIM (CEIM) system, is introduced. It combines a ring electrode array with a planar electrode array that can operate independently or together. Three operational modes of the CEIM system are presented. Using a close‐to‐realistic digital breast phantom, the CEIM system is shown to provide enhanced detectability of a tumour deep within the tissue, as required for a large‐volume breast. An implicit comparison with the authors' former MK4 system demonstrates the benefits of this integrated multimode mammography system. [ABSTRACT FROM AUTHOR]

Presented is a methodology of conversion of a conventional colour measure, e.g. 24‐bit colour, to a neuromorphic representation for use with epiretinal prostheses. The conversion implemented, for a 4 by 4 image, within a field programmable gate array outputs three groups of timing signals. These three groups correspond to red (R), green (G) and blue (B) colour channels. In future work the channels will input to a retinal implant stimulator, via a receiver chip housed over the earlobe of a prosthesis recipient, to form biphasic pulses to drive electrodes stimulating the axons of colour specific retinal ganglion cells. A test setup was used to encode the hue pulses back to intensity to display test images on a VGA monitor for validation. [ABSTRACT FROM AUTHOR]

Nonthermal irreversible electroporation (NTIRE) is an emerging tissue ablation modality that may be ideally suited in developing a decellularized tissue graft. NTIRE utilizes short electric pulses that produce nanoscale defects in the cell membrane lipid bilayer. The electric parameters can be chosen in such a way that Joule heating to the tissue is minimized and cell death occurs solely due to loss in cell homeostasis. By coupling NTIRE with the body's response, the cells can be selectively ablated and removed, leaving behind a tissue scaffold. Here, we introduce two different methods for developing a decellularized arterial scaffold. The first uses an electrode clamp that is applied to the outside of a rodent carotid artery and the second applies an endovascular minimally invasive approach to apply electric fields from the inner surface of the blood vessels. Both methods are first modeled using a transient finite element analysis of electric and thermal fields to ensure that the electric parameters used in this study will result in minimal thermal damage. Experimental work demonstrates that both techniques result in not only a decellularized arterial construct but an endothelial regrowth is evident along the lumen 7 days after treatment, indicating that the extracellular matrix was not damaged by electric and thermal fields and is still able to support cell growth. [ABSTRACT FROM AUTHOR]