Large Coil Research Articles

Abstract W P71: Analysis of Large Volume Penumbra PC400 Coil and 025” ID Microcatheter in Treatment of Anterior Communicating Artery Aneurysm Embolization: Safety and Efficacy Outcomes from a Multicenter Experience

Purpose: We report clinical experience and long-term results in treating 39 AcomA aneurysms in 39 patients using the Penumbra PC400 large volume coil at 13 high volume centers. With its .020” coil size and use of 025” ID microcatheter, the safety and efficacy of the Penumbra Coil 400 (PC400) System in embolization of AcomA aneurysms has not yet been characterized. Methods: Our treatment cohort consisted of 39 aneurysms ranging between 3.5mm and 17mm, treated between March 2012 and May 2014. Six-month follow up were assessed. Data on angiographic results and procedural complications were collected prospectively and analyzed. Results: The mean aneurysm size was 6.2 mm, with 40.8% mean packing density. All aneurysms were treated entirely with PC400 coils, with mean of 5.1 coils placed. Twenty were ruptured and 19 unruptured. Sixty-six percent of the cases achieved an initial Raymond Scale of 1, and 23.7% achieved a Raymond scale of 2. The overall rate of retreatment was 0%, while the rate of morbidity and mortality caused by stroke <30 days was 1.8%. Comparison with a recently published meta-analysis showed similar or superior outcomes with lower procedural complication rates, most notably lower overall vasospasm rate of 6% vs 17% (p=0.023), lower retreatment rate of 0% vs 9% and higher long-term complete and near-complete occlusion of 96% vs 83% with PC400 coils (Tables 1, 2). Conclusion: ACE study data demonstrate that embolization using the PC400 System and 025” ID microcatheter in AcomA aneurysms leads to safe and effective short- and long-term outcomes.

1:27 PM, Abstract No. 40 - Experience using large volume detachable coils in the peripheral vasculature: preliminary results from the ACE multicenter study

Experience using large volume detachable coils in the peripheral vasculature: preliminary results from the ACE multicenter study C. Teigen, H. Moyle, R.S. Patel, A.M. Fischman, E. Kim, B. Baxter, S. Quarfordt, D. Heck, R. Klucznik, O. Diaz, A. Reeves, M. Abraham, E.J. Madarang, B. Zwiebel, M. Brant-Zawadzki, W. Peck, B. Nguyen, L. Whitaker, P.H. Gailloud, R.T. Hagino, K. Liu, J. Moskovitz, E. Luong, J. Lai, S.S. Kuo, S.S. Hak, N. Nguyen, A. Bose, S. Sit; Sanford Medical Center, Fargo, ND; Mount Sinai Medical Center, New York, NY; Erlanger Health System, Chattanooga, TN; Forsyth Medical Center, Winston-Salem, NC; The Methodist Hospital Research Institute, Houston, TX; University of Kansas Medical Center Research Institute, Kansas City, KS; Tampa General Hospital, Tampa, FL; Hoag Hospital, Newport Beach, CA; Johns Hopkins University, Baltimore, MD; Essentia Health, Duluth, MN; University of Virginia Health System, Charlottesville, VA; Florida Hospital, Orlando, FL; Penumbra, Inc., Alameda, CA

A Ferrite LTCC Based Dual Purpose Helical Antenna Providing Bias for Tunability

Typically, magnetically tunable antennas utilize large external magnets or coils to provide the magneto-static bias. In this work, we present a novel concept of combining the antenna and the bias coil in one structure. A helical antenna has been optimized to act as the bias coil in a ten layer ferrite LTCC package, thus performing two functions. This not only reduces the overall size of the system by getting rid of the external bias source but also eliminates demagnetization effect (fields lost at air-to-substrate interface), which reduces the required magneto-static field strength and makes the design efficient. RF choking inductor and DC blocking capacitor have been monolithically integrated as package elements to allow the magnetostatic and microwave excitation at the same time. The design has been optimized for its low frequency and high frequency performance in two different simulators. A measured tuning range of 10% is achieved at a center frequency of 13 GHz. The design is highly suitable for low cost, compact, light-weight and tunable microwave systems.

