WorldWideScience

Sample records for magnetically guided ultra

  1. Laser cooling of a magnetically guided ultra cold atom beam

    Energy Technology Data Exchange (ETDEWEB)

    Aghajani-Talesh, Anoush

    2014-07-01

    This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 μK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.

  2. Laser cooling of a magnetically guided ultra cold atom beam

    International Nuclear Information System (INIS)

    Aghajani-Talesh, Anoush

    2014-01-01

    This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 μK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.

  3. Magnetically guided capsule endoscopy.

    Science.gov (United States)

    Shamsudhin, Naveen; Zverev, Vladimir I; Keller, Henrik; Pane, Salvador; Egolf, Peter W; Nelson, Bradley J; Tishin, Alexander M

    2017-08-01

    Wireless capsule endoscopy (WCE) is a powerful tool for medical screening and diagnosis, where a small capsule is swallowed and moved by means of natural peristalsis and gravity through the human gastrointestinal (GI) tract. The camera-integrated capsule allows for visualization of the small intestine, a region which was previously inaccessible to classical flexible endoscopy. As a diagnostic tool, it allows to localize the sources of bleedings in the middle part of the gastrointestinal tract and to identify diseases, such as inflammatory bowel disease (Crohn's disease), polyposis syndrome, and tumors. The screening and diagnostic efficacy of the WCE, especially in the stomach region, is hampered by a variety of technical challenges like the lack of active capsular position and orientation control. Therapeutic functionality is absent in most commercial capsules, due to constraints in capsular volume and energy storage. The possibility of using body-exogenous magnetic fields to guide, orient, power, and operate the capsule and its mechanisms has led to increasing research in Magnetically Guided Capsule Endoscopy (MGCE). This work shortly reviews the history and state-of-art in WCE technology. It highlights the magnetic technologies for advancing diagnostic and therapeutic functionalities of WCE. Not restricting itself to the GI tract, the review further investigates the technological developments in magnetically guided microrobots that can navigate through the various air- and fluid-filled lumina and cavities in the body for minimally invasive medicine. © 2017 American Association of Physicists in Medicine.

  4. Ultra high field magnetic resonance imaging

    International Nuclear Information System (INIS)

    Lethimonnier, F.; Vedrine, P.

    2007-01-01

    Understanding human brain function, brain development and brain dysfunction is one of the great challenges of the twenty first century. Biomedical imaging has now run up against a number of technical constraints that are exposing limits to its potential. In order to overcome the current limits to high-field magnetic resonance cerebral imaging (MRI) and unleash its fullest potential, the Cea has built NeuroSpin, an ultra-high-field neuroimaging facility at its Saclay centre (in the Essonne). NeuroSpin already boasts three fully operational MRI systems. The first is a 3-tesla high-field system and the second is a very-high-field 7-tesla system, both of which are dedicated to clinical studies and investigations in humans, while the third is an ultra-high-field 17.65-tesla system designed for studies on small animals. In 2011, NeuroSpin will be commissioning an 11.7-tesla ultra-high-field system of unprecedented power that is designed for research on human subjects. The level of the magnetic field and the scale required will make this joint French-German project to build the magnet a breakthrough in the international arena. (authors)

  5. Magnetic Field Measurements in Beam Guiding Magnets

    CERN Document Server

    Henrichsen, K N

    1998-01-01

    Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as well as the recently developed method of beam based alignment. References of historical nature as well as citations of recent work are given. The present commercial availability of the different sensors and asso-ciated equipment is indicated. Finally we shall try to analyze possible future needs for developments in those fields.

  6. Ultra high energy cosmic rays and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Stanev, Todor; Engel, Ralph; Alvarez-Muniz, Jaime; Seckel, David

    2002-07-01

    We follow the propagation of ultra high energy protons in the presence of random and regular magnetic fields and discuss some of the changes in the angular and energy distributions of these particles introduced by the scattering in the magnetic fields.

  7. Ultra high energy cosmic rays and magnetic fields

    International Nuclear Information System (INIS)

    Stanev, Todor; Engel, Ralph; Alvarez-Muniz, Jaime; Seckel, David

    2002-01-01

    We follow the propagation of ultra high energy protons in the presence of random and regular magnetic fields and discuss some of the changes in the angular and energy distributions of these particles introduced by the scattering in the magnetic fields

  8. Ultra-high-field magnets for future hadron colliders

    International Nuclear Information System (INIS)

    McIntyre, P.M.; Shen, W.

    1997-01-01

    Several new concepts in magnetic design and coil fabrication are being incorporated into designs for ultra-high field collider magnets: a 16 Tesla block-coil dual dipole, also using Nb 3 Sn cable, featuring simple pancake coil construction and face-loaded prestress geometry; a 330 T/m block-coil quadrupole; and a ∼ 20 Tesla pipe-geometry dual dipole, using A15 or BSCCO tape. Field design and fabrication issues are discussed for each magnet

  9. System and method for magnetic current density imaging at ultra low magnetic fields

    Science.gov (United States)

    Espy, Michelle A.; George, John Stevens; Kraus, Robert Henry; Magnelind, Per; Matlashov, Andrei Nikolaevich; Tucker, Don; Turovets, Sergei; Volegov, Petr Lvovich

    2016-02-09

    Preferred systems can include an electrical impedance tomography apparatus electrically connectable to an object; an ultra low field magnetic resonance imaging apparatus including a plurality of field directions and disposable about the object; a controller connected to the ultra low field magnetic resonance imaging apparatus and configured to implement a sequencing of one or more ultra low magnetic fields substantially along one or more of the plurality of field directions; and a display connected to the controller, and wherein the controller is further configured to reconstruct a displayable image of an electrical current density in the object. Preferred methods, apparatuses, and computer program products are also disclosed.

  10. Nuclear reactions in ultra-magnetized supernovae

    International Nuclear Information System (INIS)

    Kondratyev, V.N.

    2002-06-01

    The statistical model is employed to investigate nuclear reactions in ultrastrong magnetic fields relevant for supernovae and neutron stars. For radiative capture processes the predominant mechanisms are argued to correspond to modifications of nuclear level densities, and γ-transition energies due to interactions of the field with magnetic moments of nuclei. The density of states reflects the nuclear structure and results in oscillations of reaction cross sections as a function of field strength, while magnetic interaction energy enhances radiative neutron capture process. Implications in the synthesis of r-process nuclei in supernova site are discussed. (author)

  11. Progress towards magnetic trapping of ultra-cold neutrons

    CERN Document Server

    Huffman, P R; Butterworth, J S; Coakley, K J; Dewey, M S; Dzhosyuk, S N; Gilliam, D M; Golub, R; Greene, G L; Habicht, K; Lamoreaux, S K; Mattoni, C E H; McKinsey, D N; Wietfeldt, F E; Doyle, J M

    2000-01-01

    We report progress towards magnetic trapping of ultra-cold neutrons (UCN) in preparation for a neutron lifetime measurement. UCN will be produced by inelastic scattering of cold (0.89 nm) neutrons in a reservoir of superfluid sup 4 He and confined in a three-dimensional magnetic trap. As the trapped neutrons decay, recoil electrons will generate scintillations in the liquid He, which should be detectable with nearly 100% efficiency. This direct measure of the number of UCN decays vs. time can be used to determine the neutron beta-decay lifetime.

  12. Functional magnetic resonance imaging with ultra-high fields

    International Nuclear Information System (INIS)

    Windischberger, C.; Schoepf, V.; Sladky, R.; Moser, E.; Fischmeister, F.P.S.

    2010-01-01

    Functional magnetic resonance imaging (fMRI) is currently the primary method for non-invasive functional localization in the brain. With the emergence of MR systems with field strengths of 4 Tesla and above, neuronal activation may be studied with unprecedented accuracy. In this article we present different approaches to use the improved sensitivity and specificity for expanding current fMRT resolution limits in space and time based on several 7 Tesla studies. In addition to the challenges that arise with ultra-high magnetic fields possible solutions will be discussed. (orig.) [de

  13. Magnetically Levitated and Guided Systems

    Directory of Open Access Journals (Sweden)

    Florian Puci

    2017-05-01

    Full Text Available The paper describes the fundamentals of magnetic levitation technology. A general background of the magnetic levitation is given in this article, including applications of this technology, several comparisons with other types of technologies, the real stage of its development, etc. Further in the paper, the two main types of magnetically levitated systems are compared within their subgroups, on characteristics and specifications basis. A comparison between the AC and DC power supplies for these systems, including the pros and cons of each type, is also provided in the paper.

  14. Magnetic properties of ultra-small goethite nanoparticles

    International Nuclear Information System (INIS)

    Brok, E; Frandsen, C; Madsen, D E; Mørup, S; Jacobsen, H; Birk, J O; Lefmann, K; Bendix, J; Pedersen, K S; Boothroyd, C B; Berhe, A A; Simeoni, G G

    2014-01-01

    Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mössbauer spectroscopy. The ‘ultra-small’ size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low temperatures most likely due to freezing of spins in canted spin structures. From hysteresis curves we estimate the saturation magnetization from uncompensated magnetic moments to be σ s  = 0.044 A m 2  kg −1 at room temperature. Inelastic neutron scattering measurements show a strong signal from excitations of the uniform mode (q = 0 spin waves) at temperatures of 100–250 K and Mössbauer spectroscopy studies show that the magnetic fluctuations are dominated by ‘classical’ superparamagnetic relaxation at temperatures above ∼170 K. From the temperature dependence of the hyperfine fields and the excitation energy of the uniform mode we estimate a magnetic anisotropy constant of around 1.0 × 10 5  J m −3 . (paper)

  15. Magnetic resonance imaging and spectroscopy at ultra high fields

    International Nuclear Information System (INIS)

    Neuberger, Thomas

    2009-01-01

    The goal of the work presented in this thesis was to explore the possibilities and limitations of MRI / MRS using an ultra high field of 17.6 tesla. A broad range of specific applications and MR methods, from MRI to MRSI and MRS were investigated. The main foci were on sodium magnetic resonance spectroscopic imaging of rodents, magnetic resonance spectroscopy of the mouse brain, and the detection of small amounts of iron labeled stem cells in the rat brain using MRI Sodium spectroscopic imaging was explored since it benefits tremendously from the high magnetic field. Due to the intrinsically low signal in vivo, originating from the low concentrations and short transverse relaxation times, only limited results have been achieved by other researchers until now. Results in the literature include studies conducted on large animals such as dogs to animals as small as rats. No studies performed on mice have been reported, despite the fact that the mouse is the most important laboratory animal due to the ready availability of transgenic strains. Hence, this study concentrated on sodium MRSI of small rodents, mostly mice (brain, heart, and kidney), and in the case of the brain on young rats. The second part of this work concentrated on proton magnetic resonance spectroscopy of the rodent brain. Due to the high magnetic field strength not only the increasing signal but also the extended spectral resolution was advantageous for such kind of studies. The difficulties/limitations of ultra high field MRS were also investigated. In the last part of the presented work detection limits of iron labeled stem cells in vivo using magnetic resonance imaging were explored. The studies provided very useful benchmarks for future researchers in terms of the number of labeled stem cells that are required for high-field MRI studies. Overall this work has shown many of the benefits and the areas that need special attention of ultra high fields in MR. Three topics in MRI, MRS and MRSI were

  16. Magnetic resonance imaging and spectroscopy at ultra high fields

    Energy Technology Data Exchange (ETDEWEB)

    Neuberger, Thomas

    2009-06-23

    The goal of the work presented in this thesis was to explore the possibilities and limitations of MRI / MRS using an ultra high field of 17.6 tesla. A broad range of specific applications and MR methods, from MRI to MRSI and MRS were investigated. The main foci were on sodium magnetic resonance spectroscopic imaging of rodents, magnetic resonance spectroscopy of the mouse brain, and the detection of small amounts of iron labeled stem cells in the rat brain using MRI Sodium spectroscopic imaging was explored since it benefits tremendously from the high magnetic field. Due to the intrinsically low signal in vivo, originating from the low concentrations and short transverse relaxation times, only limited results have been achieved by other researchers until now. Results in the literature include studies conducted on large animals such as dogs to animals as small as rats. No studies performed on mice have been reported, despite the fact that the mouse is the most important laboratory animal due to the ready availability of transgenic strains. Hence, this study concentrated on sodium MRSI of small rodents, mostly mice (brain, heart, and kidney), and in the case of the brain on young rats. The second part of this work concentrated on proton magnetic resonance spectroscopy of the rodent brain. Due to the high magnetic field strength not only the increasing signal but also the extended spectral resolution was advantageous for such kind of studies. The difficulties/limitations of ultra high field MRS were also investigated. In the last part of the presented work detection limits of iron labeled stem cells in vivo using magnetic resonance imaging were explored. The studies provided very useful benchmarks for future researchers in terms of the number of labeled stem cells that are required for high-field MRI studies. Overall this work has shown many of the benefits and the areas that need special attention of ultra high fields in MR. Three topics in MRI, MRS and MRSI were

  17. Earth magnetism a guided tour through magnetic fields

    CERN Document Server

    Campbell, Wallace H

    2001-01-01

    An introductory guide to global magnetic field properties, Earth Magnetism addresses, in non-technical prose, many of the frequently asked questions about Earth''s magnetic field. Magnetism surrounds and penetrates our Earth in ways basic science courses can rarely address. It affects navigation, communication, and even the growth of crystals. As we observe and experience an 11-year solar maximum, we may witness spectacular satellite-destroying solar storms as they interact with our magnetic field. Written by an acknowledged expert in the field, this book will enrich courses in earth science, atmospheric science, geology, meteorology, geomagnetism, and geophysics. Contains nearly 200 original illustrations and eight pages of full-color plates.* Largely mathematics-free and with a wide breadth of material suitable for general readers* Integrates material from geomagnetism, paleomagnetism, and solar-terrestrial space physics.* Features nearly 200 original illustrations and 4 pages of colour plates

  18. Magnetic structures in ultra-thin Holmium films: Influence of external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, L.J. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59600-900, RN (Brazil); Departamento de Física, Universidade do Estado do Rio Grande do Norte, Mossoró 59625-620, RN (Brazil); Mello, V.D. [Departamento de Física, Universidade do Estado do Rio Grande do Norte, Mossoró 59625-620, RN (Brazil); Anselmo, D.H.A.L. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59600-900, RN (Brazil); Vasconcelos, M.S., E-mail: mvasconcelos@ect.ufrn.br [Escola de Ciência e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil)

    2015-03-01

    We address the magnetic phases in very thin Ho films at the temperature interval between 20 K and 132 K. We show that slab size, surface effects and magnetic field due to spin ordering impact significantly the magnetic phase diagram. Also we report that there is a relevant reduction of the external field strength required to saturate the magnetization and for ultra-thin films the helical state does not form. We explore the specific heat and the susceptibility as auxiliary tools to discuss the nature of the phase transitions, when in the presence of an external magnetic field and temperature effects. The presence of an external field gives rise to the magnetic phase Fan and the spin-slip structures. - Highlights: • We analyze the magnetic phases of very thin Ho films in the temperature interval 20–132 K. • We show that slab size, etc. due to spin ordering may impact the magnetic phase diagram. • All magnetic phase transitions, for strong magnetic fields, are marked by the specific heat. • The presence of an external field gives rise to the magnetic phase Fan and the spin-slip one.

  19. Progress on the Magnetic Trapping of Ultra-cold Neutrons

    Science.gov (United States)

    Doyle, John M.

    1998-04-01

    Ultra-cold neutrons (UCN) have been instrumental in making improved measurements of the neutron beta-decay lifetime and in searches for a permanent electric dipole moment.(R. Golub, D. Richardson and S.K. Lamoreaux, Ultra-cold Neutrons), Adam Hilger, 1991 The most accurate experiments have taken place using in-core devices at ILL (Grenoble, France) and PNPI (St. Petersburg, Russia). Superthermal techniques offer the promise of high-density sources of UCN via scattering of cold neutrons. Cold neutron beams are available at many neutron facilities. We are currently working on the development of a superfluid helium UCN source using the Cold Neutron Research Facility at the NIST Research Reactor (Gaithersburg) . Our first experiment plans to use superthermal scattering of neutrons in superfluid helium to produce UCN within a magnetic trapping volume. A magnetic trap 30 cm long and 4 cm diameter will be filled with helium at about 100 mK. Cold neutrons (around 11 K) will be introduced into the trapping region where some of them scatter to low enough energies (around 1 mK) so that they are magnetically trapped. Once trapped the UCN travel undisturbed; they have a very small probability of upscattering. Detection will be accomplished as the UCN beta-decay. The resultant high-energy electron creates excited molecular helium dimers, a portion which decay in less than 10 ns and emit radiation in the XUV (50-100 nm). We have developed techniques to measure these scintillations. Analysis indicates that a high accuracy measurement of the neutron beta decay lifetime should be possible using our techniques. An apparatus has been constructed and initial runs are underway. An overview of the experiment, discussion of systematic errors and recent experimental progress will be presented. This work is done in collaboration with C. Brome, J. Butterworth, S. Dzhosyuk, P. Huffman, C. Mattoni, D. McKinsey, M. Cooper, G. Greene, S. Lamoreaux, R. Golub, K. Habicht, K. Coakley, S. Dewey, D

  20. Permanent magnet system to guide superparamagnetic particles

    Science.gov (United States)

    Baun, Olga; Blümler, Peter

    2017-10-01

    A new concept of using permanent magnet systems for guiding superparamagnetic nano-particles on arbitrary trajectories over a large volume is proposed. The basic idea is to use one magnet system which provides a strong, homogeneous, dipolar magnetic field to magnetize and orient the particles, and a second constantly graded, quadrupolar field, superimposed on the first, to generate a force on the oriented particles. In this configuration the motion of the particles is driven predominantly by the component of the gradient field which is parallel to the direction of the homogeneous field. As a result, particles are guided with constant force and in a single direction over the entire volume. The direction is simply adjusted by varying the angle between quadrupole and dipole. Since a single gradient is impossible due to Gauß' law, the other gradient component of the quadrupole determines the angular deviation of the force. However, the latter can be neglected if the homogeneous field is stronger than the local contribution of the quadrupole field. A possible realization of this idea is a coaxial arrangement of two Halbach cylinders. A dipole to evenly magnetize and orient the particles, and a quadrupole to generate the force. The local force was calculated analytically for this particular geometry and the directional limits were analyzed and discussed. A simple prototype was constructed to demonstrate the principle in two dimensions on several nano-particles of different size, which were moved along a rough square by manual adjustment of the force angle. The observed velocities of superparamagnetic particles in this prototype were always several orders of magnitude higher than the theoretically expected value. This discrepancy is attributed to the observed formation of long particle chains as a result of their polarization by the homogeneous field. The magnetic moment of such a chain is then the combination of that of its constituents, while its hydrodynamic radius

  1. Interplanetary Magnetic Field Guiding Relativistic Particles

    Science.gov (United States)

    Masson, S.; Demoulin, P.; Dasso, S.; Klein, K. L.

    2011-01-01

    The origin and the propagation of relativistic solar particles (0.5 to few Ge V) in the interplanetary medium remains a debated topic. These relativistic particles, detected at the Earth by neutron monitors have been previously accelerated close to the Sun and are guided by the interplanetary magnetic field (IMF) lines, connecting the acceleration site and the Earth. Usually, the nominal Parker spiral is considered for ensuring the magnetic connection to the Earth. However, in most GLEs the IMF is highly disturbed, and the active regions associated to the GLEs are not always located close to the solar footprint of the nominal Parker spiral. A possible explanation is that relativistic particles are propagating in transient magnetic structures, such as Interplanetary Coronal Mass Ejections (ICMEs). In order to check this interpretation, we studied in detail the interplanetary medium where the particles propagate for 10 GLEs of the last solar cycle. Using the magnetic field and the plasma parameter measurements (ACE/MAG and ACE/SWEPAM), we found widely different IMF configurations. In an independent approach we develop and apply an improved method of the velocity dispersion analysis to energetic protons measured by SoHO/ERNE. We determined the effective path length and the solar release time of protons from these data and also combined them with the neutron monitor data. We found that in most of the GLEs, protons propagate in transient magnetic structures. Moreover, the comparison between the interplanetary magnetic structure and the interplanetary length suggest that the timing of particle arrival at Earth is dominantly determined by the type of IMF in which high energetic particles are propagating. Finally we find that these energetic protons are not significantly scattered during their transport to Earth.

  2. Rotatable Small Permanent Magnet Array for Ultra-Low Field Nuclear Magnetic Resonance Instrumentation: A Concept Study.

    Science.gov (United States)

    Vogel, Michael W; Giorni, Andrea; Vegh, Viktor; Pellicer-Guridi, Ruben; Reutens, David C

    2016-01-01

    We studied the feasibility of generating the variable magnetic fields required for ultra-low field nuclear magnetic resonance relaxometry with dynamically adjustable permanent magnets. Our motivation was to substitute traditional electromagnets by distributed permanent magnets, increasing system portability. The finite element method (COMSOL®) was employed for the numerical study of a small permanent magnet array to calculate achievable magnetic field strength, homogeneity, switching time and magnetic forces. A manually operated prototype was simulated and constructed to validate the numerical approach and to verify the generated magnetic field. A concentric small permanent magnet array can be used to generate strong sample pre-polarisation and variable measurement fields for ultra-low field relaxometry via simple prescribed magnet rotations. Using the array, it is possible to achieve a pre-polarisation field strength above 100 mT and variable measurement fields ranging from 20-50 μT with 200 ppm absolute field homogeneity within a field-of-view of 5 x 5 x 5 cubic centimetres. A dynamic small permanent magnet array can generate multiple highly homogeneous magnetic fields required in ultra-low field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) instruments. This design can significantly reduce the volume and energy requirements of traditional systems based on electromagnets, improving portability considerably.

  3. Tripolar electric field Structure in guide field magnetic reconnection

    OpenAIRE

    S. Fu; S. Huang; M. Zhou; B. Ni; X. Deng

    2018-01-01

    It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplit...

  4. Dynamics and morphology of chiral magnetic bubbles in perpendicularly magnetized ultra-thin films

    Science.gov (United States)

    Sarma, Bhaskarjyoti; Garcia-Sanchez, Felipe; Nasseri, S. Ali; Casiraghi, Arianna; Durin, Gianfranco

    2018-06-01

    We study bubble domain wall dynamics using micromagnetic simulations in perpendicularly magnetized ultra-thin films with disorder and Dzyaloshinskii-Moriya interaction. Disorder is incorporated into the material as grains with randomly distributed sizes and varying exchange constant at the edges. As expected, magnetic bubbles expand asymmetrically along the axis of the in-plane field under the simultaneous application of out-of-plane and in-plane fields. Remarkably, the shape of the bubble has a ripple-like part which causes a kink-like (steep decrease) feature in the velocity versus in-plane field curve. We show that these ripples originate due to the nucleation and interaction of vertical Bloch lines. Furthermore, we show that the Dzyaloshinskii-Moriya interaction field is not constant but rather depends on the in-plane field. We also extend the collective coordinate model for domain wall motion to a magnetic bubble and compare it with the results of micromagnetic simulations.

  5. Interaction between laser-produced plasma and guiding magnetic field

    International Nuclear Information System (INIS)

    Hasegawa, Jun; Takahashi, Kazumasa; Ikeda, Shunsuke; Nakajima, Mitsuo; Horioka, Kazuhiko

    2013-01-01

    Transportation properties of laser-produced plasma through a guiding magnetic field were examined. A drifting dense plasma produced by a KrF laser was injected into an axisymmetric magnetic field induced by permanent ring magnets. The plasma ion flux in the guiding magnetic field was measured by a Faraday cup at various distances from the laser target. Numerical analyses based on a collective focusing model were performed to simulate plasma particle trajectories and then compared with the experimental results. (author)

  6. Controlling the competing magnetic anisotropy energies in FineMET amorphous thin films with ultra-soft magnetic properties

    Directory of Open Access Journals (Sweden)

    Ansar Masood

    2017-05-01

    Full Text Available Thickness dependent competing magnetic anisotropy energies were investigated to explore the global magnetic behaviours of FineMET amorphous thin films. A dominant perpendicular magnetization component in the as-deposited state of thinner films was observed due to high magnetoelastic anisotropy energy which arises from stresses induced at the substrate-film interface. This perpendicular magnetization component decreases with increasing film thickness. Thermal annealing at elevated temperature revealed a significant influence on the magnetization state of the FineMET thin films and controlled annealing steps leads to ultra-soft magnetic properties, making these thin films alloys ideal for a wide range of applications.

  7. Magnetic Field Analysis of Plasma Guide in Galathea Trimyx

    Directory of Open Access Journals (Sweden)

    Jin Xianji

    2016-01-01

    Full Text Available You Galathea Trimyx is a kind of small size, multipole magnetic confinement devices in controlled thermonuclear fusion. Plasma guide is one of important part in Galathea Trimyx which is responsible for transporting fast and slow plasma bunches ejected from plasma gun. The distribution and uniformity of magnetic field in completed plasma guide is analyzed in detail, including in x -axis direction and in z-axis direction. On the basis, the motion of plasma in the guide is discussed.

  8. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

    International Nuclear Information System (INIS)

    Chai, Kil-Byoung; Bellan, Paul M.

    2013-01-01

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10 6 frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs

  9. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Kil-Byoung; Bellan, Paul M. [Applied Physics, Caltech, 1200 E. California Boulevard, Pasadena, California 91125 (United States)

    2013-12-15

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10{sup 6} frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

  10. Manipulating beams of ultra-cold atoms with a static magnetic field

    International Nuclear Information System (INIS)

    Rowlands, W.J.; Lau, D.C.; Opat, G.I.; Sidorov, A.I.; McLean, R.J.; Hannaford, P.

    1996-01-01

    The preliminary results on the deflection of a beam of ultra-cold atoms by a static magnetic field are presented. Caesium atoms trapped in a magneto-optical trap (MOT) are cooled using optical molasses, and then fall freely under gravity to form a beam of ultra-cold atoms. The atoms pass through a static inhomogeneous magnetic field produced by a single current-carrying wire, and are deflected by a force dependent on the magnetic substate of the atom. A schematical diagram of the experimental layout for laser trapping and cooling of cesium atom is given. The population of atoms in various magnetic substates can be altered by using resonant laser radiation to optically pump the atoms. The single-wire deflection experiment described can be considered as atomic reflexion from a cylindrical magnetic mirror; the underlying principles and techniques being relevant to the production of atomic mirrors and diffraction gratings. 16 refs., 10 figs

  11. Self-Biased 215MHz Magnetoelectric NEMS Resonator for Ultra-Sensitive DC Magnetic Field Detection

    Science.gov (United States)

    Nan, Tianxiang; Hui, Yu; Rinaldi, Matteo; Sun, Nian X.

    2013-06-01

    High sensitivity magnetoelectric sensors with their electromechanical resonance frequencies electromechanical systems (NEMS) resonator with an electromechanical resonance frequency of 215 MHz based on an AlN/(FeGaB/Al2O3) × 10 magnetoelectric heterostructure for detecting DC magnetic fields. This magnetoelectric NEMS resonator showed a high quality factor of 735, and strong magnetoelectric coupling with a large voltage tunable sensitivity. The admittance of the magnetoelectric NEMS resonator was very sensitive to DC magnetic fields at its electromechanical resonance, which led to a new detection mechanism for ultra-sensitive self-biased RF NEMS magnetoelectric sensor with a low limit of detection of DC magnetic fields of ~300 picoTelsa. The magnetic/piezoelectric heterostructure based RF NEMS magnetoelectric sensor is compact, power efficient and readily integrated with CMOS technology, which represents a new class of ultra-sensitive magnetometers for DC and low frequency AC magnetic fields.

  12. Ultra-High Field Magnets for X-Ray and Neutron Scattering using High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Winn, Barry L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Broholm, C. [Johns Hopkins Univ., Baltimore, MD (United States); Bird, M. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Breneman, Bruce C. [General Atomics, San Diego, CA (United States); Coffey, Michael [Cryomagnetics, Oak Ridge, TN (United States); Cutler, Roy I. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Duckworth, Robert C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Erwin, R. [National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); Hahn, Seungyong [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab); Hernandez, Yamali [National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); Herwig, Kenneth W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Holland, Leo D. [General Atomics, San Diego, CA (United States); Lonergan, Kevin M. [Oxford Instruments, Abingdon (United Kingdom); Melhem, Ziad [Oxford Instruments, Abingdon (United Kingdom); Minter, Stephen J. [Cryomagnetics, Oak Ridge, TN (United States); Nelson, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Paranthaman, M. Parans [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pierce, Josh [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ruff, Jacob [Cornell Univ., Ithaca, NY (United States); Shen, Tengming [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sherline, Todd E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Smeibidl, Peter G. [Helmholtz-Zentrum Berlin (HZB), (Germany); Tennant, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); van der Laan, Danko [Advanced Conductor Technologies, LLC, Boulder, CO (United States); Wahle, Robert J. [Helmholtz-Zentrum Berlin (HZB), (Germany); Zhang, Yifei [SuperPower, Inc., Schenectady, NY (United States)

    2017-01-01

    X-ray and neutron scattering techniques are capable of acquiring information about the structure and dynamics of quantum matter. However, the high-field magnet systems currently available at x-ray and neutron scattering facilities in the United States are limited to fields of 16 tesla (T) at maximum, which precludes applications that require and/or study ultra-high field states of matter. This gap in capability—and the need to address it—is a central conclusion of the 2005 National Academy of Sciences report by the Committee on Opportunities in High Magnetic Field Science. To address this gap, we propose a magnet development program that would more than double the field range accessible to scattering experiments. With the development and use of new ultra-high field–magnets, the program would bring into view new worlds of quantum matter with profound impacts on our understanding of advanced electronic materials.

  13. Ultra-High-Energy Cosmic Ray Acceleration by Magnetic Reconnection in Newborn Pulsars

    OpenAIRE

    Pino, E. M. de Gouveia Dal; Lazarian, A.

    2000-01-01

    Investigamos la posibilidad de que los rayos c osmicos ultra energ eticos (UHECR) observados arriba del l mite GZK sean protones acelerados en zonas de reconecci on localizadas sobre la magnet osfera de pulsares de milisegundos reci en formados por un colapso inducido por acreci on (AIC).

  14. Tripolar electric field Structure in guide field magnetic reconnection

    Science.gov (United States)

    Fu, Song; Huang, Shiyong; Zhou, Meng; Ni, Binbin; Deng, Xiaohua

    2018-03-01

    It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

  15. Tripolar electric field Structure in guide field magnetic reconnection

    Directory of Open Access Journals (Sweden)

    S. Fu

    2018-03-01

    Full Text Available It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection. In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg. Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

  16. Iron Oxide Nanoparticles for Magnetically-Guided and Magnetically-Responsive Drug Delivery

    Directory of Open Access Journals (Sweden)

    Joan Estelrich

    2015-04-01

    Full Text Available In this review, we discuss the recent advances in and problems with the use of magnetically-guided and magnetically-responsive nanoparticles in drug delivery and magnetofection. In magnetically-guided nanoparticles, a constant external magnetic field is used to transport magnetic nanoparticles loaded with drugs to a specific site within the body or to increase the transfection capacity. Magnetofection is the delivery of nucleic acids under the influence of a magnetic field acting on nucleic acid vectors that are associated with magnetic nanoparticles. In magnetically-responsive nanoparticles, magnetic nanoparticles are encapsulated or embedded in a larger colloidal structure that carries a drug. In this last case, an alternating magnetic field can modify the structure of the colloid, thereby providing spatial and temporal control over drug release.

  17. Iron oxide nanoparticles for magnetically-guided and magnetically-responsive drug delivery.

    Science.gov (United States)

    Estelrich, Joan; Escribano, Elvira; Queralt, Josep; Busquets, Maria Antònia

    2015-04-10

    In this review, we discuss the recent advances in and problems with the use of magnetically-guided and magnetically-responsive nanoparticles in drug delivery and magnetofection. In magnetically-guided nanoparticles, a constant external magnetic field is used to transport magnetic nanoparticles loaded with drugs to a specific site within the body or to increase the transfection capacity. Magnetofection is the delivery of nucleic acids under the influence of a magnetic field acting on nucleic acid vectors that are associated with magnetic nanoparticles. In magnetically-responsive nanoparticles, magnetic nanoparticles are encapsulated or embedded in a larger colloidal structure that carries a drug. In this last case, an alternating magnetic field can modify the structure of the colloid, thereby providing spatial and temporal control over drug release.

  18. Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

    International Nuclear Information System (INIS)

    Banerjee, A.K.; Alam, M.N.; Mamun, A.A.

    2001-01-01

    Obliquely propagating ultra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfven mode propagating parallel to the external magnetic field and dust- magnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfven mode these effects play no role, but in obliquely propagating dust-Alfven mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays stabilizing role. (author)

  19. Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

    International Nuclear Information System (INIS)

    Mamun, A.A.

    1999-07-01

    Obliquely propagating ultra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfven mode propagating parallel to the external magnetic field and dust-magnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that these effects of self-gravitational field and dust/ion fluid temperature play no role in parallel propagating dust-Alfven mode, but in obliquely propagating dust-Alfven mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays a destabilizing role whereas the effect of dust/ion fluid temperature plays a stabilizing role. (author)

  20. Effects of Current Guides Destruction at Ultra-fast Acceleration of Macrobodies

    Science.gov (United States)

    Kataev, V. N.; Boriskin, A. S.; Golosov, S. N.; Demidov, V. A.; Klimashov, M. V.; Korolev, P. V.; Makartsev, G. F.; Pikar, A. S.; Russkov, A. S.; Shapovalov, E. V.; Shibitov, Yu. M.

    2006-08-01

    The paper is devoted to discussion of current guides destruction effects in different accelerators: thermal-electric and electro-magnetic rail accelerator at macrobodies acceleration value of 108-109 m/s2. Experimental results with thermal-electric accelerators powering from megajoule capacitor battery and helical magneto-cumulative generator MCG-100 at currents up to 3.5 MA are analyzed. The process of rails destruction at railgun at pressure magnetic field excess over the limit of metal fluidity is presented. Methods of efficiency coefficient increase of capacitive storage energy transmission to kinetic energy of accelerating body are discussed.

  1. Guided flows in coronal magnetic flux tubes

    Science.gov (United States)

    Petralia, A.; Reale, F.; Testa, P.

    2018-01-01

    Context. There is evidence that coronal plasma flows break down into fragments and become laminar. Aims: We investigate this effect by modelling flows confined along magnetic channels. Methods: We consider a full magnetohydrodynamic (MHD) model of a solar atmosphere box with a dipole magnetic field. We compare the propagation of a cylindrical flow perfectly aligned with the field to that of another flow with a slight misalignment. We assume a flow speed of 200 km s-1 and an ambient magnetic field of 30 G. Results: We find that although the aligned flow maintains its cylindrical symmetry while it travels along the magnetic tube, the misaligned one is rapidly squashed on one side, becoming laminar and eventually fragmented because of the interaction and back-reaction of the magnetic field. This model could explain an observation made by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory of erupted fragments that fall back onto the solar surface as thin and elongated strands and end up in a hedge-like configuration. Conclusions: The initial alignment of plasma flow plays an important role in determining the possible laminar structure and fragmentation of flows while they travel along magnetic channels. Movies are available in electronic form at http://www.aanda.org

  2. Arrangement of magnets for magnetic support or guide system. Magnetanordnung fuer ein magnetisches Trag- oder Fuehrungssystem

    Energy Technology Data Exchange (ETDEWEB)

    Bohn, G; Schwaerzler, P

    1978-01-26

    The invention refers to an arrangement of magnets for a magnetic support or guide system, particularly for a levitation vehicle. A magnetic tape which can be moved without touching along a fixed armature rail is provided, having an additional magnet at its ends. The pole surfaces of each additional magnet increase their spacing from the armature rail with increasing distance from the end of the magnetic tape concerned. The purpose of the invention is to improve such an arrangement of magnets so that the extra expense of additional magnets is avoided. According to the invention, this is achieved by the pole surfaces of the outer electromagnets of the magnetic tape, instead of the additional magnets, having an increased spacing from the armature rail with increasing approach to the end of the core free of connected electromagnets. The part of the pole faces remote from the armature rail is made curved in order to produce great leakage of the magnetic field.

  3. Nonlinear electrostatic excitations in magnetized dense plasmas with nonrelativistic and ultra-relativistic degenerate electrons

    International Nuclear Information System (INIS)

    Mahmood, S.; Sadiq, Safeer; Haque, Q.

    2013-01-01

    Linear and nonlinear electrostatic waves in magnetized dense electron-ion plasmas are studied with nonrelativistic and ultra-relativistic degenerate and singly, doubly charged helium (He + , He ++ ) and hydrogen (H + ) ions, respectively. The dispersion relation of electrostatic waves in magnetized dense plasmas is obtained under both the energy limits of degenerate electrons. Using reductive perturbation method, the Zakharov-Kuznetsov equation for nonlinear propagation of electrostatic solitons in magnetized dense plasmas is derived for both nonrelativistic and ultra-relativistic degenerate electrons. It is found that variations in plasma density, magnetic field intensity, different mass, and charge number of ions play significant role in the formation of electrostatic solitons in magnetized dense plasmas. The numerical plots are also presented for illustration using the parameters of dense astrophysical plasma situations such as white dwarfs and neutron stars exist in the literature. The present investigation is important for understanding the electrostatic waves propagation in the outer periphery of compact stars which mostly consists of hydrogen and helium ions with degenerate electrons in dense magnetized plasmas

  4. Magnetic-resonance-guided biopsy of focal liver lesions

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Ethan A. [University of Michigan Health System, Section of Pediatric Radiology, C.S. Mott Children' s Hospital, Department of Radiology, Ann Arbor, MI (United States); Grove, Jason J. [University of Michigan Health System, Division of Interventional Radiology, C.S. Mott Children' s Hospital, Department of Radiology, Ann Arbor, MI (United States); Der Spek, Abraham F.L.V. [University of Michigan Health System, Department of Anesthesiology, C.S. Mott Children' s Hospital, Ann Arbor, MI (United States); Jarboe, Marcus D. [University of Michigan Health System, Division of Interventional Radiology, C.S. Mott Children' s Hospital, Department of Radiology, Ann Arbor, MI (United States); University of Michigan Health System, Section of Pediatric Surgery, C.S. Mott Children' s Hospital, Department of Surgery, Ann Arbor, MI (United States)

    2017-05-15

    Image-guided biopsy techniques are widely used in clinical practice. Commonly used methods employ either ultrasound (US) or computed tomography (CT) for image guidance. In certain patients, US or CT guidance may be suboptimal, or even impossible, because of artifacts, suboptimal lesion visualization, or both. We recently began performing magnetic resonance (MR)-guided biopsy of focal liver lesions in select pediatric patients with lesions that are not well visualized by US or CT. This report describes our experience performing MR-guided biopsy of focal liver lesions, with case examples to illustrate innovative techniques and novel aspects of these procedures. (orig.)

  5. A magnetically driven piston pump for ultra-clean applications

    Science.gov (United States)

    LePort, F.; Neilson, R.; Barbeau, P. S.; Barry, K.; Bartoszek, L.; Counts, I.; Davis, J.; deVoe, R.; Dolinski, M. J.; Gratta, G.; Green, M.; Díez, M. Montero; Müller, A. R.; O'Sullivan, K.; Rivas, A.; Twelker, K.; Aharmim, B.; Auger, M.; Belov, V.; Benitez-Medina, C.; Breidenbach, M.; Burenkov, A.; Cleveland, B.; Conley, R.; Cook, J.; Cook, S.; Craddock, W.; Daniels, T.; Dixit, M.; Dobi, A.; Donato, K.; Fairbank, W.; Farine, J.; Fierlinger, P.; Franco, D.; Giroux, G.; Gornea, R.; Graham, K.; Green, C.; Hägemann, C.; Hall, C.; Hall, K.; Hallman, D.; Hargrove, C.; Herrin, S.; Hughes, M.; Hodgson, J.; Juget, F.; Kaufman, L. J.; Karelin, A.; Ku, J.; Kuchenkov, A.; Kumar, K.; Leonard, D. S.; Lutter, G.; Mackay, D.; MacLellan, R.; Marino, M.; Mong, B.; Morgan, P.; Odian, A.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Pushkin, K.; Rollin, E.; Rowson, P. C.; Schmoll, B.; Sinclair, D.; Skarpaas, K.; Slutsky, S.; Stekhanov, V.; Strickland, V.; Swift, M.; Vuilleumier, J.-L.; Vuilleumier, J.-M.; Wichoski, U.; Wodin, J.; Yang, L.; Yen, Y.-R.

    2011-10-01

    A magnetically driven piston pump for xenon gas recirculation is presented. The pump is designed to satisfy extreme purity and containment requirements, as is appropriate for the recirculation of isotopically enriched xenon through the purification system and large liquid xenon time projection chamber of EXO-200. The pump, using sprung polymer gaskets, is capable of pumping more than 16 standard liters per minute of xenon gas with 750 Torr differential pressure.

  6. Ultra-Wideband Sensors for Improved Magnetic Resonance Imaging, Cardiovascular Monitoring and Tumour Diagnostics

    Directory of Open Access Journals (Sweden)

    Frank Seifert

    2010-12-01

    Full Text Available The specific advantages of ultra-wideband electromagnetic remote sensing (UWB radar make it a particularly attractive technique for biomedical applications. We partially review our activities in utilizing this novel approach for the benefit of high and ultra-high field magnetic resonance imaging (MRI and other applications, e.g., for intensive care medicine and biomedical research. We could show that our approach is beneficial for applications like motion tracking for high resolution brain imaging due to the non-contact acquisition of involuntary head motions with high spatial resolution, navigation for cardiac MRI due to our interpretation of the detected physiological mechanical contraction of the heart muscle and for MR safety, since we have investigated the influence of high static magnetic fields on myocardial mechanics. From our findings we could conclude, that UWB radar can serve as a navigator technique for high and ultra-high field magnetic resonance imaging and can be beneficial preserving the high resolution capability of this imaging modality. Furthermore it can potentially be used to support standard ECG analysis by complementary information where sole ECG analysis fails. Further analytical investigations have proven the feasibility of this method for intracranial displacements detection and the rendition of a tumour’s contrast agent based perfusion dynamic. Beside these analytical approaches we have carried out FDTD simulations of a complex arrangement mimicking the illumination of a human torso model incorporating the geometry of the antennas applied.

  7. Ultra-wideband sensors for improved magnetic resonance imaging, cardiovascular monitoring and tumour diagnostics.

    Science.gov (United States)

    Thiel, Florian; Kosch, Olaf; Seifert, Frank

    2010-01-01

    The specific advantages of ultra-wideband electromagnetic remote sensing (UWB radar) make it a particularly attractive technique for biomedical applications. We partially review our activities in utilizing this novel approach for the benefit of high and ultra-high field magnetic resonance imaging (MRI) and other applications, e.g., for intensive care medicine and biomedical research. We could show that our approach is beneficial for applications like motion tracking for high resolution brain imaging due to the non-contact acquisition of involuntary head motions with high spatial resolution, navigation for cardiac MRI due to our interpretation of the detected physiological mechanical contraction of the heart muscle and for MR safety, since we have investigated the influence of high static magnetic fields on myocardial mechanics. From our findings we could conclude, that UWB radar can serve as a navigator technique for high and ultra-high field magnetic resonance imaging and can be beneficial preserving the high resolution capability of this imaging modality. Furthermore it can potentially be used to support standard ECG analysis by complementary information where sole ECG analysis fails. Further analytical investigations have proven the feasibility of this method for intracranial displacements detection and the rendition of a tumour's contrast agent based perfusion dynamic. Beside these analytical approaches we have carried out FDTD simulations of a complex arrangement mimicking the illumination of a human torso model incorporating the geometry of the antennas applied.

  8. Features of the galactic magnetic field regarding deflections of ultra-high-energy cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Wirtz, Marcus; Erdmann, Martin; Mueller, Gero; Urban, Martin [III. Physikalisches Institut A, RWTH Aachen University (Germany)

    2016-07-01

    Most recent models of the galactic magnetic field have been derived from Faraday rotation measurements and imply strong deflections even for ultra-high energy cosmic rays. We investigate the characteristics of the different field parametrizations and point out similarities and interesting features. Among them are extragalactic regions which are invisible for an Earth bound observation and the transition from diffuse to ballistic behaviour in the 1 EeV energy regime. Applying this knowledge to a directional analysis, there are indications for deflection patterns by the galactic magnetic field in cosmic ray arrival directions measured by the Pierre Auger Observatory.

  9. The spheromak as a prototype for ultra-high-field superconducting magnets

    International Nuclear Information System (INIS)

    Furth, H.P.; Jardin, S.C.

    1987-08-01

    In view of current progress in the development of superconductor materials, the ultimate high-field limit of superconducting magnets is likely to be set by mechanical stress problems. Maximum field strength should be attainable by means of approximately force-free magnet windings having favorable ''MHD'' stability properties (so that small winding errors will not grow). Since a low-beta finite-flux-hole spheromak configuration qualifies as a suitable prototype, the theoretical and experimental spheromak research effort of the past decade has served to create a substantial technical basis for the design of ultra-high-field superconducting coils. 11 refs

  10. Nonlinear propagation of ultra-low-frequency electronic modes in a magnetized dusty plasma

    International Nuclear Information System (INIS)

    Mamun, A.A.

    1999-07-01

    A theoretical investigation has been made of nonlinear propagation of ultra-low-frequency electromagnetic waves in a magnetized two fluid (negatively charged dust and positively charged ion fluids) dusty plasma. These are modified Alfven waves for small value of θ and are modified magnetosonic waves for large θ, where θ is the angle between the directions of the external magnetic field and the wave propagation. A nonlinear evolution equation for the wave magnetic field, which is known as Korteweg de Vries (K-dV) equation and which admits a stationary solitary wave solution, is derived by the reductive perturbation method. The effects of external magnetic field and dust characteristics on the amplitude and the width of these solitary structures are examined. The implications of these results to some space and astrophysical plasma systems, especially to planetary ring-systems, are briefly mentioned. (author)

  11. FY1995 study to create the high density magnetic recording devices by using an ultra clean sputtering process; 1995 nendo choseijo sputter process ni yoru chokomitsudo jiki kiroku device no sosei

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    It is important to control microstructure of thin film magnetic devices such as recording heads and media, in order to induce excellent magnetic properties. Since the impurities in the sputtering atmosphere is easily thought to affect strongly on the initial film growth, we will develop the highly purified sputtering atmosphere to establish a fabrication technology of ultra thin metallic films with desirable microstructure. A specialized multi-sputtering system which has extremely clean atmosphere (impurity level: 1/10000 compared to conventional systems) were realized by (a) decreasing out-gassing rate from vacuum chamber, pumping system, cathode, robot, etc. and (b) using ultra-clean processing gas. The base pressure was 8 x 10{sup -12} Torr (XHV) and the build-up rate was less than 1 x 10{sup -8} Torrl/sec. From the correlation between the microstructure and magnetic properties of a part of spin-valve GMR films, the guiding principle for the microstructural design were clarified to induce the exchange coupling effectively at the ferro/antiferromagnetic interface and to enhance the GMR effect at the magnetic/non-magnetic interface. The mechanism of' Cr segregation on the grain boundaries was clarified, in thin film media deposited under ultra clean sputtering process. The material specification of the magnetic ultra thin film media for high density recording with low media noise were designed from view of the thermal agitation. (NEDO)

  12. Discoveries that guided the beginning of perpendicular magnetic recording

    International Nuclear Information System (INIS)

    Iwasaki, S.

    2001-01-01

    The speculations and discoveries that guided the beginning of perpendicular magnetic recording, which have never been systematically discussed before, are described in this paper. Especially, four important discoveries of perpendicular magnetization, Co-Cr film, effect of double layered medium, and complementarity law are described in detail. The studies on thin film media and recording mechanisms at short wavelengths aiming at the advancement of longitudinal magnetic recording in the 1960's lead to the realization of the new perpendicular magnetic recording through these discoveries. None of these works was on any list of research targets in the 1960's. The study of perpendicular magnetic recording has taught us that research should proceed systematically with definite targets and that it is important to have an attitude not to neglect phenomena that are different from the common sense at the time

  13. Self-generated magnetic fields and energy transport by ultra-intense laser-plasma interaction

    International Nuclear Information System (INIS)

    Abudurexiti, A.; Tuniyazi, P.; Wang Qian

    2011-01-01

    The electromagnetic instability (Weibel instability) and its mechanism in ultra-intense laser-plasma interactions are studied by using three-dimensional particle-in-cell simulations. The transport of energy in electron thermal conduction is analyzed by the Spitzer-Harm theory, and the election's vertical pyrogenation phenomenon that resulted from anisotropic heating of laser is observed. The results indicate that the strong magnetic field excited by Weibel instability makes the electron beam deposit its energy within a very short distance, and it restrains the electron thermal flux formed when the laser ponderomotive force bursts through the electron. With the increase of the self-generated magnetic field, the electron will be seized by the wave of magnetic field, and the transport of heat will be restricted. (authors)

  14. Oxygen-enabled control of Dzyaloshinskii-Moriya Interaction in ultra-thin magnetic films

    KAUST Repository

    Belabbes, Abderrezak

    2016-04-22

    The search for chiral magnetic textures in systems lacking spatial inversion symmetry has attracted a massive amount of interest in the recent years with the real space observation of novel exotic magnetic phases such as skyrmions lattices, but also domain walls and spin spirals with a defined chirality. The electrical control of these textures offers thrilling perspectives in terms of fast and robust ultrahigh density data manipulation. A powerful ingredient commonly used to stabilize chiral magnetic states is the so-called Dzyaloshinskii-Moriya interaction (DMI) arising from spin-orbit coupling in inversion asymmetric magnets. Such a large antisymmetric exchange has been obtained at interfaces between heavy metals and transition metal ferromagnets, resulting in spin spirals and nanoskyrmion lattices. Here, using relativistic first-principles calculations, we demonstrate that the magnitude and sign of DMI can be entirely controlled by tuning the oxygen coverage of the magnetic film, therefore enabling the smart design of chiral magnetism in ultra-thin films. We anticipate that these results extend to other electronegative ions and suggest the possibility of electrical tuning of exotic magnetic phases.

  15. Confinement of ultra-cold neutron in a multiple cusp magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Akiyama, Nobumichi; Inoue, Nobuyuki; Nihei, Hitoshi; Kinosita, Ken-ichi [Tokyo Univ. (Japan). Faculty of Engineering

    1996-08-01

    A new confinement system of ultra-cold neutrons is proposed. The neutron bottle is made of a rectangular vacuum chamber with the size of 40 cm x 40 cm x 30 cm covered with arrays of bar type permanent magnets. The operation of bottle requires neither cooling system nor high electric power supply, and thereby the bottle is appropriate to use in the room which is located in controlled area. The maximum kinetic energy of neutrons confined is 20 neV. Experimental scheme to test the performance of the bottle is described. (author)

  16. Ultra-low magnetic damping in metallic and half-metallic systems

    Science.gov (United States)

    Shaw, Justin

    The phenomenology of magnetic damping is of critical importance to devices which seek to exploit the electronic spin degree of freedom since damping strongly affects the energy required and speed at which a device can operate. However, theory has struggled to quantitatively predict the damping, even in common ferromagnetic materials. This presents a challenge for a broad range of applications in magnonics, spintronics and spin-orbitronics that depend on the ability to precisely control the damping of a material. I will discuss our recent work to precisely measure the intrinsic damping in several metallic and half-metallic material systems and compare experiment with several theoretical models. This investigation uncovered a metallic material composed of Co and Fe that exhibit ultra-low values of damping that approach values found in thin film YIG. Such ultra-low damping is unexpected in a metal since magnon-electron scattering dominates the damping in conductors. However, this system possesses a distinctive feature in the bandstructure that minimizes the density of states at the Fermi energy n(EF). These findings provide the theoretical framework by which such ultra-low damping can be achieved in metallic ferromagnets and may enable a new class of experiments where ultra-low damping can be combined with a charge current. Half-metallic Heusler compounds by definition have a bandgap in one of the spin channels at the Fermi energy. This feature can also lead to exceptionally low values of the damping parameter. Our results show a strong correlation of the damping with the order parameter in Co2MnGe. Finally, I will provide an overview of the recent advances in achieving low damping in thin film Heusler compounds.

  17. Direct imaging of neural currents using ultra-low field magnetic resonance techniques

    Science.gov (United States)

    Volegov, Petr L [Los Alamos, NM; Matlashov, Andrei N [Los Alamos, NM; Mosher, John C [Los Alamos, NM; Espy, Michelle A [Los Alamos, NM; Kraus, Jr., Robert H.

    2009-08-11

    Using resonant interactions to directly and tomographically image neural activity in the human brain using magnetic resonance imaging (MRI) techniques at ultra-low field (ULF), the present inventors have established an approach that is sensitive to magnetic field distributions local to the spin population in cortex at the Larmor frequency of the measurement field. Because the Larmor frequency can be readily manipulated (through varying B.sub.m), one can also envision using ULF-DNI to image the frequency distribution of the local fields in cortex. Such information, taken together with simultaneous acquisition of MEG and ULF-NMR signals, enables non-invasive exploration of the correlation between local fields induced by neural activity in cortex and more `distant` measures of brain activity such as MEG and EEG.

  18. Preparation of ultra-light magnetic nanocomposites using highly concentrated emulsions

    International Nuclear Information System (INIS)

    Ghosh, Goutam; Vilchez, Alejandro; Esquena, Jordi; Solans, Conxita; Rodriguez-Abreu, Carlos

    2011-01-01

    Highlights: → Polystyrene-divinylbenzene-iron oxide nanocomposites. → Porous magnetic nanocomposites from highly concentrated emulsions. → Ultralight materials with relatively high magnetic moment. - Abstract: Hybrid inorganic-organic ultra-light magnetic solid foams with iron oxide nanoparticles embedded in a divinylbenzene-polystyrene matrix were prepared using a highly concentrated emulsion polymerization method. Iron oxide nanoparticles with diameters of 3 and 10 nm were synthesized using two different methods. For comparison purposes, nanocomposites with magnetite nanoparticles dispersed in a non-porous polymeric matrix obtained by bulk polymerization were also investigated. Materials were characterized using several techniques such as dynamic light scattering (DLS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and magnetization measurements. SEM and TEM images showed that solid foams are made of well-defined macro pores with nanoparticles embedded in the walls. The density of the solid foams was ca. 50-70 kg m -3 , which is about 20 times lighter than the non-porous monoliths. The magnetic measurements show that both nanocomposites are superparamagnetic, and that there are differences regarding the interparticle interactions depending on matrix porosity. The synthesized materials may find applications in adsorbents, tissue reparation, enzyme supports, microreactors, or in water decontamination.

  19. Preparation of ultra-light magnetic nanocomposites using highly concentrated emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Goutam; Vilchez, Alejandro; Esquena, Jordi; Solans, Conxita [Instituto de Quimica Avanzada de Cataluna, Consejo Superior de Investigaciones Cientificas (IQAC-CSIC), Jordi Girona 18-26, 08034 Barcelona (Spain); Rodriguez-Abreu, Carlos, E-mail: carlos.rodriguez@inl.int [Instituto de Quimica Avanzada de Cataluna, Consejo Superior de Investigaciones Cientificas (IQAC-CSIC), Jordi Girona 18-26, 08034 Barcelona (Spain); International Iberian Nanotechnology Laboratory (INL), Av. Mestre Jose Veiga, 4715-330 Braga (Portugal)

    2011-10-17

    Highlights: {yields} Polystyrene-divinylbenzene-iron oxide nanocomposites. {yields} Porous magnetic nanocomposites from highly concentrated emulsions. {yields} Ultralight materials with relatively high magnetic moment. - Abstract: Hybrid inorganic-organic ultra-light magnetic solid foams with iron oxide nanoparticles embedded in a divinylbenzene-polystyrene matrix were prepared using a highly concentrated emulsion polymerization method. Iron oxide nanoparticles with diameters of 3 and 10 nm were synthesized using two different methods. For comparison purposes, nanocomposites with magnetite nanoparticles dispersed in a non-porous polymeric matrix obtained by bulk polymerization were also investigated. Materials were characterized using several techniques such as dynamic light scattering (DLS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and magnetization measurements. SEM and TEM images showed that solid foams are made of well-defined macro pores with nanoparticles embedded in the walls. The density of the solid foams was ca. 50-70 kg m{sup -3}, which is about 20 times lighter than the non-porous monoliths. The magnetic measurements show that both nanocomposites are superparamagnetic, and that there are differences regarding the interparticle interactions depending on matrix porosity. The synthesized materials may find applications in adsorbents, tissue reparation, enzyme supports, microreactors, or in water decontamination.

  20. Conclusion: probable and possible futures. MRI with ultra high magnetic field

    International Nuclear Information System (INIS)

    Le Bihan, D.

    2009-01-01

    MR neuroimaging does not interfere with brain function. Because it is safe, it can be used to study the brains of both patients and healthy volunteers. The tasks performed by neurons depend largely on their precise location, and high-field magnets have the potential to provide a 5- to 10-fold increase in spatio-temporal resolution. This should allow brain function to be studied on a scale of only a few thousand neurons, possibly at the intermediate scale of the 'neural code'. NeuroSpin, a new CEA research center, is dedicated to neuro-MRI at high magnetic field strengths. As a forum for dialogue between those developing and those using these instruments, it brings together researchers and engineers, technicians and medical doctors. NeuroSpin is one of the few institutions in Europe, if not the world, where these experts can come together in one place to design, construct and use machines equipped with ultra-strong magnets. The strongest 'routine' MR device currently operates at 3 Tesla (60 000 times the earth's magnetic field), whereas a first French system operating at 7 Tesla (140 000 times the earth's field) is now available for human studies, and another system operating at 11.7 Tesla (world record) should be delivered in 2011. Preclinical studies are also being conducted with magnets operating at 7 Tesla and, soon, 17.6 Tesla. (author)

  1. Ultra-low field nuclear magnetic resonance and magnetic resonance imaging to discriminate and identify materials

    Science.gov (United States)

    Matlashov, Andrei Nikolaevich; Urbaitis, Algis V.; Savukov, Igor Mykhaylovich; Espy, Michelle A.; Volegov, Petr Lvovich; Kraus, Jr., Robert Henry

    2013-03-05

    Method comprising obtaining an NMR measurement from a sample wherein an ultra-low field NMR system probes the sample and produces the NMR measurement and wherein a sampling temperature, prepolarizing field, and measurement field are known; detecting the NMR measurement by means of inductive coils; analyzing the NMR measurement to obtain at least one measurement feature wherein the measurement feature comprises T1, T2, T1.rho., or the frequency dependence thereof; and, searching for the at least one measurement feature within a database comprising NMR reference data for at least one material to determine if the sample comprises a material of interest.

  2. Localized Electron Heating by Strong Guide-Field Magnetic Reconnection

    Science.gov (United States)

    Guo, Xuehan; Sugawara, Takumichi; Inomoto, Michiaki; Yamasaki, Kotaro; Ono, Yasushi; UTST Team

    2015-11-01

    Localized electron heating of magnetic reconnection was studied under strong guide-field (typically Bt 15Bp) using two merging spherical tokamak plasmas in Univ. Tokyo Spherical Tokamak (UTST) experiment. Our new slide-type two-dimensional Thomson scattering system documented for the first time the electron heating localized around the X-point. The region of high electron temperature, which is perpendicular to the magnetic field, was found to have a round shape with radius of 2 [cm]. Also, it was localized around the X-point and does not agree with that of energy dissipation term Et .jt . When we include a guide-field effect term Bt / (Bp + αBt) for Et .jt where α =√{ (vin2 +vout2) /v∥2 } , the energy dissipation area becomes localized around the X-point, suggesting that the electrons are accelerated by the reconnection electric field parallel to the magnetic field and thermalized around the X-point. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus,'' a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.

  3. [Electric traction magnetic fields of ultra-low frequency as an occupational risk factor of ischemic heart disease].

    Science.gov (United States)

    Ptitsyna, N G; Kudrin, V A; Villorezi, D; Kopytenko, Iu A; Tiasto, M I; Kopytenko, E A; Bochko, V A; Iuchchi, N

    1996-01-01

    The study was inspired by earlier results that displayed influence of variable natural geomagnetic field (0.005-10 Hz range-ultra-low frequencies) on circulatory system, indicated possible correlation between industrial ultra-low frequency fields and prevalence of myocardial infarction. The authors conducted unique measurements of ultra-low frequency fields produced by electric engines. The results were compared with data on morbidity among railway transport workers. The findings are that level of magnetic variations in electric locomotive cabin can exceed 280 micro Tesla, whereas that in car sections reaches 50 micro Tesla. Occurrence of coronary heart disease among the locomotive operators appeared to be 2.0 + 0.2 times higher than that among the car section operators. Higher risk of coronary heart disease in the locomotive operators is associated with their increased occupational magnetic load.

  4. Magnetic atom optics: mirrors, guides, traps, and chips for atoms

    Energy Technology Data Exchange (ETDEWEB)

    Hinds, E.A.; Hughes, I.G. [Sussex Centre for Optical and Atomic Physics, University of Sussex, Brighton (United Kingdom)

    1999-09-21

    For the last decade it has been possible to cool atoms to microkelvin temperatures ({approx}1 cm s{sup -1}) using a variety of optical techniques. Light beams provide the very strong frictional forces required to slow atoms from room temperature ({approx}500 m s{sup -1}). However, once the atoms are cold, the relatively weak conservative forces of static electric and magnetic fields play an important role. In our group we have been studying the interaction of cold rubidium atoms with periodically magnetized data storage media. Here we review the underlying principles of the forces acting on atoms above a suitably magnetized substrate or near current-carrying wires. We also summarize the status of experiments. These structures can be used as smooth or corrugated reflectors for controlling the trajectories of cold atoms. Alternatively, they may be used to confine atoms to a plane, a line, or a dot and in some cases to reach the quantum limit of confinement. Atoms levitated above a magnetized surface can be guided electrostatically by wires deposited on the surface. The flow and interaction of atoms in such a structure may form the basis of a new technology, 'integrated atom optics' which might ultimately be capable of realizing a quantum computer. (author)

  5. Magnetic Microcalorimeter (MMC) Gamma Detectors with Ultra-High Energy Resolution

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Stephen [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2018-01-19

    The goal of this LCP is to develop ultra-high resolution gamma detectors based on magnetic microcalorimeters (MMCs) for accurate non-destructive analysis (NDA) of nuclear materials. For highest energy resolution, we will introduce erbium-doped silver (Ag:Er) as a novel sensor material, and implement several geometry and design changes to improve the signal-to-noise ratio. The detector sensitivity will be increased by developing arrays of 32 Ag:Er pixels read out by 16 SQUID preamplifiers, and by developing a cryogenic Compton veto to reduce the spectral background. Since best MMC performance requires detector operation at ~10 mK, we will purchase a dilution refrigerator with a base temperature <10 mK and adapt it for MMC operation. The detector performance will be tested with radioactive sources of interest to the safeguards community.

  6. Magnetic anisotropy in iron thin films evaporated under ultra-high vacuum

    International Nuclear Information System (INIS)

    Dinhut, J.F.; Eymery, J.P.; Krishnan, R.

    1992-01-01

    α-iron thin films with thickness ranging between 20 and 1500 nm have been evaporated using an electron gun under ultra-high vacuum conditions (5.10 -7 P). The columnar structure observed in cross-sectional TEM is related to the large surface diffusion. From Moessbauer spectra the spin orientation is deduced and found to be influenced by the column axis. Spins can be obtained perpendicularly to the film plane by rotating the substrte during the deposition. The magnetization of the samples is reduced by about 30% and the reduction attributed to the interstitial space which increases with the incident angle. The substrate rotation also decreases Ku( parallel ) by a factor 2 and increases Ku( perpendicular to ). (orig.)

  7. Ultra-fast magnetic resonance encephalography of physiological brain activity - Glymphatic pulsation mechanisms?

    Science.gov (United States)

    Kiviniemi, Vesa; Wang, Xindi; Korhonen, Vesa; Keinänen, Tuija; Tuovinen, Timo; Autio, Joonas; LeVan, Pierre; Keilholz, Shella; Zang, Yu-Feng; Hennig, Jürgen; Nedergaard, Maiken

    2016-06-01

    The theory on the glymphatic convection mechanism of cerebrospinal fluid holds that cardiac pulsations in part pump cerebrospinal fluid from the peri-arterial spaces through the extracellular tissue into the peri-venous spaces facilitated by aquaporin water channels. Since cardiac pulses cannot be the sole mechanism of glymphatic propulsion, we searched for additional cerebrospinal fluid pulsations in the human brain with ultra-fast magnetic resonance encephalography. We detected three types of physiological mechanisms affecting cerebral cerebrospinal fluid pulsations: cardiac, respiratory, and very low frequency pulsations. The cardiac pulsations induce a negative magnetic resonance encephalography signal change in peri-arterial regions that extends centrifugally and covers the brain in ≈1 Hz cycles. The respiratory ≈0.3 Hz pulsations are centripetal periodical pulses that occur dominantly in peri-venous areas. The third type of pulsation was very low frequency (VLF 0.001-0.023 Hz) and low frequency (LF 0.023-0.73 Hz) waves that both propagate with unique spatiotemporal patterns. Our findings using critically sampled magnetic resonance encephalography open a new view into cerebral fluid dynamics. Since glymphatic system failure may precede protein accumulations in diseases such as Alzheimer's dementia, this methodological advance offers a novel approach to image brain fluid dynamics that potentially can enable early detection and intervention in neurodegenerative diseases. © The Author(s) 2015.

  8. Subsolar magnetopause observation and kinetic simulation of a tripolar guide magnetic field perturbation consistent with a magnetic island

    Science.gov (United States)

    Eriksson, S.; Cassak, P. A.; Retinò, A.; Mozer, F. S.

    2016-04-01

    The Polar satellite recorded two reconnection exhausts within 6 min on 1 April 2001 across a subsolar magnetopause that displayed a symmetric plasma density, but different out-of-plane magnetic field signatures for similar solar wind conditions. The first magnetopause crossing displayed a bipolar guide field variation in a weak external guide field consistent with a symmetric Hall field from a single X line. The subsequent crossing represents the first observation of a tripolar guide field perturbation at Earth's magnetopause in a strong guide field. This perturbation consists of a significant guide field enhancement between two narrow guide field depressions. A particle-in-cell simulation for the prevailing conditions across this second event resulted in a magnetic island between two simulated X lines across which a tripolar guide field developed consistent with the observation. The simulated island supports a scenario whereby Polar encountered the asymmetric quadrupole Hall magnetic fields between two X lines for symmetric conditions across the magnetopause.

  9. Ultra-fast magnetization reversal in magnetic nano-pillars by spin-polarized current

    Energy Technology Data Exchange (ETDEWEB)

    Devolder, T. [Institut d' Electronique Fondamentale, UMR 8622 CNRS, Universite Paris Sud, Ba-circumflex timent 220, 91405 Orsay (France)]. E-mail: thibaut.devolder@ief.u-psud.fr; Tulapurkar, A. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan); CREST, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi 332-0012 (Japan); Yagami, K. [SSNC, Semiconductor Technology Development Group, SONY Corporation, Atsugi, Kanagawa 243-0014 (Japan); Crozat, P. [Institut d' Electronique Fondamentale, UMR 8622 CNRS, Universite Paris Sud, Ba-circumflex timent 220, 91405 Orsay (France); Chappert, C. [Institut d' Electronique Fondamentale, UMR 8622 CNRS, Universite Paris Sud, Ba-circumflex timent 220, 91405 Orsay (France); Fukushima, A. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan); CREST, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi 332-0012 (Japan); Suzuki, Y. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568 (Japan); CREST, Japan Science and Technology Corporation, 4-1-8 Honcho, Kawaguchi 332-0012 (Japan)

    2005-02-01

    We study the speed limitations of the magnetization switching resulting from spin transfer in pillar-shaped CoFe/Cu/CoFe spin valves. The quasi-static critical currents are Ic-=-2mA for the antiparallel (AP) to parallel (P) configuration and Ic+=+4.6mA for the P to AP transition. Current pulses of duration down to 100ps and amplitude of 4I{sub c} trigger switching at 300K. The switching is probabilistic for lower current pulses. The P to AP transition speed is not much temperature dependant from 50 to 300K. In contrast, the AP to P transition is thermally inhibited and is much faster at 150K than at 300K. This thermal inhibition highlights the importance of the macrospin coherency and of the thermally excited spin waves with finite wave vector parallel to the magnetization. Our results validate spin-transfer switching for fast memory applications.

  10. Ultra-fast magnetization reversal in magnetic nano-pillars by spin-polarized current

    International Nuclear Information System (INIS)

    Devolder, T.; Tulapurkar, A.; Yagami, K.; Crozat, P.; Chappert, C.; Fukushima, A.; Suzuki, Y.

    2005-01-01

    We study the speed limitations of the magnetization switching resulting from spin transfer in pillar-shaped CoFe/Cu/CoFe spin valves. The quasi-static critical currents are Ic-=-2mA for the antiparallel (AP) to parallel (P) configuration and Ic+=+4.6mA for the P to AP transition. Current pulses of duration down to 100ps and amplitude of 4I c trigger switching at 300K. The switching is probabilistic for lower current pulses. The P to AP transition speed is not much temperature dependant from 50 to 300K. In contrast, the AP to P transition is thermally inhibited and is much faster at 150K than at 300K. This thermal inhibition highlights the importance of the macrospin coherency and of the thermally excited spin waves with finite wave vector parallel to the magnetization. Our results validate spin-transfer switching for fast memory applications

  11. Application of magnetic liposomes for magnetically guided transport of muscle relaxants and anti-cancer photodynamic drugs

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, Anatoly A.; Filippov, Victor I.; Alyautdin, Renat N.; Torshina, N.L.; Kuznetsov, O.A. E-mail: oleg@louisiana.edu

    2001-07-01

    Magnetic liposomes containing submicron-sized ferromagnetic particles were prepared encapsulating the muscle relaxant drugs, diadony or diperony, for local anesthesia. Alternatively, metal phthalocyanines (Photosense or Teraphthal), sensitizers for photodynamic or catalytic cancer therapy were loaded into the magnetic liposomes. Animal trials demonstrated successful magnetically guided transport of the drug-loaded liposomes.

  12. Application of magnetic liposomes for magnetically guided transport of muscle relaxants and anti-cancer photodynamic drugs

    International Nuclear Information System (INIS)

    Kuznetsov, Anatoly A.; Filippov, Victor I.; Alyautdin, Renat N.; Torshina, N.L.; Kuznetsov, O.A.

    2001-01-01

    Magnetic liposomes containing submicron-sized ferromagnetic particles were prepared encapsulating the muscle relaxant drugs, diadony or diperony, for local anesthesia. Alternatively, metal phthalocyanines (Photosense or Teraphthal), sensitizers for photodynamic or catalytic cancer therapy were loaded into the magnetic liposomes. Animal trials demonstrated successful magnetically guided transport of the drug-loaded liposomes

  13. Functional magnetic resonance imaging with ultra-high fields; Funktionelle Magnetresonanztomographie bei ultrahohen Feldern

    Energy Technology Data Exchange (ETDEWEB)

    Windischberger, C.; Schoepf, V.; Sladky, R.; Moser, E. [Medizinische Universitaet Wien, Exzellenzzentrum Hochfeld-MR, Wien (Austria); Medizinische Universitaet Wien, Zentrum fuer Medizinische Physik und Biomedizinische Technik, Wien (Austria); Fischmeister, F.P.S. [Medizinische Universitaet Wien, Exzellenzzentrum Hochfeld-MR, Wien (Austria); Universitaet Wien, Fakultaet fuer Psychologie, Wien (Austria)

    2010-02-15

    Functional magnetic resonance imaging (fMRI) is currently the primary method for non-invasive functional localization in the brain. With the emergence of MR systems with field strengths of 4 Tesla and above, neuronal activation may be studied with unprecedented accuracy. In this article we present different approaches to use the improved sensitivity and specificity for expanding current fMRT resolution limits in space and time based on several 7 Tesla studies. In addition to the challenges that arise with ultra-high magnetic fields possible solutions will be discussed. (orig.) [German] Die funktionelle Magnetresonanztomographie (fMRT) stellt zurzeit die wichtigste Methode zur nichtinvasiven Funktionslokalisation im Gehirn dar. Mit der Verfuegbarkeit von MRT-Geraeten mit Magnetfeldstaerken von 4 Tesla (T) und darueber ergeben sich neue Moeglichkeiten, mittels fMRT die neuronale Aktivitaet in bislang unerreichter Genauigkeit zu untersuchen. In diesem Artikel zeigen wir anhand mehrerer Studien bei 7 T, in wieweit die Zugewinne an Sensitivitaet und Spezifitaet verwendet werden koennen, um die bisherigen Grenzen der fMRT-Aufloesung in raeumlicher und zeitlicher Hinsicht auszuweiten. Die neuen Herausforderungen, die mit dem Schritt zu ultrahohen Magnetfeldern einhergehen, werden dabei ebenso diskutiert wie moegliche Ansaetze zu deren Loesung. (orig.)

