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Sample records for precession cardiovascular magnetic

  1. Spin Precession in Oblique Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Li, Jing; Huang, Biqin; Appelbaum, Ian

    2009-03-01

    Spin precession and dephasing (``Hanle effect'') provide an unambiguous means to establish the presence of spin transport in semiconductors. We compare theoretical modeling with experimental data from drift-dominated silicon spin-transport devices, illustrating the non-trivial consequences of employing oblique magnetic fields (due to misalignment or intentional, fixed in-plane field components) to measure the effects of spin precession. Model results are also calculated for Hanle measurements under conditions of diffusion-dominated transport, revealing an expected Hanle peak-widening effect induced by the presence of fixed in-plane magnetic bias fields.

  2. Magnetic environment of hydrogen in Fe from muon precession measurements

    NASA Technical Reports Server (NTRS)

    Heiman, N.; Foy, M. L. G.; Kossler, W. J.; Stronach, C. E.

    1974-01-01

    Polarized positive muon radiation was stopped in an ellipsoidal iron target and its precession was observed in a transverse magnetic field. Results indicate that the conduction electron polarization in the 77 K-Fe Curie point region is less than expected, and that the relaxation time of the muon polarization is dominated by the static inhomogeneity to 900 K, at which point magnetization fluctuations become important.

  3. Thermally driven magnetic precession in spin valves

    NASA Astrophysics Data System (ADS)

    Luc, David; Waintal, Xavier

    2014-10-01

    We investigate the angular dependence of the spin torque generated when applying a temperature difference across a spin valve. Our study shows the presence of a nontrivial fixed point in this angular dependence. This fixed point opens the possibility for a temperature gradient to stabilize radio frequency oscillations without the need for an external magnetic field. This so-called "wavy" behavior can already be found upon applying a voltage difference across a spin valve but we find that this effect is much more pronounced with a temperature difference. We find that a spin asymmetry of the Seebeck coefficient of the order of 20 μ VK -1 should be large enough for a temperature gradient of a few degrees to trigger the radio-frequency oscillations. Our semiclassical theory is fully parametrized with experimentally measured(able) parameters and allows one to quantitatively predict the amplitude of the torque.

  4. Electromagnetic torques, precession and evolution of magnetic inclination of pulsars

    NASA Astrophysics Data System (ADS)

    Zanazzi, J. J.; Lai, Dong

    2015-07-01

    We present analytic calculations of the electromagnetic torques acting on a magnetic neutron star rotating in vacuum, including near-zone torques associated with the inertia of dipole and quadrupole magnetic fields. We incorporate these torques into the rotational dynamics of a rigid-body neutron star, and show that the effects of the inertial torque can be understood as a modification of the moment of inertia tensor of the star. We apply our rotational dynamics equation to the Crab pulsar, including intrinsic distortions of the star and various electromagnetic torques, to investigate the possibility that the counter-alignment of the magnetic inclination angle, as suggested by recent observations, could be explained by pulsar precession. We find that if the effective principal axis of the pulsar is nearly aligned with either the magnetic dipole axis or the rotation axis, then precession may account for the observed counter-alignment over decade time-scales. Over the spindown time-scale of the pulsar, the magnetic inclination angle always decreases.

  5. Regular and chaotic precession of magnetization in magnetic films with a stripe domain structure

    NASA Astrophysics Data System (ADS)

    Shutyĭ, A. M.

    2008-12-01

    Based on a numerical solution of the equations of motion found over a wide range of frequencies of an alternating magnetic field, the nonlinear precession dynamics of magnetization are studied in thin-film structures of the (100) type with a stripe domain structure in a perpendicular bias field. The conditions are determined under which high-amplitude regular and chaotic dynamic regimes occur. Bifurcational variations in the precession of coupled magnetic moments and dynamic-bistability states are detected. The specific features of the spectrum of Lyapunov exponents and of time analogs of Poincaré cross sections of trajectories in chaotic regimes are considered.

  6. Regular and chaotic dynamics of magnetization precession in ferrite-garnet films

    NASA Astrophysics Data System (ADS)

    Shutyĭ, Anatoliy M.; Sementsov, Dmitriy I.

    2009-03-01

    By numerically solving equations of motion and constructing the spectrum of Lyapunov exponents, nonlinear dynamics of uniformly precessing magnetization in (110) thin film structures with perpendicular magnetic bias is investigated over a wide frequency range of the alternating field. Bifurcational changes in magnetization precession and the states of dynamical bistability are discovered. Conditions for the realization of high-amplitude regular and chaotic dynamic regimes are revealed. The possibility of controlling those precession regimes by using external magnetic fields is shown. The features of time analogs of the Poincaré section of trajectories in the chaotic regimes are studied.

  7. Magnetization precession of magnetic thin films studied by all optical pump-probe technique

    NASA Astrophysics Data System (ADS)

    Michalski, Steven A.

    The study of magnetization dynamics such as magnetization precession and precessional damping provides insights into the behavior of complex magnetic systems, and indeed may lead to a better understanding of the fundamental limits of magnetic reversal process. In this work, a time-resolved magneto-optic Kerr effect system (TRMOKE) was developed to study magnetization dynamics: Precession and damping. The system uses a femtosecond laser in a pump-probe experiment with direct optical excitation, very similar to the method introduced by Ganping Ju and coworkers. Also, a model based on the Landau-Lifshitz-Gilbert equation (LLG) was developed and used to interpret and analyze the experimental magnetization precession data of a single magnetic layer. The model can be used to predict the precession frequencies with and without damping, the eigenvectors of the magnetization and allows the Gilbert damping parameter (alpha) to be determined. The model is extended to a system of two magnetic layers coupled through a nonmagnetic spacer layer. The capabilities of the TRMOKE system and the LLG models, were demonstrated by studying the magnetization dynamics of Ni/Pt bilayers. Static and dynamic magnetic properties of exchange-coupled magnetic layers have been investigated by magneto-optical measurements. The samples are [Pt/Co] multilayers with perpendicular magnetic anisotropy (PMA) exchange-coupled to a Co layer with in-plane magnetic anisotropy. The exchange is indirect, realized and tuned by an intervening Pt layer of varying thickness. Both the strength and the angle of an external applied magnetic field were varied and for many samples, two modes with two distinct precession frequencies were observed in the precession measurements. The frequencies of both modes depend on the strength and the angle of the applied magnetic field. The LLG model predicts two precessional modes ("acoustic" and "optic") whose behaviors depend on the strength and sign of the exchange coupling

  8. High frequency magnetic properties of ferromagnetic thin films and magnetization dynamics of coherent precession

    NASA Astrophysics Data System (ADS)

    Jiang, Chang-Jun; Fan, Xiao-Long; Xue, De-Sheng

    2015-05-01

    We focus on the ferromagnetic thin films and review progress in understanding the magnetization dynamic of coherent precession, its application in seeking better high frequency magnetic properties for magnetic materials at GHz frequency, as well as new approaches to these materials’ characterization. High frequency magnetic properties of magnetic materials determined by the magnetization dynamics of coherent precession are described by the Landau-Lifshitz-Gilbert equation. However, the complexity of the equation results in a lack of analytically universal information between the high frequency magnetic properties and the magnetization dynamics of coherent precession. Consequently, searching for magnetic materials with higher permeability at higher working frequency is still done case by case. Project supported by the National Basic Research Program of China (Grant No. 2012CB933101), the National Natural Science Foundation of China (Grant Nos. 11034004 and 51371093), the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1251), and the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20130211130003).

  9. Modeling of magnetization precession in spin-torque nano-oscillators with a tilted polarizer

    SciTech Connect

    Lv, Gang; Zhang, Hong E-mail: yaowen@tongji.edu.cn; Cao, Xuecheng; Qin, Yufeng; Li, Guihua; Wang, Linhui; Liu, Yaowen E-mail: yaowen@tongji.edu.cn; Hou, Zhiwei

    2015-07-15

    The spin-torque induced magnetization precession dynamics are studied in a spin-valve with a tilted spin polarizer. Macrospin simulations demonstrate that the frequency of precession state depends both on the external DC current and the intrinsic parameters of devices such as the tilted angle of spin polarizer, the damping factor and saturation magnetization of the free layer. The dependence role of those parameters is characterized by phase diagrams. An analytical model is presented, which can successfully interpret the features of precession frequency.

  10. Magnetization switching by microwaves initially rotating in opposite direction to precession

    NASA Astrophysics Data System (ADS)

    Taniguchi, Tomohiro

    2015-12-01

    A common understanding of magnetization switching in microwave-assisted magnetization reversal is that the rotation direction of the microwaves should be the same as the precession direction of the magnetization. In this letter, however, we show that microwaves initially rotating opposite to the magnetization precession destabilize the magnetization at an equilibrium and induce switching more efficiently when the microwave frequency depends on time. This argument is analytically deduced from an energy balance equation. We also establish a model satisfying this condition and confirm magnetization switching solely by microwaves by using numerical simulation.

  11. Coherent control of magnetization precession in electrically detected time domain ferromagnetic resonance

    SciTech Connect

    Wid, O.; Wahler, M.; Homonnay, N.; Richter, T.; Schmidt, G.

    2015-11-15

    We demonstrate coherent control of time domain ferromagnetic resonance by all electrical excitation and detection. Using two ultrashort magnetic field steps with variable time delay we control the induction decay in yttrium iron garnet (YIG). By setting suitable delay times between the two steps the precession of the magnetization can either be enhanced or completely stopped. The method allows for a determination of the precession frequency within a few precession periods and with an accuracy much higher than can be achieved using fast fourier transformation. Moreover it holds the promise to massively increase precession amplitudes in pulsed inductive microwave magnetometry (PIMM) using low amplitude finite pulse trains. Our experiments are supported by micromagnetic simulations which nicely confirm the experimental results.

  12. Rotational properties of ferromagnetic nanoparticles driven by a precessing magnetic field in a viscous fluid.

    PubMed

    Lyutyy, T V; Denisov, S I; Reva, V V; Bystrik, Yu S

    2015-10-01

    We study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations. PMID:26565245

  13. Rotational properties of ferromagnetic nanoparticles driven by a precessing magnetic field in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Lyutyy, T. V.; Denisov, S. I.; Reva, V. V.; Bystrik, Yu. S.

    2015-10-01

    We study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations.

  14. Origin of light-induced precession of magnetization in ferromagnetic (Ga,Mn)As

    NASA Astrophysics Data System (ADS)

    Rozkotova, Eva; Nemec, Petr; Sprinzl, Daniel; Tesarova, Nada; Maly, Petr; Novak, Vit; Olejnik, Kamil; Zemen, Jan; Cukr, Miroslav; Jungwirth, Tomas; Wunderlich, Joerg

    2009-03-01

    The impact of femtosecond laser pulse leads to the precession of magnetization in (Ga,Mn)As, which can be detected by the time- resolved Kerr rotation (KR) technique. Even though this phenomenon is known for several years [1], the exact physical mechanism inducing the precession is still not clear [2,3]. We show, by a detailed comparison of the KR experimental results and the microscopic calculations of the magnetic anisotropy, that the precession is a consequence of the anisotropy field modification due to the laser pulse-induced change of hole concentration and lattice temperature. [1] A. Oiwa, H. Takechi, H. Munekata, J. Supercond. 18, 9 (2005).[2] Y. Hashimoto, S. Kobayashi, H. Munekata, PRL 100, 067202 (2008).[3] E. Rozkotova, P. Nemec, P. Horodyska, D. Sprinzl, F. Trojanek, P. Maly, V. Novak, K. Olejnik, M. Cukr, T. Jungwirth, Appl. Phys. Lett 92, 122507 (2008).

  15. Magnetic field angle dependence of out-of-plane precession in spin torque oscillators having an in-plane magnetized free layer and a perpendicularly magnetized reference layer

    NASA Astrophysics Data System (ADS)

    Hiramatsu, Ryo; Kubota, Hitoshi; Tsunegi, Sumito; Tamaru, Shingo; Yakushiji, Kay; Fukushima, Akio; Matsumoto, Rie; Imamura, Hiroshi; Yuasa, Shinji

    2016-05-01

    Out-of-plane (OP) precession in spin torque oscillators having an in-plane (IP) magnetized free layer and a perpendicularly magnetized reference layer was studied. The bias voltage (V B) and magnetic field angle (θ) dependence of the OP precession were investigated. The absolute values of the critical magnetic fields (H\\text{B}\\text{c - } and H\\text{B}\\text{c + }) between which OP precession is excited increased as V B increased and as θ changed from the IP to the OP direction. The IP components of H\\text{B}\\text{c +/- } converged to a constant value regardless of θ. This result indicates that excitation of OP precession is suppressed entirely by the IP component of the magnetic field, and the contribution of the OP component can be ignored. The experimentally observed precession behavior was successfully modeled by macrospin simulations.

  16. Cardiovascular magnetic resonance artefacts

    PubMed Central

    2013-01-01

    The multitude of applications offered by CMR make it an increasing popular modality to study the heart and the surrounding vessels. Nevertheless the anatomical complexity of the chest, together with cardiac and respiratory motion, and the fast flowing blood, present many challenges which can possibly translate into imaging artefacts. The literature is wide in terms of papers describing specific MR artefacts in great technical detail. In this review we attempt to summarise, in a language accessible to a clinical readership, some of the most common artefacts found in CMR applications. It begins with an introduction of the most common pulse sequences, and imaging techniques, followed by a brief section on typical cardiovascular applications. This leads to the main section on common CMR artefacts with examples, a short description of the mechanisms behind them, and possible solutions. PMID:23697969

  17. Electromagnetic fields of a nonprecessing and precessing, spinning, permanent magnet, conducting sphere

    NASA Astrophysics Data System (ADS)

    Mueller, R. S.

    1991-02-01

    The electromagnetic fields inside and outside a steadily rotating, magnetized, conducting sphere are determined for the cases of nonprecession and precession. In both cases the spin rotational axis is aligned with the magnetic axis of the sphere. The field expressions are those measured in the laboratory reference frame. For a nonprecessing sphere the magnetic fields are identical to the fields of a stationary sphere, but in addition there is an induced induction of order v-squared/c-squared whose lines of force radiate in loops above and below the equator. The electric and magnetic induction field expressions were derived into static and dynamic parts. The amplitudes of these parts were plotted as functions of the angle of inclination of the polar axis. The dynamic parts are circularly and elliptically polarized. The pivot point of the precessing sphere was chosen off center. The only two stable positions are at theta = 0 deg and 180 deg for a center pivot.

  18. Resonantly excited precession motion of three-dimensional vortex core in magnetic nanospheres [corrected].

    PubMed

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D

    2015-01-01

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ〈mΓ〉 is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component 〈mΓ〉 of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for 〈mΓ〉 yields a simple explicit form of 〈mΓ〉 ≈ (73.6 ± 3.4)(lex/2R)(2.20±0.14), where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging. PMID:26079895

  19. Resonantly exited precession motion of three-dimensional vortex core in magnetic nanospheres

    PubMed Central

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P.; Sheka, Denis D.

    2015-01-01

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ〈mΓ〉 is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component 〈mΓ〉 of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for 〈mΓ〉 yields a simple explicit form of 〈mΓ〉 ≈ (73.6 ± 3.4)(lex/2R)2.20±0.14, where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging. PMID:26079895

  20. Resonantly exited precession motion of three-dimensional vortex core in magnetic nanospheres

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P.; Sheka, Denis D.

    2015-06-01

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for yields a simple explicit form of  ≈ (73.6 ± 3.4)(lex/2R)2.20±0.14, where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging.

  1. Precession of Uranus and Neptune and their magnetic field

    NASA Technical Reports Server (NTRS)

    Dolginov, Sh. SH.

    1993-01-01

    The strength of the dipole magnetic field of a planet, H(sub p), can be estimated relative to that of the Earth at the epoch of the observation. The generation of magnetic fields in Uranus and Neptune occurs at very different depths for different values of sigma. This assertion is confirmed by the estimation of the Reynolds number (R(sub m)) and agrees with the difference of the contributions of the Joule heat losses into the observed heat fluxes of Uranus and Neptune.

  2. Practical applications of cardiovascular magnetic resonance

    PubMed Central

    Alpendurada, F; Wong, J; Pennell, D J

    2009-01-01

    Recent developments in magnetic resonance imaging have focused attention on evaluation of patients with cardiac disease. These improvements have been substantiated by a large and expanding body of clinical evidence, making cardiovascular magnetic resonance the imaging modality of choice in a wide variety of cardiovascular disorders. A brief review on the current applications of cardiovascular magnetic resonance is provided, with reference to some of the most relevant studies, statements and reviews published in this field.

  3. Parametric Harmonic Generation as a Probe of Unconstrained Spin Magnetization Precession in the Shallow Barrier Limit.

    PubMed

    Capua, Amir; Rettner, Charles; Parkin, Stuart S P

    2016-01-29

    We study the parametric excitation of high orders of magnetization precession in ultrathin films having perpendicular magnetic anisotropy. We observe that for a given driving field amplitude the harmonic generation can be increased by lowering the barrier with the application of an in-plane magnetic field in the manner of the Smit-Beljers effect. In this effect, the magnetic stiffness is reduced not by lowering the magnitude of the magnetic field upon which the spins precess, but rather by effectively releasing the field's "anchoring" point. This results in a shallow energy barrier where the electrons' spin is locally unconstrained. While the observation is unveiled in the form of nonlinear high harmonic generation, we believe that the physics whereby the barrier is suppressed by an external magnetic field may apply to other phenomena associated with ultrathin films. In these cases, such unconstrained motion may serve as a sensitive probe of the torques associated with proximate spin currents. Moreover, our approach may be used as a model system for the study of phase transitions in the field of nonlinear dynamics. PMID:26871356

  4. X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components

    PubMed Central

    Goulon, Jośe; Rogalev, Andrei; Goujon, Gérard; Wilhelm, Fabrice; Ben Youssef, Jamal; Gros, Claude; Barbe, Jean-Michel; Guilard, Roger

    2011-01-01

    X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR spectra simultaneously recorded on ferrimagnetically ordered iron garnets. With pumping capabilities extended up to sub-THz frequencies, high-field XDMR should allow us to probe the precession of orbital magnetization components in paramagnetic organometallic complexes with large zero-field splitting. Even more challenging, we suggest that XDMR spectra might be recorded on selected antiferromagnetic crystals for which orbital magnetism is most often ignored in the absence of any supporting experimental evidence. PMID:22272105

  5. Topological currents in neutron stars: kicks, precession, toroidal fields, and magnetic helicity

    SciTech Connect

    Charbonneau, James; Zhitnitsky, Ariel E-mail: arz@phas.ubc.ca

    2010-08-01

    The effects of anomalies in high density QCD are striking. We consider a direct application of one of these effects, namely topological currents, on the physics of neutron stars. All the elements required for topological currents are present in neutron stars: degenerate matter, large magnetic fields, and parity violating processes. These conditions lead to the creation of vector currents capable of carrying momentum and inducing magnetic fields. We estimate the size of these currents for many representative states of dense matter in the neutron star and argue that they could be responsible for the large proper motion of neutron stars (kicks), the toroidal magnetic field and finite magnetic helicity needed for stability of the poloidal field, and the resolution of the conflict between type-II superconductivity and precession. Though these observational effects appear unrelated, they likely originate from the same physics — they are all P-odd phenomena that stem from a topological current generated by parity violation.

  6. Cardiovascular magnetic resonance in systemic hypertension

    PubMed Central

    2012-01-01

    Systemic hypertension is a highly prevalent potentially modifiable cardiovascular risk factor. Imaging plays an important role in the diagnosis of underlying causes for hypertension, in assessing cardiovascular complications of hypertension, and in understanding the pathophysiology of the disease process. Cardiovascular magnetic resonance (CMR) provides accurate and reproducible measures of ventricular volumes, mass, function and haemodynamics as well as uniquely allowing tissue characterization of diffuse and focal fibrosis. In addition, CMR is well suited for exclusion of common secondary causes for hypertension. We review the current and emerging clinical and research applications of CMR in hypertension. PMID:22559053

  7. Precession Control on Precipitation in the Western Pacific Warm Pool Inferred from Environmental Magnetism

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.

    2014-12-01

    The Western Pacific Warm Pool (WPWP) has highest water temperature in the global ocean, and its spatiotemporal variations have significant impacts on large-scale atmospheric circulation and global hydrology. An environmental magnetic study was conducted on sediment cores of late Pleistocene age taken from the West Caroline Basin (WCB) offshore northern New Guinea in order to constrain hydrological variability over the WPWP on orbital timescales. Magnetite dominates magnetic mineral assemblages of the sediments. This is evidenced by that IRM acquisition curves are mostly explained by a low-coercivity component, and that the Verwey transition was obvious in low-temperature measurements. Existence of the sharp central ridges on FORC diagrams and TEM images indicate the occurrence of biogenic magnetite. Compared with pelagic sediments from other regions, however, FORC diagrams show a larger contribution of an interacting PSD and MD component, and the ratios of ARM susceptibility to SIRM (kARM/SIRM) are lower, which suggests a larger proportion of the terrigenous component. This is probably due to a large terrigenous sediment input from nearby land, New Guinea, induced by high precipitation in the intertropical convergence zone. Magnetic susceptibility (k) and kARM/SIRM well correlate with northern-hemisphere summer insolation. Maxima in k and minima in kARM/SIRM correspond to insolation minima, which suggests a larger terrigenous input caused by higher precipitation at these times. Interestingly, in the western part of WCB, k variations are dominated by the eccentricity periodicity and mimic δ18O curves, but the precession periodicity prevails in kARM/SIRM. These cores were taken at depths close to the CCD, and thus the k variations cannot be explained by dilution with carbonates. Sedimentation influenced by global sea-level changes may control the k variations; this part of the basin is adjacent to a wider continental shelf compared with the eastern part of WCB.

  8. Spin precession of slow neutrons in Einstein-Cartan gravity with torsion, chameleon, and magnetic field

    NASA Astrophysics Data System (ADS)

    Ivanov, A. N.; Wellenzohn, M.

    2016-02-01

    We analyze a spin precession of slow neutrons in the Einstein-Cartan gravity with torsion, chameleon and magnetic field. For the derivation of the Heisenberg equation of motion of the neutron spin we use the effective low-energy potential, derived by Ivanov and Wellenzohn [Phys. Rev. D 92, 125004 (2015)] for slow neutrons, coupled to gravitational, chameleon, and torsion fields to order 1 /m , where m is the neutron mass. In addition to these low-energy interactions we switch on the interaction of slow neutrons with a magnetic field. We show that to linear order approximation with respect to gravitational, chameleon, and torsion fields the Dirac Hamilton operator for fermions (neutrons), moving in spacetimes created by rotating coordinate systems, contains the anti-Hermitian operators of torsion-fermion (neutron) interactions, caused by torsion scalar and tensor space-space-time and time-space-space degrees of freedom. Such anti-Hermitian operators violate C P and T invariance. In the low-energy approximation the C P and T violating torsion-fermion (neutron) interactions appear only to order O (1 /m ). One may assume that in the rotating Universe and galaxies the obtained anti-Hermitian torsion-fermion interactions might be an origin of (i) violation of C P and T invariance in the Universe and (ii) of baryon asymmetry. We show that anti-Hermitian torsion-fermion interactions of relativistic fermions, violating C P and T invariance, (i) cannot be removed by nonunitary transformations of the Dirac fermion wave functions and (ii) are conformal invariant. According to general requirements of conformal invariance of massive particle theories in gravitational fields [see R. H. Dicke, Phys. Rev. 125, 2163 (1962) and A. J. Silenko, Phys. Rev. D 91, 065012 (2015)], conformal invariance of anti-Hermitian torsion-fermion interactions is valid only if the fermion mass is changed by a conformal factor.

  9. Precessing Ferromagnetic Needle Magnetometer.

    PubMed

    Jackson Kimball, Derek F; Sushkov, Alexander O; Budker, Dmitry

    2016-05-13

    A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency Ω under conditions where its intrinsic spin dominates over its rotational angular momentum, Nℏ≫IΩ (I is the moment of inertia of the needle about the precession axis and N is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin Nℏ maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of N spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum uncertainty, the sensitivity of a precessing needle magnetometer can far surpass that of magnetometers based on spin precession of atoms in the gas phase. Under conditions where noise from coupling to the environment is subdominant, the scaling with measurement time t of the quantum- and detection-limited magnetometric sensitivity is t^{-3/2}. The phenomenon of ferromagnetic needle precession may be of particular interest for precision measurements testing fundamental physics. PMID:27232012

  10. Precessing Ferromagnetic Needle Magnetometer

    NASA Astrophysics Data System (ADS)

    Jackson Kimball, Derek F.; Sushkov, Alexander O.; Budker, Dmitry

    2016-05-01

    A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency Ω under conditions where its intrinsic spin dominates over its rotational angular momentum, N ℏ≫I Ω (I is the moment of inertia of the needle about the precession axis and N is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin N ℏ maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of N spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum uncertainty, the sensitivity of a precessing needle magnetometer can far surpass that of magnetometers based on spin precession of atoms in the gas phase. Under conditions where noise from coupling to the environment is subdominant, the scaling with measurement time t of the quantum- and detection-limited magnetometric sensitivity is t-3 /2. The phenomenon of ferromagnetic needle precession may be of particular interest for precision measurements testing fundamental physics.

  11. Possible evidence for free precession of a strongly magnetized neutron star in the magnetar 4U 0142+61.

    PubMed

    Makishima, K; Enoto, T; Hiraga, J S; Nakano, T; Nakazawa, K; Sakurai, S; Sasano, M; Murakami, H

    2014-05-01

    Magnetars are a special type of neutron stars, considered to have extreme dipole magnetic fields reaching ∼ 10(11) T. The magnetar 4 U 0142+61, one of the prototypes of this class, was studied in broadband x rays (0.5-70 keV) with the Suzaku observatory. In hard x rays (15-40 keV), its 8.69 sec pulsations suffered slow phase modulations by ± 0.7 sec, with a period of ∼ 15 h. When this effect is interpreted as free precession of the neutron star, the object is inferred to deviate from spherical symmetry by ∼ 1.6 × 10(-4) in its moments of inertia. This deformation, when ascribed to magnetic pressure, suggests a strong toroidal magnetic field, ∼ 10(12) T, residing inside the object. This provides one of the first observational approaches towards toroidal magnetic fields of magnetars. PMID:24836230

  12. Tools for cardiovascular magnetic resonance imaging

    PubMed Central

    Krishnamurthy, Ramkumar; Cheong, Benjamin

    2014-01-01

    In less than fifteen years, as a non-invasive imaging option, cardiovascular MR has grown from a being a mere curiosity to becoming a widely used clinical tool for evaluating cardiovascular disease. Cardiovascular magnetic resonance imaging (CMRI) is now routinely used to study myocardial structure, cardiac function, macro vascular blood flow, myocardial perfusion, and myocardial viability. For someone entering the field of cardiac MR, this rapid pace of development in the field of CMRI might make it difficult to identify a cohesive starting point. In this brief review, we have attempted to summarize the key cardiovascular imaging techniques that have found widespread clinical acceptance. In particular, we describe the essential cardiac and respiratory gating techniques that form the backbone of all cardiovascular imaging methods. It is followed by four sections that discuss: (I) the gradient echo techniques that are used to assess ventricular function; (II) black-blood turbo spin echo (SE) methods used for morphologic assessment of the heart; (III) phase-contrast based techniques for the assessment of blood flow; and (IV) CMR methods for the assessment of myocardial ischemia and viability. In each section, we briefly summarize technical considerations relevant to the clinical use of these techniques, followed by practical information for its clinical implementation. In each of those four areas, CMRI is considered either as the benchmark imaging modality against which the diagnostic performance of other imaging modalities are compared against, or provides a complementary capability to existing imaging techniques. We have deliberately avoided including cutting-edge CMR imaging techniques practiced at few academic centers, and restricted our discussion to methods that are widely used and are likely to be available in a clinical setting. Our hope is that this review would propel an interested reader toward more comprehensive reviews in the literature. PMID:24834409

  13. Spin-to-charge conversion in lateral and vertical topological-insulator/ferromagnet heterostructures with microwave-driven precessing magnetization

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad; Nagaosa, Naoto; Nikolić, Branislav K.

    2014-09-01

    Using the charge-conserving Floquet-Green function approach to open quantum systems driven by an external time-periodic potential, we analyze how spin current pumped by the precessing magnetization of a ferromagnetic (F) layer is injected laterally into the interface with strong spin-orbit coupling (SOC) and converted into charge current flowing in the same direction. In the case of a metallic interface with the Rashba SOC used in recent experiments [J. C. R. Sánchez, L. Vila, G. Desfonds, S. Gambarelli, J. P. Attané, J. M. De Teresa, C. Magén, and A. Fert, Nat. Commun. 4, 2944 (2013), 10.1038/ncomms3944], both spin ISα and charge I current flow within the interface where I /ISα≃ 2-8% (depending on the precession cone angle), while for a F/topological-insulator (F/TI) interface employed in related experiments [Y. Shiomi, K. Nomura, Y. Kajiwara, K. Eto, M. Novak, K. Segawa, Y. Ando, and E. Saitoh, arXiv:1312.7091] the conversion efficiency is greatly enhanced (I /ISα≃ 40-60%) due to perfect spin-momentum locking on the surface of a TI. The spin-to-charge conversion occurs also when spin current is pumped vertically through the F/TI interface with smaller efficiency (I /ISα˜0.001%), but with the charge current signal being sensitive to whether the Dirac fermions at the interface are massive or massless.

  14. Cardiovascular magnetic resonance physics for clinicians: part I.

    PubMed

    Ridgway, John P

    2010-01-01

    There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject

  15. Cardiovascular magnetic resonance physics for clinicians: part I

    PubMed Central

    2010-01-01

    There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject

  16. Simplifying cardiovascular magnetic resonance pulse sequence terminology.

    PubMed

    Friedrich, Matthias G; Bucciarelli-Ducci, Chiara; White, James A; Plein, Sven; Moon, James C; Almeida, Ana G; Kramer, Christopher M; Neubauer, Stefan; Pennell, Dudley J; Petersen, Steffen E; Kwong, Raymond Y; Ferrari, Victor A; Schulz-Menger, Jeanette; Sakuma, Hajime; Schelbert, Erik B; Larose, Éric; Eitel, Ingo; Carbone, Iacopo; Taylor, Andrew J; Young, Alistair; de Roos, Albert; Nagel, Eike

    2014-01-01

    We propose a set of simplified terms to describe applied Cardiovascular Magnetic Resonance (CMR) pulse sequence techniques in clinical reports, scientific articles and societal guidelines or recommendations. Rather than using various technical details in clinical reports, the description of the technical approach should be based on the purpose of the pulse sequence. In scientific papers or other technical work, this should be followed by a more detailed description of the pulse sequence and settings. The use of a unified set of widely understood terms would facilitate the communication between referring physicians and CMR readers by increasing the clarity of CMR reports and thus improve overall patient care. Applied in research articles, its use would facilitate non-expert readers' understanding of the methodology used and its clinical meaning. PMID:25551695

  17. Effect of zero magnetic field on cardiovascular system and microcirculation

    NASA Astrophysics Data System (ADS)

    Gurfinkel, Yu. I.; At'kov, O. Yu.; Vasin, A. L.; Breus, T. K.; Sasonko, M. L.; Pishchalnikov, R. Yu.

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling "ARFA" has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions.

  18. Effect of zero magnetic field on cardiovascular system and microcirculation.

    PubMed

    Gurfinkel, Yu I; At'kov, O Yu; Vasin, A L; Breus, T K; Sasonko, M L; Pishchalnikov, R Yu

    2016-02-01

    The effects of zero magnetic field conditions on cardiovascular system of healthy adults have been studied. In order to generate zero magnetic field, the facility for magnetic fields modeling "ARFA" has been used. Parameters of the capillary blood flow, blood pressure, and the electrocardiogram (ECG) monitoring were measured during the study. All subjects were tested twice: in zero magnetic field and, for comparison, in sham condition. The obtained results during 60 minutes of zero magnetic field exposure demonstrate a clear effect on cardiovascular system and microcirculation. The results of our experiments can be used in studies of long-term stay in hypo-magnetic conditions during interplanetary missions. PMID:26948007

  19. Realizations of magnetic-monopole gauge fields - Diatoms and spin precession

    NASA Technical Reports Server (NTRS)

    Moody, J.; Shapere, A.; Wilczek, F.