Does the Earth's magnetic field serve as a reference for alignment of the honeybee Waggle dance?

The honeybee (Apis mellifera) waggle dance, which is performed inside the hive by forager bees, informs hive mates about a potent food source, and recruits them to its location. It consists of a repeated figure-8 pattern: two oppositely directed turns interspersed by a short straight segment, the “waggle run”. The waggle run consists of a single stride emphasized by lateral waggling motions of the abdomen. Directional information pointing to a food source relative to the sun's azimuth is encoded in the angle between the waggle run line and a reference line, which is generally thought to be established by gravity. Yet, there is tantalizing evidence that the local (ambient) geomagnetic field (LGMF) could play a role. We tested the effect of the LGMF on the recruitment success of forager bees by placing observation hives inside large Helmholtz coils, and then either reducing the LGMF to 2% or shifting its apparent declination. Neither of these treatments reduced the number of nest mates that waggle dancing forager bees recruited to a feeding station located 200 m north of the hive. These results indicate that the LGMF does not act as the reference for the alignment of waggle-dancing bees.

A novel coil array for combined TMS/fMRI experiments at 3 T.

PurposeTo overcome current limitations in combined transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) studies by employing a dedicated coil array design for 3 Tesla.MethodsThe state‐of‐the‐art setup for concurrent TMS/fMRI is to use a large birdcage head coil, with the TMS between the subject's head and the MR coil. This setup has drawbacks in sensitivity, positioning, and available imaging techniques. In this study, an ultraslim 7‐channel receive‐only coil array for 3 T, which can be placed between the subject's head and the TMS, is presented. Interactions between the devices are investigated and the performance of the new setup is evaluated in comparison to the state‐of‐the‐art setup.ResultsMR sensitivity obtained at the depth of the TMS stimulation is increased by a factor of five. Parallel imaging with an acceleration factor of two is feasible with low g‐factors. Possible interactions between TMS and the novel hardware were investigated and were found negligible.ConclusionThe novel coil array is safe, strongly improves signal‐to‐noise ratio in concurrent TMS/fMRI experiments, enables parallel imaging, and allows for flexible positioning of the TMS on the head while ensuring efficient TMS stimulation due to its ultraslim design. Magn Reson Med 74:1492–1501, 2015. © 2014 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Optimization of multiple coils immersed in a conducting liquid for half-hemisphere or whole-brain deep transcranial magnetic stimulation: a simulation study.

Transcranial magnetic stimulation (TMS) was proposed in 1985. Nevertheless, its wider use in the treatment of several neurologic diseases has been hindered by its inability to stimulate deep-brain regions. This is mainly due to the physical limiting effect arising from the presence of surface discontinuities, particularly between the scalp and air. Here, we present the optimization of a system of large multiple coils for whole-brain and half-hemisphere deep TMS, termed orthogonal configuration. COMSOL(®)-based simulations show that the system is capable of reaching the very center of a spherical brain phantom with 58% induction relative to surface maximum. Such penetration capability surpasses to the best of our knowledge that of existing state of the art TMS systems. This induction capability strongly relies on the immersion of the stimulating coils and part of the head of the patient in a conducting liquid (e.g. simple saline solution). We show the impact of the presence of this surrounding conducting liquid by comparing the performance of our system with and without such liquid. In addition, we also compare the performance of the proposed coil with that of a circular coil, a figure-eight coil, and the H-coil. Finally, in addition to its whole-brain stimulation capability (e.g. potentially useful for prophylaxis of epileptic patients) the system is also able to stimulate mainly one brain hemisphere, which may be useful in stroke rehabilitation, among other applications.

A maximum entropy approach to the study of residue-specific backbone angle distributions in α-synuclein, an intrinsically disordered protein.