  14. Cross-validation of independent ultra-low-frequency magnetic recording systems for active fault studies

    Science.gov (United States)

    Wang, Can; Bin, Chen; Christman, Lilianna E.; Glen, Jonathan M. G.; Klemperer, Simon L.; McPhee, Darcy K.; Kappler, Karl N.; Bleier, Tom E.; Dunson, J. Clark

    2018-04-01

    When working with ultra-low-frequency (ULF) magnetic datasets, as with most geophysical time-series data, it is important to be able to distinguish between cultural signals, internal instrument noise, and natural external signals with their induced telluric fields. This distinction is commonly attempted using simultaneously recorded data from a spatially remote reference site. Here, instead, we compared data recorded by two systems with different instrumental characteristics at the same location over the same time period. We collocated two independent ULF magnetic systems, one from the QuakeFinder network and the other from the United States Geological Survey (USGS)-Stanford network, in order to cross-compare their data, characterize data reproducibility, and characterize signal origin. In addition, we used simultaneous measurements at a remote geomagnetic observatory to distinguish global atmospheric signals from local cultural signals. We demonstrated that the QuakeFinder and USGS-Stanford systems have excellent coherence, despite their different sensors and digitizers. Rare instances of isolated signals recorded by only one system or only one sensor indicate that caution is needed when attributing specific recorded signal features to specific origins.[Figure not available: see fulltext.

  15. Usefulness of intraoperative ultra low-field magnetic resonance imaging in glioma surgery.

    Science.gov (United States)

    Senft, Christian; Seifert, Volker; Hermann, Elvis; Franz, Kea; Gasser, Thomas

    2008-10-01

    The aim of this study was to demonstrate the usefulness of a mobile, intraoperative 0.15-T magnetic resonance imaging (MRI) scanner in glioma surgery. We analyzed our prospectively collected database of patients with glial tumors who underwent tumor resection with the use of an intraoperative ultra low-field MRI scanner (PoleStar N-20; Odin Medical Technologies, Yokneam, Israel/Medtronic, Louisville, CO). Sixty-three patients with World Health Organization Grade II to IV tumors were included in the study. All patients were subjected to postoperative 1.5-T imaging to confirm the extent of resection. Intraoperative image quality was sufficient for navigation and resection control in both high- and low-grade tumors. Primarily enhancing tumors were best detected on T1-weighted imaging, whereas fluid-attenuated inversion recovery sequences proved best for nonenhancing tumors. Intraoperative resection control led to further tumor resection in 12 (28.6%) of 42 patients with contrast-enhancing tumors and in 10 (47.6%) of 21 patients with noncontrast-enhancing tumors. In contrast-enhancing tumors, further resection led to an increased rate of complete tumor resection (71.2 versus 52.4%), and the surgical goal of gross total removal or subtotal resection was achieved in all cases (100.0%). In patients with noncontrast-enhancing tumors, the surgical goal was achieved in 19 (90.5%) of 21 cases, as intraoperative MRI findings were inconsistent with postoperative high-field imaging in 2 cases. The use of the PoleStar N-20 intraoperative ultra low-field MRI scanner helps to evaluate the extent of resection in glioma surgery. Further tumor resection after intraoperative scanning leads to an increased rate of complete tumor resection, especially in patients with contrast-enhancing tumors. However, in noncontrast- enhancing tumors, the intraoperative visualization of a complete resection seems less specific, when compared with postoperative 1.5-T MRI.

  16. MESSENGER Magnetic Field Observations of Upstream Ultra-Low Frequency Waves at Mercury

    Science.gov (United States)

    Le, G.; Chi, P. J.; Boardsen, S.; Blanco-Cano, X.; Anderosn, B. J.; Korth, H.

    2012-01-01

    The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study of upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. The most common foreshock waves have frequencies near 2 Hz, with properties similar to the I-Hz waves in the Earth's foreshock. They are present in both the flyby data and in every orbit of the orbital data we have surveyed. The most common wave phenomenon in the Earth's foreshock is the large-amplitude 30-s waves, but similar waves at Mercury have frequencies at near 0.1 Hz and occur only sporadically with short durations (a few wave cycles). Superposed on the "30-s" waves, there are spectral peaks at near 0.6 Hz, not reported previously in Mariner 10 data. We will discuss wave properties and their occurrence characteristics in this paper.

  17. 3-Tesla functional magnetic resonance imaging-guided tumor resection

    Energy Technology Data Exchange (ETDEWEB)

    Hall, W.A. [Univ. of Minnesota Medical School, Minneapolis, MN (United States). Depts. of Neurosurgery; Univ. of Minnesota Medical School, Minneapolis, MN (United States). Dept. of Radiation Oncology; Univ. of Minnesota Medical School, Minneapolis, MN (United States). Dept. of Radiology; University of Minnesota Medical Center (MMC), Minneapolis, MN (United States); Truwit, C.L. [Univ. of Minnesota Medical School, Minneapolis, MN (United States). Dept. of Radiology; Univ. of Minnesota Medical School, Minneapolis, MN (United States). Dept. of Pediatrics; Univ. of Minnesota Medical School, Minneapolis, MN (United States). Dept. of Neurology; Hennepin Country Medical Center, Minneapolis, MN (United States). Dept. of Radiology

    2006-12-15

    Objective: We sought to determine the safety and efficacy of using 3-tesla (T) functional magnetic resonance imaging (fMRI) to guide brain tumor resection. Material and methods: From February 2004 to March 2006, fMRI was performed on 13 patients before surgical resection. Functional imaging was used to identify eloquent cortices for motor (8), speech (3), and motor and speech (2) activation using two different 3-T magnetic resonance (MR) scanners. Surgical resection was accomplished using a 1.5-T intraoperative MR system. Appropriate MR scan sequences were performed intraoperatively to determine and maximize the extent of the surgical resection. Results: Tumors included six oligodendrogliomas, three meningiomas, two astrocytomas and two glioblastomas multiforme. The fMRI data was accurate in all cases. After surgery, two patients had hemiparesis, two had worsening of their speech, and one had worsening of speech and motor function. Neurological function returned to normal in all patients within 1 month. Complete resections were possible in 10 patients (77%). Two patients had incomplete resections because of the proximity of their tumors to functional areas. Biopsy was performed in another patient with an astrocytoma in the motor strip. Conclusion: 3-T fMRI was accurate for locating neurologic function before tumor resection near eloquent cortex. (orig.)

  18. Cone-guided fast ignition with no imposed magnetic fields

    Directory of Open Access Journals (Sweden)

    Strozzi D.

    2013-11-01

    Full Text Available Simulations are presented of ignition-scale fast ignition targets with the integrated Zuma-Hydra PIC-hydrodynamic capability. We consider a spherical DT fuel assembly with a carbon cone, and an artificially-collimated fast electron source. We study the role of E and B fields and the fast electron energy spectrum. For mono-energetic 1.5 MeV fast electrons, without E and B fields, ignition can be achieved with fast electron energy Efig = 30kJ. This is 3.5× the minimal deposited ignition energy of 8.7 kJ for our fuel density of 450 g/cm3. Including E and B fields with the resistive Ohm's law E = ηJb gives Efig = 20kJ, while using the full Ohm's law gives Efig > 40 kJ. This is due to magnetic self-guiding in the former case, and ∇n ×∇T magnetic fields in the latter. Using a realistic, quasi two-temperature energy spectrum derived from PIC laser-plasma simulations increases Efig to (102, 81, 162 kJ for (no E/B, E = ηJb, full Ohm's law. Such electrons are too energetic to stop in the optimal hot spot depth.

  19. A haptic unit designed for magnetic-resonance-guided biopsy.

    Science.gov (United States)

    Tse, Z T H; Elhawary, H; Rea, M; Young, I; Davis, B L; Lamperth, M

    2009-02-01

    The magnetic fields present in the magnetic resonance (MR) environment impose severe constraints on any mechatronic device present in its midst, requiring alternative actuators, sensors, and materials to those conventionally used in traditional system engineering. In addition the spatial constraints of closed-bore scanners require a physical separation between the radiologist and the imaged region of the patient. This configuration produces a loss of the sense of touch from the target anatomy for the clinician, which often provides useful information. To recover the force feedback from the tissue, an MR-compatible haptic unit, designed to be integrated with a five-degrees-of-freedom mechatronic system for MR-guided prostate biopsy, has been developed which incorporates position control and force feedback to the operator. The haptic unit is designed to be located inside the scanner isocentre with the master console in the control room. MR compatibility of the device has been demonstrated, showing a negligible degradation of the signal-to-noise ratio and virtually no geometric distortion. By combining information from the position encoder and force sensor, tissue stiffness measurement along the needle trajectory is demonstrated in a lamb liver to aid diagnosis of suspected cancerous tissue.

  20. 3-Tesla functional magnetic resonance imaging-guided tumor resection

    International Nuclear Information System (INIS)

    Hall, W.A.; Truwit, C.L.; Univ. of Minnesota Medical School, Minneapolis, MN; Univ. of Minnesota Medical School, Minneapolis, MN; Hennepin Country Medical Center, Minneapolis, MN

    2006-01-01

    Objective: We sought to determine the safety and efficacy of using 3-tesla (T) functional magnetic resonance imaging (fMRI) to guide brain tumor resection. Material and methods: From February 2004 to March 2006, fMRI was performed on 13 patients before surgical resection. Functional imaging was used to identify eloquent cortices for motor (8), speech (3), and motor and speech (2) activation using two different 3-T magnetic resonance (MR) scanners. Surgical resection was accomplished using a 1.5-T intraoperative MR system. Appropriate MR scan sequences were performed intraoperatively to determine and maximize the extent of the surgical resection. Results: Tumors included six oligodendrogliomas, three meningiomas, two astrocytomas and two glioblastomas multiforme. The fMRI data was accurate in all cases. After surgery, two patients had hemiparesis, two had worsening of their speech, and one had worsening of speech and motor function. Neurological function returned to normal in all patients within 1 month. Complete resections were possible in 10 patients (77%). Two patients had incomplete resections because of the proximity of their tumors to functional areas. Biopsy was performed in another patient with an astrocytoma in the motor strip. Conclusion: 3-T fMRI was accurate for locating neurologic function before tumor resection near eloquent cortex. (orig.)

  1. Comptonization in Ultra-Strong Magnetic Fields: Numerical Solution to the Radiative Transfer Problem

    Science.gov (United States)

    Ceccobello, C.; Farinelli, R.; Titarchuk, L.

    2014-01-01

    We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in the presence of an ultra-strong magnetic field (B approximately greater than B(sub c) approx. = 4.4 x 10(exp 13) G). Under these conditions, the magnetic field behaves like a birefringent medium for the propagating photons, and the electromagnetic radiation is split into two polarization modes, ordinary and extraordinary, that have different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are strongly Comptonized and the photon field is dominated by an isotropic component. Aims. The radiative transfer problem in strong magnetic fields presents many mathematical issues and analytical or numerical solutions can be obtained only under some given approximations. We investigate this problem both from the analytical and numerical point of view, provide a test of the previous analytical estimates, and extend these results with numerical techniques. Methods. We consider here the case of low temperature black-body photons propagating in a sub-relativistic temperature plasma, which allows us to deal with a semi-Fokker-Planck approximation of the radiative transfer equation. The problem can then be treated with the variable separation method, and we use a numerical technique to find solutions to the eigenvalue problem in the case of a singular kernel of the space operator. The singularity of the space kernel is the result of the strong angular dependence of the electron cross-section in the presence of a strong magnetic field. Results. We provide the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and the emerging Comptonization spectrum of the ordinary-mode photons for any eigenvalue of the space equation and for energies significantly lesser than the cyclotron energy, which is on the order of MeV for the intensity of the magnetic field here considered. Conclusions. We derived the specific intensity of the

  2. Navigation concepts for magnetic resonance imaging-guided musculoskeletal interventions.

    Science.gov (United States)

    Busse, Harald; Kahn, Thomas; Moche, Michael

    2011-08-01

    Image-guided musculoskeletal (MSK) interventions are a widely used alternative to open surgical procedures for various pathological findings in different body regions. They traditionally involve one of the established x-ray imaging techniques (radiography, fluoroscopy, computed tomography) or ultrasound scanning. Over the last decades, magnetic resonance imaging (MRI) has evolved into one of the most powerful diagnostic tools for nearly the whole body and has therefore been increasingly considered for interventional guidance as well.The strength of MRI for MSK applications is a combination of well-known general advantages, such as multiplanar and functional imaging capabilities, wide choice of tissue contrasts, and absence of ionizing radiation, as well as a number of MSK-specific factors, for example, the excellent depiction of soft-tissue tumors, nonosteolytic bone changes, and bone marrow lesions. On the downside, the magnetic resonance-compatible equipment needed, restricted space in the magnet, longer imaging times, and the more complex workflow have so far limited the number of MSK procedures under MRI guidance.Navigation solutions are generally a natural extension of any interventional imaging system, in particular, because powerful hardware and software for image processing have become routinely available. They help to identify proper access paths, provide accurate feedback on the instrument positions, facilitate the workflow in an MRI environment, and ultimately contribute to procedural safety and success.The purposes of this work were to describe some basic concepts and devices for MRI guidance of MSK procedures and to discuss technical and clinical achievements and challenges for some selected implementations.

  3. The Effect of a Guide Field on the Structures of Magnetic Islands: 2D PIC Simulations

    Science.gov (United States)

    Huang, C.; Lu, Q.; Lu, S.; Wang, P.; Wang, S.

    2014-12-01

    Magnetic island plays an important role in magnetic reconnection. Using a series of 2D PIC simulations, we investigate the magnetic structures of a magnetic island formed during multiple X-line magnetic reconnection, considering the effects of the guide field in symmetric and asymmetric current sheets. In a symmetric current sheet, the current in the direction forms a tripolar structure inside a magnetic island during anti-parallel reconnection, which results in a quadrupole structure of the out-of-plane magnetic field. With the increase of the guide field, the symmetry of both the current system and out-of-plane magnetic field inside the magnetic island is distorted. When the guide field is sufficiently strong, the current forms a ring along the magnetic field lines inside magnetic island. At the same time, the current carried by the energetic electrons accelerated in the vicinity of the X lines forms another ring at the edge of the magnetic island. Such a dual-ring current system enhance the out-of-plane magnetic field inside the magnetic island with a dip in the center of the magnetic island. In an asymmetric current sheet, when there is no guide field, electrons flows toward the X lines along the separatrices from the side with a higher density, and are then directed away from the X lines along the separatrices to the side with a lower density. The formed current results in the enhancement of the out-of-plane magnetic field at one end of the magnetic island, and the attenuation at the other end. With the increase of the guide field, the structures of both the current system and the out-of-plane magnetic field are distorted.

  4. Ultra-small superparamagnetic particles of iron oxide in magnetic resonance imaging of cardiovascular disease

    Directory of Open Access Journals (Sweden)

    Stirrat CG

    2014-10-01

    Full Text Available Colin G Stirrat,1 Alex T Vesey,1 Olivia MB McBride,1 Jennifer MJ Robson,1 Shirjel R Alam,1 William A Wallace,2 Scott I Semple,1,3 Peter A Henriksen,1 David E Newby1 1British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK; 2Department of Pathology, University of Edinburgh, Edinburgh, UK; 3Clinical Research Imaging Centre, University of Edinburgh, Edinburgh, UK Abstract: Ultra-small superparamagnetic particles of iron oxide (USPIO are iron-oxide based contrast agents that enhance and complement in vivo magnetic resonance imaging (MRI by shortening T1, T2, and T2* relaxation times. USPIO can be employed to provide immediate blood pool contrast, or to act as subsequent markers of cellular inflammation through uptake by inflammatory cells. They can also be targeted to specific cell-surface markers using antibody or ligand labeling. This review will discuss the application of USPIO contrast in MRI studies of cardiovascular disease. Keywords: cardiac, aortic, MRI, USPIO, carotid, vascular, molecular imaging

  5. Cinematic study of temporomandibular joint motion using ultra-fast magnetic resonance imaging.

    Science.gov (United States)

    Manière-Ezvan, A; Havet, T; Franconi, J M; Quémar, J C; de Certaines, J D

    1999-10-01

    Magnetic Resonance Images (MRI) of the temporomandibular joint (TMJ) are usually performed to study the opening/closing movements of the mandible and have up to now been pseudodynamic step-by-step images simulating condylar motion by post-processing reconstruction. The aim of this study was: 1. to optimize a TMJ cine-imaging method to give a better clinical result than the step-by-step methods; 2. to develop an ultra-fast MRI Gradient Echo (GE) sequence for this purpose; and 3. to analyze condylar movements in the sagittal, coronal and para-axial planes during border mandibular displacements and chewing. Both TM joints were studied in six asymptomatic volunteers. The method involved a compromise between in-plane resolution, slice thickness, signal-to-noise ratio and time resolution. Routine clinical use was found to be a GE pulse sequence providing three images per second with an isometric voxel resolution of approximately two millimeters in ridge. This did not allow visualization of the disk. Using this sequence enabled real and simultaneous condylar displacement observation in the three planes of space and therefore contributed to a better functional diagnosis of pathologic TMJ motions.

  6. An intra-neural microstimulation system for ultra-high field magnetic resonance imaging and magnetoencephalography.

    Science.gov (United States)

    Glover, Paul M; Watkins, Roger H; O'Neill, George C; Ackerley, Rochelle; Sanchez-Panchuelo, Rosa; McGlone, Francis; Brookes, Matthew J; Wessberg, Johan; Francis, Susan T

    2017-10-01

    Intra-neural microstimulation (INMS) is a technique that allows the precise delivery of low-current electrical pulses into human peripheral nerves. Single unit INMS can be used to stimulate individual afferent nerve fibres during microneurography. Combining this with neuroimaging allows the unique monitoring of central nervous system activation in response to unitary, controlled tactile input, with functional magnetic resonance imaging (fMRI) providing exquisite spatial localisation of brain activity and magnetoencephalography (MEG) high temporal resolution. INMS systems suitable for use within electrophysiology laboratories have been available for many years. We describe an INMS system specifically designed to provide compatibility with both ultra-high field (7T) fMRI and MEG. Numerous technical and safety issues are addressed. The system is fully analogue, allowing for arbitrary frequency and amplitude INMS stimulation. Unitary recordings obtained within both the MRI and MEG screened-room environments are comparable with those obtained in 'clean' electrophysiology recording environments. Single unit INMS (current met. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

  7. Transducer project and optimization of the ultra low magnetic field NMR tomograph reception system system

    International Nuclear Information System (INIS)

    Vidoto, Edson Luiz Gea

    1995-01-01

    The aim of the present work was to optimize the signal to noise ratio in our NMR imaging system (TORM 005) by improving transducer's reception quality through better designed coils, balanced tuning circuit for this coils and power decoupling circuits and by reducing interference from the electromagnetic environment. For this purpose, we had to modify the internal electromagnetic shielding and incorporate line filters in the more critical signals paths. Also, new types of coils were developed, improving the signal to noise ratio, and allowing us to make clinical exams with superior quality for several anatomies. Balanced circuits for tuning and matching of the coil were studied and built, allowing a reduction of the coil losses because patient's load. This produced a more reliable coil tuning after positioning each new patient. Circuits to avoid the receiver input overload and decoupling circuits for the isolation of receiver coils from excitation coil were designed and incorporated to the TORM 005. All these alterations of our imaging system (TORM 005) contributed to a significant improvement in the signal to noise ratio, reliability and reproducibility of the system. This permitted to operate the system routinely for clinical applications, research and development in the area of ultra low magnetic field tomography. (author)

  8. A planar conducting microstructure to guide and confine magnetic beads to a sensing zone

    KAUST Repository

    Gooneratne, Chinthaka Pasan

    2011-08-01

    A novel planar conducting microstructure is proposed to transport and confine magnetic micro/nano beads to a sensing zone. Manipulation and concentration of magnetic beads are achieved by employing square-shaped conducting micro-loops, with a few hundred nano-meters in thickness, arranged in a unique fashion. These microstructures are designed to produce high magnetic field gradients which are directly proportional to the force applied to manipulate the magnetic beads. Furthermore, the size of the microstructures allows greater maneuverability and control of magnetic beads than what could be achieved by permanent magnets. The aim of the microstructures is to guide magnetic beads from a large area and confine them to a smaller area where for example quantification would take place. Experiments were performed with different concentrations of 2 μm diameter magnetic beads. Experimental results showed that magnetic beads could be successfully guided and confined to the sensing zone. © 2011 Elsevier B.V. All rights reserved.

  9. Passive shimming of the fringe field of a superconducting magnet for ultra-low field hyperpolarized noble gas MRI.

    Science.gov (United States)

    Parra-Robles, Juan; Cross, Albert R; Santyr, Giles E

    2005-05-01

    Hyperpolarized noble gases (HNGs) provide exciting possibilities for MR imaging at ultra-low magnetic field strengths (superconductive magnets used in clinical MR imaging can provide a stable magnetic field for this purpose. In addition to offering the benefit of HNG MR imaging alongside conventional high field proton MRI, this approach offers the other useful advantage of providing different field strengths at different distances from the magnet. However, the extremely strong field gradients associated with the fringe field present a major challenge for imaging since impractically high active shim currents would be required to achieve the necessary homogeneity. In this work, a simple passive shimming method based on the placement of a small number of ferromagnetic pieces is proposed to reduce the fringe field inhomogeneities to a level that can be corrected using standard active shims. The method explicitly takes into account the strong variations of the field over the volume of the ferromagnetic pieces used to shim. The method is used to obtain spectra in the fringe field of a high-field (1.89 T) superconducting magnet from hyperpolarized 129Xe gas samples at two different ultra-low field strengths (8.5 and 17 mT). The linewidths of spectra measured from imaging phantoms (30 Hz) indicate a homogeneity sufficient for MRI of the rat lung.

  10. Running Performance of a Pinning-Type Superconducting Magnetic Levitation Guide

    International Nuclear Information System (INIS)

    Okano, M; Iwamoto, T; Furuse, M; Fuchino, S; Ishii, I

    2006-01-01

    A pinning-type superconducting magnetic levitation guide with bulk high-Tc superconductors was studied for use as a goods transportation system, an energy storage system, etc. A superconducting magnetic levitation running test apparatus with a circular track of ca. 38 m length, 12 m diameter, which comprises the magnetic rail constituted by Nd-B-Fe rare-earth permanent magnets and steel plates, was manufactured to examine loss and high-speed performance of the magnetic levitation guide. Running tests were conducted in air. These tests clarify that a vehicle supported by a superconducting magnetic levitation guide runs stably at speeds greater than 42 km/h above the circular track

  11. Running Performance of a Pinning-Type Superconducting Magnetic Levitation Guide

    Science.gov (United States)

    Okano, M.; Iwamoto, T.; Furuse, M.; Fuchino, S.; Ishii, I.

    2006-06-01

    A pinning-type superconducting magnetic levitation guide with bulk high-Tc superconductors was studied for use as a goods transportation system, an energy storage system, etc. A superconducting magnetic levitation running test apparatus with a circular track of ca. 38 m length, 12 m diameter, which comprises the magnetic rail constituted by Nd-B-Fe rare-earth permanent magnets and steel plates, was manufactured to examine loss and high-speed performance of the magnetic levitation guide. Running tests were conducted in air. These tests clarify that a vehicle supported by a superconducting magnetic levitation guide runs stably at speeds greater than 42 km/h above the circular track.

  12. Surgical neuro navigator guided by preoperative magnetic resonance images, based on a magnetic position sensor

    International Nuclear Information System (INIS)

    Perini, Ana Paula; Siqueira, Rogerio Bulha; Carneiro, Antonio Adilton Oliveira; Oliveira, Lucas Ferrari de; Machado, Helio Rubens

    2009-01-01

    Image guided neurosurgery enables the neurosurgeon to navigate inside the patient's brain using pre-operative images as a guide and a tracking system, during a surgery. Following a calibration procedure, three-dimensional position and orientation of surgical instruments may be transmitted to computer. The spatial information is used to access a region of interest, in the pre-operative images, displaying them to the neurosurgeon during the surgical procedure. However, when a craniotomy is involved and the lesion is removed, movements of brain tissue can be a significant source of error in these conventional navigation systems. The architecture implemented in this work intends the development of a system to surgical planning and orientation guided by ultrasound image. For surgical orientation, the software developed allows the extraction of slices from the volume of the magnetic resonance images (MRI) with orientation supplied by a magnetic position sensor (Polhemus R ). The slices extracted with this software are important because they show the cerebral area that the neurosurgeon is observing during the surgery, and besides they can be correlated with the intra-operative ultrasound images to detect and to correct the deformation of brain tissue during the surgery. Also, a tool for per-operative navigation was developed, providing three orthogonal planes through the image volume. In the methodology used for the software implementation, the Python tm programming language and the Visualization Toolkit (VTK) graphics library were used. The program to extract slices of the MRI volume allowed the application of transformations in the volume, using coordinates supplied by the position sensor. (author)

  13. Bloqueios nervosos guiados por ultra-som Bloqueos nerviosos guiados por ultrasonido Ultrasound-guided nerve blocks

    Directory of Open Access Journals (Sweden)

    Pablo Escovedo Helayel

    2007-02-01

    referencias anatómicas, menor volumenn de solución anestésica y una mayor seguridad. CONCLUSION: El artículo revisa los aspectos relativos a los mecanismos físicos para la formación de imágenes, la anatomía ultra sonográfica del neuro eje y de los plexos braquial y lumbo sacral, los equipos y materiales empleados en los bloqueos, los ajustes del aparato de ultrasonido para mejorar las imágenes, los planos de visualización de las agujas de bloqueo y las técnicas y el entrenamiento en bloqueos guiados por ultrasonido. CONCLUSIONES: Los pasos para obtener el éxito en anestesia regional incluyen la identificación exacta de la posición de los nervios, la localización precisa de la aguja, sin lesiones en las estructuras adyacentes y, finalmente, la inyección cuidadosa de anestésico local junto a los nervios. Aunque la neuro estimulación sea de gran ayuda en la identificación de los nervios, ella no logra, aisladamente, rellenar todas esas exigencias. A causa de eso, se cree que los bloqueos guiados por ultrasonido serán la técnica de elección para la anestesia regional en un futuro no muy distante.BACKGROUND AND OBJECTIVES: Ultrasound-guided nerve blocks are based on the direct visualization of nerve structures, needle, and adjacent anatomic structures. Thus, it is possible to place the local anesthetic precisely around the nerves and follow its dispersion in real time, obtaining, therefore, more effective blockades, reduced dependency on anatomic references, decreased anesthetic volume, and increased safety. CONTENTS: The aim of this paper was to review the physical mechanisms of image formation, ultrasound anatomy of the neuro axis and of the brachial and lumbosacral plexuses, equipment and materials used in the blockades, settings of the ultrasound equipment to improve the image, planes of visualization of the needles, the techniques, and training in ultrasound-guided nerve blocks. CONCLUSIONS: The steps for a successful regional block include the

  14. MAGNETICALLY DRIVEN ACCRETION DISK WINDS AND ULTRA-FAST OUTFLOWS IN PG 1211+143

    International Nuclear Information System (INIS)

    Fukumura, Keigo; Tombesi, Francesco; Kazanas, Demosthenes; Shrader, Chris; Behar, Ehud; Contopoulos, Ioannis

    2015-01-01

    We present a study of X-ray ionization of MHD accretion-disk winds in an effort to constrain the physics underlying the highly ionized ultra-fast outflows (UFOs) inferred by X-ray absorbers often detected in various sub classes of Seyfert active galactic nuclei (AGNs). Our primary focus is to show that magnetically driven outflows are indeed physically plausible candidates for the observed outflows accounting for the AGN absorption properties of the present X-ray spectroscopic observations. Employing a stratified MHD wind launched across the entire AGN accretion disk, we calculate its X-ray ionization and the ensuing X-ray absorption-line spectra. Assuming an appropriate ionizing AGN spectrum, we apply our MHD winds to model the absorption features in an XMM-Newton/EPIC spectrum of the narrow-line Seyfert, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log (ξ c [erg cm s −1 ]) ≃ 5–6 and a column density on the order of N H ≃ 10 23 cm −2 outflowing at a characteristic velocity of v c /c ≃ 0.1–0.2 (where c is the speed of light). The best-fit model favors its radial location at r c ≃ 200 R o (R o is the black hole’s innermost stable circular orbit), with an inner wind truncation radius at R t ≃ 30 R o . The overall K-shell feature in the data is suggested to be dominated by Fe xxv with very little contribution from Fe xxvi and weakly ionized iron, which is in good agreement with a series of earlier analyses of the UFOs in various AGNs, including PG 1211+143

  15. Simulations of ultra-high energy cosmic rays in the local Universe and the origin of cosmic magnetic fields

    Science.gov (United States)

    Hackstein, S.; Vazza, F.; Brüggen, M.; Sorce, J. G.; Gottlöber, S.

    2018-04-01

    We simulate the propagation of cosmic rays at ultra-high energies, ≳1018 eV, in models of extragalactic magnetic fields in constrained simulations of the local Universe. We use constrained initial conditions with the cosmological magnetohydrodynamics code ENZO. The resulting models of the distribution of magnetic fields in the local Universe are used in the CRPROPA code to simulate the propagation of ultra-high energy cosmic rays. We investigate the impact of six different magneto-genesis scenarios, both primordial and astrophysical, on the propagation of cosmic rays over cosmological distances. Moreover, we study the influence of different source distributions around the Milky Way. Our study shows that different scenarios of magneto-genesis do not have a large impact on the anisotropy measurements of ultra-high energy cosmic rays. However, at high energies above the Greisen-Zatsepin-Kuzmin (GZK)-limit, there is anisotropy caused by the distribution of nearby sources, independent of the magnetic field model. This provides a chance to identify cosmic ray sources with future full-sky measurements and high number statistics at the highest energies. Finally, we compare our results to the dipole signal measured by the Pierre Auger Observatory. All our source models and magnetic field models could reproduce the observed dipole amplitude with a pure iron injection composition. Our results indicate that the dipole is observed due to clustering of secondary nuclei in direction of nearby sources of heavy nuclei. A light injection composition is disfavoured, since the increase in dipole angular power from 4 to 8 EeV is too slow compared to observation by the Pierre Auger Observatory.

  16. Development of biodegradable scaffolds based on magnetically guided assembly of magnetic sugar particles.

    Science.gov (United States)

    Hu, Chengzhi; Uchida, Tomoyuki; Tercero, Carlos; Ikeda, Seiichi; Ooe, Katsutoshi; Fukuda, Toshio; Arai, Fumihito; Negoro, Makoto; Kwon, Guiryong

    2012-05-31

    Biodegradable scaffolds with controlled pore layout and porosity have great significance in tissue engineering for cell penetration, tissue ingrowth, vascularization, and nutrient delivery. Porogen leaching has been commonly used to control pore size, pore structure and porosity in the scaffold. In this paper we focus on the use/development of two magnetically guided porogen assembly methods using magnetic sugar particles (MSPs) for scaffold fabrication. First, a patterning device is utilized to align MSPs following designed templates. Then a magnetic sheet film is fabricated by mixing poly(vinyl alcohol, PVA) and NdFeB powder for steering the MSPs. After poly(l-lactide-co-ɛ-caprolactone) (PLCL) casting and removal of the sugar template, a scaffold with spherical pores is obtained. The surface and the inner structure of the scaffolds are evaluated using light and electron micrographs showing their interconnection of pores, pore wall morphology and porosity. Single layer scaffolds with the size of 8mm in width and 10mm in length were constructed with controllable pore diameters in the ranges of 105-150 μm, 250-300 μm and 425-500 μm. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Kinematic analysis and simulation of a substation inspection robot guided by magnetic sensor

    Science.gov (United States)

    Xiao, Peng; Luan, Yiqing; Wang, Haipeng; Li, Li; Li, Jianxiang

    2017-01-01

    In order to improve the performance of the magnetic navigation system used by substation inspection robot, the kinematic characteristics is analyzed based on a simplified magnetic guiding system model, and then the simulation process is executed to verify the reasonability of the whole analysis procedure. Finally, some suggestions are extracted out, which will be helpful to guide the design of the inspection robot system in the future.

  18. [Laparoscopic and general surgery guided by open interventional magnetic resonance].

    Science.gov (United States)

    Lauro, A; Gould, S W T; Cirocchi, R; Giustozzi, G; Darzi, A

    2004-10-01

    Interventional magnetic resonance (IMR) machines have produced unique opportunity for image-guided surgery. The open configuration design and fast pulse sequence allow virtual real time intraoperative scanning to monitor the progress of a procedure, with new images produced every 1.5 sec. This may give greater appreciation of anatomy, especially deep to the 2-dimensional laparoscopic image, and hence increase safety, reduce procedure magnitude and increase confidence in tumour resection surgery. The aim of this paper was to investigate the feasibility of performing IMR-image-guided general surgery, especially in neoplastic and laparoscopic field, reporting a single center -- St. Mary's Hospital (London, UK) -- experience. Procedures were carried out in a Signa 0.5 T General Elettric SP10 Interventional MR (General Electric Medical Systems, Milwaukee, WI, USA) with magnet-compatible instruments (titanium alloy instruments, plastic retractors and ultrasonic driven scalpel) and under general anesthesia. There were performed 10 excision biopsies of palpable benign breast tumors (on female patients), 3 excisions of skin sarcoma (dermatofibrosarcoma protuberans), 1 right hemicolectomy and 2 laparoscopic cholecystectomies. The breast lesions were localized with pre- and postcontrast (intravenous gadolinium DPTA) sagittal and axial fast multiplanar spoiled gradient recalled conventional Signa sequences; preoperative real time fast gradient recalled sequences were also obtained using the flashpoint tracking device. During right hemicolectomy intraoperative single shot fast spin echo (SSFSE) and fast spoiled gradient recalled (FSPGR) imaging of right colon were performed after installation of 150 cc of water or 1% gadolinium solution, respectively, through a Foley catheter; imaging was also obtained in an attempt to identify mesenteric lymph nodes intraoperatively. Concerning laparoscopic procedures, magnetic devices (insufflator, light source) were positioned outside scan

  19. Silicon nitride gradient film as the underlayer of ultra-thin tetrahedral amorphous carbon overcoat for magnetic recording slider

    Energy Technology Data Exchange (ETDEWEB)

    Wang Guigen, E-mail: wanggghit@yahoo.com [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Kuang Xuping; Zhang Huayu; Zhu Can [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Han Jiecai [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Center for Composite Materials, Harbin Institute of Technology, Harbin 150080 (China); Zuo Hongbo [Center for Composite Materials, Harbin Institute of Technology, Harbin 150080 (China); Ma Hongtao [SAE Technologies Development (Dongguan) Co., Ltd., Dongguan 523087 (China)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer The ultra-thin carbon films with different silicon nitride (Si-N) film underlayers were prepared. Black-Right-Pointing-Pointer It highlighted the influences of Si-N underlayers. Black-Right-Pointing-Pointer The carbon films with Si-N underlayers obtained by nitriding especially at the substrate bias of -150 V, can exhibit better corrosion protection properties - Abstract: There are higher technical requirements for protection overcoat of magnetic recording slider used in high-density storage fields for the future. In this study, silicon nitride (Si-N) composition-gradient films were firstly prepared by nitriding of silicon thin films pre-sputtered on silicon wafers and magnetic recording sliders, using microwave electron cyclotron resonance plasma source. The ultra-thin tetrahedral amorphous carbon films were then deposited on the Si-N films by filtered cathodic vacuum arc method. Compared with amorphous carbon overcoats with conventional silicon underlayers, the overcoats with Si-N underlayers obtained by plasma nitriding especially at the substrate bias of -150 V, can provide better corrosion protection for high-density magnetic recording sliders.

  20. Silicon nitride gradient film as the underlayer of ultra-thin tetrahedral amorphous carbon overcoat for magnetic recording slider

    International Nuclear Information System (INIS)

    Wang Guigen; Kuang Xuping; Zhang Huayu; Zhu Can; Han Jiecai; Zuo Hongbo; Ma Hongtao

    2011-01-01

    Highlights: ► The ultra-thin carbon films with different silicon nitride (Si-N) film underlayers were prepared. ► It highlighted the influences of Si-N underlayers. ► The carbon films with Si-N underlayers obtained by nitriding especially at the substrate bias of −150 V, can exhibit better corrosion protection properties - Abstract: There are higher technical requirements for protection overcoat of magnetic recording slider used in high-density storage fields for the future. In this study, silicon nitride (Si-N) composition-gradient films were firstly prepared by nitriding of silicon thin films pre-sputtered on silicon wafers and magnetic recording sliders, using microwave electron cyclotron resonance plasma source. The ultra-thin tetrahedral amorphous carbon films were then deposited on the Si-N films by filtered cathodic vacuum arc method. Compared with amorphous carbon overcoats with conventional silicon underlayers, the overcoats with Si-N underlayers obtained by plasma nitriding especially at the substrate bias of −150 V, can provide better corrosion protection for high-density magnetic recording sliders.

  1. Metamaterial-based transmit and receive system for whole-body magnetic resonance imaging at ultra-high magnetic fields.

    Science.gov (United States)

    Herrmann, Tim; Liebig, Thorsten; Mallow, Johannes; Bruns, Christian; Stadler, Jörg; Mylius, Judith; Brosch, Michael; Svedja, Jan Taro; Chen, Zhichao; Rennings, Andreas; Scheich, Henning; Plaumann, Markus; Hauser, Marcus J B; Bernarding, Johannes; Erni, Daniel

    2018-01-01

    Magnetic resonance imaging (MRI) at ultra-high fields (UHF), such as 7 T, provides an enhanced signal-to-noise ratio and has led to unprecedented high-resolution anatomic images and brain activation maps. Although a variety of radio frequency (RF) coil architectures have been developed for imaging at UHF conditions, they usually are specialized for small volumes of interests (VoI). So far, whole-body coil resonators are not available for commercial UHF human whole-body MRI systems. The goal of the present study was the development and validation of a transmit and receive system for large VoIs that operates at a 7 T human whole-body MRI system. A Metamaterial Ring Antenna System (MRAS) consisting of several ring antennas was developed, since it allows for the imaging of extended VoIs. Furthermore, the MRAS not only requires lower intensities of the irradiated RF energy, but also provides a more confined and focused injection of excitation energy on selected body parts. The MRAS consisted of several antennas with 50 cm inner diameter, 10 cm width and 0.5 cm depth. The position of the rings was freely adjustable. Conformal resonant right-/left-handed metamaterial was used for each ring antenna with two quadrature feeding ports for RF power. The system was successfully implemented and demonstrated with both a silicone oil and a water-NaCl-isopropanol phantom as well as in vivo by acquiring whole-body images of a crab-eating macaque. The potential for future neuroimaging applications was demonstrated by the acquired high-resolution anatomic images of the macaque's head. Phantom and in vivo measurements of crab-eating macaques provided high-resolution images with large VoIs up to 40 cm in xy-direction and 45 cm in z-direction. The results of this work demonstrate the feasibility of the MRAS system for UHF MRI as proof of principle. The MRAS shows a substantial potential for MR imaging of larger volumes at 7 T UHF. This new technique may provide new diagnostic potential

  2. Development of a movable table for a bending magnet with removable guides

    International Nuclear Information System (INIS)

    Shibuya, T.; Ito, I.; Kudoh, H.

    2004-01-01

    We develop the movable table for a bending magnet with removable guides. This table has two parallel rails in order to move the bending magnet smoothly and set it precisely. Especially this table has two removable expanded rail guides. Removing this expanded rail guides allow us to make more enough spaces, for example, to install another insertion devices. We measure the reliability of setting this table by moving this table along the rails. And we found this reliability is less than ±3 μm. We also measure the long-term stability of this table setting. (author)

  3. Ulysses Observations of Tripolar Guide-Magnetic Field Perturbations Across Solar Wind Reconnection Exhausts

    Science.gov (United States)

    Eriksson, S.; Peng, B.; Markidis, S.; Gosling, J. T.; McComas, D. J.; Lapenta, G.; Newman, D. L.

    2014-12-01

    We report observations from 15 solar wind reconnection exhausts encountered along the Ulysses orbit beyond 4 AU in 1996-1999 and 2002-2005. The events, which lasted between 17 and 45 min, were found at heliospheric latitudes between -36o and 21o with one event detected as high as 58o. All events shared a common characteristic of a tripolar guide-magnetic field perturbation being detected across the observed exhausts. The signature consists of an enhanced guide field magnitude within the exhaust center and two regions of significantly depressed guide-fields adjacent to the center region. The events displayed magnetic field shear angles as low as 37o with a mean of 89o. This corresponds to a strong external guide field relative to the anti-parallel reconnecting component of the magnetic field with a mean ratio of 1.3 and a maximum ratio of 3.1. A 2-D kinetic reconnection simulation for realistic solar wind conditions reveals that tripolar guide fields form at current sheets in the presence of multiple X-lines as two magnetic islands interact with one another for such strong guide fields. The Ulysses observations are also compared with the results of a 3-D kinetic simulation of multiple flux ropes in a strong guide field.

  4. Review of magnetic resonance-guided focused ultrasound in the treatment of uterine fibroids

    Directory of Open Access Journals (Sweden)

    Pedro Felipe Magalhães Peregrino

    Full Text Available Uterine leiomyoma is the most frequently occurring solid pelvic tumor in women during the reproductive period. Magnetic resonance-guided high-intensity focused ultrasound is a promising technique for decreasing menorrhagia and dysmenorrhea in symptomatic women. The aim of this study is to review the role of Magnetic resonance-guided high-intensity focused ultrasound in the treatment of uterine fibroids in symptomatic patients. We performed a review of the MEDLINE and Cochrane databases up to April 2016. The analysis and data collection were performed using the following keywords: Leiomyoma, High-Intensity Focused Ultrasound Ablation, Ultrasonography, Magnetic Resonance Imaging, Menorrhagia. Two reviewers independently performed a quality assessment; when there was a disagreement, a third reviewer was consulted. Nineteen studies of Magnetic resonance-guided high-intensity focused ultrasound-treated fibroid patients were selected. The data indicated that tumor size was reduced and that symptoms were improved after treatment. There were few adverse effects, and they were not severe. Some studies have reported that in some cases, additional sessions of Magnetic resonance-guided high-intensity focused ultrasound or other interventions, such as myomectomy, uterine artery embolization or even hysterectomy, were necessary. This review suggests that Magnetic resonance-guided high-intensity focused ultrasound is a safe and effective technique. However, additional evidence from future studies will be required before the technique can be recommended as an alternative treatment for fibroids.

  5. Magnetically-guided assembly of microfluidic fibers for ordered construction of diverse netlike modules

    Science.gov (United States)

    Li, Xingfu; Shi, Qing; Wang, Huaping; Sun, Tao; Huang, Qiang; Fukuda, Toshio

    2017-12-01

    In this paper, a magnetically-guided assembly method is proposed to methodically construct diverse modules with a microfiber-based network for promoting nutrient circulation and waste excretion of cell culture. The microfiber is smoothly spun from the microfluidic device via precise control of the volumetric flow rate, and superparamagnetic nanoparticles within the alginate solution of the microfluidic fiber enable its magnetic response. The magnetized device is used to effectively capture the microfiber using its powerful magnetic flux density and high magnetic field gradient. Subsequently, the dot-matrix magnetic flux density is used to distribute the microfibers in an orderly fashion that depends on the array structure of the magnetized device. Furthermore, the magnetic microfluidic fibers are spatially organized into desired locations and are cross-aligned to form highly interconnected netlike modules in a liquid environment. Therefore, the experimental results herein demonstrate the structural controllability and stability of various modules and establish the effectiveness of the proposed method.

  6. Natural time analysis on the ultra-low frequency magnetic field variations prior to the 2016 Kumamoto (Japan) earthquakes

    Science.gov (United States)

    Potirakis, Stelios M.; Schekotov, Alexander; Asano, Tomokazu; Hayakawa, Masashi

    2018-04-01

    On 15 April 2016 a very strong and shallow earthquake (EQ) (MW = 7.0 , depth ∼ 10 km) occurred in Southwest Japan under the city of Kumamoto, while two very strong foreshocks (MW = 6.2 and MW = 6.0) preceded by about one day. The Kumamoto EQs being very catastrophic, have already attracted much attention among the scientific community in a quest for understanding the generation mechanism, as well as for reporting any preseismic anomalies in various observables and assessing the effectivity of the current early warning systems. In the present article we report precursory behavior of the ground-based observed ultra-low frequency (ULF) magnetic field variations before the Kumamoto EQs. By analyzing specific ULF magnetic field characteristics in terms of the recently introduced natural time (NT) analysis method, we identified that ULF magnetic field variations presented critical features from 2 weeks up to 1 month before the Kumamoto EQs. Specifically, the ULF magnetic field characteristics Fh , Fz , Dh and δDep were analyzed. The first two represent variations of the horizontal and vertical components of the geomagnetic field. The third and fourth characteristics correspond to the depression (decrease) and a relative depression of the horizontal magnetic field variations, respectively. The latter depends on the degree of ionospheric disturbance. All of them were found to reach criticality before the Kumamoto EQs; however, in different time periods for each characteristic.

  7. Simulation and experimental study on transportation of dual-beam guided by confining magnetic-field

    International Nuclear Information System (INIS)

    Bai Xianchen; Zhang Jiande; Yang Jianhua

    2008-01-01

    Using external longitudinal magnetic-field to guide dual-beam out of the dual-shift tubes is a key step for the practicality of synchronizing dual-beam produced by a single accelerator. On the basis of the simulation of the confining magnetic-field for the solid dual-beam, the experiment of magnetic-field guiding annular dual-beam was presented. When the diode voltage was 380 kV, dual-beam currents of 5.10 kA and 4.92 kA were obtained. The experimental results indicate that the designed magnetic-field system could confine the annular dual-beam effectively, and the critical confining magnetic-field is about 0.5 T. (authors)

  8. Theoretical predictions for spatially-focused heating of magnetic nanoparticles guided by magnetic particle imaging field gradients

    Energy Technology Data Exchange (ETDEWEB)

    Dhavalikar, Rohan [Department of Chemical Engineering, University of Florida, 1030 Center Drive, Gainesville, FL 32611 (United States); Rinaldi, Carlos, E-mail: carlos.rinaldi@bme.ufl.edu [Department of Chemical Engineering, University of Florida, 1030 Center Drive, Gainesville, FL 32611 (United States); J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive, Gainesville, FL 32611 (United States)

    2016-12-01

    Magnetic nanoparticles in alternating magnetic fields (AMFs) transfer some of the field's energy to their surroundings in the form of heat, a property that has attracted significant attention for use in cancer treatment through hyperthermia and in developing magnetic drug carriers that can be actuated to release their cargo externally using magnetic fields. To date, most work in this field has focused on the use of AMFs that actuate heat release by nanoparticles over large regions, without the ability to select specific nanoparticle-loaded regions for heating while leaving other nanoparticle-loaded regions unaffected. In parallel, magnetic particle imaging (MPI) has emerged as a promising approach to image the distribution of magnetic nanoparticle tracers in vivo, with sub-millimeter spatial resolution. The underlying principle in MPI is the application of a selection magnetic field gradient, which defines a small region of low bias field, superimposed with an AMF (of lower frequency and amplitude than those normally used to actuate heating by the nanoparticles) to obtain a signal which is proportional to the concentration of particles in the region of low bias field. Here we extend previous models for estimating the energy dissipation rates of magnetic nanoparticles in uniform AMFs to provide theoretical predictions of how the selection magnetic field gradient used in MPI can be used to selectively actuate heating by magnetic nanoparticles in the low bias field region of the selection magnetic field gradient. Theoretical predictions are given for the spatial decay in energy dissipation rate under magnetic field gradients representative of those that can be achieved with current MPI technology. These results underscore the potential of combining MPI and higher amplitude/frequency actuation AMFs to achieve selective magnetic fluid hyperthermia (MFH) guided by MPI. - Highlights: • SAR predictions based on a field-dependent magnetization relaxation model.

  9. Electron cyclotron maser instability (ECMI in strong magnetic guide field reconnection

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2017-08-01

    Full Text Available The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guide-field-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is

  10. Electron cyclotron maser instability (ECMI) in strong magnetic guide field reconnection

    Science.gov (United States)

    Treumann, Rudolf A.; Baumjohann, Wolfgang

    2017-08-01

    The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guide-field-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales) electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR) in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects) involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is of particular

  11. Energy flux due to electromagnetic fluctuations during guide field magnetic reconnection

    International Nuclear Information System (INIS)

    Kuwahata, Akihiro; Inomoto, Michiaki; Ono, Yasushi; Yanai, Ryoma

    2016-01-01

    Large electromagnetic fluctuations inside the current sheet and large reconnection electric fields are observed during fast magnetic reconnection in the presence of a guide field. The fluctuations transport 2.5% of the dissipated magnetic energy from the reconnection region. Although the energy gains of the ions and electrons are approximately 60% and 12%, respectively, of the dissipated magnetic energy after the fast reconnection, the energy of fluctuations is not comparable to their energy gains. The fluctuations do not directly contribute to the energy conversion but might cause the fast reconnection leading to the rapid release of magnetic energy. (author)

  12. Design of focussing and guide structures for charged particle beams using rare earth cobalt permanent magnets

    International Nuclear Information System (INIS)

    Halbach, K.

    1981-06-01

    A number of different methods can be used to describe the magnetic properties of oriented Rare Earth Cobalt (REC) material. It will be shown how these different methods of description lead to different ways to think about, and to execute, the design of magnets that are useful for focusing and guiding charged particle beams. It will also be domonstrated that in some of these magnets, the REC material is used in a somewhat unusual way, requiring magnetics properties of the material that are usually not considered to be of great practical importance

  13. Federal Aviation Administration Curriculum Guide for Aviation Magnet Schools Programs

    Science.gov (United States)

    1994-01-01

    Prepared ca. 1994. This publication is designed to provide: : - a brief history of the role of aviation in motivating young : people to learn. : - examples of aviation magnet activities, programs, projects and : school curriculums. : - documentation ...

  14. Particle-in-cell simulations of collisionless magnetic reconnection with a non-uniform guide field

    International Nuclear Information System (INIS)

    Wilson, F.; Neukirch, T.; Harrison, M. G.; Hesse, M.; Stark, C. R.

    2016-01-01

    Results are presented of a first study of collisionless magnetic reconnection starting from a recently found exact nonlinear force-free Vlasov–Maxwell equilibrium. The initial state has a Harris sheet magnetic field profile in one direction and a non-uniform guide field in a second direction, resulting in a spatially constant magnetic field strength as well as a constant initial plasma density and plasma pressure. It is found that the reconnection process initially resembles guide field reconnection, but that a gradual transition to anti-parallel reconnection happens as the system evolves. The time evolution of a number of plasma parameters is investigated, and the results are compared with simulations starting from a Harris sheet equilibrium and a Harris sheet plus constant guide field equilibrium.

  15. Planar Hall ring sensor for ultra-low magnetic moment sensing

    DEFF Research Database (Denmark)

    Hung, Tran Quang; Terki, Ferial; Kamara, Souleymanne

    2015-01-01

    The field sensitivity of a planar Hall effect (PHE) micro-ring type biosensor has been investigated as a function of magnetizing angle of the sensor material, for the sensing of low magnetic moment superparamagnetic labels. The field sensitivity is maximal at a magnetizing angle of α = 20°. At th...

  16. CSR Wake for a Short Magnet in Ultra-Relativistic Limit

    International Nuclear Information System (INIS)

    Emma, Paul J

    2002-01-01

    Using results for the CSR wake in a short magnet [1] we obtain expressions for the wake in the limit of very large values of the relativistic factor γ, γ → ∞, for both the entrance and exit of the magnet. The analytical results are illustrated with numerical computation of the wakes, energy loss and energy spread for magnets of different lengths

  17. On Multiple Reconnection X-lines and Tripolar Perturbations of Strong Guide Magnetic Fields

    Science.gov (United States)

    Eriksson, S.; Lapenta, G.; Newman, D. L.; Phan, T. D.; Gosling, J. T.; Lavraud, B.; Khotyaintsev, Yu. V.; Carr, C. M.; Markidis, S.; Goldman, M. V.

    2015-05-01

    We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar wind reconnection exhaust in the presence of a guide field BM which is almost four times as strong as the reversing field BL. The novel tripolar field consists of two narrow regions of depressed BM, with an observed 7%-14% ΔBM magnitude relative to the external field, which are found adjacent to a wide region of enhanced BM within the exhaust. A stronger reversing field is associated with each BM depression. A kinetic reconnection simulation for realistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentially form across current sheets in the presence of multiple X-lines as magnetic islands approach one another and merge into fewer and larger islands. The simulated ΔBM/ΔXN over the normal width ΔXN between a BM minimum and the edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolar guide field perturbation may be used to identify candidate regions containing multiple X-lines and interacting magnetic islands at individual solar wind current sheets with a strong guide field.

  18. ON MULTIPLE RECONNECTION X-LINES AND TRIPOLAR PERTURBATIONS OF STRONG GUIDE MAGNETIC FIELDS

    International Nuclear Information System (INIS)

    Eriksson, S.; Gosling, J. T.; Lapenta, G.; Newman, D. L.; Goldman, M. V.; Phan, T. D.; Lavraud, B.; Khotyaintsev, Yu. V.; Carr, C. M.; Markidis, S.

    2015-01-01

    We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar wind reconnection exhaust in the presence of a guide field B M   which is almost four times as strong as the reversing field B L . The novel tripolar field consists of two narrow regions of depressed B M , with an observed 7%–14% ΔB M magnitude relative to the external field, which are found adjacent to a wide region of enhanced B M within the exhaust. A stronger reversing field is associated with each B M depression. A kinetic reconnection simulation for realistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentially form across current sheets in the presence of multiple X-lines as magnetic islands approach one another and merge into fewer and larger islands. The simulated ΔB M /ΔX N over the normal width ΔX N between a B M minimum and the edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolar guide field perturbation may be used to identify candidate regions containing multiple X-lines and interacting magnetic islands at individual solar wind current sheets with a strong guide field

  19. ON MULTIPLE RECONNECTION X-LINES AND TRIPOLAR PERTURBATIONS OF STRONG GUIDE MAGNETIC FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, S.; Gosling, J. T. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO (United States); Lapenta, G. [Center for Mathematical Plasma Astrophysics, Department of Mathematics, University of Leuven, Leuven (Belgium); Newman, D. L.; Goldman, M. V. [Center for Integrated Plasma Studies, University of Colorado, Boulder, CO (United States); Phan, T. D. [Space Sciences Laboratory, University of California, Berkeley, CA (United States); Lavraud, B. [Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, Toulouse (France); Khotyaintsev, Yu. V. [Swedish Institute of Space Physics, Uppsala (Sweden); Carr, C. M. [The Blackett Laboratory, Imperial College London, London (United Kingdom); Markidis, S., E-mail: eriksson@lasp.colorado.edu [High Performance Computing and Visualization Department, KTH, Stockholm (Sweden)

    2015-05-20

    We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar wind reconnection exhaust in the presence of a guide field B{sub M} {sub  }which is almost four times as strong as the reversing field B{sub L}. The novel tripolar field consists of two narrow regions of depressed B{sub M}, with an observed 7%–14% ΔB{sub M} magnitude relative to the external field, which are found adjacent to a wide region of enhanced B{sub M} within the exhaust. A stronger reversing field is associated with each B{sub M} depression. A kinetic reconnection simulation for realistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentially form across current sheets in the presence of multiple X-lines as magnetic islands approach one another and merge into fewer and larger islands. The simulated ΔB{sub M}/ΔX{sub N} over the normal width ΔX{sub N} between a B{sub M} minimum and the edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolar guide field perturbation may be used to identify candidate regions containing multiple X-lines and interacting magnetic islands at individual solar wind current sheets with a strong guide field.

  20. Three-dimensional modeling of electron quasiviscous dissipation in guide-field magnetic reconnection

    International Nuclear Information System (INIS)

    Hesse, Michael; Kuznetsova, Masha; Schindler, Karl; Birn, Joachim

    2005-01-01

    A numerical study of guide-field magnetic reconnection in a three-dimensional model is presented. Starting from an initial, perturbed, force-free current sheet, it is shown that reconnection develops to an almost translationally invariant state, where magnetic perturbations are aligned primarily along the main current flow direction. An analysis of guide-field and electron flow signatures indicates behavior that is very similar to earlier, albeit not three-dimensional, simulations. Furthermore, a detailed investigation of electron pressure nongyrotropies in the central diffusion region confirms the major role the associated dissipation process plays in establishing the reconnection electric field

  1. Improvement of spin-exchange optical pumping of xenon-129 using in situ NMR measurement in ultra-low magnetic field

    Science.gov (United States)

    Takeda, Shun; Kumagai, Hiroshi

    2018-02-01

    Hyperpolarized (HP) noble gas has attracted attention in NMR / MRI. In an ultra-low magnetic field, the effectiveness of signal enhancement by HP noble gas should be required because reduction of the signal intensity is serious. One method of generating HP noble gas is spin exchange optical pumping which uses selective excitation of electrons of alkali metal vapor and spin transfer to nuclear spin by collision to noble gas. Although SEOP does not require extreme cooling or strong magnetic field, generally it required large-scale equipment including high power light source to generate HP noble gas with high efficiency. In this study, we construct a simply generation system of HP xenon-129 by SEOP with an ultralow magnetic field (up to 1 mT) and small-scale light source (about 1W). In addition, we measure in situ NMR signal at the same time, and then examine efficient conditions for SEOP in ultra-low magnetic fields.

  2. On the Electron Diffusion Region in Asymmetric Reconnection with a Guide Magnetic Field

    Science.gov (United States)

    Hesse, Michael; Liu, Yi-Hsin; Chen, Li-Jen; Bessho, Naoki; Kuznetsova, Masha; Birn, Joachim; Burch, James L.

    2016-01-01

    Particle-in-cell simulations in a 2.5-D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in-plane flow stagnation and null of the in-plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in-plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.

  3. Magneto-radiotherapy: using magnetic fields to guide dose deposition

    International Nuclear Information System (INIS)

    Nettelbeck, H.; Lerch, M.; Takacs, G.; Rosenfeld, A.

    2006-01-01

    Full text: Magneto-radiotherapy is the application of magnetic fields during radiotherapy procedures. It aims to improve the quality of cancer treatment by using magnetic fields to 1 g uide the dose-deposition of electrons in tissue. Monte Carlo (MC) studies have investigated magneto-radiotherapy applied to conventional photon and electron linac beams. In this study, a combination of MC PENELOPE simulations and physical experiments were done to investigate magneto-radiotherapy applied to MRT (Microbeam Radiation Therapy) and conventional linac radiotherapy.

  4. Annealing of magnetic nanoparticles for their encapsulation into microcarriers guided by vascular magnetic resonance navigation

    Energy Technology Data Exchange (ETDEWEB)

    Pouponneau, Pierre; Segura, Vincent [Ecole Polytechnique de Montreal (EPM), NanoRobotics Laboratory, Department of Computer and Software Engineering and Institute of Biomedical Engineering (Canada); Savadogo, Oumarou [Ecole Polytechnique de Montreal (EPM), Laboratoire de Nouveaux Materiaux pour l' electrochimie et l' energie (Canada); Leroux, Jean-Christophe [Universite de Montreal, Faculty of Pharmacy (Canada); Martel, Sylvain, E-mail: sylvain.martel@polymtl.ca [Ecole Polytechnique de Montreal (EPM), NanoRobotics Laboratory, Department of Computer and Software Engineering and Institute of Biomedical Engineering (Canada)

    2012-12-15

    Iron, cobalt and iron-cobalt nanoparticle properties, such as diameter, saturation magnetization (Ms), crystal structure, surface composition and stability in physiological solutions, were investigated according to the annealing temperature used prior to their encapsulation into poly(d, l-lactic-co-glycolic acid) (PLGA) microcarriers. These new 60-{mu}m microparticles should exhibit an Ms around 70 emu g{sup -1} to be guided in real time from their intravascular injection site to a tumor with a magnetic resonance imaging scanner. The challenge in the preparation of the nanoparticles consisted in limiting Ms loss by oxidation and the release of metallic ions. It was found that when the annealing temperature reached 650 Degree-Sign C, Fe nanoparticles coalesced, the mean diameter reached (O) 361 {+-} 138 nm and Ms increased to 171 emu g{sup -1}. These nanoparticles exhibited a core of {alpha}-Fe and a shell of Fe{sub 3}O{sub 4}. On the opposite, Co nanoparticle properties were not affected by the annealing temperature: O and Ms were around 120 nm and 140 emu g{sup -1}, respectively. FeCo (60:40, atomic percent) nanoparticles coalesced at an annealing temperature >550 Degree-Sign C, O and Ms reached 217 nm and 213 emu g{sup -1}, respectively. Co and FeCo nanoparticles with a Co atomic proportion >15 % were coated with a graphite shell when the temperature was set to 550 Degree-Sign C. In physiological solution, Fe and Co nanoparticles significantly released more ions than FeCo nanoparticles. After the preparation steps prior to their encapsulation, the Ms of Fe and FeCo nanoparticles decreased by 25 and 3 %, respectively. FeCo-PLGA microparticles possessed a relatively high Ms (73 emu g{sup -1}) while that of Fe-PLGA microparticle (20 emu g{sup -1}) was too low for efficient targeting. The graphite shell was efficient to preserve Ms during the encapsulation.

  5. Ultra-high sensitivity moment magnetometry of geological samples using magnetic microscopy

    Science.gov (United States)

    Lima, Eduardo A.; Weiss, Benjamin P.

    2016-09-01

    Useful paleomagnetic information is expected to be recorded by samples with moments up to three orders of magnitude below the detection limit of standard superconducting rock magnetometers. Such samples are now detectable using recently developed magnetic microscopes, which map the magnetic fields above room-temperature samples with unprecedented spatial resolutions and field sensitivities. However, realizing this potential requires the development of techniques for retrieving sample moments from magnetic microscopy data. With this goal, we developed a technique for uniquely obtaining the net magnetic moment of geological samples from magnetic microscopy maps of unresolved or nearly unresolved magnetization. This technique is particularly powerful for analyzing small, weakly magnetized samples such as meteoritic chondrules and terrestrial silicate crystals like zircons. We validated this technique by applying it to field maps generated from synthetic sources and also to field maps measured using a superconducting quantum interference device (SQUID) microscope above geological samples with moments down to 10-15 Am2. For the most magnetic rock samples, the net moments estimated from the SQUID microscope data are within error of independent moment measurements acquired using lower sensitivity standard rock magnetometers. In addition to its superior moment sensitivity, SQUID microscope net moment magnetometry also enables the identification and isolation of magnetic contamination and background sources, which is critical for improving accuracy in paleomagnetic studies of weakly magnetic samples.

  6. Proton and multinuclear magnetic resonance spectroscopy in the human brain at ultra-high field strength: A review.

    Science.gov (United States)

    Henning, Anke

    2018-03-01

    Magnetic Resonance Spectroscopy (MRS) allows for a non-invasive and non-ionizing determination of in vivo tissue concentrations and metabolic turn-over rates of more than 20 metabolites and compounds in the central nervous system of humans. The aim of this review is to give a comprehensive overview about the advantages, challenges and advances of ultra-high field MRS with regard to methodological development, discoveries and applications from its beginnings around 15 years ago up to the current state. The review is limited to human brain and spinal cord application at field strength of 7T and 9.4T and includes all relevant nuclei ( 1 H, 31 P, 13 C). Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Development of a new superfluid helium ultra-cold neutron source and a new magnetic trap for neutron lifetime measurements

    International Nuclear Information System (INIS)

    Leung, Kent Kwan Ho

    2013-01-01

    The development of an Ultra-Cold Neutron (UCN) source at the Institut Laue-Langevin (ILL) based on super-thermal down-scattering of a Cold Neutron (CN) beam in superfluid 4 He is described. A continuous flow, self-liquefying 3 He cryostat was constructed. A beryllium coated prototype converter vessel with a vertical, window-less extraction system was tested on the PF1b CN beam at the ILL. Accumulation measurements with a mechanical valve, and continuous measurements with the vessel left open, were made. The development of a new magnetic UCN trap for neutron lifetime (τ β ) measurements is also described. A 1.2 m long octupole made from permanent magnets, with a bore diameter of 94 mm and surface field of 1.3 T, was assembled. This will be combined with a superconducting coil assembly and used with vertical confinement of UCN by gravity. A discussion of the systematic effects, focussing on the cleaning of above-threshold UCNs, is given. The possibility of detecting the charged decay products is also discussed. UCN storage experiments with the magnetic array and a fomblin-coated piston were performed on PF2 at the ILL. These measurements studied depolarization, spectrum cleaning, and loss due to material reflections in the trap experimentally.

  8. Dynamical cancellation of pulse-induced transients in a metallic shielded room for ultra-low-field magnetic resonance imaging

    International Nuclear Information System (INIS)

    Zevenhoven, Koos C. J.; Ilmoniemi, Risto J.; Dong, Hui; Clarke, John

    2015-01-01

    Pulse-induced transients such as eddy currents can cause problems in measurement techniques where a signal is acquired after an applied preparatory pulse. In ultra-low-field magnetic resonance imaging, performed in magnetic fields typically of the order of 100 μT, the signal-to-noise ratio is enhanced in part by prepolarizing the proton spins with a pulse of much larger magnetic field and in part by detecting the signal with a Superconducting QUantum Interference Device (SQUID). The pulse turn-off, however, can induce large eddy currents in the shielded room, producing an inhomogeneous magnetic-field transient that both seriously distorts the spin dynamics and exceeds the range of the SQUID readout. It is essential to reduce this transient substantially before image acquisition. We introduce dynamical cancellation (DynaCan), a technique in which a precisely designed current waveform is applied to a separate coil during the later part and turn off of the polarizing pulse. This waveform, which bears no resemblance to the polarizing pulse, is designed to drive the eddy currents to zero at the precise moment that the polarizing field becomes zero. We present the theory used to optimize the waveform using a detailed computational model with corrections from measured magnetic-field transients. SQUID-based measurements with DynaCan demonstrate a cancellation of 99%. Dynamical cancellation has the great advantage that, for a given system, the cancellation accuracy can be optimized in software. This technique can be applied to both metal and high-permeability alloy shielded rooms, and even to transients other than eddy currents

  9. Techniques for Ultra-high Magnetic Field Gradient NMR Diffusion Measurements

    Science.gov (United States)

    Sigmund, Eric E.; Mitrovic, Vesna F.; Calder, Edward S.; Will Thomas, G.; Halperin, William P.; Reyes, Arneil P.; Kuhns, Philip L.; Moulton, William G.

    2001-03-01

    We report on development and application of techniques for ultraslow diffusion coefficient measurements through nuclear magnetic resonance (NMR) in high magnetic field gradients. We have performed NMR experiments in a steady fringe field gradient of 175 T/m from a 23 T resistive Bitter magnet, as well as in a gradient of 42 T/m from an 8 T superconducting magnet. New techniques to provide optimum sensitivity in these experiments are described. To eliminate parasitic effects of the temporal instability of the resistive magnet, we have introduced a passive filter: a highly conductive cryogen-cooled inductive shield. We show experimental demonstration of such a shield’s effect on NMR performed in the Bitter magnet. For enhanced efficiency, we have employed “frequency jumping” in our spectrometer system. Application of these methods has made possible measurements of diffusion coefficients as low as 10-10 cm^2/s, probing motion on a 250 nm length scale.

  10. Ultra high field magnetic resonance imaging; L'imagerie par resonance magnetique a ultra-haut champ. L'aimant, piece maitresse de l'imageur. Memo C: les principales techniques d'imagerie medicale

    Energy Technology Data Exchange (ETDEWEB)

    Lethimonnier, F. [CEA Saclay, Institut d' Imagerie Biomedicale - NeuroSpin, Dir. des Sciences du Vivant, 91 - Gif-sur-Yvette (France); Vedrine, P. [CEA Saclay, Direction des Sciences de la Matiere, 91 - Gif-sur-Yvette (France)

    2008-07-01

    Understanding human brain function, brain development and brain dysfunction is one of the great challenges of the twenty first century. Biomedical imaging has now run up against a number of technical constraints that are exposing limits to its potential. In order to overcome the current limits to high-field magnetic resonance cerebral imaging (MRI) and unleash its fullest potential, the Cea has built NeuroSpin, an ultra-high-field neuroimaging facility at its Saclay centre (in the Essonne). NeuroSpin already boasts three fully operational MRI systems. The first is a 3-tesla high-field system and the second is a very-high-field 7-tesla system, both of which are dedicated to clinical studies and investigations in humans, while the third is an ultra-high-field 17.65-tesla system designed for studies on small animals. In 2011, NeuroSpin will be commissioning an 11.7-tesla ultra-high-field system of unprecedented power that is designed for research on human subjects. The level of the magnetic field and the scale required will make this joint French-German project to build the magnet a breakthrough in the international arena. (authors)

  11. Workshop Physics Activity Guide, Module 4: Electricity and Magnetism

    Science.gov (United States)

    Laws, Priscilla W.

    2004-05-01

    The Workshop Physics Activity Guide is a set of student workbooks designed to serve as the foundation for a two-semester calculus-based introductory physics course. It consists of 28 units that interweave text materials with activities that include prediction, qualitative observation, explanation, equation derivation, mathematical modeling, quantitative experiments, and problem solving. Students use a powerful set of computer tools to record, display, and analyze data, as well as to develop mathematical models of physical phenomena. The design of many of the activities is based on the outcomes of physics education research. The Workshop Physics Activity Guide is supported by an Instructor's Website that: (1) describes the history and philosophy of the Workshop Physics Project; (2) provides advice on how to integrate the Guide into a variety of educational settings; (3) provides information on computer tools (hardware and software) and apparatus; and (4) includes suggested homework assignments for each unit. Log on to the Workshop Physics Project website at http://physics.dickinson.edu/ Workshop Physics is a component of the Physics Suite--a collection of materials created by a group of educational reformers known as the Activity Based Physics Group. The Physics Suite contains a broad array of curricular materials that are based on physics education research, including: Understanding Physics, by Cummings, Laws, Redish and Cooney (an introductory textbook based on the best-selling text by Halliday/Resnick/Walker) RealTime Physics Laboratory Modules Physics by Inquiry (intended for use in a workshop setting) Interactive Lecture Demonstration Tutorials in Introductory Physics Activity Based Tutorials (designed primarily for use in recitations)

  12. Efficient Injection of Electron Beams into Magnetic Guide Fields

    International Nuclear Information System (INIS)

    Chorny, V.; Cooperstein, G.; Dubyna, V.; Frolov, O.; Harper-Slaboszewicz, V.; Hinshelwood, D.; Schneider, R.; Solovyov, V.; Tsepilov, H.; Vitkovitsky, I.; Ware, K.

    1999-01-01

    Preliminary experimental and modeling study of injection and transport of high current electron beams in current-neutralized background gas has been performed. Initial analysis of the results indicates that high current triaxial ring diode operates very reproducibly in the pinch mode. High current density beam can be injected efficiently into the drift region, using azimuthal guide field with reduced intensity near the injection region. This was shown to improve the effectiveness of capturing the beam for the transport. The transport length was insufficient to measure losses, such as would arise from scattering with the background gas

  13. A canonical perturbation method for computing the guiding-center motion in magnetized axisymmetric plasma columns

    International Nuclear Information System (INIS)

    Gratreau, P.