    1986-01-01

    It is found that the effective Hamiltonian for nuclear rotation in a diatom is equivalent to that of a charged particle in a background magnetic-monopole field. In certain cases, half-integer orbital angular momentum or non-Abelian fields occur. Furthermore, the effects of magnetic-monopole-like gauge fields can be experimentally observed in spin-resonance experiments with variable magnetic fields.

  20. Cardiovascular Magnetic Resonance Myocardial Feature Tracking: Concepts and Clinical Applications.

    PubMed

    Schuster, Andreas; Hor, Kan N; Kowallick, Johannes T; Beerbaum, Philipp; Kutty, Shelby

    2016-04-01

    Heart failure-induced cardiovascular morbidity and mortality constitute a major health problem worldwide and result from diverse pathogeneses, including coronary artery disease, nonischemic cardiomyopathies, and arrhythmias. Assessment of cardiovascular performance is important for early diagnosis and accurate management of patients at risk of heart failure. During the past decade, cardiovascular magnetic resonance myocardial feature tracking has emerged as a useful tool for the quantitative evaluation of cardiovascular function. The method allows quantification of biatrial and biventricular mechanics from measures of deformation: strain, torsion, and dyssynchrony. The purpose of this article is to review the basic principles, clinical applications, accuracy, and reproducibility of cardiovascular magnetic resonance myocardial feature tracking, highlighting the prognostic implications. It will also provide an outlook on how this field might evolve in the future. PMID:27009468

  1. Mechanism of photoexcited precession of magnetization in (Ga,Mn)As on the basis of time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsuda, T.; Munekata, H.

    2016-02-01

    In order to investigate the mechanism of photoexcited precession of magnetization in ferromagnetic G a1 -xM nxAs , magneto-optical (MO) and differential reflectivity (Δ R /R ; DR) temporal profiles are studied at relatively long (picosecond to nanosecond) and ultrashort (1 ps or less) time scales for samples with different Mn content (x =0.01 -0.11 ) . As to the oscillatory MO profiles observed in the long time scale, simulation based on the Landau-Lifshitz-Gilbert equation combined with two different MO effects confirms photoinducement of the perpendicular anisotropy component Δ Heff ,⊥ . As for the profiles observed in the ultrashort time scale, they are consistently explained in terms of the dynamics of photogenerated carriers, but not by the sudden reduction in magnetization (the ultrafast demagnetization). In light of these experimental results and analyses, a mechanism that accounts for the photoinduced Δ Heff ,⊥ is addressed: namely, photoionizationlike excitation of M n2 + , M n2 ++h ν →M n2 +,*=M n3++e- . That such excitation tips magnetic anisotropy toward the out-of-plane direction through the inducement of orbital angular momentum and the gradient ∂ (M n2 +,* )/∂ z is discussed. The validity of the proposed mechanism is examined by estimating the efficiency of excitation on the basis of the Lambert-Beer law and the experimental Δ Heff ,⊥ values, through which an efficiency of 1-10 ppm with a nominal optical cross section of around 5 ×10-12m2 is obtained.

  2. Interventional cardiovascular magnetic resonance: still tantalizing

    PubMed Central

    Ratnayaka, Kanishka; Faranesh, Anthony Z; Guttman, Michael A; Kocaturk, Ozgur; Saikus, Christina E; Lederman, Robert J

    2008-01-01

    The often touted advantages of MR guidance remain largely unrealized for cardiovascular interventional procedures in patients. Many procedures have been simulated in animal models. We argue these opportunities for clinical interventional MR will be met in the near future. This paper reviews technical and clinical considerations and offers advice on how to implement a clinical-grade interventional cardiovascular MR (iCMR) laboratory. We caution that this reflects our personal view of the "state of the art." PMID:19114017

  3. Molecular Cardiovascular Magnetic Resonance: Current Status and Future Prospects.

    PubMed

    Bender, Yvonne Y; Pfeifer, Andreas; Ebersberger, Hans U; Diederichs, Gerd; Hoppe, Peter; Hamm, Bernd; Botnar, René M; Makowski, Marcus R

    2016-05-01

    In the Western world and developing countries, the number one causes of mortality and morbidity result from cardiovascular diseases. Cardiovascular diseases represent a wide range of pathologies, including myocardial infarction, peripheral vascular disease, and cerebrovascular disease, which are all linked by a common cause - atherosclerosis. Currently, the diagnosis of atherosclerosis is in most cases established at the end stage of the disease, when patients are administered to the emergency room due to a myocardial infarction or stroke. Even though cardiovascular diseases have an enormous impact on society, there are still limitations in the early diagnosis and the prevention of the disease. Current imaging methods mainly focus on morphological changes that occur at an advanced disease stage, e.g., degree of stenosis. Cardiovascular magnetic resonance imaging and specifically molecular cardiovascular magnetic resonance imaging are capable to reveal pathophysiological changes already occurring during early atherosclerotic plaque formation. This allows for the assessment of cardiovascular disease on a level, which goes beyond morphological or anatomical criteria. In this review, we will introduce promising MR-based molecular imaging strategies for the non-invasive assessment of cardiovascular disease. PMID:27038612

  4. The Conformal Steady-State Free Precession:. a Kepplerian Approach to Automorphic Scattering Theory of Orbiton/spinon Dynamics

    NASA Astrophysics Data System (ADS)

    Schempp, Walter J.

    2013-09-01

    Based on projective geometry, a quantum holographic approach to the orbiton / spinon dynamics of quantum blackholography and clinical magnetic resonance tomography is mathematically described. Crucial applications of the conformal steady-state free-precession modality and automorphic scattering theory are the evidence for a supermassive central black hole in the Milky Way galaxy and the modalities of clinical cardiovascular magnetic resonance tomography and diffusion weighted magnetic resonance tomography of non-invasive radiological diagnostics.

  5. Cardiovascular outcome associations among cardiovascular magnetic resonance measures of arterial stiffness: the Dallas heart study

    PubMed Central

    2014-01-01

    Background Cardiovascular magnetic resonance (CMR) has been validated for the noninvasive assessment of total arterial compliance and aortic stiffness, but their associations with cardiovascular outcomes is unknown. The purpose of this study was to evaluate associations of CMR measures of total arterial compliance and two CMR measures of aortic stiffness with respect to future cardiovascular events. Methods The study consisted of 2122 Dallas Heart Study participants without cardiovascular disease who underwent CMR at 1.5 Tesla. Aortic stiffness was measured by CMR-derived ascending aortic distensibility and aortic arch pulse wave velocity. Total arterial compliance was calculated by dividing left ventricular stroke volume by pulse pressure. Participants were monitored for cardiovascular death, non-fatal cardiac events, and non-fatal extra-cardiac vascular events over 7.8 ± 1.5 years. Cox proportional hazards regression was used to assess for associations between CMR measures and cardiovascular events. Results Age, systolic blood pressure, and resting heart rate were independently associated with changes in ascending aortic distensibility, arch pulse wave velocity, and total arterial compliance (all p < .0001). A total of 153 participants (6.9%) experienced a cardiovascular event. After adjusting for traditional risk factors, total arterial compliance was modestly associated with increased risk for composite events (HR 1.07 per 1SD, p = 0.03) while the association between ascending aortic distensibility and composite events trended towards significance (HR 1.18 per 1SD, p = 0.08). Total arterial compliance and aortic distensibility were independently associated with nonfatal cardiac events (HR 1.11 per 1SD, p = 0.001 and HR 1.45 per 1SD, p = 0.0005, respectively), but not with cardiovascular death or nonfatal extra-cardiac vascular events. Arch pulse wave velocity was independently associated with nonfatal extra-cardiac vascular events (HR

  6. Harnessing spin precession with dissipation

    NASA Astrophysics Data System (ADS)

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors.

  7. Harnessing spin precession with dissipation

    PubMed Central

    Crisan, A. D.; Datta, S.; Viennot, J. J.; Delbecq, M. R.; Cottet, A.; Kontos, T.

    2016-01-01

    Non-collinear spin transport is at the heart of spin or magnetization control in spintronics devices. The use of nanoscale conductors exhibiting quantum effects in transport could provide new paths for that purpose. Here we study non-collinear spin transport in a quantum dot. We use a device made out of a single-wall carbon nanotube connected to orthogonal ferromagnetic electrodes. In the spin transport signals, we observe signatures of out of equilibrium spin precession that are electrically tunable through dissipation. This could provide a new path to harness spin precession in nanoscale conductors. PMID:26816050

  8. High field magnetic resonance imaging of rodents in cardiovascular research.

    PubMed

    Vanhoutte, Laetitia; Gerber, Bernhard L; Gallez, Bernard; Po, Chrystelle; Magat, Julie; Jean-Luc, Balligand; Feron, Olivier; Moniotte, Stéphane

    2016-07-01

    Transgenic and gene knockout rodent models are primordial to study pathophysiological processes in cardiovascular research. Over time, cardiac MRI has become a gold standard for in vivo evaluation of such models. Technical advances have led to the development of magnets with increasingly high field strength, allowing specific investigation of cardiac anatomy, global and regional function, viability, perfusion or vascular parameters. The aim of this report is to provide a review of the various sequences and techniques available to image mice on 7-11.7 T magnets and relevant to the clinical setting in humans. Specific technical aspects due to the rise of the magnetic field are also discussed. PMID:27287250

  9. Contrast media in cardiovascular magnetic resonance.

    PubMed

    Lombardi, Massimo; Aquaro, Giovanni; Favilli, Brunella

    2005-01-01

    Among the available imaging techniques, Magnetic Resonance Imaging (MRI) is gaining an increasing role in the cardiologic setting because its specific properties such as the use of non ionising energies, the natural strong contrast between different tissues, the absence of spatial limitations, the good spatial and temporal resolution, the reduced operator dependency. To further improve the images quality and the histopathologic characterisation of tissues the use of contrast media (molecules containing gadolinium, manganese, iron, dysprosium ions) has been proposed both in the experimental and in the clinical settings. Among these ions gadolinium, which having 7 odd electrons in the external orbit has a strong magnetic momentum, is the most used. Gadolinium by itself is extremely toxic but once it is linked with a chelanting agent such as DTPA (Dietilen-Triamin-Penta-Acetic acid) the resulting complex shows a very low toxicity. The number of Gadolinium based compound is growing together with the use of contrast agents in MRI. These contrast agents are routinely used to perform Magnetic Resonance Angiography (MRA) and to a better definition of several cardiac diseases such as the presence of a intra- or paracardiac mass, the evaluation of myocardial perfusion and the evaluation of viability. Both the latter applications have relevant clinical implications. In fact the assessment of myocardial perfusion is one of the most used approach for detecting inducible myocardial ischemia due to major coronary artery disease or to assess the presence of a microvascular disease. The presence and the extent of viable myocardium is deeply modifying the clinical decision making as this viable tissue can recruit a normal function spontaneously or after revascularisation. Furthermore, the extent of viable myocardium has a strong correlation with negative prognosis. Clinical events are also time related to the detection of viable tissue. These evidences imply that the diagnostic

  10. Introduction to Cardiovascular Magnetic Resonance: Technical Principles and Clinical Applications

    PubMed Central

    Tseng, Wen-Yih Isaac; Su, Mao-Yuan Marine; Tseng, Yao-Hui Elton

    2016-01-01

    Cardiovascular magnetic resonance (CMR) is a set of magnetic resonance imaging (MRI) techniques designed to assess cardiovascular morphology, ventricular function, myocardial perfusion, tissue characterization, flow quantification and coronary artery disease. Since MRI is a non-invasive tool and free of radiation, it is suitable for longitudinal monitoring of treatment effect and follow-up of disease progress. Compared to MRI of other body parts, CMR faces specific challenges from cardiac and respiratory motion. Therefore, CMR requires synchronous cardiac and respiratory gating or breath-holding techniques to overcome motion artifacts. This article will review the basic principles of MRI and introduce the CMR techniques that can be optimized for enhanced clinical assessment. PMID:27122944

  11. Advances in clinical applications of cardiovascular magnetic resonance imaging

    PubMed Central

    Bandettini, W P; Arai, A E

    2008-01-01

    Cardiovascular magnetic resonance (CMR) is an evolving technology with growing indications within the clinical cardiology setting. This review article summarises the current clinical applications of CMR. The focus is on the use of CMR in the diagnosis of coronary artery disease with summaries of validation literature in CMR viability, myocardial perfusion, and dobutamine CMR. Practical uses of CMR in non-coronary diseases are also discussed. PMID:18208827

  12. 'Magic Angle Precession'

    SciTech Connect

    Binder, Bernd

    2008-01-21

    An advanced and exact geometric description of nonlinear precession dynamics modeling very accurately natural and artificial couplings showing Lorentz symmetry is derived. In the linear description it is usually ignored that the geometric phase of relativistic motion couples back to the orbital motion providing for a non-linear recursive precession dynamics. The high coupling strength in the nonlinear case is found to be a gravitomagnetic charge proportional to the precession angle and angular velocity generated by geometric phases, which are induced by high-speed relativistic rotations and are relevant to propulsion technologies but also to basic interactions. In the quantum range some magic precession angles indicating strong coupling in a phase-locked chaotic system are identified, emerging from a discrete time dynamical system known as the cosine map showing bifurcations at special precession angles relevant to heavy nuclei stability. The 'Magic Angle Precession' (MAP) dynamics can be simulated and visualized by cones rolling in or on each other, where the apex and precession angles are indexed by spin, charge or precession quantum numbers, and corresponding magic angles. The most extreme relativistic warping and twisting effect is given by the Dirac spinor half spin constellation with 'Hyperdiamond' MAP, which resembles quark confinement.

  13. Assessment of Myocardial Ischemia with Cardiovascular Magnetic Resonance

    PubMed Central

    Heydari, Bobak; Jerosch-Herold, Michael; Kwong, Raymond Y.

    2014-01-01

    Assessment of myocardial ischemia in symptomatic patients remains a common and challenging clinical situation faced by physicians. Risk stratification by presence of ischemia provides important utility for both prognostic assessment and management. Unfortunately, current noninvasive modalities possess numerous limitations and have limited prognostic capacity. More recently, ischemia assessment by cardiovascular magnetic resonance (CMR) has been shown to be a safe, available, and potentially cost-effective alternative with both high diagnostic and prognostic accuracy. Cardiovascular magnetic resonance has numerous advantages over other noninvasive methods, including high temporal and spatial resolution, relatively few contraindications, and absence of ionizing radiation. Furthermore, studies assessing the clinical utility and cost effectiveness of CMR in the short-term setting for patients without evidence of an acute myocardial infarction have also demonstrated favorable results. This review will cover techniques of ischemia assessment with CMR by both stress-induced wall motion abnormalities as well as myocardial perfusion imaging. The diagnostic and prognostic performance studies will also be reviewed, and the use of CMR for ischemia assessment will be compared with other commonly used noninvasive modalities. PMID:22014487

  14. Review of journal of cardiovascular magnetic resonance 2010.

    PubMed

    Pennell, Dudley J; Firmin, David N; Kilner, Philip J; Manning, Warren J; Mohiaddin, Raad H; Prasad, Sanjay K

    2011-01-01

    There were 75 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2010, which is a 34% increase in the number of articles since 2009. The quality of the submissions continues to increase, and the editors were delighted with the recent announcement of the JCMR Impact Factor of 4.33 which showed a 90% increase since last year. Our acceptance rate is approximately 30%, but has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. Last year for the first time, the Editors summarized the papers for the readership into broad areas of interest or theme, which we felt would be useful to practitioners of cardiovascular magnetic resonance (CMR) so that you could review areas of interest from the previous year in a single article in relation to each other and other recent JCMR articles 1. This experiment proved very popular with a very high rate of downloading, and therefore we intend to continue this review annually. The papers are presented in themes and comparison is drawn with previously published JCMR papers to identify the continuity of thought and publication in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:21914185

  15. Review of journal of cardiovascular magnetic resonance 2010

    PubMed Central

    2011-01-01

    There were 75 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2010, which is a 34% increase in the number of articles since 2009. The quality of the submissions continues to increase, and the editors were delighted with the recent announcement of the JCMR Impact Factor of 4.33 which showed a 90% increase since last year. Our acceptance rate is approximately 30%, but has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. Last year for the first time, the Editors summarized the papers for the readership into broad areas of interest or theme, which we felt would be useful to practitioners of cardiovascular magnetic resonance (CMR) so that you could review areas of interest from the previous year in a single article in relation to each other and other recent JCMR articles [1]. This experiment proved very popular with a very high rate of downloading, and therefore we intend to continue this review annually. The papers are presented in themes and comparison is drawn with previously published JCMR papers to identify the continuity of thought and publication in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:21914185

  16. Review of Journal of Cardiovascular Magnetic Resonance 2009.

    PubMed

    Pennell, D J; Firmin, D N; Kilner, P J; Manning, W J; Mohiaddin, R H; Neubauer, S; Prasad, S K

    2010-01-01

    There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:20302618

  17. Review of Journal of Cardiovascular Magnetic Resonance 2009

    PubMed Central

    2010-01-01

    There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:20302618

  18. Technology Preview: X-Ray Fused With Magnetic Resonance During Invasive Cardiovascular Procedures

    PubMed Central

    Gutiérrez, Luis F.; de Silva, Ranil; Ozturk, Cengizhan; Sonmez, Merdim; Stine, Annette M.; Raval, Amish N.; Raman, Venkatesh K.; Sachdev, Vandana; Aviles, Ronnier J.; Waclawiw, Myron A.; McVeigh, Elliot R.; Lederman, Robert J.

    2009-01-01

    Background We have developed and validated a system for real-time X-ray fused with magnetic resonance imaging, MRI (XFM), to guide catheter procedures with high spatial precision. Our implementation overlays roadmaps—MRI-derived soft-tissue features of interest—onto conventional X-ray fluoroscopy. We report our initial clinical experience applying XFM, using external fiducial markers, electrocardiogram (ECG)-gating, and automated real-time correction for gantry and table movement. Methods This prospective case series for technical development was approved by the NHLBI Institutional Review Board and included 19 subjects. Multimodality external fiducial markers were affixed to patients’ skin before MRI, which included contrast-enhanced, 3D T1-weighted, or breath-held and ECG-gated 2D steady state free precession imaging at 1.5T. MRI-derived roadmaps were manually segmented while patients were transferred to a calibrated X-ray fluoroscopy system. Image spaces were registered using the fiducial markers and thereafter permitted unrestricted gantry rotation, table panning, and magnification changes. Static and ECG-gated MRI data were transformed from 3D to 2D to correspond with gantry and table position and combined with live X-ray images. Results Clinical procedures included graft coronary arteriography, right ventricular free-wall biopsy, and iliac and femoral artery recanalization and stenting. MRI roadmaps improved operator confidence, and in the biopsy cases, outperformed the best available alternative imaging modality. Registration errors were increased when external fiducial markers were affixed to more mobile skin positions, such as over the abdomen. Conclusion XFM using external fiducial markers is feasible during X-ray guided catheter treatments. Multimodality image fusion may prove a useful adjunct to invasive cardiovascular procedures. PMID:18022851

  19. Free nuclear precession gradiometer system

    SciTech Connect

    Hinton, G. F.

    1985-10-08

    A free nuclear precession gradiometer uses a fluid sample surrounded by a coil the fluid sample containing one or more nuclear species which display a magnetic moment. Current in the coil polarizes the nucleii, which when the current is abruptly terminated precess coherently about the earth's magnetic field. The exact frequency generated is a precise measure of the absolute value of the earth's magnetic field. The signal is in the form of a damped sinusoid with the rate of decay being a function of gradients in the ambient magnetic field. Two vector magnetometers are mounted rigidly on the sensor at the right angles to each other and to the earth's magnetic field. A servo system continuously orients the sensor in a two-axis gimbal system to reduce the output of the vector magnetometers to zero. The instrument is polarized, a counter is triggered to make the frequency measurement, and the signal is analyzed by determining the average amplitude of the signal over a precise interval of time. The result is simultaneous measurement of total intensity and total gradient.

  20. Precession as a driving mechanism for the geodynamo

    NASA Astrophysics Data System (ADS)

    Tilgner, A.

    Precession of the earth's rotation axis has long ago been proposed as a possible driving mechanism for the geodynamo. Past research has focused on convectively driven dynamos and relatively little is known about the hydrodynamics of precession, even in the absence of a magnetic field. Some properties of precession driven flows will be presented and the possiblity of these flows acting as dynamos will be discussed.

  1. Low rate of cardiovascular events in patients with acute myocarditis diagnosed by cardiovascular magnetic resonance

    PubMed Central

    De Stefano, Luciano; Yeyati, Ezequiel Levy; Pietrani, Marcelo; Kohan, Andres; Falconi, Mariano; Benger, Juan; Dragonetti, Laura; Garcia-Monaco, Ricardo; Cagide, Arturo

    2014-01-01

    Background Myocarditis is a relatively common inflammatory disease that affects the myocardium. Infectious disease accounts for most of the cases either because of a direct viral infection or post-viral immune-mediated reaction. Cardiovascular magnetic resonance (CMR) has become an established non-invasive diagnosis tool for acute myocarditis. A recent large single centre study with patients with biopsy-proven viral myocarditis undergoing CMR scans found a high rate of mortality. The aim of this study was to assess the rate of clinical events in our population of patients with diagnosed myocarditis by CMR scan. Methods Patients who consulted to the emergency department with diagnosis of myocarditis by CMR were retrospectively included in the study from January 2008 to May 2012. A CMR protocol was used in all patients, and were followed up to assess the rate of the composite endpoint of all-cause death, congestive heart failure, sudden cardiac death, hospitalization for cardiac cause, recurrent myocarditis or need of radiofrequency ablation or implantable cardiac defibrillator (ICD). A descriptive statistical analysis was performed. Results Thirty-two patients with myocarditis were included in the study. The mean age was 42.6±21.2 years and 81.2% were male. In a mean follow up of 30.4±17.8 months, the rate of the composite endpoint of all-cause death, congestive heart failure, sudden cardiac death, hospitalization for cardiac cause, recurrent myocarditis or need of radiofrequency ablation or ICD was 15.6% (n=5). Two patients had heart failure (one of them underwent heart transplant), one patient needed ICD because of ventricular tachycardia and two other patients were re-hospitalized, for recurrent chest pain and for recurrent myocarditis respectively. Conclusions In our series of acute myocarditis diagnosed by CMR we found a low rate of cardiovascular events without mortality. These findings might oppose data from recently published myocarditis trials. PMID

  2. Quantification of regional myocardial wall motion by cardiovascular magnetic resonance

    PubMed Central

    Jiang, Kai

    2014-01-01

    Cardiovascular magnetic resonance (CMR) is a versatile tool that also allows comprehensive and accurate measurement of both global and regional myocardial contraction. Quantification of regional wall motion parameters, such as strain, strain rate, twist and torsion, has been shown to be more sensitive to early-stage functional alterations. Since the invention of CMR tagging by magnetization saturation in 1988, several CMR techniques have been developed to enable the measurement of regional myocardial wall motion, including myocardial tissue tagging, phase contrast mapping, displacement encoding with stimulated echoes (DENSE), and strain encoded (SENC) imaging. These techniques have been developed with their own advantages and limitations. In this review, two widely used and closely related CMR techniques, i.e., tissue tagging and DENSE, will be discussed from the perspective of pulse sequence development and image-processing techniques. The clinical and preclinical applications of tissue tagging and DENSE in assessing wall motion mechanics in both normal and diseased hearts, including coronary artery diseases, hypertrophic cardiomyopathy, aortic stenosis, and Duchenne muscular dystrophies, will be discussed. PMID:25392821

  3. Multi-color magnetic particle imaging for cardiovascular interventions

    NASA Astrophysics Data System (ADS)

    Haegele, Julian; Vaalma, Sarah; Panagiotopoulos, Nikolaos; Barkhausen, Jörg; Vogt, Florian M.; Borgert, Jörn; Rahmer, Jürgen

    2016-08-01

    Magnetic particle imaging (MPI) uses magnetic fields to visualize the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs). Guidance of cardiovascular interventions is seen as one possible application of MPI. To safely guide interventions, the vessel lumen as well as all required interventional devices have to be visualized and be discernible from each other. Until now, different tracer concentrations were used for discerning devices from blood in MPI, because only one type of SPIO could be imaged at a time. Recently, it was shown for 3D MPI that it is possible to separate different signal sources in one volume of interest, i.e. to visualize and discern different SPIOs or different binding states of the same SPIO. The approach was termed multi-color MPI. In this work, the use of multi-color MPI for differentiation of a SPIO coated guide wire (Terumo Radifocus 0.035″) from the lumen of a vessel phantom filled with diluted Resovist is demonstrated. This is achieved by recording dedicated system functions of the coating material containing solid Resovist and of liquid Resovist, which allows separation of their respective signal in the image reconstruction process. Assigning a color to the different signal sources results in a differentiation of guide wire and vessel phantom lumen into colored images.

  4. Multi-color magnetic particle imaging for cardiovascular interventions.

    PubMed

    Haegele, Julian; Vaalma, Sarah; Panagiotopoulos, Nikolaos; Barkhausen, Jörg; Vogt, Florian M; Borgert, Jörn; Rahmer, Jürgen

    2016-08-21

    Magnetic particle imaging (MPI) uses magnetic fields to visualize the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs). Guidance of cardiovascular interventions is seen as one possible application of MPI. To safely guide interventions, the vessel lumen as well as all required interventional devices have to be visualized and be discernible from each other. Until now, different tracer concentrations were used for discerning devices from blood in MPI, because only one type of SPIO could be imaged at a time. Recently, it was shown for 3D MPI that it is possible to separate different signal sources in one volume of interest, i.e. to visualize and discern different SPIOs or different binding states of the same SPIO. The approach was termed multi-color MPI. In this work, the use of multi-color MPI for differentiation of a SPIO coated guide wire (Terumo Radifocus 0.035″) from the lumen of a vessel phantom filled with diluted Resovist is demonstrated. This is achieved by recording dedicated system functions of the coating material containing solid Resovist and of liquid Resovist, which allows separation of their respective signal in the image reconstruction process. Assigning a color to the different signal sources results in a differentiation of guide wire and vessel phantom lumen into colored images. PMID:27476675

  5. Prognostic value of normal regadenoson stress perfusion cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    Background Regadenoson is a vasodilator stress agent that selectively activates the A2A receptor. Compared to adenosine, regadenoson is easier to administer and results in fewer side effects. Although extensively studied in patients undergoing nuclear perfusion imaging (MPI), its use for perfusion cardiovascular magnetic resonance (CMR) is not well described. The aim of this study was to determine the prognostic value of a normal regadenoson perfusion CMR in patients with known or suspected coronary artery disease. Methods Patients with known or suspected coronary artery disease were prospectively enrolled to receive perfusion CMR (Philips 1.5 T) with regadenoson. Three short-axis slices of the left ventricle (LV) were obtained during first pass of contrast using a hybrid GRE-EPI pulse sequence (0.075 mmol/kg Gadolinium-DTPA-BMA at 4 ml/sec). Imaging was performed 1 minute after injection of regadenoson (0.4 mg) and repeated 15 minutes after reversal of hyperemia with aminophylline (125 mg). Perfusion defects were documented if they persisted for ≥2 frames after peak enhancement of the LV cavity. CMR was considered abnormal if there was a resting wall motion abnormality, decreased LVEF (<40%), presence of LGE, or the presence of a perfusion defect during hyperemia. All patients were followed for a minimum of 1 year for major adverse cardiovascular event (MACE) defined as coronary revascularization, non-fatal myocardial infarction, and cardiovascular death. Results 149 patients were included in the final analysis. Perfusion defects were noted in 43/149 (29%) patients; 59/149 (40%) had any abnormality on CMR. During the mean follow-up period of 24 ± 9 months, 17/149 (11.4%) patients experienced MACE. The separation in the survival distributions for those with perfusion defects and those without perfusion defects was highly significant (log-rank p = 0.0001). When the absence of perfusion defects was added to the absence of other resting CMR

  6. Cardiovascular imaging in the diagnosis and monitoring of cardiotoxicity: cardiovascular magnetic resonance and nuclear cardiology.