α-Synuclein is an intrinsically disordered protein of 140 residues that switches to an α-helical conformation upon binding phospholipid membranes. We characterize its residue-specific backbone structure in free solution with a novel maximum entropy procedure that integrates an extensive set of NMR data. These data include intraresidue and sequential H(N) − H(α) and H(N) − H(N) NOEs, values for (3) JHNHα, (1) JHαCα, (2) JCαN, and (1) JCαN, as well as chemical shifts of (15)N, (13)C(α), and (13)C' nuclei, which are sensitive to backbone torsion angles. Distributions of these torsion angles were identified that yield best agreement to the experimental data, while using an entropy term to minimize the deviation from statistical distributions seen in a large protein coil library. Results indicate that although at the individual residue level considerable deviations from the coil library distribution are seen, on average the fitted distributions agree fairly well with this library, yielding a moderate population (20-30%) of the PPII region and a somewhat higher population of the potentially aggregation-prone β region (20-40%) than seen in the database. A generally lower population of the αR region (10-20%) is found. Analysis of (1)H − (1)H NOE data required consideration of the considerable backbone diffusion anisotropy of a disordered protein.

Large scale Tesla coil guided discharges initiated by femtosecond laser filamentation in air

The guiding of meter scale electric discharges produced in air by a Tesla coil is realized in laboratory using a focused terawatt laser pulse undergoing filamentation. The influence of the focus position, the laser arrival time, or the gap length is studied to determine the best conditions for efficient laser guiding. Discharge parameters such as delay, jitter, and resistance are characterized. An increase of the discharge length by a factor 5 has been achieved with the laser filaments, corresponding to a mean breakdown field of 2 kV/cm for a 1.8 m gap length. Consecutive guided discharges at a repetition rate of 10 Hz are also reported.

E-025 Transorbital Carotid-Cavernous Fistula Embolization with Ruby Coils

PurposeA carotid cavernous fistula (CCF) is an abnormal arteriovenous connexion between the internal carotid artery (ICA) or the external carotid artery (ECA) and the cavernous sinus. Symptoms range from benign...

Toward the Optimization of D-Shaped Coils for the Use in an Open Magnetic Particle Imaging Scanner

Magnetic particle imaging (MPI) is a novel medical imaging modality that allows for the quantitative detection of superparamagnetic iron oxide nanoparticles using static and oscillating magnetic fields. Essential aspects in the coil optimization for MPI include the magnetic field generated per unit current and the magnetic field homogeneity. For a set of D-shaped coils, which can be used in an open MPI scanner with lateral patient access to enable multidimensional imaging, these quantities were analyzed for a range of configurations. The results were compared with the situation in a four-wire-model and a four-wire-model with return paths (called eight-wire-model). It was found that for large coil radii, the effects of the D-coil set resemble those of the eight-wire-model; however, the local minimum in the magnetic field inhomogeneity is less pronounced.

First evidence of detecting surface nuclear magnetic resonance signals using a compact B‐field sensor

AbstractThe noninvasive detection and characterization of subsurface aquifer structures demands geophysical techniques. Surface nuclear magnetic resonance (SNMR) is the only technique that is directly sensitive to hydrogen protons and, therefore, allows for unambiguous detection of subsurface water. Traditionally, SNMR utilizes large surface coils for both transmitting excitation pulses and recording the groundwater response. Recorded data are thus a voltage induced by the time derivative of the secondary magnetic field. For the first time, we demonstrate that the secondary magnetic field in a SNMR experiment can be directly detected using a superconducting quantum interference device magnetometer. Conducting measurements at a test site in Germany, we demonstrate not only the ability to detect SNMR signals on the order of femtoTesla but also we are able to satisfy the observed data by inverse modeling. This is expected to open up completely new applications for this exciting technology.