    1987-01-01

    The motion of charged particles in a magnetized plasma column, such as that of a magnetic mirror trap or a tokamak, is determined in the framework of the canonical perturbation theory through a method of variation of constants which preserves the energy conservation and the symmetry invariance. The choice of a frame of coordinates close to that of the magnetic coordinates allows a relatively precise determination of the guiding-center motion with a low-ordered approximation in the adiabatic parameter. A Hamiltonian formulation of the motion equations is obtained

  14. Effects of Cold Rolling Reduction and Initial Goss Grains Orientation on Texture Evolution and Magnetic Performance of Ultra-thin Grain-oriented Silicon Steel

    Directory of Open Access Journals (Sweden)

    LIANG Rui-yang

    2017-06-01

    Full Text Available The ultra-thin grain-oriented silicon steel strips with a thickness of 0.06-0.12mm were produced by one-step-rolling methods with different Goss-orientation of grain-oriented silicon steel sheets. The effect of cold rolling reduction and initial Goss-orientation of samples on texture evolution and magnetic performance of ultra-thin grain-oriented silicon steel strips was studied by EBSD. The result shows that with the increase of cold rolling reduction and decrease of strips thickness, the recrystallization texture is enhanced after annealing.When the cold rolling reduction is 70%,RD//〈001〉 recrystallization texture is the sharpest, and the magnetic performance is the best. The higher degree of Goss orientation in initial sample is, the better magnetic performance of ultra-thin grain-oriented silicon steel.Therefore, for producing an ultra-thin grain-oriented silicon steel with high performance, a material with a concentrated orientation of Goss grains can be used.

  15. Microfluidic active mixers employing ultra-high aspect-ratio rare-earth magnetic nano-composite polymer artificial cilia

    International Nuclear Information System (INIS)

    Rahbar, Mona; Gray, Bonnie L; Shannon, Lesley

    2014-01-01

    We present a new micromixer based on highly magnetic, flexible, high aspect-ratio, artificial cilia that are fabricated as individual micromixer elements or in arrays for improved mixing performance. These new cilia enable high efficiency, fast mixing in a microchamber, and are controlled by small electromagnetic fields. The artificial cilia are fabricated using a new micromolding process for nano-composite polymers. Cilia fibers with aspect-ratios as high as 8:0.13 demonstrate the fabrication technique's capability in creating ultra-high aspect-ratio microstructures. Cilia, which are realized in polydimethylsiloxane doped with rare-earth magnetic powder, are magnetized to produce permanent magnetic structures with bidirectional deflection capabilities, making them highly suitable as mixers controlled by electromagnetic fields. Due to the high magnetization level of the polarized nano-composite polymer, we are able to use miniature electromagnets providing relatively small magnetic fields of 1.1 to 7 mT to actuate the cilia microstructures over a very wide motion range. Mixing performances of a single cilium, as well as different arrays of multiple cilia ranging from 2 to 8 per reaction chamber, are characterized and compared with passive diffusion mixing performance. The mixer cilia are actuated at different amplitudes and frequencies to optimize mixing performance. We demonstrate that more than 85% of the total volume of the reaction chamber is fully mixed after 3.5 min using a single cilium mixer at 7 mT compared with only 20% of the total volume mixed with passive diffusion. The time to achieve over 85% mixing is further reduced to 70 s using an array of eight cilia microstructures. The novel microfabrication technique and use of rare-earth permanently-magnetizable nano-composite polymers in mixer applications has not been reported elsewhere by other researchers. We further demonstrate improved mixing over other cilia micromixers as enabled by the high

  16. Experimental verification of the role of electron pressure in fast magnetic reconnection with a guide field

    International Nuclear Information System (INIS)

    Fox, W.; Sciortino, F.; Stechow, A. von; Jara-Almonte, J.

    2017-01-01

    We report detailed laboratory observations of the structure of a reconnection current sheet in a two-fluid plasma regime with a guide magnetic field. We observe and quantitatively analyze the quadrupolar electron pressure variation in the ion-diffusion region, as originally predicted by extended magnetohydrodynamics simulations. The projection of the electron pressure gradient parallel to the magnetic field contributes significantly to balancing the parallel electric field, and the resulting cross-field electron jets in the reconnection layer are diamagnetic in origin. Furthermore, these results demonstrate how parallel and perpendicular force balance are coupled in guide field reconnection and confirm basic theoretical models of the importance of electron pressure gradients for obtaining fast magnetic reconnection.

  17. Guiding center theory for ion holes in magnetized plasmas

    International Nuclear Information System (INIS)

    Jovanovic, D.; Shukla, P.K.

    2003-01-01

    A drift-kinetic theory for ion phase-space vortices in magnetized plasmas is developed, taking into account the effects of the ion polarization and anisotropic heating by ion beams. It provides a theoretical explanation for the bipolar electrostatic structures in the auroral zone of the Earth's magnetosphere and their spatial and temporal scales, as observed by S3-3, Viking, FREJA, Polar, and FAST spacecrafts. Several types of quasi-three-dimensional ion holes are obtained analytically, in the form of either cylinders or ellipsoids. Although topologically different, they produce similar signals on the spacecraft and cannot be distinguished on the basis of the existing satellite data

  18. Development of ultra-short high voltage pulse technology using magnetic pulse compression

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Byung Heon; Kim, S. G.; Nam, S. M.; Lee, B. C.; Lee, S. M.; Jeong, Y. U.; Cho, S. O.; Jin, J. T.; Choi, H. L

    1998-01-01

    The control circuit for high voltage switches, the saturable inductor for magnetic assist, and the magnetic pulse compression circuit were designed, constructed, and tested. The core materials of saturable inductors in magnetic pulse compression circuit were amorphous metal and ferrite and total compression stages were 3. By the test, in high repetition rate, high pulse compression were certified. As a result of this test, it became possible to increase life-time of thyratrons and to replace thyratrons by solid-state semiconductor switches. (author). 16 refs., 16 tabs.

  19. Development of ultra-short high voltage pulse technology using magnetic pulse compression

    International Nuclear Information System (INIS)

    Cha, Byung Heon; Kim, S. G.; Nam, S. M.; Lee, B. C.; Lee, S. M.; Jeong, Y. U.; Cho, S. O.; Jin, J. T.; Choi, H. L.

    1998-01-01

    The control circuit for high voltage switches, the saturable inductor for magnetic assist, and the magnetic pulse compression circuit were designed, constructed, and tested. The core materials of saturable inductors in magnetic pulse compression circuit were amorphous metal and ferrite and total compression stages were 3. By the test, in high repetition rate, high pulse compression were certified. As a result of this test, it became possible to increase life-time of thyratrons and to replace thyratrons by solid-state semiconductor switches. (author). 16 refs., 16 tabs

  20. Ultrasound/Magnetic Resonance Image Fusion Guided Lumbosacral Plexus Block – A Clinical Study

    DEFF Research Database (Denmark)

    Strid, JM; Pedersen, Erik Morre; Søballe, Kjeld

    2014-01-01

    in a double-blinded randomized controlled trial with crossover design. MR datasets will be acquired and uploaded in an advanced US system (Epiq7, Phillips, Amsterdam, Netherlands). All volunteers will receive SSPS blocks with lidocaine added gadolinium contrast guided by US/MR image fusion and by US one week......Background and aims Ultrasound (US) guided lumbosacral plexus block (Supra Sacral Parallel Shift [SSPS]) offers an alternative to general anaesthesia and perioperative analgesia for hip surgery.1 The complex anatomy of the lumbosacral region hampers the accuracy of the block, but it may be improved...... by guidance of US and magnetic resonance (MR) image fusion and real-time 3D electronic needle tip tracking.2 We aim to estimate the effect and the distribution of lidocaine after SSPS guided by US/MR image fusion compared to SSPS guided by ultrasound. Methods Twenty-four healthy volunteers will be included...

  1. Oxygen-enabled control of Dzyaloshinskii-Moriya Interaction in ultra-thin magnetic films

    KAUST Repository

    Belabbes, Abderrezak; Bihlmayer, Gustav; Blü gel, Stefan; Manchon, Aurelien

    2016-01-01

    ferromagnets, resulting in spin spirals and nanoskyrmion lattices. Here, using relativistic first-principles calculations, we demonstrate that the magnitude and sign of DMI can be entirely controlled by tuning the oxygen coverage of the magnetic film, therefore

  2. Magnetic field induced superconductor-insulator transitions for ultra-thin Bi films on the different underlayers

    International Nuclear Information System (INIS)

    Makise, K; Kawaguti, T; Shinozaki, B

    2009-01-01

    This work shows the experimental results of the superconductor-insulator (S-I) transition for ultra-thin Bi films in magnetic fields. The quench-condensed (q-c) Bi film onto insulating underlayers have been interpreted to be homogeneous. In contrast, the Bi film without underlayers has been regarded as a granular film. The electrical transport properties of ultra-thin metal films near the S-I transition depend on the structure of the film. In order to confirm the effect of the underlayer to the homogeneity of the superconducting films, we investigate the characteristics of S-I transitions of q-c nominally homogeneous Bi films on underlayers of two insulating materials, SiO, and Sb. Under almost the same deposition condition except for the material of underlayer, we prepared the Bi films by repeating the additional deposition and performed in-situ electrical measurement. It is found that the transport properties near the S-I transitions show the remarkable difference between two films on different underlayers. As for Bi films on SiO, it turned out that the temperature dependence of resistance per square R sq (T) of the field-tuned transition and the thickness-tuned transition shows similar behavior; it was a thermally activated form. On the other hand, the R sq (T) of Bi films on Sb for thickness-tuned S-I transition showed logarithmic temperature dependence, but that for field-tuned S-I transition showed a thermally activated form.

  3. Investigation of the free electron laser with a guide magnetic field

    International Nuclear Information System (INIS)

    Kwan, T.; Dawson, J.M.

    1979-01-01

    The free electron laser with a static guide magnetic field has been investigated theoretically and by computer simulation using a fully relativistic electromagnetic particle code which has one spatial and three velocity dimensions. By passing a relativistic electron beam through a helical magnetic field, high frequency electromagnetic radiation is generated by its coupling to the negative energy electrostatic beam modes through the helical magnetic field. In the regime of strong guide field where Ω/sub c/e/γ>>k 0 v/sub 0z/, the dispersion relation is obtained by using a fluid model for the electron beam and the growth rates are solved for numerically. Reasonable agreement between the theory and the simulations has been obtained. It was found that the growth rate increases linearly with magnetic ripple strength but decreases with the strength of the guide field. In addition, the growth rates also increase slightly with the beam energy. For a reasonably strong guide field (e.g., Ω/sub c/e=6.0ω/sub p/e), the growth rate can be on the order of 0.1ω/sub p/e and the efficiency of radiation production has been found to be as high as 16%. However, the efficiency decreases with the strength of the guide field. A theory for the saturation level is developed which relates the efficiency to the continued growth of the electromagnetic wave after the onset of trapping by the electrostatic field. It is found that the growth continues for about one bounce time and the observed saturation levels are reasonably well explained

  4. Ultra-long magnetization needle induced by focusing azimuthally polarized beams with a spherical mirror.

    Science.gov (United States)

    Hang, Li; Luo, Kai; Fu, Jian; Chang, Yizhe; Wang, Ying; Chen, Peifeng

    2018-03-20

    Based on extended Richards-Wolf theory for axisymmetric surfaces and the inverse Faraday effect, we propose the generation of a purely longitudinal magnetization needle by focusing Gaussian annular azimuthally polarized beams with a spherical mirror. The needle obtained has a longitudinal length varying hundreds to thousands of wavelengths while keeping the lateral size under 0.4λ, and the corresponding aspect ratio can easily reach more than 2000. It may be the first time that a magnetization needle whose aspect ratio is over 500 has been achieved. The approximate analytical expressions of the magnetization needle are given, and the longitudinal length is tunable by changing the value of the angular thickness and the position of the annular beams.

  5. Magnetized target fusion: An ultra high energy approach in an unexplored parameter space

    International Nuclear Information System (INIS)

    Lindemuth, I.R.

    1994-01-01

    Magnetized target fusion is a concept that may lead to practical fusion applications in a variety of settings. However, the crucial first step is to demonstrate that it works as advertised. Among the possibilities for doing this is an ultrahigh energy approach to magnetized target fusion, one powered by explosive pulsed power generators that have become available for application to thermonuclear fusion research. In a collaborative effort between Los Alamos and the All-Russian Scientific Institute for Experimental Physics (VNIIEF) a very powerful helical generator with explosive power switching has been used to produce an energetic magnetized plasma. Several diagnostics have been fielded to ascertain the properties of this plasma. We are intensively studying the results of the experiments and calculationally analyzing the performance of this experiment

  6. Development of Variational Guiding Center Algorithms for Parallel Calculations in Experimental Magnetic Equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, C. Leland [PPPL; Finn, J. M. [LANL; Qin, H. [PPPL; Tang, William M. [PPPL

    2014-10-01

    Structure-preserving algorithms obtained via discrete variational principles exhibit strong promise for the calculation of guiding center test particle trajectories. The non-canonical Hamiltonian structure of the guiding center equations forms a novel and challenging context for geometric integration. To demonstrate the practical relevance of these methods, a prototypical variational midpoint algorithm is applied to an experimental magnetic equilibrium. The stability characteristics, conservation properties, and implementation requirements associated with the variational algorithms are addressed. Furthermore, computational run time is reduced for large numbers of particles by parallelizing the calculation on GPU hardware.

  7. Magnetic electrospun short nanofibers wrapped graphene oxide as a promising biomaterials for guiding cellular behavior.

    Science.gov (United States)

    Feng, Zhang-Qi; Shi, Chuanmei; Zhao, Bin; Wang, Ting

    2017-12-01

    Magnetic particles show extremely wide application prospects in the biomedical field, particularly in the success of cellular manipulation, drug delivery systems, magnetic hyperthermia and NRI contrast enhancement. Graphene oxide with functional groups has a promising biological effect. In this work, we develop magnetic short-fibers wrapped graphene oxide for guiding cellular behavior with the aid of high-speed shear of nanofibers fabricated through electrospinning technique. The diameter and the length of short-fibers are about 300nm and 80μm, respectively. The short-fibers exhibit superior magnetic properties (saturation magnetization value: 50.33emu/g), which has a strong response appearance to the NdFeB magnet. SEM images and laser confocal images display that there has an extremely tight adhesion between the short-fibers wrapped graphene oxide and cells. The control of cell-fibers structure behavior can be realized by applying external magnet. The results may provide an attractive perspective on the treatment of disease with magnetic field. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Real time magnetic resonance guided endomyocardial local delivery

    Science.gov (United States)

    Corti, R; Badimon, J; Mizsei, G; Macaluso, F; Lee, M; Licato, P; Viles-Gonzalez, J F; Fuster, V; Sherman, W

    2005-01-01

    Objective: To investigate the feasibility of targeting various areas of left ventricle myocardium under real time magnetic resonance (MR) imaging with a customised injection catheter equipped with a miniaturised coil. Design: A needle injection catheter with a mounted resonant solenoid circuit (coil) at its tip was designed and constructed. A 1.5 T MR scanner with customised real time sequence combined with in-room scan running capabilities was used. With this system, various myocardial areas within the left ventricle were targeted and injected with a gadolinium-diethylenetriaminepentaacetic acid (DTPA) and Indian ink mixture. Results: Real time sequencing at 10 frames/s allowed clear visualisation of the moving catheter and its transit through the aorta into the ventricle, as well as targeting of all ventricle wall segments without further image enhancement techniques. All injections were visualised by real time MR imaging and verified by gross pathology. Conclusion: The tracking device allowed real time in vivo visualisation of catheters in the aorta and left ventricle as well as precise targeting of myocardial areas. The use of this real time catheter tracking may enable precise and adequate delivery of agents for tissue regeneration. PMID:15710717

  9. Magnetically engineered smart thin films: toward lab-on-chip ultra-sensitive molecular imaging.

    Science.gov (United States)

    Hassan, Muhammad A; Saqib, Mudassara; Shaikh, Haseeb; Ahmad, Nasir M; Elaissari, Abdelhamid

    2013-03-01

    Magnetically responsive engineered smart thin films of nanoferrites as contrast agent are employed to develop surface based magnetic resonance imaging to acquire simple yet fast molecular imaging. The work presented here can be of significant potential for future lab-on-chip point-of-care diagnostics from the whole blood pool on almost any substrates to reduce or even prevent clinical studies involve a living organism to enhance the non-invasive imaging to advance the '3Rs' of work in animals-replacement, refinement and reduction.

  10. On the GHz frequency response in nanocrystalline FeXN ultra-soft magnetic films

    NARCIS (Netherlands)

    Chechenin, NG; Craus, CB; Chezan, AR; Vystavel, T; Boerma, DO; De Hosson, JTM; Niesen, L; Tidrow, SC; Horwitz, JS; Xi, XX; Levy, J

    2002-01-01

    The periodicity and angular spread of the in-plane magnetization for ultrasoft nanocrystalline FeZrN films were estimated from an analysis of the ripple structure, observed in Lorentz transmission electron microscopy (LTEM) images. The influence of the micromagnetic ripple on the ferromagnetic

  11. Use of an ultra-high resolution magnetic spectrograph for materials research

    NARCIS (Netherlands)

    Boerma, DO; Arnoldbik, WM; Wolfswinkel, W; Balogh, AG; Walter, G

    1997-01-01

    A brief description is given of a magnetic spectrograph for RBS and ERD analysis with MeV beams, delivered by a Tandem accelerator. With a number of examples of thin layer analysis it is shown that the spectrograph is uniquely suited for the measurement of concentration depth profiles up to a depth

  12. Emergence of magnetic order in ultra-thin pyrochlore iridate films

    Science.gov (United States)

    Cheema, Suraj; Serrao, Claudy; Mundy, Julia; Patankar, Shreyas; Birgeneau, Robert; Orenstein, Joseph; Salahuddin, Sayeef; Ramesh, Ramamoorthy

    We report on thickness-dependent magnetotransport in (111) - oriented Pb2Ir2O7-x (Pb227) epitaxial thin films. For thicknesses greater than 4 nm, the magnetoresistance (MR) of metallic Pb227 is positive, linear and non-saturated up to 14 T. Meanwhile at 4 nm, the conduction turns nonmetallic and the MR becomes negative and asymmetric upon field-cooling; such traits are reminiscent of all-in-all-out (AIAO) magnetic order in the insulating pyrochlore iridates. Hysteretic low-field MR dips and trained-untrained resistivity bifurcations suggest the presence of magnetic conducting domain walls within the chiral AIAO spin structure. Beyond just AIAO order, angular-dependent MR indicates a magnetic phase space hosting 2-in-2-out (2I2O) spin ice order. Such anomalous magnetotransport calls for re-evaluation of the pyrochlore iridate phase diagram, as epitaxially strained Pb227 exhibits traits reminiscent of both the insulating magnetic and metallic spin-liquid members. Furthermore, these results open avenues for realizing topological phase predictions in (111) - oriented pyrochlore slabs of kagome-triangular iridate heterostructures. This work is supported by the Office of Basic Energy Sciences of the US Department of Energy under Contract No. DE-AC02-05CH11231.

  13. Electric field with bipolar structure during magnetic reconnection without a guide field

    Science.gov (United States)

    Guo, Jun

    2014-05-01

    We present a study on the polarized electric field during the collisionless magnetic reconnection of antiparallel fields using two dimensional particle-in-cell simulations. The simulations demonstrate clearly that electron holes and electric field with bipolar structure are produced during magnetic reconnection without a guide field. The electric field with bipolar structure can be found near the X-line and on the separatrix and the plasma sheet boundary layer, which is consistent with the observations. These structures will elongate electron's time staying in the diffusion region. In addition, the electric fields with tripolar structures are also found in our simulation.

  14. Optimization of the SNS magnetism reflectometer neutron-guide optics using Monte Carlo simulations

    CERN Document Server

    Klose, F

    2002-01-01

    The magnetism reflectometer at the spallation neutron source SNS will employ advanced neutron optics to achieve high data rate, improved resolution, and extended dynamic range. Optical components utilized will include a multi-channel polygonal curved bender and a tapered neutron-focusing guide section. The results of a neutron beam interacting with these devices are rather complex. Additional complexity arises due to the spectral/time-emission profile of the moderator and non-perfect neutron optical coatings. While analytic formulae for the individual components provide some design guidelines, a realistic performance assessment of the whole instrument can only be achieved by advanced simulation methods. In this contribution, we present guide optics optimizations for the magnetism reflectometer using Monte Carlo simulations. We compare different instrument configurations and calculate the resulting data rates. (orig.)

  15. Ultra-low-frequency electrostatic modes in a magnetized dusty plasma

    International Nuclear Information System (INIS)

    Salimullah, M.; Amin, M.R.; Roy Chowdhury, A.R.; Salahuddin, M.

    1997-11-01

    A study on the extremely low-frequency possible electrostatic modes in a finite temperature magnetized dusty plasma taking the charged dust grains as the third component has been carried out using the appropriate Vlasov-kinetic theory for the dynamics of the electrons, ions and the dust particles. It is found that the inequalities of charge and number density of plasma species, and the finite-Larmor-radius thermal kinetic effects of the mobile charged dust grains, introduce the existence of very low-frequency electrostatic eigenmodes in the three-component homogeneous magnetized dusty plasma. The relevance of the present investigation to space and astrophysical situations as well as laboratory experiments for dust Coulomb crystallization has been pointed out. (author)

  16. A method to detect ultra high energy electrons using earth's magnetic field as a radiator

    Science.gov (United States)

    Stephens, S. A.; Balasubrahmanyan, V. K.

    1983-01-01

    It is pointed out that the detection of electrons with energies exceeding a few TeV, which lose energy rapidly through synchrotron and inverse Compton processes, would provide valuable information on the distribution of sources and on the propagation of cosmic rays in the solar neighborhood. However, it would not be possible to measure the energy spectrum beyond a few TeV with any of the existing experimental techniques. The present investigation is, therefore concerned with the possibility of detecting electrons with energies exceeding a few TeV on the basis of the photons emitted through synchrotron radiation in the earth's magnetic field. Attention is given to the synchrotron radiation of electrons in the earth's magnetic field, detector response and energy estimation, and the characteristics of an ideal detector, capable of detecting photons with energies equal to or greater than 20 keV.

  17. Magnetic resonance imaging guided reirradiation of recurrent and second primary head and neck cancer

    OpenAIRE

    Chen, Allen M.; Cao, Minsong; Hsu, Sophia; Lamb, James; Mikaeilian, Argin; Yang, Yingli; Agazaryan, Nzhde; Low, Daniel A.; Steinberg, Michael L.

    2017-01-01

    Purpose: To report a single-institutional experience using magnetic resonance imaging (MRI) guided radiation therapy for the reirradiation of recurrent and second cancers of the head and neck. Methods and materials: Between October 2014 and August 2016, 13 consecutive patients with recurrent or new primary cancers of the head and neck that occurred in a previously irradiated field were prospectively enrolled in an institutional registry trial to investigate the feasibility and efficacy of ...

  18. Effects of light guide and magnetic field on the characteristics of the short time measuring system

    International Nuclear Information System (INIS)

    Yamada, Yoshihiro; Ohira, Kyozo

    1977-01-01

    In order to construct the nuclear life-time measurement apparatus with good energy and time resolution, consisting of DuMond type beta-ray spectrometer and plastic scintillator, experimental studies are carried out for the effects of light guide and magnetic field on the time resolution, and for the effects of μ-metal shielding on the energy resolution. It has been found that all these effects could be practically diminished. (auth.)

  19. Z a Fast Pulsed Power Generator for Ultra-High Magnetic Field Generation

    Science.gov (United States)

    Spielman, R. B.; Stygar, W. A.; Struve, K. W.; Asay, J. R.; Hall, C. A.; Bernard, M. A.; Bailey, J. E.; McDaniel, D. H.

    2004-11-01

    Advances in fast, pulsed-power technologies have resulted in the development of very high current drivers that have current rise times ~100 ns. The largest such pulsed power driver today is the new Z accelerator located at Sandia National Laboratories in Albuquerque, New Mexico. Z can deliver more than 20 MA with a time-to-peak of 105 ns to low inductance (~1 nH) loads. Such large drivers are capable of directly generating magnetic fields approaching 3 kT in small, 1 cm3 volumes. In addition to direct field generation, Z can be used to compress an applied, axial seed field with a plasma. Flux compression schemes are not new and are, in fact, the basis of all explosive flux-compression generators, but we propose the use of plasma armatures rather than solid, conducting armatures. We present experimental results from the Z accelerator in which magnetic fields of ~2 kT are generated and measured with several diagnostics. Issues such as energy loss in solid conductors and dynamic response of current-carrying conductors to very large magnetic fields are reviewed in context with Z experiments. We describe planned flux-compression experiments that are expected to create the highest-magnitude uniform-field volumes yet attained in the laboratory.

  20. Interaction of ultra soft magnetic materials with the high-T{sub c} superconductor YBCO

    Energy Technology Data Exchange (ETDEWEB)

    Stahl, Claudia; Treiber, Sebastian; Schuetz, Gisela [Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Walker, Patrick [Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart (Germany); Aalen University, Beethovenstrasse 1, 73430 Aalen (Germany); Albrecht, Joachim [Aalen University, Beethovenstrasse 1, 73430 Aalen (Germany)

    2013-07-01

    We have grown bilayers of optimally doped YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) and ferromagnetic CoFeB on single-crystalline substrates by pulsed laser deposition and sputtering. These heterostructures are typically composed of about 100 nm YBCO and several 10 nm of CoFeB. Regarding the superconductor, the properties of the YBCO film change as a consequence of the vicinity of the ferromagnet. In detail we investigated the critical current density as a function of temperature, applied field and time as well as the transition temperature by SQUID magnetization measurements and quantitative magneto-optical measurements. The amorphous material CoFeB exhibits an in plane anisotropy and a very low coercivity. From magneto-optical images we find that the flux line lattice of the superconductor is mapped into the magnet and still visible as significant magnetic out-of-plane contrast at room temperature. We discuss this phenomenon as a new route to high-resolution mapping of the flux line distribution on a nanometer scale.

  1. Magnetic-field-induced dose effects in MR-guided radiotherapy systems: dependence on the magnetic field strength.

    Science.gov (United States)

    Raaijmakers, A J E; Raaymakers, B W; Lagendijk, J J W

    2008-02-21

    Several institutes are currently working on the development of a radiotherapy treatment system with online MR imaging (MRI) modality. The main difference between their designs is the magnetic field strength of the MRI system. While we have chosen a 1.5 Tesla (T) magnetic field strength, the Cross Cancer Institute in Edmonton will be using a 0.2 T MRI scanner and the company Viewray aims to use 0.3 T. The magnetic field strength will affect the severity of magnetic field dose effects, such as the electron return effect (ERE): considerable dose increase at tissue air boundaries due to returning electrons. This paper has investigated how the ERE dose increase depends on the magnetic field strength. Therefore, four situations where the ERE occurs have been simulated: ERE at the distal side of the beam, the lateral ERE, ERE in cylindrical air cavities and ERE in the lungs. The magnetic field comparison values were 0.2, 0.75, 1.5 and 3 T. Results show that, in general, magnetic field dose effects are reduced at lower magnetic field strengths. At the distal side, the ERE dose increase is largest for B = 0.75 T and depends on the irradiation field size for B = 0.2 T. The lateral ERE is strongest for B = 3 T but shows no effect for B = 0.2 T. Around cylindrical air cavities, dose inhomogeneities disappear if the radius of the cavity becomes small relative to the in-air radius of the secondary electron trajectories. At larger cavities (r > 1 cm), dose inhomogeneities exist for all magnetic field strengths. In water-lung-water phantoms, the ERE dose increase takes place at the water-lung transition and the dose decreases at the lung-water transition, but these effects are minimal for B = 0.2 T. These results will contribute to evaluating the trade-off between magnetic field dose effects and image quality of MR-guided radiotherapy systems.

  2. Magnetic-field-induced dose effects in MR-guided radiotherapy systems: dependence on the magnetic field strength

    International Nuclear Information System (INIS)

    Raaijmakers, A J E; Raaymakers, B W; Lagendijk, J J W

    2008-01-01

    Several institutes are currently working on the development of a radiotherapy treatment system with online MR imaging (MRI) modality. The main difference between their designs is the magnetic field strength of the MRI system. While we have chosen a 1.5 Tesla (T) magnetic field strength, the Cross Cancer Institute in Edmonton will be using a 0.2 T MRI scanner and the company Viewray aims to use 0.3 T. The magnetic field strength will affect the severity of magnetic field dose effects, such as the electron return effect (ERE): considerable dose increase at tissue air boundaries due to returning electrons. This paper has investigated how the ERE dose increase depends on the magnetic field strength. Therefore, four situations where the ERE occurs have been simulated: ERE at the distal side of the beam, the lateral ERE, ERE in cylindrical air cavities and ERE in the lungs. The magnetic field comparison values were 0.2, 0.75, 1.5 and 3 T. Results show that, in general, magnetic field dose effects are reduced at lower magnetic field strengths. At the distal side, the ERE dose increase is largest for B = 0.75 T and depends on the irradiation field size for B = 0.2 T. The lateral ERE is strongest for B = 3 T but shows no effect for B = 0.2 T. Around cylindrical air cavities, dose inhomogeneities disappear if the radius of the cavity becomes small relative to the in-air radius of the secondary electron trajectories. At larger cavities (r > 1 cm), dose inhomogeneities exist for all magnetic field strengths. In water-lung-water phantoms, the ERE dose increase takes place at the water-lung transition and the dose decreases at the lung-water transition, but these effects are minimal for B = 0.2 T. These results will contribute to evaluating the trade-off between magnetic field dose effects and image quality of MR-guided radiotherapy systems

  3. Criticality features in ultra-low frequency magnetic fields prior to the 2013 M6.3 Kobe earthquake

    Directory of Open Access Journals (Sweden)

    Stelios M. Potirakis

    2016-07-01

    Full Text Available The nonlinear criticality of ultra-low frequency (ULF magnetic variations is investigated before a particular earthquake (EQ occurred in Kobe on April 12, 2013, by applying the “natural time” analysis on a few ULF parameters: Fh, Fz and Dh. The first two refer to radiation from the lithosphere, and the last parameter corresponds to depression of horizontal component as a signature of ionospheric perturbation. A recent paper of our team has indicated, using the same data as in this paper but by means of conventional statistical analysis, a clear effect of depression in the horizontal component as an ionospheric signature. But there seems to be no convincing signature of lithospheric ULF radiation according to the specific analysis, so this paper aims at extending our study on the electromagnetic data recorded prior to the specific EQ by trying to find any significant phenomenon in ULF effects (both lithospheric radiation and the depression of horizontal component using the critical, natural time analysis. The natural time analysis has yielded that criticality at Shigaraki (SGA, as the station closest to the EQ epicenter, is reached on March 27-29 for Fh and March 27 to April 1 for Fz (about two weeks before the EQ. But, the criticality for Dh was not observed at SGA probably due to high noise, on the other hand such criticality was observed at Kanoya (KNY because of its known property of a wider range of detection of ULF depression.

  4. A 10 mK scanning tunneling microscope operating in ultra high vacuum and high magnetic fields.

    Science.gov (United States)

    Assig, Maximilian; Etzkorn, Markus; Enders, Axel; Stiepany, Wolfgang; Ast, Christian R; Kern, Klaus

    2013-03-01

    We present design and performance of a scanning tunneling microscope (STM) that operates at temperatures down to 10 mK providing ultimate energy resolution on the atomic scale. The STM is attached to a dilution refrigerator with direct access to an ultra high vacuum chamber allowing in situ sample preparation. High magnetic fields of up to 14 T perpendicular and up to 0.5 T parallel to the sample surface can be applied. Temperature sensors mounted directly at the tip and sample position verified the base temperature within a small error margin. Using a superconducting Al tip and a metallic Cu(111) sample, we determined an effective temperature of 38 ± 1 mK from the thermal broadening observed in the tunneling spectra. This results in an upper limit for the energy resolution of ΔE = 3.5 kBT = 11.4 ± 0.3 μeV. The stability between tip and sample is 4 pm at a temperature of 15 mK as demonstrated by topography measurements on a Cu(111) surface.

  5. Brain-heart interactions: challenges and opportunities with functional magnetic resonance imaging at ultra-high field.

    Science.gov (United States)

    Chang, Catie; Raven, Erika P; Duyn, Jeff H

    2016-05-13

    Magnetic resonance imaging (MRI) at ultra-high field (UHF) strengths (7 T and above) offers unique opportunities for studying the human brain with increased spatial resolution, contrast and sensitivity. However, its reliability can be compromised by factors such as head motion, image distortion and non-neural fluctuations of the functional MRI signal. The objective of this review is to provide a critical discussion of the advantages and trade-offs associated with UHF imaging, focusing on the application to studying brain-heart interactions. We describe how UHF MRI may provide contrast and resolution benefits for measuring neural activity of regions involved in the control and mediation of autonomic processes, and in delineating such regions based on anatomical MRI contrast. Limitations arising from confounding signals are discussed, including challenges with distinguishing non-neural physiological effects from the neural signals of interest that reflect cardiorespiratory function. We also consider how recently developed data analysis techniques may be applied to high-field imaging data to uncover novel information about brain-heart interactions. © 2016 The Author(s).

  6. Macrophage Uptake of Ultra-Small Iron Oxide Particles for Magnetic Resonance Imaging in Experimental Acute Cardiac Transplant Rejection

    International Nuclear Information System (INIS)

    Penno, E.; Johnsson, C.; Johansson, L.; Ahlstroem, H.

    2006-01-01

    Purpose: To discriminate between acutely rejecting and non-rejecting transplanted hearts using a blood pool contrast agent and T2 magnetic resonance imaging (MRI) in a clinical 1.5T scanner. Material and Methods: Allogeneic and syngeneic heterotopic heart transplantations were performed in rats. One allogeneic and one syngeneic group each received either the ultra-small iron oxide particle (USPIO), at two different doses, or no contrast agent at all. MRI was performed on postoperative day 6. Immediately after the MR scanning, contrast agent was injected and a further MRI was done 24 h later. Change in T2 was calculated. Results: No significant difference in change in T2 could be seen between rejecting and non-rejecting grafts in either of the doses, or in the control groups. There was a difference between the allogeneic group that received the higher contrast agent dose and the allogeneic group that did not receive any contrast agent at all. Conclusion: In our rat model, measurements of T2 after myocardial macrophage uptake of AMI-227 in a clinical 1.5T scanner were not useful for the diagnosis of acute rejection

  7. Ultra-low power transmitter for encoding non-MR signals in Magnetic Resonance (MR) recordings

    DEFF Research Database (Denmark)

    Petersen, Jan Raagaard; Pedersen, Jan Ole; Zhurbenko, Vitaliy

    collection of data from non-MRI sensors. The transmitter consumes only 1.3mW while transmitting 2.7µW at 120MHz with high frequency stability. The presented design is useful in low power applications requiring high frequency stability and is intended for wireless transmission of non-MR signal recordings......Advancing Magnetic Resonance Imaging (MRI) technology requires integration of the MRI scanners with sensors and systems for monitoring various non-MRI signals. In this paper, we present design and integration of a low power AM radio transmitter into a 3T MRI scanner, which can be used for efficient...

  8. Ultra low frequency magnetic field measurements during earthquake activity in Italy (September-October 1997)

    Energy Technology Data Exchange (ETDEWEB)

    Villante, U.; Vellante, M.; Piancatelli, A. [L' Aquila Univ., L' Aquila (Italy). Dipt. di Fisica e Astrogeofisica

    2001-04-01

    Different methods with different results have been proposed in the scientific literature to identify the possible occurrence of weak seismo-magnetic ULF emissions. In September-October, 1997 Central Italy was struck by repeated seismic activity (M{sub L} < 5.8). A simple amplitude analysis of the geomagnetic field variations (horizontal components, in the frequency range 4-100 mHz) at a geomagnetic facility located = 65-85 km from epicenters of major earthquakes does not reveal in this case any clear evidence for possible ULF emissions.

  9. Magnetization curves of sintered heavy tungsten alloys for applications in MRI-guided radiotherapy

    International Nuclear Information System (INIS)

    Kolling, Stefan; Oborn, Bradley M.; Keall, Paul J.; Horvat, Joseph

    2014-01-01

    Purpose: Due to the current interest in MRI-guided radiotherapy, the magnetic properties of the materials commonly used in radiotherapy are becoming increasingly important. In this paper, measurement results for the magnetization (BH) curves of a range of sintered heavy tungsten alloys used in radiation shielding and collimation are presented. Methods: Sintered heavy tungsten alloys typically contain >90 % tungsten and 0 and the BH curve derived. Results: The iron content of the alloys was found to play a dominant role, directly influencing the magnetizationM and thus the nonlinearity of the BH curve. Generally, the saturation magnetization increased with increasing iron content of the alloy. Furthermore, no measurable magnetization was found for all alloys without iron content, despite containing up to 6% of nickel. For two samples from different manufacturers but with identical quoted nominal elemental composition (95% W, 3.5% Ni, 1.5% Fe), a relative difference in the magnetization of 11%–16% was measured. Conclusions: The measured curves show that the magnetic properties of sintered heavy tungsten alloys strongly depend on the iron content, whereas the addition of nickel in the absence of iron led to no measurable effect. Since a difference in the BH curves for two samples with identical quoted nominal composition from different manufacturers was observed, measuring of the BH curve for each individual batch of heavy tungsten alloys is advisable whenever accurate knowledge of the magnetic properties is crucial. The obtained BH curves can be used in FEM simulations to predict the magnetic impact of sintered heavy tungsten alloys

  10. Magnetic diffusion effects on the ultra-high energy cosmic ray spectrum and composition

    Energy Technology Data Exchange (ETDEWEB)

    Mollerach, Silvia; Roulet, Esteban, E-mail: mollerach@cab.cnea.gov.ar, E-mail: roulet@cab.cnea.gov.ar [CONICET, Centro Atómico Bariloche, Av. Bustillo 9500 (8400) (Argentina)

    2013-10-01

    We discuss the effects of diffusion of high energy cosmic rays in turbulent extra-galactic magnetic fields. We find an approximate expression for the low energy suppression of the spectrum of the different mass components (with charge Z) in the case in which this suppression happens at energies below ∼ Z EeV, so that energy losses are dominated by the adiabatic ones. The low energy suppression appears when cosmic rays from the closest sources take a time comparable to the age of the Universe to reach the Earth. This occurs for energies E < Z EeV (B/nG)√(l{sub c}/Mpc)(d{sub s}/70Mpc) in terms of the magnetic field RMS strength B, its coherence length l{sub c} and the typical separation between sources d{sub s}. We apply this to scenarios in which the sources produce a mixed composition and have a relatively low maximum rigidity (E{sub max} ∼ (2–10)Z EeV), finding that diffusion has a significant effect on the resulting spectrum, the average mass and on its spread, in particular reducing this last one. For reasonable values of B and l{sub c} these effects can help to reproduce the composition trends observed by the Auger Collaboration for source spectra compatible with Fermi acceleration.

  11. Additive manufacturing of magnetic shielding and ultra-high vacuum flange for cold atom sensors.

    Science.gov (United States)

    Vovrosh, Jamie; Voulazeris, Georgios; Petrov, Plamen G; Zou, Ji; Gaber, Youssef; Benn, Laura; Woolger, David; Attallah, Moataz M; Boyer, Vincent; Bongs, Kai; Holynski, Michael

    2018-01-31

    Recent advances in the understanding and control of quantum technologies, such as those based on cold atoms, have resulted in devices with extraordinary metrological performance. To realise this potential outside of a lab environment the size, weight and power consumption need to be reduced. Here we demonstrate the use of laser powder bed fusion, an additive manufacturing technique, as a production technique relevant to the manufacture of quantum sensors. As a demonstration we have constructed two key components using additive manufacturing, namely magnetic shielding and vacuum chambers. The initial prototypes for magnetic shields show shielding factors within a factor of 3 of conventional approaches. The vacuum demonstrator device shows that 3D-printed titanium structures are suitable for use as vacuum chambers, with the test system reaching base pressures of 5 ± 0.5 × 10 -10 mbar. These demonstrations show considerable promise for the use of additive manufacturing for cold atom based quantum technologies, in future enabling improved integrated structures, allowing for the reduction in size, weight and assembly complexity.

  12. Magnetic resonance tomography-guided interventional procedure for diagnosis of prostate cancer

    International Nuclear Information System (INIS)

    Schernthaner, M.; Helbich, T.H.; Fueger, B.J.; Memarsadeghi, M.; Stiglbauer, A.; Linhart, H.G.; Doan, A.; Pinker, K.; Brader, P.; Margreiter, M.

    2011-01-01

    In recent years magnetic resonance imaging (MRI) has been increasingly established in the diagnosis of prostate cancer in addition to transrectal ultrasonography (TRUS). The use of T2-weighted imaging allows an exact delineation of the zonal anatomy of the prostate and its surrounding structures. Other MR imaging tools, such as dynamic contrast-enhanced T1-weighted imaging or diffusion-weighted imaging allow an inference of the biochemical characteristics (multiparametric MRI). Prostate cancer, which could only be diagnosed using MR imaging or lesions suspected as being prostate cancer, which are localized in the anterior aspect of the prostate and were missed with repetitive TRUS biopsy, need to undergo MR guided biopsy. Recent studies have shown a good correlation between MR imaging and histopathology of specimens collected by MR-guided biopsy. Improved lesion targeting is therefore possible with MR-guided biopsy. So far data suggest that MR-guided biopsy of the prostate is a promising alternative diagnostic tool to TRUS-guided biopsy. (orig.) [de

  13. Improving CT-guided transthoracic biopsy of mediastinal lesions by diffusion-weighted magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, Marcos Duarte; TyngI, Chiang Cheng; Bitencourt, Almir Galvao Vieira; Gross, Jefferson Luiz; Zurstrassen, Charles Edouard, E-mail: marcosduarte500@gmail.com [AC Camargo Cancer Center, Sao Paulo, SP (Brazil); Hochhegger, Bruno [Universidade Federal de Ciencias da Saude de Porto Alegre (UFCSPA), RS (Brazil). Dept. de Radiologia; Benveniste, Marcelo Felipe Kuperman; Odisio, Bruno Calazans [University of Texas, MD Anderson Cancer Center, Houston, TX (United States); Marchiori, Edson [Universidade Federal do Rio de Janeiro (UFRJ), Petropolis, RJ (Brazil)

    2014-11-15

    Objectives: to evaluate the preliminary results obtained using diffusion-weighted magnetic resonance imaging and the apparent diffusion coefficient for planning computed tomography-guided biopsies of selected mediastinal lesions. Methods: eight patients with mediastinal lesions suspicious for malignancy were referred for computed tomography-guided biopsy. Diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient measurement were performed to assist in biopsy planning with diffusion/computed tomography fused images. We selected mediastinal lesions that could provide discordant diagnoses depending on the biopsy site, including large heterogeneous masses, lesions associated with lung atelectasis or consolidation, lesions involving large mediastinal vessels and lesions for which the results of biopsy using other methods and histopathological examination were divergent from the clinical and radiological suspicion. Results: in all cases, the biopsy needle was successfully directed to areas of higher signal intensity on diffusion weighted sequences and the lowest apparent diffusion coefficient within the lesion (mean, 0.8 [range, 0.6–1.1]610{sup -3} mm{sup 2}/s), suggesting high cellularity. All biopsies provided adequate material for specific histopathological diagnoses of four lymphomas, two sarcomas and two thymoma s. Conclusion: functional imaging tools, such as diffusion-weighted imaging and the apparent diffusion coefficient, are promising for implementation in noninvasive and imaging-guided procedures. However, additional studies are needed to confirm that mediastinal biopsy can be improved with these techniques. (author)

  14. Degenerate variational integrators for magnetic field line flow and guiding center trajectories

    Science.gov (United States)

    Ellison, C. L.; Finn, J. M.; Burby, J. W.; Kraus, M.; Qin, H.; Tang, W. M.

    2018-05-01

    Symplectic integrators offer many benefits for numerically approximating solutions to Hamiltonian differential equations, including bounded energy error and the preservation of invariant sets. Two important Hamiltonian systems encountered in plasma physics—the flow of magnetic field lines and the guiding center motion of magnetized charged particles—resist symplectic integration by conventional means because the dynamics are most naturally formulated in non-canonical coordinates. New algorithms were recently developed using the variational integration formalism; however, those integrators were found to admit parasitic mode instabilities due to their multistep character. This work eliminates the multistep character, and therefore the parasitic mode instabilities via an adaptation of the variational integration formalism that we deem "degenerate variational integration." Both the magnetic field line and guiding center Lagrangians are degenerate in the sense that the resultant Euler-Lagrange equations are systems of first-order ordinary differential equations. We show that retaining the same degree of degeneracy when constructing discrete Lagrangians yields one-step variational integrators preserving a non-canonical symplectic structure. Numerical examples demonstrate the benefits of the new algorithms, including superior stability relative to the existing variational integrators for these systems and superior qualitative behavior relative to non-conservative algorithms.

  15. Cortico-Striatal GABAergic and Glutamatergic Dysregulations in Subjects at Ultra-High Risk for Psychosis Investigated with Proton Magnetic Resonance Spectroscopy

    Science.gov (United States)

    Reyes-Madrigal, Francisco; Mao, Xiangling; León-Ortiz, Pablo; Rodríguez-Mayoral, Oscar; Solís-Vivanco, Rodolfo; Favila, Rafael; Graff-Guerrero, Ariel; Shungu, Dikoma C.

    2016-01-01

    Background: Dysregulations of the major inhibitory and excitatory amino neurotransmitter systems of γ-aminobutyric acid and glutamate, respectively, have been described in patients with schizophrenia. However, it is unclear whether these abnormalities are present in subjects at ultra-high risk for psychosis. Methods: Twenty-three antipsychotic naïve subjects at ultra-high risk and 24 healthy control subjects, matched for age, sex, handedness, cigarette smoking, and parental education, underwent proton magnetic resonance spectroscopy scans in the dorsal caudate bilaterally and the medial prefrontal cortex at 3T. Levels of γ-aminobutyric acid and of the combined resonance of glutamate and glutamine (Glx) were obtained using the standard J-editing technique and expressed as peak area ratios relative to the synchronously acquired unsuppressed voxel water signal. Results: Higher levels of γ-aminobutyric acid (P<.001) and Glx (P=.007) were found in the dorsal caudate of the subjects at ultra-high risk than in the healthy controls. In the medial prefrontal cortex, likewise, both γ-aminobutyric acid (P=.03) and Glx (P=.006) levels were higher in the ultra-high risk group than in the healthy controls. No group differences were found for any of the other metabolites (N-acetylaspartate, total choline, or total creatine) in the 2 regions of interest. Conclusions: This study presents the first evidence of abnormal elevations, in subjects at ultra-high risk, of γ-aminobutyric acid and Glx in 2 brain regions that have been implicated in the pathophysiology of psychosis, warranting longitudinal studies to assess whether these neurotransmitter abnormalities can serve as noninvasive biomarkers of conversion risk to psychosis as well as of illness progression and treatment response. PMID:26364273

  16. Sub-mm Scale Fiber Guided Deep/Vacuum Ultra-Violet Optical Source for Trapped Mercury Ion Clocks

    Science.gov (United States)

    Yi, Lin; Burt, Eric A.; Huang, Shouhua; Tjoelker, Robert L.

    2013-01-01

    We demonstrate the functionality of a mercury capillary lamp with a diameter in the sub-mm range and deep ultraviolet (DUV)/ vacuum ultraviolet (VUV) radiation delivery via an optical fiber integrated with the capillary. DUV spectrum control is observed by varying the fabrication parameters such as buffer gas type and pressure, capillary diameter, electrical resonator design, and temperature. We also show spectroscopic data of the 199Hg+ hyper-fine transition at 40.5GHz when applying the above fiber optical design. We present efforts toward micro-plasma generation in hollow-core photonic crystal fiber with related optical design and theoretical estimations. This new approach towards a more practical DUV optical interface could benefit trapped ion clock developments for future ultra-stable frequency reference and time-keeping applications.

  17. The ViewRay system: magnetic resonance-guided and controlled radiotherapy.

    Science.gov (United States)

    Mutic, Sasa; Dempsey, James F

    2014-07-01

    A description of the first commercially available magnetic resonance imaging (MRI)-guided radiation therapy (RT) system is provided. The system consists of a split 0.35-T MR scanner straddling 3 (60)Co heads mounted on a ring gantry, each head equipped with independent doubly focused multileaf collimators. The MR and RT systems share a common isocenter, enabling simultaneous and continuous MRI during RT delivery. An on-couch adaptive RT treatment-planning system and integrated MRI-guided RT control system allow for rapid adaptive planning and beam delivery control based on the visualization of soft tissues. Treatment of patients with this system commenced at Washington University in January 2014. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Feasibility of intermittent pneumatic compression for venous thromboembolism prophylaxis during magnetic resonance imaging-guided interventions

    Energy Technology Data Exchange (ETDEWEB)

    Maybody, Majid, E-mail: maybodym@mskcc.org [Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 (United States); Taslakian, Bedros, E-mail: bt05@aub.edu.lb [Department of Diagnostic Radiology, American University of Beirut Medical Center, Riad El-Solh, 1107 2020 Beirut (Lebanon); Durack, Jeremy C., E-mail: durackj@mskcc.org [Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 (United States); Kaye, Elena A., E-mail: kayee@mskcc.org [Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 (United States); Erinjeri, Joseph P., E-mail: erinjerj@mskcc.org [Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 (United States); Srimathveeravalli, Govindarajan, E-mail: srimaths@mskcc.org [Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 (United States); Solomon, Stephen B., E-mail: solomons@mskcc.org [Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065 (United States)

    2015-04-15

    Highlights: •The controller of a standard SCD is labeled as an “MR-unsafe”. •No commercially available “MR-safe” SCDs. •Standard SCDs can be used in iMRI by placing the device outside the MRI scanner room. •Using serial extension tubing did not cause device failure. -- Abstract: Purpose: Venous thromboembolism (VTE) is a common cause of morbidity and mortality in hospitalized and surgical patients. To reduce risk, perioperative VTE prophylaxis is recommended for cancer patients undergoing surgical or interventional procedures. Magnetic resonance imaging (MRI) is increasingly used in interventional oncology when alternative imaging modalities do not adequately delineate malignancies. Extended periods of immobilization during MRI-guided interventions necessitate an MR compatible sequential compression device (SCD) for intra-procedural mechanical VTE prophylaxis. Such devices are not commercially available. Materials and methods: A standard SCD routinely used at our institution for VTE prophylaxis during interventional procedures was used. To satisfy MR safety requirements, the SCD controller was placed in the MR control room and connected to the compression sleeves in the magnet room through the wave guide using tubing extensions. The controller pressure sensor was used to monitor adequate pressure delivery and detect ineffective low or abnormal high pressure delivery. VTE prophylaxis was provided using the above mentioned device for 38 patients undergoing MR-guided ablations. Results: There was no evidence of device failure due to loss of pressure in the extension tubing assembly. No interference with the anesthesia or interventional procedures was documented. Conclusion: Although the controller of a standard SCD is labeled as “MR-unsafe”, the SCD can be used in interventional MR settings by placing the device outside the MR scanner room. Using serial tubing extensions did not cause device failure. The described method can be used to provide

  19. Magnetic Resonance-Guided High-Intensity-Focused Ultrasound for Palliation of Painful Skeletal Metastases: A Pilot Study.

    Science.gov (United States)

    Chan, Michael; Dennis, Kristopher; Huang, Yuexi; Mougenot, Charles; Chow, Edward; DeAngelis, Carlo; Coccagna, Jennifer; Sahgal, Arjun; Hynynen, Kullervo; Czarnota, Gregory; Chu, William

    2017-10-01

    Bone is one of the most common sites of metastases, with bone metastases-related pain representing a significant source of morbidity among patients with cancer. Magnetic resonance-guided focused ultrasound is a noninvasive, outpatient modality with the potential for treating painful bone metastases. The aim of this study is to report our initial experience with magnetic resonance-guided focused ultrasound in the treatment of bone metastases and our preliminary analysis of urinary cytokine levels after therapy. This was a single-center pilot study of 10 patients with metastatic cancer to investigate the feasibility of magnetic resonance-guided focused ultrasound for primary pain control in device-accessible skeletal metastases. Treatments were performed on a clinical magnetic resonance-guided focused ultrasound system using a volumetric ablation technique. Primary efficacy was assessed using Brief Pain Inventory scores and morphine equivalent daily dose intake at 3 time points: before, day 14, and day 30 after the magnetic resonance-guided focused ultrasound treatment. Urine cytokines were measured 3 days before treatment and 2 days after the treatment. Of the 10 patients, 8 were followed up 14 days and 6 were followed up 30 days after the treatment. At day 14, 3 patients (37.5%) exhibited partial pain response and 4 patients (50%) exhibited an indeterminate response, and at day 30 after the treatment, 5 patients (83%) exhibited partial pain response. No treatment-related adverse events were recorded. Of the urine cytokines measured, only Transforming growth factor alpha (TGFα) demonstrated an overall decrease, with a trend toward statistical significance ( P = .078). Our study corroborates magnetic resonance-guided focused ultrasound as a feasible and safe modality as a primary, palliative treatment for painful bone metastases and contributes to the limited body of literature using magnetic resonance-guided focused ultrasound for this clinical indication.

  20. Magnetic resonance guided focalized ultrasound thermo-ablation: A promising oncologic local therapy

    International Nuclear Information System (INIS)

    Iannessi, A.; Doyen, J.; Leysalle, A.; Thyss, A.

    2014-01-01

    Pain management of bone metastases is usually made using systemic and local therapy. Even though radiations are nowadays the gold standard for painful metastases, innovations regarding minimally invasive treatment approaches have been developed because of the existing non-responder patients [1]. Indeed, cementoplasty and thermo-ablations like radiofrequency or cryotherapy have shown to be efficient on pain [2-4]. Among thermo-therapy, magnetic resonance guided focalized ultrasound is now a new non-invasive weapon for bone pain palliation. (authors)

  1. Magnetic resonance imaging guided reirradiation of recurrent and second primary head and neck cancer.

    Science.gov (United States)

    Chen, Allen M; Cao, Minsong; Hsu, Sophia; Lamb, James; Mikaeilian, Argin; Yang, Yingli; Agazaryan, Nzhde; Low, Daniel A; Steinberg, Michael L

    2017-01-01

    To report a single-institutional experience using magnetic resonance imaging (MRI) guided radiation therapy for the reirradiation of recurrent and second cancers of the head and neck. Between October 2014 and August 2016, 13 consecutive patients with recurrent or new primary cancers of the head and neck that occurred in a previously irradiated field were prospectively enrolled in an institutional registry trial to investigate the feasibility and efficacy of MRI guided radiation therapy using a 0.35-T MRI scanner with a cobalt-60 radiation therapy source called the ViewRay system (ViewRay Inc., Cleveland, OH). Eligibility criteria included biopsy-proven evidence of recurrent or new primary squamous cell carcinoma of the head and neck, measurable disease, and previous radiation to >60 Gy. MRI guided reirradiation was delivered either using intensity modulated radiation therapy with conventional fractionation to a median dose of 66 Gy or stereotactic body radiation therapy (SBRT) using 7 to 8 Gy fractions on nonconsecutive days to a median dose of 40 Gy. Two patients (17%) received concurrent chemotherapy. The 1- and 2-year estimates of in-field control were 72% and 72%, respectively. A total of 227 daily MRI scans were obtained to guide reirradiation. The 2-year estimates of overall survival and progression-free survival were 53% and 59%, respectively. There were no treatment-related fatalities or hospitalizations. Complications included skin desquamation, odynophagia, otitis externa, keratitis and/or conjunctivitis, and 1 case of aspiration pneumonia. Our preliminary findings show that reirradiation with MRI guided radiation therapy results in effective disease control with relatively low morbidity for patients with recurrent and second primary cancers of the head and neck. The superior soft tissue resolution of the MRI scans that were used for planning and delivery has the potential to improve the therapeutic ratio.

  2. Survey of risks related to static magnetic fields in ultra high field MRI; Bestandsaufnahme zu Risiken durch statische Magnetfelder im Zusammenhang mit der Ultrahochfeld-MRT

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, H.E. [Max-Planck-Inst. fuer Kognitions- und Neurowissenschaften, Leipzig (Germany); Cramon, D.Y. von [Max-Planck-Inst. fuer Kognitions- und Neurowissenschaften, Leipzig (Germany); Max-Planck-Inst. fuer Neurologische Forschung, Koeln (Germany)

    2008-04-15

    In magnetic resonance imaging (MRI), substantial improvements with respect to sensitivity are expected due to the development of so-called ultra high field scanners, i.e., whole-body scanners with a magnetic field strength of 7 T or above. Users of this technology need to evaluate this benefit for potential risks since commercially available systems are not certified as a medical device for human use. This review provides a detailed survey of static field bioeffects related to the exposure of subjects being scanned, to occupational exposure, and to exposure of the general public under consideration of current standards and directives. According to present knowledge, it is not expected that exposure of human subjects to static magnetic fields of 7 T implies a specific risk of damage or disease provided that known contraindications are observed. The available database does not permit definition of exact thresholds for harmful effects. However, experience from previous application of ultra high field MRI indicates that transient phenomena, such as vertigo, nausea, metallic taste, or magnetophosphenes, are more frequently observed. In particular, movements in the field or the gradient of the fringe field seem to lead to detectable effects. Besides such observations, there is a strong demand for systematic investigation of potential interaction mechanisms related to static field exposure during MRI examinations. (orig.)

  3. Preparation of metastable CoFeNi alloys with ultra-high magnetic saturation (Bs = 2.4-2.59 T) by reverse pulse electrodeposition

    Science.gov (United States)

    Tabakovic, Ibro; Venkatasamy, Venkatram

    2018-04-01

    The results of reverse pulse electrodeposition of CoFeNi films with ultra-high magnetic saturation, i.e. Bs values between 2.4 and 2.59 T, are presented in this work. Based on valence-bond theory (Hund's rule) it was assumed that the electronic configuration of MOH obtained by one electron reduction of electroactive intermediate (MOH+ads + e → MOHads) or oxidation of metal (M - e + HOH → MOH + H+) would result with larger number of spins per atom for each of transition metals in MOH-precipitated in CoFeNi deposit- with one more spin than their respective neutral metal in the order: Fe > Co > Ni. The experimental results showed that the increase of Bs value above Slater-Pauling curve was not observed for CoFe alloys, thus FeOH and CoOH compounds were not present in deposit. However, the increase of the Bs values above the Slater-Pauling curve (Bs = 2.4-2.59 T) was observed, for CoFeNi films obtained by reverse pulse electrodeposition. Therefore, NiOH as a stable compound is probably formed in a one-electron oxidation step during anodic pulse oxidation reaction precipitated presumably at the grain boundaries, giving rise to the ultra-high magnetic saturation of CoFeNi films. The effects of experimental conditions on elemental composition, magnetic properties, crystal structure, and thermal stability of CoFeNi films were studied.

  4. Design of a high efficiency relativistic backward wave oscillator with low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaoze; Song, Wei; Tan, Weibing; Zhang, Ligang; Su, Jiancang; Zhu, Xiaoxin; Hu, Xianggang; Shen, Zhiyuan; Liang, Xu; Ning, Qi [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2016-07-15

    A high efficiency relativistic backward wave oscillator working at a low guiding magnetic field is designed and simulated. A trapezoidal resonant reflector is used to reduce the modulation field in the resonant reflector to avoid overmodulation of the electron beam which will lead to a large momentum spread and then low conversion efficiency. The envelope of the inner radius of the slow wave structure (SWS) increases stepwise to keep conformal to the trajectory of the electron beam which will alleviate the bombardment of the electron on the surface of the SWS. The length of period of the SWS is reduced gradually to make a better match between phase velocity and electron beam, which decelerates continually and improves the RF current distribution. Meanwhile the modulation field is reduced by the introduction of nonuniform SWS also. The particle in cell simulation results reveal that a microwave with a power of 1.8 GW and a frequency of 14.7 GHz is generated with an efficiency of 47% when the diode voltage is 620 kV, the beam current 6.1 kA, and the guiding magnetic field 0.95 T.

  5. Magnetic Nanoparticle Facilitated Drug Delivery for Cancer Therapy with Targeted and Image-Guided Approaches.

    Science.gov (United States)

    Huang, Jing; Li, Yuancheng; Orza, Anamaria; Lu, Qiong; Guo, Peng; Wang, Liya; Yang, Lily; Mao, Hui

    2016-06-14

    With rapid advances in nanomedicine, magnetic nanoparticles (MNPs) have emerged as a promising theranostic tool in biomedical applications, including diagnostic imaging, drug delivery and novel therapeutics. Significant preclinical and clinical research has explored their functionalization, targeted delivery, controllable drug release and image-guided capabilities. To further develop MNPs for theranostic applications and clinical translation in the future, we attempt to provide an overview of the recent advances in the development and application of MNPs for drug delivery, specifically focusing on the topics concerning the importance of biomarker targeting for personalized therapy and the unique magnetic and contrast-enhancing properties of theranostic MNPs that enable image-guided delivery. The common strategies and considerations to produce theranostic MNPs and incorporate payload drugs into MNP carriers are described. The notable examples are presented to demonstrate the advantages of MNPs in specific targeting and delivering under image guidance. Furthermore, current understanding of delivery mechanisms and challenges to achieve efficient therapeutic efficacy or diagnostic capability using MNP-based nanomedicine are discussed.

  6. Sub-solar Magnetopause Observation and Simulation of a Tripolar Guide-Magnetic Field Perturbation

    Science.gov (United States)

    Eriksson, S.; Cassak, P.; Retino, A.; Mozer, F.

    2015-12-01

    The Polar satellite recorded two reconnection exhausts within 6 min on 1 April 2001 at a rather symmetric sub-solar magnetopause that displayed different out-of-plane signatures for similar solar wind conditions. The first case was reported by Mozer et al. [2002] and displayed a bipolar guide field supporting a quadrupole Hall field consistent with a single X-line. The second case, however, shows the first known example of a tripolar guide-field perturbation at Earth's magnetopause reminiscent of the types of solar wind exhausts that Eriksson et al. [2014; 2015] have reported to be in agreement with multiple X-lines. A dedicated particle-in-cell simulation is performed for the prevailing conditions across the magnetopause. We propose an explanation in terms of asymmetric Hall magnetic fields due to a presence of a magnetic island between two X-lines, and discuss how higher resolution MMS observations can be used to further study this problem at the magnetopause.

  7. The role of electron heat flux in guide-field magnetic reconnection

    International Nuclear Information System (INIS)

    Hesse, Michael; Kuznetsova, Masha; Birn, Joachim

    2004-01-01

    A combination of analytical theory and particle-in-cell simulations are employed in order to investigate the electron dynamics near and at the site of guide field magnetic reconnection. A detailed analysis of the contributions to the reconnection electric field shows that both bulk inertia and pressure-based quasiviscous processes are important for the electrons. Analytic scaling demonstrates that conventional approximations for the electron pressure tensor behavior in the dissipation region fail, and that heat flux contributions need to be accounted for. Based on the evolution equation of the heat flux three tensor, which is derived in this paper, an approximate form of the relevant heat flux contributions to the pressure tensor is developed, which reproduces the numerical modeling result reasonably well. Based on this approximation, it is possible to develop a scaling of the electron current layer in the central dissipation region. It is shown that the pressure tensor contributions become important at the scale length defined by the electron Larmor radius in the guide magnetic field

  8. A novel coaxial Ku-band transit radiation oscillator without external guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ling, Junpu, E-mail: lingjunpu@163.com; Zhang, Jiande; He, Juntao; Jiang, Tao [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-02-15

    A novel coaxial transit radiation oscillator without external guiding magnetic field is designed to generate high power microwave at Ku-band. By using a coaxial structure, the space-charge potential energy is suppressed significantly, that is good for enhancing efficient beam-wave interaction. In order to improve the transmission stability of the unmagnetized intense relativistic electron beam, a Pierce-like cathode is employed in the novel device. By contrast with conventional relativistic microwave generators, this kind of device has the advantages of high stability, non-guiding magnetic field, and high efficiency. Moreover, with the coaxial design, it is possible to improve the power-handing capacity by increasing the radial dimension of the Ku-band device. With a 550 keV and 7.5 kA electron beam, a 1.25 GW microwave pulse at 12.08 GHz has been obtained in the simulation. The power conversion efficiency is about 30%.

  9. Ultra-fast speech comprehension in blind subjects engages primary visual cortex, fusiform gyrus, and pulvinar – a functional magnetic resonance imaging (fMRI) study

    Science.gov (United States)

    2013-01-01

    Background Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). To further elucidate the brain mechanisms underlying this extraordinary skill, functional magnetic resonance imaging (fMRI) was performed in blind subjects of varying ultra-fast speech comprehension capabilities and sighted individuals while listening to sentence utterances of a moderately fast (8 syl/s) or ultra-fast (16 syl/s) syllabic rate. Results Besides left inferior frontal gyrus (IFG), bilateral posterior superior temporal sulcus (pSTS) and left supplementary motor area (SMA), blind people highly proficient in ultra-fast speech perception showed significant hemodynamic activation of right-hemispheric primary visual cortex (V1), contralateral fusiform gyrus (FG), and bilateral pulvinar (Pv). Conclusions Presumably, FG supports the left-hemispheric perisylvian “language network”, i.e., IFG and superior temporal lobe, during the (segmental) sequencing of verbal utterances whereas the collaboration of bilateral pulvinar, right auditory cortex, and ipsilateral V1 implements a signal-driven timing mechanism related to syllabic (suprasegmental) modulation of the speech signal. These data structures, conveyed via left SMA to the perisylvian “language zones”, might facilitate – under time-critical conditions – the consolidation of linguistic information at the level of verbal working memory. PMID:23879896

  10. Electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes: FFT-impedance spectroscopy of the growth process and magnetic properties.

    Science.gov (United States)

    Gerngross, Mark-Daniel; Carstensen, Jürgen; Föll, Helmut

    2014-01-01

    The electrochemical growth of Co nanowires in ultra-high aspect ratio InP membranes has been investigated by fast Fourier transform-impedance spectroscopy (FFT-IS) in the frequency range from 75 Hz to 18.5 kHz. The impedance data could be fitted very well using an electric circuit equivalent model with a series resistance connected in series to a simple resistor-capacitor (RC) element and a Maxwell element. Based on the impedance data, the Co deposition in ultra-high aspect ratio InP membranes can be divided into two different Co deposition processes. The corresponding share of each process on the overall Co deposition can be determined directly from the transfer resistances of the two processes. The impedance data clearly show the beneficial impact of boric acid on the Co deposition and also indicate a diffusion limitation of boric acid in ultra-high aspect ratio InP membranes. The grown Co nanowires are polycrystalline with a very small grain size. They show a narrow hysteresis loop with a preferential orientation of the easy magnetization direction along the long nanowire axis due to the arising shape anisotropy of the Co nanowires.

  11. Ultra-large bandwidth hollow-core guiding in all-silica bragg fibers with nano-supports

    DEFF Research Database (Denmark)

    Vienne, Guillaume; Xu, Yong; Jakobsen, Christian

    2004-01-01

    We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in t...... in this new class of Bragg fibers exceeds that of other hollow-core fibers reported in the literature. With only three rings of silica cladding layers, these Bragg fibers achieve propagation loss of the order of 1 dB/m....

  12. Preoperative magnetic resonance imaging protocol for endoscopic cranial base image-guided surgery.

    Science.gov (United States)

    Grindle, Christopher R; Curry, Joseph M; Kang, Melissa D; Evans, James J; Rosen, Marc R

    2011-01-01

    Despite the increasing utilization of image-guided surgery, no radiology protocols for obtaining magnetic resonance (MR) imaging of adequate quality are available in the current literature. At our institution, more than 300 endonasal cranial base procedures including pituitary, extended pituitary, and other anterior skullbase procedures have been performed in the past 3 years. To facilitate and optimize preoperative evaluation and assessment, there was a need to develop a magnetic resonance protocol. Retrospective Technical Assessment was performed. Through a collaborative effort between the otolaryngology, neurosurgery, and neuroradiology departments at our institution, a skull base MR image-guided (IGS) protocol was developed with several ends in mind. First, it was necessary to generate diagnostic images useful for the more frequently seen pathologies to improve work flow and limit the expense and inefficiency of case specific MR studies. Second, it was necessary to generate sequences useful for IGS, preferably using sequences that best highlight that lesion. Currently, at our institution, all MR images used for IGS are obtained using this protocol as part of preoperative planning. The protocol that has been developed allows for thin cut precontrast and postcontrast axial cuts that can be used to plan intraoperative image guidance. It also obtains a thin cut T2 axial series that can be compiled separately for intraoperative imaging, or may be fused with computed tomographic images for combined modality. The outlined protocol obtains image sequences effective for diagnostic and operative purposes for image-guided surgery using both T1 and T2 sequences. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. Asymmetry of the Ion Diffusion Region Hall Electric and Magnetic Fields during Guide Field Reconnection: Observations and Comparison with Simulations

    International Nuclear Information System (INIS)

    Eastwood, J. P.; Shay, M. A.; Phan, T. D.; Oieroset, M.

    2010-01-01

    In situ measurements of magnetic reconnection in the Earth's magnetotail are presented showing that even a moderate guide field (20% of the reconnecting field) considerably distorts ion diffusion region structure. The Hall magnetic and electric fields are asymmetric and shunted away from the current sheet; an appropriately scaled particle-in-cell simulation is found to be in excellent agreement with the data. The results show the importance of correctly accounting for the effects of the magnetic shear when attempting to identify and study magnetic reconnection diffusion regions in nature.

  14. Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

    Science.gov (United States)

    Payne, Allison H; Hawryluk, Gregory W; Anzai, Yoshimi; Odéen, Henrik; Ostlie, Megan A; Reichert, Ethan C; Stump, Amanda J; Minoshima, Satoshi; Cross, Donna J

    2017-12-01

    Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.

  15. Magnetic Resonance Imaging-Guided Osseous Biopsy in Children With Chronic Recurrent Multifocal Osteomyelitis

    International Nuclear Information System (INIS)

    Fritz, Jan; Tzaribachev, Nikolay; Thomas, Christoph; Wehrmann, Manfred; Horger, Marius S.; Carrino, John A.; König, Claudius W.; Pereira, Philippe L.

    2012-01-01

    Purpose: To report the safety and diagnostic performance of magnetic resonance (MRI)—guided core biopsy of osseous lesions in children with chronic recurrent multifocal osteomyelitis (CRMO) that were visible on MRI but were occult on radiography and computed tomography (CT). Materials and Methods: A retrospective analysis of MRI-guided osseous biopsy performed in seven children (four girls and three boys; mean age 13 years (range 11 to 14) with CRMO was performed. Indication for using MRI guidance was visibility of lesions by MRI only. MRI-guided procedures were performed with 0.2-Tesla (Magnetom Concerto; Siemens, Erlangen, Germany; n = 5) or 1.5-T (Magnetom Espree; Siemens; n = 2) open MRI systems. Core needle biopsy was obtained using an MRI-compatible 4-mm drill system. Conscious sedation or general anesthesia was used. Parameters evaluated were lesion visibility, technical success, procedure time, complications and microbiology, cytology, and histopathology findings. Results: Seven of seven (100%) targeted lesions were successfully visualized and sampled. All obtained specimens were sufficient for histopathological analysis. Length of time of the procedures was 77 min (range 64 to 107). No complications occurred. Histopathology showed no evidence of malignancy, which was confirmed at mean follow-up of 50 months (range 28 to 78). Chronic nonspecific inflammation characteristic for CRMO was present in four of seven (58%) patients, and edema with no inflammatory cells was found in three of seven (42%) patients. There was no evidence of infection in any patient. Conclusion: MRI-guided osseous biopsy is a safe and accurate technique for the diagnosis of pediatric CRMO lesions that are visible on MRI only.

  16. Magnetic resonance imaging - guided vacuum-assisted breast biopsy: an initial experience in a community hospital

    International Nuclear Information System (INIS)

    Friedman, P.; Enis, S.; Pinyard, J.