    PubMed

    Pepe, Alessia; Pizzino, Fausto; Gargiulo, Paola; Perrone-Filardi, Pasquale; Cadeddu, Christian; Mele, Donato; Monte, Ines; Novo, Giuseppina; Zito, Concetta; Di Bella, Gianluca

    2016-05-01

    Chemotherapy-induced cardiotoxicity (CTX) is a determining factor for the quality of life and mortality of patients administered potentially cardiotoxic drugs and in long-term cancer survivors. Therefore, prevention and early detection of CTX are highly desirable, as is the exploration of alternative therapeutic strategies and/or the proposal of potentially cardioprotective treatments. In recent years, cardiovascular imaging has acquired a pivotal role in this setting. Although echocardiography remains the diagnostic method most used to monitor cancer patients, the need for more reliable, reproducible and accurate detection of early chemotherapy-induced CTX has encouraged the introduction of second-line advanced imaging modalities, such as cardiac magnetic resonance (CMR) and nuclear techniques, into the clinical setting. This review of the Working Group on Drug Cardiotoxicity and Cardioprotection of the Italian Society of Cardiology aims to afford an overview of the most important findings from the literature about the role of CMR and nuclear techniques in the management of chemotherapy-treated patients, describe conventional and new parameters for detecting CTX from both diagnostic and prognostic perspectives and provide integrated insight into the role of CMR and nuclear techniques compared with other imaging tools and versus the positions of the most important international societies. PMID:27183525

  7. The emerging clinical role of cardiovascular magnetic resonance imaging

    PubMed Central

    Kumar, Andreas; Patton, David J; Friedrich, Matthias G

    2010-01-01

    Starting as a research method little more than a decade ago, cardiovascular magnetic resonance (CMR) imaging has rapidly evolved to become a powerful diagnostic tool used in routine clinical cardiology. The contrast in CMR images is generated from protons in different chemical environments and, therefore, enables high-resolution imaging and specific tissue characterization in vivo, without the use of potentially harmful ionizing radiation. CMR imaging is used for the assessment of regional and global ventricular function, and to answer questions regarding anatomy. State-of-the-art CMR sequences allow for a wide range of tissue characterization approaches, including the identification and quantification of nonviable, edematous, inflamed, infiltrated or hypoperfused myocardium. These tissue changes are not only used to help identify the etiology of cardiomyopathies, but also allow for a better understanding of tissue pathology in vivo. CMR tissue characterization may also be used to stage a disease process; for example, elevated T2 signal is consistent with edema and helps differentiate acute from chronic myocardial injury, and the extent of myocardial fibrosis as imaged by contrast-enhanced CMR correlates with adverse patient outcome in ischemic and nonischemic cardiomyopathies. The current role of CMR imaging in clinical cardiology is reviewed, including coronary artery disease, congenital heart disease, nonischemic cardiomyopathies and valvular disease. PMID:20548977

  8. Fractal frontiers in cardiovascular magnetic resonance: towards clinical implementation.

    PubMed

    Captur, Gabriella; Karperien, Audrey L; Li, Chunming; Zemrak, Filip; Tobon-Gomez, Catalina; Gao, Xuexin; Bluemke, David A; Elliott, Perry M; Petersen, Steffen E; Moon, James C

    2015-01-01

    Many of the structures and parameters that are detected, measured and reported in cardiovascular magnetic resonance (CMR) have at least some properties that are fractal, meaning complex and self-similar at different scales. To date however, there has been little use of fractal geometry in CMR; by comparison, many more applications of fractal analysis have been published in MR imaging of the brain.This review explains the fundamental principles of fractal geometry, places the fractal dimension into a meaningful context within the realms of Euclidean and topological space, and defines its role in digital image processing. It summarises the basic mathematics, highlights strengths and potential limitations of its application to biomedical imaging, shows key current examples and suggests a simple route for its successful clinical implementation by the CMR community.By simplifying some of the more abstract concepts of deterministic fractals, this review invites CMR scientists (clinicians, technologists, physicists) to experiment with fractal analysis as a means of developing the next generation of intelligent quantitative cardiac imaging tools. PMID:26346700

  9. MRXCAT: Realistic numerical phantoms for cardiovascular magnetic resonance

    PubMed Central

    2014-01-01

    Background Computer simulations are important for validating novel image acquisition and reconstruction strategies. In cardiovascular magnetic resonance (CMR), numerical simulations need to combine anatomical information and the effects of cardiac and/or respiratory motion. To this end, a framework for realistic CMR simulations is proposed and its use for image reconstruction from undersampled data is demonstrated. Methods The extended Cardiac-Torso (XCAT) anatomical phantom framework with various motion options was used as a basis for the numerical phantoms. Different tissue, dynamic contrast and signal models, multiple receiver coils and noise are simulated. Arbitrary trajectories and undersampled acquisition can be selected. The utility of the framework is demonstrated for accelerated cine and first-pass myocardial perfusion imaging using k-t PCA and k-t SPARSE. Results MRXCAT phantoms allow for realistic simulation of CMR including optional cardiac and respiratory motion. Example reconstructions from simulated undersampled k-t parallel imaging demonstrate the feasibility of simulated acquisition and reconstruction using the presented framework. Myocardial blood flow assessment from simulated myocardial perfusion images highlights the suitability of MRXCAT for quantitative post-processing simulation. Conclusion The proposed MRXCAT phantom framework enables versatile and realistic simulations of CMR including breathhold and free-breathing acquisitions. PMID:25204441

  10. Visualization of coronary venous anatomy by cardiovascular magnetic resonance

    PubMed Central

    Younger, John F; Plein, Sven; Crean, Andrew; Ball, Stephen G; Greenwood, John P

    2009-01-01

    Background Coronary venous imaging with whole-heart cardiovascular magnetic resonance (CMR) angiography has recently been described using developmental pulse sequences and intravascular contrast agents. However, the practical utility of coronary venous imaging will be for patients with heart failure in whom cardiac resynchronisation therapy (CRT) is being considered. As such complementary information on ventricular function and myocardial viability will be required. The aim of this study was to determine if the coronary venous anatomy could be depicted as part of a comprehensive CMR protocol and using a standard extracellular contrast agent. Methods and Results Thirty-one 3D whole heart CMR studies, performed after intravenous administration of 0.05 mmol/kg gadolinium DTPA, were reviewed. The cardiac venous system was visualized in all patients. The lateral vein of the left ventricle was present in 74%, the anterior interventricular vein in 65%, and the posterior interventricular vein in 74% of patients. The mean maximum distance of demonstrable cardiac vein on the 3D images was 81.5 mm and was dependent on the quality of the 3D data set. Five patients showed evidence of myocardial infarction on late gadolinium enhancement (LGE) images. Conclusion Coronary venous anatomy can be reliably demonstrated using a comprehensive CMR protocol and a standard extracellular contrast agent. The combination of coronary venous imaging, assessment of ventricular function and LGE may be useful in the management of patients with LV dysfunction being considered for CRT. PMID:19671132

  11. Assessment of the right ventricle with cardiovascular magnetic resonance at 7 Tesla

    PubMed Central

    2013-01-01

    Background Functional and morphologic assessment of the right ventricle (RV) is of clinical importance. Cardiovascular magnetic resonance (CMR) at 1.5T has become gold standard for RV chamber quantification and assessment of even small wall motion abnormalities, but tissue analysis is still hampered by limited spatial resolution. CMR at 7T promises increased resolution, but is technically challenging. We examined the feasibility of cine imaging at 7T to assess the RV. Methods Nine healthy volunteers underwent CMR at 7T using a 16-element TX/RX coil and acoustic cardiac gating. 1.5T served as gold standard. At 1.5T, steady-state free-precession (SSFP) cine imaging with voxel size (1.2x1.2x6) mm3 was used; at 7T, fast gradient echo (FGRE) with voxel size (1.2x1.2x6) mm3 and (1.3x1.3x4) mm3 were applied. RV dimensions (RVEDV, RVESV), RV mass (RVM) and RV function (RVEF) were quantified in transverse slices. Overall image quality, image contrast and image homogeneity were assessed in transverse and sagittal views. Results All scans provided diagnostic image quality. Overall image quality and image contrast of transverse RV views were rated equally for SSFP at 1.5T and FGRE at 7T with voxel size (1.3x1.3x4)mm3. FGRE at 7T provided significantly lower image homogeneity compared to SSFP at 1.5T. RVEDV, RVESV, RVEF and RVM did not differ significantly and agreed close between SSFP at 1.5T and FGRE at 7T (p=0.5850; p=0.5462; p=0.2789; p=0.0743). FGRE at 7T with voxel size (1.3x1.3x4) mm3 tended to overestimate RV volumes compared to SSFP at 1.5T (mean difference of RVEDV 8.2±9.3ml) and to FGRE at 7T with voxel size (1.2x1.2x6) mm3 (mean difference of RVEDV 9.3±8.6ml). Conclusions FGRE cine imaging of the RV at 7T was feasible and provided good image quality. RV dimensions and function were comparable to SSFP at 1.5T as gold standard. PMID:23497030

  12. Disk Precession in Pleione

    NASA Astrophysics Data System (ADS)

    Hirata, R.

    2007-03-01

    From the polarimetric observation of Pleione, we found that the intrinsic polarization angle varied from 60° to 130° in 1974-2003. The Hα profile also changed dramatically from the edge-on type (shell-line profile) to the surface-on type (wine-bottle profile). These facts clearly indicate the spatial motion of the disk axis. We interpret these variations in terms of the disk precession, caused by the secondary of this spectroscopic binary with a period of 218d. We performed the χ^2 minimization for the polarization angle, assuming uniform precession with an imposed condition that the shell maximum occurred at edge-on view. The resulting precession angle is 59° with a period of 81 years. Then, we can describe chronologically the spatial motion of disk axis. We also derived the Hα disk radius from the peak separation, assuming the Keplerian disk. The precession of the disk gives natural explanation of the mysterious long-term spectroscopic behaviors of this star.

  13. Dynamical Torque in CoxFe3–xO4 Nanocube Thin Films Characterized by Femtosecond Magneto-Optics: A π-Shift Control of the Magnetization Precession

    PubMed Central

    2016-01-01

    For spintronic devices excited by a sudden magnetic or optical perturbation, the torque acting on the magnetization plays a key role in its precession and damping. However, the torque itself can be a dynamical quantity via the time-dependent anisotropies of the system. A challenging problem for applications is then to disentangle the relative importance of various sources of anisotropies in the dynamical torque, such as the dipolar field, the crystal structure or the shape of the particular interacting magnetic nanostructures. Here, we take advantage of a range of colloidal cobalt ferrite nanocubes assembled in 2D thin films under controlled magnetic fields to demonstrate that the phase, ϕPrec, of the precession carries a strong signature of the dynamical anisotropies. Performing femtosecond magneto-optics, we show that ϕPrec displays a π-shift for a particular angle θH of an external static magnetic field, H. θH is controlled with the cobalt concentration, the laser intensity, as well as the interparticle interactions. Importantly, it is shown that the shape anisotropy, which strongly departs from those of equivalent bulk thin films or individual noninteracting nanoparticles, reveals the essential role played by the interparticle collective effects. This work shows the reliability of a noninvasive optical approach to characterize the dynamical torque in high density magnetic recording media made of organized and interacting nanoparticles. PMID:27398653

  14. Dynamical Torque in CoxFe3-xO4 Nanocube Thin Films Characterized by Femtosecond Magneto-Optics: A π-Shift Control of the Magnetization Precession.

    PubMed

    Vomir, Mircea; Turnbull, Robin; Birced, Ipek; Parreira, Pedro; MacLaren, Donald A; Lee, Stephen L; André, Pascal; Bigot, Jean-Yves

    2016-08-10

    For spintronic devices excited by a sudden magnetic or optical perturbation, the torque acting on the magnetization plays a key role in its precession and damping. However, the torque itself can be a dynamical quantity via the time-dependent anisotropies of the system. A challenging problem for applications is then to disentangle the relative importance of various sources of anisotropies in the dynamical torque, such as the dipolar field, the crystal structure or the shape of the particular interacting magnetic nanostructures. Here, we take advantage of a range of colloidal cobalt ferrite nanocubes assembled in 2D thin films under controlled magnetic fields to demonstrate that the phase, ϕPrec, of the precession carries a strong signature of the dynamical anisotropies. Performing femtosecond magneto-optics, we show that ϕPrec displays a π-shift for a particular angle θH of an external static magnetic field, H. θH is controlled with the cobalt concentration, the laser intensity, as well as the interparticle interactions. Importantly, it is shown that the shape anisotropy, which strongly departs from those of equivalent bulk thin films or individual noninteracting nanoparticles, reveals the essential role played by the interparticle collective effects. This work shows the reliability of a noninvasive optical approach to characterize the dynamical torque in high density magnetic recording media made of organized and interacting nanoparticles. PMID:27398653

  15. Highlights of the 16th annual scientific sessions of the Society for Cardiovascular Magnetic Resonance

    PubMed Central

    2013-01-01

    The 16th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance (SCMR) took place in San Francisco, USA at the end of January 2013. With a faculty of experts from across the world, this congress provided a wealth of insight into cutting-edge research and technological development. This review article intends to provide a highlight of what represented the most significant advances in the field of cardiovascular magnetic resonance (CMR) during this year’s meeting. PMID:23870663

  16. General spin precession and betatron oscillation in storage rings

    NASA Astrophysics Data System (ADS)

    Fukuyama, Takeshi

    2016-07-01

    Spin precession of particles having both anomalous magnetic and electric dipole moments (EDMs) is considered. We give the generalized expression of spin precession of these particles injected with transversal extent in magnetic storage rings. This is the generalization of the Farley’s pitch correction [F. J. N. Farley, Phys. Lett. B 42, 66 (1972)], including radial oscillation as well as vertical one. The transversal betatron oscillation formulae of these particles are also reproduced.

  17. Cardiovascular magnetic resonance: Diagnostic utility and specific considerations in the pediatric population

    PubMed Central

    Mitchell, Frances M; Prasad, Sanjay K; Greil, Gerald F; Drivas, Peter; Vassiliou, Vassilios S; Raphael, Claire E

    2016-01-01

    Cardiovascular magnetic resonance is a non-invasive imaging modality which is emerging as important tool for the investigation and management of pediatric cardiovascular disease. In this review we describe the key technical and practical differences between scanning children and adults, and highlight some important considerations that must be taken into account for this patient population. Using case examples commonly seen in clinical practice, we discuss the important clinical applications of cardiovascular magnetic resonance, and briefly highlight key future developments in this field. PMID:26862497

  18. Review of Journal of Cardiovascular Magnetic Resonance 2012

    PubMed Central

    2013-01-01

    There were 90 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2012, which is an 8% increase in the number of articles since 2011. The quality of the submissions continues to increase. The editors are delighted to report that the 2011 JCMR Impact Factor (which is published in June 2012) has risen to 4.44, up from 3.72 for 2010 (as published in June 2011), a 20% increase. The 2011 impact factor means that the JCMR papers that were published in 2009 and 2010 were cited on average 4.44 times in 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:24006874

  19. Arrhythmogenic right ventricular cardiomyopathy mimics: role of cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    Background Cardiovascular magnetic resonance (CMR) is commonly used in patients with suspected arrhythmogenic right ventricular cardiomyopathy (ARVC) based on ECG, echocardiogram and Holter. However, various diseases may present with clinical characteristics resembling ARVC causing diagnostic dilemmas. The aim of this study was to explore the role of CMR in the differential diagnosis of patients with suspected ARVC. Methods 657 CMR referrals suspicious for ARVC in a single tertiary referral centre were analysed. Standardized CMR imaging protocols for ARVC were performed. Potential ARVC mimics were grouped into: 1) displacement of the heart, 2) right ventricular overload, and 3) non ARVC-like cardiac scarring. For each, a judgment of clinical impact was made. Results Twenty patients (3.0%) fulfilled imaging ARVC criteria. Thirty (4.6%) had a potential ARVC mimic, of which 25 (3.8%) were considered clinically important: cardiac displacement (n=17), RV overload (n=7) and non-ARVC like myocardial scarring (n=4). One patient had two mimics; one patient had dual pathology with important mimic and ARVC. RV overload and scarring conditions were always thought clinically important whilst the importance of cardiac displacement depended on the degree of displacement from severe (partial absence of pericardium) to epiphenomenon (minor kyphoscoliosis). Conclusions Some patients referred for CMR with suspected ARVC fulfil ARVC imaging criteria (3%) but more have otherwise unrecognised diseases (4.6%) mimicking potentially ARVC. Clinical assessment should reflect this, emphasising the assessment and/or exclusion of potential mimics in parallel with the detection of ARVC major and minor criteria. PMID:23398958

  20. Review of Journal of Cardiovascular Magnetic Resonance 2014.

    PubMed

    Pennell, D J; Baksi, A J; Prasad, S K; Raphael, C E; Kilner, P J; Mohiaddin, R H; Alpendurada, F; Babu-Narayan, S V; Schneider, J; Firmin, D N

    2015-01-01

    There were 102 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2014, which is a 6% decrease on the 109 articles published in 2013. The quality of the submissions continues to increase. The 2013 JCMR Impact Factor (which is published in June 2014) fell to 4.72 from 5.11 for 2012 (as published in June 2013). The 2013 impact factor means that the JCMR papers that were published in 2011 and 2012 were cited on average 4.72 times in 2013. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25% and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality papers to JCMR for publication. PMID:26589839

  1. Review of Journal of Cardiovascular Magnetic Resonance 2011.

    PubMed

    Pennell, Dudley J; Carpenter, John Paul; Firmin, David N; Kilner, Philip J; Mohiaddin, Raad H; Prasad, Sanjay K

    2012-01-01

    There were 83 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2011, which is an 11% increase in the number of articles since 2010. The quality of the submissions continues to increase. The editors had been delighted with the 2010 JCMR Impact Factor of 4.33, although this fell modestly to 3.72 for 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, we remain very pleased with the progress of the journal's impact over the last 5 years. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors feel it is useful to summarize the papers for the readership into broad areas of interest or theme, which we feel would be useful, so that areas of interest from the previous year can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:23158097

  2. Review of Journal of Cardiovascular Magnetic Resonance 2011

    PubMed Central

    2012-01-01

    There were 83 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2011, which is an 11% increase in the number of articles since 2010. The quality of the submissions continues to increase. The editors had been delighted with the 2010 JCMR Impact Factor of 4.33, although this fell modestly to 3.72 for 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, we remain very pleased with the progress of the journal's impact over the last 5 years. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors feel it is useful to summarize the papers for the readership into broad areas of interest or theme, which we feel would be useful, so that areas of interest from the previous year can be reviewed in a single article in relation to each other and other recent JCMR articles [1]. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:23158097

  3. Review of Journal of Cardiovascular Magnetic Resonance 2012.

    PubMed

    Pennell, Dudley J; Baksi, A John; Carpenter, John Paul; Firmin, David N; Kilner, Philip J; Mohiaddin, Raad H; Prasad, Sanjay K

    2013-01-01

    There were 90 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2012, which is an 8% increase in the number of articles since 2011. The quality of the submissions continues to increase. The editors are delighted to report that the 2011 JCMR Impact Factor (which is published in June 2012) has risen to 4.44, up from 3.72 for 2010 (as published in June 2011), a 20% increase. The 2011 impact factor means that the JCMR papers that were published in 2009 and 2010 were cited on average 4.44 times in 2011. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is approximately 25%, and has been falling as the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:24006874

  4. Review of Journal of Cardiovascular Magnetic Resonance 2013.

    PubMed

    Pennell, Dudley John; Baksi, Arun John; Kilner, Philip John; Mohiaddin, Raad Hashem; Prasad, Sanjay Kumar; Alpendurada, Francisco; Babu-Narayan, Sonya Vidya; Neubauer, Stefan; Firmin, David Nigel

    2014-01-01

    There were 109 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2013, which is a 21% increase on the 90 articles published in 2012. The quality of the submissions continues to increase. The editors are delighted to report that the 2012 JCMR Impact Factor (which is published in June 2013) has risen to 5.11, up from 4.44 for 2011 (as published in June 2012), a 15% increase and taking us through the 5 threshold for the first time. The 2012 impact factor means that the JCMR papers that were published in 2010 and 2011 were cited on average 5.11 times in 2012. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25% and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication. PMID:25475898

  5. Cardiovascular magnetic resonance physics for clinicians: Part II.

    PubMed

    Biglands, John D; Radjenovic, Aleksandra; Ridgway, John P

    2012-01-01

    This is the second of two reviews that is intended to cover the essential aspects of cardiovascular magnetic resonance (CMR) physics in a way that is understandable and relevant to clinicians using CMR in their daily practice. Starting with the basic pulse sequences and contrast mechanisms described in part I, it briefly discusses further approaches to accelerate image acquisition. It then continues by showing in detail how the contrast behaviour of black blood fast spin echo and bright blood cine gradient echo techniques can be modified by adding rf preparation pulses to derive a number of more specialised pulse sequences. The simplest examples described include T2-weighted oedema imaging, fat suppression and myocardial tagging cine pulse sequences. Two further important derivatives of the gradient echo pulse sequence, obtained by adding preparation pulses, are used in combination with the administration of a gadolinium-based contrast agent for myocardial perfusion imaging and the assessment of myocardial tissue viability using a late gadolinium enhancement (LGE) technique. These two imaging techniques are discussed in more detail, outlining the basic principles of each pulse sequence, the practical steps required to achieve the best results in a clinical setting and, in the case of perfusion, explaining some of the factors that influence current approaches to perfusion image analysis. The key principles of contrast-enhanced magnetic resonance angiography (CE-MRA) are also explained in detail, especially focusing on timing of the acquisition following contrast agent bolus administration, and current approaches to achieving time resolved MRA. Alternative MRA techniques that do not require the use of an endogenous contrast agent are summarised, and the specialised pulse sequence used to image the coronary arteries, using respiratory navigator gating, is described in detail. The article concludes by explaining the principle behind phase contrast imaging techniques

  6. Cardiovascular magnetic resonance physics for clinicians: part II

    PubMed Central

    2012-01-01

    This is the second of two reviews that is intended to cover the essential aspects of cardiovascular magnetic resonance (CMR) physics in a way that is understandable and relevant to clinicians using CMR in their daily practice. Starting with the basic pulse sequences and contrast mechanisms described in part I, it briefly discusses further approaches to accelerate image acquisition. It then continues by showing in detail how the contrast behaviour of black blood fast spin echo and bright blood cine gradient echo techniques can be modified by adding rf preparation pulses to derive a number of more specialised pulse sequences. The simplest examples described include T2-weighted oedema imaging, fat suppression and myocardial tagging cine pulse sequences. Two further important derivatives of the gradient echo pulse sequence, obtained by adding preparation pulses, are used in combination with the administration of a gadolinium-based contrast agent for myocardial perfusion imaging and the assessment of myocardial tissue viability using a late gadolinium enhancement (LGE) technique. These two imaging techniques are discussed in more detail, outlining the basic principles of each pulse sequence, the practical steps required to achieve the best results in a clinical setting and, in the case of perfusion, explaining some of the factors that influence current approaches to perfusion image analysis. The key principles of contrast-enhanced magnetic resonance angiography (CE-MRA) are also explained in detail, especially focusing on timing of the acquisition following contrast agent bolus administration, and current approaches to achieving time resolved MRA. Alternative MRA techniques that do not require the use of an endogenous contrast agent are summarised, and the specialised pulse sequence used to image the coronary arteries, using respiratory navigator gating, is described in detail. The article concludes by explaining the principle behind phase contrast imaging techniques

  7. Sr{sub 4}Ru{sub 6}ClO{sub 18}, a new Ru{sup 4+/5+} oxy-chloride, solved by precession electron diffraction: Electric and magnetic behavior

    SciTech Connect

    Roussel, Pascal; Palatinus, Lukas; Belva, Frédéric; Daviero-Minaud, Sylvie; Mentre, Olivier; Huve, Marielle

    2014-04-01

    The crystal structure of Sr{sub 4}Ru{sub 6}ClO{sub 18}, a new Ru{sup 4+/5+} oxo-chloride, has been determined from Precession Electron Diffraction (PED) data acquired on a nanocrystal in a transmission electron microscope using the technique of electron diffraction tomography. This approach is described in details following a pedagogic route and a systematic comparison is made of this rather new method with other experimental methods of electron diffraction, and with the standard single crystal X-ray diffraction technique. Both transport and magnetic measurements, showed a transition at low temperature that may be correlated to Ru{sup 4+}/Ru{sup 5+} charge ordering. - Graphical abstract: Structure of Sr{sub 4}Ru{sub 6}ClO{sub 18}, determined using Precession Electron Diffraction data. - Highlights: • Structure of Sr{sub 4}Ru{sub 6}ClO{sub 18} was solved ab initio using precession electron diffraction. • This was done both on a nanometric sample and on a micrometric one. • Different type of experimental methods of electron diffraction are compared. • Single crystal X-ray diffraction was used to confirm the results. • Transport properties were characterized and show “exotic” behavior.

  8. Does the Atmosphere Precess?

    NASA Astrophysics Data System (ADS)

    Hester, R. E., Jr.

    2015-12-01

    The study considers a north-south pair of mid-latitude rings of atmospheric mass, symmetric with respect to the equator, and rotating with respect to the distant stars. The mass and angular velocity are assigned similar to the annual and zonal mean upper level westerlies. Their relatively rapid rotation is assumed to allow a rigid body approximation on long time and space scales. The rings are constrained to move as if rigidly connected to a common axis of rotation. The pair thus constitutes a symmetric top with a fixed pivot point at the center of mass. Analysis of the dynamics follows the classical mechanics approach used for precession of the equinoxes. The theoretical rate of precession for this highly idealized system yields a period on the order of decades. The predicted dynamics appears consistent with three prior studies of observational data: latitudinal movements of atmospheric circulation above far Southern Australia, latitudinal movements of ocean circulation in the Kuroshio Extension, and changes in global Atmospheric Angular Momentum before and after 1976. Each of these observational records indicates correlation with the Pacific Decadal Oscillation. The theoretical dynamics in combination with the observations suggests the axis of rotation of the atmospheric westerlies is offset from the Earth axis by a few degrees, and further, that this axis precesses around a mean axis on a time scale of a few decades.

  9. Clinical Utility of Cardiovascular Magnetic Resonance in Hypertrophic Cardiomyopathy

    PubMed Central

    2012-01-01

    Hypertrophic cardiomyopathy (HCM) is characterized by substantial genetic and phenotypic heterogeneity, leading to considerable diversity in clinical course including the most common cause of sudden death in young people and a determinant of heart failure symptoms in patients of any age. Traditionally, two-dimensional echocardiography has been the most reliable method for establishing a clinical diagnosis of HCM. However, cardiovascular magnetic resonance (CMR), with its high spatial resolution and tomographic imaging capability, has emerged as a technique particularly well suited to characterize the diverse phenotypic expression of this complex disease. For example, CMR is often superior to echocardiography for HCM diagnosis, by identifying areas of segmental hypertrophy (ie., anterolateral wall or apex) not reliably visualized by echocardiography (or underestimated in terms of extent). High-risk HCM patient subgroups identified with CMR include those with thin-walled scarred LV apical aneurysms (which prior to CMR imaging in HCM remained largely undetected), end-stage systolic dysfunction, and massive LV hypertrophy. CMR observations also suggest that the cardiomyopathic process in HCM is more diffuse than previously regarded, extending beyond the LV myocardium to include thickening of the right ventricular wall as well as substantial morphologic diversity with regard to papillary muscles and mitral valve. These findings have implications for management strategies in patients undergoing invasive septal reduction therapy. Among HCM family members, CMR has identified unique phenotypic markers of affected genetic status in the absence of LV hypertrophy including: myocardial crypts, elongated mitral valve leaflets and late gadolinium enhancement. The unique capability of contrast-enhanced CMR with late gadolinium enhancement to identify myocardial fibrosis has raised the expectation that this may represent a novel marker, which may enhance risk stratification. At

  10. [Utility of cardiovascular magnetic resonance in hypertrophic cardiomyopathy: when is it superior to echocardiography?].

    PubMed

    Kammoun, I; Marrakchi, S; Zidi, A; Ibn ElHaj, Z; Naccache, S; Ben Amara, W; Jebri, F; Bennour, E; Kachboura, S

    2015-02-01

    The diagnosis of hypertrophic cardiomyopathy is usually established by echocardiography. Recently, there has been greatly increased use of cardiac magnetic resonance (CMR) because of its precise determination of myocardial anatomy and the depiction of myocardial fibrosis. In this review, we describe the role of echocardiography and magnetic resonance in the assessment of this complex disease. In conclusion, there is a complementarity between cardiovascular magnetic resonance imaging and echocardiography for the diagnosis and the management of HCM. PMID:24834991

  11. Evaluation of aortic stenosis by cardiovascular magnetic resonance imaging: comparison with established routine clinical techniques

    PubMed Central

    Kupfahl, C; Honold, M; Meinhardt, G; Vogelsberg, H; Wagner, A; Mahrholdt, H; Sechtem, U

    2004-01-01

    Objective: To evaluate whether direct planimetry of aortic valve area (AVA) by cardiac magnetic resonance (CMR) imaging is a reliable tool for determining the severity of aortic stenosis compared with transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE), and cardiac catheterisation. Methods: 44 symptomatic patients with severe aortic stenosis were studied. By cardiac catheterisation AVA was calculated by the Gorlin equation. AVA was measured with CMR from steady state free precession (true fast imaging with steady state precession) by planimetry. AVA was also determined from TOE images by planimetry and from TTE images by the continuity equation. Results: Bland-Altman analysis evaluating intraobserver and interobserver variability showed a very small bias for both (−0.016 and 0.019, respectively; n  =  20). Bias and limits of agreement between CMR and TTE were 0.05 (−0.35, 0.44) cm2 (n  =  37), between CMR and TOE 0.02 (−0.39, 0.42) cm2 (n  =  32), and between CMR and cardiac catheterisation 0.09 (−0.30, 0.47) cm2 (n  =  36). The sensitivity and specificity of CMR to detect AVA ⩽ 0.80 cm2 measured by cardiac catheterisation was 78% and 89%, of TOE 70% and 70%, and of TTE 74% and 67%, respectively. Conclusion: CMR planimetry is highly reliable and reproducible. Further, CMR planimetry had the best sensitivity and specificity of all non-invasive methods for detecting severe aortic stenosis in comparison with cardiac catheterisation. Therefore, CMR planimetry of AVA with steady state free precession is a new powerful diagnostic tool, particularly for patients with uncertain or discrepant findings by other modalities. PMID:15253962

  12. Cardiovascular Magnetic Resonance in Cardiology Practice: A Concise Guide to Image Acquisition and Clinical Interpretation.

    PubMed

    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. PMID:26778592

  13. The precession dynamo experiment at HZDR

    NASA Astrophysics Data System (ADS)

    Giesecke, A.; Gundrum, T.; Herault, J.; Stefani, F.; Gerbeth, G.

    2015-12-01

    In a next generation dynamo experiment currently under development atthe Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquidsodium, solely driven by precession, will be considered as a possiblesource for magnetic field generation. The experiment is mainlymotivated by alternative concepts for astrophysical dynamos that arebased on mechanical flow driving. For example, it has long beendiscussed whether precession may be a complementary power source forthe geodynamo (Malkus, Science 1968) or for the ancient lunar dynamodue to the Earth-driven precession of the lunar spin axis (Dwyer, Nature 2011).We will present the current state of development of the dynamoexperiment together with results from non-linear hydrodynamicsimulations with moderate precessional forcing. Our simulations reveala non-axisymmetric forced mode with an amplitude of up to one fourthof the rotation velocity of the cylindrical container confirming thatprecession provides a rather efficient flow driving mechanism even atmoderate precession rates.More relevant for dynamo action might be free Kelvin modes (thenatural flow eigenmodes in a rotating cylinder) with higher azimuthalwave number. These modes may become relevant when constituting atriadic resonance with the fundamental forced mode, i.e., when theheight of the container matches their axial wave lengths. We findtriadic resonances at aspect ratios close to those predicted by thelinear theory except around the primary resonance of the forcedmode. In that regime we still identify free Kelvin modes propagatingin retrograde direction but none of them can be assigned to a triade.Our results will enter into the development of flow models that willbe used in kinematic simulations of the electromagnetic inductionequation in order to determine whether a precession driven flow willbe capable to drive a dynamo at all and to limit the parameter spacewithin which the occurrence of dynamo action is most promising.

  14. Understanding cardiovascular injury after treatment for cancer: an overview of current uses and future directions of cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    While cancer-free survival has improved over the past 20 years for many individuals with prostate, renal, breast, and hematologic malignancies, the increasingly recognized prevalence of cardiovascular (CV) events in cancer survivors has been an unintended consequence of many of the therapies that have improved these survival rates. The increase in CV events threatens to offset the improvement in cancer related survival. As a result, there is an emerging need to develop methods to identify those individuals treated for cancer at increased risk of cardiovascular events. With its inherent ability to characterize myocardial tissue and identify both cardiac and vascular dysfunction, cardiovascular magnetic resonance (CMR) has the potential to identify both subclinical and early clinical CV injury before the development of an overt catastrophic event such as a myocardial infarction, stroke, or premature cardiac death. Early identification provides an opportunity for the implementation of primary prevention strategies to prevent such events, thereby improving overall cancer survivorship and quality of life. This article reviews the etiology of CV events associated with cancer therapy and the unique potential of CMR to provide early diagnosis of subclinical CV injury related to the administration of these therapies. PMID:23902649

  15. Laser-Induced Fast Magnetization Precession and Gilbert Damping for CoCrPt Alloy Thin Films with Perpendicular Magnetic Anisotropy

    NASA Astrophysics Data System (ADS)

    Mizukami, Shigemi; Watanabe, Daisuke; Kubota, Takahide; Zhang, Xianmin; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Miyazaki, Terunobu

    2010-12-01

    We have investigated magnetic field strength (up to 10 kOe) and angle dependences of spin dynamics in 4-nm-thick films of CoCrPt alloys with perpendicular magnetic anisotropy using the all-optical time-resolved magneto-optical Kerr effect (TRMOKE). The comprehensive TRMOKE measurements have indicated the Gilbert damping constant α of 0.05 for the alloy film with low coercivity. The experiments also indicated that α values for the alloy films deposited at higher temperatures with higher coercivities were also no greater than 0.06.

  16. Heating of cardiovascular stents in intense radiofrequency magnetic fields.

    PubMed

    Foster, K R; Goldberg, R; Bonsignore, C

    1999-01-01

    We consider the heating of a metal stent in an alternating magnetic field from an induction heating furnace. An approximate theoretical analysis is conducted to estimate the magnetic field strength needed to produce substantial temperature increases. Experiments of stent heating in industrial furnaces are reported, which confirm the model. The results show that magnetic fields inside inductance furnaces are capable of significantly heating stents. However, the fields fall off very quickly with distance and in most locations outside the heating coil, field levels are far too small to produce significant heating. The ANSI/IEEE C95.1-1992 limits for human exposure to alternating magnetic fields provide adequate protection against potential excessive heating of the stents. PMID:10029137

  17. Spin precession in anisotropic cosmologies

    NASA Astrophysics Data System (ADS)

    Kamenshchik, A. Yu.; Teryaev, O. V.

    2016-05-01

    We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early universe may produce the sterile particles contributing to dark matter.

  18. The Combined Effect of Precession and Convection on the Dynamo Action

    NASA Astrophysics Data System (ADS)

    Wei, Xing

    2016-08-01

    To understand the generation of the Earth’s magnetic field and those of other planets, we numerically investigate the combined effect of precession and convection on dynamo action in a spherical shell. Convection alone, precession alone, and the combined effect of convection and precession are studied at the low Ekman number at which the precessing flow is already unstable. The key result is that although precession or convection alone are not strong enough to support the dynamo action, the combined effect of precession and convection can support the dynamo action because of the resonance of precessional and convective instabilities. This result may explain why the geodynamo has been maintained for such a long time compared to the Martian dynamo.