From Conception to Commissioning of EDIPO and SULTAN Quench Detection Systems

At CRPP in Villigen (Switzerland), the superconducting windings of the EDIPO and SULTAN test facilities need to be protected in case of quench. The detection of a quench, which triggers the protection circuit, is based on the comparison of the voltages on the windings with preset thresholds. Each facility has two quench detection systems, one for the main coils and one for the primary coil of superconducting transformer (TRAFO), which supplies the operating current to the test samples. In the years between 2010 and 2013, a Quench Detection System (QDS) has been developed for EDIPO main coils and for its TRAFO. Afterwards, the 25 years old SULTAN QDS has been updated, for its magnet system and TRAFO, on the basis of the work done before for EDIPO. The four QDS are described and the commissioning of the two EDIPO QDS and the SULTAN-TRAFO QDS is reported. The features of the QDS are discussed, including reliability, sensitivity, and reaction time. The lessons learned can be conveniently extrapolated to other QDS for large coils based on voltage threshold.

Status of the Shielding Coil Fabrication for the Iseult/INUMAC Whole Body 11.75 T MRI Magnet

A neuroscience research center with a very high field magnetic resonance imaging (MRI) equipment was opened in November 2006 in the Neurospin site at CEA Saclay. One of the imaging systems requires a whole body 11.75 T MRI magnet with a 900 mm warm bore. Operating at a homogeneous field level of 11.75 T, the cryostat has external dimensions of 4.8 m in diameter and 5.0 m in length. With the large aperture and high field strength, this magnet represents a real challenge when compared to the largest MRI systems ever built. The coil is made from a copper-stabilized niobium-titanium conductor cooled by a superfluid helium bath at 1.8 K and permanently connected to a cryo-plant. The main coil is constructed from a stack of 170 double pancakes and the magnet is actively shielded by two large coils connected in series to fulfill the stray field specifications. The two shielding coils, each of about 4 m in diameter, are presently being manufactured by Alstom Power Systems STTG Magnets, Belfort. This paper describes the design of these coils and presents the latest progress of their fabrication. Details are given of the winding technique, impregnation method, and the first results of electrical and geometrical tests.

Torus CLAS12-Superconducting Magnet Quench Analysis

The JLAB Torus magnet system consists of six superconducting trapezoidal racetrack-type coils assembled in a toroidal configuration. These coils are wound with SSC-36 Nb-Ti superconductor and have the peak magnetic field of 3.6 T. The first coil manufacturing based on the JLAB design began at FNAL. The large magnet system dimensions (8 m diameter and 14 MJ of stored energy) dictate the need for quench protection. Each coil is placed in an aluminum case mounted inside a cryostat and cooled by 4.6 K supercritical helium gas flowing through a copper tube attached to the coil ID. The large coil dimensions and small cryostat thickness drove the design to challenging technical solutions, suggesting that Lorentz forces due to transport currents and eddy currents during quench and various failure scenarios are analyzed. The paper covers the magnet system quench analysis using the OPERA3d Quench code.

Wireless power transfer to deep-tissue microimplants.

The ability to implant electronic systems in the human body has led to many medical advances. Progress in semiconductor technology paved the way for devices at the scale of a millimeter or less ("microimplants"), but the miniaturization of the power source remains challenging. Although wireless powering has been demonstrated, energy transfer beyond superficial depths in tissue has so far been limited by large coils (at least a centimeter in diameter) unsuitable for a microimplant. Here, we show that this limitation can be overcome by a method, termed midfield powering, to create a high-energy density region deep in tissue inside of which the power-harvesting structure can be made extremely small. Unlike conventional near-field (inductively coupled) coils, for which coupling is limited by exponential field decay, a patterned metal plate is used to induce spatially confined and adaptive energy transport through propagating modes in tissue. We use this method to power a microimplant (2 mm, 70 mg) capable of closed-chest wireless control of the heart that is orders of magnitude smaller than conventional pacemakers. With exposure levels below human safety thresholds, milliwatt levels of power can be transferred to a deep-tissue (>5 cm) microimplant for both complex electronic function and physiological stimulation. The approach developed here should enable new generations of implantable systems that can be integrated into the body at minimal cost and risk.