    2009-01-01

    To evaluate the effectiveness in diagnosing mammographically and sonographically occult breast lesions by using magnetic resonance imaging (MRI) guided vacuum-assisted breast biopsy in patients who presented to a community-based hospital with a newly established breast MRI program. The records of 142 consecutive patients, median age of 55 years, who had undergone MRI-guided biopsy at our institution between July 2006 and July 2007 were reviewed. From these patients, 197 mammographically and sonographically occult lesions were biopsied at the time of discovery. The pathology was then reviewed and correlated with the MRI findings. Cancer was present and subsequently discovered in 8% of the previously occult lesions (16/197) or 11% of the women studied (16/142). Of the cancerous lesions, 56% were invasive carcinomas (9/16) and 44% were ductal carcinomas in situ (7/16). Fourteen percent of the discovered lesions (28/197) were defined as high risk and included atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, and radial scar. In total, occult cancerous and high-risk lesions were discovered in 22% of the found lesions (44/197) or 31% of the women who underwent MRI-guided biopsy (44/142). This study demonstrated that detection of cancerous and high-risk lesions can be significantly increased when an MRI-guided biopsy program is introduced at a community-based hospital. We believe that as radiologists gain confidence in imaging and histologic correlation, community-based hospitals can achieve similar rates of occult lesion diagnosis as those found in data emerging from academic institutions. (author)

  17. Magnetic resonance imaging - guided vacuum-assisted breast biopsy: an initial experience in a community hospital

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, P.; Enis, S.; Pinyard, J., E-mail: jpinyard@gmail.com [Morristown Memorial Hospital, The Carol W. and Julius A. Rippel Breast Center, The Carol G. Simon Cancer Centre, Morristown, New Jersey (United States)

    2009-10-15

    To evaluate the effectiveness in diagnosing mammographically and sonographically occult breast lesions by using magnetic resonance imaging (MRI) guided vacuum-assisted breast biopsy in patients who presented to a community-based hospital with a newly established breast MRI program. The records of 142 consecutive patients, median age of 55 years, who had undergone MRI-guided biopsy at our institution between July 2006 and July 2007 were reviewed. From these patients, 197 mammographically and sonographically occult lesions were biopsied at the time of discovery. The pathology was then reviewed and correlated with the MRI findings. Cancer was present and subsequently discovered in 8% of the previously occult lesions (16/197) or 11% of the women studied (16/142). Of the cancerous lesions, 56% were invasive carcinomas (9/16) and 44% were ductal carcinomas in situ (7/16). Fourteen percent of the discovered lesions (28/197) were defined as high risk and included atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, and radial scar. In total, occult cancerous and high-risk lesions were discovered in 22% of the found lesions (44/197) or 31% of the women who underwent MRI-guided biopsy (44/142). This study demonstrated that detection of cancerous and high-risk lesions can be significantly increased when an MRI-guided biopsy program is introduced at a community-based hospital. We believe that as radiologists gain confidence in imaging and histologic correlation, community-based hospitals can achieve similar rates of occult lesion diagnosis as those found in data emerging from academic institutions. (author)

  18. MRI-Guided Percutaneous Biopsy of Mediastinal Masses Using a Large Bore Magnet: Technical Feasibility

    Energy Technology Data Exchange (ETDEWEB)

    Garnon, J., E-mail: juliengarnon@gmail.com [Nouvel Hôpital Civil, Department of Interventional Radiology (France); Ramamurthy, N., E-mail: nitin-ramamurthy@hotmail.com [Norfolk and Norwich University Hospital, Department of Radiology (United Kingdom); Caudrelier J, J., E-mail: caudjean@yahoo.fr [Nouvel Hôpital Civil, Department of Interventional Radiology (France); Erceg, G., E-mail: erceggorislav@yahoo.com; Breton, E., E-mail: ebreton@unistra.fr [ICube, University of Strasbourg, CNRS (France); Tsoumakidou, G., E-mail: gtsoumakidou@yahoo.com; Rao, P., E-mail: pramodrao@me.com; Gangi, A., E-mail: gangi@unistra.fr [Nouvel Hôpital Civil, Department of Interventional Radiology (France)

    2016-05-15

    ObjectiveTo evaluate the diagnostic accuracy and safety of magnetic resonance imaging (MRI)-guided percutaneous biopsy of mediastinal masses performed using a wide-bore high-field scanner.Materials and MethodsThis is a retrospective study of 16 consecutive patients (8 male, 8 female; mean age 74 years) who underwent MRI-guided core needle biopsy of a mediastinal mass between February 2010 and January 2014. Size and location of lesion, approach taken, time for needle placement, overall duration of procedure, and post-procedural complications were evaluated. Technical success rates and correlation with surgical pathology (where available) were assessed.ResultsTarget lesions were located in the anterior (n = 13), middle (n = 2), and posterior mediastinum (n = 1), respectively. Mean size was 7.2 cm (range 3.6–11 cm). Average time for needle placement was 9.4 min (range 3–18 min); average duration of entire procedure was 42 min (range 27–62 min). 2–5 core samples were obtained from each lesion (mean 2.6). Technical success rate was 100 %, with specimens successfully obtained in all 16 patients. There were no immediate complications. Histopathology revealed malignancy in 12 cases (4 of which were surgically confirmed), benign lesions in 3 cases (1 of which was false negative following surgical resection), and one inconclusive specimen (treated as inaccurate since repeat CT-guided biopsy demonstrated thymic hyperplasia). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in our study were 92.3, 100, 100, 66.7, and 87.5 %, respectively.ConclusionMRI-guided mediastinal biopsy is a safe procedure with high diagnostic accuracy, which may offer a non-ionizing alternative to CT guidance.

  19. Determination of type A trichothecenes in coix seed by magnetic solid-phase extraction based on magnetic multi-walled carbon nanotubes coupled with ultra-high performance liquid chromatography-tandem mass spectrometry.

    Science.gov (United States)

    Dong, Maofeng; Si, Wenshuai; Wang, Weimin; Bai, Bing; Nie, Dongxia; Song, Weiguo; Zhao, Zhihui; Guo, Yirong; Han, Zheng

    2016-09-01

    Magnetic solid-phase extraction (m-SPE) is a promising sample preparation approach due to its convenience, speed, and simplicity. For the first time, a rapid and reliable m-SPE approach using magnetic multi-walled carbon nanotubes (m-MWCNTs) as the adsorbent was proposed for purification of type A trichothecenes including T-2 toxins (T2), HT-2 toxins (HT-2), diacetoxyscirpenol (DAS), and neosolaniol (NEO) in coix seed. The m-MWCNTs were synthesized by assembling the magnetic nanoparticles (Fe3O4) with MWCNTs by sonication through an aggregation wrap mechanism, and characterized by transmission electron microscope. Several key parameters affecting the performance of the procedure were extensively investigated including extraction solutions, desorption solvents, and m-MWCNT amounts. Under the optimal sample preparation conditions followed by analysis with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), high sensitivity (limit of quantification in the range of 0.3-1.5 μg kg(-1)), good linearity (R (2) > 0.99), satisfactory recovery (73.6-90.6 %), and acceptable precision (≤2.5 %) were obtained. The analytical performance of the developed method has also been successfully evaluated in real coix seed samples. Graphical Abstract Flow chart of determination of type A trichothecenes in coix seed by magnetic solid-phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry.

  20. Evaluating the role of prefrontal and parietal cortices in memory-guided response with repetitive transcranial magnetic stimulation

    OpenAIRE

    Hamidi, Massihullah; Tononi, Giulio; Postle, Bradley R.

    2008-01-01

    The dorsolateral prefrontal cortex (dlPFC) plays an important role in working memory, including the control of memory-guided response. In this study, with 24 subjects, we used high frequency repetitive transcranial magnetic stimulation (rTMS) to evaluate the role of the dlPFC in memory-guided response to two different types of spatial working memory tasks: one requiring a recognition decision about a probe stimulus (operationalized with a yes/no button press), another requiring direct recall ...

  1. Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence

    Science.gov (United States)

    Montag, Peter; Egedal, Jan; Lichko, Emily; Wetherton, Blake

    2017-10-01

    Previous work has shown that Fermi acceleration can be an effective heating mechanism during magnetic island coalescence, where electrons may undergo repeated reflections as the magnetic field lines contract. This energization has the potential to account for the power-law distributions of particle energy inferred from observations of solar flares. Here, we develop a generalized framework for the analysis of Fermi acceleration that can incorporate the effects of compressibility and non-uniformity along field lines, which have commonly been neglected in previous treatments of the problem. Applying this framework to the simplified case of the uniform flux tube allows us to find both the power-law scaling of the distribution function and the rate at which the power-law behavior develops. We find that a guide magnetic field of order unity effectively suppresses the development of power-law distributions. The work was supported by NASA Grant No. NNX14AC68G, NSF GEM Grant No. 1405166, NSF Award 1404166, and NASA Award NNX15AJ73G.

  2. The Onset of Magnetic Reconnection: Tearing Instability in Current Sheets with a Guide Field

    Science.gov (United States)

    Daldorff, L. K. S.; Klimchuk, J. A.; Knizhnik, K. J.

    2016-12-01

    Magnetic reconnection is fundamental to many solar phenomena, ranging from coronal heating, to jets, to flares and CMEs. A poorly understood yet crucial aspect of reconnection is that it does not occur until magnetic stresses have built to sufficiently high levels for significant energy release. If reconnection were to happen too soon, coronal heating would be weak and flares would be small. As part of our program to study the onset conditions for magnetic reconnection, we have investigated the instability of current sheets to tearing. Surprisingly little work has been done on this problem for sheets that include a guide field, i.e., for which the field rotates by less than 180 degrees. This is the most common situation on the Sun. We present numerical 3D resistive MHD simulations of several sheets and show how the behaviour depends on the shear angle (rotation). We compare our results to the predictions of linear theory and discuss the nonlinear evolution in terms of plasmoid formation and the interaction of different oblique tearing modes. The relevance to the Sun is explained.

  3. Electron spin polarization in realistic trajectories around the magnetic node of two counter-propagating, circularly polarized, ultra-intense lasers

    Science.gov (United States)

    Del Sorbo, D.; Seipt, D.; Thomas, A. G. R.; Ridgers, C. P.

    2018-06-01

    It has recently been suggested that two counter-propagating, circularly polarized, ultra-intense lasers can induce a strong electron spin polarization at the magnetic node of the electromagnetic field that they setup (Del Sorbo et al 2017 Phys. Rev. A 96 043407). We confirm these results by considering a more sophisticated description that integrates over realistic trajectories. The electron dynamics is weakly affected by the variation of power radiated due to the spin polarization. The degree of spin polarization differs by approximately 5% if considering electrons initially at rest or already in a circular orbit. The instability of trajectories at the magnetic node induces a spin precession associated with the electron migration that establishes an upper temporal limit to the polarization of the electron population of about one laser period.

  4. An ultra­high field Magnetic Resonance Spectroscopy study of post exercise brain lactate, glutamate and glutamine change in the human brain.

    Directory of Open Access Journals (Sweden)

    Andrea eDennis

    2015-12-01

    Full Text Available During strenuous exercise there is a progressive increase in lactate uptake and metabolism into the brain as workload and plasma lactate levels increase. Although it is now widely accepted that the brain can metabolise lactate, few studies have directly measured brain lactate following vigorous exercise. Here, we used ultra-high field Magnetic Resonance Spectroscopy of the brain to obtain static measures of brain lactate, as well as brain glutamate and glutamine after vigorous exercise. The aims of our experiment were to (a track the changes in brain lactate following recovery from exercise and, (b to simultaneously measure the signals from brain glutamate and glutamine. The results of our experiment showed that vigorous exercise resulted in a significant increase in brain lactate. Furthermore, both glutamate and glutamine were successfully resolved, and as expected, although contrary to some previous reports, we did not observe any significant change in either amino acid after exercise. We did however observe a negative correlation between glutamate and a measure of fitness. These results support the hypothesis that peripherally-derived lactate is taken up by the brain when available. Our data additionally highlight the potential of ultra-high field magnetic resonance spectroscopy as a non-invasive way of measuring multiple brain metabolite changes with exercise.

  5. An ultra-high vacuum scanning tunneling microscope operating at sub-Kelvin temperatures and high magnetic fields for spin-resolved measurements

    Science.gov (United States)

    Salazar, C.; Baumann, D.; Hänke, T.; Scheffler, M.; Kühne, T.; Kaiser, M.; Voigtländer, R.; Lindackers, D.; Büchner, B.; Hess, C.

    2018-06-01

    We present the construction and performance of an ultra-low-temperature scanning tunneling microscope (STM), working in ultra-high vacuum (UHV) conditions and in high magnetic fields up to 9 T. The cryogenic environment of the STM is generated by a single-shot 3He magnet cryostat in combination with a 4He dewar system. At a base temperature (300 mK), the cryostat has an operation time of approximately 80 h. The special design of the microscope allows the transfer of the STM head from the cryostat to a UHV chamber system, where samples and STM tips can be easily exchanged. The UHV chambers are equipped with specific surface science treatment tools for the functionalization of samples and tips, including high-temperature treatments and thin film deposition. This, in particular, enables spin-resolved tunneling measurements. We present test measurements using well-known samples and tips based on superconductors and metallic materials such as LiFeAs, Nb, Fe, and W. The measurements demonstrate the outstanding performance of the STM with high spatial and energy resolution as well as the spin-resolved capability.

  6. Electron heating in the exhaust of magnetic reconnection with negligible guide field

    Science.gov (United States)

    Wang, Shan; Chen, Li-Jen; Bessho, Naoki; Kistler, Lynn M.; Shuster, Jason R.; Guo, Ruilong

    2016-03-01

    Electron heating in the magnetic reconnection exhaust is investigated with particle-in-cell simulations, space observations, and theoretical analysis. Spatial variations of the electron temperature (Te) and associated velocity distribution functions (VDFs) are examined and understood in terms of particle energization and randomization processes that vary with exhaust locations. Inside the electron diffusion region (EDR), the electron temperature parallel to the magnetic field (Te∥) exhibits a local minimum and the perpendicular temperature (Te⊥) shows a maximum at the current sheet midplane. In the intermediate exhaust downstream from the EDR and far from the magnetic field pileup region, Te⊥/Te∥ is close to unity and Te is approximately uniform, but the VDFs are structured: close to the midplane, VDFs are quasi-isotropic, whereas farther away from the midplane, VDFs exhibit field-aligned beams directed toward the midplane. In the far exhaust, Te generally increases toward the midplane and the pileup region, and the corresponding VDFs show counter-streaming beams. A distinct population with low v∥ and high v⊥ is prominent in the VDFs around the midplane. Test particle results show that the magnetic curvature near the midplane produces pitch angle scattering to generate quasi-isotropic distributions in the intermediate exhaust. In the far exhaust, electrons with initial high v∥ (v⊥) are accelerated mainly through curvature (gradient-B) drift opposite to the electric field, without significant pitch angle scattering. The VDF structures predicted by simulations are observed in magnetotail reconnection measurements, indicating that the energization mechanisms captured in the reported simulations are applicable to magnetotail reconnection with negligible guide field.

  7. Effects of a Guide Field on the Larmor Electric Field and Upstream Electron Temperature Anisotropy in Collisionless Asymmetric Magnetic Reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Ek-In, Surapat; Ruffolo, David [Department of Physics, Faculty of Science, Mahidol University, Bangkok (Thailand); Malakit, Kittipat [Department of Physics, Faculty of Science and Techonology, Thammasat University, Pathum Thani (Thailand); Shay, Michael A. [Department of Physics and Astronomy, University of Delaware, Newark, DE (United States); Cassak, Paul A., E-mail: kmalakit@gmail.com [Department of Physics and Astronomy, West Virginia University, Morgantown, WV (United States)

    2017-08-20

    We perform the first study of the properties of the Larmor electric field (LEF) in collisionless asymmetric magnetic reconnection in the presence of an out-of-plane (guide) magnetic field for different sets of representative upstream parameters at Earth’s dayside magnetopause with an ion temperature greater than the electron temperature (the ion-to-electron temperature ratio fixed at 2) using two-dimensional particle-in-cell simulations. We show that the LEF does persist in the presence of a guide field. We study how the LEF thickness and strength change as a function of guide field and the magnetospheric temperature and reconnecting magnetic field strength. We find that the thickness of the LEF structure decreases, while its magnitude increases when a guide field is added to the reconnecting magnetic field. The added guide field makes the Larmor radius smaller, so the scaling with the magnetospheric ion Larmor radius is similar to that reported for the case without a guide field. Note, however, that the physics causing the LEF is not well understood, so future work in other parameter regimes is needed to fully predict the LEF for arbitrary conditions. We also find that a previously reported upstream electron temperature anisotropy arises in the vicinity of the LEF region both with and without a guide field. We argue that the generation of the anisotropy is linked to the existence of the LEF. The LEF can be used in combination with the electron temperature anisotropy as a signature to effectively identify dayside reconnection sites in observations.

  8. Effects of a Guide Field on the Larmor Electric Field and Upstream Electron Temperature Anisotropy in Collisionless Asymmetric Magnetic Reconnection

    International Nuclear Information System (INIS)

    Ek-In, Surapat; Ruffolo, David; Malakit, Kittipat; Shay, Michael A.; Cassak, Paul A.

    2017-01-01

    We perform the first study of the properties of the Larmor electric field (LEF) in collisionless asymmetric magnetic reconnection in the presence of an out-of-plane (guide) magnetic field for different sets of representative upstream parameters at Earth’s dayside magnetopause with an ion temperature greater than the electron temperature (the ion-to-electron temperature ratio fixed at 2) using two-dimensional particle-in-cell simulations. We show that the LEF does persist in the presence of a guide field. We study how the LEF thickness and strength change as a function of guide field and the magnetospheric temperature and reconnecting magnetic field strength. We find that the thickness of the LEF structure decreases, while its magnitude increases when a guide field is added to the reconnecting magnetic field. The added guide field makes the Larmor radius smaller, so the scaling with the magnetospheric ion Larmor radius is similar to that reported for the case without a guide field. Note, however, that the physics causing the LEF is not well understood, so future work in other parameter regimes is needed to fully predict the LEF for arbitrary conditions. We also find that a previously reported upstream electron temperature anisotropy arises in the vicinity of the LEF region both with and without a guide field. We argue that the generation of the anisotropy is linked to the existence of the LEF. The LEF can be used in combination with the electron temperature anisotropy as a signature to effectively identify dayside reconnection sites in observations.

  9. Magnetic Resonance Imaging-Guided Focused Ultrasound Surgery for the Treatment of Symptomatic Uterine Fibroids

    Directory of Open Access Journals (Sweden)

    Laura Geraci

    2017-01-01

    Full Text Available Uterine fibroids, the most common benign tumor in women of childbearing age, may cause symptoms including pelvic pain, menorrhagia, dysmenorrhea, pressure, urinary symptoms, and infertility. Various approaches are available to treat symptomatic uterine fibroids. Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS represents a recently introduced noninvasive safe and effective technique that can be performed without general anesthesia, in an outpatient setting. We review the principles of MRgFUS, describing patient selection criteria for the treatments performed at our center and we present a series of five selected patients with symptomatic uterine fibroids treated with this not yet widely known technique, showing its efficacy in symptom improvement and fibroid volume reduction.

  10. Functional magnetic resonance imaging-controlled neuronavigator-guided brain surgery: a case report.

    Science.gov (United States)

    Morioka, J; Nishizaki, T; Tokumaru, T; Uesugi, S; Yamashita, K; Ito, H; Suzuki, M

    2001-05-01

    The effectiveness of functional magnetic resonance imaging (f-MRI)-controlled and navigator-guided brain surgery for a patient with a recurrent astrocytoma is demonstrated. Preoperative f-MRI was performed in order to identify the motor area and ensure that the tumour was in the left prefrontal area. A more aggressive operation was planned for the recurrent tumour. The f-MRI data were input to the MKM navigation system and during the operation the contours of the tumour and motor area were visualised b y the microscope of the navigation system. The tumour and surrounding gliotic brain tissue were removed completely. The diagnosis was a grade III astrocytoma. The combination of the navigation system and f-MRI was useful for preoperative design of the surgical strategy, and tumour orientation during the operation, enabling aggressive surgery to be performed without functional deficits ensuing. Copyright 2001 Harcourt Publishers Ltd.

  11. Magnetic Resonance Imaging-Guided Focused Ultrasound Surgery for the Treatment of Symptomatic Uterine Fibroids.

    Science.gov (United States)

    Geraci, Laura; Napoli, Alessandro; Catalano, Carlo; Midiri, Massimo; Gagliardo, Cesare

    2017-01-01

    Uterine fibroids, the most common benign tumor in women of childbearing age, may cause symptoms including pelvic pain, menorrhagia, dysmenorrhea, pressure, urinary symptoms, and infertility. Various approaches are available to treat symptomatic uterine fibroids. Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) represents a recently introduced noninvasive safe and effective technique that can be performed without general anesthesia, in an outpatient setting. We review the principles of MRgFUS, describing patient selection criteria for the treatments performed at our center and we present a series of five selected patients with symptomatic uterine fibroids treated with this not yet widely known technique, showing its efficacy in symptom improvement and fibroid volume reduction.

  12. An ultra-high field strength MR image-guided robotic needle delivery system for in-bore small animal interventions.

    Science.gov (United States)

    Gravett, Matthew; Cepek, Jeremy; Fenster, Aaron

    2017-11-01

    The purpose of this study was to develop and validate an image-guided robotic needle delivery system for accurate and repeatable needle targeting procedures in mouse brains inside the 12 cm inner diameter gradient coil insert of a 9.4 T MR scanner. Many preclinical research techniques require the use of accurate needle deliveries to soft tissues, including brain tissue. Soft tissues are optimally visualized in MR images, which offer high-soft tissue contrast, as well as a range of unique imaging techniques, including functional, spectroscopy and thermal imaging, however, there are currently no solutions for delivering needles to small animal brains inside the bore of an ultra-high field MR scanner. This paper describes the mechatronic design, evaluation of MR compatibility, registration technique, mechanical calibration, the quantitative validation of the in-bore image-guided needle targeting accuracy and repeatability, and demonstrated the system's ability to deliver needles in situ. Our six degree-of-freedom, MR compatible, mechatronic system was designed to fit inside the bore of a 9.4 T MR scanner and is actuated using a combination of piezoelectric and hydraulic mechanisms. The MR compatibility and targeting accuracy of the needle delivery system are evaluated to ensure that the system is precisely calibrated to perform the needle targeting procedures. A semi-automated image registration is performed to link the robot coordinates to the MR coordinate system. Soft tissue targets can be accurately localized in MR images, followed by automatic alignment of the needle trajectory to the target. Intra-procedure visualization of the needle target location and the needle were confirmed through MR images after needle insertion. The effects of geometric distortions and signal noise were found to be below threshold that would have an impact on the accuracy of the system. The system was found to have negligible effect on the MR image signal noise and geometric distortion

  13. Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

    Science.gov (United States)

    Sadeh, Boaz; Yovel, Galit

    2014-01-01

    Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator's coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes. PMID:24893706

  14. Extracting visual evoked potentials from EEG data recorded during fMRI-guided transcranial magnetic stimulation.

    Science.gov (United States)

    Sadeh, Boaz; Yovel, Galit

    2014-05-12

    Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator's coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

  15. Nanoscale Metal-Organic Frameworks Decorated with Graphene Oxide for Magnetic Resonance Imaging Guided Photothermal Therapy.

    Science.gov (United States)

    Meng, Jing; Chen, Xiujin; Tian, Yang; Li, Zhongfeng; Zheng, Qingfeng

    2017-12-11

    Imaging-guided photothermal therapy (PTT) provides an attractive way to treat cancer. A composite material of a nanoscale metal-organic framework (NMOF) and graphene oxide (GO) has been prepared for potential use in tumor-guided PTT with magnetic resonance imaging (MRI). The NMOFs containing Fe 3+ were prefabricated with an octahedral morphology through a solvothermal reaction to offer a strong T 2 -weighted contrast in MRI. Then the NMOFs were decorated with GO nanosheets, which had good photothermal properties. After decoration, zeta-potential characterization shows that the aqueous stability of the composite material is enhanced, UV/Vis and near-infrared (NIR) spectra confirm that NIR absorption is also increased, and photothermal experiments reveal that the composite materials express higher photothermal conversion effects and conversion stability. The fabricated NMOF/GO shows low cytotoxicity, effective T 2 -weighted contrast of MRI, and positive PTT behavior for a tumor model in vitro. The performance of the composite NMOF/GO for MRI and PTT was also tested upon injection into A549 tumor-bearing mice. The studies in vivo revealed that the fabricated NMOF/GO was efficient in T 2 -weighted imaging and ablation of the A549 tumor with low cytotoxicity, which implied that the prepared composite contrast agent was a potential multifunctional nanotheranostic agent. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Student representation of magnetic field concepts in learning by guided inquiry

    International Nuclear Information System (INIS)

    Fatmaryanti, Siska Desy; Suparmi; Sarwanto; Ashadi

    2017-01-01

    The purpose of this study was to determine the change of student’s representation after the intervention of learning by guided inquiry. The population in this research were all students who took a fundamental physics course, consisted of 28 students academic year 2016, Department of Physics Education, Faculty of Teacher Training and Education, University of Muhammadiyah Purworejo. This study employed a quasi-experimental design with group pre-test and post-test. The result of the research showed that the average of students representation of magnetic field before implementation of guided inquiry was 28,6 % and after implementation was 71,4%. It means that the student’s ability of multi-representation increase. Moreover, the number of students who is able to write and draw based on experiment data increased from 10,7% to 21,4 %. It was also showed that the number of student with no answer decreased from 28,5% to 10,7%. (paper)

  17. Student representation of magnetic field concepts in learning by guided inquiry

    Science.gov (United States)

    Desy Fatmaryanti, Siska; Suparmi; Sarwanto; Ashadi

    2017-01-01

    The purpose of this study was to determine the change of student’s representation after the intervention of learning by guided inquiry. The population in this research were all students who took a fundamental physics course, consisted of 28 students academic year 2016, Department of Physics Education, Faculty of Teacher Training and Education, University of Muhammadiyah Purworejo. This study employed a quasi-experimental design with group pre-test and post-test. The result of the research showed that the average of students representation of magnetic field before implementation of guided inquiry was 28,6 % and after implementation was 71,4%. It means that the student’s ability of multi-representation increase. Moreover, the number of students who is able to write and draw based on experiment data increased from 10,7% to 21,4 %. It was also showed that the number of student with no answer decreased from 28,5% to 10,7%.

  18. Image-Based Monitoring of Magnetic Resonance-Guided Thermoablative Therapies for Liver Tumors

    Energy Technology Data Exchange (ETDEWEB)

    Rempp, Hansjoerg, E-mail: hansjoerg.rempp@med.uni-tuebingen.de; Clasen, Stephan [Eberhard Karls University of Tuebingen, Department of Diagnostic and Interventional Radiology (Germany); Pereira, Philippe L. [SLK-Kliniken, Clinic for Radiology, Nuclear Medicine, and Minimal Invasive Therapies (Germany)

    2012-12-15

    Minimally invasive treatment options for liver tumor therapy have been increasingly used during the last decade because their benefit has been proven for primary and inoperable secondary liver tumors. Among these, radiofrequency ablation has gained widespread consideration. Optimal image-guidance offers precise anatomical information, helps to position interventional devices, and allows for differentiation between already-treated and remaining tumor tissue. Patient safety and complete ablation of the entire tumor are the overriding objectives of tumor ablation. These may be achieved most elegantly with magnetic resonance (MR)-guided therapy, where monitoring can be performed based on precise soft-tissue imaging and additional components, such as diffusion-weighted imaging and temperature mapping. New MR scanner types and newly developed sequence techniques have enabled MR-guided intervention to move beyond the experimental phase. This article reviews the current role of MR imaging in guiding radiofrequency ablation. Signal characteristics of primary and secondary liver tumors are identified, and signal alteration during therapy is described. Diffusion-weighted imaging (DWI) and temperature mapping as special components of MR therapy monitoring are introduced. Practical information concerning coils, sequence selection, and parameters, as well as sequence gating, is given. In addition, sources of artifacts are identified and techniques to decrease them are introduced, and the characteristic signs of residual tumor in T1-, T2-, and DWI are described. We hope to enable the reader to choose MR sequences that allow optimal therapy monitoring depending on the initial signal characteristics of the tumor as well as its size and location in the liver.

  19. Image-Based Monitoring of Magnetic Resonance-Guided Thermoablative Therapies for Liver Tumors

    International Nuclear Information System (INIS)

    Rempp, Hansjörg; Clasen, Stephan; Pereira, Philippe L.

    2012-01-01

    Minimally invasive treatment options for liver tumor therapy have been increasingly used during the last decade because their benefit has been proven for primary and inoperable secondary liver tumors. Among these, radiofrequency ablation has gained widespread consideration. Optimal image-guidance offers precise anatomical information, helps to position interventional devices, and allows for differentiation between already-treated and remaining tumor tissue. Patient safety and complete ablation of the entire tumor are the overriding objectives of tumor ablation. These may be achieved most elegantly with magnetic resonance (MR)-guided therapy, where monitoring can be performed based on precise soft-tissue imaging and additional components, such as diffusion-weighted imaging and temperature mapping. New MR scanner types and newly developed sequence techniques have enabled MR-guided intervention to move beyond the experimental phase. This article reviews the current role of MR imaging in guiding radiofrequency ablation. Signal characteristics of primary and secondary liver tumors are identified, and signal alteration during therapy is described. Diffusion-weighted imaging (DWI) and temperature mapping as special components of MR therapy monitoring are introduced. Practical information concerning coils, sequence selection, and parameters, as well as sequence gating, is given. In addition, sources of artifacts are identified and techniques to decrease them are introduced, and the characteristic signs of residual tumor in T1-, T2-, and DWI are described. We hope to enable the reader to choose MR sequences that allow optimal therapy monitoring depending on the initial signal characteristics of the tumor as well as its size and location in the liver.

  20. Magnetic Particle / Magnetic Resonance Imaging: In-Vitro MPI-Guided Real Time Catheter Tracking and 4D Angioplasty Using a Road Map and Blood Pool Tracer Approach.

    Directory of Open Access Journals (Sweden)

    Johannes Salamon

    Full Text Available In-vitro evaluation of the feasibility of 4D real time tracking of endovascular devices and stenosis treatment with a magnetic particle imaging (MPI / magnetic resonance imaging (MRI road map approach and an MPI-guided approach using a blood pool tracer.A guide wire and angioplasty-catheter were labeled with a thin layer of magnetic lacquer. For real time MPI a custom made software framework was developed. A stenotic vessel phantom filled with saline or superparamagnetic iron oxide nanoparticles (MM4 was equipped with bimodal fiducial markers for co-registration in preclinical 7T MRI and MPI. In-vitro angioplasty was performed inflating the balloon with saline or MM4. MPI data were acquired using a field of view of 37.3×37.3×18.6 mm3 and a frame rate of 46 volumes/sec. Analysis of the magnetic lacquer-marks on the devices were performed with electron microscopy, atomic absorption spectrometry and micro-computed tomography.Magnetic marks allowed for MPI/MRI guidance of interventional devices. Bimodal fiducial markers enable MPI/MRI image fusion for MRI based roadmapping. MRI roadmapping and the blood pool tracer approach facilitate MPI real time monitoring of in-vitro angioplasty. Successful angioplasty was verified with MPI and MRI. Magnetic marks consist of micrometer sized ferromagnetic plates mainly composed of iron and iron oxide.4D real time MP imaging, tracking and guiding of endovascular instruments and in-vitro angioplasty is feasible. In addition to an approach that requires a blood pool tracer, MRI based roadmapping might emerge as a promising tool for radiation free 4D MPI-guided interventions.

  1. Magnetic Particle / Magnetic Resonance Imaging: In-Vitro MPI-Guided Real Time Catheter Tracking and 4D Angioplasty Using a Road Map and Blood Pool Tracer Approach.

    Science.gov (United States)

    Salamon, Johannes; Hofmann, Martin; Jung, Caroline; Kaul, Michael Gerhard; Werner, Franziska; Them, Kolja; Reimer, Rudolph; Nielsen, Peter; Vom Scheidt, Annika; Adam, Gerhard; Knopp, Tobias; Ittrich, Harald

    2016-01-01

    In-vitro evaluation of the feasibility of 4D real time tracking of endovascular devices and stenosis treatment with a magnetic particle imaging (MPI) / magnetic resonance imaging (MRI) road map approach and an MPI-guided approach using a blood pool tracer. A guide wire and angioplasty-catheter were labeled with a thin layer of magnetic lacquer. For real time MPI a custom made software framework was developed. A stenotic vessel phantom filled with saline or superparamagnetic iron oxide nanoparticles (MM4) was equipped with bimodal fiducial markers for co-registration in preclinical 7T MRI and MPI. In-vitro angioplasty was performed inflating the balloon with saline or MM4. MPI data were acquired using a field of view of 37.3×37.3×18.6 mm3 and a frame rate of 46 volumes/sec. Analysis of the magnetic lacquer-marks on the devices were performed with electron microscopy, atomic absorption spectrometry and micro-computed tomography. Magnetic marks allowed for MPI/MRI guidance of interventional devices. Bimodal fiducial markers enable MPI/MRI image fusion for MRI based roadmapping. MRI roadmapping and the blood pool tracer approach facilitate MPI real time monitoring of in-vitro angioplasty. Successful angioplasty was verified with MPI and MRI. Magnetic marks consist of micrometer sized ferromagnetic plates mainly composed of iron and iron oxide. 4D real time MP imaging, tracking and guiding of endovascular instruments and in-vitro angioplasty is feasible. In addition to an approach that requires a blood pool tracer, MRI based roadmapping might emerge as a promising tool for radiation free 4D MPI-guided interventions.

  2. Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field.

    Science.gov (United States)

    von Allwörden, Henning; Eich, Andreas; Knol, Elze J; Hermenau, Jan; Sonntag, Andreas; Gerritsen, Jan W; Wegner, Daniel; Khajetoorians, Alexander A

    2018-03-01

    We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).

  3. A modular designed ultra-high-vacuum spin-polarized scanning tunneling microscope with controllable magnetic fields for investigating epitaxial thin films.

    Science.gov (United States)

    Wang, Kangkang; Lin, Wenzhi; Chinchore, Abhijit V; Liu, Yinghao; Smith, Arthur R

    2011-05-01

    A room-temperature ultra-high-vacuum scanning tunneling microscope for in situ scanning freshly grown epitaxial films has been developed. The core unit of the microscope, which consists of critical components including scanner and approach motors, is modular designed. This enables easy adaptation of the same microscope units to new growth systems with different sample-transfer geometries. Furthermore the core unit is designed to be fully compatible with cryogenic temperatures and high magnetic field operations. A double-stage spring suspension system with eddy current damping has been implemented to achieve ≤5 pm z stability in a noisy environment and in the presence of an interconnected growth chamber. Both tips and samples can be quickly exchanged in situ; also a tunable external magnetic field can be introduced using a transferable permanent magnet shuttle. This allows spin-polarized tunneling with magnetically coated tips. The performance of this microscope is demonstrated by atomic-resolution imaging of surface reconstructions on wide band-gap GaN surfaces and spin-resolved experiments on antiferromagnetic Mn(3)N(2)(010) surfaces.

  4. Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field

    Science.gov (United States)

    von Allwörden, Henning; Eich, Andreas; Knol, Elze J.; Hermenau, Jan; Sonntag, Andreas; Gerritsen, Jan W.; Wegner, Daniel; Khajetoorians, Alexander A.

    2018-03-01

    We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).

  5. Sensitivity enhancement by chromatographic peak concentration with ultra-high performance liquid chromatography-nuclear magnetic resonance spectroscopy for minor impurity analysis.

    Science.gov (United States)

    Tokunaga, Takashi; Akagi, Ken-Ichi; Okamoto, Masahiko

    2017-07-28

    High performance liquid chromatography can be coupled with nuclear magnetic resonance (NMR) spectroscopy to give a powerful analytical method known as liquid chromatography-nuclear magnetic resonance (LC-NMR) spectroscopy, which can be used to determine the chemical structures of the components of complex mixtures. However, intrinsic limitations in the sensitivity of NMR spectroscopy have restricted the scope of this procedure, and resolving these limitations remains a critical problem for analysis. In this study, we coupled ultra-high performance liquid chromatography (UHPLC) with NMR to give a simple and versatile analytical method with higher sensitivity than conventional LC-NMR. UHPLC separation enabled the concentration of individual peaks to give a volume similar to that of the NMR flow cell, thereby maximizing the sensitivity to the theoretical upper limit. The UHPLC concentration of compound peaks present at typical impurity levels (5.0-13.1 nmol) in a mixture led to at most three-fold increase in the signal-to-noise ratio compared with LC-NMR. Furthermore, we demonstrated the use of UHPLC-NMR for obtaining structural information of a minor impurity in a reaction mixture in actual laboratory-scale development of a synthetic process. Using UHPLC-NMR, the experimental run times for chromatography and NMR were greatly reduced compared with LC-NMR. UHPLC-NMR successfully overcomes the difficulties associated with analyses of minor components in a complex mixture by LC-NMR, which are problematic even when an ultra-high field magnet and cryogenic probe are used. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Histopathology of breast cancer after magnetic resonance-guided high-intensity focused ultrasound and radiofrequency ablation

    NARCIS (Netherlands)

    Knuttel, Floor; Waaijer, Laurien; Merckel, LG; van den Bosch, Maurice A A J; Witkamp, Arjen J.; Deckers, Roel; van Diest, Paul J.

    AIMS: Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation and radiofrequency ablation (RFA) are being researched as possible substitutes for surgery in breast cancer patients. The histopathological appearance of ablated tissue has not been studied in great detail. This

  7. Effects of magnetic resonance-guided high-intensity focused ultrasound ablation on bone mechanical properties and modeling

    NARCIS (Netherlands)

    Yeoh, S.Y.; Arias Moreno, A.J.; Rietbergen, van B.; Hoeve, ter N.D.; Diest, van P.J.; Grull, H.

    2015-01-01

    Background Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a promising technique for palliative treatment of bone pain. In this study, the effects of MR-HIFU ablation on bone mechanics and modeling were investigated. Methods A total of 12 healthy rat femurs were ablated

  8. Particle Filter-Based Target Tracking Algorithm for Magnetic Resonance-Guided Respiratory Compensation : Robustness and Accuracy Assessment

    NARCIS (Netherlands)

    Bourque, Alexandra E; Bedwani, Stéphane; Carrier, Jean-François; Ménard, Cynthia; Borman, Pim; Bos, Clemens; Raaymakers, Bas W; Mickevicius, Nikolai; Paulson, Eric; Tijssen, Rob H N

    PURPOSE: To assess overall robustness and accuracy of a modified particle filter-based tracking algorithm for magnetic resonance (MR)-guided radiation therapy treatments. METHODS AND MATERIALS: An improved particle filter-based tracking algorithm was implemented, which used a normalized

  9. Motion of guiding center drift atoms in the electric and magnetic field of a Penning trap

    International Nuclear Information System (INIS)

    Kuzmin, S.G.; O'Neil, T.M.

    2005-01-01

    The ApparaTus for High precision Experiment on Neutral Antimatter and antihydrogen TRAP collaborations have produced antihydrogen atoms by recombination in a cryogenic antiproton-positron plasma. This paper discusses the motion of the weakly bound atoms in the electric and magnetic field of the plasma and trap. The effective electric field in the moving frame of the atom polarizes the atom, and then gradients in the field exert a force on the atom. An approximate equation of motion for the atom center of mass is obtained by averaging over the rapid internal dynamics of the atom. The only remnant of the atom internal dynamics that enters this equation is the polarizability for the atom. This coefficient is evaluated for the weakly bound and strongly magnetized (guiding center drift) atoms understood to be produced in the antihydrogen experiments. Application of the approximate equation of motion shows that the atoms can be trapped radially in the large space charge field near the edge of the positron column. Also, an example is presented for which there is full three-dimensional trapping, not just radial trapping. Even untrapped atoms follow curved trajectories, and such trajectories are discussed for the important class of atoms that reach a field ionization diagnostic. Finally, the critical field for ionization is determined as an upper bound on the range of applicability of the theory

  10. Development of a magnetic beam guiding system for tumor-specific radiotherapy using heavy, charged particles

    International Nuclear Information System (INIS)

    Haberer, T.

    1994-06-01

    An active, magnetic beam guiding system was developed and tested for the purpose of enhanced and tumor-specific irradiation of irregularly shaped target volumina. Combining intensity-controlled wobbling in rapidly changing magnetic fields with the heavy-ion synchrotron's capacity of fast energy variation achieved a new technique allowing good range modulation. This technique allows the calculated dose distribution to be exactly matched to target contours, and at the same time guarantees best possible quality of the radiation beam, since there is no need for use of mechanical beam shaping members. The components of the scanning system and a specifically designed instrumentation and control concept for this configuration were integrated into the synchrotron's control system, so that there is now a system available offering free selection of beam characteristics combined with energy variation along with the pulsed operation of the accelerator. The system was tested at the biophysical measuring unit of the GSI implementing an elaborated irradiation method at this unit equipped with tools for physico-technical irradiation planning and performance. Methods were designed and tested for optimizing the beam path within a given contour, the optimization taking into account the effects of transmission functions of the scanner components on the results of radiation treatments. (orig.) [de

  11. Priori mask guided image reconstruction (p-MGIR) for ultra-low dose cone-beam computed tomography

    Science.gov (United States)

    Park, Justin C.; Zhang, Hao; Chen, Yunmei; Fan, Qiyong; Kahler, Darren L.; Liu, Chihray; Lu, Bo

    2015-11-01

    Recently, the compressed sensing (CS) based iterative reconstruction method has received attention because of its ability to reconstruct cone beam computed tomography (CBCT) images with good quality using sparsely sampled or noisy projections, thus enabling dose reduction. However, some challenges remain. In particular, there is always a tradeoff between image resolution and noise/streak artifact reduction based on the amount of regularization weighting that is applied uniformly across the CBCT volume. The purpose of this study is to develop a novel low-dose CBCT reconstruction algorithm framework called priori mask guided image reconstruction (p-MGIR) that allows reconstruction of high-quality low-dose CBCT images while preserving the image resolution. In p-MGIR, the unknown CBCT volume was mathematically modeled as a combination of two regions: (1) where anatomical structures are complex, and (2) where intensities are relatively uniform. The priori mask, which is the key concept of the p-MGIR algorithm, was defined as the matrix that distinguishes between the two separate CBCT regions where the resolution needs to be preserved and where streak or noise needs to be suppressed. We then alternately updated each part of image by solving two sub-minimization problems iteratively, where one minimization was focused on preserving the edge information of the first part while the other concentrated on the removal of noise/artifacts from the latter part. To evaluate the performance of the p-MGIR algorithm, a numerical head-and-neck phantom, a Catphan 600 physical phantom, and a clinical head-and-neck cancer case were used for analysis. The results were compared with the standard Feldkamp-Davis-Kress as well as conventional CS-based algorithms. Examination of the p-MGIR algorithm showed that high-quality low-dose CBCT images can be reconstructed without compromising the image resolution. For both phantom and the patient cases, the p-MGIR is able to achieve a clinically

  12. On Multiple Hall-Like Electron Currents and Tripolar Guide Magnetic Field Perturbations During Kelvin-Helmholtz Waves

    Science.gov (United States)

    Sturner, Andrew P.; Eriksson, Stefan; Nakamura, Takuma; Gershman, Daniel J.; Plaschke, Ferdinand; Ergun, Robert E.; Wilder, Frederick D.; Giles, Barbara; Pollock, Craig; Paterson, William R.; Strangeway, Robert J.; Baumjohann, Wolfgang; Burch, James L.

    2018-02-01

    Two magnetopause current sheet crossings with tripolar guide magnetic field signatures were observed by multiple Magnetosphere Multiscale (MMS) spacecraft during Kelvin-Helmholtz wave activity. The two out-of-plane magnetic field depressions of the tripolar guide magnetic field are largely supported by the observed in-plane electron currents, which are reminiscent of two clockwise Hall current loop systems. A comparison with a three-dimensional kinetic simulation of Kelvin-Helmholtz waves and vortex-induced reconnection suggests that MMS likely encountered the two Hall magnetic field depressions on either side of a magnetic reconnection X-line. Moreover, MMS observed an out-of-plane current reversal and a corresponding in-plane magnetic field rotation at the center of one of the current sheets, suggesting the presence of two adjacent flux ropes. The region inside one of the ion-scale flux ropes was characterized by an observed decrease of the total magnetic field, a strong axial current, and significant enhancements of electron density and parallel electron temperature. The flux rope boundary was characterized by currents opposite this axial current, strong in-plane and converging electric fields, parallel electric fields, and weak electron-frame Joule dissipation. These return current region observations may reflect a need to support the axial current rather than representing local reconnection signatures in the absence of any exhausts.

  13. Electrodynamic support and/or guide device for a magnetic levitation train. Elektrodynamische Trag- und/oder Fuehrungsvorrichtung fuer eine Magnetschwebebahn

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberg, A

    1979-02-15

    The invention refers to an electrodynamic support and/or guide device for a magnetic levitation train, in which magnets, particularly superconducting magnets are situated on a vehicle, which has rail-like electrically conducting plates or loops on the track. The purpose of the invention is to describe such an electrodynamic support and/or guide device, which can achieve contactless support or guidance of an electrodynamic levitation vehicle when stopped. According to the invention, the problem is solved by the magnetic fields of the support and/or guide magnets acting on the electrically conducting plates or loops of the track being controlled so that moving magnetic fields relative to the vehicle are produced. In this way it is possible to support and/or to guide the vehicle electro-dynamically from standstill to the maximum speed and to drive or brake it.

  14. Nu shifts in betatron oscillations from uniform perturbations in the presence of non-linear magnetic guide fields

    International Nuclear Information System (INIS)

    Crebbin, K.C.

    1985-05-01

    Uniform magnetic field perturbations cause a closed orbit distortion in a circular accelerator. If the magnetic guide field is non-linear these perturbations can also cause a Nu shift in the betatron oscillations. Such a shift in radial Nu values has been observed in the Bevalac while studying the low energy resonant extraction system. In the Bevalac, the radial perturbation comes from the quadrants being magnetically about 0.8% longer than 90 0 . The normal effect of this type of perturbation is a radial closed orbit shift and orbit distortion. The Nu shift, associated with this type of perturbation in the presence of a non-linear guide field, is discussed in this paper. A method of handling the non-linear n values is discussed as well as the mechanism for the associated Nu shift. Computer calculations are compared to measurements. 2 refs., 4 figs

  15. Magnetic Random Access Memory based non-volatile asynchronous Muller cell for ultra-low power autonomous applications

    Science.gov (United States)

    Di Pendina, G.; Zianbetov, E.; Beigne, E.

    2015-05-01

    Micro and nano electronic integrated circuit domain is today mainly driven by the advent of the Internet of Things for which the constraints are strong, especially in terms of power consumption and autonomy, not only during the computing phases but also during the standby or idle phases. In such ultra-low power applications, the circuit has to meet new constraints mainly linked to its changing energetic environment: long idle phases, automatic wake up, data back-up when the circuit is sporadically turned off, and ultra-low voltage power supply operation. Such circuits have to be completely autonomous regarding their unstable environment, while remaining in an optimum energetic configuration. Therefore, we propose in this paper the first MRAM-based non-volatile asynchronous Muller cell. This cell has been simulated and characterized in a very advanced 28 nm CMOS fully depleted silicon-on-insulator technology, presenting good power performance results due to an extremely efficient body biasing control together with ultra-wide supply voltage range from 160 mV up to 920 mV. The leakage current can be reduced to 154 pA thanks to reverse body biasing. We also propose an efficient standard CMOS bulk version of this cell in order to be compatible with different fabrication processes.

  16. Magnetic Random Access Memory based non-volatile asynchronous Muller cell for ultra-low power autonomous applications

    Energy Technology Data Exchange (ETDEWEB)

    Di Pendina, G., E-mail: gregory.dipendina@cea.fr, E-mail: eldar.zianbetov@cea.fr, E-mail: edith.beigne@cea.fr; Zianbetov, E., E-mail: gregory.dipendina@cea.fr, E-mail: eldar.zianbetov@cea.fr, E-mail: edith.beigne@cea.fr [Univ. Grenoble Alpes, INAC-SPINTEC, F-38000 Grenoble (France); CNRS, SPINTEC, F-38000 Grenoble (France); CEA, INAC-SPINTEC, F-38000 Grenoble (France); Beigne, E., E-mail: gregory.dipendina@cea.fr, E-mail: eldar.zianbetov@cea.fr, E-mail: edith.beigne@cea.fr [Univ. Grenoble Alpes, CEA, LETI, F-38000 Grenoble (France)

    2015-05-07

    Micro and nano electronic integrated circuit domain is today mainly driven by the advent of the Internet of Things for which the constraints are strong, especially in terms of power consumption and autonomy, not only during the computing phases but also during the standby or idle phases. In such ultra-low power applications, the circuit has to meet new constraints mainly linked to its changing energetic environment: long idle phases, automatic wake up, data back-up when the circuit is sporadically turned off, and ultra-low voltage power supply operation. Such circuits have to be completely autonomous regarding their unstable environment, while remaining in an optimum energetic configuration. Therefore, we propose in this paper the first MRAM-based non-volatile asynchronous Muller cell. This cell has been simulated and characterized in a very advanced 28 nm CMOS fully depleted silicon-on-insulator technology, presenting good power performance results due to an extremely efficient body biasing control together with ultra-wide supply voltage range from 160 mV up to 920 mV. The leakage current can be reduced to 154 pA thanks to reverse body biasing. We also propose an efficient standard CMOS bulk version of this cell in order to be compatible with different fabrication processes.

  17. Magnetic Random Access Memory based non-volatile asynchronous Muller cell for ultra-low power autonomous applications

    International Nuclear Information System (INIS)

    Di Pendina, G.; Zianbetov, E.; Beigne, E.

    2015-01-01

    Micro and nano electronic integrated circuit domain is today mainly driven by the advent of the Internet of Things for which the constraints are strong, especially in terms of power consumption and autonomy, not only during the computing phases but also during the standby or idle phases. In such ultra-low power applications, the circuit has to meet new constraints mainly linked to its changing energetic environment: long idle phases, automatic wake up, data back-up when the circuit is sporadically turned off, and ultra-low voltage power supply operation. Such circuits have to be completely autonomous regarding their unstable environment, while remaining in an optimum energetic configuration. Therefore, we propose in this paper the first MRAM-based non-volatile asynchronous Muller cell. This cell has been simulated and characterized in a very advanced 28 nm CMOS fully depleted silicon-on-insulator technology, presenting good power performance results due to an extremely efficient body biasing control together with ultra-wide supply voltage range from 160 mV up to 920 mV. The leakage current can be reduced to 154 pA thanks to reverse body biasing. We also propose an efficient standard CMOS bulk version of this cell in order to be compatible with different fabrication processes

  18. Generation of ultra-long pure magnetization needle and multiple spots by phase modulated doughnut Gaussian beam

    Science.gov (United States)

    Udhayakumar, M.; Prabakaran, K.; Rajesh, K. B.; Jaroszewicz, Z.; Belafhal, Abdelmajid; Velauthapillai, Dhayalan

    2018-06-01

    Based on vector diffraction theory and inverse Faraday effect (IFE), the light induced magnetization distribution of a tightly focused azimuthally polarized doughnut Gaussian beam superimposed with a helical phase and modulated by an optimized multi belt complex phase filter (MBCPF) is analysed numerically. It is noted that by adjusting the radii of different rings of the complex phase filter, one can achieve many novel magnetization focal distribution such as sub wavelength scale (0.29λ) and super long (52.2λ) longitudinal magnetic probe suitable for all optical magnetic recording and the formation of multiple magnetization chain with four, six and eight sub-wavelength spherical magnetization spots suitable for multiple trapping of magnetic particles are achieved.

  19. Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation

    Directory of Open Access Journals (Sweden)

    Herynek V

    2016-08-01

    Full Text Available Vít Herynek,1 Karolína Turnovcová,2 Pavel Veverka,3 Tereza Dědourková,4,5 Pavel Žvátora,6 Pavla Jendelová,2 Andrea Gálisová,1 Lucie Kosinová,7 Klára Jiráková,2 Eva Syková2 1MR-Unit, Radiodiagnostic and Interventional Radiology Department, Institute for Clinical and Experimental Medicine, Prague, 2Department of Neuroscience, Institute of Experimental Medicine, 3Department of Magnetics and Superconductors, Institute of Physics, Czech Academy of Sciences, Prague, 4Department of Inorganic Technology, Faculty of Chemical Technology, University of Pardubice, 5SYNPO, akciová společnost, Pardubice, 6Department of Analytical Chemistry, Institute of Chemical Technology, 7Diabetes Center, Institute for Clinical and Experimental Medicine, Prague, Czech Republic Introduction: Magnetic nanoparticles (NPs represent a tool for use in magnetic resonance imaging (MRI-guided thermoablation of tumors using an external high-frequency (HF magnetic field. To avoid local overheating, perovskite NPs with a lower Curie temperature (Tc were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis. Methods: Perovskite NPs (Tc =66°C–74°C were characterized and tested both in vitro and in vivo. In vitro, the cells suspended with NPs were exposed to a HF magnetic field together with control samples. In vivo, a NP suspension was injected into a induced tumor in rats. Distribution was checked by MRI and the rats were exposed to a HF field together with control animals. Apoptosis in the tissue was evaluated. Results and discussion: In vitro, the high concentration of suspended NPs caused an increase of the temperature in the cell sample, leading to cell death. In vivo, MRI confirmed distribution of the NPs in the tumor. The temperature in the tumor with injected NPs did not increase

  20. Ultra-low switching energy and scaling in electric-field-controlled nanoscale magnetic tunnel junctions with high resistance-area product

    Energy Technology Data Exchange (ETDEWEB)

    Grezes, C.; Alzate, J. G.; Cai, X.; Wang, K. L. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Ebrahimi, F.; Khalili Amiri, P. [Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Inston, Inc., Los Angeles, California 90024 (United States); Katine, J. A. [HGST, Inc., San Jose, California 95135 (United States); Langer, J.; Ocker, B. [Singulus Technologies AG, Kahl am Main 63796 (Germany)

    2016-01-04

    We report electric-field-induced switching with write energies down to 6 fJ/bit for switching times of 0.5 ns, in nanoscale perpendicular magnetic tunnel junctions (MTJs) with high resistance-area product and diameters down to 50 nm. The ultra-low switching energy is made possible by a thick MgO barrier that ensures negligible spin-transfer torque contributions, along with a reduction of the Ohmic dissipation. We find that the switching voltage and time are insensitive to the junction diameter for high-resistance MTJs, a result accounted for by a macrospin model of purely voltage-induced switching. The measured performance enables integration with same-size CMOS transistors in compact memory and logic integrated circuits.

  1. Novel aluminum near field transducer and highly integrated micro-nano-optics design for heat-assisted ultra-high-density magnetic recording

    International Nuclear Information System (INIS)

    Miao, Lingyun; Hsiang, Thomas Y; Stoddart, Paul R

    2014-01-01

    Heat-assisted magnetic recording (HAMR) has attracted increasing attention as one of the most promising future techniques for ultra-high-density magnetic recording beyond the current limit of 1 Tb in −2 . Localized surface plasmon resonance plays an important role in HAMR by providing a highly focused optical spot for heating the recording medium within a small volume. In this work, we report an aluminum near-field transducer (NFT) based on a novel bow-tie design. At an operating wavelength of 450 nm, the proposed transducer can generate a 35 nm spot size inside the magnetic recording medium, corresponding to a recording density of up to 2 Tb in −2 . A highly integrated micro-nano-optics design is also proposed to ensure process compatibility and corrosion-resistance of the aluminum NFT. Our work has demonstrated the feasibility of using aluminum as a plasmonic material for HAMR, with advantages of reduced cost and improved efficiency compared to traditional noble metals. (paper)

  2. Feasibility of real-time magnetic resonance imaging-guided endomyocardial biopsies: An in-vitro study.

    Science.gov (United States)

    Lossnitzer, Dirk; Seitz, Sebastian A; Krautz, Birgit; Schnackenburg, Bernhard; André, Florian; Korosoglou, Grigorios; Katus, Hugo A; Steen, Henning

    2015-07-26

    To investigate if magnetic resonance (MR)-guided biopsy can improve the performance and safety of such procedures. A novel MR-compatible bioptome was evaluated in a series of in-vitro experiments in a 1.5T magnetic resonance imaging (MRI) system. The bioptome was inserted into explanted porcine and bovine hearts under real-time MR-guidance employing a steady state free precession sequence. The artifact produced by the metal element at the tip and the signal voids caused by the bioptome were visually tracked for navigation and allowed its constant and precise localization. Cardiac structural elements and the target regions for the biopsy were clearly visible. Our method allowed a significantly better spatial visualization of the bioptoms tip compared to conventional X-ray guidance. The specific device design of the bioptome avoided inducible currents and therefore subsequent heating. The novel MR-compatible bioptome provided a superior cardiovascular magnetic resonance (imaging) soft-tissue visualization for MR-guided myocardial biopsies. Not at least the use of MRI guidance for endomyocardial biopsies completely avoided radiation exposure for both patients and interventionalists. MRI-guided endomyocardial biopsies provide a better than conventional X-ray guided navigation and could therefore improve the specificity and reproducibility of cardiac biopsies in future studies.

  3. Magnetic Resonance Imaging-Guided Intracavitary Brachytherapy for Cancer of the Cervix

    International Nuclear Information System (INIS)

    Zwahlen, Daniel; Jezioranski, John; Chan, Philip; Haider, Masoom A.; Cho, Young-Bin; Yeung, Ivan; Levin, Wilfred; Manchul, Lee; Fyles, Anthony; Milosevic, Michael

    2009-01-01

    Purpose: To determine the feasibility and benefits of optimized magnetic resonance imaging (MRI)-guided brachytherapy (BT) for cancer of the cervix. Methods and Materials: A total of 20 patients with International Federation of Gynecology and Obstetrics Stage IB-IV cervical cancer had an MRI-compatible intrauterine BT applicator inserted after external beam radiotherapy. MRI scans were acquired, and the gross tumor volume at diagnosis and at BT, the high-risk (HR) and intermediate-risk clinical target volume (CTV), and rectal, sigmoid, and bladder walls were delineated. Pulsed-dose-rate BT was planned and delivered in a conventional manner. Optimized MRI-based plans were developed and compared with the conventional plans. Results: The HR CTV and intermediate-risk CTV were adequately treated (the percentage of volume treated to ≥100% of the intended dose was >95%) in 70% and 85% of the patients with the conventional plans, respectively, and in 75% and 95% of the patients with the optimized plans, respectively. The minimal dose to the contiguous 2 cm 3 of the rectal, sigmoid, and bladder wall volume was 16 ± 6.2, 25 ± 8.7, and 31 ± 9.2 Gy, respectively. With MRI-guided BT optimization, it was possible to maintain coverage of the HR-CTV and reduce the dose to the normal tissues, especially in patients with small tumors at BT. In these patients, the HR percentage of volume treated to ≥100% of the intended dose approached 100% in all cases, and the minimal dose to the contiguous 2-cm 3 of the rectum, sigmoid, and bladder was 12-32% less than with conventional BT planning. Conclusion: MRI-based BT for cervical cancer has the potential to optimize primary tumor dosimetry and reduce the dose to critical normal tissues, particularly in patients with small tumors.

  4. Evaluation of the liver in normal subjects and cases of hepatic diseases by ultra-low field (0.02 T) magnetic resonance imaging

    International Nuclear Information System (INIS)

    Iwasaki, Yoshie

    1988-01-01

    A total of 123 cases (45 controls, 14 liver cirrhoses, 6 fatty livers, 22 cavernous hemangiomas, 14 hepatomas, 9 metastases, 10 cysts, and 3 hemorrhagic cysts) were studied by ultra-low field magnetic resonance imaging. On T1-weighted images, the means of the intesity ratio in controls were 0.703±0.074 (liver to spleen), 0.658±0.073 (liver to kidney) and 0.932±0.058 (spleen to kidney). On T2-weighted images, the means of the intensity ratios in controls were 0.449±0.083 (liver to spleen), 0.363±0.069 (liver to kidney) and 0.822±0.115 (spleen to kidney). In liver cirrhosis, on T2-weighted images, the intensity ratio of liver to kidney and spleen to kidney. In liver cirrhosis were significantly higher than those in controls. In fatty liver, the intensity ratio of liver to spleen on T1-weighted image, and those of liver to spleen and liver to kidney on T2-weighted image were higher than those in controls. On T2-weighted images, the intensity ratio of tumor to liver in hepatic cavernous hemangioma were significantly higher than those in hepatocellular carcinoma and metastatic liver tumor. Ultra-low field magnetic resonance imaging with the intensity ratio of tumor to liver was valuable in distinguishing between hepatic cavernous hemangioma and hepatic malignancies and it was also possible to distinguish hemorrhagic liver cyst from non-hemorrhagic liver cyst. (author)

  5. Endovascular MR-guided Renal Embolization by Using a Magnetically Assisted Remote-controlled Catheter System.

    Science.gov (United States)

    Lillaney, Prasheel V; Yang, Jeffrey K; Losey, Aaron D; Martin, Alastair J; Cooke, Daniel L; Thorne, Bradford R H; Barry, David C; Chu, Andrew; Stillson, Carol; Do, Loi; Arenson, Ronald L; Saeed, Maythem; Wilson, Mark W; Hetts, Steven W

    2016-10-01

    Purpose To assess the feasibility of a magnetically assisted remote-controlled (MARC) catheter system under magnetic resonance (MR) imaging guidance for performing a simple endovascular procedure (ie, renal artery embolization) in vivo and to compare with x-ray guidance to determine the value of MR imaging guidance and the specific areas where the MARC system can be improved. Materials and Methods In concordance with the Institutional Animal Care and Use Committee protocol, in vivo renal artery navigation and embolization were tested in three farm pigs (mean weight 43 kg ± 2 [standard deviation]) under real-time MR imaging at 1.5 T. The MARC catheter device was constructed by using an intramural copper-braided catheter connected to a laser-lithographed saddle coil at the distal tip. Interventionalists controlled an in-room cart that delivered electrical current to deflect the catheter in the MR imager. Contralateral kidneys were similarly embolized under x-ray guidance by using standard clinical catheters and guidewires. Changes in renal artery flow and perfusion were measured before and after embolization by using velocity-encoded and perfusion MR imaging. Catheter navigation times, renal parenchymal perfusion, and renal artery flow rates were measured for MR-guided and x-ray-guided embolization procedures and are presented as means ± standard deviation in this pilot study. Results Embolization was successful in all six kidneys under both x-ray and MR imaging guidance. Mean catheterization time with MR guidance was 93 seconds ± 56, compared with 60 seconds ± 22 for x-ray guidance. Mean changes in perfusion rates were 4.9 au/sec ± 0.8 versus 4.6 au/sec ± 0.6, and mean changes in renal flow rate were 2.1 mL/min/g ± 0.2 versus 1.9 mL/min/g ± 0.2 with MR imaging and x-ray guidance, respectively. Conclusion The MARC catheter system is feasible for renal artery catheterization and embolization under real-time MR imaging in vivo, and quantitative physiologic

  6. Three-Dimensional Dosimetric Validation of a Magnetic Resonance Guided Intensity Modulated Radiation Therapy System

    Energy Technology Data Exchange (ETDEWEB)

    Rankine, Leith J., E-mail: Leith_Rankine@med.unc.edu [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Department of Radiation Oncology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (United States); Mein, Stewart [Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States); Cai, Bin; Curcuru, Austen [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Juang, Titania; Miles, Devin [Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States); Mutic, Sasa; Wang, Yuhe [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Oldham, Mark [Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States); Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Li, H. Harold, E-mail: hli@radonc.wustl.edu [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States)

    2017-04-01

    Purpose: To validate the dosimetric accuracy of a commercially available magnetic resonance guided intensity modulated radiation therapy (MRgIMRT) system using a hybrid approach: 3-dimensional (3D) measurements and Monte Carlo calculations. Methods and Materials: We used PRESAGE radiochromic plastic dosimeters with remote optical computed tomography readout to perform 3D high-resolution measurements, following a novel remote dosimetry protocol. We followed the intensity modulated radiation therapy commissioning recommendations of American Association of Physicists in Medicine Task Group 119, adapted to incorporate 3D data. Preliminary tests (“AP” and “3D-Bands”) were delivered to 9.5-cm usable diameter cylindrical PRESAGE dosimeters to validate the treatment planning system (TPS) for nonmodulated deliveries; assess the sensitivity, uniformity, and rotational symmetry of the PRESAGE dosimeters; and test the robustness of the remote dosimetry protocol. Following this, 4 clinical MRgIMRT plans (“MultiTarget,” “Prostate,” “Head/Neck,” and “C-Shape”) were measured using 13-cm usable diameter PRESAGE dosimeters. For all plans, 3D-γ (3% or 3 mm global, 10% threshold) passing rates were calculated and 3D-γ maps were examined. Point doses were measured with an IBA-CC01 ionization chamber for validation of absolute dose. Finally, by use of an in-house-developed, GPU-accelerated Monte Carlo algorithm (gPENELOPE), we independently calculated dose for all 6 Task Group 119 plans and compared against the TPS. Results: For PRESAGE measurements, 3D-γ analysis yielded passing rates of 98.7%, 99.2%, 98.5%, 98.0%, 99.2%, and 90.7% for AP, 3D-Bands, MultiTarget, Prostate, Head/Neck, and C-Shape, respectively. Ion chamber measurements were within an average of 0.5% (±1.1%) from the TPS dose. Monte Carlo calculations demonstrated good agreement with the TPS, with a mean 3D-γ passing rate of 98.5% ± 1.9% using a stricter 2%/2-mm criterion. Conclusions: We

  7. Three-Dimensional Dosimetric Validation of a Magnetic Resonance Guided Intensity Modulated Radiation Therapy System

    International Nuclear Information System (INIS)

    Rankine, Leith J.; Mein, Stewart; Cai, Bin; Curcuru, Austen; Juang, Titania; Miles, Devin; Mutic, Sasa; Wang, Yuhe; Oldham, Mark; Li, H. Harold

    2017-01-01

    Purpose: To validate the dosimetric accuracy of a commercially available magnetic resonance guided intensity modulated radiation therapy (MRgIMRT) system using a hybrid approach: 3-dimensional (3D) measurements and Monte Carlo calculations. Methods and Materials: We used PRESAGE radiochromic plastic dosimeters with remote optical computed tomography readout to perform 3D high-resolution measurements, following a novel remote dosimetry protocol. We followed the intensity modulated radiation therapy commissioning recommendations of American Association of Physicists in Medicine Task Group 119, adapted to incorporate 3D data. Preliminary tests (“AP” and “3D-Bands”) were delivered to 9.5-cm usable diameter cylindrical PRESAGE dosimeters to validate the treatment planning system (TPS) for nonmodulated deliveries; assess the sensitivity, uniformity, and rotational symmetry of the PRESAGE dosimeters; and test the robustness of the remote dosimetry protocol. Following this, 4 clinical MRgIMRT plans (“MultiTarget,” “Prostate,” “Head/Neck,” and “C-Shape”) were measured using 13-cm usable diameter PRESAGE dosimeters. For all plans, 3D-γ (3% or 3 mm global, 10% threshold) passing rates were calculated and 3D-γ maps were examined. Point doses were measured with an IBA-CC01 ionization chamber for validation of absolute dose. Finally, by use of an in-house-developed, GPU-accelerated Monte Carlo algorithm (gPENELOPE), we independently calculated dose for all 6 Task Group 119 plans and compared against the TPS. Results: For PRESAGE measurements, 3D-γ analysis yielded passing rates of 98.7%, 99.2%, 98.5%, 98.0%, 99.2%, and 90.7% for AP, 3D-Bands, MultiTarget, Prostate, Head/Neck, and C-Shape, respectively. Ion chamber measurements were within an average of 0.5% (±1.1%) from the TPS dose. Monte Carlo calculations demonstrated good agreement with the TPS, with a mean 3D-γ passing rate of 98.5% ± 1.9% using a stricter 2%/2-mm criterion. Conclusions: We

  8. Transducer project and optimization of the ultra low magnetic field NMR tomograph reception system system; Projeto de transdutores e otimizacao do sistema de recepcao do tomografo de RMN de campo magnetico ultra baixo

    Energy Technology Data Exchange (ETDEWEB)

    Vidoto, Edson Luiz Gea

    1995-12-31

    The aim of the present work was to optimize the signal to noise ratio in our NMR imaging system (TORM 005) by improving transducer`s reception quality through better designed coils, balanced tuning circuit for this coils and power decoupling circuits and by reducing interference from the electromagnetic environment. For this purpose, we had to modify the internal electromagnetic shielding and incorporate line filters in the more critical signals paths. Also, new types of coils were developed, improving the signal to noise ratio, and allowing us to make clinical exams with superior quality for several anatomies. Balanced circuits for tuning and matching of the coil were studied and built, allowing a reduction of the coil losses because patient`s load. This produced a more reliable coil tuning after positioning each new patient. Circuits to avoid the receiver input overload and decoupling circuits for the isolation of receiver coils from excitation coil were designed and incorporated to the TORM 005. All these alterations of our imaging system (TORM 005) contributed to a significant improvement in the signal to noise ratio, reliability and reproducibility of the system. This permitted to operate the system routinely for clinical applications, research and development in the area of ultra low magnetic field tomography. (author) 46 refs., 66 figs., 11 tabs.

  9. Transducer project and optimization of the ultra low magnetic field NMR tomograph reception system system; Projeto de transdutores e otimizacao do sistema de recepcao do tomografo de RMN de campo magnetico ultra baixo

    Energy Technology Data Exchange (ETDEWEB)

    Vidoto, Edson Luiz Gea

    1996-12-31

    The aim of the present work was to optimize the signal to noise ratio in our NMR imaging system (TORM 005) by improving transducer`s reception quality through better designed coils, balanced tuning circuit for this coils and power decoupling circuits and by reducing interference from the electromagnetic environment. For this purpose, we had to modify the internal electromagnetic shielding and incorporate line filters in the more critical signals paths. Also, new types of coils were developed, improving the signal to noise ratio, and allowing us to make clinical exams with superior quality for several anatomies. Balanced circuits for tuning and matching of the coil were studied and built, allowing a reduction of the coil losses because patient`s load. This produced a more reliable coil tuning after positioning each new patient. Circuits to avoid the receiver input overload and decoupling circuits for the isolation of receiver coils from excitation coil were designed and incorporated to the TORM 005. All these alterations of our imaging system (TORM 005) contributed to a significant improvement in the signal to noise ratio, reliability and reproducibility of the system. This permitted to operate the system routinely for clinical applications, research and development in the area of ultra low magnetic field tomography. (author) 46 refs., 66 figs., 11 tabs.

  10. Focal point determination in magnetic resonance-guided focused ultrasound using tracking coils.

    Science.gov (United States)

    Svedin, Bryant T; Beck, Michael J; Hadley, J Rock; Merrill, Robb; de Bever, Joshua T; Bolster, Bradley D; Payne, Allison; Parker, Dennis L

    2017-06-01

    To develop a method for rapid prediction of the geometric focus location in MR coordinates of a focused ultrasound (US) transducer with arbitrary position and orientation without sonicating. Three small tracker coil circuits were designed, constructed, attached to the transducer housing of a breast-specific MR-guided focused US (MRgFUS) system with 5 degrees of freedom, and connected to receiver channel inputs of an MRI scanner. A one-dimensional sequence applied in three orthogonal directions determined the position of each tracker, which was then corrected for gradient nonlinearity. In a calibration step, low-level heating located the US focus in one transducer position orientation where the tracker positions were also known. Subsequent US focus locations were determined from the isometric transformation of the trackers. The accuracy of this method was verified by comparing the tracking coil predictions to thermal center of mass calculated using MR thermometry data acquired at 16 different transducer positions for MRgFUS sonications in a homogeneous gelatin phantom. The tracker coil predicted focus was an average distance of 2.1 ± 1.1 mm from the thermal center of mass. The one-dimensional locator sequence and prediction calculations took less than 1 s to perform. This technique accurately predicts the geometric focus for a transducer with arbitrary position and orientation without sonicating. Magn Reson Med 77:2424-2430, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  11. On-the-fly detection of images with gastritis aspects in magnetically guided capsule endoscopy

    Science.gov (United States)

    Mewes, P. W.; Neumann, D.; Juloski, A. L.; Angelopoulou, E.; Hornegger, J.