  19. Cardiovascular magnetic resonance in rheumatology: Current status and recommendations for use.

    PubMed

    Mavrogeni, Sophie I; Kitas, George D; Dimitroulas, Theodoros; Sfikakis, Petros P; Seo, Philip; Gabriel, Sherine; Patel, Amit R; Gargani, Luna; Bombardieri, Stefano; Matucci-Cerinic, Marco; Lombardi, Massimo; Pepe, Alessia; Aletras, Anthony H; Kolovou, Genovefa; Miszalski, Tomasz; van Riel, Piet; Semb, AnneGrete; Gonzalez-Gay, Miguel Angel; Dessein, Patrick; Karpouzas, George; Puntmann, Valentina; Nagel, Eike; Bratis, Konstantinos; Karabela, Georgia; Stavropoulos, Efthymios; Katsifis, Gikas; Koutsogeorgopoulou, Loukia; van Rossum, Albert; Rademakers, Frank; Pohost, Gerald; Lima, Joao A C

    2016-08-15

    Targeted therapies in connective tissue diseases (CTDs) have led to improvements of disease-associated outcomes, but life expectancy remains lower compared to general population due to emerging co-morbidities, particularly due to excess cardiovascular risk. Cardiovascular magnetic resonance (CMR) is a noninvasive imaging technique which can provide detailed information about multiple cardiovascular pathologies without using ionizing radiation. CMR is considered the reference standard for quantitative evaluation of left and right ventricular volumes, mass and function, cardiac tissue characterization and assessment of thoracic vessels; it may also be used for the quantitative assessment of myocardial blood flow with high spatial resolution and for the evaluation of the proximal coronary arteries. These applications are of particular interest in CTDs, because of the potential of serious and variable involvement of the cardiovascular system during their course. The International Consensus Group on CMR in Rheumatology was formed in January 2012 aiming to achieve consensus among CMR and rheumatology experts in developing initial recommendations on the current state-of-the-art use of CMR in CTDs. The present report outlines the recommendations of the participating CMR and rheumatology experts with regards to: (a) indications for use of CMR in rheumatoid arthritis, the spondyloarthropathies, systemic lupus erythematosus, vasculitis of small, medium and large vessels, myositis, sarcoidosis (SRC), and scleroderma (SSc); (b) CMR protocols, terminology for reporting CMR and diagnostic CMR criteria for assessment and quantification of cardiovascular involvement in CTDs; and (c) a research agenda for the further development of this evolving field. PMID:27179903

  20. Probing for compositeness, discrete time effects and Markov enviromental influences using spin polarization precession.

    NASA Astrophysics Data System (ADS)

    Wolf, Carl

    By considering a spin-one particle precession in a magnetic field, we demonstrate that if very refined measurements were made of both the precession frequency and the amplitude of spin polarization, these measurements could be used to probe for compositeness of gauge bosons, discrete time effects and possible Markov environmental effects.

  1. Minimizing Risk of Nephrogenic systemic fibrosis in Cardiovascular Magnetic Resonance

    PubMed Central

    2012-01-01

    Nephrogenic Systemic Fibrosis is a rare condition appearing only in patients with severe renal impairment or failure and presents with dermal lesions and involvement of internal organs. Although many cases are mild, an estimated 5 % have a progressive debilitating course. To date, there is no known effective treatment thus stressing the necessity of ample prevention measures. An association with the use of Gadolinium based contrast agents (GBCA) makes Nephrogenic Systemic Fibrosis a potential side effect of contrast enhanced magnetic resonance imaging and offers the opportunity for prevention by limiting use of gadolinium based contrast agents in renal failure patients. In itself toxic, Gadolinium is embedded into chelates that allow its safe use as a contrast agent. One NSF theory is that Gadolinium chelates distribute into the extracellular fluid compartment and set Gadolinium ions free, depending on multiple factors among which the duration of chelates exposure is directly related to the renal function. Major medical societies both in Europe and in North America have developed guidelines for the usage of GBCA. Since the establishment of these guidelines and the increased general awareness of this condition, the occurrence of NSF has been nearly eliminated. Giving an overview over the current knowledge of NSF pathobiochemistry, pathogenesis and treatment options this review focuses on the guidelines of the European Medicines Agency, the European Society of Urogenital Radiology, the FDA and the American College of Radiology from 2008 up to 2011 and the transfer of this knowledge into every day practice. PMID:22607376

  2. Precession-driven dynamos in a full sphere and the role of large scale cyclonic vortices

    NASA Astrophysics Data System (ADS)

    Lin, Yufeng; Marti, Philippe; Noir, Jerome; Jackson, Andrew

    2016-06-01

    Precession has been proposed as an alternative power source for planetary dynamos. Previous hydrodynamic simulations suggested that precession can generate very complex flows in planetary liquid cores [Y. Lin, P. Marti, and J. Noir, "Shear-driven parametric instability in a precessing sphere," Phys. Fluids 27, 046601 (2015)]. In the present study, we numerically investigate the magnetohydrodynamics of a precessing sphere. We demonstrate precession driven dynamos in different flow regimes, from laminar to turbulent flows. In particular, we highlight the magnetic field generation by large scale cyclonic vortices, which has not been explored previously. In this regime, dynamos can be sustained at relatively low Ekman numbers and magnetic Prandtl numbers, which paves the way for planetary applications.

  3. Unmasking Silent Endothelial Activation in the Cardiovascular System Using Molecular Magnetic Resonance Imaging.

    PubMed

    Belliere, Julie; Martinez de Lizarrondo, Sara; Choudhury, Robin P; Quenault, Aurélien; Le Béhot, Audrey; Delage, Christine; Chauveau, Dominique; Schanstra, Joost P; Bascands, Jean-Loup; Vivien, Denis; Gauberti, Maxime

    2015-01-01

    Endothelial activation is a hallmark of cardiovascular diseases, acting either as a cause or a consequence of organ injury. To date, we lack suitable methods to measure endothelial activation in vivo. In the present study, we developed a magnetic resonance imaging (MRI) method allowing non-invasive endothelial activation mapping in the vasculature of the main organs affected during cardiovascular diseases. In clinically relevant contexts in mice (including systemic inflammation, acute and chronic kidney diseases, diabetes mellitus and normal aging), we provided evidence that this method allows detecting endothelial activation before any clinical manifestation of organ failure in the brain, kidney and heart with an exceptional sensitivity. In particular, we demonstrated that diabetes mellitus induces chronic endothelial cells activation in the kidney and heart. Moreover, aged mice presented activated endothelial cells in the kidneys and the cerebrovasculature. Interestingly, depending on the underlying condition, the temporospatial patterns of endothelial activation in the vascular beds of the cardiovascular system were different. These results demonstrate the feasibility of detecting silent endothelial activation occurring in conditions associated with high cardiovascular risk using molecular MRI. PMID:26379785

  4. Unmasking Silent Endothelial Activation in the Cardiovascular System Using Molecular Magnetic Resonance Imaging

    PubMed Central

    Belliere, Julie; Martinez de Lizarrondo, Sara; Choudhury, Robin P.; Quenault, Aurélien; Le Béhot, Audrey; Delage, Christine; Chauveau, Dominique; Schanstra, Joost P.; Bascands, Jean-Loup; Vivien, Denis; Gauberti, Maxime

    2015-01-01

    Endothelial activation is a hallmark of cardiovascular diseases, acting either as a cause or a consequence of organ injury. To date, we lack suitable methods to measure endothelial activation in vivo. In the present study, we developed a magnetic resonance imaging (MRI) method allowing non-invasive endothelial activation mapping in the vasculature of the main organs affected during cardiovascular diseases. In clinically relevant contexts in mice (including systemic inflammation, acute and chronic kidney diseases, diabetes mellitus and normal aging), we provided evidence that this method allows detecting endothelial activation before any clinical manifestation of organ failure in the brain, kidney and heart with an exceptional sensitivity. In particular, we demonstrated that diabetes mellitus induces chronic endothelial cells activation in the kidney and heart. Moreover, aged mice presented activated endothelial cells in the kidneys and the cerebrovasculature. Interestingly, depending on the underlying condition, the temporospatial patterns of endothelial activation in the vascular beds of the cardiovascular system were different. These results demonstrate the feasibility of detecting silent endothelial activation occurring in conditions associated with high cardiovascular risk using molecular MRI. PMID:26379785

  5. LVM Assessed by Echocardiography and Cardiac Magnetic Resonance, Cardiovascular Outcomes, and Medical Practice

    PubMed Central

    Armstrong, Anderson C.; Gidding, Samuel; Gjesdal, Ola; Wu, Colin; Bluemke, David A; Lima, João A.

    2012-01-01

    We investigate three important areas related to the clinical use of LVM (LVM): accuracy of assessments by echocardiography and cardiac magnetic resonance (CMR), the ability to predict cardiovascular outcomes, and the comparative value of different indexing methods. The recommended formula for echocardiographic estimation of LVM uses linear measurements and is based on the assumption of the left ventricle as a prolate ellipsoid of revolution. CMR permits a modeling of the left ventricle free of cardiac geometric assumptions or acoustic window dependency, showing better accuracy and reproducibility. However, echocardiography has lower cost, easier availability, and better tolerability. From the Medline database, 26 longitudinal echocardiographic studies and 5 CMR studies, investigating LVM or LV hypertrophy as predictors of death or major cardiovascular outcomes, were identified. LVM and LV hypertrophy were reliable cardiovascular risk predictors using both modalities. However, no study directly compared the methods for the ability to predict events, agreement in hypertrophy classification, or performance in cardiovascular risk reclassification. Indexing LVM to BSA was the earliest normalization process used, but it seems to underestimate the prevalence of hypertrophy in obese and overweight subjects. Dividing LVM by height to 1.7 or 2.7 as allometric powers are the most promising normalization methods in terms of practicality and usefulness from a clinical ans scientific standpoints for scaling myocardial mass to body size. The measurement of LVM, calculation of LVMi, and classification for LVH should be standardized by scientific societies across measurement techniques and adopted by clinicians in risk stratification and therapeutic decision. PMID:22897998

  6. Standardized cardiovascular magnetic resonance imaging (CMR) protocols, society for cardiovascular magnetic resonance: board of trustees task force on standardized protocols

    PubMed Central

    Kramer, Christopher M; Barkhausen, Jorg; Flamm, Scott D; Kim, Raymond J; Nagel, Eike

    2008-01-01

    Index 1. General techniques 1.1. Stress and safety equipment 1.2. Left ventricular (LV) structure and function module 1.3. Right ventricular (RV) structure and function module 1.4. Gadolinium dosing module. 1.5. First pass perfusion 1.6. Late gadolinium enhancement (LGE) 2. Disease specific protocols 2.1. Ischemic heart disease 2.1.1. Acute myocardial infarction (MI) 2.1.2. Chronic ischemic heart disease and viability 2.1.3. Dobutamine stress 2.1.4. Adenosine stress perfusion 2.2. Angiography: 2.2.1. Peripheral magnetic resonance angiography (MRA) 2.2.2. Thoracic MRA 2.2.3. Anomalous coronary arteries 2.2.4. Pulmonary vein evaluation 2.3. Other 2.3.1. Non-ischemic cardiomyopathy 2.3.2. Arrhythmogenic right ventricular cardiomyopathy (ARVC) 2.3.3. Congenital heart disease 2.3.4. Valvular heart disease 2.3.5. Pericardial disease 2.3.6. Masses PMID:18605997

  7. Hyperpolarized Magnetic Resonance: A Novel Technique for the In Vivo Assessment of Cardiovascular Disease

    PubMed Central

    Schroeder, Marie A.; Clarke, Kieran; Neubauer, Stefan; Tyler, Damian J.

    2011-01-01

    Non-invasive imaging plays a central role in cardiovascular disease for determining diagnosis, prognosis, and optimizing patient management. Recent experimental studies have demonstrated that monitoring hyperpolarized 13C-labelled tracers with magnetic resonance imaging and spectroscopy (MRI and MRS) offers a new way to investigate the normal and diseased heart, and that the technology may be useful in patients with heart disease. In this review, we show how hyperpolarized 13C-labelled tracers are generated and have been applied experimentally, and outline the methodological advances currently underway to enable translation of hyperpolarized 13C MRI and MRS into the clinic. Using hyperpolarized 13C-labelled metabolites and metabolic MRI and MRS could help assessment of many human cardiovascular diseases, including coronary artery disease, heart failure and metabolic cardiomyopathies. We discuss the clinical areas in which the technology may, in the future, aid in the diagnosis and management of patients with cardiovascular diseases, including dynamic investigations of in vivo metabolism, coronary angiography and quantitative perfusion imaging. It is possible that, in the future, hyperpolarized magnetic resonance will play a major role in clinical cardiology. PMID:21969318

  8. Cardiovascular alterations in Macaca monkeys exposed to stationary magnetic fields: experimental observations and theoretical analysis

    SciTech Connect

    Tenforde, T.S.; Gaffey, C.T.; Moyer, B.R.; Budinger, T.F.

    1983-01-01

    Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposure to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system. 27 references, 1 figure, 1 table.

  9. Cardiovascular magnetic resonance at 3.0T: Current state of the art

    PubMed Central

    2010-01-01

    There are advantages to conducting cardiovascular magnetic resonance (CMR) studies at a field strength of 3.0 Telsa, including the increase in bulk magnetization, the increase in frequency separation of off-resonance spins, and the increase in T1 of many tissues. However, there are significant challenges to routinely performing CMR at 3.0T, including the reduction in main magnetic field homogeneity, the increase in RF power deposition, and the increase in susceptibility-based artifacts. In this review, we outline the underlying physical effects that occur when imaging at higher fields, examine the practical results these effects have on the CMR applications, and examine methods used to compensate for these effects. Specifically, we will review cine imaging, MR coronary angiography, myocardial perfusion imaging, late gadolinium enhancement, and vascular wall imaging. PMID:20929538

  10. A Precession-Driven Lunar Dynamo

    NASA Astrophysics Data System (ADS)

    Tian, B. Y.; Stanley, S.; Tikoo, S. M.; Weiss, B. P.

    2014-12-01

    Paleomagnetic studies of Apollo samples suggest that the Moon generated a magnetic field with surface field intensities of several tens of microteslas until at least 3.56 billion years ago (Ga). The field then declined by an order of magnitude from 3.56 - 3.19 Ga. Because of difficulties in reproducing such a long-lived and intense field with convection-driven dynamos, a dynamo driven by precession of the mantle relative to the core was proposed as an alternative. However, there have not been any detailed numerical models demonstrating the feasibility, lifetime, and intensity of such a lunar dynamo. Using fully 3D magnetohydrodynamic simulations, we determined the strength and duration of a mechanically-driven dynamo powered by mantle precession. We found that this mechanism was capable of not only generating the 10-100μT paleomagnetic intensities observed in Apollo samples aged between 4.25 and 3.56 Ga, but also reproducing the precipitous decline in paleointensity beyond 3.56 Ga as the obliquity of the Moon decreased below 15°.

  11. Two spinning ways for precession dynamo

    NASA Astrophysics Data System (ADS)

    Cappanera, L.; Guermond, J.-L.; Léorat, J.; Nore, C.

    2016-04-01

    It is numerically demonstrated by means of a magnetohydrodynamic code that precession can trigger dynamo action in a cylindrical container. Fixing the angle between the spin and the precession axis to be 1/2 π , two limit configurations of the spinning axis are explored: either the symmetry axis of the cylinder is parallel to the spin axis (this configuration is henceforth referred to as the axial spin case), or it is perpendicular to the spin axis (this configuration is referred to as the equatorial spin case). In both cases, the centro-symmetry of the flow breaks when the kinetic Reynolds number increases. Equatorial spinning is found to be more efficient in breaking the centro-symmetry of the flow. In both cases, the average flow in the reference frame of the mantle converges to a counter-rotation with respect to the spin axis as the Reynolds number grows. We find a scaling law for the average kinetic energy in term of the Reynolds number in the axial spin case. In the equatorial spin case, the unsteady asymmetric flow is shown to be capable of sustaining dynamo action in the linear and nonlinear regimes. The magnetic field is mainly dipolar in the equatorial spin case, while it is is mainly quadrupolar in the axial spin case.

  12. Toroidal Precession as a Geometric Phase

    SciTech Connect

    J.W. Burby and H. Qin

    2012-09-26

    Toroidal precession is commonly understood as the orbit-averaged toroidal drift of guiding centers in axisymmetric and quasisymmetric configurations. We give a new, more natural description of precession as a geometric phase effect. In particular, we show that the precession angle arises as the holonomy of a guiding center's poloidal trajectory relative to a principal connection. The fact that this description is physically appropriate is borne out with new, manifestly coordinate-independent expressions for the precession angle that apply to all types of orbits in tokamaks and quasisymmetric stellarators alike. We then describe how these expressions may be fruitfully employed in numerical calculations of precession.

  13. The Precession of Asteroid 1620 Geographos

    NASA Astrophysics Data System (ADS)

    Prokof'eva, V. V.; Tarashchuk, V. P.; Karachkina, L. G.

    The frequency analysis of the fine photometric effects in the photometric observation obtained during asteroid 1620 Geographos approaching to Earth in 1994 allowed to derive the precession of asteroid spin axis. The periods of 0({rm) d!.8 and 2({rm) d!.8 or multiple to them were revealed. The magnitude of precession angle was estimated to be near 3({circ) . The nature of the precession discussed. The emergence of the free precession may be supported at time of the formation of the asteroid or by the collision with another body. The forced precession does not contradict to the Geographos connection with meteor streams and the assumption that Geographos may have small satellites.

  14. Identification of Left Ventricular Myocardial Ischemia and Cardiac Prognosis with Cardiovascular Magnetic Resonance: Updates from 2008 to 2010

    PubMed Central

    Chotenimitkhun, Runyawan

    2013-01-01

    Noninvasive imaging modalities are often used to manage patients with cardiovascular disease. Cardiovascular magnetic resonance (CMR) is increasingly used for diagnosing and evaluating myocardial ischemia and viability; moreover, stress CMR study results can be used to determine cardiac prognosis. In this article, we review recently published material regarding the performance of stress testing with CMR including a brief update regarding techniques, stress agents, diagnostic accuracy, prognosis, economic implications, and ongoing trials and future developments. PMID:21125353

  15. Extra-cardiac findings in cardiovascular magnetic resonance: what the imaging cardiologist needs to know.

    PubMed

    Rodrigues, Jonathan C L; Lyen, Stephen M; Loughborough, William; Amadu, Antonio Matteo; Baritussio, Anna; Dastidar, Amardeep Ghosh; Manghat, Nathan E; Bucciarelli-Ducci, Chiara

    2016-01-01

    Cardiovascular magnetic resonance (CMR) is an established non-invasive technique to comprehensively assess cardiovascular structure and function in a variety of acquired and inherited cardiac conditions. A significant amount of the neck, thorax and upper abdomen are imaged at the time of routine clinical CMR, particularly in the initial multi-slice axial and coronal images. The discovery of unsuspected disease at the time of imaging has ethical, financial and medico-legal implications. Extra-cardiac findings at the time of CMR are common, can be important and can change clinical management. Certain patient groups undergoing CMR are at particular risk of important extra-cardiac findings as several of the cardiovascular risk factors for atherosclerosis are also risk factors for malignancy. Furthermore, the presence of certain extra-cardiac findings may contribute to the interpretation of the primary cardiac pathology as some cardiac conditions have multi-systemic extra-cardiac involvement. The aim of this review is to give an overview of the type of extra-cardiac findings that may become apparent on CMR, subdivided by anatomical location. We focus on normal variant anatomy that may mimic disease, common incidental extra-cardiac findings and important imaging signs that help distinguish sinister pathology from benign disease. We also aim to provide a framework to the approach and potential further diagnostic work-up of incidental extra-cardiac findings discovered at the time of CMR. However, it is beyond the scope of this review to discuss and determine the clinical significance of extracardiac findings at CMR. PMID:27156861

  16. Consistency of aortic distensibility and pulse wave velocity estimates with respect to the Bramwell-Hill theoretical model: a cardiovascular magnetic resonance study

    PubMed Central

    2011-01-01

    Background Arterial stiffness is considered as an independent predictor of cardiovascular mortality, and is increasingly used in clinical practice. This study aimed at evaluating the consistency of the automated estimation of regional and local aortic stiffness indices from cardiovascular magnetic resonance (CMR) data. Results Forty-six healthy subjects underwent carotid-femoral pulse wave velocity measurements (CF_PWV) by applanation tonometry and CMR with steady-state free-precession and phase contrast acquisitions at the level of the aortic arch. These data were used for the automated evaluation of the aortic arch pulse wave velocity (Arch_PWV), and the ascending aorta distensibility (AA_Distc, AA_Distb), which were estimated from ascending aorta strain (AA_Strain) combined with either carotid or brachial pulse pressure. The local ascending aorta pulse wave velocity AA_PWVc and AA_PWVb were estimated respectively from these carotid and brachial derived distensibility indices according to the Bramwell-Hill theoretical model, and were compared with the Arch_PWV. In addition, a reproducibility analysis of AA_PWV measurement and its comparison with the standard CF_PWV was performed. Characterization according to the Bramwell-Hill equation resulted in good correlations between Arch_PWV and both local distensibility indices AA_Distc (r = 0.71, p < 0.001) and AA_Distb (r = 0.60, p < 0.001); and between Arch_PWV and both theoretical local indices AA_PWVc (r = 0.78, p < 0.001) and AA_PWVb (r = 0.78, p < 0.001). Furthermore, the Arch_PWV was well related to CF_PWV (r = 0.69, p < 0.001) and its estimation was highly reproducible (inter-operator variability: 7.1%). Conclusions The present work confirmed the consistency and robustness of the regional index Arch_PWV and the local indices AA_Distc and AA_Distb according to the theoretical model, as well as to the well established measurement of CF_PWV, demonstrating the relevance of the regional and local CMR indices. PMID

  17. Long term effects of cocaine on the heart assessed by cardiovascular magnetic resonance at 3T

    PubMed Central

    2014-01-01

    Background Cocaine is an addictive, sympathomimetic drug with potentially lethal effects. The prevalence and features of cocaine cardiotoxicity are not well known. We aimed to assess these effects using a comprehensive cardiovascular magnetic resonance (CMR) protocol in a large group of asymptomatic cocaine users. Methods Consecutive (n = 94, 81 males, 36.6 ±7 years), non-selected, cocaine abusers were recruited and had a medical history, examination, ECG, blood test and CMR. The CMR study included measurement of left and right ventricular (LV, RV) dimensions and ejection fraction (EF), sequences for detection of myocardial oedema and late gadolinium enhancement (LGE). Images were compared to a cohort of healthy controls. Results Years of regular cocaine use were 13.9 ± 9. When compared to the age-matched healthy cohort, the cocaine abusers had increased LV end-systolic volume, LV mass index and RV end-systolic volume, with decreased LVEF and RVEF. No subject had myocardial oedema, but 30% had myocardial LGE indicating myocardial damage. Conclusions CMR detected cardiovascular disease in 71% of this cohort of consecutive asymptomatic cocaine abusers and mean duration of abuse was related to probability of LV systolic dysfunction. PMID:24758161

  18. Role of cardiovascular magnetic resonance in assessment of acute coronary syndrome

    PubMed Central

    Azarisman, Shah M; Teo, Karen S; Worthley, Matthew I; Worthley, Stephen G

    2014-01-01

    Cardiovascular disease (CVD) is the leading cause of death in the western world and is becoming more important in the developing world. Recently, advances in monitoring, revascularisation and pharmacotherapy have resulted in a reduction in mortality. However, although mortality rates have declined, the burden of disease remains large resulting in high direct and indirect healthcare costs related to CVDs. In Australia, acute coronary syndrome (ACS) accounts for more than 300000 years of life lost due to premature death and a total cost exceeding eight billion dollars annually. It is also the main contributor towards the discrepancy in life expectancy between indigenous and non-indigenous Australians. The high prevalence of CVD along with its associated cost urgently requires a reliable but non-invasive and cost-effective imaging modality. The imaging modality of choice should be able to accelerate the diagnosis of ACS, aid in the risk stratification of de novo coronary artery disease and avail incremental information of prognostic value such as viability which cardiovascular magnetic resonance (CMR) allows. Despite its manifold benefits, there are limitations to its wider use in routine clinical assessment and more studies are required into assessing its cost-effectiveness. It is hoped that with greater development in the technology and imaging protocols, CMR could be made less cumbersome, its imaging protocols less lengthy, the technology more inexpensive and easily applied in routine clinical practice. PMID:24976912

  19. Alterations in vascular function in primary aldosteronism: a cardiovascular magnetic resonance imaging study.

    PubMed

    Mark, P B; Boyle, S; Zimmerli, L U; McQuarrie, E P; Delles, C; Freel, E M

    2014-02-01

    Excess aldosterone is associated with increased cardiovascular risk. Aldosterone has a permissive effect on vascular fibrosis. Cardiovascular magnetic resonance imaging (CMR) allows study of vascular function by measuring aortic distensibility. We compared aortic distensibility in primary aldosteronism (PA), essential hypertension (EH) and normal controls and explored the relationship between aortic distensibility and pulse wave velocity (PWV). We studied PA (n=14) and EH (n=33) subjects and age-matched healthy controls (n=17) with CMR, including measurement of aortic distensibility, and measured PWV using applanation tonometry. At recruitment, PA and EH patients had similar blood pressure and left ventricular mass. Subjects with PA had significantly lower aortic distensibility and higher PWV compared with EH and healthy controls. These changes were independent of other factors associated with reduced aortic distensibility, including ageing. There was a significant relationship between increasing aortic stiffness and age in keeping with physical and vascular ageing. As expected, aortic distensibility and PWV were closely correlated. These results demonstrate that PA patients display increased arterial stiffness compared with EH, independent of vascular ageing. The implication is that aldosterone invokes functional impairment of arterial function. The long-term implications of arterial stiffening in aldosterone excess require further study. PMID:23884211

  20. Quantification of cardiovascular disease biomarkers via functionalized magnetic beads and on-demand detachable quantum dots

    NASA Astrophysics Data System (ADS)

    Park, Hoyoung; Lee, Jong-Wook; Hwang, Mintai P.; Lee, Kwan Hyi

    2013-08-01

    Cardiovascular disease (CVD) is a potent cause of mortality in both advanced and developing countries. While soluble CD40L (sCD40L) has been implicated as a correlative factor among CVD patients, methods to quantify sCD40L are not yet well-established. In this paper, we present an ability to separate and quantify sCD40L via a simple immunomagnetic assay. Composed of functionalized magnetic beads conferred with directionality and on-demand detachable quantum dots for subsequent optical analysis, our system utilizes the competitive nature of imidazole and nickel ions for histidine. In essence, we demonstrate the capacity to effectively separate and detect sCD40L within a clinically relevant range that contains the cut-off value for acute coronary disease. While sCD40L was used to conduct this study, we envision the use of our system for the separation and quantification of other biomarkers.

  1. Quantification of cardiovascular disease biomarkers via functionalized magnetic beads and on-demand detachable quantum dots.

    PubMed

    Park, Hoyoung; Lee, Jong-Wook; Hwang, Mintai P; Lee, Kwan Hyi

    2013-09-21

    Cardiovascular disease (CVD) is a potent cause of mortality in both advanced and developing countries. While soluble CD40L (sCD40L) has been implicated as a correlative factor among CVD patients, methods to quantify sCD40L are not yet well-established. In this paper, we present an ability to separate and quantify sCD40L via a simple immunomagnetic assay. Composed of functionalized magnetic beads conferred with directionality and on-demand detachable quantum dots for subsequent optical analysis, our system utilizes the competitive nature of imidazole and nickel ions for histidine. In essence, we demonstrate the capacity to effectively separate and detect sCD40L within a clinically relevant range that contains the cut-off value for acute coronary disease. While sCD40L was used to conduct this study, we envision the use of our system for the separation and quantification of other biomarkers. PMID:23893124

  2. Diagnostic and prognostic value of cardiovascular magnetic resonance in non-ischaemic cardiomyopathies

    PubMed Central

    2012-01-01

    Cardiovascular Magnetic Resonance (CMR) is recognised as a valuable clinical tool which in a single scan setting can assess ventricular volumes and function, myocardial fibrosis, iron loading, flow quantification, tissue characterisation and myocardial perfusion imaging. The advent of CMR using extrinsic and intrinsic contrast-enhanced protocols for tissue characterisation have dramatically changed the non-invasive work-up of patients with suspected or known cardiomyopathy. Although the technique initially focused on the in vivo identification of myocardial necrosis through the late gadolinium enhancement (LGE) technique, recent work highlighted the ability of CMR to provide more detailed in vivo tissue characterisation to help establish a differential diagnosis of the underlying aetiology, to exclude an ischaemic substrate and to provide important prognostic markers. The potential application of CMR in the clinical approach of a patient with suspected non-ischaemic cardiomyopathy is discussed in this review. PMID:22857649

  3. Remote magnetic targeting of iron oxide nanoparticles for cardiovascular diagnosis and therapeutic drug delivery: where are we now?

    PubMed Central

    Bietenbeck, Michael; Florian, Anca; Faber, Cornelius; Sechtem, Udo; Yilmaz, Ali

    2016-01-01

    Magnetic resonance imaging (MRI) allows for an accurate assessment of both functional and structural cardiac parameters, and thereby appropriate diagnosis and validation of cardiovascular diseases. The diagnostic yield of cardiovascular MRI examinations is often increased by the use of contrast agents that are almost exclusively based on gadolinium compounds. Another clinically approved contrast medium is composed of superparamagnetic iron oxide nanoparticles (IONs). These particles may expand the field of contrast-enhanced cardiovascular MRI as recently shown in clinical studies focusing on acute myocardial infarction (AMI) and atherosclerosis. Furthermore, IONs open up new research opportunities such as remote magnetic drug targeting (MDT). The approach of MDT relies on the coupling of bioactive molecules and magnetic nanoparticles to form an injectable complex. This complex, in turn, can be attracted to and retained at a desired target inside the body with the help of applied magnetic fields. In comparison to common systemic drug applications, MDT techniques promise both higher concentrations at the target site and lower concentrations elsewhere in the body. Moreover, concurrent or subsequent MRI can be used for noninvasive monitoring of drug distribution and successful delivery to the desired organ in vivo. This review does not only illustrate the basic conceptual and biophysical principles of IONs, but also focuses on new research activities and achievements in the cardiovascular field, mainly in the management of AMI. Based on the presentation of successful MDT applications in preclinical models of AMI, novel approaches and the translational potential of MDT are discussed. PMID:27486321

  4. Determining phase relations of proxy data using the eccentricity-precession pattern

    NASA Astrophysics Data System (ADS)

    Zeeden, C.; Rivera, T. A.

    2012-04-01

    The phase relation between proxy data and orbital forcing is not always obvious; a link to both precession/insolation maxima or -minima can often be reasoned for. We present a novel approach to extract the phase relation using solely eccentricity-precession pattern from high quality proxy data. We determine the position of consecutive eccentricity maxima as precisely as possible from a stratigraphic record using both eccentricity filters and the amplitude modulation of precession. This way we obtain both the position of these eccentricity maxima as well as the sedimentation rate between successive maxima with error margins. Combining these results with the precession pattern in the geological record, we can determine whether precession-related patterns relate to precession (or insolation) minima or maxima. This approach relies on high quality geological data, the assumption of a direct eccentricity and precession response to orbital forcing, and a well defined orbital solution, but avoids the assumption of an instantaneous response to obliquity. For data with filtered components showing a good fit with the proxy data, this approach yields good results. Using high quality proxy data (color, magnetic susceptibility), we are able to determine the phase relation for equatorial Atlantic Miocene successions of ODP Leg 154. The research leading to these results has received funding from the [European Community's] Seventh Framework Programme ([FP7/2007-2013] under grant agreement n° [215458]. This research used data provided by IODP. Funding for this research was provided by NWO.