Experimental Research on the Influence of Transmission Parameters on the Transmission Performance of Magnetic Resonance Wireless Power Transmission Systems

Magnetic resonance wireless power transmission uses resonance strong coupling between the transmission and receiving terminals to realize a non-contact efficient supply of energy over large distance. The transmission power, efficiency and distance are confirmed by comprehensive function of the transmission parameters. By taking experimental means, the influence laws of loop transmission parameters, such as separation between coils, coil size, etc., on the transmission performance are studied in this paper. The experimental results show that the power high-efficiency and high-quality transmission does not depend on the large coil loop coupling coefficient and transmission power and efficiency may increase firstly and then decline as the separation between coils increases. The transmission performance can be optimized by increasing the coils diameter or wire diameter, and moreover, transmission systems with a high resonance frequency can produce high power and efficiency transmission over short distances.

Theoretical Study on the Influence of Transmission Parameters on the Transmission Performance of Magnetic Resonance Wireless Power Transmission Systems

Magnetic resonance wireless power transmission technology is based on the phenomenon of resonant coupling to realize non-contact power transmission via near magnetic field. Based on the mutual coupling model of resonance system, the influence laws of system transmission parameters, such as coil coupling coefficients, load resistance, etc., on the transmission performance are theoretically studied in this paper. The research results shows that the power high-efficiency and high-quality transmission does not depend on the large coil loop coupling coefficient and the working frequencies of maximum power and maximum efficiency transmission do not coincide at most condition. Transmission systems with a high resonance frequency can produce high power and efficiency transmission over short distances. In addition, by increasing the coil diameter or wire diameter can improve the system quality factor, and optimize the energy transmission performance.

A two-component post-column derivatisation method utilising reaction flow chromatography

“Reaction flow (RF) chromatography” has recently emerged from exploiting a new column “Parallel Segmented Flow” (PSF) to post-column derivatisation (PCD) methods [1]. The main advantage RF has over conventional PCD methods is the elimination of large volume reaction coils, as mixing occurs in the PSF column outlet fitting design, therefore minimising peak broadening. In this investigation we take an existing PCD method for the detection of phenols and apply it to RF. The detection sensitivity of the RF method is discussed, with the results demonstrating that through careful control of the mobile phase and derivatisation reagent conditions the selectivity of the PCD reaction may target compounds other than phenols.

MR-monitored focused ultrasound using the acoustic-coupling water bath as an intrinsic high-mode dielectric resonator.

The conventional set-up for MR-monitored focused ultrasound surgery includes a piezoelectric transducer and an acoustic-coupling water bath integrated into the MR patient table; a large surface RF coil is placed close to the patient or, alternatively, the body coil is used as the MR receiver. Potential disadvantages of this approach are that the body coil has low sensitivity because of its low filling factor and the local RF coil can interfere with and cause reflections of the ultrasound irradiation. In this article, a completely new approach is presented, in which an MR transmit/receive coil is not needed at all. Instead, the dimensions of the water bath are adjusted so that a high-order dielectric mode is excited, resulting in efficient MR excitation and reception at the transducer focal point. An example of monitoring ultrasound-mediated heating in a phantom is shown on a 7-T human system, although the new method can also be applied at lower fields.

Race-track coils for a 3 MW HTS ship motor

Since the discovery of high-temperature superconductivity (HTS), Sumitomo Electric has been developing silver-sheathed Bi2223 superconducting wire and products. Ship propulsion motors are one of the most promising applications of HTS. Sumitomo Electric Industries, Ltd. (SEI) has recently manufactured 24 large racetrack coils, using 70km long DI-BSCCO wires, for use in a 3MW HTS motor developed by Kawasaki Heavy Industries, Ltd. (KHI). The 3MW HTS motor, using our newly developed racetrack coils, has successfully passed the loading test. It is particularly important that the HTS field coils used in ship propulsion motors can withstand the expansive forces repeatedly applied to them. As racetrack type coils have straight sections, the support mechanism they require to withstand expansive forces is very different from that of circular coils.Therefore, we ran tests and obtained the basic data to evaluate the 20-year durability of racetrack coils against the repeatedly applied expansive forces expected in domestic ship propulsion motors.