    2011-03-01

    Capsule Endoscopy (CE) was introduced in 2000 and has since become an established diagnostic procedure for the small bowel, colon and esophagus. For the CE examination the patient swallows the capsule, which then travels through the gastrointestinal tract under the influence of the peristaltic movements. CE is not indicated for stomach examination, as the capsule movements can not be controlled from the outside and the entire surface of the stomach can not be reliably covered. Magnetically-guided capsule endoscopy (MGCE) was introduced in 2010. For the MGCE procedure the stomach is filled with water and the capsule is navigated from the outside using an external magnetic field. During the examination the operator can control the motion of the capsule in order to obtain a sufficient number of stomach-surface images with diagnostic value. The quality of the examination depends on the skill of the operator and his ability to detect aspects of interest in real time. We present a novel computer-assisted diagnostic-procedure (CADP) algorithm for indicating gastritis pathologies in the stomach during the examination. Our algorithm is based on pre-processing methods and feature vectors that are suitably chosen for the challenges of the MGCE imaging (suspended particles, bubbles, lighting). An image is classified using an ada-boost trained classifier. For the classifier training, a number of possible features were investigated. Statistical evaluation was conducted to identify relevant features with discriminative potential. The proposed algorithm was tested on 12 video sequences stemming from 6 volunteers. A mean detection rate of 91.17% was achieved during leave-one out cross-validation.

  12. The effect of guide-field and boundary conditions on collisionless magnetic reconnection in a stressed X-point collapse

    Energy Technology Data Exchange (ETDEWEB)

    Graf von der Pahlen, J.; Tsiklauri, D. [School of Physics and Astronomy, Queen Mary University of London, London E1 4NS (United Kingdom)

    2014-01-15

    Works of Tsiklauri and Haruki [Phys. Plasmas 15, 102902 (2008); 14, 112905 (2007)] are extended by inclusion of the out-of-plane magnetic (guide) field. In particular, magnetic reconnection during collisionless, stressed X-point collapse for varying out-of-plane guide-fields is studied using a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code. For zero guide-field, cases for both open and closed boundary conditions are investigated, where magnetic flux and particles are lost and conserved, respectively. It is found that reconnection rates, out-of-plane currents and density in the X-point increase more rapidly and peak sooner in the closed boundary case, but higher values are reached in the open boundary case. The normalized reconnection rate is fast: 0.10-0.25. In the open boundary case it is shown that an increase of guide-field yields later onsets in the reconnection peak rates, while in the closed boundary case initial peak rates occur sooner but are suppressed. The reconnection current changes similarly with increasing guide-field; however for low guide-fields the reconnection current increases, giving an optimal value for the guide-field between 0.1 and 0.2 times the in-plane field in both cases. Also, in the open boundary case, it is found that for guide-fields of the order of the in-plane magnetic field, the generation of electron vortices occurs. Possible causes of the vortex generation, based on the flow of decoupled particles in the diffusion region and localized plasma heating, are discussed. Before peak reconnection onset, oscillations in the out-of-plane electric field at the X-point are found, ranging in frequency from approximately 1 to 2 ω{sub pe} and coinciding with oscillatory reconnection. These oscillations are found to be part of a larger wave pattern in the simulation domain. Mapping the out-of-plane electric field along the central lines of the domain over time and applying a 2D Fourier transform reveal that

  13. Analysis of Magnetic Resonance Image Signal Fluctuations Acquired During MR-Guided Radiotherapy.

    Science.gov (United States)

    Breto, Adrian L; Padgett, Kyle R; Ford, John C; Kwon, Deukwoo; Chang, Channing; Fuss, Martin; Stoyanova, Radka; Mellon, Eric A

    2018-03-28

    Magnetic resonance-guided radiotherapy (MRgRT) is a new and evolving treatment modality that allows unprecedented visualization of the tumor and surrounding anatomy. MRgRT includes daily 3D magnetic resonance imaging (MRI) for setup and rapidly repeated near real-time MRI scans during treatment for target tracking. One of the more exciting potential benefits of MRgRT is the ability to analyze serial MRIs to monitor treatment response or predict outcomes. A typical radiation treatment (RT) over the span of 10-15 minutes on the MRIdian system (ViewRay, Cleveland, OH) yields thousands of "cine" images, each acquired in 250 ms. This unique data allows for a glimpse in image intensity changes during RT delivery. In this report, we analyze cine images from a single fraction RT of a glioblastoma patient on the ViewRay platform in order to characterize the dynamic signal changes occurring during RT therapy. The individual frames in the cines were saved into DICOM format and read into an MIM image analysis platform (MIM Software, Cleveland, OH) as a time series. The three possible states of the three Cobalt-60 radiation sources-OFF, READY, and ON-were also recorded. An in-house Java plugin for MIM was created in order to perform principal component analysis (PCA) on each of the datasets. The analysis resulted in first PC, related to monotonous signal increase over the course of the treatment fraction. We found several distortion patterns in the data that we postulate result from the perturbation of the magnetic field due to the moving metal parts in the platform while treatment was being administered. The largest variations were detected when all Cobalt-60 sources were OFF. During this phase of the treatment, the gantry and multi-leaf collimators (MLCs) are moving. Conversely, when all Cobalt-60 sources were in the ON position, the image signal fluctuations were minimal, relating to very little mechanical motion. At this phase, the gantry, the MLCs, and sources are fixed

  14. A proposal to pulse the Bevatron/Bevalac main guide field magnet with SCR power supplies

    International Nuclear Information System (INIS)

    Frias, B.; Alonso, J.; Dwinell, R.; Lothrop, F.

    1989-01-01

    The Bevatron/Bevalac Main Guide Field Power Supply was originally designed to provide a 15,250 Volt DC. at sign 8400 Ampere peak magnet pulse. Protons were accelerated to 6.2 Gev. The 128 Megawatt (MW) pulse required two large motor-generator (MG) sets with 67 ton flywheels to store 680 Megajoules of energy. Ignitron rectifiers are used to rectify the generator outputs. Acceleration of heavy ions results in an operating schedule with a broad range of peak fields. The maximum field of 12.5 kilogauss requires a peak pulse of 80 MW. Acceleration of ions to 1.0 kilogauss requires an 8 MW peak pulse. One MG set can provide pulses below 45 MW. Peak pulses of less than 15 MW are now a large block of the operating schedule. A proposal has been made to replace the existing MG system with eight SCR power supplies for low field operation. The SCR supplies will be powered directly from the Lawrence Berkeley Laboratory's 12.3 KV. power distribution system. This paper describes the many advantages of the plan. 4 refs., 3 figs., 3 tabs

  15. Fluoroscopically-Guided Posterior Approach for Shoulder Magnetic Resonance Arthrography: Comparison with Conventional Anterior Approach

    International Nuclear Information System (INIS)

    Yoo, Koun J.; Ha, Doo Hoe; Lee, Sang Min

    2011-01-01

    To prospectively evaluate the usefulness of the fluoroscopically-guided posterior approach compared with the anterior approach for shoulder magnetic resonance(MR) arthrography. Institutional review board approval and informed consent were obtained. Among 60 shoulder MR arthrographies performed on 59 patients with symptomatic shoulders, an intra-articular injection was performed (30 cases using the anterior approach and 30 using the posterior approach). Procedure-related pain was assessed by using a 5 score visual analogue scale (VAS). Depth of the puncture and standardized depth of puncture by body mass index (BMI) were recorded. The contrast leakage along the course of the puncture was evaluated by reviewing the MR. The statistical analyses included the Mann-Whitney U and Kruskal-Wallis test. There was no significant difference in VAS scores between the anterior and posterior groups (1.77 ± 1.10 vs. 1.80 ± 0.96). Depth of puncture and standardized depth of puncture by BMI were significantly shorter in the posterior group than those in the anterior group (4.4 ± 0.8 cm and 1.8 ± 0.3 cm vs. 6.6 ± 0.9 cm and 2.8 ± 0.4 cm, p < 0.001), respectively. The incidence of contrast leakage was more frequent in the posterior group (p = 0.003). The posterior approach will be useful in shoulder MR arthrography with a suspected anterior pathology, a postoperative follow-up study or obese patient.

  16. Combinatorial programming of human neuronal progenitors using magnetically-guided stoichiometric mRNA delivery.

    Science.gov (United States)

    Azimi, Sayyed M; Sheridan, Steven D; Ghannad-Rezaie, Mostafa; Eimon, Peter M; Yanik, Mehmet Fatih

    2018-05-01

    Identification of optimal transcription-factor expression patterns to direct cellular differentiation along a desired pathway presents significant challenges. We demonstrate massively combinatorial screening of temporally-varying mRNA transcription factors to direct differentiation of neural progenitor cells using a dynamically-reconfigurable magnetically-guided spotting technology for localizing mRNA, enabling experiments on millimetre size spots. In addition, we present a time-interleaved delivery method that dramatically reduces fluctuations in the delivered transcription-factor copy-numbers per cell. We screened combinatorial and temporal delivery of a pool of midbrain-specific transcription factors to augment the generation of dopaminergic neurons. We show that the combinatorial delivery of LMX1A, FOXA2 and PITX3 is highly effective in generating dopaminergic neurons from midbrain progenitors. We show that LMX1A significantly increases TH -expression levels when delivered to neural progenitor cells either during proliferation or after induction of neural differentiation, while FOXA2 and PITX3 increase expression only when delivered prior to induction, demonstrating temporal dependence of factor addition. © 2018, Azimi et al.

  17. Dynamic T2-mapping during magnetic resonance guided high intensity focused ultrasound ablation of bone marrow

    International Nuclear Information System (INIS)

    Waspe, Adam C.; Looi, Thomas; Mougenot, Charles; Amaral, Joao; Temple, Michael; Sivaloganathan, Siv; Drake, James M.

    2012-01-01

    Focal bone tumor treatments include amputation, limb-sparing surgical excision with bone reconstruction, and high-dose external-beam radiation therapy. Magnetic resonance guided high intensity focused ultrasound (MR-HIFU) is an effective non-invasive thermotherapy for palliative management of bone metastases pain. MR thermometry (MRT) measures the proton resonance frequency shift (PRFS) of water molecules and produces accurate ( 2 , since T 2 increases linearly in fat during heating. T 2 -mapping using dual echo times during a dynamic turbo spin-echo pulse sequence enabled rapid measurement of T 2 . Calibration of T 2 -based thermal maps involved heating the marrow in a bovine femur and simultaneously measuring T 2 and temperature with a thermocouple. A positive T 2 temperature dependence in bone marrow of 20 ms/°C was observed. Dynamic T 2 -mapping should enable accurate temperature monitoring during MR-HIFU treatment of bone marrow and shows promise for improving the safety and reducing the invasiveness of pediatric bone tumor treatments.

  18. Nonmagnetic concrete. Guide for the superconductive magnetically levitated train system (Maglev); Hijisei concrete. Chodendo jiki fujoshiki tetsudoyo guide way

    Energy Technology Data Exchange (ETDEWEB)

    Tottori, S; Sato, T [Railway Technical Research Institute, Tokyo (Japan)

    1994-07-01

    Non-magnetization is applied to concrete structures with which magnetic environment is a problem, such as a guideway for superconductive magnetically levitated train system (Maglev) and geomagnetism observation facilities. As an example, this paper introduces the conception and the design methods of guideways for Maglev. If reinforcing bars or tensing materials of common steel are placed close to a vehicle, inductive current is generated in the steel due to moving magnetic field, causing a problem to form part of driving resistance. The inductive current includes loop current and eddy current. The former current may be prevented if the contact resistance in steels with each other is about one ohm or more, but the latter current has no other means but to minimize it as long as the material is electrically conductive. Conceivable measures may include the use as reinforcing bars of non magnetic high Mn-steel with electric specific resistance of 4 to 5 times as large as that for common steel reinforcing bars, and the use of continuous reinforcing fibers such as aramid. The latter material requires strength design especially importantly, but has obtained good result when it was constructed at the experimental linear motor train guideway at Miyazaki, Japan. 5 refs., 6 figs.

  19. Retrospective Analysis of the Accuracy of Ultrasound-Guided Magnetic Resonance Arthrogram Injections of the Hip in the Office Setting.

    Science.gov (United States)

    Jernick, Michael; Walker Gallego, Edward; Nuzzo, Michael

    2017-12-01

    Ultrasound (US)-guided intra-articular hip injections have been proposed in the literature to be accurate, reliable, and safe alternatives to fluoroscopy-guided injections. To evaluate the accuracy of US-guided magnetic resonance (MR) arthrogram injections of the hip performed in the office setting by a single orthopaedic surgeon and elucidate the potential effects that patient age, sex, and body mass index (BMI) have on contrast placement. Case series; Level of evidence, 4. From a review of the senior author's office database, 89 patients (101 hips) who had US-guided MR arthrogram injections performed between December 2014 and June 2016 were identified. Official radiology reports were evaluated to determine whether extra-articular contrast was noted. Patient variables, including BMI, age, and sex, were evaluated between patients who had inappropriately placed contrast and those who did not. Of the 101 hip injections, there were 6 cases that demonstrated inadequate contrast placement within the joint, likely secondary to extravasation or incorrect placement; however, an MR arthrogram was adequately interpreted in all cases. There were no significant differences noted between those with appropriate versus inappropriate contrast placement when evaluating BMI ( P = .57), age ( P = .33), or sex ( P = .67), and neither group had an adverse event. US-guided injections are safe and accurate alternatives to fluoroscopy-guided injections in the office setting, with 94% accuracy. Furthermore, BMI, age, and sex did not play a statistically significant role among patients with inappropriately placed contrast.

  20. Binary system containing the pulsar PSR 1913 + 16 and ultra-violet and x-radiation from accreting magnetic white dwarfs

    International Nuclear Information System (INIS)

    Masters, A.R.

    1978-01-01

    Part I of the thesis deals with the binary system containing the pulsar PSR 1913 + 16. The system has been touted as a laboratory for testing relativistic theories of gravity, and is also a challenge for theories of stellar evolution. However, proposed uses of the system rely on assumptions about the nature of the pulsar's unobserved companion. Ways of determining the nature of the companion from observation of the pulsar are discussed. Geometrical constraints on the size of the pulsar's orbit and the observed slow rate of the orbit's precession require that the companion be a black hole, a neutron star, a white dwarf or a helium main-sequence star. Observable second-order relativistic effects may or may not further restrict the list of candidates. The discussion summarizes Masters and Roberts, 1975 Ap.J. (Letters), 195, L107, and Roberts, Masters and Arnett, 1976, Ap. J., 203, 196. Part II of the thesis treats ultra-violet and X-radiation from accreting magnetic white dwarfs. Matter from a companion star falling onto a white dwarf is shock-heated near the stellar surface and radiatively cooled. The post-shock region is approximated by a uniform, geometrically thin slab and determine the physical conditions behind the shock and the emitted spectrum for a range of stellar masses, magnetic fields and accretion rates. At low magnetic fields and high accretion rates, bremsstrahlung is the dominant cooling mechanism and the post-shock material is a single fluid (the electrons and ions have a common temperature). As the magnetic field increases or the accretion rate decreases, cyclotron emission becomes more important than bremsstrahlung

  1. Large superconducting detector magnets with ultra thin coils for use in high energy accelerators and storage rings

    International Nuclear Information System (INIS)

    Green, M.A.

    1977-08-01

    The development of a new class of large superconducting solenoid magnets is described. High energy physics on colliding beam machines sometimes require the use of thin coil solenoid magnets. The development of these magnets has proceeded with the substitution of light materials for heavy materials and by increasing the current density in the coils. The Lawrence Berkeley Laboratory has developed a radical approach to the problem by having the coil operate at very high current densities. This approach and its implications are described in detail

  2. Magnetic resonance image-guided brachytherapy for cervical cancer. Prognostic factors for survival

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon-Joo; Kim, Joo-Young [National Cancer Center, Proton Therapy Center, Goyang (Korea, Republic of); National Cancer Center, Center for Uterine Cancer, Goyang (Korea, Republic of); Kim, Youngkyong; Lim, Young Kyung; Jeong, Jonghwi [National Cancer Center, Proton Therapy Center, Goyang (Korea, Republic of); Jeong, Chiyoung [National Cancer Center, Proton Therapy Center, Goyang (Korea, Republic of); University of Ulsan College of Medicine, Department of Radiation Oncology, Asan Medical Center, Seoul (Korea, Republic of); Kim, Meyoung [National Cancer Center, Proton Therapy Center, Goyang (Korea, Republic of); Dongnam Inst. of Radiology and Medical Sciences, Research center, Busan (Korea, Republic of); Lim, Myong Cheol; Seo, Sang-Soo; Park, Sang-Yoon [National Cancer Center, Center for Uterine Cancer, Goyang (Korea, Republic of)

    2016-12-15

    The purpose of this work was to identify prognostic factors for survival after magnetic resonance image (MRI)-guided brachytherapy combined with external beam radiotherapy for cervical cancer. External beam radiotherapy of 45-50.4 Gy was delivered by either three-dimensional conformal radiotherapy or helical tomotherapy. Patients also received high-dose-rate MRI-guided brachytherapy of 5 Gy in 6 fractions. We analyzed 128 patients with International Federation of Gynecology and Obstetrics stage IB-IVB cervical cancer who underwent MRI-guided brachytherapy. Most patients (96 %) received concurrent chemotherapy. Pelvic lymph node metastases and para-aortic lymphadenopathies were found in 62 % and 14 % of patients, respectively. The median follow-up time was 44 months. Complete remission was achieved in 119 of 128 patients (93 %). The 5-year local recurrence-free, cancer-specific, and overall survival rates were 94, 89, and 85 %, respectively. Negative pelvic lymphadenopathy, gross tumor volume (GTV) dose covering 90 % of the target (GTV D90) of >110 Gy, and treatment duration ≤56 days were associated with better overall survival in univariate analyses. Multivariable analysis showed that GTV D90 of >110 Gy and treatment duration ≤56 days were possibly associated with overall survival with near-significant P-values of 0.062 and 0.073, respectively. The outcome of MRI-guided brachytherapy combined with external beam radiotherapy in patients with cervical cancer was excellent. GTV D90 of >110 Gy and treatment duration ≤56 days were potentially associated with overall survival. (orig.) [German] Ziel der Arbeit war es, prognostische Faktoren nach magnetresonanztomographisch (MRT-)gesteuerter Brachytherapie in Verbindung mit externer Strahlentherapie fuer Gebaermutterhalskrebs zu identifizieren. Externe Strahlentherapie von 45-50,4 Gy erfolgte entweder mittels dreidimensionaler konformaler Strahlentherapie oder helikaler Tomotherapie. Die Patientinnen erhielten auch

  3. Design and performance of an ultra-high vacuum scanning tunneling microscope operating at dilution refrigerator temperatures and high magnetic fields.

    Science.gov (United States)

    Misra, S; Zhou, B B; Drozdov, I K; Seo, J; Urban, L; Gyenis, A; Kingsley, S C J; Jones, H; Yazdani, A

    2013-10-01

    We describe the construction and performance of a scanning tunneling microscope capable of taking maps of the tunneling density of states with sub-atomic spatial resolution at dilution refrigerator temperatures and high (14 T) magnetic fields. The fully ultra-high vacuum system features visual access to a two-sample microscope stage at the end of a bottom-loading dilution refrigerator, which facilitates the transfer of in situ prepared tips and samples. The two-sample stage enables location of the best area of the sample under study and extends the experiment lifetime. The successful thermal anchoring of the microscope, described in detail, is confirmed through a base temperature reading of 20 mK, along with a measured electron temperature of 250 mK. Atomically resolved images, along with complementary vibration measurements, are presented to confirm the effectiveness of the vibration isolation scheme in this instrument. Finally, we demonstrate that the microscope is capable of the same level of performance as typical machines with more modest refrigeration by measuring spectroscopic maps at base temperature both at zero field and in an applied magnetic field.

  4. Magnetic matrix solid phase dispersion assisted dispersive liquid liquid microextraction of ultra trace polychlorinated biphenyls in water prior to GC-ECD determination

    International Nuclear Information System (INIS)

    Diao, Chunpeng; Li, Cong; Yang, Xiao; Sun, Ailing; Liu, Renmin

    2016-01-01

    Magnetic matrix solid phase dispersion (MMSPD) assisted dispersive liquid liquid microextraction (DLLME) was applied to extract ultra traces of polychlorinated biphenyls (PCBs) from water samples prior to gas chromatography with electron capture detection. PCBs in water were adsorbed by micro particles of magnetic bamboo charcoal and then transferred into the elution solvent. PCBs in the elution solvent of the MMSPD were further concentrated into trace volume extraction solvent of the DLLME procedure. Under optimized conditions, good linearity in the range of 0.2–100 ng L"−"1 was obtained with regression coefficients (r) higher than 0.9987. Based on a signal-noise ratio of 3, the limits of detection (LODs) range from 0.05–0.1 ng L"−"1. These LODs are much lower than those of MMSPD or DLLME alone. Relative standard deviations are between 4.9–8.2 %. The method was successfully applied to the determination of PCBs in lake and river water. Relative recoveries were 85.5–117.4 % for the spiked environmental water samples. (author)

  5. Polyethylene glycol-covered ultra-small Gd2O3 nanoparticles for positive contrast at 1.5 T magnetic resonance clinical scanning

    Science.gov (United States)

    Fortin, Marc-André; Petoral, Rodrigo M., Jr.; Söderlind, Fredrik; Klasson, A.; Engström, Maria; Veres, Teodor; Käll, Per-Olof; Uvdal, Kajsa

    2007-10-01

    The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd2O3) were studied, and the impact of polyethylene glycol capping on the relaxivity constants (r1, r2) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd2O3 nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd2O3 nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd3+ and surfactants. The particle hydrodynamic radius was measured with dynamic light scattering (DLS) and the proton relaxation times were measured with a 1.5 T MRI scanner. Parallel studies were performed with DEG-Gd2O3 and PEG-silane-SPGO (Gd2O3,DTPA and the r2/r1 ratio was 1.4. PEG-silane-SPGO gave low r1 relaxivities and high r2/r1 ratios, less compatible with positive contrast agent requirements. Higher r1 were obtained with PEG-silane in comparison to DEG-Gd2O3. Treatment of DEG-US-Gd2O3 with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd2O3 nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.

  6. Application of SQUIDs to low temperature and high magnetic field measurements—Ultra low noise torque magnetometry

    Science.gov (United States)

    Arnold, F.; Naumann, M.; Lühmann, Th.; Mackenzie, A. P.; Hassinger, E.

    2018-02-01

    Torque magnetometry is a key method to measure the magnetic anisotropy and quantum oscillations in metals. In order to resolve quantum oscillations in sub-millimeter sized samples, piezo-electric micro-cantilevers were introduced. In the case of strongly correlated metals with large Fermi surfaces and high cyclotron masses, magnetic torque resolving powers in excess of 104 are required at temperatures well below 1 K and magnetic fields beyond 10 T. Here, we present a new broadband read-out scheme for piezo-electric micro-cantilevers via Wheatstone-type resistance measurements in magnetic fields up to 15 T and temperatures down to 200 mK. By using a two-stage superconducting-quantum interference device as a null detector of a cold Wheatstone bridge, we were able to achieve a magnetic moment resolution of Δm = 4 × 10-15 J/T at maximal field and 700 mK, outperforming conventional magnetometers by at least one order of magnitude in this temperature and magnetic field range. Exemplary de Haas-van Alphen measurement of a newly grown delafossite, PdRhO2, was used to show the superior performance of our setup.

  7. The influence of bias magnetization of nanoparticles on GMR sensor signal and sensitivity for the ultra-low concentration detection

    Science.gov (United States)

    Zhang, Yang; Xu, Jie; Cao, Derang; Li, Qiang; Zhao, Guoxia; Sun, Nian X.; Li, Shandong

    2018-05-01

    In the broad research of the GMR bio-sensing technology, it is vital to explore appropriate magnetic labels and its influences on the detection signal. In this work, four kinds of ferrite particles of γ-Fe2O3, CoFe2O4, NiFe2O4 and NiZnFe2O4 were prepared through calcining the Dimethyl Formamide (DMF) solution of the transition metal nitrates [Fe(NO3)3 and X(NO3)2, X = Co, Ni, Zn] to study the effect of magnetic properties on detection signals using a DC in-plane measuring method. It was revealed that for four particles, the output voltage differences |ΔV| between with and without magnetic particles exhibit log-linear functions of the particles concentrations x in the range from 0.1 to 10 ng/mL. A very low limitation of detection (LOD) of 0.1 ng/mL for all the samples was obtained, which is two orders smaller than that in the previous work. Moreover, the change of output voltage difference at the LOD (|ΔVlim|) is proportional to the magnetization at bias field (bias magnetization, Mbias), which indicates that larger Mbias leads to a lower LOD. This work provides a useful guidance in selecting or preparing magnetic labels to enhance the sensitivity of GMR biosensors.

  8. Efficacy of Magnetic Resonance-guided Focused Ultrasound Surgery for Bone Metastases Pain Palliation

    Science.gov (United States)

    Kawasaki, Motohiro; Nanba, Hirofumi; Kato, Tomonari; Tani, Toshikazu; Ushida, Takahiro

    2011-09-01

    Magnetic resonance-guided focused ultrasound surgery (MRgFUS) is a novel treatment method that achieves non-invasive thermal ablation by focusing many ultrasound waves on a target tissue with real-time monitoring of the location and temperature of the target during the procedure. We investigated the palliative effect on pain and safety of MRgFUS in painful bone metastases. Six patients (mean age, 65.8 years) who met eligibility criteria for the clinical study approved by our Institutional Ethics Committee based on the cooperative protocol were treated with MRgFUS. Targeted sites included the sacrum (n = 1), ilium (n = 2), scapula (n = 2), and femur (n = 1). The mean follow-up period was 9.2 months. All procedures were performed as a single-session treatment using the treatment system that is integrated into the patient table of a magnetic resonance image (MRI) scanner. Endpoints were change in the intensity of pain due to bone metastases from before to after the treatment, as measured on a numerical rating scale, pain interference with daily activities as determined by the Brief pain inventory (BPI), change in images, and safety. Pain relief was obtained in all patients early after treatment, with a reduction in the mean pain score from 6.0±1.3 at baseline to 1.2±1.0 at the end of follow-up as well as in pain interference with daily activities. The mean time required for a single-session treatment was 83.7±37.0 min, with a mean number of sonications required of 13.3±3.7 and mean energy applied of 846.4±273.5 J. No significant growth of tumors was observed, nor were there treatment-related adverse events. These results suggest that MRgFUS has a non-invasive palliative effect on the localized pain in patients with bone metastasis. MRgFUS could become an option in treatment strategies for painful bone metastases in the future.

  9. Open-source, small-animal magnetic resonance-guided focused ultrasound system.

    Science.gov (United States)

    Poorman, Megan E; Chaplin, Vandiver L; Wilkens, Ken; Dockery, Mary D; Giorgio, Todd D; Grissom, William A; Caskey, Charles F

    2016-01-01

    MR-guided focused ultrasound or high-intensity focused ultrasound (MRgFUS/MRgHIFU) is a non-invasive therapeutic modality with many potential applications in areas such as cancer therapy, drug delivery, and blood-brain barrier opening. However, the large financial costs involved in developing preclinical MRgFUS systems represent a barrier to research groups interested in developing new techniques and applications. We aim to mitigate these challenges by detailing a validated, open-source preclinical MRgFUS system capable of delivering thermal and mechanical FUS in a quantifiable and repeatable manner under real-time MRI guidance. A hardware and software package was developed that includes closed-loop feedback controlled thermometry code and CAD drawings for a therapy table designed for a preclinical MRI scanner. For thermal treatments, the modular software uses a proportional integral derivative controller to maintain a precise focal temperature rise in the target given input from MR phase images obtained concurrently. The software computes the required voltage output and transmits it to a FUS transducer that is embedded in the delivery table within the magnet bore. The delivery table holds the FUS transducer, a small animal and its monitoring equipment, and a transmit/receive RF coil. The transducer is coupled to the animal via a water bath and is translatable in two dimensions from outside the magnet. The transducer is driven by a waveform generator and amplifier controlled by real-time software in Matlab. MR acoustic radiation force imaging is also implemented to confirm the position of the focus for mechanical and thermal treatments. The system was validated in tissue-mimicking phantoms and in vivo during murine tumor hyperthermia treatments. Sonications were successfully controlled over a range of temperatures and thermal doses for up to 20 min with minimal temperature overshoot. MR thermometry was validated with an optical temperature probe, and focus

  10. Ultra-High Field NMR and MRI—The Role of Magnet Technology to Increase Sensitivity and Specificity

    Directory of Open Access Journals (Sweden)

    Ewald Moser

    2017-08-01

    Full Text Available “History, of course, is difficult to write, if for no other reason, than that it has so many players and so many authors.” – P. J. Keating (former Australian Prime MinisterStarting with post-war developments in nuclear magnetic resonance (NMR a race for stronger and stronger magnetic fields has begun in the 1950s to overcome the inherently low sensitivity of this promising method. Further challenges were larger magnet bores to accommodate small animals and eventually humans. Initially, resistive electromagnets with small pole distances, or sample volumes, and field strengths up to 2.35 T (or 100 MHz 1H frequency were used in applications in physics, chemistry, and material science. This was followed by stronger and more stable (Nb-Ti based superconducting magnet technology typically implemented first for small-bore systems in analytical chemistry, biochemistry and structural biology, and eventually allowing larger horizontal-bore magnets with diameters large enough to fit small laboratory animals. By the end of the 1970s, first low-field resistive magnets big enough to accommodate humans were developed and superconducting whole-body systems followed. Currently, cutting-edge analytical NMR systems are available at proton frequencies up to 1 GHz (23.5 T based on Nb3Sn at 1.9 K. A new 1.2 GHz system (28 T at 1.9 K, operating in persistent mode but using a combination of low and high temperature multi-filament superconductors is to be released. Preclinical instruments range from small-bore animal systems with typically 600–800 MHz (14.1–18.8 T up to 900 MHz (21 T at 1.9 K. Human whole-body MRI systems currently operate up to 10.5 T. Hybrid combined superconducting and resistive electromagnets with even higher field strength of 45 T dc and 100 T pulsed, are available for material research, of course with smaller free bore diameters. This rather costly development toward higher and higher field strength is a consequence of the inherently low

  11. Magnetic resonance imaging-guided focused ultrasound ablation of uterine fibroids. Early clinical experience

    International Nuclear Information System (INIS)

    Mikami, Koji; Osuga, Keigo; Tomoda, Kaname; Nakamura, Hironobu; Murakami, Takamichi; Okada, Atsuya

    2008-01-01

    The aim of this study was to assess the feasibility and effectiveness of magnetic resonance (MRI)-guided focused ultrasound (MRIgFUS) ablation for uterine fibroids and to identify the candidates for this treatment. A total of 48 patients with a symptomatic uterine fibroid underwent MRIgFUS. The percent ablation volume was calculated, and the patients' characteristics and the MR imaging features of the fibroids that might predict the effect of this treatment were assessed. Changes in the symptoms related to the uterine fibroid were assessed at 6 and 12 months. The planned target zone were successfully treated in 32 patients with bulk-related and menstrual symptoms but unsuccessfully treated in the remaining 16 patients. These 16 patients were obese or their uterine fibroid showed heterogeneous high signal intensity on T2-weighted images. The 32 successfully treated patients were followed up for 6 months. At the 6-month follow-up, bulk-related and menstrual symptoms were diminished in 60% and 51% of patients, respectively. Among them, 17 patients were followed up for 12 months, and 9 of them who showed alleviation of bulk-related symptoms at 6 months had further improvement. The mean percent ablation volume of those nine patients was 51%. In 5 (33%) of the 15 patients with alleviation of menstrual symptoms at 6 months, the symptoms became worse at 12 months. There was a significant difference in the mean percent ablation volume between patients with alleviation of menstrual symptoms and those without (54% vs. 37%; P=0.03). MRIgFUS ablation is a safe, effective treatment for nonobese patients with symptomatic fibroids that show low signal intensity on T2-weighted images. Ablation of more than 50% of the fibroid volume may be needed with a short-term follow-up. (author)

  12. Ultra-small v-shaped gold split ring resonators for biosensing using fundamental magnetic resonance in the visible spectrum

    Science.gov (United States)

    Mauluidy Soehartono, Alana; Mueller, Aaron David; Tobing, Landobasa Yosef Mario; Chan, Kok Ken; Zhang, Dao Hua; Yong, Ken-Tye

    2017-10-01

    Strong light localization within metal nanostructures occurs by collective oscillations of plasmons in the form of electric and magnetic resonances. This so-called localized surface plasmon resonance (LSPR) has gained much interest in the development of low-cost sensing platforms in the visible spectrum. However, demonstrations of LSPR-based sensing are mostly limited to electric resonances due to the technological limitations for achieving magnetic resonances in the visible spectrum. In this work, we report the first demonstration of LSPR sensing based on fundamental magnetic resonance in the visible spectrum using ultrasmall gold v-shaped split ring resonators. Specifically, we show the ability for detecting adsorption of bovine serum albumin and cytochrome c biomolecules at monolayer levels, and the selective binding of protein A/G to immunoglobulin G.

  13. Ultra-soft magnetic Co-Fe-B-Si-Nb amorphous alloys for high frequency power applications

    Science.gov (United States)

    Ackland, Karl; Masood, Ansar; Kulkarni, Santosh; Stamenov, Plamen

    2018-05-01

    With the continuous shrinkage of the footprint of inductors and transformers in modern power supplies, higher flux, while still low-loss metallic replacements of traditional ferrite materials are becoming an intriguing alternative. One candidate replacement strategy is based on amorphous CoFeBSi soft-magnetic alloys, in their metallic glass form. Here the structural and magnetic properties of two different families of CoFeBSi-based soft magnetic alloys, prepared by arc-melting and subsequent melt spinning (rapid quenching) are presented, targeting potential applications at effective frequencies of 100 kHz and beyond. The nominal alloy compositions are Co67Fe4B11Si16Mo2 representing commercial Vitrovac and Co72-xFexB28-y (where B includes non-magnetic elements such as Boron, Silicon etc. x varies between 4 and 5 % and y is varied from 0 to 2 %) denoted Alloy #1 and prepared as a possible higher performance alternative, i.e. lower power loss and lower coercivity, to commercial Vitrovac. Room temperature magnetization measurements of the arc-melted alloys reveal that compared to Vitrovac, Alloy #1 already presents a ten-fold decrease in coercivity, with Hc ˜ 1.4 Am-1 and highest figure of merit of (Ms/Hc > 96). Upon melt-spinning the alloys into thin (< 30 μm) ribbons, the alloys are essentially amorphous when analyzed by XRD. Magnetization measurements of the melt-spun ribbons demonstrate that Alloy #1 possesses a coercivity of just 2 Am-1, which represents a significant improvement compared to melt-spun ribbons of Vitrovac (17 Am-1). A set of prototype transformers of approximately 10 turns of Alloy #1 ribbon exhibits systematically Hc < 10 Am-1 at 100 kHz, without a noticeable decrease in coupled flux and saturation.

  14. Pure-iron/iron-based-alloy hybrid soft magnetic powder cores compacted at ultra-high pressure

    Science.gov (United States)

    Saito, Tatsuya; Tsuruta, Hijiri; Watanabe, Asako; Ishimine, Tomoyuki; Ueno, Tomoyuki

    2018-04-01

    We developed Fe/FeSiAl soft magnetic powder cores (SMCs) for realizing the miniaturization and high efficiency of an electromagnetic conversion coil in the high-frequency range (˜20 kHz). We found that Fe/FeSiAl SMCs can be formed with a higher density under higher compaction pressure than pure-iron SMCs. These SMCs delivered a saturation magnetic flux density of 1.7 T and iron loss (W1/20k) of 158 kW/m3. The proposed SMCs exhibited similar excellent characteristics even in block shapes, which are closer to the product shapes.

  15. Pure-iron/iron-based-alloy hybrid soft magnetic powder cores compacted at ultra-high pressure

    Directory of Open Access Journals (Sweden)

    Tatsuya Saito

    2018-04-01

    Full Text Available We developed Fe/FeSiAl soft magnetic powder cores (SMCs for realizing the miniaturization and high efficiency of an electromagnetic conversion coil in the high-frequency range (∼20 kHz. We found that Fe/FeSiAl SMCs can be formed with a higher density under higher compaction pressure than pure-iron SMCs. These SMCs delivered a saturation magnetic flux density of 1.7 T and iron loss (W1/20k of 158 kW/m3. The proposed SMCs exhibited similar excellent characteristics even in block shapes, which are closer to the product shapes.

  16. Magnetic Nickel iron Electroformed Trap (MagNET): a master/replica fabrication strategy for ultra-high throughput (>100 mL h−1) immunomagnetic sorting†

    Science.gov (United States)

    Ko, Jina; Yelleswarapu, Venkata; Singh, Anup; Shah, Nishal

    2016-01-01

    Microfluidic devices can sort immunomagnetically labeled cells with sensitivity and specificity much greater than that of conventional methods, primarily because the size of microfluidic channels and micro-scale magnets can be matched to that of individual cells. However, these small feature sizes come at the expense of limited throughput (ϕ 10 mL whole blood. Here, we report a new approach to micromagnetic sorting that can achieve highly specific cell separation in unprocessed complex samples at a throughput (ϕ > 100 mL h−1) 100× greater than that of conventional microfluidics. To achieve this goal, we have devised a new approach to micromagnetic sorting, the magnetic nickel iron electroformed trap (MagNET), which enables high flow rates by having millions of micromagnetic traps operate in parallel. Our design rotates the conventional microfluidic approach by 90° to form magnetic traps at the edges of pores instead of in channels, enabling millions of the magnetic traps to be incorporated into a centimeter sized device. Unlike previous work, where magnetic structures were defined using conventional microfabrication, we take inspiration from soft lithography and create a master from which many replica electroformed magnetic micropore devices can be economically manufactured. These free-standing 12 µm thick permalloy (Ni80Fe20) films contain micropores of arbitrary shape and position, allowing the device to be tailored for maximal capture efficiency and throughput. We demonstrate MagNET's capabilities by fabricating devices with both circular and rectangular pores and use these devices to rapidly (ϕ = 180 mL h−1) and specifically sort rare tumor cells from white blood cells. PMID:27170379

  17. T2-Weighted 4D Magnetic Resonance Imaging for Application in Magnetic Resonance–Guided Radiotherapy Treatment Planning

    Science.gov (United States)

    Freedman, Joshua N.; Collins, David J.; Bainbridge, Hannah; Rank, Christopher M.; Nill, Simeon; Kachelrieß, Marc; Oelfke, Uwe; Leach, Martin O.; Wetscherek, Andreas

    2017-01-01

    Objectives The aim of this study was to develop and verify a method to obtain good temporal resolution T2-weighted 4-dimensional (4D-T2w) magnetic resonance imaging (MRI) by using motion information from T1-weighted 4D (4D-T1w) MRI, to support treatment planning in MR-guided radiotherapy. Materials and Methods Ten patients with primary non–small cell lung cancer were scanned at 1.5 T axially with a volumetric T2-weighted turbo spin echo sequence gated to exhalation and a volumetric T1-weighted stack-of-stars spoiled gradient echo sequence with golden angle spacing acquired in free breathing. From the latter, 20 respiratory phases were reconstructed using the recently developed 4D joint MoCo-HDTV algorithm based on the self-gating signal obtained from the k-space center. Motion vector fields describing the respiratory cycle were obtained by deformable image registration between the respiratory phases and projected onto the T2-weighted image volume. The resulting 4D-T2w volumes were verified against the 4D-T1w volumes: an edge-detection method was used to measure the diaphragm positions; the locations of anatomical landmarks delineated by a radiation oncologist were compared and normalized mutual information was calculated to evaluate volumetric image similarity. Results High-resolution 4D-T2w MRI was obtained. Respiratory motion was preserved on calculated 4D-T2w MRI, with median diaphragm positions being consistent with less than 6.6 mm (2 voxels) for all patients and less than 3.3 mm (1 voxel) for 9 of 10 patients. Geometrical positions were coherent between 4D-T1w and 4D-T2w MRI as Euclidean distances between all corresponding anatomical landmarks agreed to within 7.6 mm (Euclidean distance of 2 voxels) and were below 3.8 mm (Euclidean distance of 1 voxel) for 355 of 470 pairs of anatomical landmarks. Volumetric image similarity was commensurate between 4D-T1w and 4D-T2w MRI, as mean percentage differences in normalized mutual information (calculated over all

  18. T2-Weighted 4D Magnetic Resonance Imaging for Application in Magnetic Resonance-Guided Radiotherapy Treatment Planning.

    Science.gov (United States)

    Freedman, Joshua N; Collins, David J; Bainbridge, Hannah; Rank, Christopher M; Nill, Simeon; Kachelrieß, Marc; Oelfke, Uwe; Leach, Martin O; Wetscherek, Andreas

    2017-10-01

    The aim of this study was to develop and verify a method to obtain good temporal resolution T2-weighted 4-dimensional (4D-T2w) magnetic resonance imaging (MRI) by using motion information from T1-weighted 4D (4D-T1w) MRI, to support treatment planning in MR-guided radiotherapy. Ten patients with primary non-small cell lung cancer were scanned at 1.5 T axially with a volumetric T2-weighted turbo spin echo sequence gated to exhalation and a volumetric T1-weighted stack-of-stars spoiled gradient echo sequence with golden angle spacing acquired in free breathing. From the latter, 20 respiratory phases were reconstructed using the recently developed 4D joint MoCo-HDTV algorithm based on the self-gating signal obtained from the k-space center. Motion vector fields describing the respiratory cycle were obtained by deformable image registration between the respiratory phases and projected onto the T2-weighted image volume. The resulting 4D-T2w volumes were verified against the 4D-T1w volumes: an edge-detection method was used to measure the diaphragm positions; the locations of anatomical landmarks delineated by a radiation oncologist were compared and normalized mutual information was calculated to evaluate volumetric image similarity. High-resolution 4D-T2w MRI was obtained. Respiratory motion was preserved on calculated 4D-T2w MRI, with median diaphragm positions being consistent with less than 6.6 mm (2 voxels) for all patients and less than 3.3 mm (1 voxel) for 9 of 10 patients. Geometrical positions were coherent between 4D-T1w and 4D-T2w MRI as Euclidean distances between all corresponding anatomical landmarks agreed to within 7.6 mm (Euclidean distance of 2 voxels) and were below 3.8 mm (Euclidean distance of 1 voxel) for 355 of 470 pairs of anatomical landmarks. Volumetric image similarity was commensurate between 4D-T1w and 4D-T2w MRI, as mean percentage differences in normalized mutual information (calculated over all respiratory phases and patients), between

  19. Cooperative photo-induced effects: from photo-magnetism under continuous irradiation to ultra-fast phenomena - study through optical spectroscopy and X-ray diffraction

    International Nuclear Information System (INIS)

    Glijer, D.

    2006-12-01

    The control with ultra-short laser pulses of the collective and concerted transformation of molecules driving a macroscopic state switching on an ultra-fast time scale in solid state opens new prospects in materials science. The goal is to realize at the material level what happens at the molecular level in femto-chemistry. These processes are highly cooperative and highly non-linear, leading to self-amplification and self-organization within the material, a so-called photo-induced phase transition with a new long range order (structural, magnetic, ferroelectric,...). Two families of molecular compounds have been studied here: first of all, spin transition materials changing from a diamagnetic state over to a paramagnetic state under the effect of temperature or under continuous laser excitation. It concerns photo-active molecular bi-stability prototype materials in solid state, whose switching has been studied during X-ray diffraction, optical reflectivity and magnetism experiments. Then we have studied charge-transfer molecular systems, prototype compounds for ultrafast photo-induced phase transitions: insulator-metal, neutral-ionic....As well as ultrafast optical experiments, time-resolved X ray crystallography is a key technique in order to follow at the atomic level the different steps of the photo-induced transformation and thus to observe the involved mechanisms. We have underlined a process of photo-formation of one-dimensional nano-domains of lattice-relaxed charge-transfer excitations, governing the photo-induced phase transition of the molecular charge-transfer complex TTF-CA by the first time-resolved diffuse scattering measurements. Moreover, a new femtosecond laser-plasma source and a optical pump-probe spectroscopy set-up with a highly sensitive detecting system have been developed in this work. The results presented here will be an illustration of the present scientific challenges existing on the one hand with the development of projects of major

  20. Ultra-high field NMR and MRI - the role of magnet technology to increase sensitivity and specificity

    Science.gov (United States)

    Moser, Ewald; Laistler, Elmar; Schmitt, Franz; Kontaxis, Georg

    2017-08-01

    "History, of course, is difficult to write, if for no other reason, than that it has so many players and so many authors." - P. J. Keating (former Australian Prime Minister) Starting with post-war developments in nuclear magnetic resonance (NMR) a race for stronger and stronger magnetic fields has begun in the 1950s to overcome the inherently low sensitivity of this promising method. Further challenges were larger magnet bores to accommodate small animals and eventually humans. Initially, resistive electromagnets with small pole distances, or sample volumes, and field strengths up to 2.35 T (or 100 MHz 1H frequency) were used in applications in physics, chemistry, and material science. This was followed by stronger and more stable (NbTi based) superconducting magnet technology typically implemented first for small-bore systems in analytical chemistry, biochemistry and structural biology, and eventually allowing larger horizontal-bore magnets with diameters large enough to fit small laboratory animals. By the end of the 1970s, first low-field resistive magnets big enough to accommodate humans were developed and superconducting whole-body systems followed. Currently, cutting-edge analytical NMR systems are available at proton frequencies up to 1 GHz (23.5 T) based on Nb3Sn at 1.9 K. A new 1.2 GHz system (28 T) at 1.9 K, operating in persistent mode but using a combination of low and high temperature multi-filament superconductors is to be released. Preclinical instruments range from small-bore animal systems with typically 600 - 800 MHz (14.1 - 18.8 T) up to 900 MHz (21 T) at 1.9 K. Human whole-body MRI systems currently operate up to 10.5 T. Hybrid combined superconducting and resistive electromagnets with even higher field strength of 45 T dc and 100 T pulsed, are available for material research, of course with smaller free bore diameters. This rather costly development towards higher and higher field strength is a consequence of the inherently low and, thus

  1. Fluorescence and Magnetic Resonance Dual-Modality Imaging-Guided Photothermal and Photodynamic Dual-Therapy with Magnetic Porphyrin-Metal Organic Framework Nanocomposites

    Science.gov (United States)

    Zhang, Hui; Li, Yu-Hao; Chen, Yang; Wang, Man-Man; Wang, Xue-Sheng; Yin, Xue-Bo

    2017-03-01

    Phototherapy shows some unique advantages in clinical application, such as remote controllability, improved selectivity, and low bio-toxicity, than chemotherapy. In order to improve the safety and therapeutic efficacy, imaging-guided therapy seems particularly important because it integrates visible information to speculate the distribution and metabolism of the probe. Here we prepare biocompatible core-shell nanocomposites for dual-modality imaging-guided photothermal and photodynamic dual-therapy by the in situ growth of porphyrin-metal organic framework (PMOF) on Fe3O4@C core. Fe3O4@C core was used as T2-weighted magnetic resonance (MR) imaging and photothermal therapy (PTT) agent. The optical properties of porphyrin were well remained in PMOF, and PMOF was therefore selected for photodynamic therapy (PDT) and fluorescence imaging. Fluorescence and MR dual-modality imaging-guided PTT and PDT dual-therapy was confirmed with tumour-bearing mice as model. The high tumour accumulation of Fe3O4@C@PMOF and controllable light excitation at the tumour site achieved efficient cancer therapy, but low toxicity was observed to the normal tissues. The results demonstrated that Fe3O4@C@PMOF was a promising dual-imaging guided PTT and PDT dual-therapy platform for tumour diagnosis and treatment with low cytotoxicity and negligible in vivo toxicity.

  2. Microelectrode Recording-Guided Versus Intraoperative Magnetic Resonance Imaging-Guided Subthalamic Nucleus Deep Brain Stimulation Surgery for Parkinson Disease: A 1-Year Follow-Up Study.

    Science.gov (United States)

    Liu, Xuemeng; Zhang, Jibo; Fu, Kai; Gong, Rui; Chen, Jincao; Zhang, Jie

    2017-11-01

    Microelectrode recording (MER) and intraoperative magnetic resonance imaging (iMRI) have been used in deep brain stimulation surgery for Parkinson disease (PD), but comparative methodology is lacking. Therefore, we compared the 1-year follow-up outcomes of MER-guided and iMRI-guided subthalamic nucleus (STN) deep brain stimulation (DBS) surgery in PD patients. We conducted a review comparing PD patients who underwent MER-guided (n = 76, group A) and iMRI-guided STN DBS surgery (n = 61, group B) in our institution. Pre- and postoperative assessments included Unified Parkinson's Disease Rating Scale-III (UPDRS-III) score, Parkinson's Disease Questionnaire (PDQ-39), Mini-Mental State Examination (MMSE), levodopa equivalent daily doses (LEDDs), and magnetic resonance images. The mean magnitudes of electrode discrepancy were x = 1.1 ± 0.2 mm, y = 1.3 ± 0.3 mm, and z = 2.1 ± 0.5 mm in group A and x = 1.3 ± 0.4 mm, y = 1.2 ± 0.2 mm, and z = 2.5 ± 0.7 mm in group B. Significant differences were not found between 2 groups for x, y, or z (P = 0.34, P = 0.26, and P = 0.41, respectively). At 1 year, when levodopa was withdrawn for 12 hours, the UPDRS-III score improved by 66.3% ± 13.5% in group A and 64.8% ± 12.7% in group B (P = 0.24); the PDQ-39 summary index score improved by 49.7% ± 14.3% in group A and 44.1% ± 12.7% in group B (P = 0.16); the MMSE score improved by 4.2% ± 2.1% in group A and 11.1% ± 3.2% in group B (P = 0.43); and LEDDs decreased by 48.7% ± 10.1% in group A and 56.9% ± 12.0% in group B (P = 0.32). MER and iMRI both are effective ways to ensure adequate electrode placement in DBS surgery, but there is no superiority between both techniques, at least in terms of 1-year follow-up outcomes. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Role of oxygen defects on the magnetic properties of ultra-small Sn1-xFexO2 nanoparticles

    Science.gov (United States)

    Dodge, Kelsey; Chess, Jordan; Eixenberger, Josh; Alanko, Gordon; Hanna, Charles B.; Punnoose, Alex

    2013-05-01

    Although the role of oxygen defects in the magnetism of metal oxide semiconductors has been widely discussed, it is been difficult to directly measure the oxygen defect concentration of samples to verify this. This work demonstrates a direct correlation between the photocatalytic activity of Sn1-xFexO2 nanoparticles and their magnetic properties. For this, a series of ˜2.6 nm sized, well characterized, single-phase Sn1-xFexO2 crystallites with x = 0-0.20 were synthesized using tin acetate, urea, and appropriate amounts of iron acetate. X-ray photoelectron spectroscopy confirmed the concentration and 3+ oxidation state of the doped Fe ions. The maximum magnetic moment/Fe ion, μ, of 1.6 × 10-4 μB observed for the 0.1% Fe doped sample is smaller than the expected spin-only contribution from either high or low spin Fe3+ ions, and μ decreases with increasing Fe concentration. This behavior cannot be explained by the existing models of magnetic exchange. Photocatalytic studies of pure and Fe-doped SnO2 were used to understand the roles of doped Fe3+ ions and of the oxygen vacancies and defects. The photocatalytic rate constant k also showed an increase when SnO2 nanoparticles were doped with low concentrations of Fe3+, reaching a maximum at 0.1% Fe, followed by a rapid decrease of k for further increase in Fe%. Fe doping presumably increases the concentration of oxygen vacancies, and both Fe3+ ions and oxygen vacancies act as electron acceptors to reduce e--h+ recombination and promote transfer of electrons (and/or holes) to the nanoparticle surface, where they participate in redox reactions. This electron transfer from the Fe3+ ions to local defect density of states at the nanoparticle surface could develop a magnetic moment at the surface states and leads to spontaneous ferromagnetic ordering of the surface shell under favorable conditions. However, at higher doping levels, the same Fe3+ ions might act as recombination centers causing a decrease of both k and

  4. Preoperative Navigated Transcranial Magnetic Stimulation and Tractography to Guide Endoscopic Cystoventriculostomy: A Technical Note and Case Report.

    Science.gov (United States)

    Hendrix, Philipp; Senger, Sebastian; Griessenauer, Christoph J; Simgen, Andreas; Linsler, Stefan; Oertel, Joachim

    2018-01-01

    To report a technique for endoscopic cystoventriculostomy guided by preoperative navigated transcranial magnetic stimulation (nTMS) and tractography in a patient with a large speech eloquent arachnoid cyst. A 74-year old woman presented with a seizure and subsequent persistent anomic aphasia from a progressive left-sided parietal arachnoid cyst. An endoscopic cystoventriculostomy and endoscope-assisted ventricle catheter placement were performed. Surgery was guided by preoperative nTMS and tractography to avoid eloquent language, motor, and visual pathways. Preoperative nTMS motor and language mapping were used to guide tractography of motor and language white matter tracts. The ideal locations of entry point and cystoventriculostomy as well as trajectory for stent-placement were determined preoperatively with a pseudo-3-dimensional model visualizing eloquent language, motor, and visual cortical and subcortical information. The early postoperative course was uneventful. At her 3-month follow-up visit, her language impairments had completely recovered. Additionally, magnetic resonance imaging demonstrated complete collapse of the arachnoid cyst. The combination of nTMS and tractography supports the identification of a safe trajectory for cystoventriculostomy in eloquent arachnoid cysts. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Biodegradable Magnetic Silica@Iron Oxide Nanovectors with Ultra-Large Mesopores for High Protein Loading, Magnetothermal Release, and Delivery

    KAUST Repository

    Omar, Haneen

    2016-11-29

    The delivery of large cargos of diameter above 15 nm for biomedical applications has proved challenging since it requires biocompatible, stably-loaded, and biodegradable nanomaterials. In this study, we describe the design of biodegradable silica-iron oxide hybrid nanovectors with large mesopores for large protein delivery in cancer cells. The mesopores of the nanomaterials spanned from 20 to 60 nm in diameter and post-functionalization allowed the electrostatic immobilization of large proteins (e.g. mTFP-Ferritin, ~ 534 kDa). Half of the content of the nanovectors was based with iron oxide nanophases which allowed the rapid biodegradation of the carrier in fetal bovine serum and a magnetic responsiveness. The nanovectors released large protein cargos in aqueous solution under acidic pH or magnetic stimuli. The delivery of large proteins was then autonomously achieved in cancer cells via the silica-iron oxide nanovectors, which is thus a promising for biomedical applications.

  6. Particle-in-cell simulations of asymmetric guide-field reconnection: quadrupolar structure of Hall magnetic field

    Science.gov (United States)

    Schmitz, R. G.; Alves, M. V.; Barbosa, M. V. G.

    2017-12-01

    One of the most important processes that occurs in Earth's magnetosphere is known as magnetic reconnection (MR). This process can be symmetric or asymmetric, depending basically on the plasma density and magnetic field in both sides of the current sheet. A good example of symmetric reconnection in terrestrial magnetosphere occurs in the magnetotail, where these quantities are similar on the north and south lobes. In the dayside magnetopause MR is asymmetric, since the plasma regimes and magnetic fields of magnetosheath and magnetosphere are quite different. Symmetric reconnection has some unique signatures. For example, the formation of a quadrupolar structure of Hall magnetic field and a bipolar Hall electric field that points to the center of the current sheet. The different particle motions in the presence of asymmetries change these signatures, causing the quadrupolar pattern to be distorted and forming a bipolar structure. Also, the bipolar Hall electric field is modified and gives rise to a single peak pointing toward the magnetosheat, considering an example of magnetopause reconnection. The presence of a guide-field can also distort the quadrupolar pattern, by giving a shear angle across the current sheet and altering the symmetric patterns, according to previous simulations and observations. Recently, a quadrupolar structure was observed in an asymmetric guide-field MR event using MMS (Magnetospheric Multiscale) mission data [Peng et al., JGR, 2017]. This event shows clearly that the density asymmetry and the guide-field were not sufficient to form signatures of asymmetric reconnection. Using the particle-in-cell code iPIC3D [Markidis et al, Mathematics and Computers in Simulation, 2010] with the MMS data from this event used to define input parameters, we found a quadrupolar structure of Hall magnetic field and a bipolar pattern of Hall electric field in ion scales, showing that our results are in an excellent agreement with the MMS observations. To our

  7. Fabrication and characterization of nano-particulate PtCo media for ultra-high density perpendicular magnetic recording

    International Nuclear Information System (INIS)

    Newman, Dave M; Wears, M Lesley; Jollie, Michael; Choo, Desmond

    2007-01-01

    The year-on-year growth in areal recording density maintained now for half a century by the hard disk industry has required a corresponding reduction in the size of the magnetic grains comprising the storage media employed. Grain dimensions are now such that the performance of materials which thus far have served the industry well can no longer be maintained as further reduction in their volume risks breaching the superparamagnetic limit with the attendant loss of data integrity. The high magnetocrystalline anisotropy of the Ll 0 phase of PtCo allows particles as small as 4 nm diameter to remain magnetically stable in the elevated temperature environment typical of disk drive systems. A non-interacting dispersion of nanomagnetic particles suspended in an inert non-magnetic host such that each has its anisotropy axis directed perpendicular to the surface of the medium now constitutes the new ideal for a recording medium. Fabrication by a novel combination of conventional sputtering and thermal processing technologies of a medium closely approximating this ideal is demonstrated. An optimized two-stage fabrication process produces a near mono-dispersion of particles with magnetic activation volumes centred about 5 x 10 23 and crystallized in the L1 0 phase with an orientated tetragonal structure. The characteristics of this medium are discussed as a function of composition and crystalline structure. In the absence of a thermally assisted recording head, experiments are conducted on a degraded form of the medium that is shown to support perpendicular recording at linear densities in excess of 240 kfci (D50 point)

  8. Variational Symplectic Integrator for Long-Time Simulations of the Guiding-Center Motion of Charged Particles in General Magnetic Fields

    International Nuclear Information System (INIS)

    Qin Hong; Guan Xiaoyin

    2008-01-01

    A variational symplectic integrator for the guiding-center motion of charged particles in general magnetic fields is developed for long-time simulation studies of magnetized plasmas. Instead of discretizing the differential equations of the guiding-center motion, the action of the guiding-center motion is discretized and minimized to obtain the iteration rules for advancing the dynamics. The variational symplectic integrator conserves exactly a discrete Lagrangian symplectic structure, and has better numerical properties over long integration time, compared with standard integrators, such as the standard and variable time-step fourth order Runge-Kutta methods

  9. Variational Symplectic Integrator for Long-Time Simulations of the Guiding-Center Motion of Charged Particles in General Magnetic Fields

    International Nuclear Information System (INIS)

    Qin, H.; Guan, X.

    2008-01-01

    A variational symplectic integrator for the guiding-center motion of charged particles in general magnetic fields is developed for long-time simulation studies of magnetized plasmas. Instead of discretizing the differential equations of the guiding-center motion, the action of the guiding-center motion is discretized and minimized to obtain the iteration rules for advancing the dynamics. The variational symplectic integrator conserves exactly a discrete Lagrangian symplectic structure, and has better numerical properties over long integration time, compared with standard integrators, such as the standard and variable time-step fourth order Runge-Kutta methods.

  10. Generalized theory of a free-electron laser in a helical wiggler and guide magnetic fields using the kinetic approach

    International Nuclear Information System (INIS)

    Misra, K.D.; Mishra, P.K.

    2002-01-01

    A self-consistent theory of a free-electron laser is developed by the kinetic approach, using the method of characteristics in helical wiggler and guide magnetic fields. The detailed relativistic particle trajectories obtained in wiggler and guide magnetic fields are used in linearized Vlasov-Maxwell equations having variations in perpendicular and parallel momenta to obtain the perturbed distribution function in terms of perturbed electric and magnetic fields deviating from the vector potential approach. The perturbed distribution function thus obtained, having variations in perpendicular and parallel momenta for an arbitrary distribution function, is used to obtain current, conductivity and dielectric tensors. The full dispersion relation (FDR) and Compton dispersion relation (CDR) have been obtained. The dispersion diagram has been obtained and the interaction of the negative longitudinal space charge with the electromagnetic wave has been shown. The temporal growth rates obtained from the full dispersion relation and Compton dispersion relation for the tenuous cold relativistic beam in microwave region have been discussed

  11. Ultra-high resistive and anisotropic CoPd-CaF2 nanogranular soft magnetic films prepared by tandem-sputtering deposition

    Science.gov (United States)

    Naoe, Masayuki; Kobayashi, Nobukiyo; Ohnuma, Shigehiro; Iwasa, Tadayoshi; Arai, Ken-Ichi; Masumoto, Hiroshi

    2015-10-01

    Ultra-high resistive and anisotropic soft magnetic films for gigahertz applications are desirable to demonstrate the really practical films. Here we present a study of novel nanogranular films fabricated by tandem-sputtering deposition. Their electromagnetic properties and nanostructure have also been discussed. These films consisted of nanocrystallized CoPd alloy-granules and CaF2 matrix, and a specimen having a composition of (Co0.69Pd0.31)52-(Ca0.31F0.69)48 exhibited distinct in-plane uniaxial anisotropy after uniaxial field annealing with granule growth. Its complex permeability spectra have a ferromagnetic resonance frequency extending to the Super-High-Frequency band due to its higher anisotropy field, and its frequency response was quite well reproduced by a numerical calculation based on the Landau-Lifshitz-Gilbert equation. Furthermore, it was clarified that the CaF2-based nanogranular film exhibits a hundredfold higher electrical resistivity than conventional oxide or nitride-based films. Higher resistivity enables the film thickness to achieve a margin exceeding threefold against eddy current loss. The greater resistivity of nanogranular films is attributed to the wide energy bandgap and superior crystallinity of CaF2 matrix.

  12. Online Magnetic Resonance Image Guided Adaptive Radiation Therapy: First Clinical Applications

    International Nuclear Information System (INIS)

    Acharya, Sahaja; Fischer-Valuck, Benjamin W.; Kashani, Rojano; Parikh, Parag; Yang, Deshan; Zhao, Tianyu; Green, Olga; Wooten, Omar; Li, H. Harold; Hu, Yanle; Rodriguez, Vivian; Olsen, Lindsey; Robinson, Clifford; Michalski, Jeff; Mutic, Sasa; Olsen, Jeffrey

    2016-01-01

    Purpose: To demonstrate the feasibility of online adaptive magnetic resonance (MR) image guided radiation therapy (MR-IGRT) through reporting of our initial clinical experience and workflow considerations. Methods and Materials: The first clinically deployed online adaptive MR-IGRT system consisted of a split 0.35T MR scanner straddling a ring gantry with 3 multileaf collimator-equipped "6"0Co heads. The unit is supported by a Monte Carlo–based treatment planning system that allows real-time adaptive planning with the patient on the table. All patients undergo computed tomography and MR imaging (MRI) simulation for initial treatment planning. A volumetric MRI scan is acquired for each patient at the daily treatment setup. Deformable registration is performed using the planning computed tomography data set, which allows for the transfer of the initial contours and the electron density map to the daily MRI scan. The deformed electron density map is then used to recalculate the original plan on the daily MRI scan for physician evaluation. Recontouring and plan reoptimization are performed when required, and patient-specific quality assurance (QA) is performed using an independent in-house software system. Results: The first online adaptive MR-IGRT treatments consisted of 5 patients with abdominopelvic malignancies. The clinical setting included neoadjuvant colorectal (n=3), unresectable gastric (n=1), and unresectable pheochromocytoma (n=1). Recontouring and reoptimization were deemed necessary for 3 of 5 patients, and the initial plan was deemed sufficient for 2 of the 5 patients. The reasons for plan adaptation included tumor progression or regression and a change in small bowel anatomy. In a subsequently expanded cohort of 170 fractions (20 patients), 52 fractions (30.6%) were reoptimized online, and 92 fractions (54.1%) were treated with an online-adapted or previously adapted plan. The median time for recontouring, reoptimization, and QA was 26

  13. Online Magnetic Resonance Image Guided Adaptive Radiation Therapy: First Clinical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, Sahaja; Fischer-Valuck, Benjamin W.; Kashani, Rojano; Parikh, Parag; Yang, Deshan; Zhao, Tianyu; Green, Olga; Wooten, Omar; Li, H. Harold; Hu, Yanle; Rodriguez, Vivian; Olsen, Lindsey; Robinson, Clifford; Michalski, Jeff; Mutic, Sasa; Olsen, Jeffrey, E-mail: jolsen@radonc.wustl.edu

    2016-02-01

    Purpose: To demonstrate the feasibility of online adaptive magnetic resonance (MR) image guided radiation therapy (MR-IGRT) through reporting of our initial clinical experience and workflow considerations. Methods and Materials: The first clinically deployed online adaptive MR-IGRT system consisted of a split 0.35T MR scanner straddling a ring gantry with 3 multileaf collimator-equipped {sup 60}Co heads. The unit is supported by a Monte Carlo–based treatment planning system that allows real-time adaptive planning with the patient on the table. All patients undergo computed tomography and MR imaging (MRI) simulation for initial treatment planning. A volumetric MRI scan is acquired for each patient at the daily treatment setup. Deformable registration is performed using the planning computed tomography data set, which allows for the transfer of the initial contours and the electron density map to the daily MRI scan. The deformed electron density map is then used to recalculate the original plan on the daily MRI scan for physician evaluation. Recontouring and plan reoptimization are performed when required, and patient-specific quality assurance (QA) is performed using an independent in-house software system. Results: The first online adaptive MR-IGRT treatments consisted of 5 patients with abdominopelvic malignancies. The clinical setting included neoadjuvant colorectal (n=3), unresectable gastric (n=1), and unresectable pheochromocytoma (n=1). Recontouring and reoptimization were deemed necessary for 3 of 5 patients, and the initial plan was deemed sufficient for 2 of the 5 patients. The reasons for plan adaptation included tumor progression or regression and a change in small bowel anatomy. In a subsequently expanded cohort of 170 fractions (20 patients), 52 fractions (30.6%) were reoptimized online, and 92 fractions (54.1%) were treated with an online-adapted or previously adapted plan. The median time for recontouring, reoptimization, and QA was 26

  14. Positron emission tomography-guided magnetic resonance spectroscopy in Alzheimer disease.

    Science.gov (United States)

    Sheikh-Bahaei, Nasim; Sajjadi, S Ahmad; Manavaki, Roido; McLean, Mary; O'Brien, John T; Gillard, Jonathan H

    2018-04-01

    To determine whether the level of metabolites in magnetic resonance spectroscopy (MRS) is a representative marker of underlying pathological changes identified in positron emission tomographic (PET) images in Alzheimer disease (AD). We performed PET-guided MRS in cases of probable AD, mild cognitive impairment (MCI), and healthy controls (HC). All participants were imaged by 11 C-Pittsburgh compound B ( 11 C-PiB) and 18 F-fluorodeoxyglucose ( 18 F-FDG) PET followed by 3T MRS. PET images were assessed both visually and using standardized uptake value ratios (SUVRs). MRS voxels were placed in regions with maximum abnormality on amyloid (Aβ+) and FDG (hypometabolic) areas on PET scans. Corresponding normal areas were selected in controls. The ratios of total N-acetyl (tNA) group, myoinositol (mI), choline, and glutamate + glutamine over creatine (Cr) were compared between these regions. Aβ + regions had significantly higher (p = 0.02) mI/Cr and lower tNA/Cr (p = 0.02), whereas in hypometabolic areas only tNA/Cr was reduced (p = 0.003). Multiple regression analysis adjusting for sex, age, and education showed mI/Cr was only associated with 11 C-PiB SUVR (p < 0.0001). tNA/Cr, however, was associated with both PiB (p = 0.0003) and 18 F-FDG SUVR (p = 0.006). The level of mI/Cr was not significantly different between MCI and AD (p = 0.28), but tNA/Cr showed significant decline from HC to MCI to AD (p = 0.001, p = 0.04). mI/Cr has significant temporal and spatial associations with Aβ and could potentially be considered as a disease state biomarker. tNA is an indicator of early neurodegenerative changes and might have a role as disease stage biomarker and also as a valuable surrogate marker for treatment response. Ann Neurol 2018;83:771-778. © 2018 American Neurological Association.

  15. Effect of Prostate Magnetic Resonance Imaging/Ultrasound Fusion-guided Biopsy on Radiation Treatment Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Aaron; Valle, Luca F.; Shankavaram, Uma; Krauze, Andra; Kaushal, Aradhana; Schott, Erica; Cooley-Zgela, Theresa [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland (United States); Wood, Bradford [Center for Interventional Oncology, National Institutes of Health, Bethesda, Maryland (United States); Pinto, Peter [Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland (United States); Choyke, Peter; Turkbey, Baris [Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland (United States); Citrin, Deborah E., E-mail: citrind@mail.nih.gov [Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland (United States)

    2017-04-01

    Purpose: Targeted magnetic resonance imaging (MRI)/ultrasound fusion prostate biopsy (MRI-Bx) has recently been compared with the standard of care extended sextant ultrasound-guided prostate biopsy (SOC-Bx), with the former associated with an increased rate of detection of clinically significant prostate cancer. The present study sought to determine the influence of MRI-Bx on radiation therapy and androgen deprivation therapy (ADT) recommendations. Methods and Materials: All patients who had received radiation treatment and had undergone SOC-Bx and MRI-Bx at our institution were included. Using the clinical T stage, pretreatment prostate-specific antigen, and Gleason score, patients were categorized into National Comprehensive Cancer Network risk groups and radiation treatment or ADT recommendations assigned. Intensification of the recommended treatment after multiparametric MRI, SOC-Bx, and MRI-Bx was evaluated. Results: From January 2008 to January 2016, 73 patients received radiation therapy at our institution after undergoing a simultaneous SOC-Bx and MRI-Bx (n=47 with previous SOC-Bx). Repeat SOC-Bx and MRI-Bx resulted in frequent upgrading compared with previous SOC-Bx (Gleason score 7, 6.7% vs 44.6%; P<.001; Gleason score 8-10, 2.1% vs 38%; P<.001). MRI-Bx increased the proportion of patients classified as very high risk from 24.7% to 41.1% (P=.027). Compared with SOC-Bx alone, including the MRI-Bx findings resulted in a greater percentage of pathologically positive cores (mean 37% vs 44%). Incorporation of multiparametric MRI and MRI-Bx results increased the recommended use and duration of ADT (duration increased in 28 of 73 patients and ADT was added for 8 of 73 patients). Conclusions: In patients referred for radiation treatment, MRI-Bx resulted in an increase in the percentage of positive cores, Gleason score, and risk grouping. The benefit of treatment intensification in accordance with the MRI-Bx findings is unknown.

