Image-Guided 256-Element Phased-Array Focused Ultrasound Surgery

High-intensity focused ultrasound (HIFU) has been testified as a promising surgical modality to ablate deepseated tumors noninvasively and precisely [1]?[4]. The faster pace of the advanced HIFU technology owes a great deal to the sufficiently sophisticated imaging techniques and the significant advancements in high-power ultrasound transducers, which now allow the focused ultrasound surgery system to be more reliable and precise [1]?[7]. The early pioneer work in the clinical trials and HIFU clinical equipment carried out by the researchers in China (Chongqing, Beijing, and Shanghai) are valuable and encouraging in the world of HIFU [8]. The ultrasound- guided equipment of the JC HIFU systemhas been put into clinical trials, both in China and Oxford, United Kingdom [9]. Now, a variety of tumors such as those in the liver, breast, kidney, and pancreas as well as the uterine fibroids and osteosarcoma are treated clinically with focused ultrasound surgery [8]?[12].     

Energy-Based Diagnostic and Treatment Techniques

In living systems, numerous biochemical reactions take place, including energy and entropy variations. Understanding how energy flows and interacts with the surrounding tissues may provide some insights into tumor initiation and development and, thus, lay the foundation for early cancer diagnosis and treatment using energy-based technologies. For example, previous research showed that the internal temperature of breast cancer was 2?3 C higher than that of normal tissue mainly due to the higher metabolic rate and local blood perfusion [1]?[3]. This has been the biological basis for noninvasive breast cancer detection using infrared thermal imaging techniques. Also tumor cells and neo-vasculature were found to be more sensitive to temperature than normal vessels, providing the possibility of thermally targeted drug delivery for tumor therapy [4]?[10]. Thermal treatment     

Cortical Spreading Depression in Rats

Cortical spreading depression (CSD) is an important neurophysiological phenomenon, which was first discovered more than 60 years ago [1]. As it is associated with migraine and focal cerebral ischemia, CSD has attracted intensive attention [2]?[5]. Various methodologies including positron emission tomography [6], magnetic resonance imaging (MRI) [7], laser Doppler flowmetry (LDF) [8], and autoradiography have been used to investigate CSD. Optical intrinsic signal imaging (OISI) is a neuroimaging technique that can monitor a large region of the cortex with both higher temporal and spatial resolution [9]?[11].     

The windmill topology

A widely used 18-pulse clean power converter with windmill transformer topology is presented and analyzed. It provides a more economical solution to achieve harmonicmitigation in electric power systems when compared with some of the earlier methods. With the proliferation of nonlinear loads in industrial power systems, the advent of IEEE 519-1992 [1], and the increasing demand by utilities for power factor improvement, the specification of harmonic mitigation has become common [2], [3]. In the past 14 years, several patented 18-pulse converter methods have been accepted in the marketplace and are successfully applied in a variety of practical applications such as water management, oil field installations, etc., where adjustable speed drive (ASD) and harmonic mitigation are required. A threeto nine-phase unity-gain autotransformer topology with a ±20° phase shift between output voltages is first proposed in [4]. The step-up and step-down 18-pulse autotransformer topologies with a 40° phase shift between the output voltages are discussed in [5]?[9]. The winding current looping and sharing problems in early days have already been solved [10]. The challenging design problem becomes one of economics [11].     

Retinal neurostimulator for a multifocal vision prosthesis.

A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator forms part of a vision prosthesis, designed to restore vision to patients who have lost their sight due to retinal diseases such as retinitis pigmentosa and macular degeneration. For charge balance, the neurostimulator was designed to stimulate with current sources and sinks operating together, and with the ability to drive a hexagonal mosaic of electrodes to reduce the electrical crosstalk that occurs when multiple bipolar stimulation sites are active simultaneously. A hexagonal mosaic of electrodes surrounds each stimulation site and has been shown to effectively isolate each site, increasing the ability to inject localized independent charge into multiple regions simultaneously.     

Autonomic neural control of cerebral hemodynamics

Despite the rich innervation of the cerebral vasculature by both sympathetic and parasympathetic nerves [1], the role of autonomic control in cerebral circulation and, particularly, cerebral hemodynamics is not entirely clear [2]. Previous animal studies have reported inconsistent results regarding the effects of electrical stimulation or denervation on cerebral blood flow (CBF), cerebral pressureflow relationship, and cerebral vessel response to metabolic stimuli [3]--[5]. Moreover, with the advance of transcranial Doppler ultrasound (TCD), which yields accuratemeasurements of CBF velocity (CBFV) with high time resolution [6], it has been found that in humans CBFV in the middle cerebral artery decreased substantially during lower body negative pressure (LBNP) and head-up tilt in the absence of systemic hypotension, which suggests the presence of cerebral vasoconstriction associated with augmented sympathetic nerve activity during orthostatic stress [7]. These observations were based on assessing static measures of cerebral circulation, i.e., mean values of artevial blood pressure (ABP) and CBF with a low time resolution.     