  5. Non-Mathematical Explanation of Precession

    ERIC Educational Resources Information Center

    Cordell, John

    2011-01-01

    The phenomenon of precession is necessary to explain the motion of footballs, gyroscopes, tops, the Earth, and many other interesting physical systems, but it was very hard for me to understand as a student and is very difficult to teach to students now. Many explanations of precession in physics textbooks are highly mathematical and hard to…

  6. Cardiovascular magnetic resonance imaging of isolated perfused pig hearts in a 3T clinical MR scanner

    PubMed Central

    Chiribiri, Amedeo; Ishida, Masaki; Morton, Geraint; Paul, Matthias; Hussain, Shazia T.; Bigalke, Boris; Perera, Divaka; Schaeffter, Tobias; Nagel, Eike

    2012-01-01

    Purpose An isolated perfused pig heart model has recently been proposed for the development of novel methods in standard clinical magnetic resonance (MR) scanners. The original set-up required the electrical system to be within the safe part of the MR-room, which introduced significant background noise. The purpose of the current work was to refine the system to overcome this limitation so that all electrical parts are completely outside the scanner room. Methods Four pig hearts were explanted under terminal anaesthesia from large white cross landrace pigs. All hearts underwent cardiovascular magnetic resonance (CMR) scanning in the MR part of a novel combined 3T MR and x-ray fluoroscopy (XMR) suite. CMR scanning included real-time k-t SENSE functional imaging, k-t SENSE accelerated perfusion imaging and late gadolinium enhancement imaging. Interference with image quality was assessed by spurious echo imaging and compared to noise levels acquired while operating the electrical parts within the scanner room. Results Imaging was performed successfully in all hearts. The system proved suitable for isolated heart perfusion in a novel 3T XMR suite. No significant additional noise was introduced into the scanner room by our set-up. Conclusions We have substantially improved a previous version of an isolated perfused pig heart model and made it applicable for MR imaging in a state of the art clinical 3T XMR imaging suite. The use of this system should aid novel CMR sequence development and translation into clinical practice. PMID:24265875

  7. Myocardial edema imaging by cardiovascular magnetic resonance: current status and future potential.

    PubMed

    Carbone, Iacopo; Friedrich, Matthias G

    2012-02-01

    Cardiovascular magnetic resonance (CMR) imaging is widely established, free of radioactive material or ionizing radiation, and the accepted noninvasive gold standard for numerous noninvasive cardiac markers. Using a technique called T2-weighted imaging, CMR can be used to assess myocardial edema as a reliable marker for acute, potentially reversible myocardial injury. Contrast agents are not required as the myocardial free water content affects the magnetic properties of the tissue, thus providing inherent image contrast. In this review, we illustrate the utility of T2-weighted techniques in the assessment of myocardial edema in a range of clinical scenarios. The detection of myocardial edema is clinically relevant in many acute settings and may be further helpful to better understand the pathophysiology of many non-acute clinical diseases. Currently, T2-weighted CMR represents the only imaging modality that can accurately depict and quantify the presence of myocardial edema in a noninvasive fashion. Thus, T2-weighted imaging should be included in a comprehensive CMR imaging protocol, especially if an acute injury is suspected. PMID:22139527

  8. Early diagnosis and follow-up of chronic active Epstein–Barr-virus-associated cardiovascular complications with cardiovascular magnetic resonance imaging

    PubMed Central

    Jiang, Shu; Li, Xiao; Cao, Jian; Wu, Di; Kong, Lingyan; Lin, Lu; Jin, Zhengyu; An, Jing; Wang, Yining

    2016-01-01

    Abstract Introduction: Chronic active Epstein–Barr virus (EBV) infection (CAEBV) is characterized as chronic or recurrent mononucleosis-like symptoms and elevated EBV deoxyribonucleic acid (EBV-DNA) copies. Cardiovascular complications have high morbidity and mortality. The treatment regimen for CAEBV has not been established yet, resulting in poor prognoses. Herein, we present a case of cardiovascular magnetic resonance imaging (CMRI) evaluation with a series of sequences for CAEBV-associated cardiovascular involvement, which has never been reported. Case presentation: A 16-year-old female (body weight, 55 kg) developed a persistent fever and a positive EBV-DNA level of 28,000 copies/mL. Computed tomography angiography (CTA) showed aneurysms involving the aorta and its major branches, as well as multiple aneurysms and stenoses of the coronary arteries. CMRI of the coronary arteries depicted the dilution and stenosis of the arterial lumen as well as the thickening of the arterial wall. Late gadolinium enhancement (LGE) showed subendocardial and transmural delayed enhancement of the left ventricle, suggesting myocardial infarction. CAEBV and associated cardiovascular complications were diagnosed. After treatment with Medrol and Leflunomide, the clinical manifestation and serological parameters reversed to normal. However, the EBV-DNA level increased again to 13,900 copies/mL 2 months later. A follow-up with aorta CTA showed that the arterial walls of the bilateral common iliac artery aneurysms were thicker with new-onset mural thrombi. The aorta CTA also showed new-onset occlusion of the right coronary artery, but a follow-up of CMRI at the same day did not find new-onset delayed enhancement lesion. Conclusion: This case reminds clinicians of the vital importance of early diagnosis and close follow-up of CAEBV-associated cardiovascular complications. With cine imaging, coronary artery imaging, LGE imaging, and other novel techniques, CMRI can effectively and

  9. Nonlinear dynamo action in a precessing cylindrical container.

    PubMed

    Nore, C; Léorat, J; Guermond, J-L; Luddens, F

    2011-07-01

    It is numerically demonstrated by means of a magnetohydrodynamics code that precession can trigger the dynamo effect in a cylindrical container. When the Reynolds number, based on the radius of the cylinder and its angular velocity, increases, the flow, which is initially centrosymmetric, loses its stability and bifurcates to a quasiperiodic motion. This unsteady and asymmetric flow is shown to be capable of sustaining dynamo action in the linear and nonlinear regimes. The magnetic field thus generated is unsteady and quadrupolar. These numerical evidences of dynamo action in a precessing cylindrical container may be useful for an experiment now planned at the Dresden sodium facility for dynamo and thermohydraulic studies in Germany. PMID:21867314

  10. Insolation and the Precession Index

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2000-01-01

    Simple nonlinear climate models yield a precession index-like term in the temperature. Despite its importance in the geologic record, the precession index e sin omega, where e is the Earth's orbital eccentricity and omega is the Sun's perigee in the geocentric frame, is not present in the insolation at the top of the atmosphere. Hence there is no one-for-one mapping of 23,000 and 19,000 year periodicities from the insolation to the paleoclimate record; a nonlinear climate model is needed to produce these periods. Two such models, a grey body and an energy balance climate model with an added quadratic term, produce e sin omega terms in temperature. These terms, which without feedback mechanisms achieve extreme values of about plus or minus 0.48 K for the grey body and plus or minus 0.64 K for the energy balance model, simultaneously cool one hemisphere while they warm the other. Moreover, they produce long-term cooling in the northern hemisphere when the Sun's perigee is near northern solstice and long-term warming in the northern hemisphere when the perigee is near southern solstice. Thus this seemingly paradoxical mechanism works against the standard model which requires cool northern summers (Sun far from Earth in northern summer) to build up northern ice sheets, so that if the standard model is correct it may be more efficient than previously thought. Alternatively, the new mechanism could possibly be dominant and indicate southern hemisphere control of the northern ice sheets, wherein the southern oceans undergo a long-term cooling when the Sun is close to the Earth during southern summer. The cold water eventually flows north, cooling the northern hemisphere. This might explain why the northern oceans lag the southern ones when it comes to orbital forcing.

  11. Prognostic Value of Late Gadolinium Enhancement Cardiovascular Magnetic Resonance in Cardiac Amyloidosis

    PubMed Central

    Fontana, Marianna; Pica, Silvia; Reant, Patricia; Abdel-Gadir, Amna; Treibel, Thomas A.; Banypersad, Sanjay M.; Maestrini, Viviana; Barcella, William; Rosmini, Stefania; Bulluck, Heerajnarain; Sayed, Rabya H.; Patel, Ketna; Mamhood, Shameem; Bucciarelli-Ducci, Chiara; Whelan, Carol J.; Herrey, Anna S.; Lachmann, Helen J.; Wechalekar, Ashutosh D.; Manisty, Charlotte H.; Schelbert, Eric B.; Kellman, Peter; Gillmore, Julian D.; Hawkins, Philip N.

    2015-01-01

    Background— The prognosis and treatment of the 2 main types of cardiac amyloidosis, immunoglobulin light chain (AL) and transthyretin (ATTR) amyloidosis, are substantially influenced by cardiac involvement. Cardiovascular magnetic resonance with late gadolinium enhancement (LGE) is a reference standard for the diagnosis of cardiac amyloidosis, but its potential for stratifying risk is unknown. Methods and Results— Two hundred fifty prospectively recruited subjects, 122 patients with ATTR amyloid, 9 asymptomatic mutation carriers, and 119 patients with AL amyloidosis, underwent LGE cardiovascular magnetic resonance. Subjects were followed up for a mean of 24±13 months. LGE was performed with phase-sensitive inversion recovery (PSIR) and without (magnitude only). These were compared with extracellular volume measured with T1 mapping. PSIR was superior to magnitude-only inversion recovery LGE because PSIR always nulled the tissue (blood or myocardium) with the longest T1 (least gadolinium). LGE was classified into 3 patterns: none, subendocardial, and transmural, which were associated with increasing amyloid burden as defined by extracellular volume (P<0.0001), with transitions from none to subendocardial LGE at an extracellular volume of 0.40 to 0.43 (AL) and 0.39 to 0.40 (ATTR) and to transmural at 0.48 to 0.55 (AL) and 0.47 to 0.59 (ATTR). Sixty-seven patients (27%) died. Transmural LGE predicted death (hazard ratio, 5.4; 95% confidence interval, 2.1–13.7; P<0.0001) and remained independent after adjustment for N-terminal pro-brain natriuretic peptide, ejection fraction, stroke volume index, E/E′, and left ventricular mass index (hazard ratio, 4.1; 95% confidence interval, 1.3–13.1; P<0.05). Conclusions— There is a continuum of cardiac involvement in systemic AL and ATTR amyloidosis. Transmural LGE is determined reliably by PSIR and represents advanced cardiac amyloidosis. The PSIR technique provides incremental information on outcome even after

  12. Disease-specific cardiovascular positron emission tomography/magnetic resonance imaging: a brief review of the current literature

    PubMed Central

    Zheng, Jie

    2016-01-01

    The hybrid positron emission tomography/magnetic resonance (PET/MR) is a new imaging tool that has garnered immense research interest for its potentials to assist clinical investigations. PET/MR combines the quantitative measurement of PET with dynamic functional and anatomic assessment of MR and can deliver a robust clinical examination. Currently, simultaneous cardiovascular PET/MR imaging remains in the pre-clinical research stage, and most institutions have not adopted a clinical PET/MR clinical imaging service. Nevertheless, PET/MR examination has unique promises in several areas of cardiovascular medicine, and in recent years more and more research publications have become available to lend us insight into its utility in cardiovascular imaging. Here we review the existing literature on simultaneous cardiovascular PET/MR imaging, with an emphasis on organizing the current literature into disease-specific discussions. These areas include coronary artery disease (CAD), carotid atherosclerosis, various infiltrative, inflammatory and hereditary heart diseases, myocarditis, vasculitis, and cardiac mass assessment. The purpose of this review is to provide an overview of the current understanding of cardiovascular PET/MR clinical imaging, in a disease-specific manner, from a clinician’s perspective. Potential limitations of simultaneous PET/MR, such as cost effectiveness, artifacts, contraindications, and radiation exposure, are briefly discussed. PMID:27429913

  13. Torque-induced precession of bacterial flagella.

    PubMed

    Shimogonya, Yuji; Sawano, Yoichiro; Wakebe, Hiromichi; Inoue, Yuichi; Ishijima, Akihiko; Ishikawa, Takuji

    2015-01-01

    The bacterial flagellar motor is an ion-driven rotary machine in the cell envelope of bacteria. Using a gold nanoparticle as a probe, we observed the precession of flagella during rotation. Since the mechanism of flagella precession was unknown, we investigated it using a combination of full simulations, theory, and experiments. The results show that the mechanism can be well explained by fluid mechanics. The validity of our theory was confirmed by our full simulation, which was utilized to predict both the filament tilt angle and motor torque from experimental flagellar precession data. The knowledge obtained is important in understanding mechanical properties of the bacterial motor and hook. PMID:26691402

  14. Advancing Cardiovascular, Neurovascular, and Renal Magnetic Resonance Imaging in Small Rodents Using Cryogenic Radiofrequency Coil Technology

    PubMed Central

    Niendorf, Thoralf; Pohlmann, Andreas; Reimann, Henning M.; Waiczies, Helmar; Peper, Eva; Huelnhagen, Till; Seeliger, Erdmann; Schreiber, Adrian; Kettritz, Ralph; Strobel, Klaus; Ku, Min-Chi; Waiczies, Sonia

    2015-01-01

    Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR) for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF) coils in small animal MR as a means of boosting image quality (e.g., by supporting MR microscopy) and making data acquisition more efficient (e.g., by reducing measuring time); both being important constituents for thorough investigational studies on animal models of disease. This review attempts to make the (bio)medical imaging, molecular medicine, and pharmaceutical communities aware of this productive ferment and its outstanding significance for anatomical and functional MR in small rodents. The goal is to inspire a more intense interdisciplinary collaboration across the fields to further advance and progress non-invasive MR methods that ultimately support thorough (patho)physiological characterization of animal disease models. In this review, current and potential future applications for the RF coil technology in cardiovascular, neurovascular, and renal disease will be discussed. PMID:26617515

  15. Diagnosis and management of ischemic cardiomyopathy: Role of cardiovascular magnetic resonance imaging.

    PubMed

    Doesch, Christina; Papavassiliu, Theano

    2014-11-26

    Coronary artery disease (CAD) represents an important cause of mortality. Cardiovascular magnetic resonance (CMR) imaging evolved as an imaging modality that allows the assessment of myocardial function, perfusion, contractile reserve and extent of fibrosis in a single comprehensive exam. This review highlights the role of CMR in the differential diagnosis of acute chest pain by detecting the location of obstructive CAD or necrosis and identifying other conditions like stress cardiomyopathy or myocarditis that can present with acute chest pain. Besides, it underlines the prognostic implication of perfusion abnormalities in the setting of acute chest pain. Furthermore, the review addresses the role of CMR to detect significant CAD in patients with stable CAD. It elucidates the accuracy and clinical utility of CMR with respect to other imaging modalities like single-photon emission computed tomography and positron emission tomography. Besides, the prognostic value of CMR stress testing is discussed. Additionally, it summarizes the available CMR techniques to assess myocardial viability and describes algorithm to identify those patient who might profit from revascularization those who should be treated medically. Finally, future promising imaging techniques that will provide further insights into the fundamental disease processes in ischemic cardiomyopathy are discussed. PMID:25429329

  16. The Emerging Role of Cardiovascular Magnetic Resonance Imaging in the Evaluation of Metabolic Cardiomyopathies.

    PubMed

    Mavrogeni, S; Markousis-Mavrogenis, G; Markussis, V; Kolovou, G

    2015-08-01

    The aim of this review is to discuss the role of Cardiovascular Magnetic Resonance (CMR) in the diagnosis, risk stratification, and follow-up of metabolic cardiomyopathies. The classification of myocardial diseases, proposed by WHO/ISFC task force, distinguished specific cardiomyopathies, caused by metabolic disorders, into 4 types: 1) endocrine disorders, 2) storage or infiltration disorders (amyloidosis, hemochromatosis and familial storage disorders), 3) nutritional disorders (Kwashiorkor, beri-beri, obesity, and alcohol), and 4) diabetic heart. Thyroid disease, pheochromocytoma, and growth hormone excess or deficiency may contribute to usually reversible dilated cardiomyopathy. Glucogen storage diseases can be presented with myopathy, liver, and heart failure. Lysosomal storage diseases can provoke cardiac hypertrophy, mimicking hypertrophic cardiomyopathy and arrhythmias. Hereditary hemochromatosis, an inherited disorder of iron metabolism, leads to tissue iron overload in different organs, including the heart. Cardiac amyloidosis is the result of amyloid deposition in the heart, formed from breakdown of normal or abnormal proteins that leads to increased heart stiffness, restrictive cardiomyopathy, and heart failure. Finally, nutritional disturbances and metabolic diseases, such as Kwashiorkor, beri-beri, obesity, alcohol consumption, and diabetes mellitus may also lead to severe cardiac dysfunction. CMR, through its capability to reliably assess anatomy, function, inflammation, rest-stress myocardial perfusion, myocardial fibrosis, aortic distensibility, iron and/or fat deposition can serve as an excellent tool for early diagnosis of heart involvement, risk stratification, treatment evaluation, and long term follow-up of patients with metabolic cardiomyopathies. PMID:26197853

  17. Contribution of cardiovascular magnetic resonance in the evaluation of coronary arteries

    PubMed Central

    Mavrogeni, Sophie; Markousis-Mavrogenis, George; Kolovou, Genovefa

    2014-01-01

    Cardiovascular magnetic resonance (CMR) allows the nonradiating assessment of coronary arteries; to achieve better image quality cardiorespiratory artefacts should be corrected. Coronary MRA (CMRA) at the moment is indicated only for the detection of abnormal coronary origin, coronary artery ectasia and/or aneurysms (class I indication) and coronary bypass grafts (class II indication). CMRA utilisation for coronary artery disease is not yet part of clinical routine. However, the lack of radiation is of special value for the coronary artery evaluation in children and women. CMRA can assess the proximal part of coronary arteries in almost all cases. The best results have been observed in the evaluation of the left anterior descending and the right coronary artery, while the left circumflex, which is located far away from the coil elements, is frequently imaged with reduced quality, compared to the other two. Different studies detected an increase in wall thickness of the coronaries in patients with type I diabetes and abnormal renal function. Additionally, the non-contrast enhanced T1-weighed images detected the presence of thrombus in acute myocardial infarction. New techniques using delayed gadolinium enhanced imaging promise the direct visualization of inflamed plaques in the coronary arteries. The major advantage of CMR is the potential of an integrated protocol offering assessment of coronary artery anatomy, cardiac function, inflammation and stress perfusion-fibrosis in the same study, providing an individualized clinical profile of patients with heart disease. PMID:25349650

  18. Assessment of Left Ventricular Structural Remodelling in Patients with Diabetic Cardiomyopathy by Cardiovascular Magnetic Resonance.

    PubMed

    Shang, Yongning; Zhang, Xiaochun; Chen, Liu; Leng, Weiling; Lei, Xiaotian; Yang, Qi; Liang, Ziwen; Wang, Jian

    2016-01-01

    Background. Diabetic cardiomyopathy (DCM) is always accompanied with alteration of left ventricular structure and function. The aims of this study were to assess the structural remodelling in patients with DCM by cardiovascular magnetic resonance (CMR) and correlation of structural remodelling with severity of DCM. Methods. Twenty-five patients (53.8 ± 8.8 years, 52.0% males) with DCM and thirty-one normal healthy controls (51.9 ± 13.6 years, 45.2% males) were scanned by CMR cine to assess function and structure of left ventricular. Length of diabetic history and results of cardiac echocardiography (E', A', and E'/A') were also measured. Results. Compared with normal controls group, DCM group was associated with significantly increased ratio of left ventricular mass at end diastole to end-diastolic volume (MVR) (P < 0.05) and no significant difference was in mass at end diastole (P > 0.05). The ratio correlated with both length of diabetic history and echocardiographic Doppler tissue imaging E' (all P < 0.05). Conclusions. CMR can be a powerful technique to assess LV remodelling, and MVR may be considered as an imaging marker to evaluate the severity of LV remodelling in patients with DCM. PMID:27419144

  19. Assessment of Left Ventricular Structural Remodelling in Patients with Diabetic Cardiomyopathy by Cardiovascular Magnetic Resonance

    PubMed Central

    Zhang, Xiaochun; Leng, Weiling

    2016-01-01

    Background. Diabetic cardiomyopathy (DCM) is always accompanied with alteration of left ventricular structure and function. The aims of this study were to assess the structural remodelling in patients with DCM by cardiovascular magnetic resonance (CMR) and correlation of structural remodelling with severity of DCM. Methods. Twenty-five patients (53.8 ± 8.8 years, 52.0% males) with DCM and thirty-one normal healthy controls (51.9 ± 13.6 years, 45.2% males) were scanned by CMR cine to assess function and structure of left ventricular. Length of diabetic history and results of cardiac echocardiography (E′, A′, and E′/A′) were also measured. Results. Compared with normal controls group, DCM group was associated with significantly increased ratio of left ventricular mass at end diastole to end-diastolic volume (MVR) (P < 0.05) and no significant difference was in mass at end diastole (P > 0.05). The ratio correlated with both length of diabetic history and echocardiographic Doppler tissue imaging E′ (all P < 0.05). Conclusions. CMR can be a powerful technique to assess LV remodelling, and MVR may be considered as an imaging marker to evaluate the severity of LV remodelling in patients with DCM. PMID:27419144

  20. Late gadolinium enhanced cardiovascular magnetic resonance of lamin A/C gene mutation related dilated cardiomyopathy

    PubMed Central

    2011-01-01

    Background The purpose of this study was to identify early features of lamin A/C gene mutation related dilated cardiomyopathy (DCM) with cardiovascular magnetic resonance (CMR). We characterise myocardial and functional findings in carriers of lamin A/C mutation to facilitate the recognition of these patients using this method. We also investigated the connection between myocardial fibrosis and conduction abnormalities. Methods Seventeen lamin A/C mutation carriers underwent CMR. Late gadolinium enhancement (LGE) and cine images were performed to evaluate myocardial fibrosis, regional wall motion, longitudinal myocardial function, global function and volumetry of both ventricles. The location, pattern and extent of enhancement in the left ventricle (LV) myocardium were visually estimated. Results Patients had LV myocardial fibrosis in 88% of cases. Segmental wall motion abnormalities correlated strongly with the degree of enhancement. Myocardial enhancement was associated with conduction abnormalities. Sixty-nine percent of our asymptomatic or mildly symptomatic patients showed mild ventricular dilatation, systolic failure or both in global ventricular analysis. Decreased longitudinal systolic LV function was observed in 53% of patients. Conclusions Cardiac conduction abnormalities, mildly dilated LV and depressed systolic dysfunction are common in DCM caused by a lamin A/C gene mutation. However, other cardiac diseases may produce similar symptoms. CMR is an accurate tool to determine the typical cardiac involvement in lamin A/C cardiomyopathy and may help to initiate early treatment in this malignant familiar form of DCM. PMID:21689390

  1. Trapped Electron Precession Shear Induced Fluctuation Decorrelation

    SciTech Connect

    T.S. Hahm; P.H. Diamond; E.-J. Kim

    2002-07-29

    We consider the effects of trapped electron precession shear on the microturbulence. In a similar way the strong E x B shear reduces the radial correlation length of ambient fluctuations, the radial variation of the trapped electron precession frequency can reduce the radial correlation length of fluctuations associated with trapped electrons. In reversed shear plasmas, with the explicit dependence of the trapped electron precession shearing rate on B(subscript)theta, the sharp radial gradient of T(subscript)e due to local electron heating inside qmin can make the precession shearing mechanism more effective, and reduce the electron thermal transport constructing a positive feedback loop for the T(subscript)e barrier formation.

  2. About detection of precessing circumpulsar discs

    NASA Astrophysics Data System (ADS)

    Grimani, Catia

    2016-08-01

    Detections of circumpulsar discs and planetary systems through electromagnetic observations appear quite rare. In the case of PSR 1931+24 and B0656+14, the hypothesis of a precessing disc penetrating the pulsar light cylinder is found consistent with radio and gamma observations from these stars. Disc self-occultation and precession may affect electromagnetic measurements. We investigate here under which conditions gravitational waves generated by circumpulsar disc precession may be detected by the proposed second-generation space interferometers DECI-hertz Interferometer Gravitational Wave Observatory and Big Bang Observer. The characteristics of circumpulsar detectable precessing discs are estimated as a function of distance from the Solar system. Speculations on detection rates are presented.

  3. Consistent Numerical Expressions for Precession Formulae.

    NASA Astrophysics Data System (ADS)

    Soma, M.

    The precession formulae by Lieske et al. (1977) have been used since 1984 for calculating apparent positions and reducing astrometric observations of celestial objects. These formulae are based on the IAU (1976) Astronomical Constants, some of which deviate from their recently determined values. They are also derived using the secular variations of the ecliptic pole from Newcomb's theory, which is not consistent with the recent planetary theories. Accordingly Simon et al. (1994) developed new precession formulae using the recently determined astronomical constants and also being based on the new planetary theory VSOP87. There are two differing definitions of the ecliptic: ecliptic in the inertial sense and ecliptic in the rotating sense (Standish 1981). The ecliptic given by the VSOP87 theory is that in the inertial sense, but the value for obliquity Simon et al. used is the obliquity in the rotating sense. Therefore their precession formulae has inconsistency. This paper gives corrections for consistent precession formulae.

  4. About detection of precessing circumpulsar disks

    NASA Astrophysics Data System (ADS)

    Grimani, Catia

    2016-05-01

    Detections of circumpulsar disks and planetary systems through electromagnetic observations appear quite rare. In the case of PSR 1931+24 and B0656+14, the hypothesis of a precessing disk penetrating the pulsar light cylinder is found consistent with radio and gamma observations from these stars. Disk self-occultation and precession may affect electromagnetic measurements. We investigate here under which conditions gravitational waves generated by circumpulsar disk precession may be detected by the proposed second generation space interferometers DECIGO (DECI-hertz Interferometer Gravitational Wave Observatory) and BBO (Big Bang Observer). The characteristics of circumpulsar detectable precessing disks are estimated as a function of distance from the Solar System. Speculations on detection rates are presented.

  5. On the Subjective Acceptance during Cardiovascular Magnetic Resonance Imaging at 7.0 Tesla

    PubMed Central

    Klix, Sabrina; Els, Antje; Paul, Katharina; Graessl, Andreas; Oezerdem, Celal; Weinberger, Oliver; Winter, Lukas; Thalhammer, Christof; Huelnhagen, Till; Rieger, Jan; Mehling, Heidrun; Schulz-Menger, Jeanette; Niendorf, Thoralf

    2015-01-01

    Purpose This study examines the subjective acceptance during UHF-CMR in a cohort of healthy volunteers who underwent a cardiac MR examination at 7.0T. Methods Within a period of two-and-a-half years (January 2012 to June 2014) a total of 165 healthy volunteers (41 female, 124 male) without any known history of cardiac disease underwent UHF-CMR. For the assessment of the subjective acceptance a questionnaire was used to examine the participants experience prior, during and after the UHF-CMR examination. For this purpose, subjects were asked to respond to the questionnaire in an exit interview held immediately after the completion of the UHF-CMR examination under supervision of a study nurse to ensure accurate understanding of the questions. All questions were answered with “yes” or “no” including space for additional comments. Results Transient muscular contraction was documented in 12.7% of the questionnaires. Muscular contraction was reported to occur only during periods of scanning with the magnetic field gradients being rapidly switched. Dizziness during the study was reported by 12.7% of the subjects. Taste of metal was reported by 10.1% of the study population. Light flashes were reported by 3.6% of the entire cohort. 13% of the subjects reported side effects/observations which were not explicitly listed in the questionnaire but covered by the question about other side effects. No severe side effects as vomiting or syncope after scanning occurred. No increase in heart rate was observed during the UHF-CMR exam versus the baseline clinical examination. Conclusions This study adds to the literature by detailing the subjective acceptance of cardiovascular magnetic resonance imaging examinations at a magnetic field strength of 7.0T. Cardiac MR examinations at 7.0T are well tolerated by healthy subjects. Broader observational and multi-center studies including patient cohorts with cardiac diseases are required to gain further insights into the subjective

  6. Myocardial tagging by Cardiovascular Magnetic Resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications

    PubMed Central

    2011-01-01

    Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this

  7. Improvement of the IAU 2000 precession model

    NASA Astrophysics Data System (ADS)

    Capitaine, N.; Wallace, P. T.; Chapront, J.

    2005-03-01

    The IAU 2000 precession consists of the IAU 1976 ecliptic precession (Lieske et al. [CITE], A&A, 58, 1) and the precession part of the IAU 2000A equator adopted by IAU 2000 Resolution B1.6 (Mathews et al. [CITE], J. Geophys. Res., 107, B4, 10.1029/2001JB000390). In this paper we provide a range of new expressions as possible replacements for the IAU 2000 precession. The new expressions are based upon the so-called P03 solution of Capitaine et al. ([CITE], A&A, 412, 567) for the equator and the ecliptic. In addition an improved model for the precession of the equator is discussed. This improved solution was obtained in exactly the same way as P03 but using a refined model for the contributions of the non-rigid Earth (Mathews [CITE], private communication) and revised integration constants for the precession rates resulting from fits to the most recent VLBI data. The paper reports on the procedure that was used for improving the P03 solution and on the comparisons of this solution with the MHB 2000, IAU 2000 and P03 solutions. It also discusses the choices for the solution to be put forward as a replacement for IAU 2000. We concluded that the existing VLBI data were insufficient to provide convincing evidence that the improved solutions would deliver better accuracy than the existing P03 solution, and we recommend retaining P03 as the replacement for IAU 2000. P03, which unlike the IAU 2000 precession is dynamically consistent, has the advantage of already having been used experimentally by a number of groups; the model is recalled in Tables [see full text]- [see full text]. Due to the strong dependence of the precession expressions on the precession rates and of the precession in longitude (or equivalently the celestial CIP X coordinate) on the J2 rate model, we also provide a parameterized P04 solution for these quantities as functions of those parameters. The expressions include the quantities to be used in both the equinox-based and CIO-based (i.e. referred to

  8. Using 4D Cardiovascular Magnetic Resonance Imaging to Validate Computational Fluid Dynamics: A Case Study

    PubMed Central

    Biglino, Giovanni; Cosentino, Daria; Steeden, Jennifer A.; De Nova, Lorenzo; Castelli, Matteo; Ntsinjana, Hopewell; Pennati, Giancarlo; Taylor, Andrew M.; Schievano, Silvia

    2015-01-01

    Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta. PMID:26697416

  9. Left ventricular reverse remodeling after transcatheter aortic valve implantation: a cardiovascular magnetic resonance study

    PubMed Central

    2013-01-01

    Background In patients with severe aortic stenosis, left ventricular hypertrophy is associated with increased myocardial stiffness and dysfunction linked to cardiac morbidity and mortality. We aimed at systematically investigating the degree of left ventricular mass regression and changes in left ventricular function six months after transcatheter aortic valve implantation (TAVI) by cardiovascular magnetic resonance (CMR). Methods Left ventricular mass indexed to body surface area (LVMi), end diastolic volume indexed to body surface area (LVEDVi), left ventricular ejection fraction (LVEF) and stroke volume (SV) were investigated by CMR before and six months after TAVI in patients with severe aortic stenosis and contraindications for surgical aortic valve replacement. Results Twenty-sevent patients had paired CMR at baseline and at 6-month follow-up (N=27), with a mean age of 80.7±5.2 years. LVMi decreased from 84.5±25.2 g/m2 at baseline to 69.4±18.4 g/m2 at six months follow-up (P<0.001). LVEDVi (87.2±30.1 ml /m2vs 86.4±22.3 ml/m2; P=0.84), LVEF (61.5±14.5% vs 65.1±7.2%, P=0.08) and SV (89.2±22 ml vs 94.7±26.5 ml; P=0.25) did not change significantly. Conclusions Based on CMR, significant left ventricular reverse remodeling occurs six months after TAVI. PMID:23692630

  10. Cardiovascular magnetic resonance for the assessment of patients undergoing transcatheter aortic valve implantation: a pilot study

    PubMed Central

    2011-01-01

    Background Before trans-catheter aortic valve implantation (TAVI), assessment of cardiac function and accurate measurement of the aortic root are key to determine the correct size and type of the prosthesis. The aim of this study was to compare cardiovascular magnetic resonance (CMR) and trans-thoracic echocardiography (TTE) for the assessment of aortic valve measurements and left ventricular function in high-risk elderly patients submitted to TAVI. Methods Consecutive patients with severe aortic stenosis and contraindications for surgical aortic valve replacement were screened from April 2009 to January 2011 and imaged with TTE and CMR. Results Patients who underwent both TTE and CMR (n = 49) had a mean age of 80.8 ± 4.8 years and a mean logistic EuroSCORE of 14.9 ± 9.3%. There was a good correlation between TTE and CMR in terms of annulus size (R2 = 0.48, p < 0.001), left ventricular outflow tract (LVOT) diameter (R2 = 0.62, p < 0.001) and left ventricular ejection fraction (LVEF) (R2 = 0.47, p < 0.001) and a moderate correlation in terms of aortic valve area (AVA) (R2 = 0.24, p < 0.001). CMR generally tended to report larger values than TTE for all measurements. The Bland-Altman test indicated that the 95% limits of agreement between TTE and CMR ranged from -5.6 mm to + 1.0 mm for annulus size, from -0.45 mm to + 0.25 mm for LVOT, from -0.45 mm2 to + 0.25 mm2 for AVA and from -29.2% to 13.2% for LVEF. Conclusions In elderly patients candidates to TAVI, CMR represents a viable complement to transthoracic echocardiography. PMID:22202669

  11. Cardiovascular magnetic resonance feature-tracking assessment of myocardial mechanics: Intervendor agreement and considerations regarding reproducibility

    PubMed Central

    Schuster, A.; Stahnke, V.-C.; Unterberg-Buchwald, C.; Kowallick, J.T.; Lamata, P.; Steinmetz, M.; Kutty, S.; Fasshauer, M.; Staab, W.; Sohns, J.M.; Bigalke, B.; Ritter, C.; Hasenfuß, G.; Beerbaum, P.; Lotz, J.