  16. Treatment of uterine leiomyoma with magnetic resonance-guided focused ultrasound surgery (MRgFUS)

    International Nuclear Information System (INIS)

    Fukunishi, Hidenobu

    2007-01-01

    Uterine leiomyoma is the most common pelvic tumor in women. Although hysterectomy has long been the standard treatment for uterine myoma, some uterus-preserving alternatives are available today. Among these, magnetic resonance-guided focused ultrasound surgery (MRgFUS) is a minimally-invasive procedure that uses high intensity ultrasound waves to ablate tissue. The present study investigates the efficacy of MRgFUS in the treatment of uterine myoma and the histopathological features on extirpated myoma tissue, when alternative surgical treatment is requisite. The Ethics Committee of Shinsuma Hospital approved the treatment of uterine myoma by MRgFUS, and written informed consent was obtained from all of the patients in compliance with the principles of good clinical practice. Between June 2004 and March 2007, 81 premenopausal patients with 125 myomas confirmed by T2-weighted MRI were treated by MRgFUS. The myomas were classified into 3 types based on signal intensity of T2-weighted images type I, low intensity; type II, intermediate intensity and type III, high intensity. The ablation (the non-perfused ratio of gadolinium injection) was about 55% in type I and type II, and 38% in type III. There was no correlation between the ablation ratio and the location or the size of the myoma. The uterine muscle was spared ablation when 2 combined myomas were treated as one tumor, suggesting that the vascularity was richer in the uterine muscle layer than in the myoma Sufficient ablation of the myoma near the Os sacrum is not able to attain immediately after the treatment; however, in several cases a complete non-perfusion margin was observed 3 or 6 months after the treatment. These cases yield very satisfactory results and it is meaningful to search for the reason why such good results were induced. Alternative treatment such as hysterectomy, myomectomy, trans cervical resection (TCR) or uterine artery embolization (UAE) was indicated for 13.6% of the patients. Here, we

  17. The Travelling-Wave Primate System: A New Solution for Magnetic Resonance Imaging of Macaque Monkeys at 7 Tesla Ultra-High Field.

    Science.gov (United States)

    Herrmann, Tim; Mallow, Johannes; Plaumann, Markus; Luchtmann, Michael; Stadler, Jörg; Mylius, Judith; Brosch, Michael; Bernarding, Johannes

    2015-01-01

    Neuroimaging of macaques at ultra-high field (UHF) is usually conducted by combining a volume coil for transmit (Tx) and a phased array coil for receive (Rx) tightly enclosing the monkey's head. Good results have been achieved using vertical or horizontal magnets with implanted or near-surface coils. An alternative and less costly approach, the travelling-wave (TW) excitation concept, may offer more flexible experimental setups on human whole-body UHF magnetic resonance imaging (MRI) systems, which are now more widely available. Goal of the study was developing and validating the TW concept for in vivo primate MRI. The TW Primate System (TWPS) uses the radio frequency shield of the gradient system of a human whole-body 7 T MRI system as a waveguide to propagate a circularly polarized B1 field represented by the TE11 mode. This mode is excited by a specifically designed 2-port patch antenna. For receive, a customized neuroimaging monkey head receive-only coil was designed. Field simulation was used for development and evaluation. Signal-to-noise ratio (SNR) was compared with data acquired with a conventional monkey volume head coil consisting of a homogeneous transmit coil and a 12-element receive coil. The TWPS offered good image homogeneity in the volume-of-interest Turbo spin echo images exhibited a high contrast, allowing a clear depiction of the cerebral anatomy. As a prerequisite for functional MRI, whole brain ultrafast echo planar images were successfully acquired. The TWPS presents a promising new approach to fMRI of macaques for research groups with access to a horizontal UHF MRI system.

  18. Ultra-high resistive and anisotropic CoPd–CaF{sub 2} nanogranular soft magnetic films prepared by tandem-sputtering deposition

    Energy Technology Data Exchange (ETDEWEB)

    Naoe, Masayuki, E-mail: naoe@denjiken.ne.jp [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Kobayashi, Nobukiyo [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Ohnuma, Shigehiro [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578 (Japan); Iwasa, Tadayoshi; Arai, Ken-Ichi [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Masumoto, Hiroshi [Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578 (Japan)

    2015-10-01

    Ultra-high resistive and anisotropic soft magnetic films for gigahertz applications are desirable to demonstrate the really practical films. Here we present a study of novel nanogranular films fabricated by tandem-sputtering deposition. Their electromagnetic properties and nanostructure have also been discussed. These films consisted of nanocrystallized CoPd alloy-granules and CaF{sub 2} matrix, and a specimen having a composition of (Co{sub 0.69}Pd{sub 0.31}){sub 52}–(Ca{sub 0.31}F{sub 0.69}){sub 48} exhibited distinct in-plane uniaxial anisotropy after uniaxial field annealing with granule growth. Its complex permeability spectra have a ferromagnetic resonance frequency extending to the Super-High-Frequency band due to its higher anisotropy field, and its frequency response was quite well reproduced by a numerical calculation based on the Landau–Lifshitz–Gilbert equation. Furthermore, it was clarified that the CaF{sub 2}-based nanogranular film exhibits a hundredfold higher electrical resistivity than conventional oxide or nitride-based films. Higher resistivity enables the film thickness to achieve a margin exceeding threefold against eddy current loss. The greater resistivity of nanogranular films is attributed to the wide energy bandgap and superior crystallinity of CaF{sub 2} matrix. - Highlights: • We fabricated high-resistive and anisotropic granular films by tandem-sputtering. • CaF{sub 2}-based films exhibit a hundredfold higher resistivity than conventional films. • Uniaxial field annealing improved the magnetic properties dramatically. • High uniaxial anisotropy extended ferromagnetic resonance frequency to 4 GHz. • Annealed samples can be regarded as a ferromagnetic homogenized material.

  19. The Travelling-Wave Primate System: A New Solution for Magnetic Resonance Imaging of Macaque Monkeys at 7 Tesla Ultra-High Field.

    Directory of Open Access Journals (Sweden)

    Tim Herrmann

    Full Text Available Neuroimaging of macaques at ultra-high field (UHF is usually conducted by combining a volume coil for transmit (Tx and a phased array coil for receive (Rx tightly enclosing the monkey's head. Good results have been achieved using vertical or horizontal magnets with implanted or near-surface coils. An alternative and less costly approach, the travelling-wave (TW excitation concept, may offer more flexible experimental setups on human whole-body UHF magnetic resonance imaging (MRI systems, which are now more widely available. Goal of the study was developing and validating the TW concept for in vivo primate MRI.The TW Primate System (TWPS uses the radio frequency shield of the gradient system of a human whole-body 7 T MRI system as a waveguide to propagate a circularly polarized B1 field represented by the TE11 mode. This mode is excited by a specifically designed 2-port patch antenna. For receive, a customized neuroimaging monkey head receive-only coil was designed. Field simulation was used for development and evaluation. Signal-to-noise ratio (SNR was compared with data acquired with a conventional monkey volume head coil consisting of a homogeneous transmit coil and a 12-element receive coil.The TWPS offered good image homogeneity in the volume-of-interest Turbo spin echo images exhibited a high contrast, allowing a clear depiction of the cerebral anatomy. As a prerequisite for functional MRI, whole brain ultrafast echo planar images were successfully acquired.The TWPS presents a promising new approach to fMRI of macaques for research groups with access to a horizontal UHF MRI system.

  20. Remote Cherenkov imaging-based quality assurance of a magnetic resonance image-guided radiotherapy system.

    Science.gov (United States)

    Andreozzi, Jacqueline M; Mooney, Karen E; Brůža, Petr; Curcuru, Austen; Gladstone, David J; Pogue, Brian W; Green, Olga

    2018-06-01

    Tools to perform regular quality assurance of magnetic resonance image-guided radiotherapy (MRIgRT) systems should ideally be independent of interference from the magnetic fields. Remotely acquired optical Cherenkov imaging-based dosimetry measurements in water were investigated for this purpose, comparing measures of dose accuracy, temporal dynamics, and overall integrated IMRT delivery. A 40 × 30.5 × 37.5 cm 3 water tank doped with 1 g/L of quinine sulfate was imaged using an intensified charge-coupled device (ICCD) to capture the Cherenkov emission while being irradiated by a commercial MRIgRT system (ViewRay™). The ICCD was placed down-bore at the end of the couch, 4 m from treatment isocenter and behind the 5-Gauss line of the 0.35-T MRI. After establishing optimal camera acquisition settings, square beams of increasing size (4.2 × 4.2 cm 2 , 10.5 × 10.5 cm 2 , and 14.7 × 14.7 cm 2 ) were imaged at 0.93 frames per second, from an individual cobalt-60 treatment head, to develop projection measures related to percent depth dose (PDD) curves and cross beam profiles (CPB). These Cherenkov-derived measurements were compared to ionization chamber (IC) and radiographic film dosimetry data, as well as simulation data from the treatment planning system (TPS). An intensity-modulated radiotherapy (IMRT) commissioning plan from AAPM TG-119 (C4:C-Shape) was also imaged at 2.1 frames per second, and the single linear sum image from 509 s of plan delivery was compared to the dose volume prediction generated by the TPS using gamma index analysis. Analysis of standardized test target images (1024 × 1024 pixels) yielded a pixel resolution of 0.37 mm/pixel. The beam width measured from the Cherenkov image-generated projection CBPs was within 1 mm accuracy when compared to film measurements for all beams. The 502 point measurements (i.e., pixels) of the Cherenkov image-based projection percent depth dose curves (pPDDs) were compared to p

  1. Magnetic nanoparticles for precision oncology: theranostic magnetic iron oxide nanoparticles for image-guided and targeted cancer therapy.

    Science.gov (United States)

    Zhu, Lei; Zhou, Zhiyang; Mao, Hui; Yang, Lily

    2017-01-01

    Recent advances in the development of magnetic nanoparticles (MNPs) have shown promise in the development of new personalized therapeutic approaches for clinical management of cancer patients. The unique physicochemical properties of MNPs endow them with novel multifunctional capabilities for imaging, drug delivery and therapy, which are referred to as theranostics. To facilitate the translation of those theranostic MNPs into clinical applications, extensive efforts have been made on designing and improving biocompatibility, stability, safety, drug-loading ability, targeted delivery, imaging signal and thermal- or photodynamic response. In this review, we provide an overview of the physicochemical properties, toxicity and theranostic applications of MNPs with a focus on magnetic iron oxide nanoparticles.

  2. Interfacial exchange, magnetic coupling and magnetoresistance in ultra-thin GdN/NbN/GdN tri-layers

    Science.gov (United States)

    Takamura, Yota; Goncalves, Rafael S.; Cascales, Juan Pedro; Altinkok, Atilgan; de Araujo, Clodoaldo I. L.; Lauter, Valeria; Moodera, Jagadeesh S.; MIT Team

    Superconducting spin-valve structures with a superconductive (SC) spacer sandwiched between ferromagnetic (FM) insulating layers [Li PRL 2013, Senapati APL 2013, Zhu Nat. Mat. 2016.] are attractive since the SC and FM characteristics can mutually be controlled by the proximity effect. We investigated reactively sputtered GdN/NbN/GdN tri-layer structures with various (SC) NbN spacer thicknesses (dNbN) from superconducting to normal layers. Magnetoresistive behavior similar to GMR in metallic magnetic multilayers was observed in the tri-layers with dNbN between 5-10 monolayers (ML), where thinner NbN layers did not show superconductivity down to 4.2 K. The occurrence of GMR signal indicates the presence of a ML of FM metallic layers at the GdN/NbN interfaces. Susceptibility and transport measurements in these samples revealed that the interface layers (ILs) are ferromagnetically coupled with adjacent GdN layers. The thickness of each of the IL is deduced to be about 1.25 ML, and as a result for dNbN magnetically coupled and switched simultaneously. These findings and interfacial characterization by various techniques will be presented. Work supported by NSF and ONR Grants.

  3. EEG-guided transcranial magnetic stimulation reveals rapid shifts in motor cortical excitability during the human sleep slow oscillation

    DEFF Research Database (Denmark)

    Bergmann, Til O; Mölle, Matthias; Schmidt, Marlit A

    2012-01-01

    Evoked cortical responses do not follow a rigid input–output function but are dynamically shaped by intrinsic neural properties at the time of stimulation. Recent research has emphasized the role of oscillatory activity in determining cortical excitability. Here we employed EEG-guided transcranial......, closely resembling a spontaneous SO. However, both MEPs and TEPs were consistently larger when evoked during SO up-states than during down-states, and ampliudes within each SO state depended on the actual EEG potential at the time and site of stimulation. These results provide first-time evidence...... magnetic stimulation (TMS) during non-rapid eye movement sleep to examine whether the spontaneous

  4. Diffusion-weighted magnetic resonance imaging in the prostate transition zone: histopathological validation using magnetic resonance-guided biopsy specimens

    NARCIS (Netherlands)

    Hoeks, C.M.A.; Vos, E.K.; Bomers, J.G.R.; Barentsz, J.O.; Kaa, C.A. van de; Scheenen, T.W.J.

    2013-01-01

    OBJECTIVES: The objective of this study was to evaluate the apparent diffusion coefficient (ADC) of diffusion-weighted magnetic resonance (MR) imaging for the differentiation of transition zone cancer from non-cancerous transition zone with and without prostatitis and for the differentiation of

  5. Magnetic resonance-compatible robotic and mechatronics systems for image-guided interventions and rehabilitation: a review study.

    Science.gov (United States)

    Tsekos, Nikolaos V; Khanicheh, Azadeh; Christoforou, Eftychios; Mavroidis, Constantinos

    2007-01-01

    The continuous technological progress of magnetic resonance imaging (MRI), as well as its widespread clinical use as a highly sensitive tool in diagnostics and advanced brain research, has brought a high demand for the development of magnetic resonance (MR)-compatible robotic/mechatronic systems. Revolutionary robots guided by real-time three-dimensional (3-D)-MRI allow reliable and precise minimally invasive interventions with relatively short recovery times. Dedicated robotic interfaces used in conjunction with fMRI allow neuroscientists to investigate the brain mechanisms of manipulation and motor learning, as well as to improve rehabilitation therapies. This paper gives an overview of the motivation, advantages, technical challenges, and existing prototypes for MR-compatible robotic/mechatronic devices.

  6. Multi-frequency ESR studies on a Haldane magnet in a field-induced phase at ultra-low temperatures

    International Nuclear Information System (INIS)

    Hagiwara, Masayuki; Kashiwagi, Takanari; Idutsu, Yuichi; Honda, Zentaro; Miyazaki, Hiroshi; Harada, Isao

    2010-01-01

    We report the results of multi-frequency electron spin resonance (ESR) measurements on single crystals of Ni(C 5 H 14 N 2 ) 2 N 3 (PF 6 ) which is regarded as the one-dimensional Heisenberg antiferromagnet with spin one, namely the Haldane magnet, at very low temperatures down to about 100 mK. We observed the lowest resonance branch below about 500 mK for the field along the chain direction (H||c), which was observed previously only in an inelastic neutron scattering experiment at 30 mK. We compare the resonance branch with that calculated by a phenomenological field theory, and discuss the field dependence and the temperature sensitivity of this ESR branch.

  7. Development and performance of a 129-GHz dynamic nuclear polarizer in an ultra-wide bore superconducting magnet.

    Science.gov (United States)

    Lumata, Lloyd L; Martin, Richard; Jindal, Ashish K; Kovacs, Zoltan; Conradi, Mark S; Merritt, Matthew E

    2015-04-01

    We sought to build a dynamic nuclear polarization system for operation at 4.6 T (129 GHz) and evaluate its efficiency in terms of (13)C polarization levels using free radicals that span a range of ESR linewidths. A liquid helium cryostat was placed in a 4.6 T superconducting magnet with a 150-mm warm bore diameter. A 129-GHz microwave source was used to irradiate (13)C enriched samples. Temperatures close to 1 K were achieved using a vacuum pump with a 453-m(3)/h roots blower. A hyperpolarized (13)C nuclear magnetic resonance (NMR) signal was detected using a saddle coil and a Varian VNMRS console operating at 49.208 MHz. Samples doped with free radicals BDPA (1,3-bisdiphenylene-2-phenylallyl), trityl OX063 (tris{8-carboxyl-2,2,6,6-benzo(1,2-d:4,5-d)-bis(1,3)dithiole-4-yl}methyl sodium salt), galvinoxyl ((2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxy), 2,2-diphenylpicrylhydrazyl (DPPH) and 4-oxo-TEMPO (4-Oxo-2,2,6,6-tetramethyl-1-piperidinyloxy) were assayed. Microwave dynamic nuclear polarization (DNP) spectra and solid-state (13)C polarization levels for these samples were determined. (13)C polarization levels close to 50 % were achieved for [1-(13)C]pyruvic acid at 1.15 K using the narrow electron spin resonance (ESR) linewidth free radicals trityl OX063 and BDPA, while 10-20 % (13)C polarizations were achieved using galvinoxyl, DPPH and 4-oxo-TEMPO. At this field strength free radicals with smaller ESR linewidths are still superior for DNP of (13)C as opposed to those with linewidths that exceed that of the (1)H Larmor frequency.

  8. Ultra high-current superconducting cables for a 2.2-Tesla, 300-kilojoule energy storage magnet

    International Nuclear Information System (INIS)

    Miranda, G.A.; Rhodenizer, R.; Rackov, P.; Punchard, W.F.B.; de Winter, T.A.

    1976-01-01

    These 2.2-T, 300-kJ magnets are to operate at 10 to 12 kA with a safety factor in critical current of about 50 percent at 10 kA. The conductor must exhibit low losses in addition to being stable. Magnetic Corporation of America (MCA) designed a flat conductor using 1224 copper-matrix, monofilament wires combined in two stages of cabling followed by two stages of flat braiding. Two of these conductors were constructed, one with wire already on hand and the second using wire made specifically for this application. Intermagnetics General Corporation (IGC) designed two rectangular conductors using 315 and 319 mixed-matrix multifilament wires combined in three stages of cabling followed by compaction in a Turk's head. The maximum transport current capabilities (I/sub t/) of these cables were measured in hairpin shaped samples with the straight section under test in perpendicularly applied fields. The measured results at 2.5 T for the two MCA cables were 11.7 kA and 15.4 kA, and for the IGC cables were 18.2 kA and 19.3 kA (extrapolated). In addition, samples of the compacted and uncompacted major strands from the IGC cables were tested. The results of these measurements are compred with values of I/sub t/ from the single-wire critical currents taking into account the adjacent conductor fields and the cable self-fields.Several causes of degradation of I/sub t/ in the compacted cable are discussed including those due to experimental factors

  9. Combined Inter- and Intrafractional Plan Adaptation Using Fraction Partitioning in Magnetic Resonance-guided Radiotherapy Delivery.

    Science.gov (United States)

    Lagerwaard, Frank; Bohoudi, Omar; Tetar, Shyama; Admiraal, Marjan A; Rosario, Tezontl S; Bruynzeel, Anna

    2018-04-05

    Magnetic resonance-guided radiation therapy (MRgRT) not only allows for superior soft-tissue setup and online MR-guidance during delivery but also for inter-fractional plan re-optimization or adaptation. This plan adaptation involves repeat MR imaging, organs at risk (OARs) re-contouring, plan prediction (i.e., recalculating the baseline plan on the anatomy of that moment), plan re-optimization, and plan quality assurance. In contrast, intrafractional plan adaptation cannot be simply performed by pausing delivery at any given moment, adjusting contours, and re-optimization because of the complex and composite nature of deformable dose accumulation. To overcome this limitation, we applied a practical workaround by partitioning treatment fractions, each with half the original fraction dose. In between successive deliveries, the patient remained in the treatment position and all steps of the initial plan adaptation were repeated. Thus, this second re-optimization served as an intrafractional plan adaptation at 50% of the total delivery. The practical feasibility of this partitioning approach was evaluated in a patient treated with MRgRT for locally advanced pancreatic cancer (LAPC). MRgRT was delivered in 40Gy in 10 fractions, with two fractions scheduled successively on each treatment day. The contoured gross tumor volume (GTV) was expanded by 3 mm, excluding parts of the OARs within this expansion to derive the planning target volume for daily re-optimization (PTV OPT ). The baseline GTVV 95%  achieved in this patient was 80.0% to adhere to the high-dose constraints for the duodenum, stomach, and bowel (V 33 Gy ViewRay Inc, Mountain View, USA) using video-assisted breath-hold in shallow inspiration. The dual plan adaptation resulted, for each partitioned fraction, in the generation of Plan PREDICTED1 , Plan RE-OPTIMIZED1  (inter-fractional adaptation), Plan PREDICTED2 , and Plan RE-OPTIMIZED2  (intrafractional adaptation). An offline analysis was

  10. Improved foilless Ku-band transit-time oscillator for generating gigawatt level microwave with low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ling, Junpu; He, Juntao, E-mail: hejuntao12@163.com; Zhang, Jiande; Jiang, Tao; Hu, Yi [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-09-15

    An improved foilless Ku-band transit-time oscillator with low guiding magnetic field is proposed and investigated in this paper. With a non-uniform buncher and a coaxial TM{sub 02} mode dual-resonant reflector, this improved device can output gigawatt level Ku-band microwave with relatively compact radial dimensions. Besides the above virtue, this novel reflector also has the merits of high TEM reflectance, being more suitable for pre-modulating the electron beam and enhancing the conversion efficiency. Moreover, in order to further increase the conversion efficiency and lower the power saturation time, a depth-tunable coaxial collector and a resonant cavity located before the extractor are employed in our device. Main structure parameters of the device are optimized by particle in cell simulations. The typical simulation result is that, with a 380 kV, 8.2 kA beam guided by a magnetic field of about 0.6 T, 1.15 GW microwave pulse at 14.25 GHz is generated, yielding a conversion efficiency of about 37%.

  11. {sup 1}H-NMR and charge transport in metallic polypyrrole at ultra-low temperatures and high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Jugeshwar Singh, K; Ramesh, K P; Menon, Reghu [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Clark, W G [Department of Physics and Astronomy, University of California at Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095 (United States)], E-mail: jshwar@physics.iisc.ernet.in

    2008-11-19

    The temperature dependence of conductivity, proton spin relaxation time (T{sub 1}) and magnetoconductance (MC) in metallic polypyrrole (PPy) doped with PF{sub 6}{sup -} have been carried out at mK temperatures and high magnetic fields. At T<1 K both electron-electron interaction (EEI) and hopping contributes to conductivity. The temperature dependence of a proton T{sub 1} is classified in three regimes: (a) for T<6 K-relaxation mechanism follows a modified Korringa relation due to EEI and disorder, (b) for 6 K50 K-relaxation is due to the dipolar interaction modulated by the reorientation of the symmetric PF{sub 6} groups following the Bloembergen, Purcell and Pound (BPP) model. The data analysis shows that the Korringa ratio is enhanced by an order of magnitude. The positive and negative MC at T<250 mK is due to the contributions from weak localization and Coulomb-correlated hopping transport, respectively. The role of EEI is observed to be consistent in conductivity, T{sub 1} and MC data, especially at T<1 K.

  12. Magnetic resonance–guided interstitial high-intensity focused ultrasound for brain tumor ablation

    Science.gov (United States)

    MacDonell, Jacquelyn; Patel, Niravkumar; Rubino, Sebastian; Ghoshal, Goutam; Fischer, Gregory; Burdette, E. Clif; Hwang, Roy; Pilitsis, Julie G.

    2018-01-01

    Currently, treatment of brain tumors is limited to resection, chemotherapy, and radiotherapy. Thermal ablation has been recently explored. High-intensity focused ultrasound (HIFU) is being explored as an alternative. Specifically, the authors propose delivering HIFU internally to the tumor with an MRI-guided robotic assistant (MRgRA). The advantage of the authors’ interstitial device over external MRI-guided HIFU (MRgHIFU) is that it allows for conformal, precise ablation and concurrent tissue sampling. The authors describe their workflow for MRgRA HIFU delivery. PMID:29385926

  13. Diagnostic Accuracy of Multiparametric Magnetic Resonance Imaging and Fusion Guided Targeted Biopsy Evaluated by Transperineal Template Saturation Prostate Biopsy for the Detection and Characterization of Prostate Cancer.

    Science.gov (United States)

    Mortezavi, Ashkan; Märzendorfer, Olivia; Donati, Olivio F; Rizzi, Gianluca; Rupp, Niels J; Wettstein, Marian S; Gross, Oliver; Sulser, Tullio; Hermanns, Thomas; Eberli, Daniel

    2018-02-21

    We evaluated the diagnostic accuracy of multiparametric magnetic resonance imaging and multiparametric magnetic resonance imaging/transrectal ultrasound fusion guided targeted biopsy against that of transperineal template saturation prostate biopsy to detect prostate cancer. We retrospectively analyzed the records of 415 men who consecutively presented for prostate biopsy between November 2014 and September 2016 at our tertiary care center. Multiparametric magnetic resonance imaging was performed using a 3 Tesla device without an endorectal coil, followed by transperineal template saturation prostate biopsy with the BiopSee® fusion system. Additional fusion guided targeted biopsy was done in men with a suspicious lesion on multiparametric magnetic resonance imaging, defined as Likert score 3 to 5. Any Gleason pattern 4 was defined as clinically significant prostate cancer. The detection rates of multiparametric magnetic resonance imaging and fusion guided targeted biopsy were compared with the detection rate of transperineal template saturation prostate biopsy using the McNemar test. We obtained a median of 40 (range 30 to 55) and 3 (range 2 to 4) transperineal template saturation prostate biopsy and fusion guided targeted biopsy cores, respectively. Of the 124 patients (29.9%) without a suspicious lesion on multiparametric magnetic resonance imaging 32 (25.8%) were found to have clinically significant prostate cancer on transperineal template saturation prostate biopsy. Of the 291 patients (70.1%) with a Likert score of 3 to 5 clinically significant prostate cancer was detected in 129 (44.3%) by multiparametric magnetic resonance imaging fusion guided targeted biopsy, in 176 (60.5%) by transperineal template saturation prostate biopsy and in 187 (64.3%) by the combined approach. Overall 58 cases (19.9%) of clinically significant prostate cancer would have been missed if fusion guided targeted biopsy had been performed exclusively. The sensitivity of

  14. Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation

    Czech Academy of Sciences Publication Activity Database

    Herynek, V.; Turnovcová, Karolína; Veverka, Pavel; Dědourková, T.; Žvátora, P.; Jendelová, Pavla; Gálisová, A.; Kosinová, L.; Jiráková, Klára; Syková, Eva

    2016-01-01

    Roč. 11, č. 2016 (2016), s. 3801-3811 E-ISSN 1178-2013 R&D Projects: GA MPO FR-TI3/521; GA MŠk(CZ) LO1309 Institutional support: RVO:68378041 ; RVO:68378271 Keywords : perovskite nanoparticles * hyperthermia * high-frequency magnetic field Subject RIV: FP - Other Medical Disciplines; BM - Solid Matter Physics ; Magnetism (FZU-D) Impact factor: 4.300, year: 2016

  15. Driving magnetic turbulence using flux ropes in a moderate guide field linear system

    Science.gov (United States)

    Brookhart, Matthew I.; Stemo, Aaron; Waleffe, Roger; Forest, Cary B.

    2017-12-01

    We present a series of experiments on novel, line-tied plasma geometries as a study of the generation of chaos and turbulence in line-tied systems. Plasma production and the injection scale for magnetic energy is provided by spatially discrete plasma guns that inject both plasma and current. The guns represent a technique for controlling the injection scale of magnetic energy. A two-dimensional (2-D) array of magnetic probes provides spatially resolved time histories of the magnetic fluctuations at a single cross-section of the experimental cylinder, allowing simultaneous spatial measurements of chaotic and turbulent behaviour. The first experiment shows chaotic fluctuations and self-organization in a hollow-current line-tied screw pinch. These dynamics is modulated primarily by the applied magnetic field and weakly by the plasma current and safety factor. The second experiment analyses the interactions of multiple line-tied flux ropes. The flux ropes all exhibit chaotic behaviour, and under certain conditions develop an inverse cascade to larger scales and a turbulent inertial range with magnetic energy ( ) related to perpendicular wave number ( \\bot $ ) as \\bot -2.5\\pm 0.5$ .

  16. Enhancement of the guide field during the current sheet formation in the three-dimensional magnetic configuration with an X line

    International Nuclear Information System (INIS)

    Frank, Anna; Bugrov, Sergey; Markov, Vladimir

    2009-01-01

    Results are presented from studies of the formation of current sheets during exciting a current aligned with the X line of the 3D magnetic configuration, in the CS-3D device. Enhancement of the guide field (parallel to the X line) was directly observed for the first time, on the basis of magnetic measurements. After the current sheet formation, the guide field inside the sheet exceeds its initial value, as well as the field outside. It is convincingly demonstrated that an enhancement of the guide field is due to its transportation by plasma flows on the early stage of the sheet formation. The in-plane plasma currents, which produce the excess guide field, are comparable to the total current along the X line that initiates the sheet itself.

  17. Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine

    Science.gov (United States)

    2012-01-01

    Background Real-time cardiovascular magnetic resonance (rtCMR) is considered attractive for guiding TAVI. Owing to an unlimited scan plane orientation and an unsurpassed soft-tissue contrast with simultaneous device visualization, rtCMR is presumed to allow safe device navigation and to offer optimal orientation for precise axial positioning. We sought to evaluate the preclinical feasibility of rtCMR-guided transarterial aortic valve implatation (TAVI) using the nitinol-based Medtronic CoreValve bioprosthesis. Methods rtCMR-guided transfemoral (n = 2) and transsubclavian (n = 6) TAVI was performed in 8 swine using the original CoreValve prosthesis and a modified, CMR-compatible delivery catheter without ferromagnetic components. Results rtCMR using TrueFISP sequences provided reliable imaging guidance during TAVI, which was successful in 6 swine. One transfemoral attempt failed due to unsuccessful aortic arch passage and one pericardial tamponade with subsequent death occurred as a result of ventricular perforation by the device tip due to an operating error, this complication being detected without delay by rtCMR. rtCMR allowed for a detailed, simultaneous visualization of the delivery system with the mounted stent-valve and the surrounding anatomy, resulting in improved visualization during navigation through the vasculature, passage of the aortic valve, and during placement and deployment of the stent-valve. Post-interventional success could be confirmed using ECG-triggered time-resolved cine-TrueFISP and flow-sensitive phase-contrast sequences. Intended valve position was confirmed by ex-vivo histology. Conclusions Our study shows that rtCMR-guided TAVI using the commercial CoreValve prosthesis in conjunction with a modified delivery system is feasible in swine, allowing improved procedural guidance including immediate detection of complications and direct functional assessment with reduction of radiation and omission of contrast media. PMID:22453050

  18. Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine.

    Science.gov (United States)

    Kahlert, Philipp; Parohl, Nina; Albert, Juliane; Schäfer, Lena; Reinhardt, Renate; Kaiser, Gernot M; McDougall, Ian; Decker, Brad; Plicht, Björn; Erbel, Raimund; Eggebrecht, Holger; Ladd, Mark E; Quick, Harald H

    2012-03-27

    Real-time cardiovascular magnetic resonance (rtCMR) is considered attractive for guiding TAVI. Owing to an unlimited scan plane orientation and an unsurpassed soft-tissue contrast with simultaneous device visualization, rtCMR is presumed to allow safe device navigation and to offer optimal orientation for precise axial positioning. We sought to evaluate the preclinical feasibility of rtCMR-guided transarterial aortic valve implatation (TAVI) using the nitinol-based Medtronic CoreValve bioprosthesis. rtCMR-guided transfemoral (n = 2) and transsubclavian (n = 6) TAVI was performed in 8 swine using the original CoreValve prosthesis and a modified, CMR-compatible delivery catheter without ferromagnetic components. rtCMR using TrueFISP sequences provided reliable imaging guidance during TAVI, which was successful in 6 swine. One transfemoral attempt failed due to unsuccessful aortic arch passage and one pericardial tamponade with subsequent death occurred as a result of ventricular perforation by the device tip due to an operating error, this complication being detected without delay by rtCMR. rtCMR allowed for a detailed, simultaneous visualization of the delivery system with the mounted stent-valve and the surrounding anatomy, resulting in improved visualization during navigation through the vasculature, passage of the aortic valve, and during placement and deployment of the stent-valve. Post-interventional success could be confirmed using ECG-triggered time-resolved cine-TrueFISP and flow-sensitive phase-contrast sequences. Intended valve position was confirmed by ex-vivo histology. Our study shows that rtCMR-guided TAVI using the commercial CoreValve prosthesis in conjunction with a modified delivery system is feasible in swine, allowing improved procedural guidance including immediate detection of complications and direct functional assessment with reduction of radiation and omission of contrast media.

  19. Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine

    Directory of Open Access Journals (Sweden)

    Kahlert Philipp

    2012-03-01

    Full Text Available Abstract Background Real-time cardiovascular magnetic resonance (rtCMR is considered attractive for guiding TAVI. Owing to an unlimited scan plane orientation and an unsurpassed soft-tissue contrast with simultaneous device visualization, rtCMR is presumed to allow safe device navigation and to offer optimal orientation for precise axial positioning. We sought to evaluate the preclinical feasibility of rtCMR-guided transarterial aortic valve implatation (TAVI using the nitinol-based Medtronic CoreValve bioprosthesis. Methods rtCMR-guided transfemoral (n = 2 and transsubclavian (n = 6 TAVI was performed in 8 swine using the original CoreValve prosthesis and a modified, CMR-compatible delivery catheter without ferromagnetic components. Results rtCMR using TrueFISP sequences provided reliable imaging guidance during TAVI, which was successful in 6 swine. One transfemoral attempt failed due to unsuccessful aortic arch passage and one pericardial tamponade with subsequent death occurred as a result of ventricular perforation by the device tip due to an operating error, this complication being detected without delay by rtCMR. rtCMR allowed for a detailed, simultaneous visualization of the delivery system with the mounted stent-valve and the surrounding anatomy, resulting in improved visualization during navigation through the vasculature, passage of the aortic valve, and during placement and deployment of the stent-valve. Post-interventional success could be confirmed using ECG-triggered time-resolved cine-TrueFISP and flow-sensitive phase-contrast sequences. Intended valve position was confirmed by ex-vivo histology. Conclusions Our study shows that rtCMR-guided TAVI using the commercial CoreValve prosthesis in conjunction with a modified delivery system is feasible in swine, allowing improved procedural guidance including immediate detection of complications and direct functional assessment with reduction of radiation and omission of contrast media.

  20. Magnetic resonance imaging guided reirradiation of recurrent and second primary head and neck cancer

    Directory of Open Access Journals (Sweden)

    Allen M. Chen, MD

    2017-04-01

    Conclusions: Our preliminary findings show that reirradiation with MRI guided radiation therapy results in effective disease control with relatively low morbidity for patients with recurrent and second primary cancers of the head and neck. The superior soft tissue resolution of the MRI scans that were used for planning and delivery has the potential to improve the therapeutic ratio.

  1. New experimental perspectives for soft x-ray absorption spectroscopies at ultra-low temperatures below 50 mK and in high magnetic fields up to 7 T

    International Nuclear Information System (INIS)

    Beeck, T.; Baev, I.; Gieschen, S.; Meyer, H.; Meyer, S.; Palutke, S.; Martins, M.; Feulner, P.; Uhlig, K.; Wurth, W.

    2016-01-01

    A new ultra-low temperature experiment including a superconducting vector magnet has been developed for soft x-ray absorption spectroscopy experiments at third generation synchrotron light sources. The sample is cooled below 50 mK by a cryogen free "3He-"4He dilution refrigerator. At the same time, magnetic fields of up to ±7 T in the horizontal direction and ±0.5 T in the vertical direction can be applied by a superconducting vector magnet. The setup allows to study ex situ and in situ prepared samples, offered by an attached UHV preparation chamber with load lock. The transfer of the prepared samples between the preparation section and the dilution refrigerator is carried out under cryogenic temperatures. First commissioning studies have been carried out at the Variable Polarization XUV Beamline P04 at PETRA III and the influence of the incident photon beam to the sample temperature has been studied.

  2. Imaging of foreign bodies in the face and ultrasound guided surgical removal; Diagnostico por imagem de corpos estranhos da face e retirada cirurgica guiada por ultra-sonografia

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Claudio Marcio Amaral de Oliveira; Gambin, Moises; Ribeiro, Erica Barreiros; Amarante Junior, Jose Luiz de Medeiros [Hospital Naval Marcilio Dias, Rio de Janeiro, RJ (Brazil)]. E-mail: cmaol@br.inter.net; cmaolima@hotmail.com; Monteiro, Alexandra Maria Vieira [Pontificia Univ. Catolica do Rio de Janeiro (PUC/Rio), RJ (Brazil). Curso de Pos-Graduacao em Radiologia

    2006-10-15

    The identification and surgical removal of foreign bodies is a complex procedure in medical practice, principally when the involved material is radiolucent. The technological advent of the ultrasonography equipment comes enlarging the field of application of this method more and more, in medical practice. The authors describe a case of an ultrasound guided surgical removal of glass fragments from the face of a patient. The foreign bodies were previously diagnosed by ultrasound and computed tomography. The guided technic showed secure, less invasive and efficient, allowing the retreat of all the fragments. (author)

  3. Cardiovascular Magnetic Resonance in Cardiology Practice: A Concise Guide to Image Acquisition and Clinical Interpretation.

    Science.gov (United States)

    Valbuena-López, Silvia; Hinojar, Rocío; Puntmann, Valentina O

    2016-02-01

    Cardiovascular magnetic resonance plays an increasingly important role in routine cardiology clinical practice. It is a versatile imaging modality that allows highly accurate, broad and in-depth assessment of cardiac function and structure and provides information on pertinent clinical questions in diseases such as ischemic heart disease, nonischemic cardiomyopathies, and heart failure, as well as allowing unique indications, such as the assessment and quantification of myocardial iron overload or infiltration. Increasing evidence for the role of cardiovascular magnetic resonance, together with the spread of knowledge and skill outside expert centers, has afforded greater access for patients and wider clinical experience. This review provides a snapshot of cardiovascular magnetic resonance in modern clinical practice by linking image acquisition and postprocessing with effective delivery of the clinical meaning. Copyright © 2015 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  4. Danish Ultras

    DEFF Research Database (Denmark)

    Havelund, Jonas; Joern, Lise; Rasmussen, Kristian

    2012-01-01

    It is well documented that knowledge of supporter culture is crucial when assessing the risk of disorder at football matches and thereby ensuring a balanced approach by police and stewards (Stott & Pearson 2007). Both within Denmark and internationally, there is a weak understanding of risk suppo....... The article aims to create knowledge concerning ultra supporter culture with the purpose of gaining the information necessary for building differentiated and balanced action on the part of the police and security services....

  5. Hitchhiker'S Guide to Voxel Segmentation for Partial Volume Correction of in Vivo Magnetic Resonance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Scott Quadrelli

    2016-01-01

    Full Text Available Partial volume effects have the potential to cause inaccuracies when quantifying metabolites using proton magnetic resonance spectroscopy (MRS. In order to correct for cerebrospinal fluid content, a spectroscopic voxel needs to be segmented according to different tissue contents. This article aims to detail how automated partial volume segmentation can be undertaken and provides a software framework for researchers to develop their own tools. While many studies have detailed the impact of partial volume correction on proton magnetic resonance spectroscopy quantification, there is a paucity of literature explaining how voxel segmentation can be achieved using freely available neuroimaging packages.

  6. Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

    Energy Technology Data Exchange (ETDEWEB)

    Weygand, Joseph, E-mail: jw2899@columbia.edu [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Fuller, Clifton David [The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Ibbott, Geoffrey S. [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Mohamed, Abdallah S.R. [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Department of Clinical Oncology and Nuclear Medicine, Alexandria University, Alexandria (Egypt); Ding, Yao [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Yang, Jinzhong [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Hwang, Ken-Pin [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Wang, Jihong [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States)

    2016-07-15

    Because magnetic resonance imaging–guided radiation therapy (MRIgRT) offers exquisite soft tissue contrast and the ability to image tissues in arbitrary planes, the interest in this technology has increased dramatically in recent years. However, intrinsic geometric distortion stemming from both the system hardware and the magnetic properties of the patient affects MR images and compromises the spatial integrity of MRI-based radiation treatment planning, given that for real-time MRIgRT, precision within 2 mm is desired. In this article, we discuss the causes of geometric distortion, describe some well-known distortion correction algorithms, and review geometric distortion measurements from 12 studies, while taking into account relevant imaging parameters. Eleven of the studies reported phantom measurements quantifying system-dependent geometric distortion, while 2 studies reported simulation data quantifying magnetic susceptibility–induced geometric distortion. Of the 11 studies investigating system-dependent geometric distortion, 5 reported maximum measurements less than 2 mm. The simulation studies demonstrated that magnetic susceptibility–induced distortion is typically smaller than system-dependent distortion but still nonnegligible, with maximum distortion ranging from 2.1 to 2.6 mm at a field strength of 1.5 T. As expected, anatomic landmarks containing interfaces between air and soft tissue had the largest distortions. The evidence indicates that geometric distortion reduces the spatial integrity of MRI-based radiation treatment planning and likely diminishes the efficacy of MRIgRT. Better phantom measurement techniques and more effective distortion correction algorithms are needed to achieve the desired spatial precision.

  7. Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

    International Nuclear Information System (INIS)

    Weygand, Joseph; Fuller, Clifton David; Ibbott, Geoffrey S.; Mohamed, Abdallah S.R.; Ding, Yao; Yang, Jinzhong; Hwang, Ken-Pin; Wang, Jihong

    2016-01-01

    Because magnetic resonance imaging–guided radiation therapy (MRIgRT) offers exquisite soft tissue contrast and the ability to image tissues in arbitrary planes, the interest in this technology has increased dramatically in recent years. However, intrinsic geometric distortion stemming from both the system hardware and the magnetic properties of the patient affects MR images and compromises the spatial integrity of MRI-based radiation treatment planning, given that for real-time MRIgRT, precision within 2 mm is desired. In this article, we discuss the causes of geometric distortion, describe some well-known distortion correction algorithms, and review geometric distortion measurements from 12 studies, while taking into account relevant imaging parameters. Eleven of the studies reported phantom measurements quantifying system-dependent geometric distortion, while 2 studies reported simulation data quantifying magnetic susceptibility–induced geometric distortion. Of the 11 studies investigating system-dependent geometric distortion, 5 reported maximum measurements less than 2 mm. The simulation studies demonstrated that magnetic susceptibility–induced distortion is typically smaller than system-dependent distortion but still nonnegligible, with maximum distortion ranging from 2.1 to 2.6 mm at a field strength of 1.5 T. As expected, anatomic landmarks containing interfaces between air and soft tissue had the largest distortions. The evidence indicates that geometric distortion reduces the spatial integrity of MRI-based radiation treatment planning and likely diminishes the efficacy of MRIgRT. Better phantom measurement techniques and more effective distortion correction algorithms are needed to achieve the desired spatial precision.

  8. Targeted Vessel Ablation for More Efficient Magnetic Resonance-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids

    Energy Technology Data Exchange (ETDEWEB)

    Voogt, Marianne J., E-mail: m.voogt@umcutrecht.nl [University Medical Center Utrecht, Department of Radiology (Netherlands); Stralen, Marijn van [University Medical Center Utrecht, Image Sciences Institute (Netherlands); Ikink, Marlijne E. [University Medical Center Utrecht, Department of Radiology (Netherlands); Deckers, Roel; Vincken, Koen L.; Bartels, Lambertus W. [University Medical Center Utrecht, Image Sciences Institute (Netherlands); Mali, Willem P. Th. M.; Bosch, Maurice A. A. J. van den [University Medical Center Utrecht, Department of Radiology (Netherlands)

    2012-10-15

    Purpose: To report the first clinical experience with targeted vessel ablation during magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) treatment of symptomatic uterine fibroids. Methods: Pretreatment T1-weighted contrast-enhanced magnetic resonance angiography was used to create a detailed map of the uterine arteries and feeding branches to the fibroids. A three-dimensional overlay of the magnetic resonance angiography images was registered on 3D T2-weighted pretreatment imaging data. Treatment was focused primarily on locations where supplying vessels entered the fibroid. Patients were followed 6 months after treatment with a questionnaire to assess symptoms and quality of life (Uterine Fibroid Symptom and Quality of Life) and magnetic resonance imaging to quantify shrinkage of fibroid volumes. Results: In two patients, three fibroids were treated with targeted vessel ablation during MR-HIFU. The treatments resulted in almost total fibroid devascularization with nonperfused volume to total fibroid volume ratios of 84, 68, and 86%, respectively, of treated fibroids. The predicted ablated volumes during MR-HIFU in patients 1 and 2 were 45, 40, and 82 ml, respectively, while the nonperfused volumes determined immediately after treatment were 195, 92, and 190 ml respectively, which is 4.3 (patient 1) and 2.3 (patient 2) times higher than expected based on the thermal dose distribution. Fibroid-related symptoms reduced after treatment, and quality of life improved. Fibroid volume reduction ranged 31-59% at 6 months after treatment. Conclusion: Targeted vessel ablation during MR-HIFU allowed nearly complete fibroid ablation in both patients. This technique may enhance the use of MR-HIFU for fibroid treatment in clinical practice.

  9. SMTMS - SM18 Magnet Tests Management System: a Brief User Guide for Operation

    CERN Document Server

    Chohan, N; CERN. Geneva. AB Department

    2004-01-01

    As the number of magnets to be tested under cryogenic conditions increased during the course of 2003, it was clear that a versatile computer-based tool was urgently required for keeping track of all the necessary tests that were carried out for each magnet as well as the outcome of the tests. It was also essential to keep track of the times taken during different phases in magnet preparation for the tests, including Cryogenic connections, cool-downs, warm ups and so forth. SMTMS uses the CERN provided backbone in Web based services and Access database to fulfil these urgent needs and was successfully made operational within a very short time. It has considerably eased & simplified the work in operation for cold testing the magnets with a few permanent core operational staff and a considerably large number of rotational personnel of short duration. This is because SMTMS is now the exclusive & unique Web-based tool to manage the tests and collate the essential electrical characterisation and quench resu...

  10. TU-H-BRA-02: The Physics of Magnetic Field Isolation in a Novel Compact Linear Accelerator Based MRI-Guided Radiation Therapy System

    International Nuclear Information System (INIS)

    Low, D; Mutic, S; Shvartsman, S; Chmielewski, T; Fought, G; Sharma, A; Dempsey, J

    2016-01-01

    Purpose: To develop a method for isolating the MRI magnetic field from field-sensitive linear accelerator components at distances close to isocenter. Methods: A MRI-guided radiation therapy system has been designed that integrates a linear accelerator with simultaneous MR imaging. In order to accomplish this, the magnetron, port circulator, radiofrequency waveguide, gun driver, and linear accelerator needed to be placed in locations with low magnetic fields. The system was also required to be compact, so moving these components far from the main magnetic field and isocenter was not an option. The magnetic field sensitive components (exclusive of the waveguide) were placed in coaxial steel sleeves that were electrically and mechanically isolated and whose thickness and placement were optimized using E&M modeling software. Six sets of sleeves were placed 60° apart, 85 cm from isocenter. The Faraday effect occurs when the direction of propagation is parallel to the magnetic RF field component, rotating the RF polarization, subsequently diminishing RF power. The Faraday effect was avoided by orienting the waveguides such that the magnetic field RF component was parallel to the magnetic field. Results: The magnetic field within the shields was measured to be less than 40 Gauss, significantly below the amount needed for the magnetron and port circulator. Additional mu-metal was employed to reduce the magnetic field at the linear accelerator to less than 1 Gauss. The orientation of the RF waveguides allowed the RT transport with minimal loss and reflection. Conclusion: One of the major challenges in designing a compact linear accelerator based MRI-guided radiation therapy system, that of creating low magnetic field environments for the magnetic-field sensitive components, has been solved. The measured magnetic fields are sufficiently small to enable system integration. This work supported by ViewRay, Inc.

  11. TU-H-BRA-02: The Physics of Magnetic Field Isolation in a Novel Compact Linear Accelerator Based MRI-Guided Radiation Therapy System

    Energy Technology Data Exchange (ETDEWEB)

    Low, D [UCLA, Los Angeles, CA (United States); Mutic, S [Washington University School of Medicine, Saint Louis, MO (United States); Shvartsman, S; Chmielewski, T; Fought, G; Sharma, A; Dempsey, J [ViewRay, Inc., Oakwood Village, OH (United States)

    2016-06-15

    Purpose: To develop a method for isolating the MRI magnetic field from field-sensitive linear accelerator components at distances close to isocenter. Methods: A MRI-guided radiation therapy system has been designed that integrates a linear accelerator with simultaneous MR imaging. In order to accomplish this, the magnetron, port circulator, radiofrequency waveguide, gun driver, and linear accelerator needed to be placed in locations with low magnetic fields. The system was also required to be compact, so moving these components far from the main magnetic field and isocenter was not an option. The magnetic field sensitive components (exclusive of the waveguide) were placed in coaxial steel sleeves that were electrically and mechanically isolated and whose thickness and placement were optimized using E&M modeling software. Six sets of sleeves were placed 60° apart, 85 cm from isocenter. The Faraday effect occurs when the direction of propagation is parallel to the magnetic RF field component, rotating the RF polarization, subsequently diminishing RF power. The Faraday effect was avoided by orienting the waveguides such that the magnetic field RF component was parallel to the magnetic field. Results: The magnetic field within the shields was measured to be less than 40 Gauss, significantly below the amount needed for the magnetron and port circulator. Additional mu-metal was employed to reduce the magnetic field at the linear accelerator to less than 1 Gauss. The orientation of the RF waveguides allowed the RT transport with minimal loss and reflection. Conclusion: One of the major challenges in designing a compact linear accelerator based MRI-guided radiation therapy system, that of creating low magnetic field environments for the magnetic-field sensitive components, has been solved. The measured magnetic fields are sufficiently small to enable system integration. This work supported by ViewRay, Inc.

  12. Magnetic resonance imaging-guided attenuation and scatter corrections in three-dimensional brain positron emission tomography

    CERN Document Server

    Zaidi, H; Slosman, D O

    2003-01-01

    Reliable attenuation correction represents an essential component of the long chain of modules required for the reconstruction of artifact-free, quantitative brain positron emission tomography (PET) images. In this work we demonstrate the proof of principle of segmented magnetic resonance imaging (MRI)-guided attenuation and scatter corrections in 3D brain PET. We have developed a method for attenuation correction based on registered T1-weighted MRI, eliminating the need of an additional transmission (TX) scan. The MR images were realigned to preliminary reconstructions of PET data using an automatic algorithm and then segmented by means of a fuzzy clustering technique which identifies tissues of significantly different density and composition. The voxels belonging to different regions were classified into air, skull, brain tissue and nasal sinuses. These voxels were then assigned theoretical tissue-dependent attenuation coefficients as reported in the ICRU 44 report followed by Gaussian smoothing and additio...

  13. Successful Magnetic Resonance Imaging-Guided Focused Ultrasound Surgery for Recurrent Uterine Fibroid Previously Treated with Uterine Artery Embolization

    Directory of Open Access Journals (Sweden)

    Sang-Wook Yoon

    2010-01-01

    Full Text Available A 45-year-old premenopausal woman was referred to our clinic due to recurring symptoms of uterine fibroids, nine years after a uterine artery embolization (UAE. At the time of screening, the patient presented with bilateral impairment and narrowing of the uterine arteries, which increased the risk of arterial perforation during repeated UAE procedures. The patient was subsequently referred for magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS treatment. Following the treatment, the patient experienced a significant improvement in symptoms (symptom severity score was reduced from 47 to 12 by 1 year post-treatment. MR images at 3 months showed a 49% decrease in fibroid volume. There were no adverse events during the treatment or the follow-up period. This case suggests that MRgFUS can be an effective treatment option for patients with recurrent fibroids following previous UAE treatment.

  14. Guide to making time-lapse graphics using the facilities of the National Magnetic Fusion Energy Computing Center

    International Nuclear Information System (INIS)

    Munro, J.K. Jr.

    1980-05-01

    The advent of large, fast computers has opened the way to modeling more complex physical processes and to handling very large quantities of experimental data. The amount of information that can be processed in a short period of time is so great that use of graphical displays assumes greater importance as a means of displaying this information. Information from dynamical processes can be displayed conveniently by use of animated graphics. This guide presents the basic techniques for generating black and white animated graphics, with consideration of aesthetic, mechanical, and computational problems. The guide is intended for use by someone who wants to make movies on the National Magnetic Fusion Energy Computing Center (NMFECC) CDC-7600. Problems encountered by a geographically remote user are given particular attention. Detailed information is given that will allow a remote user to do some file checking and diagnosis before giving graphics files to the system for processing into film in order to spot problems without having to wait for film to be delivered. Source listings of some useful software are given in appendices along with descriptions of how to use it. 3 figures, 5 tables

  15. Magnetic resonance imaging guided transatrial electrophysiological studies in swine using active catheter tracking - experience with 14 cases

    Energy Technology Data Exchange (ETDEWEB)

    Grothoff, Matthias; Gutberlet, Matthias [University of Leipzig - Heart Center, Department of Radiology, Leipzig (Germany); Hindricks, Gerhard; Sommer, Philipp; Hilbert, Sebastian [University of Leipzig - Heart Center, Department of Electrophysiology, Leipzig (Germany); Fleiter, Christian [Helios Klinikum Berlin-Buch, Department of Orthopaedic Surgery, Berlin (Germany); Schnackenburg, Bernhard [Philips Healthcare, Hamburg (Germany); Weiss, Steffen; Krueger, Sascha [Philips Innovative Technologies, Hamburg (Germany); Piorkowski, Christopher; Gaspar, Thomas [University of Dresden - Heart Center, Department of Electrophysiology, Dresden (Germany); Wedan, Steve; Lloyd, Thomas [Imricor Medical Systems, Burnsville, MN (United States)

    2017-05-15

    To evaluate the feasibility of performing comprehensive Cardiac Magnetic resonance (CMR) guided electrophysiological (EP) interventions in a porcine model encompassing left atrial access. After introduction of two femoral sheaths 14 swine (41 ± 3.6 kg) were transferred to a 1.5 T MR scanner. A three-dimensional whole-heart sequence was acquired followed by segmentation and the visualization of all heart chambers using an image-guidance platform. Two MR conditional catheters were inserted. The interventional protocol consisted of intubation of the coronary sinus, activation mapping, transseptal left atrial access (n = 4), generation of ablation lesions and eventually ablation of the atrioventricular (AV) node. For visualization of the catheter tip active tracking was used. Catheter positions were confirmed by passive real-time imaging. Total procedure time was 169 ± 51 minutes. The protocol could be completed in 12 swine. Two swine died from AV-ablation induced ventricular fibrillation. Catheters could be visualized and navigated under active tracking almost exclusively. The position of the catheter tips as visualized by active tracking could reliably be confirmed with passive catheter imaging. Comprehensive CMR-guided EP interventions including left atrial access are feasible in swine using active catheter tracking. (orig.)

  16. Randomized trial for superiority of high field strength intra-operative magnetic resonance imaging guided resection in pituitary surgery.

    Science.gov (United States)

    Tandon, Vivek; Raheja, Amol; Suri, Ashish; Chandra, P Sarat; Kale, Shashank S; Kumar, Rajinder; Garg, Ajay; Kalaivani, Mani; Pandey, Ravindra M; Sharma, Bhawani S

    2017-03-01

    Till date there are no randomized trials to suggest the superiority of intra-operative magnetic resonance imaging (IOMRI) guided trans-sphenoidal pituitary resection over two dimensional fluoroscopic (2D-F) guided resections. We conducted this trial to establish the superiority of IOMRI in pituitary surgery. Primary objective was to compare extent of tumor resection between the two study arms. It was a prospective, randomized, outcome assessor and statistician blinded, two arm (A: IOMRI, n=25 and B: 2D-F, n=25), parallel group clinical trial. 4 patients from IOMRI group cross-over to 2D-F group and were consequently analyzed in latter group, based on modified intent to treat method. A total of 50 patients were enrolled till completion of trial (n=25 in each study arm). Demographic profile and baseline parameters were comparable among the two arms (p>0.05) except for higher number of endoscopic procedures and experienced neurosurgeons (>10years) in arm B (p=0.02, 0.002 respectively). Extent of resection was similar in both study arms (A, 94.9% vs B, 93.6%; p=0.78), despite adjusting for experience of operating surgeon and use of microscope/endoscope for surgical resection. We observed that use of IOMRI helped optimize the extent of resection in 5/20 patients (25%) for pituitary tumor resection in-group A. Present study failed to observe superiorty of IOMRI over conventional 2D-F guided resection in pituitary macroadenoma surgery. By use of this technology, younger surgeons could validate their results intra-operatively and hence could increase EOR without causing any increase in complications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. High concordance of findings obtained from transgluteal magnetic resonance imaging - and transrectal ultrasonography-guided biopsy as compared with prostatectomy specimens.

    Science.gov (United States)

    Steurer, Stefan; Rico, Sebastian Dwertmann; Simon, Ronald; Minner, Sarah; Tsourlakis, Maria Christina; Krech, Till; Koop, Christina; Graefen, Markus; Heinzer, Hans; Adam, Meike; Huland, Hartwig; Schlomm, Thorsten; Sauter, Guido; Lumiani, Agron

    2017-09-01

    To determine the utility of our transgluteal magnetic resonance imaging (MRI)-guided prostate biopsy approach. A total of 960 biopsy series, taken within the period of 1 year, were evaluated, including 301 MRI-guided and 659 transrectal ultrasonography (TRUS)-guided biopsies. The positivity rate and proportion of high grade cancers were significantly higher in MRI-guided than in TRUS-guided biopsies. Of 301 MRI-guided biopsies, 65.4% contained cancer while 57.2% of 659 TRUS biopsies contained cancer (P = 0.016). Gleason grade 3 + 3 = 6 disease was observed in 16.8% of 197 MRI-guided and in 36.1% of 377 TRUS-guided biopsies (P guided biopsies. In all cancers, the mean cancer surface area was 64.8 ± 51.6 mm 2 in MRI-guided biopsies as compared with 23.0 ± 31.4 mm 2 in non-MRI-guided biopsies (P guided biopsy was highest in Gleason grade 3 + 3 = 6 cancers (20.9 ± 27.9 vs 5.1 ± 10.2 mm 2 ; P guided and in 170 patients with non-MRI-guided biopsies. This comparison showed a very high but almost identical concordance of TRUS- and MRI-guided biopsies with the prostatectomy specimen findings. With both approaches, undetected high-risk cancers were present in ~10% of patients with low-risk biopsy results. A significant difference was observed, however, in the proportion of patients who had clinically insignificant cancers and who underwent surgery. The proportion of patients with Gleason grade 3 + 3 = 6 carcinoma in their prostatectomy specimen was 11.2% in the post-TRUS biopsy cohort, but only 2.5% in the post-MRI biopsy cohort (P = 0.021). MRI-guided transgluteal prostate biopsy has a high detection rate for high-risk carcinomas, while the risk of detecting clinically insignificant carcinomas appears to be reduced. This may by itself lead to a reduction of unnecessary prostatectomies. Overtreatment may be further avoided by better applicability of molecular testing to MRI-guided biopsies because of the excessive amount of tissue available for analysis, especially in

  18. High-resolution structural studies of ultra-thin magnetic, transition metal overlayers and two-dimensional transition metal oxides using synchrotron radiation

    International Nuclear Information System (INIS)

    Kellar, S.A.; Lawrence Berkeley National Lab., CA

    1997-05-01

    This thesis report the surface-structure determination of three, ultra-thin magnetic transition-metal films, Fe/Au(100), Mn/Ni(100), and Mn/Cu(100) using Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) and photoelectron holography. These structural studies are the first to use non-s initial states in the ARPEFS procedure. This thesis also reports an ARPEFS surface-structure determination of a two-dimensional transition-metal oxide, [(1 x 1)O/W(110)] x 12. The authors have analyzed the ARPFES signal from the Au 4f 7/5 core level of the Au(1 ML)/Fe(15 ML)/Au(100) system. The analysis shows that the Fe grows layer by layer with one monolayer of gold, acting as a surfactant, remaining on top of the growing Fe layers. These surface gold atoms sit in the four-fold hollow site, 1.67 ± 0.02 A above the iron surface. The grown Fe layer is very much like the bulk, bcc iron, with an interlayer spacing of 1.43 ± 0.03 A. Analysis of the Mn 3p ARPEFS signals from c(2 x 2)Mn/Ni(100) and c(2 x 2)Mn/Cu(100) shows that the Mn forms highly corrugated surface alloys. The corrugation of the Mn/Ni(100) and Mn/Cu(100) systems are 0.24 ± 0.02 A and 0.30 ± 0.04 A respectively. In both cases the Mn is sticking above the plane of the surface substrate atoms. For the Mn/Ni(100) system the first layer Ni is contracted 4% from the bulk value. The Mn/Cu(100) system shows bulk spacing for the substrate Cu. Photoelectron holography shows that the Mn/Ni interface is very abrupt with very little Mn leaking into the second layer, while the Mn/Cu(100) case has a significant amount of Mn leaking into the second layer. A new, five-element electrostatic electron lens was developed for hemispherical electron-energy analyzers. This lens system can be operated at constant transverse or constants angular magnification, and has been optimized for use with the very small photon-spot sizes. Improvements to the hemispherical electron-energy analyzer are also discussed

  19. High-resolution structural studies of ultra-thin magnetic, transition metal overlayers and two-dimensional transition metal oxides using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kellar, S.A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Advanced Light Source Div.

    1997-05-01

    This thesis report the surface-structure determination of three, ultra-thin magnetic transition-metal films, Fe/Au(100), Mn/Ni(100), and Mn/Cu(100) using Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) and photoelectron holography. These structural studies are the first to use non-s initial states in the ARPEFS procedure. This thesis also reports an ARPEFS surface-structure determination of a two-dimensional transition-metal oxide, [(1 x 1)O/W(110)] x 12. The authors have analyzed the ARPFES signal from the Au 4f{sub 7/5} core level of the Au(1 ML)/Fe(15 ML)/Au(100) system. The analysis shows that the Fe grows layer by layer with one monolayer of gold, acting as a surfactant, remaining on top of the growing Fe layers. These surface gold atoms sit in the four-fold hollow site, 1.67 {+-} 0.02 A above the iron surface. The grown Fe layer is very much like the bulk, bcc iron, with an interlayer spacing of 1.43 {+-} 0.03 A. Analysis of the Mn 3p ARPEFS signals from c(2 x 2)Mn/Ni(100) and c(2 x 2)Mn/Cu(100) shows that the Mn forms highly corrugated surface alloys. The corrugation of the Mn/Ni(100) and Mn/Cu(100) systems are 0.24 {+-} 0.02 A and 0.30 {+-} 0.04 A respectively. In both cases the Mn is sticking above the plane of the surface substrate atoms. For the Mn/Ni(100) system the first layer Ni is contracted 4% from the bulk value. The Mn/Cu(100) system shows bulk spacing for the substrate Cu. Photoelectron holography shows that the Mn/Ni interface is very abrupt with very little Mn leaking into the second layer, while the Mn/Cu(100) case has a significant amount of Mn leaking into the second layer. A new, five-element electrostatic electron lens was developed for hemispherical electron-energy analyzers. This lens system can be operated at constant transverse or constants angular magnification, and has been optimized for use with the very small photon-spot sizes. Improvements to the hemispherical electron-energy analyzer are also discussed.

  20. Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

    OpenAIRE

    Sadeh, Boaz; Yovel, Galit

    2014-01-01

    Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior...

  1. Focusing electrode and coaxial reflector used for reducing the guiding magnetic field of the Ku-band foilless transit-time oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Ling, Junpu; Zhang, Jiande; He, Juntao, E-mail: hejuntao12@163.com; Wang, Lei; Deng, Bingfang [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-08-15

    Based on the theoretical analysis of the intense relativistic electron beam propagation in the coaxial drift-tube, a focusing electrode and a coaxial reflector is proposed to lessen the demand of the coaxial Ku-band foilless transit-time oscillator (TTO) for the guiding magnetic field. Moreover, a Ku-band TTO with the focusing electrode and the coaxial reflector is designed and studied by particle in cell simulation. When the diode voltage is 390 kV, the beam current 7.8 kA, and the guiding magnetic field is only 0.3 T, the device can output 820 MW microwave pulse at 14.25 GHz by means of the simulation. However, for the device without them, the output power is only 320 MW. The primary experiments are also carried out. When the guiding magnetic field is 0.3 T, the output power of the device with the focusing electrode and the coaxial reflector is double that of the one without them. The simulation and experimental results prove that the focusing electrode and the coaxial reflector are effective on reducing the guiding magnetic field of the device.

  2. Extended Remediation of Sleep Deprived-Induced Working Memory Deficits Using fMRI-guided Transcranial Magnetic Stimulation

    Science.gov (United States)

    Luber, Bruce; Steffener, Jason; Tucker, Adrienne; Habeck, Christian; Peterchev, Angel V.; Deng, Zhi-De; Basner, Robert C.; Stern, Yaakov; Lisanby, Sarah H.

    2013-01-01

    Study Objectives: We attempted to prevent the development of working memory (WM) impairments caused by sleep deprivation using fMRI-guided repetitive transcranial magnetic stimulation (rTMS). Novel aspects of our fMRI-guided rTMS paradigm included the use of sophisticated covariance methods to identify functional networks in imaging data, and the use of fMRI-targeted rTMS concurrent with task performance to modulate plasticity effects over a longer term. Design: Between-groups mixed model. Setting: TMS, MRI, and sleep laboratory study. Participants: 27 subjects (13 receiving Active rTMS, and 14 Sham) completed the sleep deprivation protocol, with another 21 (10 Active, 11 Sham) non-sleep deprived subjects run in a second experiment. Interventions: Our previous covariance analysis had identified a network, including occipital cortex, which demonstrated individual differences in resilience to the deleterious effects of sleep deprivation on WM performance. Five Hz rTMS was applied to left lateral occipital cortex while subjects performed a WM task during 4 sessions over the course of 2 days of total sleep deprivation. Measurements and Results: At the end of the sleep deprivation period, Sham sleep deprived subjects exhibited degraded performance in the WM task. In contrast, those receiving Active rTMS did not show the slowing and lapsing typical in sleep deprivation, and instead performed similarly to non- sleep deprived subjects. Importantly, the Active sleep deprivation group showed rTMS-induced facilitation of WM performance a full 18 hours after the last rTMS session. Conclusions: Over the course of sleep deprivation, these results indicate that rTMS applied concurrently with WM task performance affected neural circuitry involved in WM to prevent its full impact. Citation: Luber B; Steffener J; Tucker A; Habeck C; Peterchev AV; Deng ZD; Basner RC; Stern Y; Lisanby SH. Extended remediation of sleep deprived-induced working memory deficits using fMRI-guided

  3. Magnetic particle imaging: advancements and perspectives for real-time in vivo monitoring and image-guided therapy

    Science.gov (United States)

    Pablico-Lansigan, Michele H.; Situ, Shu F.; Samia, Anna Cristina S.

    2013-05-01

    Magnetic particle imaging (MPI) is an emerging biomedical imaging technology that allows the direct quantitative mapping of the spatial distribution of superparamagnetic iron oxide nanoparticles. MPI's increased sensitivity and short image acquisition times foster the creation of tomographic images with high temporal and spatial resolution. The contrast and sensitivity of MPI is envisioned to transcend those of other medical imaging modalities presently used, such as magnetic resonance imaging (MRI), X-ray scans, ultrasound, computed tomography (CT), positron emission tomography (PET) and single photon emission computed tomography (SPECT). In this review, we present an overview of the recent advances in the rapidly developing field of MPI. We begin with a basic introduction of the fundamentals of MPI, followed by some highlights over the past decade of the evolution of strategies and approaches used to improve this new imaging technique. We also examine the optimization of iron oxide nanoparticle tracers used for imaging, underscoring the importance of size homogeneity and surface engineering. Finally, we present some future research directions for MPI, emphasizing the novel and exciting opportunities that it offers as an important tool for real-time in vivo monitoring. All these opportunities and capabilities that MPI presents are now seen as potential breakthrough innovations in timely disease diagnosis, implant monitoring, and image-guided therapeutics.

  4. Magnetic resonance imaging-guided attenuation correction of positron emission tomography data in PET/MRI

    OpenAIRE

    Izquierdo-Garcia, David; Catana, Ciprian

    2016-01-01

    Attenuation correction (AC) is one of the most important challenges in the recently introduced combined positron emission tomography/magnetic resonance imaging (PET/MR) scanners. PET/MR AC (MR-AC) approaches aim to develop methods that allow accurate estimation of the linear attenuation coefficients (LACs) of the tissues and other components located in the PET field of view (FoV). MR-AC methods can be divided into three main categories: segmentation-, atlas- and PET-based. This review aims to...

  5. Role of magnetic resonance imaging in guiding thermal therapies. A brief technical review

    International Nuclear Information System (INIS)

    Kuroda, Kagayaki

    2007-01-01

    For a number of reasons, Magnetic Resonance Imaging (MRI) is a unique tool for interventional use. It has a spatial resolution which is independent of the wavelength of the electromagnetic field used for imaging, has various imaging parameters which are related to the physical properties of the subject; provides a superior soft-tissue contrast; provides freedom in determining the slicing or viewing angle; and it utilizes non-ionizing radiation. This technology offers assistance in therapeutic applications such as lesion identification, treatment planning, device tracking, temperature imaging and treatment evaluation. In this article, the role of MRI in assisting thermal therapy is briefly reviewed from a technical point of view. (author)

  6. SU-E-J-181: Magnetic Resonance Image-Guided Radiation Therapy Workflow: Initial Clinical Experience

    International Nuclear Information System (INIS)

    Green, O; Kashani, R; Santanam, L; Wooten, H; Li, H; Rodriguez, V; Hu, Y; Mutic, S; Hand, T; Victoria, J; Steele, C

    2014-01-01

    Purpose: The aims of this work are to describe the workflow and initial clinical experience treating patients with an MRI-guided radiotherapy (MRIGRT) system. Methods: Patient treatments with a novel MR-IGRT system started at our institution in mid-January. The system consists of an on-board 0.35-T MRI, with IMRT-capable delivery via doubly-focused MLCs on three 60 Co heads. In addition to volumetric MR-imaging, real-time planar imaging is performed during treatment. So far, eleven patients started treatment (six finished), ranging from bladder to lung SBRT. While the system is capable of online adaptive radiotherapy and gating, a conventional workflow was used to start, consisting of volumetric imaging for patient setup using visible tumor, evaluation of tumor motion outside of PTV on cine images, and real-time imaging. Workflow times were collected and evaluated to increase efficiency and evaluate feasibility of adding the adaptive and gating features while maintaining a reasonable patient throughput. Results: For the first month, physicians attended every fraction to provide guidance on identifying the tumor and an acceptable level of positioning and anatomical deviation. Average total treatment times (including setup) were reduced from 55 to 45 min after physician presence was no longer required and the therapists had learned to align patients based on soft-tissue imaging. Presently, the source strengths were at half maximum (7.7K Ci each), therefore beam-on times will be reduced after source replacement. Current patient load is 10 per day, with increase to 25 anticipated in the near future. Conclusion: On-board, real-time MRI-guided RT has been incorporated into clinical use. Treatment times were kept to reasonable lengths while including volumetric imaging, previews of tumor movement, and physician evaluation. Workflow and timing is being continuously evaluated to increase efficiency. In near future, adaptive and gating capabilities of the system will be

  7. Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yanle, E-mail: Hu.Yanle@mayo.edu [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110 and Department of Radiation Oncology, Mayo Clinic in Arizona, Phoenix, Arizona 85054 (United States); Rankine, Leith; Green, Olga L.; Kashani, Rojano; Li, H. Harold; Li, Hua; Rodriguez, Vivian; Santanam, Lakshmi; Wooten, H. Omar; Mutic, Sasa [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110 (United States); Nana, Roger; Shvartsman, Shmaryu; Victoria, James; Dempsey, James F. [ViewRay, Inc., Oakwood Village, Ohio 44146 (United States)

    2015-10-15

    Purpose: To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR-IGRT) system. Methods: The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance. The spatial integrity test was evaluated using a 40.8 × 40.8 × 40.8 cm{sup 3} spatial integrity phantom. MR and computed tomography (CT) images of the phantom were acquired and coregistered. Objects were identified around the surfaces of 20 and 35 cm diameters of spherical volume (DSVs) on both the MR and CT images. Geometric distortion was quantified using deviation in object location between the MR and CT images. The coil SNR test was performed according to the national electrical manufacturers association (NEMA) standards MS-1 and MS-9. The magnetic field homogeneity test was measured using field camera and spectral peak methods. Results: For the ACR tests, the slice position error was less than 0.10 cm, the slice thickness error was less than 0.05 cm, the resolved high-contrast spatial resolution was 0.09 cm, the resolved low-contrast spokes were more than 25, the image intensity uniformity was above 93%, and the percentage ghosting was less than 0.22%. All were within the ACR recommended specifications. The maximum geometric distortions within the 20 and 35 cm DSVs were 0.10 and 0.18 cm for high spatial resolution three-dimensional images and 0.08 and 0.20 cm for high temporal resolution two dimensional cine images based on the distance-to-phantom-center method. The average SNR was 12.0 for the body coil, 42.9 for the combined torso coil, and 44.0 for the combined head and neck coil. Magnetic field homogeneities at gantry angles of 0°, 30°, 60°, 90°, and 120° were 23.55, 20.43, 18.76, 19

  8. Characterization of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy system

    International Nuclear Information System (INIS)

    Hu, Yanle; Rankine, Leith; Green, Olga L.; Kashani, Rojano; Li, H. Harold; Li, Hua; Rodriguez, Vivian; Santanam, Lakshmi; Wooten, H. Omar; Mutic, Sasa; Nana, Roger; Shvartsman, Shmaryu; Victoria, James; Dempsey, James F.