Emerging Technologies

One of the most promising medical device therapies is neurostimulation. Advances in implantable device technologies make it now possible for patients suffering from a wide array of debilitating neurological conditions to receive adequate treatment. Implantable neurostimulation systems include cochlear implants, cortical stimulators, deep brain stimulators (DBSs), gastric nerve stimulators, spinal cord stimulators (SCSs), and vagus nerve stimulators (VNSs). Neurostimulation currently treats several debilitating conditions, including major treatmentresistant depression, epilepsy, gastroparesis, hearing loss, incontinence, chronic, untreatable pain, Parkinson disease, essential tremor, and dystonia [1]?[3].     

Nanocomposites-a review of electrical treeing and breakdown

Polymer nanocomposites are composite materials having several wt% of inorganic particles of nanometer dimensions homogeneously dispersed into their polymer matrix. This new type of polymer composite has recently drawn considerable attention because nanocomposites or nanostructured polymers have the potential of improving the electrical, mechanical, and thermal properties as compared to the neat polymers [1]. Polymer nanocomposites are, among other applications, increasingly desirable as coatings, structural, and packaging materials in a wide range of automobile, civil, aerospace, and electrical engineering applications. Also, nanocomposites find applications in medical services, healthcare, and decorative coloring [2], [3]. These new materials show excellent mechanical properties such as high tensile strength, increased hardness and toughness, improved flexural strength modulus, and greater heat and chemical resistance. Polymer nanocomposites are characterized by an enormously large interfacial surface area between the inorganic particles and the polymer matrix into which they are embedded. This ratio is typically more than two orders of magnitude greater than that in traditional microcomposite materials. The percentage by weight of the nanoparticles is usually quite low because of the low nanoparticle percolation threshold, particularly for the commonly used platelet and nanotube particles [4]. However, when the nanoparticle content increases beyond the percolation threshold, the nanocomposite may loose its beneficial properties [5]. Various polymers such as polyamide (PA), polyethylene (PE), polypropylene (PP), ethylene vinyl acetate (EVA), epoxy resin (EP), and silicone rubber (SiR) can be combined with inorganic particles such as layered silicate (LS), silica (SiO2), titania (TiO2), alumina (Al2O3), and magnesia (MgO) [1], and there are a number of papers that describe the tests and the properties of the aforementioned combinations of materials [6]?[10].     

Pushing the limits of artificial vision

The field of neural prostheses has made significant strides toward restoring damaged or lost nervous system function for millions of people. These advances have led to the development of selective electrical interfaces that communicate directly with nerve cells to modulate neural processes rationally. The first neural prosthesis developed was the cardiac pacemaker, which has become pervasive in society. The pacemaker also provides the promise that such an approach can address higher order neural dysfunctions. Technologies borrowed from the semiconductor industry have allowed researchers to micro fabricate devices with active elements on the length scale of nerve cells. This size capability has led to the development of the cochlear implant, which has restored hearing in thousands of deaf patients. Restoring more complex sensory functions, such is vision, provides greater engineering challenges, but achieving them is within our grasp. Current approaches to achieving artificial vision are discussed, along with strategies being used to push the capability limits of these prostheses even further.     

Cellular/Tissue Engineering

Self-repair capacity of the adult skeletal muscle is deficient in its ability to restore significant tissue loss caused by traumatic injury, congenital defects, tumor ablation, prolonged denervation, or functional damage due to a variety of myopathies [1], [2]. Conventional surgical treatments including local or distant autologous muscle transposition yield a limited degree of success [2]. Alternatively, transplantation of exogenous myogenic cells (satellite cells and myoblasts) has been proposed to increase the regenerative capacity of skeletal muscle [3]. However, the clinical outcomes from intramuscular injection of allogeneic myoblasts were compromised by numerous limitations, including poor cell retention and survival, as well as immunorejection [3], [4]. Studies of other muscle-derived stem cells [5] and genetically modified myoblasts [6] are currently in progress, for their ability to overcome these limitations and improve therapeutic efficacy.     