    2015-01-01

    Aim To assess intervendor agreement of cardiovascular magnetic resonance feature tracking (CMR-FT) and to study the impact of repeated measures on reproducibility. Materials and methods Ten healthy volunteers underwent cine imaging in short-axis orientation at rest and with dobutamine stimulation (10 and 20 μg/kg/min). All images were analysed three times using two types of software (TomTec, Unterschleissheim, Germany and Circle, cvi42, Calgary, Canada) to assess global left ventricular circumferential (Ecc) and radial (Err) strains and torsion. Differences in intra- and interobserver variability within and between software types were assessed based on single and averaged measurements (two and three repetitions with subsequent averaging of results, respectively) as determined by Bland–Altman analysis, intraclass correlation coefficients (ICC), and coefficient of variation (CoV). Results Myocardial strains and torsion significantly increased on dobutamine stimulation with both types of software (p<0.05). Resting Ecc and torsion as well as Ecc values during dobutamine stimulation were lower measured with Circle (p<0.05). Intra- and interobserver variability between software types was lowest for Ecc (ICC 0.81 [0.63–0.91], 0.87 [0.72–0.94] and CoV 12.47% and 14.3%, respectively) irrespective of the number of analysis repetitions. Err and torsion showed higher variability that markedly improved for torsion with repeated analyses and to a lesser extent for Err. On an intravendor level TomTec showed better reproducibility for Ecc and torsion and Circle for Err. Conclusions CMR-FT strain and torsion measurements are subject to considerable intervendor variability, which can be reduced using three analysis repetitions. For both vendors, Ecc qualifies as the most robust parameter with the best agreement, albeit lower Ecc values obtained using Circle, and warrants further investigation of incremental clinical merit. PMID:26139384

  12. Using 4D Cardiovascular Magnetic Resonance Imaging to Validate Computational Fluid Dynamics: A Case Study.

    PubMed

    Biglino, Giovanni; Cosentino, Daria; Steeden, Jennifer A; De Nova, Lorenzo; Castelli, Matteo; Ntsinjana, Hopewell; Pennati, Giancarlo; Taylor, Andrew M; Schievano, Silvia

    2015-01-01

    Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta. PMID:26697416

  13. Automated quantitative assessment of cardiovascular magnetic resonance-derived atrioventricular junction velocities.

    PubMed

    Leng, Shuang; Zhao, Xiao-Dan; Huang, Fei-Qiong; Wong, Jia-Ing; Su, Bo-Yang; Allen, John Carson; Kassab, Ghassan S; Tan, Ru-San; Zhong, Liang

    2015-12-01

    The assessment of atrioventricular junction (AVJ) deformation plays an important role in evaluating left ventricular systolic and diastolic function in clinical practice. This study aims to demonstrate the effectiveness and consistency of cardiovascular magnetic resonance (CMR) for quantitative assessment of AVJ velocity compared with tissue Doppler echocardiography (TDE). A group of 145 human subjects comprising 21 healthy volunteers, 8 patients with heart failure, 17 patients with hypertrophic cardiomyopathy, 52 patients with myocardial infarction, and 47 patients with repaired Tetralogy of Fallot were prospectively enrolled and underwent TDE and CMR scan. Six AVJ points were tracked with three CMR views. The peak systolic velocity (Sm1), diastolic velocity during early diastolic filling (Em), and late diastolic velocity during atrial contraction (Am) were extracted and analyzed. All CMR-derived septal and lateral AVJ velocities correlated well with TDE measurements (Sm1: r = 0.736; Em: r = 0.835; Am: r = 0.701; Em/Am: r = 0.691; all p < 0.001) and demonstrated excellent reproducibility [intrastudy: r = 0.921-0.991, intraclass correlation coefficient (ICC): 0.918-0.991; interstudy: r = 0.900-0.970, ICC: 0.887-0.957; all p < 0.001]. The evaluation of three-dimensional AVJ motion incorporating measurements from all views better differentiated normal and diseased states [area under the curve (AUC) = 0.918] and provided further insights into mechanical dyssynchrony diagnosis in HF patients (AUC = 0.987). These findings suggest that the CMR-based method is feasible, accurate, and consistent in quantifying the AVJ deformation, and subsequently in diagnosing systolic and diastolic cardiac dysfunction. PMID:26408537

  14. Assessment of atrial septal defects in adults comparing cardiovascular magnetic resonance with transoesophageal echocardiography

    PubMed Central

    2010-01-01

    Background Many adult patients with secundum-type atrial septal defects (ASDs) are able to have these defects fixed percutaneously. Traditionally, this has involved an assessment of ASD size, geometry and atrial septal margins by transoesophageal echocardiography (TOE) prior to percutaneous closure. This is a semi-invasive technique, and all of the information obtained could potentially be obtained by non-invasive cardiovascular magnetic resonance (CMR). We compared the assessment of ASDs in consecutive patients being considered for percutaneous ASD closure using CMR and TOE. Methods Consecutive patients with ASDs diagnosed on transthoracic echocardiography (TTE) were invited to undergo both CMR and TOE. Assessment of atrial septal margins, maximal and minimal defect dimensions was performed with both techniques. Analyses between CMR and TOE were made using simple linear regression and Bland Altman Analyses. Results Total CMR scan time was 20 minutes, and comparable to the TOE examination time. A total of 20 patients (M:F = 5:15, mean age 42.8 years ± 15.7) were included in the analyses. There was an excellent agreement between CMR and TOE for estimation of maximum defect size (R = 0.87). The anterior inferior, anterior superior and posterior inferior margins could be assessed in all patients with CMR. The posterior superior margin could not be assessed in only one patient. Furthermore, in 1 patient in whom TOE was unable to be performed, CMR was used to successfully direct percutaneous ASD closure. Conclusions CMR agrees with TOE assessment of ASDs in the work-up for percutaneous closure. Potentially CMR could be used instead of TOE for this purpose. PMID:20663157

  15. Cardiovascular magnetic resonance T2 mapping can detect myocardial edema in idiopathic dilated cardiomyopathy.

    PubMed

    Nishii, Tatsuya; Kono, Atsushi K; Shigeru, Mayumi; Takamine, Sachiko; Fujiwara, Sei; Kyotani, Katsusuke; Aoyama, Nobukazu; Sugimura, Kazuro

    2014-06-01

    Myocardial edema and inflammation play an important role in dilated cardiomyopathy (DCM). This pathologic condition can be identified noninvasively using cardiovascular magnetic resonance imaging (CMR). The purpose of this study was to determine the effectiveness of T2 values obtained with T2 mapping in the detection of edema in DCM patients, compared with that of conventional T2-weighted imaging (T2WI). CMR was used for 15 normal controls (NML) and 26 DCM patients. The DCM patients were classified as having either mild dysfunction with a left ventricular ejection fraction (EF) >35% or severe dysfunction with an EF ≤35%. Myocardial edema was assessed by both T2 mapping and T2WI. The differences between the T2 values determined from T2 mapping and the T2 ratios that were calculated from the T2WI were compared among the NML, mild DCM, and severe DCM patients. The T2 values for the NML, mild DCM, and severe DCM patients were 51.2 ± 1.6, 61.2 ± 0.37, and 67.4 ± 6.8, respectively (P < 0.05 for each pair), and the corresponding T2 ratios were 1.88 ± 0.09, 2.12 ± 0.37, and 2.04 ± 0.34, respectively (P > 0.05). T2 mapping clearly showed that the myocardial water content was larger in DCM patients than in NML controls and that the myocardial water content increased as the disease progressed. Thus, T2 mapping is a useful technique for the diagnosis and quantitation of diffuse myocardial edema. PMID:24715436

  16. Three-axis atomic magnetometer based on spin precession modulation

    SciTech Connect

    Huang, H. C.; Dong, H. F. Hu, X. Y.; Chen, L.; Gao, Y.

    2015-11-02

    We demonstrate a three-axis atomic magnetometer with one intensity-modulated pump beam and one orthogonal probe beam. The main field component is measured using the resonance of the pumping light, while the transverse field components are measured simultaneously using the optical rotation of the probe beam modulated by the spin precession. It is an all-optical magnetometer without using any modulation field or radio frequency field. Magnetic field sensitivity of 0.8 pT/Hz{sup 1∕2} is achieved under a bias field of 2 μT.

  17. Parametric pumping of precession modes in ferromagnetic nanodisks

    NASA Astrophysics Data System (ADS)

    Guo, Feng; Belova, L. M.; McMichael, R. D.

    2014-03-01

    We report on the parametric excitation of magnetic precession modes in nanodisks using a parallel pumping configuration. The excitations are detected using a ferromagnetic resonance force microscopy method, and the parallel-pumped spectra reveal nonlinear characteristics including instability thresholds and multiple, narrow, sawtooth-shaped resonances. These characteristics are in accord with analytical theory and micromagnetic modeling results. Modeled mode profiles of the excitations show that higher-order standing spin-wave modes with both even and odd symmetries are excited under parallel pumping.

  18. Static magnetic field effect on the arterial baroreflex-mediated control of microcirculation: implications for cardiovascular effects due to environmental magnetic fields.

    PubMed

    Gmitrov, Juraj

    2007-08-01

    Increasing evidence suggests that time-varying and static magnetic fields in the environment might affect the cardiovascular system. To explore the underlying physiology, the effect of static magnetic fields (SMFs) on the carotid baroreflex control of microcirculation was studied. Twenty-four hemodynamic monitorings were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h) during experiments that lasted 120 min. Mean femoral artery blood pressure, heart rate, and ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after a 40 min exposure of the sinocarotid baroreceptors to Nd(2)-Fe(14)-B alloy magnets (n = 14) or sham magnets (n = 10, control series). The local SMF field was 350 mT, at the baroreceptors' site. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. A significant positive correlation was found between the SMF-induced increase in BRS (DeltaBRS = BRS(afterSMF) - BRS(priorSMF)) and the increment in microvascular blood flow (DeltaMPPG = MPPG(afterSMF) - MPPG(priorSMF)) (r = 0.66, p < 0.009). The SMF probably modulated the arterial baroreflex-mediated microcirculatory control. This could represent one possible mechanism how environmental magnetic fields act on the cardiovascular system, and a method how to complexly adjust macro- and microcirculation with potential clinical implementation. PMID:17530271

  19. Current-Controlled Spin Precession of Quasistationary Electrons in a Cubic Spin-Orbit Field.

    PubMed

    Altmann, P; Hernandez, F G G; Ferreira, G J; Kohda, M; Reichl, C; Wegscheider, W; Salis, G

    2016-05-13

    Space- and time-resolved measurements of spin drift and diffusion are performed on a GaAs-hosted two-dimensional electron gas. For spins where forward drift is compensated by backward diffusion, we find a precession frequency in the absence of an external magnetic field. The frequency depends linearly on the drift velocity and is explained by the cubic Dresselhaus spin-orbit interaction, for which drift leads to a spin precession angle twice that of spins that diffuse the same distance. PMID:27232032

  20. Current-Controlled Spin Precession of Quasistationary Electrons in a Cubic Spin-Orbit Field

    NASA Astrophysics Data System (ADS)

    Altmann, P.; Hernandez, F. G. G.; Ferreira, G. J.; Kohda, M.; Reichl, C.; Wegscheider, W.; Salis, G.

    2016-05-01

    Space- and time-resolved measurements of spin drift and diffusion are performed on a GaAs-hosted two-dimensional electron gas. For spins where forward drift is compensated by backward diffusion, we find a precession frequency in the absence of an external magnetic field. The frequency depends linearly on the drift velocity and is explained by the cubic Dresselhaus spin-orbit interaction, for which drift leads to a spin precession angle twice that of spins that diffuse the same distance.

  1. Highly stable atomic vector magnetometer based on free spin precession.

    PubMed

    Afach, S; Ban, G; Bison, G; Bodek, K; Chowdhuri, Z; Grujić, Z D; Hayen, L; Hélaine, V; Kasprzak, M; Kirch, K; Knowles, P; Koch, H-C; Komposch, S; Kozela, A; Krempel, J; Lauss, B; Lefort, T; Lemière, Y; Mtchedlishvili, A; Naviliat-Cuncic, O; Piegsa, F M; Prashanth, P N; Quéméner, G; Rawlik, M; Ries, D; Roccia, S; Rozpedzik, D; Schmidt-Wellenburg, P; Severjins, N; Weis, A; Wursten, E; Wyszynski, G; Zejma, J; Zsigmond, G

    2015-08-24

    We present a magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 μT magnetic field. Multiple circularly polarized laser beams were used to probe the free spin precession of the Cs atoms. The design was optimized for long-time stability and achieves a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s. The best scalar resolution of less than 80 fT was reached with integration times of 1.6 to 6 s. We were able to measure the magnetic field direction with a resolution better than 10 μrad for integration times from 10 s up to 2000 s. PMID:26368184

  2. Real-time cine and myocardial perfusion with treadmill exercise stress cardiovascular magnetic resonance in patients referred for stress SPECT

    PubMed Central

    2010-01-01

    Background To date, stress cardiovascular magnetic resonance (CMR) has relied on pharmacologic agents, and therefore lacked the physiologic information available only with exercise stress. Methods 43 patients age 25 to 81 years underwent a treadmill stress test incorporating both Tc99m SPECT and CMR. After rest Tc99m SPECT imaging, patients underwent resting cine CMR. Patients then underwent in-room exercise stress using a partially modified treadmill. 12-lead ECG monitoring was performed throughout. At peak stress, Tc99m was injected and patients rapidly returned to their prior position in the magnet for post-exercise cine and perfusion imaging. The patient table was pulled out of the magnet for recovery monitoring. The patient was sent back into the magnet for recovery cine and resting perfusion followed by delayed post-gadolinium imaging. Post-CMR, patients went to the adjacent SPECT lab to complete stress nuclear imaging. Each modality's images were reviewed blinded to the other's results. Results Patients completed on average 9.3 ± 2.4 min of the Bruce protocol. Stress cine CMR was completed in 68 ± 14 sec following termination of exercise, and stress perfusion CMR was completed in 88 ± 8 sec. Agreement between SPECT and CMR was moderate (κ = 0.58). Accuracy in eight patients who underwent coronary angiography was 7/8 for CMR and 5/8 for SPECT (p = 0.625). Follow-up at 6 months indicated freedom from cardiovascular events in 29/29 CMR-negative and 33/34 SPECT-negative patients. Conclusions Exercise stress CMR including wall motion and perfusion is feasible in patients with suspected ischemic heart disease. Larger clinical trials are warranted based on the promising results of this pilot study to allow comparative effectiveness studies of this stress imaging system vs. other stress imaging modalities. PMID:20624294

  3. Precession of the Earth-Moon System

    ERIC Educational Resources Information Center

    Urbassek, Herbert M.

    2009-01-01

    The precession rate of the Earth-Moon system by the gravitational influence of the Sun is derived. Attention is focussed on a physically transparent but complete presentation accessible to first- or second-year physics students. Both a shortcut and a full analysis are given, which allows the inclusion of this material as an example of the physics…

  4. Thomas precession and squeezed states of light

    NASA Technical Reports Server (NTRS)

    Han, D.; Hardekopf, E. E.; Kim, Y. S.

    1989-01-01

    The Lorentz group, which is the language of special relativity, is a useful theoretical toll in modern optics. Optics experiments can therefore serve as analog computers for special relativity. Possible optics experiments involving squeezed states are discussed in connection with the Thomas precession and the Wigner rotation.

  5. Spinor approach to gravitational motion and precession

    SciTech Connect

    Hestenes, D.

    1986-06-01

    The translational and rotational equations of motion for a small rigid body in a gravitational field are combined in a single spinor equation. Besides its computational advantages, this unifies the description of gravitational interaction in classical and quantum theory. Explicit expressions for gravitational precession rates are derived.

  6. Nonrelativistic Contribution to Mercury's Perihelion Precession.

    ERIC Educational Resources Information Center

    Price, Michael P.; Rush, William F.

    1979-01-01

    Presents a calculation of the precession of the perihelion of Mercury due to the perturbations from the outer planets. The time-average effect of each planet is calculated by replacing that planet with a ring of linear mass density equal to the mass of the planet divided by the circumference of its orbit. (Author/GA)

  7. Feature tracking compared with tissue tagging measurements of segmental strain by cardiovascular magnetic resonance

    PubMed Central

    2014-01-01

    Background Left ventricular segmental wall motion analysis is important for clinical decision making in cardiac diseases. Strain analysis with myocardial tissue tagging is the non-invasive gold standard for quantitative assessment, however, it is time-consuming. Cardiovascular magnetic resonance myocardial feature-tracking (CMR-FT) can rapidly perform strain analysis, because it can be employed with standard CMR cine-imaging. The aim is to validate segmental peak systolic circumferential strain (peak SCS) and time to peak systolic circumferential strain (T2P-SCS) analysed by CMR-FT against tissue tagging, and determine its intra and inter-observer variability. Methods Patients in whom both cine CMR and tissue tagging has been performed were selected. CMR-FT analysis was done using endocardial (CMR-FTendo) and mid-wall contours (CMR-FTmid). The Intra Class Correlation Coefficient (ICC) and Pearson correlation were calculated. Results 10 healthy volunteers, 10 left bundle branch block (LBBB) and 10 hypertrophic cardiomyopathy patients were selected. With CMR-FT all 480 segments were analyzable and with tissue tagging 464 segments. Significant differences in mean peak SCS values of the total study group were present between CMR-FTendo and tissue tagging (-23.8 ± 9.9% vs -13.4 ± 3.3%, p < 0.001). Differences were smaller between CMR-FTmid and tissue tagging (-16.4 ± 6.1% vs -13.4 ± 3.3%, p = 0.001). The ICC of the mean peak SCS of the total study group between CMR-FTendo and tissue tagging was low (0.19 (95%-CI-0.10-0.49), p = 0.02). Comparable results were seen between CMR-FTmid and tissue tagging. In LBBB patients, mean T2P-SCS values measured with CMR-FTendo and CMR-FTmid were 418 ± 66 ms, 454 ± 60 ms, which were longer than with tissue tagging, 376 ± 55 ms, both p < 0.05. ICC of the mean T2P-SCS between CMR-FTendo and tissue tagging was 0.64 (95%-CI-0.36-0.81), p < 0.001, this was better in the healthy

  8. Cardiovascular magnetic resonance in pregnancy: Insights from the cardiac hemodynamic imaging and remodeling in pregnancy (CHIRP) study

    PubMed Central

    2014-01-01

    Background Cardiovascular disease in pregnancy is the leading cause of maternal mortality in North America. Although transthoracic echocardiography (TTE) is the most widely used imaging modality for the assessment of cardiovascular function during pregnancy, little is known on the role of cardiovascular magnetic resonance (CMR). The objective of the Cardiac Hemodynamic Imaging and Remodeling in Pregnancy (CHIRP) study was to compare TTE and CMR in the non-invasive assessment of maternal cardiac remodeling during the peripartum period. Methods Between 2010–2012, healthy pregnant women aged 18 to 35 years were prospectively enrolled. All women underwent TTE and CMR during the third trimester and at least 3 months postpartum (surrogate for non-pregnant state). Results The study population included a total of 34 women (mean age 29 ± 3 years). During the third trimester, TTE and CMR demonstrated an increase in left ventricular end-diastolic volume from 95 ± 11 mL to 115 ± 14 mL and 98 ± 6 mL to 125 ± 5 mL, respectively (p < 0.05). By TTE and CMR, there was also an increase in left ventricular (LV) mass during pregnancy from 111 ± 10 g to 163 ± 11 g and 121 ± 5 g to 179 ± 5 g, respectively (p < 0.05). Although there was good correlation between both imaging modalities for LV mass, stroke volume, and cardiac output, the values were consistently underestimated by TTE. Conclusion This CMR study provides reference values for cardiac indices during normal pregnancy and the postpartum state. PMID:24387349

  9. Prospects for aberration corrected electron precession.

    PubMed

    Own, C S; Sinkler, W; Marks, L D

    2007-01-01

    Recent developments in aberration control in the TEM have yielded a tremendous enhancement of direct imaging capabilities for studying atomic structures. However, aberration correction also has substantial benefits for achieving ultra-resolution in the TEM through reciprocal space techniques. Several tools are available that allow very accurate detection of the electron distribution in surfaces allowing precise atomic-scale characterization through statistical inversion techniques from diffraction data. The precession technique now appears to extend this capability to the bulk. This article covers some of the progress in this area and details requirements for a next-generation analytical diffraction instrument. An analysis of the contributions offered by aberration correction for precision electron precession is included. PMID:17207934

  10. Relativistic spin precession in the double pulsar.

    PubMed

    Breton, Rene P; Kaspi, Victoria M; Kramer, Michael; McLaughlin, Maura A; Lyutikov, Maxim; Ransom, Scott M; Stairs, Ingrid H; Ferdman, Robert D; Camilo, Fernando; Possenti, Andrea

    2008-07-01

    The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 degrees (-0 degrees .65)(+0 degrees .66) per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%. PMID:18599782

  11. Method of propulsion of a ferromagnetic core in the cardiovascular system through magnetic gradients generated by an MRI system.

    PubMed

    Mathieu, Jean-Baptiste; Beaudoin, Gilles; Martel, Sylvain

    2006-02-01

    This paper reports the use of a magnetic resonance imaging (MRI) system to propel a ferromagnetic core. The concept was studied for future development of microdevices designed to perform minimally invasive interventions in remote sites accessible through the human cardiovascular system. A mathematical model is described taking into account various parameters such as the size of blood vessels, the velocities and viscous properties of blood, the magnetic properties of the materials, the characteristics of MRI gradient coils, as well as the ratio between the diameter of a spherical core and the diameter of the blood vessels. The concept of magnetic propulsion by MRI is validated experimentally by measuring the flow velocities that magnetized spheres (carbon steel 1010/1020) can withstand inside cylindrical tubes under the different magnetic forces created with a Siemens Magnetom Vision 1.5 T MRI system. The differences between the velocities predicted by the theoretical model and the experiments are approximately 10%. The results indicate that with the technology available today for gradient coils used in clinical MRI systems, it is possible to generate sufficient gradients to propel a ferromagnetic sphere in the larger sections of the arterial system. In other words, the results show that in the larger blood vessels where the diameter of the microdevices could be as large as a couple a millimeters, the few tens of mT/m of gradients required for displacement against the relatively high blood flow rate is well within the limits of clinical MRI systems. On the other hand, although propulsion of a ferromagnetic core with diameter of approximately 600 microm may be possible with existing clinical MRI systems, gradient amplitudes of several T/m would be required to propel a much smaller ferromagnetic core in small vessels such as capillaries and additional gradient coils would be required to upgrade existing MRI systems for operations at such a scale. PMID:16485758

  12. Geodetic precession or dragging of inertial frames

    NASA Technical Reports Server (NTRS)

    Ashby, Neil; Shahid-Saless, Bahman

    1989-01-01

    In General Relativity, the Principle of General Covariance allows one to describe phenomena by means of any convenient choice of coordinate system. Here, it is shown that the geodetic precession of a gyroscope orbiting a spherically symmetric, nonrotating mass can be recast as a Lense-Thirring frame-dragging effect, in an appropriately chosen coordinate frame whose origin falls freely along with the gyroscope and whose spatial coordinate axes point in fixed directions.

  13. Uncertainty relations and precession of perihelion

    NASA Astrophysics Data System (ADS)

    Scardigli, Fabio; Casadio, Roberto

    2016-03-01

    We compute the corrections to the Schwarzschild metric necessary to reproduce the Hawking temperature derived from a Generalized Uncertainty Principle (GUP), so that the GUP deformation parameter is directly linked to the deformation of the metric. Using this modified Schwarzschild metric, we compute corrections to the standard General Relativistic predictions for the perihelion precession for planets in the solar system, and for binary pulsars. This analysis allows us to set bounds for the GUP deformation parameter from well-known astronomical measurements.

  14. Using the P03 Precession Model

    NASA Astrophysics Data System (ADS)

    Wallace, P. T.; Capitaine, N.

    2006-08-01

    The precession model adopted by the IAU in 2000 comprised the existing Lieske et al. (1977) model plus rate corrections of about 300 mas/cy in longitude and 25 mas/cy in obliquity. Though accurate with respect to existing VLBI observations, the IAU 2000 model is not consistent with dynamical theory, and consequently the IAU Working Group on precession and the ecliptic has recommended (Hilton et al. 2006) that it be replaced by the "P03" model of Capitaine et al. (2003). P03 provides improved models for both the equator and the ecliptic, and also includes parameterized provision for future adjustment to match new determinations of properties of the non-rigid Earth such as the precession rates and J2 rate. Practical use of the new model involves choices of algorithm and computational procedure, and a number of ways have been studied (Capitaine & Wallace 2006) of generating the directions of the celestial intermediate pole and origin (CIP, CIO), from which the usual rotation matrices can be obtained. From a wide range of possible procedures we have selected two that target different classes of application, typified by the SOFA software and the IERS Conventions respectively. These procedures achieve a high standard of consistency, both internal and mutual, as well as being efficient and versatile. One is based on the Fukushima-Williams precession-nutation angles, the other on series for the CIP coordinates. Both use the CIO locator s, and both deliver the full range of products, supporting classical equinox/GST methods in addition to the CIO/ERA "new paradigm".

  15. Turbulent mixing in a precessing sphere

    SciTech Connect

    Goto, Susumu Shimizu, Masaki; Kawahara, Genta

    2014-11-15

    By numerically simulating turbulent flows at high Reynolds numbers in a precessing sphere, we propose a method to enhance the mixing of a fluid confined within a smooth cavity by its rotational motion alone. To precisely evaluate the mixing efficiency, we extend the quantification method proposed by Danckwerts [“The definition and measurement of some characteristics of mixtures,” Appl. Sci. Res. A 3, 279–296 (1952)] to the case in which only a finite number of fluid particle trajectories can be known. Our accurate numerical tracking of fluid particles in the flow, which is controlled by the Reynolds number (an indicator of the spin rate) and the Poincaré number (the precession rate), shows the following results. First, the mixing process on the time scale normalized by the spin period is independent of the Reynolds number as long as it is high enough for the flow to be developed turbulence. Second, fastest mixing is achieved under weak precession (Poincaré number ≈0.1); in such cases, perfect mixing requires only 10–15 spins of the container. Third, the power to sustain turbulence is a weakly increasing function of the Poincaré number, and the energy efficiency of the mixing is also maximized when the Poincaré number is about 0.1. Fourth, efficient mixing driven by the weak precession arises from the effective cooperation of complex large-scale flow and small-scale turbulence, which itself is sustained by the large-scale flow.

  16. Structure refinement from precession electron diffraction data.

    PubMed

    Palatinus, Lukáš; Jacob, Damien; Cuvillier, Priscille; Klementová, Mariana; Sinkler, Wharton; Marks, Laurence D

    2013-03-01

    Electron diffraction is a unique tool for analysing the crystal structures of very small crystals. In particular, precession electron diffraction has been shown to be a useful method for ab initio structure solution. In this work it is demonstrated that precession electron diffraction data can also be successfully used for structure refinement, if the dynamical theory of diffraction is used for the calculation of diffracted intensities. The method is demonstrated on data from three materials - silicon, orthopyroxene (Mg,Fe)(2)Si(2)O(6) and gallium-indium tin oxide (Ga,In)(4)Sn(2)O(10). In particular, it is shown that atomic occupancies of mixed crystallographic sites can be refined to an accuracy approaching X-ray or neutron diffraction methods. In comparison with conventional electron diffraction data, the refinement against precession diffraction data yields significantly lower figures of merit, higher accuracy of refined parameters, much broader radii of convergence, especially for the thickness and orientation of the sample, and significantly reduced correlations between the structure parameters. The full dynamical refinement is compared with refinement using kinematical and two-beam approximations, and is shown to be superior to the latter two. PMID:23403968

  17. Warp evidence in precessing galactic bar models

    NASA Astrophysics Data System (ADS)

    Sánchez-Martín, P.; Romero-Gómez, M.; Masdemont, J. J.

    2016-04-01

    Most galaxies have a warped shape when they are seen edge-on. The reason for this curious form is not completely known so far, so in this work we apply dynamical system tools to contribute to its explanation. Starting from a simple, but realistic model formed by a bar and a disc, we study the effect of a small misalignment between the angular momentum of the system and its angular velocity. To this end, a precession model was developed and considered, assuming that the bar behaves like a rigid body. After checking that the periodic orbits inside the bar continue to be the skeleton of the inner system even after inflicting a precession to the potential, we computed the invariant manifolds of the unstable periodic orbits departing from the equilibrium points at the ends of the bar to find evidence of their warped shapes. As is well known, the invariant manifolds associated with these periodic orbits drive the arms and rings of barred galaxies and constitute the skeleton of these building blocks. Looking at them from a side-on viewpoint, we find that these manifolds present warped shapes like those recognised in observations. Lastly, test particle simulations have been performed to determine how the stars are affected by the applied precession, this way confirming the theoretical results.

  18. Longitudinal and transverse right ventricular function in pulmonary hypertension: cardiovascular magnetic resonance imaging study from the ASPIRE registry

    PubMed Central

    Rajaram, Smitha; Capener, Dave; Elliot, Charlie; Condliffe, Robin; Wild, Jim M.; Kiely, David G.

    2015-01-01

    Abstract Right ventricular (RV) function is a strong predictor of outcome in cardiovascular diseases. Two components of RV function, longitudinal and transverse motion, have been investigated in pulmonary hypertension (PH). However, their individual clinical significance remains uncertain. The aim of this study was to determine the factors associated with transverse and longitudinal RV motion in patients with PH. In 149 treatment-naive patients with PH and 16 patients with suspected PH found to have mean pulmonary arterial pressure of <20 mmHg, cardiovascular magnetic resonance imaging was performed within 24 hours of right heart catheterization. In patients with PH, fractional longitudinal motion (fractional tricuspid annulus to apex distance [f-TAAD]) was significantly greater than fractional transverse motion (fractional septum to free wall distance [f-SFD]; P = 0.002). In patients without PH, no significant difference between f-SFD and f-TAAD was identified (P = 0.442). Longitudinal RV motion was singularly associated with RV ejection fraction independent of age, invasive hemodynamics, and cardiac magnetic resonance measurements (P = 0.024). In contrast, transverse RV motion was independently associated with left ventricular eccentricity (P = 0.036) in addition to RV ejection fraction (P = 0.014). In conclusion, RV motion is significantly greater in the longitudinal direction in patients with PH, whereas patients without PH have equal contributions of transverse and longitudinal motion. Longitudinal RV motion is primarily associated with global RV pump function in PH. Transverse RV motion not only reflects global pump function but is independently influenced by ventricular interaction in patients with PH. PMID:26401257

  19. Cardiovascular magnetic resonance and computed tomography in the evaluation of aneurysmal coronary-cameral fistula

    PubMed Central

    Detorakis, Efstathios E; Foukarakis, Emmanouil; Karavolias, George; Dermitzakis, Alkiviades

    2015-01-01

    Coronary artery fistulas represent abnormal communications between a coronary artery and a major vessel like venae cavae, pulmonary arteries or veins, the coronary sinus, or a cardiac chamber. The latter is called coronary cameral fistula is a rare condition and is most of the times congenital but can be also post traumatic or post surgical, especially after cardiovascular interventional procedures. Most patients are asymptomatic and coronary-cameral fistulae are discovered incidentally during angiographic evaluation for coronary vascular disorders, while other patients have a clinical presentation ranging from angina pectoris to heart failure. In this article, we report a rare case of an aneurysmal right coronary cameral fistula draining into the left ventricle. Echocardiography usually represents the first diagnostic imaging approach, but often due to a poor acoustic window may not show the entire course of the fistula which is crucial for the final diagnosis. ECG-gated cardiovascular CT may play an important role in the evaluation of the origin, course, termination and morphology of the fistula, its relation to the adjacent anatomical structures as well as the morphology and contractility of the heart. Cardiac MRI instead plays an additional crucial role regarding not only the above mentioned factors but also in estimating the blood flow within the fistula, providing more detailed information about the cardiac function but also about myocardial wall viability. PMID:26629294

  20. Quipus and System of Coordinated Precession

    NASA Astrophysics Data System (ADS)

    Campos, T. C.