    2015-01-01

    Purpose: To characterize the performance of the onboard imaging unit for the first clinical magnetic resonance image guided radiation therapy (MR-IGRT) system. Methods: The imaging performance characterization included four components: ACR (the American College of Radiology) phantom test, spatial integrity, coil signal to noise ratio (SNR) and uniformity, and magnetic field homogeneity. The ACR phantom test was performed in accordance with the ACR phantom test guidance. The spatial integrity test was evaluated using a 40.8 × 40.8 × 40.8 cm 3 spatial integrity phantom. MR and computed tomography (CT) images of the phantom were acquired and coregistered. Objects were identified around the surfaces of 20 and 35 cm diameters of spherical volume (DSVs) on both the MR and CT images. Geometric distortion was quantified using deviation in object location between the MR and CT images. The coil SNR test was performed according to the national electrical manufacturers association (NEMA) standards MS-1 and MS-9. The magnetic field homogeneity test was measured using field camera and spectral peak methods. Results: For the ACR tests, the slice position error was less than 0.10 cm, the slice thickness error was less than 0.05 cm, the resolved high-contrast spatial resolution was 0.09 cm, the resolved low-contrast spokes were more than 25, the image intensity uniformity was above 93%, and the percentage ghosting was less than 0.22%. All were within the ACR recommended specifications. The maximum geometric distortions within the 20 and 35 cm DSVs were 0.10 and 0.18 cm for high spatial resolution three-dimensional images and 0.08 and 0.20 cm for high temporal resolution two dimensional cine images based on the distance-to-phantom-center method. The average SNR was 12.0 for the body coil, 42.9 for the combined torso coil, and 44.0 for the combined head and neck coil. Magnetic field homogeneities at gantry angles of 0°, 30°, 60°, 90°, and 120° were 23.55, 20.43, 18.76, 19

  9. Magnetic resonance imaging-guided attenuation correction of positron emission tomography data in PET/MRI

    Science.gov (United States)

    Izquierdo-Garcia, David; Catana, Ciprian

    2018-01-01

    Synopsis Attenuation correction (AC) is one of the most important challenges in the recently introduced combined positron emission tomography/magnetic resonance imaging (PET/MR) scanners. PET/MR AC (MR-AC) approaches aim to develop methods that allow accurate estimation of the linear attenuation coefficients (LACs) of the tissues and other components located in the PET field of view (FoV). MR-AC methods can be divided into three main categories: segmentation-, atlas- and PET-based. This review aims to provide a comprehensive list of the state of the art MR-AC approaches as well as their pros and cons. The main sources of artifacts such as body-truncation, metallic implants and hardware correction will be presented. Finally, this review will discuss the current status of MR-AC approaches for clinical applications. PMID:26952727

  10. A practical guide to diagnostic transcranial magnetic stimulation: Report of an IFCN committee

    Science.gov (United States)

    Groppa, S.; Oliviero, A.; Eisen, A.; Quartarone, A.; Cohen, L.G.; Mall, V.; Kaelin-Lang, A.; Mima, T.; Rossi, S.; Thickbroom, G.W.; Rossini, P.M.; Ziemann, U.; Valls-Solé, J.; Siebner, H.R.

    2016-01-01

    Transcranial magnetic stimulation (TMS) is an established neurophysiological tool to examine the integrity of the fast-conducting corticomotor pathways in a wide range of diseases associated with motor dysfunction. This includes but is not limited to patients with multiple sclerosis, amyotrophic lateral sclerosis, stroke, movement disorders, disorders affecting the spinal cord, facial and other cranial nerves. These guidelines cover practical aspects of TMS in a clinical setting. We first discuss the technical and physiological aspects of TMS that are relevant for the diagnostic use of TMS. We then lay out the general principles that apply to a standardized clinical examination of the fast-conducting corticomotor pathways with single-pulse TMS. This is followed by a detailed description of how to examine corticomotor conduction to the hand, leg, trunk and facial muscles in patients. Additional sections cover safety issues, the triple stimulation technique, and neuropediatric aspects of TMS. PMID:22349304

  11. Production ultra propre

    CERN Document Server

    Morvan, Gilles

    2011-01-01

    L'ultra propreté se caractérise par l'absence de particules et la maîtrise de la contamination dans un environnement défini. Largement appliquée dans diverses industries (pharmacie, cosmétiques, dispositifs médicaux, chimie fine, biotechnologies, électronique et secteurs de pointe, agroalimentaire, plasturgie…), la technicité dans ce domaine est élevée, car principalement liée à la maîtrise des différentes sources de contaminations (eau, air ambiant, fluides, etc.). Véritable guide pratique, cet ouvrage détaille les points techniques essentiels pour permettre à l’ingénieur de trouver des solutions adéquates à chaque type de projet. La démarche passe par la rédaction de spécifications rigoureuses pour : - l’eau, essentielle à toutes productions, - les équipements de production ultra propre, - la démarche qualité et environnementale, - la démarche de suivi du projet.

  12. Magnetic resonance-guided regional gene delivery strategy using a tumor stroma-permeable nanocarrier for pancreatic cancer

    Directory of Open Access Journals (Sweden)

    Wang Q

    2015-07-01

    Full Text Available Qingbing Wang,1,2 Jianfeng Li,3 Sai An,3 Yi Chen,1 Chen Jiang,3 Xiaolin Wang1,2 1Department of Interventional Radiology, Zhongshan Hospital, Fudan University, 2Shanghai Institute of Medical Imaging, 3Key Laboratory of Smart Drug Delivery, Ministry of Education, Department of Pharmaceutics, School of Pharmacy, Fudan University, Shanghai, People’s Republic of China Background: Gene therapy is a very promising technology for treatment of pancreatic ductal adenocarcinoma (PDAC. However, its application has been limited by the abundant stromal response in the tumor microenvironment. The aim of this study was to prepare a dendrimer-based gene-free loading vector with high permeability in the tumor stroma and explore an imaging-guided local gene delivery strategy for PDAC to promote the efficiency of targeted gene delivery.Methods: The experimental protocol was approved by the animal ethics committee of Zhongshan Hospital, Fudan University. Third-generation dendrigraft poly-L-lysines was selected as the nanocarrier scaffold, which was modified by cell-penetrating peptides and gadolinium (Gd chelates. DNA plasmids were loaded with these nanocarriers via electrostatic interaction. The cellular uptake and loaded gene expression were examined in MIA PaCa-2 cell lines in vitro. Permeability of the nanoparticles in the tumor stroma and transfected gene distribution in vivo were studied using a magnetic resonance imaging-guided delivery strategy in an orthotopic nude mouse model of PDAC.Results: The nanocarriers were synthesized with a dendrigraft poly-L-lysine to polyethylene glycol to DTPA ratio of 1:3.4:8.3 and a mean diameter of 110.9±7.7 nm. The luciferases were strictly expressed in the tumor, and the luminescence intensity in mice treated by Gd-DPT/plasmid luciferase (1.04×104±9.75×102 p/s/cm2/sr was significantly (P<0.05 higher than in those treated with Gd-DTPA (9.56×102±6.15×10 p/s/cm2/sr and Gd-DP (5.75×103± 7.45×102 p/s/cm2/sr

  13. Where Do Transrectal Ultrasound- and Magnetic Resonance Imaging-guided Biopsies Miss Significant Prostate Cancer?

    DEFF Research Database (Denmark)

    Boesen, Lars; Nørgaard, Nis; Løgager, Vibeke

    2017-01-01

    -guided biopsy (reTRUSbx) and targeted mpMRIbx (image fusion) of any suspicious lesion. Biopsy results were compared and the locations of missed sPCa lesions were registered. Cancer significance was defined as (1) any core with a Gleason score of >6, (2) cancer core involvement of ≥50% and for re......TRUSbx on patient level, and (3) the presence of ≥3 positive cores. RESULTS: Of the 289 patients, prostate cancer was detected in 128 (44%) with 88 (30%) having sPCa. Overall, 165 separate prostate cancer lesions were detected with 100 being sPCa. Of these, mpMRIbx and reTRUSbx detected 90% (90/100) and 68% (68...... TRUSbx and mpMRIbx missed sPCa lesions in specific segments of the prostate. Missed sPCa lesions at repeat biopsy were primarily located anteriorly for TRUSbx and posterolateral midprostatic for mpMRIbx. Localization of these segments may improve biopsy techniques in men undergoing repeat biopsies....

  14. Shoulder Magnetic Resonance Arthrography: A Prospective Randomized Study of Anterior and Posterior Ultrasonography-Guided Contrast Injections

    Energy Technology Data Exchange (ETDEWEB)

    Koivikko, M.P.; Mustonen, A.O.T. (Dept. of Radiology, Helsinki Univ. Central Hospital, Helsinki (Finland))

    2008-10-15

    Background: Magnetic resonance (MR) arthrography is an accurate imaging method for internal shoulder derangements and rotator cuff pathologies. Both anterior and posterior contrast injection techniques, under palpatory, fluoroscopic, or ultrasonographic guidance have been described in the literature. However, clinical comparisons of the injection techniques remain few. Purpose: To compare the performance of anterior and posterior ultrasonography (US)-guided arthrography injections of the shoulder regarding patient discomfort and influence on diagnostic MR reading, and to illustrate the typical artifacts resulting from contrast leakage in the respective techniques. Material and Methods: 43 MR arthrographies were prospectively randomized into anterior and posterior US-guided contrast injections and performed by two radiologists, with the study of artifacts from contrast leakage. Pain from the injections was assessed by a survey utilizing a 100-mm visual analogue scale (VAS). Results: Of the 23 anterior injections, nine caused contrast artifacts in the subscapular tendon, and in three the leakage extended further anteriorly. Of the 20 posterior injections, 12 showed injection artifacts of the rotator cuff, extending outside the cuff in seven. Two of the anterior and none of the posterior artifacts compromised diagnostic quality. In posterior injections, the leakage regularly occurred at the caudal edge of the infraspinatus muscle and was easily distinguishable from rotator cuff tears. All patients completed the pain survey. Mean VAS scores were 25.0 (median 18, SD 22) for anterior, and 25.4 (median 16, SD 25) for posterior injections. The two radiologists achieved different mean VAS scores but closely agreed as to anterior and posterior VAS scores. Conclusion: Arthrography injections were fairly simple to perform under US guidance. Patient discomfort for anterior and posterior injections was equally minor. A tailored approach utilizing anterior or posterior injections

  15. Magnetic Resonance Imaging–Guided versus Surrogate-Based Motion Tracking in Liver Radiation Therapy: A Prospective Comparative Study

    Energy Technology Data Exchange (ETDEWEB)

    Paganelli, Chiara, E-mail: chiara.paganelli@polimi.it [Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano (Italy); Seregni, Matteo; Fattori, Giovanni [Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano (Italy); Summers, Paul [Division of Radiology, Istituto Europeo di Oncologia, Milano (Italy); Bellomi, Massimo [Division of Radiology, Istituto Europeo di Oncologia, Milano (Italy); Department of Health Sciences, Università degli Studi di Milano, Milano (Italy); Baroni, Guido; Riboldi, Marco [Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano (Italy); Bioengineering Unit, CNAO Foundation, Pavia (Italy)

    2015-03-15

    Purpose: This study applied automatic feature detection on cine–magnetic resonance imaging (MRI) liver images in order to provide a prospective comparison between MRI-guided and surrogate-based tracking methods for motion-compensated liver radiation therapy. Methods and Materials: In a population of 30 subjects (5 volunteers plus 25 patients), 2 oblique sagittal slices were acquired across the liver at high temporal resolution. An algorithm based on scale invariant feature transform (SIFT) was used to extract and track multiple features throughout the image sequence. The position of abdominal markers was also measured directly from the image series, and the internal motion of each feature was quantified through multiparametric analysis. Surrogate-based tumor tracking with a state-of-the-art external/internal correlation model was simulated. The geometrical tracking error was measured, and its correlation with external motion parameters was also investigated. Finally, the potential gain in tracking accuracy relying on MRI guidance was quantified as a function of the maximum allowed tracking error. Results: An average of 45 features was extracted for each subject across the whole liver. The multi-parametric motion analysis reported relevant inter- and intrasubject variability, highlighting the value of patient-specific and spatially-distributed measurements. Surrogate-based tracking errors (relative to the motion amplitude) were were in the range 7% to 23% (1.02-3.57mm) and were significantly influenced by external motion parameters. The gain of MRI guidance compared to surrogate-based motion tracking was larger than 30% in 50% of the subjects when considering a 1.5-mm tracking error tolerance. Conclusions: Automatic feature detection applied to cine-MRI allows detailed liver motion description to be obtained. Such information was used to quantify the performance of surrogate-based tracking methods and to provide a prospective comparison with respect to MRI-guided

  16. Factors associated with successful magnetic resonance-guided focused ultrasound treatment: efficiency of acoustic energy delivery through the skull.

    Science.gov (United States)

    Chang, Won Seok; Jung, Hyun Ho; Zadicario, Eyal; Rachmilevitch, Itay; Tlusty, Tal; Vitek, Shuki; Chang, Jin Woo

    2016-02-01

    Magnetic resonance-guided focused ultrasound surgery (MRgFUS) was recently introduced as treatment for movement disorders such as essential tremor and advanced Parkinson's disease (PD). Although deep brain target lesions are successfully generated in most patients, the target area temperature fails to increase in some cases. The skull is one of the greatest barriers to ultrasonic energy transmission. The authors analyzed the skull-related factors that may have prevented an increase in target area temperatures in patients who underwent MRgFUS. The authors retrospectively reviewed data from clinical trials that involved MRgFUS for essential tremor, idiopathic PD, and obsessive-compulsive disorder. Data from 25 patients were included. The relationships between the maximal temperature during treatment and other factors, including sex, age, skull area of the sonication field, number of elements used, skull volume of the sonication field, and skull density ratio (SDR), were determined. Among the various factors, skull volume and SDR exhibited relationships with the maximum temperature. Skull volume was negatively correlated with maximal temperature (p = 0.023, r(2) = 0.206, y = 64.156 - 0.028x, whereas SDR was positively correlated with maximal temperature (p = 0.009, r(2) = 0.263, y = 49.643 + 11.832x). The other factors correlate with the maximal temperature, although some factors showed a tendency to correlate. Some skull-related factors correlated with the maximal target area temperature. Although the number of patients in the present study was relatively small, the results offer information that could guide the selection of MRgFUS candidates.

  17. Numerical Analysis of Index-Guiding Photonic Crystal Fibers with Low Confinement Loss and Ultra-Flattened Dispersion by FDFD Method

    Directory of Open Access Journals (Sweden)

    M. Pourmahyabadi

    2009-09-01

    Full Text Available In this article, perfectly matched layer (PML for the boundary treatment and an efficient compact two dimensional finite-difference frequency-domain (2-D FDFD method were combined to model photonic crystal fibers (PCF. For photonic crystal fibers, if we assume that the propagation constant along the propagation direction is fixed, three-dimensional hybrid guided modes can be calculated by using only a two-dimensional mesh. An index-guiding PCF with an array of air-holes surrounding the silica core region has special characteristics compared with conventional single-mode fibers (SMFs. Using this model, the fundamental characteristics of single mode photonic crystal fibers (SMPCFs such as confinement loss, bending loss, effective mode area and chromatic dispersion are numerically investigated. The results revealed that low confinement loss and zero-flattened chromatic dispersion can be obtained by varying the air-holes diameter of each ring along the PCF radius. In this work, an especial PCF with nearly zero-flattened dispersion (1.3 ps/nm/km over a wide wavelength range which covers O, E, S, C, L and U telecommunication wavelength bands and low confinement loss (0.06 dB/km at 1.55μm is designed. Macro-bending loss performance of the designed PCF is also studied and it is found that the fiber shows low bending losses for the smallest feasible bending radius of 5 mm. Also, it is revealed that the temperature sensitivity of PCFs is very low in compared with the conventional fibers.

  18. Punção Aspirativa por Agulha Fina Orientada por Ultra-Sonografia em Lesões Não-palpáveis Fine Needle Aspiration Cytology Guided by Ultrasound in Nonpalpable Lesions

    Directory of Open Access Journals (Sweden)

    Cláudio Kemp

    2001-06-01

    Full Text Available Objetivo: correlacionar os achados citológicos obtidos por punção com agulha fina dirigida pela ultra-sonografia de lesões não-palpáveis da mama, císticas ou sólidas, os aspectos ultra-sonográficos e os respectivos resultados histopatológicos das lesões que foram submetidas a cirurgia. Métodos: foram analisadas 617 lesões não-palpáveis visualizadas ao ultra-som. Realizou-se a punção aspirativa por agulha fina (PAAF orientada pela ultra-sonografia, com análise citológica do material, diferenciando-as em cistos ou nódulos sólidos. Estes tiveram seu resultado citológico confrontado com o resultado histopatológico, nos casos em que foi realizada a biópsia cirúrgica. Resultados: das 617 lesões não-palpáveis, 471 eram cistos, sendo 451 cistos simples que apresentaram citologia negativa em todos os casos e 20 casos foram considerados cistos complexos. Destes, 3 (15% tiveram resultado citológico positivo ou suspeito e em 2 casos confirmou-se malignidade. Dos 105 nódulos sólidos, 63 apresentaram citologia negativa, sendo 59 concordantes com a biópsia e houve 4 casos (0,3% de resultado falso-negativo pela citologia. Todos, porém, apresentavam discordância entre imagem e citologia. Em 14 nódulos sólidos (13%, a citologia foi suspeita e, destes, 5 foram diagnosticados como carcinoma. Em outros 14 (13%, o material foi insatisfatório e 1 era carcinoma. Em 51 casos, o tríplice diagnóstico foi concordante e optou-se por seguimento clínico. Conclusão: a análise citológica do material dos cistos mamários simples é desnecessária, porém quando são complexos, a citologia é imperativa. Nas lesões sólidas não-palpáveis, é fundamental a correlação da citologia com o aspecto ultra-sonográfico e mamográfico; caso sejam discordantes, deve-se sempre prosseguir a investigação da lesão.Purpose: to determine the relationship between fine needle aspiration cytology guided by ultrasound of nonpalpable breast lesions

  19. A comparison of prostate tumor targeting strategies using magnetic resonance imaging-targeted, transrectal ultrasound-guided fusion biopsy.

    Science.gov (United States)

    Martin, Peter R; Cool, Derek W; Fenster, Aaron; Ward, Aaron D

    2018-03-01

    Magnetic resonance imaging (MRI)-targeted, three-dimensional (3D) transrectal ultrasound (TRUS)-guided prostate biopsy aims to reduce the 21-47% false-negative rate of clinical two-dimensional (2D) TRUS-guided systematic biopsy, but continues to yield false-negative results. This may be improved via needle target optimization, accounting for guidance system errors and image registration errors. As an initial step toward the goal of optimized prostate biopsy targeting, we investigated how needle delivery error impacts tumor sampling probability for two targeting strategies. We obtained MRI and 3D TRUS images from 49 patients. A radiologist and radiology resident assessed these MR images and contoured 81 suspicious regions, yielding tumor surfaces that were registered to 3D TRUS. The biopsy system's root-mean-squared needle delivery error (RMSE) and systematic error were modeled using an isotropic 3D Gaussian distribution. We investigated two different prostate tumor-targeting strategies using (a) the tumor's centroid and (b) a ring in the lateral-elevational plane. For each simulation, targets were spaced at equal arc lengths on a ring with radius equal to the systematic error magnitude. A total of 1000 biopsy simulations were conducted for each tumor, with RMSE and systematic error magnitudes ranging from 1 to 6 mm. The difference in median tumor sampling probability and probability of obtaining a 50% core involvement was determined for ring vs centroid targeting. Our simulation results indicate that ring targeting outperformed centroid targeting in situations where systematic error exceeds RMSE. In these instances, we observed statistically significant differences showing 1-32% improvement in sampling probability due to ring targeting. Likewise, we observed statistically significant differences showing 1-39% improvement in 50% core involvement probability due to ring targeting. Our results suggest that the optimal targeting scheme for prostate biopsy depends on

  20. Dynamic T{sub 2}-mapping during magnetic resonance guided high intensity focused ultrasound ablation of bone marrow

    Energy Technology Data Exchange (ETDEWEB)

    Waspe, Adam C.; Looi, Thomas; Mougenot, Charles; Amaral, Joao; Temple, Michael; Sivaloganathan, Siv; Drake, James M. [Centre for Image Guided Innovation and Therapeutic Intervention, The Hospital for Sick Children, Toronto, ON, M5G 1X8 (Canada); Philips Healthcare Canada, Markham, ON, L6C 2S3 (Canada); Centre for Image Guided Innovation and Therapeutic Intervention, The Hospital for Sick Children, Toronto, ON, M5G 1X8 (Canada); Department of Applied Mathematics, University of Waterloo, Waterloo, ON, N2L 3G1 (Canada); Centre for Image Guided Innovation and Therapeutic Intervention, The Hospital for Sick Children, Toronto, ON, M5G 1X8 (Canada)

    2012-11-28

    Focal bone tumor treatments include amputation, limb-sparing surgical excision with bone reconstruction, and high-dose external-beam radiation therapy. Magnetic resonance guided high intensity focused ultrasound (MR-HIFU) is an effective non-invasive thermotherapy for palliative management of bone metastases pain. MR thermometry (MRT) measures the proton resonance frequency shift (PRFS) of water molecules and produces accurate (<1 Degree-Sign C) and dynamic (<5s) thermal maps in soft tissues. PRFS-MRT is ineffective in fatty tissues such as yellow bone marrow and, since accurate temperature measurements are required in the bone to ensure adequate thermal dose, MR-HIFU is not indicated for primary bone tumor treatments. Magnetic relaxation times are sensitive to lipid temperature and we hypothesize that bone marrow temperature can be determined accurately by measuring changes in T{sub 2}, since T{sub 2} increases linearly in fat during heating. T{sub 2}-mapping using dual echo times during a dynamic turbo spin-echo pulse sequence enabled rapid measurement of T{sub 2}. Calibration of T{sub 2}-based thermal maps involved heating the marrow in a bovine femur and simultaneously measuring T{sub 2} and temperature with a thermocouple. A positive T{sub 2} temperature dependence in bone marrow of 20 ms/ Degree-Sign C was observed. Dynamic T{sub 2}-mapping should enable accurate temperature monitoring during MR-HIFU treatment of bone marrow and shows promise for improving the safety and reducing the invasiveness of pediatric bone tumor treatments.

  1. Towards hybrid biocompatible magnetic rHuman serum albumin-based nanoparticles: use of ultra-small (CeLn)3/4+ cation-doped maghemite nanoparticles as functional shell

    Science.gov (United States)

    Israel, Liron L.; Kovalenko, Elena I.; Boyko, Anna A.; Sapozhnikov, Alexander M.; Rosenberger, Ina; Kreuter, Jörg; Passoni, Lorena; Lellouche, Jean-Paul

    2015-01-01

    Human serum albumin (HSA) is a protein found in human blood. Over the last decade, HSA has been evaluated as a promising drug carrier. However, not being magnetic, HSA cannot be used for biomedical applications such as magnetic resonance imaging (MRI) and magnetic drug targeting. Therefore, subsequent composites building on iron oxide nanoparticles that are already used clinically as MRI contrast agents are extensively studied. Recently and in this context, innovative fully hydrophilic ultra-small CAN-stabilized maghemite ((CeLn)3/4+-γ-Fe2O3) nanoparticles have been readily fabricated. The present study discusses the design, fabrication, and characterization of a dual phase hybrid core (rHSA)-shell ((CeLn)3/4+-γ-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)3/4+-γ-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)3/4+-γ-Fe2O3 NP surface functionalities (COOH and ligand L coordinative exchange) in addition to very effective MRI contrast capability due to optimal accessibility of H2O molecules with the outer magnetic phase. Resulting hybrid nanoparticles might be used as a platform modular system for therapeutic (drug delivery system) and MR diagnostic purposes.

  2. Towards hybrid biocompatible magnetic rHuman serum albumin-based nanoparticles: use of ultra-small (CeLn)3/4+ cation-doped maghemite nanoparticles as functional shell

    International Nuclear Information System (INIS)

    Israel, Liron L; Lellouche, Jean-Paul; Kovalenko, Elena I; Boyko, Anna A; Sapozhnikov, Alexander M; Rosenberger, Ina; Kreuter, Jörg; Passoni, Lorena

    2015-01-01

    Human serum albumin (HSA) is a protein found in human blood. Over the last decade, HSA has been evaluated as a promising drug carrier. However, not being magnetic, HSA cannot be used for biomedical applications such as magnetic resonance imaging (MRI) and magnetic drug targeting. Therefore, subsequent composites building on iron oxide nanoparticles that are already used clinically as MRI contrast agents are extensively studied. Recently and in this context, innovative fully hydrophilic ultra-small CAN-stabilized maghemite ((CeL n ) 3/4+ -γ-Fe 2 O 3 ) nanoparticles have been readily fabricated. The present study discusses the design, fabrication, and characterization of a dual phase hybrid core (rHSA)-shell ((CeL n ) 3/4+ -γ-Fe 2 O 3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeL n ) 3/4+ -γ-Fe 2 O 3 NPs enabled to exploit both rHSA (protein functionalities) and (CeL n ) 3/4+ -γ-Fe 2 O 3 NP surface functionalities (COOH and ligand L coordinative exchange) in addition to very effective MRI contrast capability due to optimal accessibility of H 2 O molecules with the outer magnetic phase. Resulting hybrid nanoparticles might be used as a platform modular system for therapeutic (drug delivery system) and MR diagnostic purposes. (paper)

  3. Phosphene-guided transcranial magnetic stimulation of occipital but not parietal cortex suppresses stimulus visibility

    Science.gov (United States)

    Tapia, Evelina; Mazzi, Chiara; Savazzi, Silvia; Beck, Diane M.

    2014-01-01

    Transcranial magnetic stimulation (TMS) applied over the occipital lobe approximately 100 ms after the onset of a stimulus decreases its visibility if it appears in the location of the phosphene. Because phosphenes can also be elicited by stimulation of the parietal regions, we asked if the same procedure that is used to reduce visibility of stimuli with occipital TMS will lead to decreased stimulus visibility when TMS is applied to parietal regions. TMS was randomly applied at 0 to 130 ms after the onset of the stimulus (SOA) in steps of 10 ms in occipital and parietal regions. Participants responded to the orientation of the line stimulus and rated its visibility. We replicate previous reports of phosphenes from both occipital and parietal TMS. As previously reported, we also observed visual suppression around the classical 100 ms window both in the objective line orientation and subjective visibility responses with occipital TMS. Parietal stimulation, on the other hand, did not consistently reduce stimulus visibility in any time window. PMID:24584900

  4. Virtual cathode microwave generation using inhomogeneous magnetic field and wave guide wall configuration

    International Nuclear Information System (INIS)

    Thode, L.E.; Kwan, T.J.T.

    1984-01-01

    Microwave generation from a virtual cathode system is investigated using two-dimensional particle-in-cell simulation. In the typical virtual cathode geometry, the electron beam diode is separated from the output waveguide by a ground plane which is a thin foil or screen. By lowering the diode impedance sufficiently, it is possible to form a virtual cathode in the waveguide region a short distance from the ground plane. In this configuration two mechanisms can lead to microwave generation: 1) electron bunching due to reflection between the real and virtual cathode and 2) electron bunching due to virtual cathode oscillation. Both mechanisms are typically present, but it appears possible to make one mechanism dominant by adjusting the output waveguide radius. Although such a configuration might generate 1-10 GW output, electron deposition into the ground plane, waveguide wall, and output window causes breakdown. To overcome these disadvantages, the authors have investigated a configuration with no ground plane coupled with the use of an inhomogeneous external magnetic field and waveguide wall

  5. A practical guide to diagnostic transcranial magnetic stimulation: report of an IFCN committee.

    Science.gov (United States)

    Groppa, S; Oliviero, A; Eisen, A; Quartarone, A; Cohen, L G; Mall, V; Kaelin-Lang, A; Mima, T; Rossi, S; Thickbroom, G W; Rossini, P M; Ziemann, U; Valls-Solé, J; Siebner, H R

    2012-05-01

    Transcranial magnetic stimulation (TMS) is an established neurophysiological tool to examine the integrity of the fast-conducting corticomotor pathways in a wide range of diseases associated with motor dysfunction. This includes but is not limited to patients with multiple sclerosis, amyotrophic lateral sclerosis, stroke, movement disorders, disorders affecting the spinal cord, facial and other cranial nerves. These guidelines cover practical aspects of TMS in a clinical setting. We first discuss the technical and physiological aspects of TMS that are relevant for the diagnostic use of TMS. We then lay out the general principles that apply to a standardized clinical examination of the fast-conducting corticomotor pathways with single-pulse TMS. This is followed by a detailed description of how to examine corticomotor conduction to the hand, leg, trunk and facial muscles in patients. Additional sections cover safety issues, the triple stimulation technique, and neuropediatric aspects of TMS. Copyright © 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  6. A novel magnetic resonance imaging-compatible motor control method for image-guided robotic surgery

    International Nuclear Information System (INIS)

    Suzuki, Takashi; Liao, Hongen; Kobayashi, Etsuko; Sakuma, Ichiro

    2006-01-01

    For robotic surgery assistance systems that use magnetic resonance imaging (MRI) for guidance, the problem of electromagnetic interference is common. Image quality is particularly degraded if motors are running during scanning. We propose a novel MRI-compatible method considering the pulse sequence of imaging. Motors are driven for a short time when the MRI system stops signal acquisition (i.e., awaiting relaxation of the proton), so the image does not contain noise from the actuators. The MRI system and motor are synchronized using a radio frequency pulse signal (8.5 MHz) as the trigger, which is acquired via a special antenna mounted near the scanner. This method can be widely applied because it only receives part of the scanning signal and neither hardware nor software of the MRI system needs to be changed. As a feasibility evaluation test, we compared the images and signal-to-noise ratios between the cases with and without this method, under the condition that a piezoelectric motor was driven during scanning as a noise source, which was generally used as a MRI-compatible actuator. The results showed no deterioration in image quality and the benefit of the new method even though the choice of available scanning sequences is limited. (author)

  7. Magnetic resonance imaging-guided navigation with a thermoplastic shell for breast-conserving surgery.

    Science.gov (United States)

    Abe, M; Kiryu, T; Sonoda, K; Kashiki, Y

    2011-11-01

    The aim of this study was to evaluate the accuracy of a magnetic resonance imaging (MRI) marking technique with a drape-type thermoplastic shell for planning breast-conserving surgery (BCS). A prospective review was performed on 35 consecutive patients who underwent MRI in the supine position and used the specified MRI marking technique. Eleven cases underwent pre-operative chemotherapy and 24 cases did not. After immobilizing the breast mound with a drape-type thermoplastic shell, patients underwent MRI, and the location of the lesion was marked on the shell. Resection lines were dyed blue by indigo carmine, which was pushed through the pores of the shell. Specimens obtained during BCS were sliced into 5-mm contiguous sections, and the margin was assessed for each specimen. Cancer foci less than 5 mm from the margin were classified as positive. Of 35 patients, 33 were included in the analysis; 2 were excluded due to a lack of effect of pre-operative chemotherapy. Of these 33 patients, 25 (75.8%) had negative margins and 7 (21.2%) had positive margins. Our MRI marking technique may be useful for evaluating the extent of tumors that were determined by MRI alone. Long-term outcomes of this technique should be evaluated further. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Transcranial magnetic stimulation and preparation of visually-guided reaching movements

    Directory of Open Access Journals (Sweden)

    Pierpaolo eBusan

    2012-08-01

    Full Text Available To better define the neural networks related to preparation of reaching, we applied transcranial magnetic stimulation (TMS to the lateral parietal and frontal cortex. TMS did not evoke effects closely related to preparation of reaching, suggesting that neural networks already identified by our group are not larger than previously thought. We also replicated previous TMS/EEG data by applying TMS to the parietal cortex: new analyses were performed to better support reliability of already reported findings (Zanon et al., 2010; Brain Topography 22, 307-317. We showed the existence of neural circuits ranging from posterior to frontal regions of the brain after the stimulation of parietal cortex, supporting the idea of strong connections among these areas and suggesting their possible temporal dynamic. Connection with ventral stream was confirmed.The present work helps to define those areas which are involved in preparation of natural reaching in humans. They correspond to parieto-occipital, parietal and premotor medial regions of the left hemisphere, i.e. the contralateral one with respect to the moving hand, as suggested by previous studies. Behavioral data support the existence of a discrete stream involved in reaching. Besides the serial flow of activation from posterior to anterior direction, a parallel elaboration of information among parietal and premotor areas seems also to exist. Present cortico-cortical interactions (TMS/EEG experiment show propagation of activity to frontal, temporal, parietal and more posterior regions, exhibiting distributed communication among various areas in the brain.The neural system highlighted by TMS/EEG experiments is wider with respect to the one disclosed by the TMS behavioral approach. Further studies are needed to unravel this paucity of overlap. Moreover, the understanding of these mechanisms is crucial for the comprehension of response inhibition and changes in prepared actions, which are common behaviors in

  9. Magnets

    International Nuclear Information System (INIS)

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  10. Magnetic resonance imaging-guided biopsies may improve diagnosis in biopsy-naive men with suspicion of prostate cancer

    DEFF Research Database (Denmark)

    Winther, Mads Dochedahl; Balslev, Ingegerd; Boesen, Lars

    2017-01-01

    INTRODUCTION: The purpose of this pilot study was to investigate whether a short prostate biparametric magnetic resonance imaging (bp-MRI) protocol provides a valuable diagnostic addition for biopsy guidance in biopsy-naive men with a suspicion of prostate cancer (PCa). METHODS: A total of 62...... biopsy-naive patients referred to a systematic transrectal ultrasound biopsy (TRUS-bx) due to suspicion of PCa were prospectively enrolled. Bp-MRI was performed before biopsy. All lesions were scored according to the modified Prostate Imaging Reporting and Data System (PI-RADS) version 2. All patients...... underwent TRUS-bx followed by bp-MRI-guided biopsies (bp-MRI-bx) under MRI/TRUS image fusion from any bp-MRI suspicious lesions not obviously targeted by TRUS-bx. RESULTS: PCa was found in 42 (68%) and 32 (52%) patients by TRUS-bx and bp-MRI-bx, respectively. Bp-MRI-bx de-tected PCa in one patient who had...

  11. Deep and superficial infrapatellar bursae: cadaveric investigation of regional anatomy using magnetic resonance after ultrasound-guided bursography

    Energy Technology Data Exchange (ETDEWEB)

    Viegas, Flavio C.; Trudell, Debbie J.; Haghighi, Parviz; Resnick, Donald [Veterans Affairs Medical Center - San Diego, San Diego, CA (United States); Aguiar, Rodrigo O.C. [Veterans Affairs Medical Center - San Diego, San Diego, CA (United States); Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil); Gasparetto, Emerson; Marchiori, Edson [Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil)

    2007-01-15

    To demonstrate the anatomy of the deep and superficial infrapatellar bursae using magnetic resonance (MR) imaging and anatomic correlation in cadavers. MR imaging of the infrapatellar bursae of nine cadaveric knees was performed after ultrasound-guided bursography. The images were compared with those seen on anatomic sectioning. Histologic analysis was obtained in two specimens. The deep infrapatellar bursa (DIB) was visualized in all specimens (n=9) and the superficial infrapatellar bursa (SIB) in five specimens (55%). The mean dimensions of the DIB in the craniocaudal, mediolateral, and anteroposterior planes were respectively 25, 28.7, and 6 mm, and for SIB 19.5, 21.2 and 2.2 mm. A fat apron dividing the DIB was depicted in eight knees (89%). Lateral extension of the DIB beyond the patellar tendon was observed in 100% of cases. Cadaveric analysis depicted a thin septum in the SIB in four of five cases (80%). The DIB is generally present and extends beyond the lateral margin of the patellar tendon. A fat apron partially separating this structure is usual. The SIB is not an unusual finding and may have a septum separating its compartments. (orig.)

  12. Magnetic Resonance-Guided Growth Plate Bone Bridge Resection at 0.23 Tesla: Report of a Novel Technique

    International Nuclear Information System (INIS)

    Blanco Sequeiros, R.; Vaehaesarja, V.; Ojala, R.

    2008-01-01

    Background: Growth plate or physeal cartilage trauma may result in delayed or immediate failure of growth due to bone bridge formation at the insult site. With computed tomography (CT) and magnetic resonance imaging (MRI), the role of imaging has expanded from diagnosis to treatment planning and therapy guidance. Purpose: To describe a technique for MR-guided growth plate bone bridge resection and to evaluate feasibility of the procedure. Material and Methods: Three consecutive patients with growth plate bone bridges were treated surgically under MR guidance. All bridges were detected with prior MRI and radiographs. All patients were referred to procedure due to growth plate bridge associated growth anomaly and pertaining clinical symptoms. The effect of the treatment was evaluated after 48 months with a clinical follow-up. Results: All bridges were successfully detected, marked, and removed under MRI guidance. All patients had relief from their symptoms. Two patients had lasting results from the operation with no further operative treatment needed or scheduled at 48 months from primary treatment. There was one clinical failure, with the patient requiring repeated osteotomies. Conclusion: We have successfully implemented a novel therapy for growth plate bridge resection

  13. Intraoperative high-field magnetic resonance imaging, multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas.

    Science.gov (United States)

    Li, Fang-Ye; Chen, Xiao-Lei; Xu, Bai-Nan

    2016-09-01

    To determine the beneficial effects of intraoperative high-field magnetic resonance imaging (MRI), multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas. Twelve patients with 13 supratentorial cavernomas were prospectively enrolled and operated while using a 1.5 T intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. All cavernomas were deeply located in subcortical areas or involved critical areas. Intraoperative high-field MRIs were obtained for the intraoperative "visualization" of surrounding eloquent structures, "brain shift" corrections, and navigational plan updates. All cavernomas were successfully resected with guidance from intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. In 5 cases with supratentorial cavernomas, intraoperative "brain shift" severely deterred locating of the lesions; however, intraoperative MRI facilitated precise locating of these lesions. During long-term (>3 months) follow-up, some or all presenting signs and symptoms improved or resolved in 4 cases, but were unchanged in 7 patients. Intraoperative high-field MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring are helpful in surgeries for the treatment of small deeply seated subcortical cavernomas.

  14. [Neuroprotective subthalamotomy in Parkinson's disease. The role of magnetic resonance-guided focused ultrasound in early surgery].

    Science.gov (United States)

    Guridi, Jorge; Marigil, Miguel; Becerra, Victoria; Parras, Olga

    Subthalamic nucleus hyperactivity in Parkinson's disease may be a very early phenomenon. Its start is not well known, and it may occur during the pre-symptomatic disease stage. Glutamatergic hyperactivity may be neurotoxic over the substantia nigra compacta dopaminergic neurons. If this occurred, the excitatory neurotransmitter, glutamate, should affect the neurons that maintain a high turnover as a compensatory mechanism. Would a subthalamic nucleus lesion decrease this hyperactivity and thus be considered as a neuroprotective mechanism for dopaminergic neurons? The authors hypothesise about the possibility to perform surgery on a subthalamic nucleus lesion at a very early stage in order to avoid the neurotoxic glutamatergic effect over the dopaminergic neurons, and therefore be considered as a neuroprotective surgery able to alter the progress of the disease during early motor symptoms. In this regard, magnetic resonance-guided focused ultrasound techniques open a new window in the stereotactic armamentarium. Copyright © 2016 Sociedad Española de Neurocirugía. Publicado por Elsevier España, S.L.U. All rights reserved.

  15. Endovascular brain intervention and mapping in a dog experimental model using magnetically-guided micro-catheter technology.

    Science.gov (United States)

    Kara, Tomas; Leinveber, Pavel; Vlasin, Michal; Jurak, Pavel; Novak, Miroslav; Novak, Zdenek; Chrastina, Jan; Czechowicz, Krzysztof; Belehrad, Milos; Asirvatham, Samuel J

    2014-06-01

    Despite the substantial progress that has been achieved in interventional cardiology and cardiac electrophysiology, endovascular intervention for the diagnosis and treatment of central nervous system (CNS) disorders such as stroke, epilepsy and CNS malignancy is still limited, particularly due to highly tortuous nature of the cerebral arterial and venous system. Existing interventional devices and techniques enable only limited and complicated access especially into intra-cerebral vessels. The aim of this study was to develop a micro-catheter magnetically-guided technology specifically designed for endovascular intervention and mapping in deep CNS vascular structures. Mapping of electrical brain activity was performed via the venous system on an animal dog model with the support of the NIOBE II system. A novel micro-catheter specially designed for endovascular interventions in the CNS, with the support of the NIOBE II technology, was able to reach safely deep intra-cerebral venous structures and map the electrical activity there. Such structures are not currently accessible using standard catheters. This is the first study demonstrating successful use of a new micro-catheter in combination with NIOBE II technology for endovascular intervention in the brain.

  16. First Magnetic Resonance Imaging-Guided Aortic Stenting and Cava Filter Placement Using a Polyetheretherketone-Based Magnetic Resonance Imaging-Compatible Guidewire in Swine: Proof of Concept

    International Nuclear Information System (INIS)

    Kos, Sebastian; Huegli, Rolf; Hofmann, Eugen; Quick, Harald H.; Kuehl, Hilmar; Aker, Stephanie; Kaiser, Gernot M.; Borm, Paul J. A.; Jacob, Augustinus L.; Bilecen, Deniz

    2009-01-01

    The purpose of this study was to demonstrate feasibility of percutaneous transluminal aortic stenting and cava filter placement under magnetic resonance imaging (MRI) guidance exclusively using a polyetheretherketone (PEEK)-based MRI-compatible guidewire. Percutaneous transluminal aortic stenting and cava filter placement were performed in 3 domestic swine. Procedures were performed under MRI-guidance in an open-bore 1.5-T scanner. The applied 0.035-inch guidewire has a PEEK core reinforced by fibres, floppy tip, hydrophilic coating, and paramagnetic markings for passive visualization. Through an 11F sheath, the guidewire was advanced into the abdominal (swine 1) or thoracic aorta (swine 2), and the stents were deployed. The guidewire was advanced into the inferior vena cava (swine 3), and the cava filter was deployed. Postmortem autopsy was performed. Procedural success, guidewire visibility, pushability, and stent support were qualitatively assessed by consensus. Procedure times were documented. Guidewire guidance into the abdominal and thoracic aortas and the inferior vena cava was successful. Stent deployments were successful in the abdominal (swine 1) and thoracic (swine 2) segments of the descending aorta. Cava filter positioning and deployment was successful. Autopsy documented good stent and filter positioning. Guidewire visibility through applied markers was rated acceptable for aortic stenting and good for venous filter placement. Steerability, pushability, and device support were good. The PEEK-based guidewire allows either percutaneous MRI-guided aortic stenting in the thoracic and abdominal segments of the descending aorta and filter placement in the inferior vena cava with acceptable to good device visibility and offers good steerability, pushability, and device support.

  17. First magnetic resonance imaging-guided aortic stenting and cava filter placement using a polyetheretherketone-based magnetic resonance imaging-compatible guidewire in swine: proof of concept.

    Science.gov (United States)

    Kos, Sebastian; Huegli, Rolf; Hofmann, Eugen; Quick, Harald H; Kuehl, Hilmar; Aker, Stephanie; Kaiser, Gernot M; Borm, Paul J A; Jacob, Augustinus L; Bilecen, Deniz

    2009-05-01

    The purpose of this study was to demonstrate feasibility of percutaneous transluminal aortic stenting and cava filter placement under magnetic resonance imaging (MRI) guidance exclusively using a polyetheretherketone (PEEK)-based MRI-compatible guidewire. Percutaneous transluminal aortic stenting and cava filter placement were performed in 3 domestic swine. Procedures were performed under MRI-guidance in an open-bore 1.5-T scanner. The applied 0.035-inch guidewire has a PEEK core reinforced by fibres, floppy tip, hydrophilic coating, and paramagnetic markings for passive visualization. Through an 11F sheath, the guidewire was advanced into the abdominal (swine 1) or thoracic aorta (swine 2), and the stents were deployed. The guidewire was advanced into the inferior vena cava (swine 3), and the cava filter was deployed. Postmortem autopsy was performed. Procedural success, guidewire visibility, pushability, and stent support were qualitatively assessed by consensus. Procedure times were documented. Guidewire guidance into the abdominal and thoracic aortas and the inferior vena cava was successful. Stent deployments were successful in the abdominal (swine 1) and thoracic (swine 2) segments of the descending aorta. Cava filter positioning and deployment was successful. Autopsy documented good stent and filter positioning. Guidewire visibility through applied markers was rated acceptable for aortic stenting and good for venous filter placement. Steerability, pushability, and device support were good. The PEEK-based guidewire allows either percutaneous MRI-guided aortic stenting in the thoracic and abdominal segments of the descending aorta and filter placement in the inferior vena cava with acceptable to good device visibility and offers good steerability, pushability, and device support.

  18. Why and Where do We Miss Significant Prostate Cancer with Multi-parametric Magnetic Resonance Imaging followed by Magnetic Resonance-guided and Transrectal Ultrasound-guided Biopsy in Biopsy-naïve Men?

    Science.gov (United States)

    Schouten, Martijn G; van der Leest, Marloes; Pokorny, Morgan; Hoogenboom, Martijn; Barentsz, Jelle O; Thompson, Les C; Fütterer, Jurgen J

    2017-06-01

    Knowledge of significant prostate (sPCa) locations being missed with magnetic resonance (MR)- and transrectal ultrasound (TRUS)-guided biopsy (Bx) may help to improve these techniques. To identify the location of sPCa lesions being missed with MR- and TRUS-Bx. In a referral center, 223 consecutive Bx-naive men with elevated prostate specific antigen level and/or abnormal digital rectal examination were included. Histopathologically-proven cancer locations, Gleason score, and tumor length were determined. All patients underwent multi-parametric MRI and 12-core systematic TRUS-Bx. MR-Bx was performed in all patients with suspicion of PCa on multi-parametric MRI (n=142). Cancer locations were compared between MR- and TRUS-Bx. Proportions were expressed as percentages, and the corresponding 95% confidence intervals were calculated. In total, 191 lesions were found in 108 patients with sPCa. From these lesion 74% (141/191) were defined as sPCa on either MR- or TRUS-Bx. MR-Bx detected 74% (105/141) of these lesions and 61% (86/141) with TRUS-Bx. TRUS-Bx detected more lesions compared with MR-Bx (140 vs 109). However, these lesions were often low risk (39%). Significant lesions missed with MR-Bx most often had involvement of dorsolateral (58%) and apical (37%) segments and missed segments with TRUS-Bx were located anteriorly (79%), anterior midprostate (50%), and anterior apex (23%). Both techniques have difficulties in detecting apical lesions. MR-Bx most often missed cancer with involvement of the dorsolateral part (58%) and TRUS-Bx with involvement of the anterior part (79%). Both biopsy techniques miss cancer in specific locations within the prostate. Identification of these lesions may help to improve these techniques. Copyright © 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.

  19. 28 May 2010 - Representatives of the Netherlands School of Public Administration guided in the ATLAS visitor centre by ATLAS Collaboration Member and NIKHEF G. Bobbink and ATLAS Magnet Project Leader H.ten Kate.

    CERN Document Server

    Maximilien Brice

    2010-01-01

    28 May 2010 - Representatives of the Netherlands School of Public Administration guided in the ATLAS visitor centre by ATLAS Collaboration Member and NIKHEF G. Bobbink and ATLAS Magnet Project Leader H.ten Kate.

  20. TU-AB-BRA-12: Quality Assurance of An Integrated Magnetic Resonance Image Guided Adaptive Radiotherapy Machine Using Cherenkov Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Andreozzi, J; Bruza, P; Saunders, S; Pogue, B [Dartmouth College, Hanover, NH (United States); Mooney, K; Curcuru, A; Green, O [Washington University School of Medicine, Saint Louis, MO (United States); Gladstone, D [Dartmouth-Hitchcock Med. Ctr., Lebanon, NH (Lebanon)

    2016-06-15

    Purpose: To investigate the viability of using Cherenkov imaging as a fast and robust method for quality assurance tests in the presence of a magnetic field, where other instruments can be limited. Methods: Water tank measurements were acquired from a clinically utilized adaptive magnetic resonance image guided radiation therapy (MR-IGRT) machine with three multileaf-collimator equipped 60Co sources. Cherenkov imaging used an intensified charge coupled device (ICCD) camera placed 3.5m from the treatment isocenter, looking down the bore of the 0.35T MRI into a water tank. Images were post-processed to make quantitative comparison between Cherenkov light intensity with both film and treatment planning system predictions, in terms of percent depth dose curves as well as lateral beam profile measurements. A TG-119 commissioning test plan (C4: C-Shape) was imaged in real-time at 6.33 frames per second to investigate the temporal and spatial resolution of the Cherenkov imaging technique. Results: A .33mm/pixel Cherenkov image resolution was achieved across 1024×1024 pixels in this setup. Analysis of the Cherenkov image of a 10.5×10.5cm treatment beam in the water tank successfully measured the beam width at the depth of maximum dose within 1.2% of the film measurement at the same point. The percent depth dose curve for the same beam was on average within 2% of ionization chamber measurements for corresponding depths between 3–100mm. Cherenkov video of the TG-119 test plan provided qualitative agreement with the treatment planning system dose predictions, and a novel temporal verification of the treatment. Conclusions: Cherenkov imaging was successfully used to make QA measurements of percent depth dose curves and cross beam profiles of MRI-IGRT radiotherapy machines after only several seconds of beam-on time and data capture; both curves were extracted from the same data set. Video-rate imaging of a dynamic treatment plan provided new information regarding temporal

  1. Technical Note: Dose effects of 1.5 T transverse magnetic field on tissue interfaces in MRI-guided radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xinfeng; Prior, Phil; Chen, Guang-Pei; Schultz, Christopher J.; Li, X. Allen, E-mail: ali@mcw.edu [Department of Radiation Oncology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226 (United States)

    2016-08-15

    dose effects of the TMF at tissue interfaces (e.g., air-cavity wall, lung-tissue interfaces, skin) are significantly reduced in most cases. Conclusions: The doses on tissue interfaces can be significantly changed by the presence of a TMF during MR-guided RT when the magnetic field is not included in plan optimization. These changes can be substantially reduced or even eliminated during VMAT/IMRT optimization that specifically considers the TMF, without deteriorating overall plan quality.

  2. A long arm for ultrasound: a combined robotic focused ultrasound setup for magnetic resonance-guided focused ultrasound surgery.

    Science.gov (United States)

    Krafft, Axel J; Jenne, Jürgen W; Maier, Florian; Stafford, R Jason; Huber, Peter E; Semmler, Wolfhard; Bock, Michael

    2010-05-01

    Focused ultrasound surgery (FUS) is a highly precise noninvasive procedure to ablate pathogenic tissue. FUS therapy is often combined with magnetic resonance (MR) imaging as MR imaging offers excellent target identification and allows for continuous monitoring of FUS induced temperature changes. As the dimensions of the ultrasound (US) focus are typically much smaller than the targeted volume, multiple sonications and focus repositioning are interleaved to scan the focus over the target volume. Focal scanning can be achieved electronically by using phased-array US transducers or mechanically by using dedicated mechanical actuators. In this study, the authors propose and evaluate the precision of a combined robotic FUS setup to overcome some of the limitations of the existing MRgFUS systems. Such systems are typically integrated into the patient table of the MR scanner and thus only provide an application of the US wave within a limited spatial range from below the patient. The fully MR-compatible robotic assistance system InnoMotion (InnoMedic GmbH, Herxheim, Germany) was originally designed for MR-guided interventions with needles. It offers five pneumatically driven degrees of freedom and can be moved over a wide range within the bore of the magnet. In this work, the robotic system was combined with a fixed-focus US transducer (frequency: 1.7 MHz; focal length: 68 mm, and numerical aperture: 0.44) that was integrated into a dedicated, in-house developed treatment unit for FUS application. A series of MR-guided focal scanning procedures was performed in a polyacrylamide-egg white gel phantom to assess the positioning accuracy of the combined FUS setup. In animal experiments with a 3-month-old domestic pig, the system's potential and suitability for MRgFUS was tested. In phantom experiments, a total targeting precision of about 3 mm was found, which is comparable to that of the existing MRgFUS systems. Focus positioning could be performed within a few seconds

  3. Phospholipid micelle-based magneto-plasmonic nanoformulation for magnetic field-directed, imaging-guided photo-induced cancer therapy.

    Science.gov (United States)

    Ohulchanskyy, Tymish Y; Kopwitthaya, Atcha; Jeon, Mansik; Guo, Moran; Law, Wing-Cheung; Furlani, Edward P; Kim, Chulhong; Prasad, Paras N

    2013-11-01

    We present a magnetoplasmonic nanoplatform combining gold nanorods (GNR) and iron-oxide nanoparticles within phospholipid-based polymeric nanomicelles (PGRFe). The gold nanorods exhibit plasmon resonance absorbance at near infrared wavelengths to enable photoacoustic imaging and photothermal therapy, while the Fe3O4 nanoparticles enable magnetophoretic control of the nanoformulation. The fabricated nanoformulation can be directed and concentrated by an external magnetic field, which provides enhancement of a photoacoustic signal. Application of an external field also leads to enhanced uptake of the magnetoplasmonic formulation by cancer cells in vitro. Under laser irradiation at the wavelength of the GNR absorption peak, the PGRFe formulation efficiently generates plasmonic nanobubbles within cancer cells, as visualized by confocal microscopy, causing cell destruction. The combined magnetic and plasmonic functionalities of the nanoplatform enable magnetic field-directed, imaging-guided, enhanced photo-induced cancer therapy. In this study, a nano-formulation of gold nanorods and iron oxide nanoparticles is presented using a phospholipid micelle-based delivery system for magnetic field-directed and imaging-guided photo-induced cancer therapy. The gold nanorods enable photoacoustic imaging and photothermal therapy, while the Fe3O4 nanoparticles enable magnetophoretic control of the formulation. This and similar systems could enable more precise and efficient cancer therapy, hopefully in the near future, after additional testing. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Bioinspired Multifunctional Melanin-Based Nanoliposome for Photoacoustic/Magnetic Resonance Imaging-Guided Efficient Photothermal Ablation of Cancer

    Science.gov (United States)

    Zhang, Liang; Sheng, Danli; Wang, Dong; Yao, Yuanzhi; Yang, Ke; Wang, Zhigang; Deng, Liming; Chen, Yu

    2018-01-01

    Background: The construction of theranostic nanosystems with concurrently high biosafety and therapeutic performance is a challenge but has great significance for the clinical translation of nanomedicine for combating cancer. Methods: Bio-inspired melanin-based nanoliposomes (Lip-Mel) as theranostic agents were constructed for simultaneous photoacoustic (PA) imaging- and T1-weighted magnetic resonance (MR) imaging-guided photothermal ablation of tumors, which was demonstrated both in vitro and in vivo. The high biosafety of Lip-Mel was also systematically evaluated. Results: The achieved Lip-Mel nanoliposomes demonstrated their imaging capability for both PA and T1-weighted MR imaging (r1 = 0.25 mM-1·s-1) both in vitro and in vivo, providing the potential for therapeutic guidance and monitoring. Importantly, the desirable photothermal-conversion efficiency of the as-prepared Lip-Mel achieved complete eradication of tumors in breast cancer-bearing mice, exhibiting remarkable photothermal-based therapeutic performance. In particular, the efficient encapsulation of melanin into the PEGylated liposome mitigated the potential toxicity of melanin and improved the photothermal performance of the loaded melanin. Systematic in vivo biosafety evaluations demonstrated the high biocompatibility of Lip-Mel at a high dose of 100 mg/kg. Conclusion: In this work, we reported a bioinspired strategy where melanin, a natural product in the human body, is encapsulated into PEGylated nanoliposomes for efficient theranostics with high biocompatibility. This work provides a new strategy for creating desirable theranostic agents with concurrent high biocompatibility and satisfactory theranostic performance through the use of materials that totally originate from biosystems. PMID:29556343

  5. Magnetic resonance imaging-guided focused laser interstitial thermal therapy for subinsular metastatic adenocarcinoma: technical case report.

    Science.gov (United States)

    Hawasli, Ammar H; Ray, Wilson Z; Murphy, Rory K J; Dacey, Ralph G; Leuthardt, Eric C

    2012-06-01

    To describe the novel use of the AutoLITT System (Monteris Medical, Winnipeg, Manitoba, Canada) for focused laser interstitial thermal therapy (LITT) with intraoperative magnetic resonance imaging (MRI) and stereotactic image guidance for the treatment of metastatic adenocarcinoma in the left insula. The patient was a 61-year-old right-handed man with a history of metastatic adenocarcinoma of the colon. He had previously undergone resection of multiple lesions, Gamma Knife radiosurgery, and whole-brain radiation. Despite treatment of a left insular tumor, serial imaging revealed that the lesion continued to enlarge. Given the refractory nature of this tumor to radiation and the deep-seated location, the patient elected to undergo LITT treatment. The center of the lesion and entry point on the scalp were identified with STEALTH (Medtronic, Memphis, Tennessee) image-guided navigation. The AXiiiS Stereotactic Miniframe (Monteris Medical) for the LITT system was secured onto the skull, and a trajectory was defined to achieve access to the centroid of the tumor. After a burr hole was made, a gadolinium template probe was inserted into the AXiiiS base. The trajectory was confirmed via an intraoperative MRI, and the LITT probe driver was attached to the base and CO2-cooled, side-firing laser LITT probe. The laser was activated and thermometry images were obtained. Two trajectories, posteromedial and anterolateral, produced satisfactory tumor ablation. LITT with intraoperative MRI and stereotactic image guidance is a newly available, minimally invasive, and therapeutically viable technique for the treatment of deep seated brain tumors.

  6. Vision 20/20: Magnetic resonance imaging-guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities

    Energy Technology Data Exchange (ETDEWEB)

    Mehranian, Abolfazl; Arabi, Hossein [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva CH-1211 (Switzerland); Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva CH-1211 (Switzerland); Geneva Neuroscience Centre, University of Geneva, Geneva CH-1205 (Switzerland); Department of Nuclear Medicine and Molecular Imaging, University of Groningen, Groningen 9700 RB (Netherlands)

    2016-03-15

    Attenuation correction is an essential component of the long chain of data correction techniques required to achieve the full potential of quantitative positron emission tomography (PET) imaging. The development of combined PET/magnetic resonance imaging (MRI) systems mandated the widespread interest in developing novel strategies for deriving accurate attenuation maps with the aim to improve the quantitative accuracy of these emerging hybrid imaging systems. The attenuation map in PET/MRI should ideally be derived from anatomical MR images; however, MRI intensities reflect proton density and relaxation time properties of biological tissues rather than their electron density and photon attenuation properties. Therefore, in contrast to PET/computed tomography, there is a lack of standardized global mapping between the intensities of MRI signal and linear attenuation coefficients at 511 keV. Moreover, in standard MRI sequences, bones and lung tissues do not produce measurable signals owing to their low proton density and short transverse relaxation times. MR images are also inevitably subject to artifacts that degrade their quality, thus compromising their applicability for the task of attenuation correction in PET/MRI. MRI-guided attenuation correction strategies can be classified in three broad categories: (i) segmentation-based approaches, (ii) atlas-registration and machine learning methods, and (iii) emission/transmission-based approaches. This paper summarizes past and current state-of-the-art developments and latest advances in PET/MRI attenuation correction. The advantages and drawbacks of each approach for addressing the challenges of MR-based attenuation correction are comprehensively described. The opportunities brought by both MRI and PET imaging modalities for deriving accurate attenuation maps and improving PET quantification will be elaborated. Future prospects and potential clinical applications of these techniques and their integration in commercial

  7. Predicting variation in subject thermal response during transcranial magnetic resonance guided focused ultrasound surgery: Comparison in seventeen subject datasets

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, Urvi, E-mail: urvi.vyas@gmail.com; Ghanouni, Pejman; Halpern, Casey H.; Pauly, Kim Butts [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Elias, Jeff [Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia 22908 (United States)

    2016-09-15

    Purpose: In transcranial magnetic resonance-guided focused ultrasound (tcMRgFUS) treatments, the acoustic and spatial heterogeneity of the skull cause reflection, absorption, and scattering of the acoustic beams. These effects depend on skull-specific parameters and can lead to patient-specific thermal responses to the same transducer power. In this work, the authors develop a simulation tool to help predict these different experimental responses using 3D heterogeneous tissue models based on the subject CT images. The authors then validate and compare the predicted skull efficiencies to an experimental metric based on the subject thermal responses during tcMRgFUS treatments in a dataset of seventeen human subjects. Methods: Seventeen human head CT scans were used to create tissue acoustic models, simulating the effects of reflection, absorption, and scattering of the acoustic beam as it propagates through a heterogeneous skull. The hybrid angular spectrum technique was used to model the acoustic beam propagation of the InSightec ExAblate 4000 head transducer for each subject, yielding maps of the specific absorption rate (SAR). The simulation assumed the transducer was geometrically focused to the thalamus of each subject, and the focal SAR at the target was used as a measure of the simulated skull efficiency. Experimental skull efficiency for each subject was calculated using the thermal temperature maps from the tcMRgFUS treatments. Axial temperature images (with no artifacts) were reconstructed with a single baseline, corrected using a referenceless algorithm. The experimental skull efficiency was calculated by dividing the reconstructed temperature rise 8.8 s after sonication by the applied acoustic power. Results: The simulated skull efficiency using individual-specific heterogeneous models predicts well (R{sup 2} = 0.84) the experimental energy efficiency. Conclusions: This paper presents a simulation model to predict the variation in thermal responses

  8. Hair sparing does not compromise real-time magnetic resonance imaging guided stereotactic laser fiber placement for temporal lobe epilepsy.

    Science.gov (United States)

    Singh, Shikha; Kumar, Kevin K; Rabon, Matthew J; Dolce, Dana; Halpern, Casey H

    2018-06-01

    Pre-operative scalp shaving is conventionally thought to simplify postoperative cranial wound care, lower the rate of wound infections, and ease optimal incision localization. Over the past few decades, some neurosurgeons have refrained from scalp shaving in order to improve patient satisfaction with brain surgery. However, this hair-sparing approach has not yet been explored in the growing field of magnetic resonance-guided laser interstitial thermal therapy (MRgLITT). This study investigated the initial impact of a no-shave technique on post-operative wound infection rate as well as on entry and target accuracy in MRgLITT for mesial temporal epilepsy. Eighteen patients selected by the Stanford Comprehensive Epilepsy Program between November 2015 and August 2017 were included in the study. All patients underwent functional selective amygdalohippocampotomies using MRgLITT entirely within a diagnostic MRI suite. No hair was removed and no additional precautions were taken for hair or scalp care. Otherwise, routine protocols for surgical preparations and wound closure were followed. The study was performed under approval from Stanford University's Internal Review Board (IRB-37830). No post-operative wound infections or erosions occurred for any patient. The mean entry point error was 2.87 ± 1.3 mm and the mean target error was 1.0 ± 0.9 mm. There have been no other complications associated with this hair-sparing approach. The study's results suggest that hair sparing in MRgLITT surgery for temporal epilepsy does not increase the risk of wound complications or compromise accuracy. This preferred cosmetic approach may thus appeal to epilepsy patients considering such interventions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. A mathematical model of superparamagnetic iron oxide nanoparticle magnetic behavior to guide the design of novel nanomaterials

    International Nuclear Information System (INIS)

    Ortega, Ryan A.; Giorgio, Todd D.

    2012-01-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) exhibit unique magnetic properties that make them highly efficacious as MR imaging contrast agents and laboratory diagnostic tools. The complexity of SPION magnetic behavior and the multiple parameters affecting this behavior complicate attempts at fabricating particles suited for a particular purpose. A mathematical model of SPION magnetic properties derived from experimental relationships and first principles can be an effective design tool for predicting particle behavior before materials are fabricated. Here, a novel model of SPION magnetic properties is described, using particle size and applied magnetic field as the primary variable inputs. The model is capable of predicting particle susceptibility and non-linear particle magnetization as well as describing the vector magnetic field produced by a single particle in an applied field. Magnetization values produced by the model agree with recent experimental measurements of particle magnetizations. The model is used to predict the complex magnetic behavior of clustered magnetic particles in simulated in vivo environment; specifically, interactions between the clusters and water molecules. The model shows that larger particles exhibit more linear magnetic behavior and stronger magnetization and that clusters of smaller particles allow for more numerous SPION–water molecule interactions and more uniform cluster magnetizations.

  10. The effect of guide-field and boundary conditions on the features and signatures of collisionless magnetic reconnection in a stressed X-point collapse

    Science.gov (United States)

    Graf von der Pahlen, J.; Tsiklauri, D.

    2015-12-01

    Magnetic X-point collapse is investigated using a 2.5D fully relativistic particle-in-cell simulation, with varying strengths of guide-field as well as open and closed boundary conditions. In the zero guide-field case we discover a new signature of Hall-reconnection in the out-of-plane magnetic field, namely an octupolar pattern, as opposed to the well-studied quadrupolar out-of-plane field of reconnection. The emergence of the octupolar components was found to be caused by ion currents and is a general feature of X-point collapse. In a comparative study of tearing-mode reconnection, signatures of octupolar components are found only in the out-flow region. It is argued that space-craft observations of magnetic fields at reconnection sites may be used accordingly to identify the type of reconnection [1][2]. Further, initial oscillatory reconnection is observed, prior to reconnection onset, generating electro-magnetic waves at the upper-hybrid frequency, matching solar flare progenitor emission. When applying a guide-field, in both open and closed boundary conditions, thinner dissipation regions are obtained and the onset of reconnection is increasingly delayed. Investigations with open boundary conditions show that, for guide-fields close to the strength of the in-plane field, shear flows emerge, leading to the formation of electron flow vortices and magnetic islands [3]. Asymmetries in the components of the generalised Ohm's law across the dissipation region are observed. Extended in 3D geometry, it is shown that locations of magnetic islands and vortices are not constant along the height of the current-sheet. Vortices formed on opposite sites of the current-sheet travel in opposite directions along it, leading to a criss-cross vortex pattern. Possible instabilities resulting from this specific structure formation are to be investigated [4].[1] J. Graf von der Pahlen and D. Tsiklauri, Phys. Plasmas 21, 060705 (2014), [2] J. Graf von der Pahlen and D. Tsiklauri

  11. Outcomes following implementation of a pediatric procedural sedation guide for referral to general anesthesia for magnetic resonance imaging studies.

    Science.gov (United States)

    Grunwell, Jocelyn R; Marupudi, Neelima K; Gupta, Rohan V; Travers, Curtis D; McCracken, Courtney E; Williamson, Julie L; Stockwell, Jana A; Fortenberry, James D; Couloures, Kevin; Cravero, Joseph; Kamat, Pradip P

    2016-06-01

    Guidelines for referral of children to general anesthesia (GA) to complete MRI studies are lacking. We devised a pediatric procedural sedation guide to determine whether a pediatric procedural sedation guide would decrease serious adverse events and decrease failed sedations requiring rescheduling with GA. We constructed a consensus-based sedation guide by combining a retrospective review of reasons for referral of children to GA (n = 221) with published risk factors associated with the inability to complete the MRI study with sedation. An interrupted time series analysis of 11 530 local sedation records from the Pediatric Sedation Research Consortium between July 2008 and March 2013, adjusted for case-mix differences in the pre- and postsedation guide cohorts, evaluated whether a sedation guide resulted in decreased severe adverse events (SAE) and failed sedation rates. A significant increase in referrals to GA following implementation of a sedation guide occurred (P pediatric procedural sedation services. © 2016 John Wiley & Sons Ltd.

  12. Sun Ultra 5

    CERN Multimedia

    1998-01-01

    The Sun Ultra 5 is a 64-bit personal computer based on the UltraSPARC microprocessor line at a low price. The Ultra 5 has been declined in several variants: thus, some models have a processor with less cache memory to further decrease the price of the computer.

  13. Standard guide for use of UV-A and visible light sources and meters used in the liquid penetrant and magnetic particle methods

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2004-01-01

    1.1 This guide describes the use of UV-A/Visible light sources and meters used for the examination of materials by the liquid penetrant and magnetic particle processes. This guide may be used to help support the needs for appropriate light intensities and light measurement. 1.2 This guide also provides a reference: 1.2.1 To assist in the selection of light sources and meters that meet the applicable specifications or standards. 1.2.2 For use in the preparation of internal documentation dealing with liquid penetrant or magnetic particle examination of materials and parts. 1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and det...

  14. Magnets and magnetic materials

    International Nuclear Information System (INIS)

    Meuris, Ch.; Rifflet, J.M.

    2007-01-01

    The Large Hadron Collider (LHC), the world's largest highest-energy particle collider that the CERN plans to commission in 2008, gets a double boost from superconducting magnet technology. Superconducting magnets are first used to guide the particles scheduled for collision through the accelerator, and then to observe the events triggered by the collision inside giant detectors in a known magnetic field. Despite the installation's massive dimensions, all this is done with minimal expenditure of energy. (author)

  15. Clickable and imageable multiblock polymer micelles with magnetically guided and PEG-switched targeting and release property for precise tumor theranosis.