Reliability and statistical lifetime- prognosis of motor winding insulation in low-voltage power drive systems

Today, more and more complex power drive system (PDS) applications are being used in which an arbitrary number of inverters with different, autonomous drive frequencies are connected to a single dc bus. If long feeder cables, different inverter output circuits, and unfavorable grounding conditions simultaneously occur, then electrical oscillations with high peak values of the voltage between the motor terminals and ground may be generated. Occasionally, these can exceed the peak values of the generally better known mechanism of traveling waves [1], [2]. The complex design of recent drive systems requires more knowledge about the interaction of the components being used in the system and of the resulting effects. This knowledge forms the basis for the design of reliable drive systems. One of the major reliability topics for variable-speed power drive systems has long been the lifetime of the winding insulation system. The winding insulation system may manifest partial discharge (PD) because the electrical stress is higher for these systems than it is for drive systems that are directly connected to the line supply [1]?[4]. In the classic approach (see Figure 1) [4], [5], it is assumed that the peak voltages stressing the insulation system of the motor winding would be more or less constant and the PD inception voltage of the winding insulation would also be a deterministic value. From this, it is derived that an adequate lifetime can only be achieved by ensuring operation without PD. In case of operation with PD, the lifetime would be reduced to an unacceptable level. The approach presented in this paper considers both the generation of peak voltages, which stress the winding insulation system, as well as the associated stochastic PD inception behavior. This results in a statistically-based insulation coordination and a reliability-based economic design of the complete drive system (see Figure 2).     

Assessing experiences of international students in Haiti and Benin

The past two decades have seen an increase in international experiences for engineering students focused on service and research in developing countries. Motivation for these programs reflects the growing recognition that there is a need for creating engineers with greater global awareness [18] who are familiar with the need for integrating solutions to complex problems through interdisciplinary approaches [12]. Of particular interest have been programs in humanitarian engineering that address these needs while at the same time contributing to the attractiveness of engineering, helping to bridge the gender gap that has challenged engineering education, and providing new opportunities to see engineering in a broader global/ethical realm [3], [11], [12], [14], [16], [30].     

A biomimetic retinal stimulating array.

A retinal prosthesis capable of restoring face recognition, reading, and mobility to blind patients is within the capability of microsystems technology. Electrode arrays can be made dense enough to be able to place thousands of pixels into the macula. Electrode materials can supply safe and effective stimulus current. This review examines some prior work in electrical stimulation of the retina and simulations of phosphene-based vision as a basis to produce design constraints for a biomimetic retinal-stimulating array. An array is designed considering the needs of the end users (blind individuals), the biology of diseased retina, and the limits of electrode technology. Other technology to support the system such as high-density stimulus generation circuitry and hermetic packaging face significant challenges but solutions can likely be realized to some degree.     

Electronic design of a multichannel programmable implant for neuromuscular electrical stimulation.

An advanced stimulator for neuromuscular stimulation of spinal cord injured patients has been developed. The stimulator is externally controlled and powered by a single encoded radio frequency carrier and has four independently controlled bipolar stimulation channels. It offers a wide range of reprogrammability and flexibility, and can be used in many neuromuscular electrical stimulation applications. The implant system is adaptable to patient's needs and to future developments in stimulation algorithms by reprogramming the stimulator. The stimulator is capable of generating a wide range of stimulation waveforms and stimulation patterns and therefore is very suitable for selective nerve stimulation techniques. The reliability of the implant has been increased by using a forward error detection and correction communication protocol and by designing the chip for structural testability based on scan test approach. Implemented testability scheme makes it possible to verify the complete functionality of the implant before and after implantation. The stimulators architecture is designed to be modular and therefore its different blocks can be reused as standard building blocks in the design and implementation of other neuromuscular prostheses. Design for low-power techniques have also been employed to reduce power consumption of the electronic circuitry.     

Possible indicators of aging in oil-filled transformers part 1: measurements

Degradation model development using basic research, and remaining life estimation, are essential for modern electrical engineering aging-asset management programs [1]. A CIGRE report [2] presents in detail the different aging factors and models, mechanisms of failure, condition-assessment and diagnostic techniques, and life assessment and extension methods.     

As Singular as a Delta Function? [Microwave Surfing]

I am sure that many readers of Lucky's column share his trepidations (as I do) when it comes to making sense of quantum electrodynamics. Even P.A.M. Dirac (1902-1984), who shared the Nobel Prize for physics with Schr?dinger in 1933, might have commiserated. Dirac (who received his first undergraduate degree in electrical engineering) felt that the quantum world could not be described in words or represented as images. To draw its picture would be "like a blind man sensing a snowflake. One touch and it's gone" [2]. He remarked on this challenge even in his Nobel Banquet Speech [3] of December 10, 1933: "But the physicist is at a disadvantage in this respect on account of the very specialized nature of his work, which cannot be made intelligible without an intensive preliminary course of study."     