    2004-05-01

    The Incas of ancient Peru possessed no writing. Instead, they developed a unique system expressed on spatial arrays of colored knotted cords called Quipus to record and transmit information throughout their vast empire. In their thorough description of quipus, Ascher & Ascher observed that in two cases the numbers registered in their strings have a very special relationship to each other. For this to occur the numbers must have been obtained through the multiplication of whole numbers by fractions or decimals, operations apparently beyond the arithmetic knowledge of the Incas. The quipus AS120 and AS143, coming from Ica (Peru) and conserved in the Museum of Berlin has the suitable characteristics previously. In the AS143 there is a the relationship with the systems of coordinated precession (tilt of Earth's spin axis (40036); eccentricity of Earth's orbit (97357); and precession of equinoxes (between 18504 and 23098)). For the history of the Earth are necessary an chronometer natural to coordinate and to classify the observations and this chronometer comes to be the vernal point, defining the vernal point as" a sensitive axis of maximum conductivity" as itdemonstrates it the stability of the geomagnetic equator (inclination of the field is zero grades), in the year 1939 calculated with the IGRF from the year 1900 up to the 2004 and that it is confirmed with tabulated data of the Geophysical Institute of Huancayo (Peru),from that date until this year (2004) and this fluctuating between the 12-14 South.,on the other hand in the area of Brazil it has advanced very quickly toward the north, and above to 108 km. approximately it is located the equatorial electrojet that is but intense in the equinoxes in South America. And this stability from the point of view of the precession of the equinoxes this coinciding with the entrance of the apparent sun for the constellation of Aquarius, being this mechanism the base to establish a system of coordinated precession where it is

  1. Laser induced spin precession in highly anisotropic granular L1{sub 0} FePt

    SciTech Connect

    Becker, J.; Mosendz, O.; Weller, D.; Kirilyuk, A.; Rasing, Th.; Kimel, A.; Maan, J. C.; Christianen, P. C. M.

    2014-04-14

    The dynamic magnetic properties of a highly anisotropic, granular L1{sub 0} FePt thin film in magnetic fields up to 7 T are investigated using time-resolved magneto-optical Kerr effect measurements. We find that ultrashort laser pulses induce coherent spin precession in the granular FePt sample. Frequencies of spin precession up to over 400 GHz are observed, which are strongly field and temperature dependent. The high frequencies can be ascribed to the high value of the magnetocrystalline anisotropy constant K{sub u} leading to large anisotropy fields H{sub a} of up to 10.7 T at 170 K. A Gilbert damping parameter of α ∼ 0.1 was derived from the lifetimes of the oscillations.

  2. Research program in nuclear and solid state physics. [including pion absorption spectra and muon spin precession

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.

  3. Electrocardiographic diagnosis of left ventricular hypertrophy in aortic valve disease: evaluation of ECG criteria by cardiovascular magnetic resonance

    PubMed Central

    Buchner, Stefan; Debl, Kurt; Haimerl, Josef; Djavidani, Behrus; Poschenrieder, Florian; Feuerbach, Stefan; Riegger, Guenter AJ; Luchner, Andreas

    2009-01-01

    Background Left ventricular hypertrophy (LVH) is a hallmark of chronic pressure or volume overload of the left ventricle and is associated with risk of cardiovascular morbidity and mortality. The purpose was to evaluate different electrocardiographic criteria for LVH as determined by cardiovascular magnetic resonance (CMR). Additionally, the effects of concentric and eccentric LVH on depolarization and repolarization were assessed. Methods 120 patients with aortic valve disease and 30 healthy volunteers were analysed. As ECG criteria for LVH, we assessed the Sokolow-Lyon voltage/product, Gubner-Ungerleider voltage, Cornell voltage/product, Perugia-score and Romhilt-Estes score. Results All ECG criteria demonstrated a significant correlation with LV mass and chamber size. The highest predictive values were achieved by the Romhilt-Estes score 4 points with a sensitivity of 86% and specificity of 81%. There was no difference in all ECG criteria between concentric and eccentric LVH. However, the intrinsicoid deflection (V6 37 ± 1.0 ms vs. 43 ± 1.6 ms, p < 0.05) was shorter in concentric LVH than in eccentric LVH and amplitudes of ST-segment (V5 -0.06 ± 0.01 vs. -0.02 ± 0.01) and T-wave (V5 -0.03 ± 0.04 vs. 0.18 ± 0.05) in the anterolateral leads (p < 0.05) were deeper. Conclusion By calibration with CMR, a wide range of predictive values was found for the various ECG criteria for LVH with the most favourable results for the Romhilt-Estes score. As electrocardiographic correlate for concentric LVH as compared with eccentric LVH, a shorter intrinsicoid deflection and a significant ST-segment and T-wave depression in the anterolateral leads was noted. PMID:19486532

  4. Role of cardiovascular magnetic resonance imaging in arrhythmogenic right ventricular dysplasia

    PubMed Central

    Jain, Aditya; Tandri, Harikrishna; Calkins, Hugh; Bluemke, David A

    2008-01-01

    Arrhythmogenic right ventricular dysplasia (ARVD) is a genetic cardiomyopathy characterized clinically by ventricular arrhythmias and progressive right ventricular (RV) dysfunction. The histopathologic hallmark is fibro-fatty replacement of RV myocardium. It is inherited in an autosomal pattern with variable penetrance. ARVD is unique in that it most commonly presents in young, otherwise healthy and highly athletic individuals. The cause of ARVD is not well-known but recent evidence suggests strongly that it is a disease of desmosomal dysfunction. The disease involvement is not limited only to the RV as left ventricle (LV) has also been reportedly affected. Diagnosis of ARVD is challenging and is currently based upon a multi-disciplinary work-up of the patient as defined by the Task Force. Currently, implanted cardioverter defibrillators (ICD) are routinely used to prevent sudden death in patients with ARVD. Cardiovascular MR is an important non-invasive diagnostic modality that allows both qualitative and quantitative evaluation of RV. This article reviews the genetics of ARVD, current status and role of CMR in the diagnosis of ARVD and LV involvement in ARVD. PMID:18570661

  5. Photon-assisted electronic and spin transport in a junction containing precessing molecular spin

    NASA Astrophysics Data System (ADS)

    Filipović, Milena; Belzig, Wolfgang

    2016-02-01

    We study the ac charge and -spin transport through an orbital of a magnetic molecule with spin precessing in a constant magnetic field. We assume that the source and drain contacts have time-dependent chemical potentials. We employ the Keldysh nonequilibrium Green's functions method to calculate the spin and charge currents to linear order in the time-dependent potentials. The molecular and electronic spins are coupled via exchange interaction. The time-dependent molecular spin drives inelastic transitions between the molecular quasienergy levels, resulting in a rich structure in the transport characteristics. The time-dependent voltages allow us to reveal the internal precession time scale (the Larmor frequency) by a dc conductance measurement if the ac frequency matches the Larmor frequency. In the low-ac-frequency limit the junction resembles a classical electric circuit. Furthermore, we show that the setup can be used to generate dc-spin currents, which are controlled by the molecular magnetization direction and the relative phases between the Larmor precession and the ac voltage.

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

    PubMed Central

    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. PMID:22163498

  7. Review Of The Working Group On Precession And The Ecliptic

    NASA Astrophysics Data System (ADS)

    Hilton, J. L.

    2006-08-01

    The IAU Working Group on Precession and the Ecliptic was charged with providing a precession model that was both dynamically consistent and compatible with the IAU 2000A nutation model, along with an updated definition and model for the ecliptic. The report of the working group has been accepted for publication in Celestial Mechanics (Hilton et al. 2006, in press) and has resulted in a recommendation to be considered at this General Assembly of the IAU. Specifically, the working group recommends: 1. That the terms lunisolar precession and planetary precession be replaced by precession of the equator and precession of the ecliptic, respectively. 2. That, beginning on 1 January 2009, the precession component of the IAU 2000A precession-nutation model be replaced by the P03 precession theory, of Capitaine et al. (2003, A&A, 412, 567-586) for the precession of the equator (Eqs. 37) and the precession of the ecliptic (Eqs. 38); the same paper provides the polynomial developments for the P03 primary angles and a number of derived quantities for use in both the equinox based and Celestial Intermediate Origin based paradigms. 3. That the choice of precession parameters be left to the user. 4. That the ecliptic pole should be explicitly defined by the mean orbital angular momentum vector of the Earth-Moon barycenter in an inertial reference frame, and this definition should be explicitly stated to avoid confusion with other, older definitions. consistent and compatible with the IAU 2000A nutation model, along consistent and compatible with the IAU 2000A nutation model, along with an updated definition and model for the ecliptic. The report of the working group has been accepted for publication in Celestial Mechanics (Hilton et al. 2006, in press) and has resulted in a recommendation to be considered at this General Assembly of the IAU. Specifically, the working group recommends, * that the terms lunisolar precession and planetary precession be replaced by precession of the

  8. Relativistic 3D precessing jet simulations for the X-ray binary SS433

    NASA Astrophysics Data System (ADS)

    Monceau-Baroux, Rémi; Porth, Oliver; Meliani, Zakaria; Keppens, Rony

    2014-01-01

    Context. Modern high-resolution radio observations allow us a closer look into the objects that power relativistic jets. This is especially the case for SS433, an X-ray binary that emits a precessing jet that is observed down to the subparsec scale. Aims: We aim to study full 3D dynamics of relativistic jets associated with active galactic nuclei or X-ray binaries (XRB). In particular, we incorporate the precessing motion of a jet into a model for the jet associated with the XRB SS433. Our study of the jet dynamics in this system focuses on the subparsec scales. We investigate the impact of jet precession and the variation of the Lorentz factor of the injected matter on the general 3D jet dynamics and its energy transfer to the surrounding medium. After visualizing and quantifying jet dynamics, we aim to realize synthetic radio mapping of the data, to compare our results with observations. Methods: For our study we used a block-tree adaptive mesh refinement scheme and an inner time-dependent boundary prescription to inject precessing bipolar supersonic jets. Parameters extracted from observations were used. Different 3D jet realizations that match the kinetic flux of the SS433 jet were intercompared, which vary in density contrast and jet beam velocity. We tracked the energy content deposited in different regions of the domain affected by the jet. Our code allows us to follow the adiabatic cooling of a population of relativistic particles injected by the jet. This evolving energy spectrum of accelerated electrons, using a pressure-based proxy for the magnetic field, allowed us to obtain the radio emission from our simulation. Results: We find a higher energy transfer for a precessing jet than for standing jets with otherwise identical parameters as a result of the effectively increased interaction area. We obtain synthetic radio maps for all jets, from which one can see that dynamical flow features are clearly linked with enhanced emission sites. Conclusions: The

  9. SU-E-T-145: Effects of Temporary Tachytherapy Inhibition Magnet On MOSFET Dose Measurements of Cardiovascular Implantable Electronic Devices (CIED) in Radiation Therapy Patients

    SciTech Connect

    P, Joshi; Salomons, G; Kerr, A; Peters, C; Lalonde, M

    2014-06-01

    Purpose: To determine the effects of temporary tachytherapy inhibition magnet on MOSFET dose measurements of cardiovascular implantable electronic devices (CIED) in radiation therapy patients. Methods: Infield and peripheral MOSFET dose measurements with 6MV photon beams were performed to evaluate dose to a CIED in the presence of a doughnut shaped temporary tachytherapy inhibition magnet. Infield measurements were done to quantify the effects of the magnetic field alone and shielding by the magnet. MOSFETs were placed inside a 20×20cm{sup 2} field at a depth of 3cm in the isocentre plane in the presence and absence of the magnet. Peripheral dose measurements were done to determine the impact of the magnet on dose to the CIED in a clinical setting. These measurements were performed at the centre, under the rim and half way between a 10×10cm{sup 2} field edge and the magnet with MOSFETS placed at the surface, 0.5cm and 1cm depths in the presence and absence of the magnet. Results: Infield measurements showed that effects of magnetic field on the MOSFET readings were within the 2% MOSFET dose measurement uncertainty; a 20% attenuation of dose under the magnet rim was observed. Peripheral dose measurements at the centre of the magnet show an 8% increase in surface dose and a 6% decrease in dose at 1cm depth. Dose under the magnet rim was reduced by approximately 68%, 45% and 25% for MOSFET placed at 0.0, 0.5 and 1.0cm bolus depths, respectively. Conclusions: The magnetic field has an insignificant effect on MOSFET dose measurements. Dose to the central region of CIED represented by centre of the magnet doughnut increases at the surface, and decreases at depths due to low energy scattering contributions from the magnet. Dose under the magnet rim, representing CIED edges, decreased significantly due to shielding.

  10. Geodetic precession in squashed Kaluza-Klein black hole spacetimes

    SciTech Connect

    Matsuno, Ken; Ishihara, Hideki

    2009-11-15

    We investigate the geodetic precession effect of a parallelly transported spin vector along a circular geodesic in five-dimensional squashed Kaluza-Klein black hole spacetime. Then we derive the higher-dimensional correction of the precession angle to general relativity. We find that the correction is proportional to the square of (size of extra dimension)/(gravitational radius of central object)

  11. precession: Dynamics of spinning black-hole binaries with python

    NASA Astrophysics Data System (ADS)

    Gerosa, Davide; Kesden, Michael

    2016-06-01

    We present the numerical code precession, a new open-source python module to study the dynamics of precessing black-hole binaries in the post-Newtonian regime. The code provides a comprehensive toolbox to (i) study the evolution of the black-hole spins along their precession cycles, (ii) perform gravitational-wave-driven binary inspirals using both orbit-averaged and precession-averaged integrations, and (iii) predict the properties of the merger remnant through fitting formulas obtained from numerical-relativity simulations. precession is a ready-to-use tool to add the black-hole spin dynamics to larger-scale numerical studies such as gravitational-wave parameter estimation codes, population synthesis models to predict gravitational-wave event rates, galaxy merger trees and cosmological simulations of structure formation. precession provides fast and reliable integration methods to propagate statistical samples of black-hole binaries from/to large separations where they form to/from small separations where they become detectable, thus linking gravitational-wave observations of spinning black-hole binaries to their astrophysical formation history. The code is also a useful tool to compute initial parameters for numerical-relativity simulations targeting specific precessing systems. precession can be installed from the python Package Index, and it is freely distributed under version control on github, where further documentation is provided.

  12. Established and emerging cardiovascular magnetic resonance techniques for the assessment of stable coronary heart disease and acute coronary syndromes

    PubMed Central

    Ripley, David P.; Motwani, Manish; Plein, Sven

    2014-01-01

    Coronary heart disease (CHD) is a leading cause of death and disability worldwide. International guidelines recommend cardiovascular magnetic resonance (CMR) as an investigative option in those presenting with chest pain to inform diagnosis, risk stratify and determine the need for revascularization. CMR offers a unique method to assess global and regional cardiac function, myocardial perfusion, myocardial viability, tissue characterisation and proximal coronary anatomy all within a single study. This results in high diagnostic accuracy for the detection of significant coronary stenoses and an established role in the management of both stable CHD and acute coronary syndromes (ACS). The growing evidence base for the prognostic value of CMR, emerging advances in acquisition techniques, improvements in hardware and the completion of current major multi-centre clinical CMR trials will further raise its prominence in international guidelines and routine cardiological practice. This article will focus on the rapidly evolving role of the multi-parametric CMR examination in the assessment of patients with stable and unstable CHD. PMID:25392820

  13. Is there a place for cardiovascular magnetic resonance conditional devices in systemic inflammatory diseases?

    PubMed

    Mavrogeni, Sophie I; Poulos, George; Sfikakis, Petros P; Kitas, George D; Kolovou, Genovefa; Theodorakis, George

    2016-06-01

    Rhythm disturbances and sudden cardiac death (SCD) are important manifestations of cardiac involvement in systemic inflammatory diseases (SID). The commonest events demanding the implantation of a device include ventricular tachycardia and atrioventricular block, mainly diagnosed in sarcoidosis, systemic lupus erythematosus and scleroderma. In SCD, cardiac magnetic resonance (CMR) identified areas of late gadolinium enhancement (LGE) in 71% and provided an arrhythmic substrate in 76%, while during the follow-up, the extent of LGE identified a subgroup at increased risk for future adverse events. CMR has been successfully used for detection of cardiac disease in SID, including myocarditis, coronary, microvascular and valvular disease. Additionally, SIDs have a higher probability to need MRI scanning of other organs, due to their systemic disease. These reasons support the necessity of an MRI conditional device in SIDs. A broad selection of devices, approved for the MRI environment under defined conditions allows the safe and accurate scanning of SID patients. PMID:26878099

  14. Aortic Relative Pressure Components Derived from Four-Dimensional Flow Cardiovascular Magnetic Resonance

    PubMed Central

    Lamata, Pablo; Pitcher, Alex; Krittian, Sebastian; Nordsletten, David; Bissell, Malenka M; Cassar, Thomas; Barker, Alex J; Markl, Michael; Neubauer, Stefan; Smith, Nicolas P

    2014-01-01

    Purpose To describe the assessment of the spatiotemporal distribution of relative aortic pressure quantifying the magnitude of its three major components. Methods Nine healthy volunteers and three patients with aortic disease (bicuspid aortic valve, dissection, and Marfan syndrome) underwent 4D-flow CMR. Spatiotemporal pressure maps were computed from the CMR flow fields solving the pressure Poisson equation. The individual components of pressure were separated into time-varying inertial (“transient”), spatially varying inertial (“convective”), and viscous components. Results Relative aortic pressure is primarily caused by transient effects followed by the convective and small viscous contributions (64.5, 13.6, and 0.3 mmHg/m, respectively, in healthy subjects), although regional analysis revealed prevalent convective effects in specific contexts, e.g., Sinus of Valsalva and aortic arch at instants of peak velocity. Patients showed differences in peak transient values and duration, and localized abrupt convective changes explained by abnormalities in aortic geometry, including the presence of an aneurysm, a pseudo-coarctation, the inlet of a dissection, or by complex flow patterns. Conclusion The evaluation of the three components of relative pressure enables the quantification of mechanistic information for understanding and stratifying aortic disease, with potential future implications for guiding therapy. Magn Reson Med 72:1162–1169, 2014. © 2013 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:24243444

  15. In vitro study on the feasibility of magnetic stent hyperthermia for the treatment of cardiovascular restenosis.

    PubMed

    Li, Li; Wang, Rui; Shi, Huan-Huan; Xie, LE; Li, Jing-Ding-Sha; Kong, Wei-Chao; Tang, Jin-Tian; Ke, DA-Nian; Zhao, Ling-Yun

    2013-08-01

    Thermal treatment or hyperthermia has received considerable attention in recent years due to its high efficiency, safety and relatively few side-effects. In this study, we investigated whether it was possible to utilize targeted thermal or instent thermal treatments for the treatment of restenosis following percutaneous transluminal coronary angioplasty (PTCA) through magnetic stent hyperthermia (MSH). A 316L stainless steel stent and rabbit vascular smooth muscle cells (VSMCs) were used in the present study, in which the inductive heating characteristics of the stent under alternative magnetic field (AMF) exposure, as well as the effect of MSH on the proliferation, apoptosis, cell cycle and proliferating cell nuclear antigen (PCNA) expression of the rabbit VSMCs, were evaluated. The results demonstrated that 316L stainless steel coronary stents possess ideal inductive heating characteristics under 300 kHz AMF exposure. The heating properties were shown to be affected by the field intensity of the AMF, as well as the orientation the stent axis. MSH had a significant effect on the proliferation and apoptosis of VSMCs, and the effect was temperature-dependent. While a mild temperature of 43°C demonstrated negligible effects on the growth of VSMCs, MSH treatment above 47°C effectively inhibited the VSMC proliferation and induced apoptosis. Furthermore, a 47°C treatment exhibited a significant and long-term inhibitory effect on VSMC migration. The results strongly suggested that MSH may be potentially applied in the clinic as an alternative approach for the prevention and treatment of restenosis. PMID:24137187

  16. Effect of equinoctial precession on geosynchronous earth satellites

    NASA Astrophysics Data System (ADS)

    Gurfil, P.

    The long-periodic effects of the equinoctial precession on geosynchronous Earth orbit satellites are investigated. The equations of motion in a reference frame that coprecesses with the Earth are developed, and the resulting variational equations are derived using mean classical orbital elements. The Earth gravitational model includes the J_2 and J_3 zonal harmonics, which induce the equinoctial precession due to the lunisolar gravitational torque. It is shown that the ever-growing lifetime and mass of geosynchronous Earth orbit satellites render the equinoctial precession a significant factor, which should be taken into account during mission design, as it affects north-south stationkeeping maneuvers. The equilibria of the variational equations including the zonal harmonics and the equinoctial precession are investigated and a class of stable frozen orbits which are equinoctial precession invariant is derived.

  17. Rectification and precession signals in the climate system

    NASA Astrophysics Data System (ADS)

    Huybers, P.; Wunsch, C.

    2003-10-01

    Precession of the equinoxes has no effect on the mean annual insolation, but does modulate the amplitude of the seasonal cycle. In a linear climate system, there would be no energy near the 21,000 year precession period. It is only when a non-linear mechanism rectifies the seasonal modulation that precession-period variability appears. Such rectification can arise from physical processes within the climate system, for example a dependence of ice cover only on summer maximum insolation. The possibility exists, however, that the seasonality inherent in many climate proxies will produce precession-period variability in the records independent of any precession-period variability in the climate. One must distinguish this instrumental effect from true climate responses. Careful examination of regions without seasonal cycles, for example the abyssal ocean, and the use of proxies with different seasonal responses, might permit separation of physical from instrumental effects.

  18. Meeting Highlights of the 11th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance, Los Angeles, February 1–3, 2008

    PubMed Central

    2008-01-01

    This paper features the most interesting presentations and discussions of the 2008 Annual Sessions of the Society for Cardiovascular Magnetic Resonance, which were held in Los Angeles from February 1 to 3, 2008. With more than 1100 attendees, this was the largest of the SCMR meetings ever. Among this year's highlights were scientific reports on CMR-based risk assessment, non-contrast tissue characterization, 3 T data, and interventional CMR. PMID:19128420

  19. Division I Working Group on `Precession and the Ecliptic'

    NASA Astrophysics Data System (ADS)

    Hilton, James L.; Capitaine, N.; Chapront, J.; Ferrandiz, J. M.; Fienga, A.; Fukushima, T.; Getino, J.; Mathews, P.; Simon, J.-L.; Soffel, M.; Vondrak, J.; Wallace, P.; Williams, J.

    2007-03-01

    The WG has conferred via email on the topics of providing a precession theory dynamically consistent with the IAU 2000A nutation theory and updating the expressions defining the ecliptic. The consensus of the WG is to recommend:(a) The terms lunisolar precession and planetary precession be replaced by precession of the equator and precession of the ecliptic, respectively.(b) The IAU adopt the P03 precession theory, of Capitaine et al (2003a, A& A 412, 567-586) for the precession of the equator (Eqs. 37) and the precession of the ecliptic (Eqs. 38); the same paper provides the polynomial developments for the P03 primary angles and a number of derived quantities for use in both the equinox based and celestial intermediate origin based paradigms.(c) The choice of precession parameters be left to the user.(d) The recommended polynomial coefficients for a number of precession angles are given in Table 1 of the WG report, including the P03 expressions set out in Tables 3-5 of Capitaine et al (2005, A& A 432, 355-367), and those of the alternative Fukushima (2003, AJ 126, 494-534) parameterization; the corresponding matrix representations are given in equations 1, 6, 11, and 22 of the WG report.(e) The ecliptic pole should be explicitly defined by the mean orbital angular momentum vector of the Earth-Moon barycenter in an inertial reference frame, and this definition should be explicitly stated to avoid confusion with older definitions. The formal WG report will be submitted, shortly to Celest. Mech. for publication and their recommendations will be submitted at the next General Assembly for adoption by the IAU.

  20. Scanning precession electron tomography for three-dimensional nanoscale orientation imaging and crystallographic analysis.

    PubMed

    Eggeman, Alexander S; Krakow, Robert; Midgley, Paul A

    2015-01-01

    Three-dimensional (3D) reconstructions from electron tomography provide important morphological, compositional, optical and electro-magnetic information across a wide range of materials and devices. Precession electron diffraction, in combination with scanning transmission electron microscopy, can be used to elucidate the local orientation of crystalline materials. Here we show, using the example of a Ni-base superalloy, that combining these techniques and extending them to three dimensions, to produce scanning precession electron tomography, enables the 3D orientation of nanoscale sub-volumes to be determined and provides a one-to-one correspondence between 3D real space and 3D reciprocal space for almost any polycrystalline or multi-phase material. PMID:26028514

  1. Scanning precession electron tomography for three-dimensional nanoscale orientation imaging and crystallographic analysis

    PubMed Central

    Eggeman, Alexander S.; Krakow, Robert; Midgley, Paul A.

    2015-01-01

    Three-dimensional (3D) reconstructions from electron tomography provide important morphological, compositional, optical and electro-magnetic information across a wide range of materials and devices. Precession electron diffraction, in combination with scanning transmission electron microscopy, can be used to elucidate the local orientation of crystalline materials. Here we show, using the example of a Ni-base superalloy, that combining these techniques and extending them to three dimensions, to produce scanning precession electron tomography, enables the 3D orientation of nanoscale sub-volumes to be determined and provides a one-to-one correspondence between 3D real space and 3D reciprocal space for almost any polycrystalline or multi-phase material. PMID:26028514

  2. Relationship between coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance and serum eicosapentaenoic acid

    PubMed Central

    2013-01-01

    Background Long-term intake of long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs), especially eicosapentaenoic acid (EPA) is associated with a low risk for cardiovascular disease. Phase-contrast cine cardiovascular magnetic resonance (PC cine CMR) can assess coronary flow reserve (CFR). The present study investigates the relationship between CFR evaluated by PC cine CMR and the serum EPA. Methods We studied 127 patients (male, 116 (91%); mean age, 72.2 ± 7.4 years) with known or suspected coronary artery disease (CAD). X-ray coronary angiography revealed no significant coronary arterial stenoses (defined as luminal diameter reduction ≥50% on quantitative coronary angiogram (QCA) analysis) in all study participants. Breath-hold PC cine CMR images of the coronary sinus (CS) were acquired to assess blood flow of the CS both at rest and during adenosine triphosphate (ATP) infusion. We calculated CFR as CS blood flow during ATP infusion divided by that at rest. Patients were allocated to groups according to whether they had high (n = 64, EPA ≥ 75.8 μg/mL) or low (n = 63, EPA < 75.8 μg/mL) median serum EPA. Results CFR was significantly lower in the low, than in the high EPA group (2.54 ± 1.00 vs. 2.91 ± 0.98, p = 0.038). Serum EPA positively correlated with CFR (R = 0.35, p < 0.001). We defined preserved CFR as > 2.5, which is the previously reported lower limit of normal flow reserve without obstructive CAD. Multivariate analysis revealed that EPA is an independent predictor of CFR > 2.5 (odds ratio, 1.01; 95% confidence interval, 1.00 – 1.02, p = 0.008). Conclusions The serum EPA is significantly correlated with CFR in CAD patients without significant coronary artery stenosis. PMID:24359564

  3. Precession electron diffraction – a topical review

    PubMed Central

    Midgley, Paul A.; Eggeman, Alexander S.

    2015-01-01

    In the 20 years since precession electron diffraction (PED) was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis. PMID:25610633

  4. Solutions to the relativistic precession model

    NASA Astrophysics Data System (ADS)

    Ingram, Adam; Motta, Sara

    2014-11-01

    The relativistic precession model (RPM) can be used to obtain a precise measurement of the mass and spin of a black hole when the appropriate set of quasi-periodic oscillations is detected in the power-density spectrum of an accreting black hole. However, in previous studies, the solution of the RPM equations could be obtained only through numerical methods at a price of an intensive computational effort. Here, we demonstrate that the RPM system of equations can be solved analytically, drastically reducing the computational load, now limited to the Monte Carlo simulation necessary to estimate the uncertainties. The analytical method not only provides an easy solution to the RPM system when three oscillations are detected, but in all the cases where the detection of two simultaneous oscillations is coupled with an independent mass measurement. We also present a computationally inexpensive method to place limits on the black hole mass and spin when only two oscillations are observed.

  5. Precession, Nutation and Wobble of the Earth

    NASA Astrophysics Data System (ADS)

    Dehant, V.; Mathews, P. M.

    2015-04-01

    Covering both astronomical and geophysical perspectives, this book describes changes in the Earth's orientation, specifically precession and nutation, and how they are observed and computed in terms of tidal forcing and models of the Earth's interior. Following an introduction to key concepts and elementary geodetic theory, the book describes how precise measurements of the Earth's orientation are made using observations of extra-galactic radio-sources by Very Long Baseline Interferometry techniques. It demonstrates how models are used to accurately pinpoint the location and orientation of the Earth with reference to the stars and how to determine variations in its rotation speed. A theoretical framework is also presented that describes the role played by the structure and properties of the Earth's deep interior. Incorporating suggestions for future developments in nutation theory for the next generation models, this book is ideal for advanced-level students and researche! rs in solid Earth geophysics, planetary science and astronomy.

  6. Precession electron diffraction - a topical review.

    PubMed

    Midgley, Paul A; Eggeman, Alexander S

    2015-01-01

    In the 20 years since precession electron diffraction (PED) was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis. PMID:25610633

  7. Quantitative myocardial perfusion imaging by cardiovascular magnetic resonance and positron emission tomography.

    PubMed

    Bratis, K; Mahmoud, I; Chiribiri, A; Nagel, E

    2013-10-01

    Recent studies have demonstrated that a detailed knowledge of the extent of angiographic coronary artery disease (CAD) is not a prerequisite for clinical decision making, and the clinical management of patients with CAD is more and more focused towards the identification of myocardial ischemia and the quantification of ischemic burden. In this view, non-invasive assessment of ischemia and in particular stress imaging techniques are emerging as preferred and non-invasive options. A quantitative assessment of regional myocardial perfusion can provide an objective estimate of the severity of myocardial injury and may help clinicians to discriminate regions of the heart that are at increased risk for myocardial infarction. Positron emission tomography (PET) has established itself as the reference standard for myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) quantification. Cardiac magnetic resonance (CMR) is increasingly used to measure MBF and MPR by means of first-pass signals, with a well-defined diagnostic performance and prognostic value. The aim of this article is to review the currently available evidence on the use of both PET and CMR for quantification of MPR, with particular attention to the studies that directly compared these two diagnostic methods. PMID:23868071

  8. ECG-based gating in ultra high field cardiovascular magnetic resonance using an independent component analysis approach

    PubMed Central

    2013-01-01

    Background In Cardiovascular Magnetic Resonance (CMR), the synchronization of image acquisition with heart motion is performed in clinical practice by processing the electrocardiogram (ECG). The ECG-based synchronization is well established for MR scanners with magnetic fields up to 3 T. However, this technique is prone to errors in ultra high field environments, e.g. in 7 T MR scanners as used in research applications. The high magnetic fields cause severe magnetohydrodynamic (MHD) effects which disturb the ECG signal. Image synchronization is thus less reliable and yields artefacts in CMR images. Methods A strategy based on Independent Component Analysis (ICA) was pursued in this work to enhance the ECG contribution and attenuate the MHD effect. ICA was applied to 12-lead ECG signals recorded inside a 7 T MR scanner. An automatic source identification procedure was proposed to identify an independent component (IC) dominated by the ECG signal. The identified IC was then used for detecting the R-peaks. The presented ICA-based method was compared to other R-peak detection methods using 1) the raw ECG signal, 2) the raw vectorcardiogram (VCG), 3) the state-of-the-art gating technique based on the VCG, 4) an updated version of the VCG-based approach and 5) the ICA of the VCG. Results ECG signals from eight volunteers were recorded inside the MR scanner. Recordings with an overall length of 87 min accounting for 5457 QRS complexes were available for the analysis. The records were divided into a training and a test dataset. In terms of R-peak detection within the test dataset, the proposed ICA-based algorithm achieved a detection performance with an average sensitivity (Se) of 99.2%, a positive predictive value (+P) of 99.1%, with an average trigger delay and jitter of 5.8 ms and 5.0 ms, respectively. Long term stability of the demixing matrix was shown based on two measurements of the same subject, each being separated by one year, whereas an averaged detection

  9. P03-based precession-nutation matrices

    NASA Astrophysics Data System (ADS)

    Wallace, P.; Capitaine, N.