    Science.gov (United States)

    Wei, Jing; Shuai, Xiaoyu; Wang, Rui; He, Xueling; Li, Yiwen; Ding, Mingming; Li, Jiehua; Tan, Hong; Fu, Qiang

    2017-11-01

    Targeted delivery of therapeutics and diagnostics using nanotechnology holds great promise to minimize the side effects of conventional chemotherapy and enable specific and real-time detection of diseases. To realize this goal, we report a clickable and imageable nanovehicle assembled from multiblock polyurethanes (MPUs). The soft segments of the polymers are based on detachable poly(ethylene glycol) (PEG) and degradable poly(ε-caprolactone) (PCL), and the hard segments are constructed from lysine- and cystine-derivatives bearing reduction-responsive disulfide linkages and click-active alkynyl moieties, allowing for post-conjugation of targeting ligands via a click chemistry. It was found that the cleavage of PEG corona bearing a pH-sensitive benzoic-imine linkage (BPEG) could act as an on-off switch, which is capable of activating the clicked targeting ligands under extracellular acidic condition, followed by triggering the core degradation and payload release within tumor cells. In combination with superparamagnetic iron oxide nanoparticles (SPION) clustered within the micellar core, the MPUs exhibit excellent magnetic resonance imaging (MRI) contrast effects and T 2 relaxation in vitro, as well as magnetically guided MR imaging and multimodal targeting of therapeutics to tumor precisely, leading to significant inhibition of cancer with minimal side effect. This work provides a safe and versatile platform for the further development of smart theranostic systems for potential magnetically-targeted and imaging-guided personalized medicine. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    Fred Sabins

    2001-01-01

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job

  17. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  18. Magnetic Resonance–Guided High-Intensity Focused Ultrasound Hyperthermia for Recurrent Rectal Cancer: MR Thermometry Evaluation and Preclinical Validation

    Energy Technology Data Exchange (ETDEWEB)

    Chu, William, E-mail: William.Chu@sunnybrook.ca [Department of Radiation Oncology, Sunnybrook Health Sciences Centre and the University of Toronto, Toronto, Ontario (Canada); Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Staruch, Robert M. [Clinical Sites Research Program, Philips Research, Cambridge, Massachusetts (United States); Pichardo, Samuel [Thunder Bay Regional Research Institute, Thunder Bay, Ontario (Canada); Physics and Electrical Engineering, Lakehead University, Thunder Bay, Ontario (Canada); Tillander, Matti; Köhler, Max O. [MR Therapy, Philips Healthcare, Vantaa (Finland); Huang, Yuexi [Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Ylihautala, Mika [MR Therapy, Philips Healthcare, Vantaa (Finland); McGuffin, Merrylee [Department of Radiation Oncology, Sunnybrook Health Sciences Centre and the University of Toronto, Toronto, Ontario (Canada); Czarnota, Gregory [Department of Radiation Oncology, Sunnybrook Health Sciences Centre and the University of Toronto, Toronto, Ontario (Canada); Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Hynynen, Kullervo [Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada)

    2016-07-15

    Purpose: To evaluate the feasibility of magnetic resonance–guided high-intensity focused ultrasound (MR-HIFU) mild hyperthermia in deep tissue targets for enhancing radiation therapy and chemotherapy in the context of recurrent rectal cancer. A preclinical study was performed to evaluate the safety and performance of MR-HIFU mild hyperthermia. A prospective imaging study was performed in volunteers with rectal cancer to evaluate MR thermometry quality near the rectum and accessibility of rectal tumors using MR-HIFU. Methods and Materials: Mild hyperthermia was performed in pig thigh (9 sonications, 6 pigs) using a clinical MR-HIFU system. Targets near the rectal wall and deep thigh were evaluated. Thermal maps obtained in 6 planes every 3.2 seconds were used to control sonications in 18-mm diameter treatment regions at temperatures of 42°C to 42.5°C for 10 to 60 minutes. Volunteer imaging-only studies to assess the quality of MR thermometry (without heating) were approved by the institutional research ethics board. Anatomic and MR thermometry images were acquired in consenting volunteers with rectal cancer. In 3 of 6 study participants, rectal filling with saline was used to reduce motion-related MR thermometry artifacts near the tumor. Results: In pigs, mean target temperature matched the desired hyperthermia temperature within 0.2°C; temporal standard deviation ≤0.5°C. With optimized control thresholds, no undesired tissue damage was observed. In human volunteers, MR temperature measurements had adequate precision and stability, especially when rectal filling was used to reduce bowel motion. Conclusions: In pigs, MR-HIFU can safely deliver mild hyperthermia (41°C-43°C) to a targeted volume for 30 minutes. In humans, careful patient selection and preparation will enable adequate targeting for recurrent rectal cancers and sufficient MR temperature mapping stability to control mild hyperthermia. These results enable human trials of MR-HIFU hyperthermia.

  19. Clinical outcome of magnetic-resonance-guided focused ultrasound surgery (MRgFUS) in the treatment of symptomatic uterine fibroids

    International Nuclear Information System (INIS)

    Kamp, J.E.K.; Scheurig-Muenkler, C.; Beck, A.; David, M.; Hengst, S.

    2013-01-01

    Purpose: To investigate the clinical outcome of magnetic-resonance-guided focused ultrasound surgery (MRgFUS) treatment for symptomatic uterine fibroids in premenopausal women using the validated USF-QOL (Uterine Fibroid Symptom and Quality of Life) Questionnaire. Materials and Methods: 54 patients with symptomatic uterine fibroids were enrolled in this prospective study. The patients completed the UFS-QOL Questionnaire prior to MRgFUS treatment as well as after 3, 6, and 12 months. Results: The rate of technical success was 91.5 % (95.2 % after subtraction of screening errors). 6/54 patients (11 %) had other treatments (surgery, n = 4; UAE, n = 2), 8/54 (15 %) dropped out due to pregnancy, and 8/54 were lost to follow-up. The remaining group showed considerable symptom relief as early as after 3 months. The median overall quality of life score increased from 64.7 (quartile range QR: 49.8 - 77.6) before treatment to 77.6 (QR: 61.4 - 87.1) (p < 0.001), 78.4 (QR: 66.4 - 89.7) (p < 0.001), and 82.8 (QR: 69.8 - 92.2) (p < 0.001) at 3, 6, and 12 months, respectively. The corresponding median symptom severity score decreased from 46.9 (QR: 28.1 - 56.2) to 34.4 (QR: 21.9 - 43.7) at 3 months (p = 0.003) and 28.1 at 6 and 12 months (QR: 18.7 - 38.3, QR: 15.6 - 34.4) (p < 0.001, p = 0.002). The rate of complications requiring treatment was 9 %, and the rate of overall complications was 39 %. No major complications occurred. Conclusion: Our results indicate significant alleviation of fibroid-related symptoms within 12 months of MRgFUS with improvement beginning as early as 3 months after treatment. We observed no major complications, and some women became pregnant after MRgFUS. There was a low treatment failure rate of 11 %. (orig.)

  20. Magnetic Resonance–Guided High-Intensity Focused Ultrasound Hyperthermia for Recurrent Rectal Cancer: MR Thermometry Evaluation and Preclinical Validation

    International Nuclear Information System (INIS)

    Chu, William; Staruch, Robert M.; Pichardo, Samuel; Tillander, Matti; Köhler, Max O.; Huang, Yuexi; Ylihautala, Mika; McGuffin, Merrylee; Czarnota, Gregory; Hynynen, Kullervo

    2016-01-01

    Purpose: To evaluate the feasibility of magnetic resonance–guided high-intensity focused ultrasound (MR-HIFU) mild hyperthermia in deep tissue targets for enhancing radiation therapy and chemotherapy in the context of recurrent rectal cancer. A preclinical study was performed to evaluate the safety and performance of MR-HIFU mild hyperthermia. A prospective imaging study was performed in volunteers with rectal cancer to evaluate MR thermometry quality near the rectum and accessibility of rectal tumors using MR-HIFU. Methods and Materials: Mild hyperthermia was performed in pig thigh (9 sonications, 6 pigs) using a clinical MR-HIFU system. Targets near the rectal wall and deep thigh were evaluated. Thermal maps obtained in 6 planes every 3.2 seconds were used to control sonications in 18-mm diameter treatment regions at temperatures of 42°C to 42.5°C for 10 to 60 minutes. Volunteer imaging-only studies to assess the quality of MR thermometry (without heating) were approved by the institutional research ethics board. Anatomic and MR thermometry images were acquired in consenting volunteers with rectal cancer. In 3 of 6 study participants, rectal filling with saline was used to reduce motion-related MR thermometry artifacts near the tumor. Results: In pigs, mean target temperature matched the desired hyperthermia temperature within 0.2°C; temporal standard deviation ≤0.5°C. With optimized control thresholds, no undesired tissue damage was observed. In human volunteers, MR temperature measurements had adequate precision and stability, especially when rectal filling was used to reduce bowel motion. Conclusions: In pigs, MR-HIFU can safely deliver mild hyperthermia (41°C-43°C) to a targeted volume for 30 minutes. In humans, careful patient selection and preparation will enable adequate targeting for recurrent rectal cancers and sufficient MR temperature mapping stability to control mild hyperthermia. These results enable human trials of MR-HIFU hyperthermia.

  1. Effects of magnetic resonance-guided high-intensity focused ultrasound ablation on bone mechanical properties and modeling.

    Science.gov (United States)

    Yeo, Sin Yuin; Arias Moreno, Andrés J; van Rietbergen, Bert; Ter Hoeve, Natalie D; van Diest, Paul J; Grüll, Holger

    2015-01-01

    Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a promising technique for palliative treatment of bone pain. In this study, the effects of MR-HIFU ablation on bone mechanics and modeling were investigated. A total of 12 healthy rat femurs were ablated using 10 W for 46 ± 4 s per sonication with 4 sonications for each femur. At 7 days after treatments, all animals underwent MR and single photon emission computed tomography/computed tomography (SPECT/CT) imaging. Then, six animals were euthanized. At 1 month following ablations, the remaining six animals were scanned again with MR and SPECT/CT prior to euthanization. Thereafter, both the HIFU-treated and contralateral control bones of three animals from each time interval were processed for histology, whereas the remaining bones were subjected to micro-CT (μCT), three-point bending tests, and micro-finite element (micro-FE) analyses. At 7 days after HIFU ablations, edema formation around the treated bones coupled with bone marrow and cortical bone necrosis was observed on MRI and histological images. SPECT/CT and μCT images revealed presence of bone modeling through an increased uptake of (99m)Tc-MDP and formation of woven bone, respectively. At 31 days after ablations, as illustrated by imaging and histology, healing of the treated bone and the surrounding soft tissue was noted, marked by decreased in amount of tissue damage, formation of scar tissue, and sub-periosteal reaction. The results of three-point bending tests showed no significant differences in elastic stiffness, ultimate load, and yield load between the HIFU-treated and contralateral control bones at 7 days and 1 month after treatments. Similarly, the elastic stiffness and Young's moduli determined by micro-FE analyses at both time intervals were not statistically different. Multimodality imaging and histological data illustrated the presence of HIFU-induced bone damage at the cellular level, which activated the

  2. [Magnetic resonance guided focused ultrasound surgery for pain palliation of bone metastases: early experience of clinical application in China].

    Science.gov (United States)

    Gu, Jianjun; Wang, Han; Tang, Na; Hua, Yingqi; Yang, Haiyan; Qiu, Yimin; Ge, Renbin; Zhou, Ying; Wang, Wenwen; Zhang, Guixiang

    2015-11-03

    To evaluate the safety and efficacy of magnetic resonance guided focused ultrasound surgery (MRgFUS) in treatment for pain palliation of bone metastases. Eighty-one patients of painful bone metastases were volunteered to screen for this study in Shanghai General Hospital from June 2014 to February 2015. Twenty-three patients among them were treated by MRgFUS, who was more than 18-years old, having the ability to fully understand the informed consent of the research, suffering with pain of numeric rating scale (NRS) ≥ 4, non-received radiotherapy or chemotherapy for pain palliation of bone metastases in the past two weeks. The NRS, the standard question of Brief Pain Inventory (BPI-QoL), and the standard question of Europe Organization for Research and Treatment of Cancer Quality of Life Questionnaire- Bone Metastases 22 (EORTC QLQ-BM22) were respectively recorded before and 1-week, 1-month, 3-month after the treatment. The related adverse events of MRgFUS were observed and recorded in 3 months after the treatment as well. (1)Twenty-three metastatic bone tumor lesions of 23 patients were treated by MRgFUS, the treatment data was as follows: the mean treatment time was (88 ± 33) minutes, the mean sonication number was 13 ± 8. (2) Adverse events included: pain in therapy area 3/23, which spontaneous relieving within one week; numbness in lower limb (1/23), which relieved after physiotherapy. (3) The NRS of before treatment and at 1-week, 1-month, and 3-month after treatment respectively was 6.0 ± 1.5, 3.7 ± 1.7,3.1 ± 2.0, and 2.2 ± 1.0,which significantly decreased after the treatment (P<0.01). (4) The BPI-QoL score of before treatment and at 1-week, 1-month, and 3-month after treatment respectively was 39 ± 16, 27 ± 18, 26 ± 18, and 21 ± 18, which significantly decreased after the treatment (P<0.01). (5) The EORTC QLQ-BM22 score of before treatment and at 1-week, 1-month, and 3-month after treatment respectively was 52 ± 13, 44 ± 12, 42 ± 12, and 39

  3. A magnetic-based dispersive micro-solid-phase extraction method using the metal-organic framework HKUST-1 and ultra-high-performance liquid chromatography with fluorescence detection for determining polycyclic aromatic hydrocarbons in waters and fruit tea infusions.

    Science.gov (United States)

    Rocío-Bautista, Priscilla; Pino, Verónica; Ayala, Juan H; Pasán, Jorge; Ruiz-Pérez, Catalina; Afonso, Ana M

    2016-03-04

    A hybrid material composed by the metal-organic framework (MOF) HKUST-1 and Fe3O4 magnetic nanoparticles (MNPs) has been synthetized in a quite simple manner, characterized, and used in a magnetic-assisted dispersive micro-solid-phase extraction (M-d-μSPE) method in combination with ultra-high-performance liquid chromatography (UHPLC) and fluorescence detection (FD). The application was devoted to the determination of 8 heavy polycyclic aromatic hydrocarbons (PAHs) in different aqueous samples, specifically tap water, wastewaters, and fruit tea infusion samples. The overall M-d-μSPE-UHPLC-FD method was optimized and validated. The method is characterized by: its simplicity in both the preparation of the hybrid material (simple mixing) and the magnetic-assisted approach (∼10min extraction time), the use of low sorbent amounts (20mg of HKUST-1 and 5mg of Fe3O4 MNPs), and the low organic solvent consumption in the overall M-d-μSPE-UHPLC-FD method (1.5mL of acetonitrile in the M-d-μSPE method and 2.8mL of acetonitrile in the UHPLC-FD run). The resulting method has high sensitivity, with LODs down to 0.8ngL(-1); adequate intermediate precision, with relative standard deviation values (RSD) always lower than 6.3% (being the range 5.9-9.0% in tap water for a spiked level of 45ngL(-1), 6.1-14% in wastewaters for a spiked level of 45ngL(-1), and 7.2-17% in fruit tea infusion samples for a spiked level of 45ngL(-1)); and adequate relative recoveries, with average values of 82% in tap water, and 94% and 75% in wastewater and fruit tea infusion samples, respectively, if using the proper matrix-matched calibration. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Successful Use of Magnetic Resonance-Guided Focused Ultrasound Surgery for Long-Term Pain Palliation in a Patient Suffering from Metastatic Bone Tumor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ji Eun; Yoon, Sang Wook; Kim, Kyoung Ah; Lee, Jong Tae [Dept. of Diagnostic Radiology, CHA Bundang Medical Center, CHA University College of Medicine, Seongnam (Korea, Republic of); Shay, Lilach [InSightec. Ltd, Hifa, (Israel); Lee, Kyong Sik [Dept. of General Surgery, CHA Bundang Medical Center, CHA University College of Medicine, Seongnam (Korea, Republic of)

    2011-08-15

    Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) is a clinically effective, non-invasive treatment for thermal ablation of various soft tissue tumors, and is effective in pain palliation following radiation therapy, as has been demonstrated in the initial studies of bone metastases. The current study evaluated the safety and clinical efficacy of MRgFUS for pain palliation prior to radiation therapy, in a patient with a solitary metastatic bone lesion. This is the first case report of MRgFUS treatment with a 1-year follow-up in a patient.

  5. Successful Use of Magnetic Resonance-Guided Focused Ultrasound Surgery for Long-Term Pain Palliation in a Patient Suffering from Metastatic Bone Tumor

    International Nuclear Information System (INIS)

    Lee, Ji Eun; Yoon, Sang Wook; Kim, Kyoung Ah; Lee, Jong Tae; Shay, Lilach; Lee, Kyong Sik

    2011-01-01

    Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) is a clinically effective, non-invasive treatment for thermal ablation of various soft tissue tumors, and is effective in pain palliation following radiation therapy, as has been demonstrated in the initial studies of bone metastases. The current study evaluated the safety and clinical efficacy of MRgFUS for pain palliation prior to radiation therapy, in a patient with a solitary metastatic bone lesion. This is the first case report of MRgFUS treatment with a 1-year follow-up in a patient.

  6. Ultra-Compact 100 × 100 μm2 Footprint Hybrid Device with Spin-Valve Nanosensors

    Directory of Open Access Journals (Sweden)

    Diana C. Leitao

    2015-12-01

    Full Text Available Magnetic field mapping with micrometric spatial resolution and high sensitivity is a challenging application, and the technological solutions are usually based on large area devices integrating discrete magnetic flux guide elements. In this work we demonstrate a high performance hybrid device with improved field sensitivity levels and small footprint, consisting of a ultra-compact 2D design where nanometric spin valve sensors are inserted within the gap of thin-film magnetic flux concentrators. Pole-sensor distances down to 400 nm are demonstrated using nanofabrication techniques combined with an optimized liftoff process. These 100 × 100 μm 2 pixel sensors can be integrated in modular devices for surface mapping without moving parts.

  7. Ab initio understanding of magnetic properties in Zn2+ substitution of Fe3O4 ultra-thin film with dilute Zn substitution

    Science.gov (United States)

    Huang, Zhaocong; Chen, Qian; Jiang, Sheng; Dong, Shuai; Zhai, Ya

    2018-05-01

    The mechanism of the magnetic properties on the Zn2+ substituted Fe3O4 film have been investigated based on first principle calculations. It is found that the surface effect plays an important role in the occupation of Zn ion, and in turn changes the magnetic moment. It may also destroy the half metallic behavior of Fe3O4 film even if the Zn2+ concentration only is one Zn2+ per unit cell (4%), which is different from that in bulk material.

  8. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  9. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  10. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  11. Ultra-sensitive chemiluminescent detection of Staphylococcus aureus based on competitive binding of Staphylococcus protein A-modified magnetic beads to immunoglobulin G

    International Nuclear Information System (INIS)

    Xiong, Jie; Wang, Wenwen; Zhou, Yali; Kong, Weijun; Wang, Zhenxing; Fu, Zhifeng

    2016-01-01

    Staphylococcus protein A (SPA) is a surface protein only expressed naturally in the cell walls of Staphylococcus aureus (S. aureus) and binds specifically to the Fc region of immunoglobulin G (IgG). This fact can be utilized for the detection of S. aureus. Specifically, SPA-modified magnetic beads, compete with S. aureus pathogens for binding to rabbit IgG that previously was labeled with horseradish peroxidase (HRP). The beads were then magnetically separated, and chemiluminescence (CL) was generated by adding the reagents luminol and H_2O_2. Under optimal conditions, the intensity of CL decreases with increasing concentration of S. aureus over a very wide linear range (10 to 1.0 × 10"9 cfu·mL"−"1), with a limit of detection of 6.0 cfu·mL"−"1 at an S/N ratio of 3. The assay (including binding reaction, magnetic separation, washing of beads and detection) is completed within 50 min which is faster than many reported methods. It can well distinguish S. aureus from other Gram-positive and Gram-negative bacteria. The magnetic beads have the beneficial effect of eliminating undesired matrix effects and of concentrating the sample. The method was applied to the analysis of urine, apple juice and glucose injection samples spiked with S. aureus, and recoveries ranged from 85 to 107 %. (author)

  12. Towards real-time cardiovascular magnetic resonance-guided transarterial aortic valve implantation: In vitro evaluation and modification of existing devices

    Directory of Open Access Journals (Sweden)

    Ladd Mark E

    2010-10-01

    Full Text Available Abstract Background Cardiovascular magnetic resonance (CMR is considered an attractive alternative for guiding transarterial aortic valve implantation (TAVI featuring unlimited scan plane orientation and unsurpassed soft-tissue contrast with simultaneous device visualization. We sought to evaluate the CMR characteristics of both currently commercially available transcatheter heart valves (Edwards SAPIEN™, Medtronic CoreValve® including their dedicated delivery devices and of a custom-built, CMR-compatible delivery device for the Medtronic CoreValve® prosthesis as an initial step towards real-time CMR-guided TAVI. Methods The devices were systematically examined in phantom models on a 1.5-Tesla scanner using high-resolution T1-weighted 3D FLASH, real-time TrueFISP and flow-sensitive phase-contrast sequences. Images were analyzed for device visualization quality, device-related susceptibility artifacts, and radiofrequency signal shielding. Results CMR revealed major susceptibility artifacts for the two commercial delivery devices caused by considerable metal braiding and precluding in vivo application. The stainless steel-based Edwards SAPIEN™ prosthesis was also regarded not suitable for CMR-guided TAVI due to susceptibility artifacts exceeding the valve's dimensions and hindering an exact placement. In contrast, the nitinol-based Medtronic CoreValve® prosthesis was excellently visualized with delineation even of small details and, thus, regarded suitable for CMR-guided TAVI, particularly since reengineering of its delivery device toward CMR-compatibility resulted in artifact elimination and excellent visualization during catheter movement and valve deployment on real-time TrueFISP imaging. Reliable flow measurements could be performed for both stent-valves after deployment using phase-contrast sequences. Conclusions The present study shows that the Medtronic CoreValve® prosthesis is potentially suited for real-time CMR-guided placement

  13. Magnetic resonance tomography-guided interventional procedure for diagnosis of prostate cancer; MRT-gezielte interventionelle Verfahren zur Abklaerung des Prostatakarzinoms

    Energy Technology Data Exchange (ETDEWEB)

    Schernthaner, M.; Helbich, T.H.; Fueger, B.J.; Memarsadeghi, M.; Stiglbauer, A.; Linhart, H.G.; Doan, A.; Pinker, K.; Brader, P. [Medizinische Universitaet Wien, Univ.-Klinik fuer Radiodiagnostik, Division fuer Molekulare und Gender-Bildgebung, Wien (Austria); Margreiter, M. [Medizinische Universitaet Wien, Univ.-Klinik fuer Urologie, Wien (Austria)

    2011-11-15

    In recent years magnetic resonance imaging (MRI) has been increasingly established in the diagnosis of prostate cancer in addition to transrectal ultrasonography (TRUS). The use of T2-weighted imaging allows an exact delineation of the zonal anatomy of the prostate and its surrounding structures. Other MR imaging tools, such as dynamic contrast-enhanced T1-weighted imaging or diffusion-weighted imaging allow an inference of the biochemical characteristics (multiparametric MRI). Prostate cancer, which could only be diagnosed using MR imaging or lesions suspected as being prostate cancer, which are localized in the anterior aspect of the prostate and were missed with repetitive TRUS biopsy, need to undergo MR guided biopsy. Recent studies have shown a good correlation between MR imaging and histopathology of specimens collected by MR-guided biopsy. Improved lesion targeting is therefore possible with MR-guided biopsy. So far data suggest that MR-guided biopsy of the prostate is a promising alternative diagnostic tool to TRUS-guided biopsy. (orig.) [German] Neben dem transrektalen Ultraschall (TRUS) hat sich in den letzten Jahren die MRT als nichtinvasive Methode zur Bildgebung von Prostatatumoren etabliert. Mittels T2-gewichteter Sequenzen ist eine exakte anatomische Darstellung der Prostata und ihrer umliegenden Strukturen moeglich. Andere MRT-Techniken ermoeglichen Rueckschluesse auf das biologische Verhalten des Tumors: dynamische kontrastmittelverstaerkte T1-gewichtete Sequenzen zur Darstellung der Angiogenese, diffusionsgewichtete Aufnahmen zur Beurteilung der Zelldichte und die Spektroskopie zur Bestimmung von Gewebemetaboliten wie Cholin und Kreatin (multiparametrische Bildgebung). Prostatatumoren, die nur mittels MRT nachweisbar sind oder verdaechtige Tumoren, die hauptsaechlich anterior in der Prostata lokalisiert sind und in wiederholten TRUS-gezielten Biopsien verfehlt wurden, benoetigen eine MRT-gezielte Biopsie zur Diagnosesicherung. Die bisherigen

  14. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  15. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  16. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  17. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  18. Test of Shi et al. Method to Infer the Magnetic Reconnection Geometry from Spacecraft Data: MHD Simulation with Guide Field and Antiparallel Kinetic Simulation

    Science.gov (United States)

    Denton, R.; Sonnerup, B. U. O.; Swisdak, M.; Birn, J.; Drake, J. F.; Heese, M.

    2012-01-01

    When analyzing data from an array of spacecraft (such as Cluster or MMS) crossing a site of magnetic reconnection, it is desirable to be able to accurately determine the orientation of the reconnection site. If the reconnection is quasi-two dimensional, there are three key directions, the direction of maximum inhomogeneity (the direction across the reconnection site), the direction of the reconnecting component of the magnetic field, and the direction of rough invariance (the "out of plane" direction). Using simulated spacecraft observations of magnetic reconnection in the geomagnetic tail, we extend our previous tests of the direction-finding method developed by Shi et al. (2005) and the method to determine the structure velocity relative to the spacecraft Vstr. These methods require data from four proximate spacecraft. We add artificial noise and calibration errors to the simulation fields, and then use the perturbed gradient of the magnetic field B and perturbed time derivative dB/dt, as described by Denton et al. (2010). Three new simulations are examined: a weakly three-dimensional, i.e., quasi-two-dimensional, MHD simulation without a guide field, a quasi-two-dimensional MHD simulation with a guide field, and a two-dimensional full dynamics kinetic simulation with inherent noise so that the apparent minimum gradient was not exactly zero, even without added artificial errors. We also examined variations of the spacecraft trajectory for the kinetic simulation. The accuracy of the directions found varied depending on the simulation and spacecraft trajectory, but all the directions could be found within about 10 for all cases. Various aspects of the method were examined, including how to choose averaging intervals and the best intervals for determining the directions and velocity. For the kinetic simulation, we also investigated in detail how the errors in the inferred gradient directions from the unmodified Shi et al. method (using the unperturbed gradient

  19. Five degree-of-freedom control of an ultra-precision magnetically-suspended linear bearing. Ph.D. Thesis - MIT

    Science.gov (United States)

    Trumper, David L.; Slocum, A. H.

    1991-01-01

    The authors constructed a high precision linear bearing. A 10.7 kg platen measuring 125 mm by 125 mm by 350 mm is suspended and controlled in five degrees of freedom by seven electromagnets. The position of the platen is measured by five capacitive probes which have nanometer resolution. The suspension acts as a linear bearing, allowing linear travel of 50 mm in the sixth degree of freedom. In the laboratory, this bearing system has demonstrated position stability of 5 nm peak-to-peak. This is believed to be the highest position stability yet demonstrated in a magnetic suspension system. Performance at this level confirms that magnetic suspensions can address motion control requirements at the nanometer level. The experimental effort associated with this linear bearing system is described. Major topics are the development of models for the suspension, implementation of control algorithms, and measurement of the actual bearing performance. Suggestions for the future improvement of the bearing system are given.

  20. Radio frequency self-resonant coil for contactless AC-conductivity in 100 T class ultra-strong pulse magnetic fields

    Science.gov (United States)

    Nakamura, D.; Altarawneh, M. M.; Takeyama, S.

    2018-03-01

    A contactless measurement system of electrical conductivity was developed for application under pulsed high magnetic fields over 100 T by using a self-resonant-type, high-frequency circuit. Electromagnetic fields in the circuit were numerically analysed by the finite element method, to show how the resonant power spectra of the circuit depends on the electrical conductivity of a sample set on the probe-coil. The performance was examined using a high-temperature cuprate superconductor, La2-x Sr x CuO4, in magnetic fields up to 102 T with a high frequency of close to 800 MHz. As a result, the upper critical field could be determined with a good signal-to-noise ratio.

  1. Experimental Investigation of Magnetic Superconducting, and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures Using Designer Diamond Anvils

    International Nuclear Information System (INIS)

    Maple, M. Brian

    2005-01-01

    Pressure is a powerful control parameter, owing to its ability to affect crystal and electronic structure without introducing defects, for the investigation of condensed matter systems. Some f-electron, heavy-fermion materials display interesting and novel behavior when exposed to pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require extreme conditions such as ultrahigh pressures, high magnetic fields, and ultralow temperatures to sufficiently explore the important properties. To that end, we have been funded to develop an ultrahigh pressure facility at the University of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena under extreme conditions. Our goals for the second year of this grant were as follows: (a) perform electrical resistivity measurements on novel samples at a myriad of pressures using conventional piston-cylinder techniques, Bridgman anvil techniques, and diamond anvil cell technology; (b) install, commission, and operate an Oxford Kelvinox MX-100 dilution refrigerator for access to ultralow temperatures and high magnetic fields. (c) continue the development of diamond anvil cell (DAC) technology. During the past year, we have successfully installed the Oxford Kelvinox MX-100 dilution refrigerator and verified its operability down to 12 mK. We have begun an experimental program to systematically investigate the f-electron compound URu2Si2 under pressure and in the presence of magnetic fields. We have also continued our collaborative work with Sam Weir at Lawrence Livermore National Laboratory (LLNL) on Au4V and implemented a new corollary study on Au1-xVx using ultrahigh pressures. We have continued developing our DAC facility by designing and constructing an apparatus for in situ pressure measurement as well as designing high pressure cells. This report serves to highlight the progress we have made

  2. Ferumoxtran-10 advanced magnetics.

    NARCIS (Netherlands)

    Leenders, W.P.J.

    2003-01-01

    Ferumoxtran-10 (Combidex) is an ultra-small superparamagnetic iron oxide molecular resonance imaging contrast agent under development by Advanced Magnetics Ltd and Guerbet for the principal indication of lymph node imaging.

  3. Near-infrared magneto-optical study of excitonic states in single-walled carbon nanotubes under ultra-high magnetic fields

    International Nuclear Information System (INIS)

    Yokoi, H; Effendi, Mukhtar; Minami, N; Takeyama, S

    2011-01-01

    Singlet excitonic states at the first subband-edge in single-walled carbon nanotubes (SWCNTs) have been studied through near-infrared magneto-absorption spectroscopy under magnetic fields to 105.9 T. Well-resolved absorption spectra of stretch-aligned SWCNT(CoMoCAT)-gelatin films were obtained above 100 T. By the application of magnetic fields in parallel to the alignment of SWCNTs, peak shift toward the lower energy was observed for (8, 4) and (7, 6) tubes and the opposite behavior was observed for (7, 5) and (6, 5) tubes. Above 28.8 T, new peaks emerged at the higher energy side of the peak for the (8, 4) and (7, 6) tubes, and at the lower energy side of the peaks for the (7, 5) and (6, 5) tubes. The magnetic splitting between the existing peak and the new peak was symmetric for every tube, which is in line with the energy splitting due to the Aharonov-Bohm effect. Judging from the energetic positions where the new peaks emerged, the singlet dark excitonic state locates at the lower energy than the singlet bright one in the (7, 5) and (6, 5) tubes while it is suggested strongly that the bright one locates at the lower energy in the (8, 4) and (7, 6) tubes.

  4. Giant voltage manipulation of MgO-based magnetic tunnel junctions via localized anisotropic strain: A potential pathway to ultra-energy-efficient memory technology

    Science.gov (United States)

    Zhao, Zhengyang; Jamali, Mahdi; D'Souza, Noel; Zhang, Delin; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha; Wang, Jian-Ping

    2016-08-01

    Voltage control of magnetization via strain in piezoelectric/magnetostrictive systems is a promising mechanism to implement energy-efficient straintronic memory devices. Here, we demonstrate giant voltage manipulation of MgO magnetic tunnel junctions (MTJ) on a Pb(Mg1/3Nb2/3)0.7Ti0.3O3 piezoelectric substrate with (001) orientation. It is found that the magnetic easy axis, switching field, and the tunnel magnetoresistance (TMR) of the MTJ can be efficiently controlled by strain from the underlying piezoelectric layer upon the application of a gate voltage. Repeatable voltage controlled MTJ toggling between high/low-resistance states is demonstrated. More importantly, instead of relying on the intrinsic anisotropy of the piezoelectric substrate to generate the required strain, we utilize anisotropic strain produced using a local gating scheme, which is scalable and amenable to practical memory applications. Additionally, the adoption of crystalline MgO-based MTJ on piezoelectric layer lends itself to high TMR in the strain-mediated MRAM devices.

  5. Removal of acidic interferences in multi-pesticides residue analysis of fruits using modified magnetic nanoparticles prior to determination via ultra-HPLC-MS/MS

    International Nuclear Information System (INIS)

    Qi, Peipei; Wang, Zhiwei; Yang, Guiling; Wang, Xinquan; Shang, Chunqing; Xu, Hao; Wang, Xiangyun; Zhang, Hu; Wang, Qiang

    2015-01-01

    The authors describe magnetite (Fe 3 O 4 ) nanoparticles modified with 3-(N,N-diethylamino) propyltrimethoxysilane (Fe 3 O 4 -PSA NPs) for use as a sorbent for dispersive solid phase extraction of pesticide residues. The Fe 3 O 4 -PSA NPs were prepared by silanizing Fe 3 O 4 NPs and modifying them with 3-(N,N-diethylamino) propyltrimethoxysilane. Field-emission scanning electron microscopy, FTIR and zeta potential measurements were employed to characterize the modified NPs. They were then used as an adsorbent to remove acidic interferences (such as malic acid and succinic acid), which are major interferences in LC-MS/MS analysis in causing ion suppression in the MS spectra of pesticides. In addition, graphitized carbon black (GCB) was used as an adsorbent to eliminate interferences by pigments. The use of Fe 3 O 4 -PSA NPs can replace time-consuming centrifugation as used in the so-called QuEChERS (quick, easy, cheap, effective, rugged and safe) method. This improvement is particularly significant in high-throughput analysis. Following the optimization of the quantities of Fe 3 O 4 -PSA NPs and GCB, the method was applied to the determination of 56 pesticides in (spiked) fruits (apple, kiwi, orange and pear) by ultra-HPLC-MS/MS. The analytical ranges typically extend from 1 to 200 ng∙mL −1 , and recoveries range from 60.2 to 130 % at different concentrations of all four kinds of fruits. The LOQs for the pesticides are 10 ng∙kg −1 , which makes the method a viable tool for pesticide monitoring in fruits. (author)

  6. Technical Note: Error metrics for estimating the accuracy of needle/instrument placement during transperineal magnetic resonance/ultrasound-guided prostate interventions.

    Science.gov (United States)

    Bonmati, Ester; Hu, Yipeng; Villarini, Barbara; Rodell, Rachael; Martin, Paul; Han, Lianghao; Donaldson, Ian; Ahmed, Hashim U; Moore, Caroline M; Emberton, Mark; Barratt, Dean C

    2018-04-01

    Image-guided systems that fuse magnetic resonance imaging (MRI) with three-dimensional (3D) ultrasound (US) images for performing targeted prostate needle biopsy and minimally invasive treatments for prostate cancer are of increasing clinical interest. To date, a wide range of different accuracy estimation procedures and error metrics have been reported, which makes comparing the performance of different systems difficult. A set of nine measures are presented to assess the accuracy of MRI-US image registration, needle positioning, needle guidance, and overall system error, with the aim of providing a methodology for estimating the accuracy of instrument placement using a MR/US-guided transperineal approach. Using the SmartTarget fusion system, an MRI-US image alignment error was determined to be 2.0 ± 1.0 mm (mean ± SD), and an overall system instrument targeting error of 3.0 ± 1.2 mm. Three needle deployments for each target phantom lesion was found to result in a 100% lesion hit rate and a median predicted cancer core length of 5.2 mm. The application of a comprehensive, unbiased validation assessment for MR/US guided systems can provide useful information on system performance for quality assurance and system comparison. Furthermore, such an analysis can be helpful in identifying relationships between these errors, providing insight into the technical behavior of these systems. © 2018 American Association of Physicists in Medicine.

  7. Application of a highly sensitive magnetic solid phase extraction for phytochemical compounds in medicinal plant and biological fluids by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry.

    Science.gov (United States)

    Cao, Wan; Yi, Ling; Ye, Li-Hong; Cao, Jun; Hu, Shuai-Shuai; Xu, Jing-Jing; Peng, Li-Qing; Zhu, Qiong-Yao; Zhang, Qian-Yun

    2015-10-01

    A highly sensitive method using reduced graphene oxide with iron oxide (rGO/Fe3 O4 ) as the sorbent in magnetic SPE has been developed for the purification of five anthraquinones (emodin, rhein, aloeemodin, physcion, and chrysophanol) in rhubarb and rat urine by ultra-HPLC coupled with quadrupole TOF/MS. The extraction was accomplished by adding trace amount rGO/Fe3 O4 suspension to 200 mL of aqueous mixture, and the excellent adsorption capacity of the nanoparticles was fully demonstrated in this procedure. Under the optimized conditions, the calibration curves were linear in the concentration range of 0.05-27.77 ng/mL with correlation coefficients varying from 0.9902 to 0.9978. The LODs ranged from 0.28 to 58.99 pg/mL. The experimental results indicated that the proposed method was feasible for the analysis of anthraquinones in rhubarb and urine samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Cervical Gross Tumor Volume Dose Predicts Local Control Using Magnetic Resonance Imaging/Diffusion-Weighted Imaging—Guided High-Dose-Rate and Positron Emission Tomography/Computed Tomography—Guided Intensity Modulated Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Dyk, Pawel; Jiang, Naomi; Sun, Baozhou; DeWees, Todd A. [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Fowler, Kathryn J.; Narra, Vamsi [Department of Diagnostic Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri (United States); Garcia-Ramirez, Jose L.; Schwarz, Julie K. [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Grigsby, Perry W., E-mail: pgrigsby@wustl.edu [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri (United States); Division of Gynecologic Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri (United States); Alvin J. Siteman Cancer Center, Washington University School of Medicine, St Louis, Missouri (United States)

    2014-11-15

    Purpose: Magnetic resonance imaging/diffusion weighted-imaging (MRI/DWI)-guided high-dose-rate (HDR) brachytherapy and {sup 18}F-fluorodeoxyglucose (FDG) — positron emission tomography/computed tomography (PET/CT)-guided intensity modulated radiation therapy (IMRT) for the definitive treatment of cervical cancer is a novel treatment technique. The purpose of this study was to report our analysis of dose-volume parameters predicting gross tumor volume (GTV) control. Methods and Materials: We analyzed the records of 134 patients with International Federation of Gynecology and Obstetrics stages IB1-IVB cervical cancer treated with combined MRI-guided HDR and IMRT from July 2009 to July 2011. IMRT was targeted to the metabolic tumor volume and lymph nodes by use of FDG-PET/CT simulation. The GTV for each HDR fraction was delineated by use of T2-weighted or apparent diffusion coefficient maps from diffusion-weighted sequences. The D100, D90, and Dmean delivered to the GTV from HDR and IMRT were summed to EQD2. Results: One hundred twenty-five patients received all irradiation treatment as planned, and 9 did not complete treatment. All 134 patients are included in this analysis. Treatment failure in the cervix occurred in 24 patients (18.0%). Patients with cervix failures had a lower D100, D90, and Dmean than those who did not experience failure in the cervix. The respective doses to the GTV were 41, 58, and 136 Gy for failures compared with 67, 99, and 236 Gy for those who did not experience failure (P<.001). Probit analysis estimated the minimum D100, D90, and Dmean doses required for ≥90% local control to be 69, 98, and 260 Gy (P<.001). Conclusions: Total dose delivered to the GTV from combined MRI-guided HDR and PET/CT-guided IMRT is highly correlated with local tumor control. The findings can be directly applied in the clinic for dose adaptation to maximize local control.

  9. Operation of a 400MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7-x high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1GHz.

    Science.gov (United States)

    Yanagisawa, Y; Piao, R; Iguchi, S; Nakagome, H; Takao, T; Kominato, K; Hamada, M; Matsumoto, S; Suematsu, H; Jin, X; Takahashi, M; Yamazaki, T; Maeda, H

    2014-12-01

    High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1GHz (23.5T). (RE)Ba 2 Cu 3 O 7- x (REBCO, RE: rare earth) conductors have an advantage over Bi 2 Sr 2 Ca 2 Cu 3 O 10- x (Bi-2223) and Bi 2 Sr 2 CaCu 2 O 8- x (Bi-2212) conductors in that they have very high tensile strengths and tolerate strong electromagnetic hoop stress, thereby having the potential to act as an ultra-compact super-high field NMR magnet. As a first step, we developed the world's first NMR magnet comprising an inner REBCO coil and outer low-temperature superconducting (LTS) coils. The magnet was successfully charged without degradation and mainly operated at 400MHz (9.39T). Technical problems for the NMR magnet due to screening current in the REBCO coil were clarified and solved as follows: (i) A remarkable temporal drift of the central magnetic field was suppressed by a current sweep reversal method utilizing ∼10% of the peak current. (ii) A Z2 field error harmonic of the main coil cannot be compensated by an outer correction coil and therefore an additional ferromagnetic shim was used. (iii) Large tesseral harmonics emerged that could not be corrected by cryoshim coils. Due to those harmonics, the resolution and sensitivity of NMR spectra are ten-fold lower than those for a conventional LTS NMR magnet. As a result, a HSQC spectrum could be achieved for a protein sample, while a NOESY spectrum could not be obtained. An ultra-compact 1.2GHz NMR magnet could be realized if we effectively take advantage of REBCO conductors, although this will require further research to suppress the effect of the screening current. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  11. Regional gravity and magnetic surveys along southern margin of Indravati basin, Central India - a guide to unconformity related uranium mineralisation

    International Nuclear Information System (INIS)

    Patra, I.; Ramesh Babu, V.; Chaturvedi, A.K.; Sreenivas, R.; Chari, M.N.; Dash, J.K.; Roy, M.K.

    2009-01-01

    Geophysical methods play vital role at various stages in mineral exploration programme particularly in case of buried deposits. The unconformity related uranium deposits owing to their concealed nature are explored by geophysical methods as an indirect tool. Regional ground gravity and magnetic surveys have been conducted to decipher the basin configuration, presence of fault/ fractures and basic activity. These structural features may form favorable criteria for mineralisation. Qualitative and quantitative interpretation of the gravity and magnetic data along the southern margin of Mesoproterozoic Indravati basin has been correlated with ground follow up geological investigation. There exists a good correlation between interpreted faults, fracture zones and mafic activity from the magnetic and gravity surveys with available borehole data in the area. Further, 2D models generated from magnetic data have paved the way for planning boreholes and thereby reorienting the sub-surface exploration programme. Evidence of alteration and fracturing intercepted from the borehole correlates well with the low gravity and magnetic. Hence, gravity and magnetic surveys can be effectively utilized in delineating basement configuration and to estimate sediment thickness besides deciphering post sedimentary fault/fractures which are favorable factors for unconformity related uranium mineralisation. (author)

  12. Ultra-small and broadband polarization splitters based on double-slit interference

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Chengwei; Li, Hongyun [State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, Department of Physics, Peking University, Beijing 100871 (China); Gong, Qihuang; Chen, Jianjun, E-mail: jjchern@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China)

    2016-03-07

    An ultra-small and broadband polarization splitter is numerically and experimentally demonstrated based on the double-slit interference in a polymer-film-coated double-slit structure. The hybrid slab waveguide (air-polymer-Au) supports both the transverse-magnetic and transverse-electric modes. The incident beam from the back side can excite these two guided modes of orthogonally polarized states in the hybrid structure. By exploiting the difference slit widths and the large mode birefringence, these two guided modes propagate to the opposite directions along the front metal surface. Moreover, the short interference length broadens the operation bandwidth. Experimentally, a polarization splitter with a lateral dimension of only about 1.6 μm and an operation bandwidth of 50 nm is realized. By designing the double-slit structure in a hybrid strip waveguide, the device dimension can be significant downscaled to about 0.3 × 1.3 μm{sup 2}. Such an ultra-small and broadband polarization splitter may find important applications in the integrated photonic circuits.

  13. Cone beam computed tomography guided treatment delivery and planning verification for magnetic resonance imaging only radiotherapy of the brain

    DEFF Research Database (Denmark)

    Edmund, Jens M.; Andreasen, Daniel; Mahmood, Faisal

    2015-01-01

    CT (CBCT) can be used for MRI-only image-guided radiotherapy (IGRT) and for verifying the correctness of the corresponding pCT. Material and methods. Six patients receiving palliative cranial RT were included in the study. Each patient had three-dimensional (3D) T1W MRI, a CBCT and a CT for reference...

  14. Surgical neuro navigator guided by preoperative magnetic resonance images, based on a magnetic position sensor;Neuronavegador cirurgico guiado por imagens de ressonancia magnetica pre-operatoria, baseado num transdutor de posicao magnetico

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana Paula; Siqueira, Rogerio Bulha; Carneiro, Antonio Adilton Oliveira, E-mail: adilton@ffclrp.usp.b [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras. Dept. de Fisica e Matematica; Oliveira, Lucas Ferrari de [Universidade Federal de Pelotas (UFPel), RS (Brazil). Dept. de Informatica; Machado, Helio Rubens [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Faculdade de Medicina. Dept. de Neurocirurgia

    2009-08-15

    Image guided neurosurgery enables the neurosurgeon to navigate inside the patient's brain using pre-operative images as a guide and a tracking system, during a surgery. Following a calibration procedure, three-dimensional position and orientation of surgical instruments may be transmitted to computer. The spatial information is used to access a region of interest, in the pre-operative images, displaying them to the neurosurgeon during the surgical procedure. However, when a craniotomy is involved and the lesion is removed, movements of brain tissue can be a significant source of error in these conventional navigation systems. The architecture implemented in this work intends the development of a system to surgical planning and orientation guided by ultrasound image. For surgical orientation, the software developed allows the extraction of slices from the volume of the magnetic resonance images (MRI) with orientation supplied by a magnetic position sensor (Polhemus{sup R}). The slices extracted with this software are important because they show the cerebral area that the neurosurgeon is observing during the surgery, and besides they can be correlated with the intra-operative ultrasound images to detect and to correct the deformation of brain tissue during the surgery. Also, a tool for per-operative navigation was developed, providing three orthogonal planes through the image volume. In the methodology used for the software implementation, the Python{sup tm} programming language and the Visualization Toolkit (VTK) graphics library were used. The program to extract slices of the MRI volume allowed the application of transformations in the volume, using coordinates supplied by the position sensor. (author)

  15. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  16. MAGNET

    CERN Multimedia

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  17. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  18. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  19. Experimental Investigation of Magnetic Superconducting and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures using Designer Diamond Anvils

    International Nuclear Information System (INIS)

    Maple, M. Brian; Jeffries, Jason R.; Ho, Pei-Chun; Butch, Nicholas P.

    2004-01-01

    Pressure is often used as a controlled parameter for the investigation of condensed matter systems. In particular, pressure experiments can provide valuable information into the nature of superconductivity, magnetism, and the coexistence of these two phenomena. Some f-electron, heavy-fermion materials display interesting and novel behavior at moderately low pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require ultrahigh pressure techniques, techniques that generate significantly higher pressures than conventional methods, to sufficiently explore their important properties. To that end, we have been funded to develop an ultrahigh pressure diamond anvil cell facility at the University of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena. Our goals for the first year of this grant were as follows: (a) set up and test a suitable refrigerator; (b) set up a laser and spectrometer fluorescence system to determine the pressure within the diamond anvil cell; (c) perform initial resistivity measurements at moderate pressures from room temperature to liquid helium temperatures (∼1K); (d) investigate f-electron materials within our current pressure capabilities to find candidate materials for high-pressure studies. During the past year, we have ordered almost all the components required to set up a diamond anvil cell facility at UCSD, we have received and implemented many of the components that have been ordered, we have performed low pressure research on several materials, and we have engaged in a collaborative effort with Sam Weir at Lawrence Livermore National Lab (LLNL) to investigate Au4V under ultrahigh pressure in a designer diamond anvil cell (dDAC). This report serves to highlight the progress we have made towards developing an ultrahigh pressure research facility at UCSD, the research performed in the past year, as

  20. Graphene Oxide and Gadolinium-Chelate Functionalized Poly(lactic acid) Nanocapsules Encapsulating Perfluorooctylbromide for Ultrasound/Magnetic Resonance Bimodal Imaging Guided Photothermal Ablation of Cancer.

    Science.gov (United States)

    Li, Zhenglin; Ke, Hengte; Wang, Jinrui; Miao, Zhaohua; Yue, Xiuli

    2016-03-01

    This paper successfully fabricated a novel multifunctional theranostic agent (PFOB@PLA/GO/Gd-DTPA NCs) by loading perfluorooctylbromide (PFOB) into poly(lactic acid) (PLA) nanocapsules (NCs) followed by surface functionalization with graphene oxide (GO) and gadolinium-chelate (Gd-DTPA). It was found that the resulting nanoagent could serve as a contrast agent simultaneously to enhance ultrasound (US) and magnetic resonance imaging (MRI). Benefiting from the strong absorption in the near infrared (NIR) region, the nanocapsules could efficiently kill cancer cells under NIR laser irradiation. Thus, such a single theranostic agent with the combination of realtime US imaging and high-resolution MR imaging could achieve great therapeutic effectiveness without systemic damage to the body. In addition, the cytotoxicity assay on HUVEC cells revealed a good biocompatibility of PFOB@PLA/GO/Gd-DTPA NCs, showing that the versatile nanocapsule system may hold great potential as an effective nanoplatform for contrast enhanced imaging guided photothermal therapy.

  1. Analysis of ultra-narrow ferromagnetic domain walls

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, Catherine; Paul, David

    2012-01-10

    New materials with high magnetic anisotropy will have domains separated by ultra-narrow ferromagnetic walls with widths on the order of a few unit cells, approaching the limit where the elastic continuum approximation often used in micromagnetic simulations is accurate. The limits of this approximation are explored, and the static and dynamic interactions with intrinsic crystalline defects and external driving elds are modeled. The results developed here will be important when considering the stability of ultra-high-density storage media.

  2. Ultra trace analysis of PAHs by designing simple injection of large amounts of analytes through the sample reconcentration on SPME fiber after magnetic solid phase extraction.

    Science.gov (United States)

    Khodaee, Nader; Mehdinia, Ali; Esfandiarnejad, Reyhaneh; Jabbari, Ali

    2016-01-15

    A simple solventless injection method was introduced based on the using of a solid-phase microextraction (SPME) fiber for injection of large amounts of the analytes extracted by the magnetic solid phase extraction (MSPE) procedure. The resulted extract from MSPE procedure was loaded on a G-coated SPME fiber, and then the fiber was injected into the gas chromatography (GC) injection port. This method combines the advantages of exhaustive extraction property of MSPE and the solvent-less injection of SPME to improve the sensitivity of the analysis. In addition, the analytes were re-concentrated prior to inject into the gas chromatography (GC) inlet because of the organic solvent removing from the remaining extract of MSPE technique. Injection of the large amounts of analytes was made possible by using the introduced procedure. Fourteen polycyclic aromatic hydrocarbons (PAHs) with different volatility were used as model compounds to investigate the method performance for volatile and semi-volatile compounds. The introduced method resulted in the higher enhancement factors (5097-59376), lower detection limits (0.29-3.3pgmL(-1)), and higher sensitivity for the semi-volatile compounds compared with the conventional direct injection method. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Dispersive solid phase microextraction with magnetic graphene oxide as the sorbent for separation and preconcentration of ultra-trace amounts of gold ions.

    Science.gov (United States)

    Kazemi, Elahe; Dadfarnia, Shayessteh; Haji Shabani, Ali Mohammad

    2015-08-15

    A selective, simple and rapid dispersive solid phase microextraction was developed using magnetic graphene oxide (MGO) as an efficient sorbent for the separation and preconcentration of gold ions. The MGO was synthesized by means of the simple one step chemical coprecipitation method, characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Gold ions retained by the sorbent were eluted using 0.5mol L(-)(1) thiourea in 0.1mol L(-1) HCl solution and determined by the flow injection flame atomic absorption spectrometry (FI-FAAS). The factors affecting the separation and preconcentration of gold were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0.02-100.0µg L(-)(1) with a detection limit of 4ng L(-1) and an enrichment factor of 500. The relative standard deviations of 3.2% and 4.7% (n=6) were obtained at 20µg L(-1) level of gold ions for the intra and the inter day analysis, respectively. The method was successfully applied to the determination of gold ions in water and waste water samples as well as a certified reference material (CCU-1b, copper flotation concentrate). Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Magnetic silica nanomaterials for solid-phase extraction combined with dispersive liquid-liquid microextraction of ultra-trace quantities of plasticizers

    International Nuclear Information System (INIS)

    Yamini, Yadollah; Faraji, Mohammad; Adeli, Mahnaz

    2015-01-01

    We are presenting surface modified magnetic silica nanoparticles (m-Si-NPs) for use in solid-phase extraction combined with dispersive liquid-liquid microextraction (DLLME). The m-Si-NPs were surface-functionalized with octadecyl groups to give a material for the extraction of the plasticizers dibutyl phthalate, di(2-ethylhexyl) adipate and di(2-ethylhexyl) phthalate from water samples. The functionalized m-Si-NPs were characterized by scanning electron microscopy, FTIR spectroscopy, thermal gravimetric analysis, and vibrating sample magnetometry. The results showed that the m-Si-NPs were well functionalized with octadecyl groups. The effects of various experimental variables on the extraction efficiencies were investigated. The analytes were quantified by GC/FID. Under optimal conditions, the calibration plots are linear in the range from 0.01 to 100 μg∙L -1 , and very high enrichment factors (mean value ∼20,000) were obtained. As a result of the high enrichment factors, the detection limits are as low as 2–3 ng∙L -1 . The method was successfully employed to the extraction of the plasticizers from (spiked) water samples, and recoveries are in the order of 93.9 to 106.7 %. The method is low cost, fast, and very sensitive (author)

  5. MAGNET

    CERN Multimedia

    Benoit Curé

    The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...

  6. MAGNET

    CERN Multimedia

    B. Curé

    During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...

  7. MMS Observations of Large Guide Field Symmetric Reconnection Between Colliding Reconnection Jets at the Center of a Magnetic Flux Rope at the Magnetopause

    Science.gov (United States)

    Oieroset, M.; Phan, T. D.; Haggerty, C.; Shay, M. A.; Eastwood, J. P.; Gershman, D. J.; Drake, J. F.; Fujimoto, M.; Ergun, R. E.; Mozer, F. S.; hide

    2016-01-01

    We report evidence for reconnection between colliding reconnection jets in a compressed current sheet at the center of a magnetic flux rope at Earth's magnetopause. The reconnection involved nearly symmetric Inflow boundary conditions with a strong guide field of two. The thin (2.5 ion-skin depth (d(sub i) width) current sheet (at approximately 12 d(sub i) downstream of the X line) was well resolved by MMS, which revealed large asymmetries in plasma and field structures in the exhaust. Ion perpendicular heating, electron parallel heating, and density compression occurred on one side of the exhaust, while ion parallel heating and density depression were shifted to the other side. The normal electric field and double out-of-plane (bifurcated) currents spanned almost the entire exhaust. These observations are in good agreement with a kinetic simulation for similar boundary conditions, demonstrating in new detail that the structure of large guide field symmetric reconnection is distinctly different from antiparallel reconnection.

  8. Design and rationale of the MR-INFORM study: stress perfusion cardiovascular magnetic resonance imaging to guide the management of patients with stable coronary artery disease

    Directory of Open Access Journals (Sweden)

    Hussain Shazia T

    2012-09-01

    Full Text Available Abstract Background In patients with stable coronary artery disease (CAD, decisions regarding revascularisation are primarily driven by the severity and extent of coronary luminal stenoses as determined by invasive coronary angiography. More recently, revascularisation decisions based on invasive fractional flow reserve (FFR have shown improved event free survival. Cardiovascular magnetic resonance (CMR perfusion imaging has been shown to be non-inferior to nuclear perfusion imaging in a multi-centre setting and superior in a single centre trial. In addition, it is similar to invasively determined FFR and therefore has the potential to become the non-invasive test of choice to determine need for revascularisation. Trial design The MR-INFORM study is a prospective, multi-centre, randomised controlled non-inferiority, outcome trial. The objective is to compare the efficacy of two investigative strategies for the management of patients with suspected CAD. Patients presenting with stable angina are randomised into two groups: 1 The FFR-INFORMED group has subsequent management decisions guided by coronary angiography and fractional flow reserve measurements. 2 The MR-INFORMED group has decisions guided by stress perfusion CMR. The primary end-point will be the occurrence of major adverse cardiac events (death, myocardial infarction and repeat revascularisation at one year. Clinical trials.gov identifier NCT01236807. Conclusion MR INFORM will assess whether an initial strategy of CMR perfusion is non-inferior to invasive angiography supplemented by FFR measurements to guide the management of patients with stable coronary artery disease. Non-inferiority of CMR perfusion imaging to the current invasive reference standard (FFR would establish CMR perfusion imaging as an attractive non-invasive alternative to current diagnostic pathways.

  9. MAGNETIC VT study: a prospective, multicenter, post-market randomized controlled trial comparing VT ablation outcomes using remote magnetic navigation-guided substrate mapping and ablation versus manual approach in a low LVEF population.

    Science.gov (United States)

    Di Biase, Luigi; Tung, Roderick; Szili-Torok, Tamás; Burkhardt, J David; Weiss, Peter; Tavernier, Rene; Berman, Adam E; Wissner, Erik; Spear, William; Chen, Xu; Neužil, Petr; Skoda, Jan; Lakkireddy, Dhanunjaya; Schwagten, Bruno; Lock, Ken; Natale, Andrea

    2017-04-01

    Patients with ischemic cardiomyopathy (ICM) are prone to scar-related ventricular tachycardia (VT). The success of VT ablation depends on accurate arrhythmogenic substrate localization, followed by optimal delivery of energy provided by constant electrode-tissue contact. Current manual and remote magnetic navigation (RMN)-guided ablation strategies aim to identify a reentry circuit and to target a critical isthmus through activation and entrainment mapping during ongoing tachycardia. The MAGNETIC VT trial will assess if VT ablation using the Niobe™ ES magnetic navigation system results in superior outcomes compared to a manual approach in subjects with ischemic scar VT and low ejection fraction. This is a randomized, single-blind, prospective, multicenter post-market study. A total of 386 subjects (193 per group) will be enrolled and randomized 1:1 between treatment with the Niobe ES system and treatment via a manual procedure at up to 20 sites. The study population will consist of patients with ischemic cardiomyopathy with left ventricular ejection fraction (LVEF) of ≤35% and implantable cardioverter defibrillator (ICD) who have sustained monomorphic VT. The primary study endpoint is freedom from any recurrence of VT through 12 months. The secondary endpoints are acute success; freedom from any VT at 1 year in a large-scar subpopulation; procedure-related major adverse events; and mortality rate through 12-month follow-up. Follow-up will consist of visits at 3, 6, 9, and 12 months, all of which will include ICD interrogation. The MAGNETIC VT trial will help determine whether substrate-based ablation of VT with RMN has clinical advantages over manual catheter manipulation. Clinicaltrials.gov identifier: NCT02637947.

  10. 1.0 T open-configuration magnetic resonance-guided microwave ablation of pig livers in real time

    Science.gov (United States)

    Dong, Jun; Zhang, Liang; Li, Wang; Mao, Siyue; Wang, Yiqi; Wang, Deling; Shen, Lujun; Dong, Annan; Wu, Peihong

    2015-01-01

    The current fastest frame rate of each single image slice in MR-guided ablation is 1.3 seconds, which means delayed imaging for human at an average reaction time: 0.33 seconds. The delayed imaging greatly limits the accuracy of puncture and ablation, and results in puncture injury or incomplete ablation. To overcome delayed imaging and obtain real-time imaging, the study was performed using a 1.0-T whole-body open configuration MR scanner in the livers of 10 Wuzhishan pigs. A respiratory-triggered liver matrix array was explored to guide and monitor microwave ablation in real-time. We successfully performed the entire ablation procedure under MR real-time guidance at 0.202 s, the fastest frame rate for each single image slice. The puncture time ranged from 23 min to 3 min. For the pigs, the mean puncture time was shorted to 4.75 minutes and the mean ablation time was 11.25 minutes at power 70 W. The mean length and widths were 4.62 ± 0.24 cm and 2.64 ± 0.13 cm, respectively. No complications or ablation related deaths during or after ablation were observed. In the current study, MR is able to guide microwave ablation like ultrasound in real-time guidance showing great potential for the treatment of liver tumors. PMID:26315365

  11. Test-retest assessment of cortical activation induced by repetitive transcranial magnetic stimulation with brain atlas-guided optical topography

    Science.gov (United States)

    Tian, Fenghua; Kozel, F. Andrew; Yennu, Amarnath; Croarkin, Paul E.; McClintock, Shawn M.; Mapes, Kimberly S.; Husain, Mustafa M.; Liu, Hanli

    2012-11-01

    Repetitive transcranial magnetic stimulation (rTMS) is a technology that stimulates neurons with rapidly changing magnetic pulses with demonstrated therapeutic applications for various neuropsychiatric disorders. Functional near-infrared spectroscopy (fNIRS) is a suitable tool to assess rTMS-evoked brain responses without interference from the magnetic or electric fields generated by the TMS coil. We have previously reported a channel-wise study of combined rTMS/fNIRS on the motor and prefrontal cortices, showing a robust decrease of oxygenated hemoglobin concentration (Δ[HbO2]) at the sites of 1-Hz rTMS and the contralateral brain regions. However, the reliability of this putative clinical tool is unknown. In this study, we develop a rapid optical topography approach to spatially characterize the rTMS-evoked hemodynamic responses on a standard brain atlas. A hemispherical approximation of the brain is employed to convert the three-dimensional topography on the complex brain surface to a two-dimensional topography in the spherical coordinate system. The test-retest reliability of the combined rTMS/fNIRS is assessed using repeated measurements performed two to three days apart. The results demonstrate that the Δ[HbO2] amplitudes have moderate-to-high reliability at the group level; and the spatial patterns of the topographic images have high reproducibility in size and a moderate degree of overlap at the individual level.

  12. Multifunctional reduction-responsive SPIO and DOX-loaded PEGylated polymeric lipid vesicles for magnetic resonance imaging-guided drug delivery

    International Nuclear Information System (INIS)

    Wang, Sheng; Yang, Weitao; Wang, Hanjie; Chang, Jin; Gong, Xiaoqun; Du, Hongli; Guo, Fangfang; Zhang, Bingbo

    2016-01-01

    Multifunctional superparamagnetic iron-oxide (SPIO)-based nanoparticles have been emerging as candidate nanosystems for cancer diagnosis and therapy. Here, we report the use of reduction- responsive SPIO/doxorubicin (DOX)-loaded poly(ethylene glycol) monomethyl ether (PEG)ylated polymeric lipid vesicles (SPIO and DOX-PPLVs) as a novel theranostic system for tumor magnetic resonance imaging (MRI) diagnosis and controlled drug delivery. These SPIO and DOX-PPLVs are composed of SPIOs that function as MR contrast agents for tumor enhancement and PPLVs as polymer matrices for encapsulating SPIO and antitumor drugs. The in vitro characterizations show that the SPIO and DOX-PPLVs have nanosized structures (∼80 nm), excellent colloidal stability,  good biocompatibility, as well as T _2-weighted MRI capability with a relatively high T _2 relaxivity (r _2 = 213.82 mM"−"1 s"−"1). In vitro drug release studies reveal that the release rate of DOX from the SPIO and DOX-PPLVs is accelerated in the reduction environment. An in vitro cellular uptake study and an antitumor study show that the SPIO and DOX-PPLVs have magnetic targeting properties and effective antitumor activity. In vivo studies show the SPIO and DOX-PPLVs have excellent T _2-weighted tumor targeted MRI capability, image-guided drug delivery capability, and high antitumor effects. These results suggest that the SPIO and DOX-PPLVs are promising nanocarriers for MRI diagnosis and cancer therapy applications. (paper)

  13. National Center for Electron Microscopy users' guide

    International Nuclear Information System (INIS)

    1987-01-01

    The National Center for Electron Microscopy (NCEM) in the Materials and Molecular Research Division of the Lawrence Berkeley Laboratory is a high voltage electron microscope facility for ultra-high resolution or dynamic in-situ studies. This guide describes the instruments and their specifications, support instrumentation, and user policies. Advice as to travel and accommodations is provided in the guide. (FI)

  14. User's guide to program MAD: a computer program for the organization and manipulation of magnetic tape directories

    International Nuclear Information System (INIS)

    Gray, W.H.

    1979-05-01

    MAD is a computer program for the organization and manipulation of the information contained in magnetic tape directories. Program MAD creates, updates, and interrogates a set of four random access files collectively called the MAD unified data base. Although program MAD was originally intended as an information compression mechanism, it has evolved into an organization system with the added feature of an approximately 60% reduction in the space required to store the data. This program is easy to use, relatively fast, efficient in its use of disk space, and available to all users of the Fusion Energy Division DECsystem-10

  15. Magnetic resonance imaging-guided biopsies may improve diagnosis in biopsy-naive men with suspicion of prostate cancer

    DEFF Research Database (Denmark)

    Winther, Mads Dochedahl; Balslev, Ingegerd; Boesen, Lars

    2017-01-01

    INTRODUCTION: The purpose of this pilot study was to investigate whether a short prostate biparametric magnetic resonance imaging (bp-MRI) protocol provides a valuable diagnostic addition for biopsy guidance in biopsy-naive men with a suspicion of prostate cancer (PCa). METHODS: A total of 62...... biopsy-naive patients referred to a systematic transrectal ultrasound biopsy (TRUS-bx) due to suspicion of PCa were prospectively enrolled. Bp-MRI was performed before biopsy. All lesions were scored according to the modified Prostate Imaging Reporting and Data System (PI-RADS) version 2. All patients...

  16. Resonant alteration of propagation in guiding structures with complex Robin parameter and its magnetic-field-induced restoration

    International Nuclear Information System (INIS)

    Olendski, O.

    2011-01-01

    Highlights: → Solutions of the wave equation are analyzed for the confined circular geometry with complex Robin boundary conditions. → Sharp extremum is found in the energy dependence on the imaginary part of the extrapolation length. → Nonzero real part of the Robin length or/and magnetic field wipe out the resonance. - Abstract: Solutions of the scalar Helmholtz wave equation are derived for the analysis of the transport and thermodynamic properties of the two-dimensional disk and three-dimensional infinitely long straight wire in the external uniform longitudinal magnetic field B under the assumption that the Robin boundary condition contains extrapolation length Λ with nonzero imaginary part Λ i . As a result of this complexity, the self-adjointness of the Hamiltonian is lost, its eigenvalues E become complex too and the discrete bound states of the disk characteristic for the real Λ turn into the corresponding quasibound states with their lifetime defined by the eigenenergies imaginary parts E i . Accordingly, the longitudinal flux undergoes an alteration as it flows along the wire with its attenuation/amplification being E i -dependent too. It is shown that, for zero magnetic field, the component E i as a function of the Robin imaginary part exhibits a pronounced sharp extremum with its magnitude being the largest for the zero real part Λ r of the extrapolation length. Increasing magnitude of Λ r quenches the E i - Λ i resonance and at very large Λ r the eigenenergies E approach the asymptotic real values independent of Λ i . The extremum is also wiped out by the magnetic field when, for the large B, the energies tend to the Landau levels. Mathematical and physical interpretations of the obtained results are provided; in particular, it is shown that the finite lifetime of the disk quasibound states stems from the Λ i -induced currents flowing through the sample boundary. Possible experimental tests of the calculated effect are discussed; namely

  17. Osteoid osteoma: Magnetic resonance guided high intensity focused ultrasound for entirely non-invasive treatment. A prospective developmental study

    Science.gov (United States)

    Napoli, A.; de Soccio, V.; Cartocci, G.; Boni, F.; Anzidei, M.; Catalano, C.

    2017-03-01

    To determine the effect of acoustic energy delivered during MR guided Focused Ultrasound (MRgFUS) treatment of symptomatic osteoid osteomas. This prospective, IRB approved study involved 15 consecutive patients (11 m; 4f; mean age, 21) with clinical and imaging diagnosis of Osteoid Osteoma; all patients underwent MRgFUS ablation (ExAblate, InSightec; Discovery 750 MR unit, GE). Lesions located in the vertebral body were excluded, while lesions in proximity to joints or neurovascular bundles were included. Treatment success was determined at clinical and imaging follow-up at 1, 6 and 12 months post-treatment. A visual Analog Pain Score (VAS) was used to assess changes in symptoms. Bone changes at nidus site were evaluated on the basis of CT and dynamic ce-MR imaging (Gd-Bopta; Bracco) pre- and post-treatment. Treatment was carried out using a variable number of sonications (mean 4±1.8) with a mean energy deposition of 866±211 J. There were no treatment- or anesthesia-related complications. A statistically significant (p=0.001) difference was noted between the overall pre- and post-treatment mean VAS scores (8.3±1.6 and 0.6±1.5, respectively). Two treatments were conducted in patients with prior CTgRFA failure and needed two different session for achieving complete clinical successful. At imaging, edema and hyperemia associated with typical osteoid osteoma, gradually disappeared in all lesions. No apparent relationship between nidus vascular extinction and successful outcome was found. Variable reabsorption degree of sclerotic reaction was observed with nidus disappearance in 4 cases (27%). Treatment of osteoid osteoma using MR guided Focused Ultrasound can be performed safely with a high rate of success and without treatment related morbidity; our results indicated also a positive trend to bone rearrangement after treatment.

  18. Magnetic

    Science.gov (United States)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  19. MAGNET

    CERN Multimedia

    Benoit Curé

    The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...

  20. MAGNET

    CERN Document Server

    B. Curé

    The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...

  1. MAGNET

    CERN Multimedia

    Benoit Curé

    2013-01-01

    Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...

  2. Introduction to tractography-guided navigation: using 3-tesla magnetic resonance tractography in surgery for cerebral arteriovenous malformations.

    Science.gov (United States)

    Kikuta, K; Takagi, Y; Nozaki, K; Hashimoto, N

    2008-01-01

    To examine the effectiveness of magnetic resonance (MR) tractography in surgery for cerebral arteriovenous malformations (AVMs). A preoperative evaluation of major neural tracts around the nidus was carried out with 3-tesla (3 T) MR tractography in 25 consecutive patients with cerebral AVMs. The patients were 12 men and 13 women ranging in age from 4 to 60 years of age (mean age: 31.2 +/- 14.1 years). Twelve presented with hemorrhage. Images were obtained with T2-weighted turbo spin echo sequences, axial T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo (MPRAGE) sequences, three-dimensional time-of-flight MR angiography (3D TOF MRA), and thin-section diffusion-tensor imaging (DTI). The AVMs were obliterated in 22 of the 25 patients. A postoperative study of the MR tractography was carried out in 24 patients. In 21 patients, tracts were preserved and no postoperative neurological worsening was observed. Disruption of the tracts was found in 3 patients, and postoperative worsening was observed in 2 patients. However, no deterioration occurred in 1 patient with cerebellar AVM. Notwithstanding the limitations of this method, MR tractography can be considered useful for confirming the integrity of deviated tracts, for localizing deviated tracts, and for evaluating surgical risk, especially in cases of non-hemorrhagic AVM.

  3. Guiding center drift equations

    International Nuclear Information System (INIS)

    Boozer, A.H.

    1979-03-01

    The quations for particle guiding center drift orbits are given in a new magnetic coordinate system. This form of the equations not only separates the fast motion along the lines from the slow motion across, but also requires less information about the magnetic field than many other formulations of the problem

  4. Feasibility of magnetic resonance imaging-guided high intensity focused ultrasound therapy for ablating uterine fibroids in patients with bowel lies anterior to uterus

    International Nuclear Information System (INIS)

    Zhang Lian; Chen Wenzhi; Liu Yinjiang; Hu Xiao; Zhou Kun; Chen Li; Peng Song; Zhu Hui; Zou Huiling; Bai Jin; Wang Zhibiao

    2010-01-01

    Purpose: To prospectively evaluate the feasibility of magnetic resonance (MR) imaging-guided high intensity focused ultrasound (HIFU) therapeutic ablation of uterine fibroids in patients with bowel lies anterior to uterus. Materials and methods: Twenty-one patients with 23 uterine fibroids underwent MR imaging-guided high intensity focused ultrasound treatment, with a mean age of 39.4 ± 6.9 (20-49) years, with fibroids average measuring 6.0 ± 1.6 (range, 2.9-9.5) cm in diameter. After being compressed with a degassed water balloon on abdominal wall, MR imaging-guided high intensity focused ultrasound treatment was performed under conscious sedation by using fentanyl and midazolam. This procedure was performed by a Haifu JM focused ultrasound tumour therapeutic system (JM2.5C, Chongqing Haifu Technology Co., Ltd., China), in combination with a 1.5-Tesla MRI system (Symphony, Siemens, Germany), which provides real-time guidance and control. Contrast-enhanced MR imaging was performed to evaluate the efficacy of thermal ablation immediately and 3 months after HIFU treatment. The treatment time and adverse events were recorded. Results: The mean fibroid volume was 97.0 ± 78.3 (range, 12.7-318.3) cm 3 . According to the treatment plan, an average 75.0 ± 11.4% (range, 37.8-92.4%) of the fibroid volume was treated. The mean fibroid volume immediately after HIFU was 109.7 ± 93.1 (range, 11.9-389.6) cm 3 , slightly enlarged because of edema. The average non-perfused volume was 83.3 ± 71.7 (ra