Precision farming practices

In the past decade, farmers around the globe have witnessed what some consider an agricultural revolution. Driven by economic and environmental pressures, precision agriculture has emerged as a flurry of technological enhancements to traditional farm machinery and management tools [1]-[3]. One does not have to closely examine a field to notice that the crop often thrives in certain areas while growing poorly in others. An intuitive approach to addressing this problem is to apply different amounts of seed, fertilizer, or other inputs according to the specific needs of the particular area of the field. For a very small field, manual control of inputs may be possible; however, for larger fields, this approach is unrealistic, if not impossible. Furthermore, this approach is subjective because control decisions are based on the operator?s opinion and have no quantitative basis. In recent years, several technologies have emerged and made their way into the agricultural realm. These technologies provide the basis to realize the precision farming vision and to objectively manage agricultural land according to its spatially variable needs. Traditionally, whole-field application rates of inputs such as fertilizer and pesticide have been determined according to the maximum needs within a field. Precision farming practices significantly improve farm production in terms of net profit and limit environmental pollution potential.     

Switching Current Measurements in Pb(Zn1/3 Nb2/3)O3-PbTiO3 Relaxor Ferroelectric Single Crystals

Switching current measurements have been carried out on relaxor ferroelectric single crystal-PZN, and the solid solution 0.86PZN-0.04PT and 0.91PZN-0.09PT for crystallographic directions [001] and [111]. The experiments showed the presence of two maximum points in the switching current for 0.86PZN-0.04PT and 0.91PZN-0.09PT that can be attributed to the co-existence of two phases. The switching time inverse shows a two-fold linear dependence on applied field for both [001] and [111]. This suggests that the polarization reversal in the relaxor systems is related to the mobility of the domains. The switching time in relaxor ferroelectric is long (millisecs) compared to the reported data on normal ferroelectric Barium titanate (microsecs). The switching time is dependent on the composition of the crystal along both [001] and [111]. Along [111], the switching time decreases as the PT component increases in the crystal while along [001], the switching time increases as the PT increases.     

Development of restoration system based on human performance model

A stable power supply is required from power systems as the importance of electrical energy increases. Particularly, in the case of high-voltage systems (500-, 275-, 154-kV bulk power systems), this requirement is high. However, there are cases when power system faults cannot be avoided. Accordingly, it is very important to restore power systems quickly and safely if these failures occur. The characteristics of the power system restoration (its combinatorial aspects, use of knowledge from a wide variety of origins and of different types, number of criteria to satisfy) make it a difficult problem, for which the use of expert systems to generate restoration plans is being considered by many researchers, and promising results have already been obtained. However, most systems are still in the prototype stage [1]. One reason seems to be the lack of studies of a support system for knowledge-based behavior (unable to describe with any rule). This paper analyzes first power system restoration based on the human performance model [6] and discusses the knowledge-based behavior that is a high conceptual level of human performance to solve the problem from the combinatorial viewpoint. Then the application for the trunk line dispatching center is reported. Finally, the relations between knowledge-based behavior and the designed human interfaces are verified with a power networks restoration case-study.     

Sites of neuronal excitation by epiretinal electrical stimulation.

Action potentials arising from retinal ganglion cells ultimately create visual percepts. In persons blind from retinitis pigmentosa and age-related macular degeneration, viable retinal ganglion cells remain, and the retina can be stimulated electrically to restore partial sight. However, it is unclear what neuronal elements in the retina are activated by epiretinal electrical stimulation. This study investigated the effects of cellular geometry, electrode to neuron distance, stimulus duration, and stimulus polarity on excitation of a retinal ganglion cell with an epiretinal electrode. Computer-based compartmental models representing simplified retinal ganglion cell morphology provided evidence that the threshold for excitation was lower when an electrode was located in proximity to the characteristic 90 degrees bend in the axon of the retinal ganglion cell than when it was located over a passing axon of the nerve fiber layer. This electrode-position-dependent difference in threshold occurred with both cathodic and anodic monophasic stimuli, with point source and disk electrodes, at multiple electrode-to-neuron distances, and was robust to changes in the electrical properties of the model. This finding reveals that the physical geometry of the retinal ganglion cells produces stimulation thresholds that depend strongly on electrode position. The low excitation thresholds near the bend in the axon will result in activation of cells local to the electrode at lower currents than required to excite passing axons. This pattern of activation provides a potential explanation of how epiretinal electrical stimulation results in the production of punctuate, rather than diffuse or streaky phosphenes.