    2006-10-01

    The IAU WG on precession and the ecliptic has recommended the adoption of the P03 models of Capitaine et al. (2003). We discuss methods for generating the rotation matrices that transform celestial to terrestrial coordinates, taking into account frame bias (B), P03 precession (P), P03-adjusted IAU 2000A nutation (N) and Earth rotation. The NPB portion can refer either to the equinox or the celestial intermediate origin (CIO), requiring either the Greenwich sidereal time (GST) or the Earth rotation angle (ERA) as the measure of Earth rotation. The equinox based NPB transformation can be formed using various sequences of rotations, while the CIO based transformation can be formed using series for the X, Y coordinates of the celestial intermediate pole (CIP) and for the CIO locator s; also, either matrix can be computing using series for the x, y, z components of the "rotation vector". Common to both methods is the CIP, which forms the bottom row of the transformation matrix. In the case of the CIO based transformation, the CIO is the top row of the NPB matrix, whereas in the equinox based case it enters via the GST formulation in the form of the equation of the origins (EO). The EO is the difference between ERA and GST and equivalently the distance between the CIO and equinox. The choice of method is dictated by considerations of internal consistency, flexibility and ease of use; the different ways agree at the level of a few microarcseconds over several centuries, and consume similar computing resources.

  10. Precession of the isolated neutron star PSR B1828-11

    NASA Astrophysics Data System (ADS)

    Akgün, Taner; Link, Bennett; Wasserman, Ira

    2006-01-01

    Stairs, Lyne & Shemar have found that the arrival-time residuals from PSR B1828-11 vary periodically with a period ~500 d. This behaviour can be accounted for by precession of the radio pulsar, an interpretation that is reinforced by the detection of variations in its pulse profile on the same time-scale. Here, we model the period residuals from PSR B1828-11 in terms of precession of a triaxial rigid body. We include two contributions to the residuals: (i) the geometric effect, which arises because the times at which the pulsar emission beam points towards the observer varies with precession phase; and (ii) the spin-down contribution, which arises from any dependence of the spin-down torque acting on the pulsar on the angle between its spin and magnetic axes. We use the data to probe numerous properties of the pulsar, most notably its shape, and the dependence of its spin-down torque on , for which we assume the sum of a spin-aligned component (with a weight 1 -a) and a dipolar component perpendicular to the magnetic beam axis (weight a), rather than the vacuum dipole torque (a= 1). We find that a variety of shapes are consistent with the residuals, with a slight statistical preference for a prolate star. Moreover, a range of torque possibilities fit the data equally well, with no strong preference for the vacuum model. In the case of a prolate star, we find evidence for an angle-dependent spin-down torque. Our results show that the combination of geometrical and spin-down effects associated with precession can account for the principal features of the timing behaviour of PSR B1828-11, without fine tuning of the parameters.

  11. Three-Directional Evaluation of Mitral Flow in the Rat Heart by Phase-Contrast Cardiovascular Magnetic Resonance

    PubMed Central

    Skårdal, Kristine; Espe, Emil KS; Zhang, Lili; Aronsen, Jan Magnus; Sjaastad, Ivar

    2016-01-01

    Purpose Determination of mitral flow is an important aspect in assessment of cardiac function. Traditionally, mitral flow is measured by Doppler echocardiography which suffers from several challenges, particularly related to the direction and the spatial inhomogeneity of flow. These challenges are especially prominent in rodents. The purpose of this study was to establish a cardiovascular magnetic resonance (CMR) protocol for evaluation of three-directional mitral flow in a rodent model of cardiac disease. Materials and Methods Three-directional mitral flow were evaluated by phase contrast CMR (PC-CMR) in rats with aortic banding (AB) (N = 7) and sham-operated controls (N = 7). Peak mitral flow and deceleration rate from PC-CMR was compared to conventional Doppler echocardiography. The accuracy of PC-CMR was investigated by comparison of spatiotemporally integrated mitral flow with left ventricular stroke volume assessed by cine CMR. Results PC-CMR portrayed the spatial distribution of mitral flow and flow direction in the atrioventricular plane throughout diastole. Both PC-CMR and echocardiography demonstrated increased peak mitral flow velocity and higher deceleration rate in AB compared to sham. Comparison with cine CMR revealed that PC-CMR measured mitral flow with excellent accuracy. Echocardiography presented significantly lower values of flow compared to PC-CMR. Conclusions For the first time, we show that PC-CMR offers accurate evaluation of three-directional mitral blood flow in rodents. The method successfully detects alterations in the mitral flow pattern in response to cardiac disease and provides novel insight into the characteristics of mitral flow. PMID:26930073

  12. Cine and tagged cardiovascular magnetic resonance imaging in normal rat at 1.5 T: a rest and stress study

    PubMed Central

    Daire, Jean-Luc; Jacob, Jean-Pascal; Hyacinthe, Jean-Noel; Croisille, Pierre; Montet-Abou, Karin; Richter, Sophie; Botsikas, Diomidis; Lepetit-Coiffé, Matthieu; Morel, Denis; Vallée, Jean-Paul

    2008-01-01

    Background The purpose of this study was to measure regional contractile function in the normal rat using cardiac cine and tagged cardiovascular magnetic resonance (CMR) during incremental low doses of dobutamine and at rest. Methods Five rats were investigated for invasive left ventricle pressure measurements and five additional rats were imaged on a clinical 1.5 T MR system using a cine sequence (11–20 phases per cycle, 0.28/0.28/2 mm) and a C-SPAMM tag sequence (18–25 phases per cycle, 0.63/1.79/3 mm, tag spacing 1.25 mm). For each slice, wall thickening (WT) and circumferential strains (CS) were calculated at rest and at stress (2.5, 5 and 10 μg/min/kg of dobutamine). Results Good cine and tagged images were obtained in all the rats even at higher heart rate (300–440 bpm). Ejection fraction and left ventricular (LV) end-systolic volume showed significant changes after each dobutamine perfusion dose (p < 0.001). Tagged CMR had the capacity to resolve the CS transmural gradient and showed a significant increase of both WT and CS at stress compared to rest. Intra and interobserver study showed less variability for the tagged technique. In rats in which a LV catheter was placed, dobutamine produced a significant increase of heart rate, LV dP/dtmax and LV pressure significantly already at the lowest infusion dose. Conclusion Robust cardiac cine and tagging CMR measurements can be obtained in the rat under incremental dobutamine stress using a clinical 1.5 T MR scanner. PMID:18980685

  13. Potential clinical impact of cardiovascular magnetic resonance assessment of ejection fraction on eligibility for cardioverter defibrillator implantation

    PubMed Central

    2012-01-01

    Background For the primary prevention of sudden cardiac death, guidelines provide left ventricular ejection fraction (EF) criteria for implantable cardioverter defibrillator (ICD) placement without specifying the technique by which it should be measured. We sought to investigate the potential impact of performing cardiovascular magnetic resonance (CMR) for EF on ICD eligibility. Methods The study population consisted of patients being considered for ICD implantation who were referred for EF assessment by CMR. Patients who underwent CMR within 30 days of echocardiography were included. Echocardiographic EF was determined by Simpson’s biplane method and CMR EF was measured by Simpson’s summation of discs method. Results Fifty-two patients (age 62±15 years, 81% male) had a mean EF of 38 ± 14% by echocardiography and 35 ± 14% by CMR. CMR had greater reproducibility than echocardiography for both intra-observer (ICC, 0.98 vs 0.94) and inter-observer comparisons (ICC 0.99 vs 0.93). The limits of agreement comparing CMR and echocardiographic EF were – 16 to +10 percentage points. CMR resulted in 11 of 52 (21%) and 5 of 52 (10%) of patients being reclassified regarding ICD eligibility at the EF thresholds of 35 and 30% respectively. Among patients with an echocardiographic EF of between 25 and 40%, 9 of 22 (41%) were reclassified by CMR at either the 35 or 30% threshold. Echocardiography identified only 1 of the 6 patients with left ventricular thrombus noted incidentally on CMR. Conclusions CMR resulted in 21% of patients being reclassified regarding ICD eligibility when strict EF criteria were used. In addition, CMR detected unexpected left ventricular thrombus in almost 10% of patients. Our findings suggest that the use of CMR for EF assessment may have a substantial impact on management in patients being considered for ICD implantation. PMID:23043729

  14. A Novel Approach to Early Detection of Doxorubicin Cardiotoxicity using Gadolinium Enhanced Cardiovascular Magnetic Resonance Imaging in an Experimental Model

    PubMed Central

    Lightfoot, James C.; D'Agostino, Ralph B.; Hamilton, Craig A; Jordan, Jennifer; Torti, Frank M.; Kock, Nancy D.; Jordan, James; Workman, Susan; Hundley, W Gregory

    2011-01-01

    Background To determine if cardiovascular magnetic resonance (CMR) measures of gadolinium (Gd) signal intensity (SI) within the left ventricular (LV) myocardium are associated with future changes in LV ejection fraction (LVEF) after receipt of doxorubicin (DOX). Methods and Results Forty Sprague-Dawley rats were divided into 3 groups scheduled to receive weekly intravenous doses of: normal saline (NS) (n=7), 1.5 mg/kg DOX (n=19), or 2.5 mg/kg DOX (n=14). MR determinations of LVEF and myocardial Gd-SI were performed before and then at 2, 4, 7, and 10 weeks after DOX initiation. During treatment, animals were sacrificed at different time points so that histopathological assessments of the LV myocardium could be obtained. Within group analyses were performed to examine time-dependent relationships between Gd-SI and primary events (a deterioration in LVEF or an unanticipated death). Six of 19 animals receiving 1.5 mg/kg of DOX and 10/14 animals receiving 2.5 mg/kg of DOX experienced a primary event; no NS animals experienced a primary event. In animals with a primary event, histopathological evidence of myocellular vacuolization occurred (p=0.04), and the Gd-SI was elevated relative to baseline at the time of the event (p<0.0001) and during the measurement period prior to the event (p=0.0001). In all animals (including NS) without an event, measures of Gd-SI did not differ from baseline. Conclusions After DOX, low serial measures of Gd-SI predict an absence of a LVEF drop or unanticipated death. An increase in Gd-SI after DOX forecasts a subsequent drop in LVEF as well as histopathologic evidence of intracellular vacuolization consistent with DOX cardiotoxicity. PMID:20622140

  15. Forward and Backward Precession of a Vertical Anisotropically Supported Rotor

    NASA Astrophysics Data System (ADS)

    Muszynska, A.

    1996-04-01

    This paper presents the analytical and experimental study of a vertical, overhung imbalanced rotor supported by flexible, anisotropic bearings. The results show that existence of imbalance and shaft bow causes the synchronous forced precession of the rotor to be forward (below the first value of split balance resonance and above the second value of the split balance resonance) or backward (between the two values of the split resonance). This phenomenon is classical. The new result consists of exploring the existence of forward precession of the inboard and midspan rotor sections while the outboard disk is precessing backward. The sensitivity analysis shows which system parameters are mainly responsible for this apparently bizarre phenomenon.

  16. Refinements on precession, nutation, and wobble of the Earth

    NASA Astrophysics Data System (ADS)

    Dehant, V. Folgueira M.; Puica, M.; Van Hoolst, T.

    2015-08-01

    Most of the essential elements of the theory of nutation of the nonrigid Earth have been presented in the IAU adopted model MHB2000 (Mathews et al., 2002) considering an ellipsoidal rotating Earth, with a solid inner core, a liquid outer core, and an ellipsoidal inelastic mantle, and with a magnetic field. However in the meantime, the observed nutation amplitudes have been redetermined with a better precision. A number of relatively small significant effects have to be taken into account before one can expect to have a theoretical framework that can yield numerical results matching the precession and nutation observations. The adopted model already accounts for the existence of a geomagnetic field passing through the mantle and the fluid core regions and beyond. The model MHB2000 considers an electromagnetic torque generated by this field when the core and the mantle are moving relative to each other, which can in turn affect some nutation amplitudes (both in phase and out-of-phase) to the extent of a few hundreds of microarcsecond (μas), playing thus a significant role. The paper revisits the last adopted model in order to incorporate potential additional coupling effects at the core-mantle boundary, that can be at an observable level, such as the existence of a non-hydrostatic core-mantle boundary topography, the viscosity of the liquid core, the existence of stratification in the core, the existence of boundary layers at both sides of the core-mantle boundary.

  17. The Equivalence of Precession Phenomena in Metric Theories of Gravity

    NASA Technical Reports Server (NTRS)

    Krisher, Timothy P.

    1996-01-01

    A simple argument is presented that demonstrates clearly, without the need for detailed calculation, how geodetic precession of a gyroscope and the effect of fram-draggin are fundamentally equivalent.

  18. Suppression of vortex core precession in a swirling reacting flow

    NASA Astrophysics Data System (ADS)

    Litvinov, I. V.; Nazarov, A. V.; Shtork, S. I.

    2016-03-01

    The influence of combustion effect on unsteady vortex structure in the form of precessing vortex core was studied using the non-intrusive method of laser Doppler anemometry and special procedure of extracting the non-axisymmetric mode of flow fluctuations. The studies show that combustion has a significant effect on the parameters of such a core, reducing the amplitude (vortex deviation from the burner center) and increasing precession frequency. At the same time, the acoustic sensors detect almost an order reduction in the level of pressure pulsations generated by the precessing vortex core. Moreover, distributions of tangential velocity fluctuations and cross-correlation analysis show that vortex precession is quite pronounced even under the combustion conditions, bringing a significant coherent component to distributions of velocity fluctuations.

  19. GRAVITATIONAL WAVES OF JET PRECESSION IN GAMMA-RAY BURSTS

    SciTech Connect

    Sun Mouyuan; Liu Tong; Gu Weimin; Lu Jufu

    2012-06-10

    The physical nature of gamma-ray bursts (GRBs) is believed to involve an ultra-relativistic jet. The observed complex structure of light curves motivates the idea of jet precession. In this work, we study the gravitational waves of jet precession based on neutrino-dominated accretion disks around black holes, which may account for the central engine of GRBs. In our model, the jet and the inner part of the disk may precess along with the black hole, which is driven by the outer part of the disk. Gravitational waves are therefore expected to be significant from this black-hole-inner-disk precession system. By comparing our numerical results with the sensitivity of some detectors, we find that it is possible for DECIGO and BBO to detect such gravitational waves, particularly for GRBs in the Local Group.

  20. Determination of the spin-lifetime anisotropy in graphene using oblique spin precession

    PubMed Central

    Raes, Bart; Scheerder, Jeroen E.; Costache, Marius V.; Bonell, Frédéric; Sierra, Juan F.; Cuppens, Jo; Van de Vondel, Joris; Valenzuela, Sergio O.

    2016-01-01

    We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields. PMID:27157318

  1. Determination of the spin-lifetime anisotropy in graphene using oblique spin precession.

    PubMed

    Raes, Bart; Scheerder, Jeroen E; Costache, Marius V; Bonell, Frédéric; Sierra, Juan F; Cuppens, Jo; Van de Vondel, Joris; Valenzuela, Sergio O

    2016-01-01

    We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields. PMID:27157318

  2. Magnetohydrodynamic instabilities in rotating and precessing sheared flows: An asymptotic analysis

    NASA Astrophysics Data System (ADS)

    Salhi, A.; Lehner, T.; Cambon, C.

    2010-07-01

    Linear magnetohydrodynamic instabilities are studied analytically in the case of unbounded inviscid and electrically conducting flows that are submitted to both rotation and precession with shear in an external magnetic field. For given rotation and precession the possible configurations of the shear and of the magnetic field and their interplay are imposed by the “admissibility” condition (i.e., the base flow must be a solution of the magnetohydrodynamic Euler equations): we show that an “admissible” basic magnetic field must align with the basic absolute vorticity. For these flows with elliptical streamlines due to precession we undertake an analytical stability analysis for the corresponding Floquet system, by using an asymptotic expansion into the small parameter ɛ (ratio of precession to rotation frequencies) by a method first developed in the magnetoelliptical instabilities study by Lebovitz and Zweibel [Astrophys. J. 609, 301 (2004)]10.1086/420972. The present stability analysis is performed into a suitable frame that is obtained by a systematic change of variables guided by symmetry and the existence of invariants of motion. The obtained Floquet system depends on three parameters: ɛ , η (ratio of the cyclotron frequency to the rotation frequency) and χ=cosα , with α being a characteristic angle which, for circular streamlines, ɛ=0 , identifies with the angle between the wave vector and the axis of the solid body rotation. We look at the various (centrifugal or precessional) resonant couplings between the three present modes: hydrodynamical (inertial), magnetic (Alfvén), and mixed (magnetoinertial) modes by computing analytically to leading order in ɛ the instabilities by estimating their threshold, growth rate, and maximum growth rate and their bandwidths as functions of ɛ , η , and χ . We show that the subharmonic “magnetic” mode appears only for η>5/2 and at large η (≫1) the maximal growth rate of both the

  3. Experimental study of fluid flows in a precessing cylindrical annulus

    NASA Astrophysics Data System (ADS)

    Lin, Yufeng; Noir, Jerome; Jackson, Andrew

    2014-04-01

    The flow inside a precessing fluid cavity has been given particular attention since the end of the 19th century in geophysical and industrial contexts. The present study aims at shedding light on the underlying mechanism by which the flow inside a precessing cylindrical annulus transitions from laminar to multiple scale complex structures. We address this problem experimentally using ultrasonic Doppler velocimetry to diagnose the fluid velocity in a rotating and precessing cylindrical annulus. When precession is weak, the flow can be described as a superposition of forced inertial modes. Above a critical value of the precession rate, the forced flow couples with two free inertial modes satisfying triadic resonance conditions, leading to the classical growth and collapse. Using a Bayesian approach, we extract the wavenumber, frequency, growth rate, and amplitude of each mode involved in the instability. In some cases, we observe for the first time ever experimentally two pairs of free modes coexisting with the forced flow. At larger precession rates, we do not observe triadic resonance any more, instead we observe several harmonics whose frequencies are integer multiples of the rotation frequency.

  4. Pulsar state switching, timing noise and free precession

    NASA Astrophysics Data System (ADS)

    Jones, D. I.

    2012-03-01

    Recent radio pulsar observations have shown that a number of pulsars display interesting long-term periodicities in their spin-down rates. At least some of these pulsars also undergo sharp changes in pulse profile. This has been convincingly attributed to the stars abruptly switching between two different magnetospheric states. The sharpness of these transitions has been taken as evidence against free precession as the mechanism behind the long-term variations. We argue that such a conclusion is premature. By performing a simple best-fitting analysis to the data, we show that the relationship between the observed spin and modulation periods is of approximately the correct form to be accounted for by the free precession of a population of neutron stars with strained crusts, the level of strain being similar in all of the stars, and consistent with the star retaining a memory of a former faster rotation rate. We also provide an argument as to why abrupt magnetospheric changes can occur in precessing stars, and how such changes would serve to magnify the effect of precession in the timing data, making the observation of the precession more likely in those stars where such switching occurs. We describe how future observations could further test the precession hypothesis advanced here.

  5. Single-spin precessing gravitational waveform in closed form

    NASA Astrophysics Data System (ADS)

    Lundgren, Andrew; O'Shaughnessy, R.

    2014-02-01

    In coming years, gravitational-wave detectors should find black hole-neutron star (BH-NS) binaries, potentially coincident with astronomical phenomena like short gamma ray bursts. These binaries are expected to precess. Gravitational-wave science requires a tractable model for precessing binaries, to disentangle precession physics from other phenomena like modified strong field gravity, tidal deformability, or Hubble flow; and to measure compact object masses, spins, and alignments. Moreover, current searches for gravitational waves from compact binaries use templates where the binary does not precess and are ill-suited for detection of generic precessing sources. In this paper we provide a closed-form representation of the single-spin precessing waveform in the frequency domain by reorganizing the signal as a sum over harmonics, each of which resembles a nonprecessing waveform. This form enables simple analytic calculations of the Fisher matrix for use in template bank generation and coincidence metrics, and jump proposals to improve the efficiency of Markov chain Monte Carlo sampling. We have verified that for generic BH-NS binaries, our model agrees with the time-domain waveform to 2%. Straightforward extensions of the derivations outlined here (and provided in full online) allow higher accuracy and error estimates.

  6. Role of Perfusion at Rest in the Diagnosis of Myocardial Infarction Using Vasodilator Stress Cardiovascular Magnetic Resonance.

    PubMed

    Patel, Mita B; Mor-Avi, Victor; Kawaji, Keigo; Nathan, Sandeep; Kramer, Christopher M; Lang, Roberto M; Patel, Amit R

    2016-04-01

    In clinical practice, perfusion at rest in vasodilator stress single-photon emission computed tomography is commonly used to confirm myocardial infarction (MI) and ischemia and to rule out artifacts. It is unclear whether perfusion at rest carries similar information in cardiovascular magnetic resonance (CMR). We sought to determine whether chronic MI is associated with abnormal perfusion at rest on CMR. We compared areas of infarct and remote myocardium in 31 patients who underwent vasodilator stress CMR (1.5 T), had MI confirmed by late gadolinium enhancement (LGE scar), and coronary angiography within 6 months. Stress perfusion imaging during gadolinium first pass was followed by reversal with aminophylline (75 to 125 mg), rest perfusion, and LGE imaging. Resting and peak-stress time-intensity curves were used to obtain maximal upslopes (normalized by blood pool upslopes), which were compared between infarcted and remote myocardial regions of interest. At rest, there was no significant difference between the slopes in the regions of interest supplied by arteries with and without stenosis >70% (0.31 ± 0.16 vs 0.26 ± 0.15 1/s), irrespective of LGE scar. However, at peak stress, we found significant differences (0.20 ± 0.11 vs 0.30 ± 0.22 1/s; p <0.05), reflecting the expected stress-induced ischemia. Similarly, at rest, there was no difference between infarcted and remote myocardium (0.27 ± 0.14 vs 0.30 ± 0.17 1/s), irrespective of stenosis, but significant differences were seen during stress (0.21 ± 0.16 vs 0.28 ± 0.18 1/s; p <0.001), reflecting inducible ischemia. In conclusion, abnormalities in myocardial perfusion at rest associated with chronic MI are not reliably detectable on CMR images. Accordingly, unlike single-photon emission computed tomography, normal CMR perfusion at rest should not be used to rule out chronic MI. PMID:26830261

  7. Cardiovascular magnetic resonance by non contrast T1-mapping allows assessment of severity of injury in acute myocardial infarction

    PubMed Central

    2012-01-01

    Background Current cardiovascular magnetic resonance (CMR) methods, such as late gadolinium enhancement (LGE) and oedema imaging (T2W) used to depict myocardial ischemia, have limitations. Novel quantitative T1-mapping techniques have the potential to further characterize the components of ischemic injury. In patients with myocardial infarction (MI) we sought to investigate whether state-of the art pre-contrast T1-mapping (1) detects acute myocardial injury, (2) allows for quantification of the severity of damage when compared to standard techniques such as LGE and T2W, and (3) has the ability to predict long term functional recovery. Methods 3T CMR including T2W, T1-mapping and LGE was performed in 41 patients [of these, 78% were ST elevation MI (STEMI)] with acute MI at 12-48 hour after chest pain onset and at 6 months (6M). Patients with STEMI underwent primary PCI prior to CMR. Assessment of acute regional wall motion abnormalities, acute segmental damaged fraction by T2W and LGE and mean segmental T1 values was performed on matching short axis slices. LGE and improvement in regional wall motion at 6M were also obtained. Results We found that the variability of T1 measurements was significantly lower compared to T2W and that, while the diagnostic performance of acute T1-mapping for detecting myocardial injury was at least as good as that of T2W-CMR in STEMI patients, it was superior to T2W imaging in NSTEMI. There was a significant relationship between the segmental damaged fraction assessed by either by LGE or T2W, and mean segmental T1 values (P < 0.01). The index of salvaged myocardium derived by acute T1-mapping and 6M LGE was not different to the one derived from T2W (P = 0.88). Furthermore, the likelihood of improvement of segmental function at 6M decreased progressively as acute T1 values increased (P < 0.0004). Conclusions In acute MI, pre-contrast T1-mapping allows assessment of the extent of myocardial damage. T1-mapping might become an important

  8. Assessment of global myocardial perfusion reserve using cardiovascular magnetic resonance of coronary sinus flow at 3 Tesla

    PubMed Central

    2014-01-01

    Background Despite increasing clinical use, there is limited data regarding regadenoson in stress perfusion cardiovascular magnetic resonance (CMR). In particular, given its long half-life the optimal stress protocol remains unclear. Although Myocardial Perfusion Reserve (MPR) may provide additive prognostic information, current techniques for its measurement are cumbersome and challenging for routine clinical practice. The aims of this study were: 1) To determine the feasibility of MPR quantification during regadenoson stress CMR by measurement of Coronary Sinus (CS) flow; and 2) to investigate the role of aminophylline reversal during regadenoson stress-CMR. Methods 117 consecutive patients with possible myocardial ischemia were prospectively enrolled. Perfusion imaging was performed at 1 minute and 15 minutes after administration of 0.4 mg regadenoson. A subgroup of 41 patients was given aminophylline (100 mg) after stress images were acquired. CS flow was measured using phase-contrast imaging at baseline (pre CS flow), and immediately after the stress (peak CS flow) and rest (post CS flow) perfusion images. Results CS flow measurements were obtained in 92% of patients with no adverse events. MPR was significantly underestimated when calculated as peak CS flow/post CS flow as compared to peak CS flow/pre CS flow (2.43 ± 0.20 vs. 3.28 ± 0.32, p = 0.03). This difference was abolished when aminophylline was administered (3.35 ± 0.44 vs. 3.30 ± 0.52, p = 0.95). Impaired MPR (peak CS flow/pre CS flow <2) was associated with advanced age, diabetes, current smoking and higher Framingham risk score. Conclusions Regadenoson stress CMR with MPR measurement from CS flow can be successfully performed in most patients. This measurement of MPR appears practical to perform in the clinical setting. Residual hyperemia is still present even 15 minutes after regadenoson administration, at the time of resting-perfusion acquisition, and is completely

  9. Comparison of different electrocardiographic scoring systems for detection of any previous myocardial infarction as assessed with cardiovascular magnetic resonance imaging.

    PubMed

    Jaarsma, Caroline; Bekkers, Sebastiaan C; Haidari, Zaki; Smulders, Martijn W; Nelemans, Patricia J; Gorgels, Anton P; Crijns, Harry J; Wildberger, Joachim E; Schalla, Simon

    2013-10-15

    Although electrocardiography is frequently used as an initial test to detect or rule out previous myocardial infarction (MI), the diagnostic performance of commonly used electrocardiographic scoring systems is not well described. We aimed to determine the diagnostic accuracy of (1) the Universal Definition, (2) Minnesota ECG Code (MC), (3) Selvester QRS Score, and (4) assessment by cardiologists using late gadolinium enhancement cardiovascular magnetic resonance imaging as the reference standard. Additionally, the effect of electrocardiographic patterns and infarct characteristics on detecting previous MI was evaluated. The 3-month follow-up electrocardiograms of 78 patients with first-time reperfused ST elevation MI were pooled with electrocardiograms of 36 healthy controls. All 114 electrocardiograms were randomly analyzed, blinded to clinical and LGE-CMR data. The sensitivity of the Universal Definition, MC, Selvester QRS Score, and cardiologists to detect previous MI was 33%, 79%, 90%, and 67%, respectively; specificity 97%, 72%, 31%, and 89%, respectively; diagnostic accuracy 54%, 77%, 71%, and 74%, respectively. Probability of detecting MI by cardiologists increased with an increasing number (odds ratio [OR] 2.00, 95% confidence interval [CI] 1.30 to 3.09), width (OR 1.02, 95% CI 1.01 to 1.03), and depth (OR 1.16, 95% CI 1.07 to 1.27) of Q waves as well as increasing infarct size (OR 1.15, 95% CI 1.06 to 1.25) and transmurality (OR 1.05, 95% CI 1.01 to 1.08; p <0.05 for all). The time-consuming MC and rapid visual assessment by cardiologists achieved the best and similar diagnostic accuracies to detect previous MI. The diagnostic performance of all 4 electrocardiographic scoring systems was modest and related to the number, depth, and width of Q waves as well as increasing infarct size and transmurality. In conclusion, the exclusion of a previous MI based solely on electrocardiographic findings should be done with caution. Future studies are needed to define

  10. Guidelines and protocols for cardiovascular magnetic resonance in children and adults with congenital heart disease: SCMR expert consensus group on congenital heart disease

    PubMed Central

    2013-01-01

    Cardiovascular magnetic resonance (CMR) has taken on an increasingly important role in the diagnostic evaluation and pre-procedural planning for patients with congenital heart disease. This article provides guidelines for the performance of CMR in children and adults with congenital heart disease. The first portion addresses preparation for the examination and safety issues, the second describes the primary techniques used in an examination, and the third provides disease-specific protocols. Variations in practice are highlighted and expert consensus recommendations are provided. Indications and appropriate use criteria for CMR examination are not specifically addressed. PMID:23763839

  11. Balanced steady state-free precession (b-SSFP) imaging for MRCP: techniques and applications.

    PubMed

    Glockner, James F; Lee, Christine U

    2014-12-01

    Balanced steady state-free precession (b-SSFP) pulse sequences have a number of properties which can be useful in magnetic resonance cholangiopancreatography (MRCP), including short acquisition times, high signal-to-noise ratios, and T2/T1 contrast weighting. The utility and versatility of b-SSFP sequences for MRCP imaging are probably underappreciated, and this pictorial essay briefly discusses benefits and limitations of 2D and 3D b-SSFP techniques used in place of or in addition to conventional single-shot fast spin echo or 3D fast spin echo acquisitions and illustrates their appearance in several clinical cases. PMID:24811765

  12. Perihelion precession, polar ice and global warming

    NASA Astrophysics Data System (ADS)

    Steel, Duncan

    2013-03-01

    The increase in mean global temperature over the past 150 years is generally ascribed to human activities, in particular the rises in the atmospheric mixing ratios of carbon dioxide and other greenhouse gases since the Industrial Revolution began. Whilst it is thought that ice ages and interglacial periods are mainly initiated by multi-millennial variations in Earth's heliocentric orbit and obliquity, shorter-term orbital variations and consequent observable climatic effects over decadal/centurial timescales have not been considered significant causes of contemporary climate change compared to anthropogenic influences. Here it is shown that the precession of perihelion occurring over a century substantially affects the intra-annual variation of solar radiation influx at different locations, especially higher latitudes, with northern and southern hemispheres being subject to contrasting insolation changes. This north/south asymmetry has grown since perihelion was aligned with the winter solstice seven to eight centuries ago, and must cause enhanced year-on-year springtime melting of Arctic (but not Antarctic) ice and therefore feedback warming because increasing amounts of land and open sea are denuded of high-albedo ice and snow across boreal summer and into autumn. The accelerating sequence of insolation change now occurring as perihelion moves further into boreal winter has not occurred previously during the Holocene and so would not have been observed before by past or present civilisations. Reasons are given for the significance of this process having been overlooked until now. This mechanism represents a supplementary - natural - contribution to climate change in the present epoch and may even be the dominant fundamental cause of global warming, although anthropogenic effects surely play a role too.

  13. Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic

    NASA Astrophysics Data System (ADS)

    Hilton, J. L.; Capitaine, N.; Chapront, J.; Ferrandiz, J. M.; Fienga, A.; Fukushima, T.; Getino, J.; Mathews, P.; Simon, J.-L.; Soffel, M.; Vondrak, J.; Wallace, P.; Williams, J.

    2006-03-01

    The IAU Working Group on Precession and the Equinox looked at several solutions for replacing the precession part of the IAU 2000A precession nutation model, which is not consistent with dynamical theory. These comparisons show that the (Capitaine et al., Astron. Astrophys., 412, 2003a) precession theory, P03, is both consistent with dynamical theory and the solution most compatible with the IAU 2000A nutation model. Thus, the working group recommends the adoption of the P03 precession theory for use with the IAU 2000A nutation. The two greatest sources of uncertainty in the precession theory are the rate of change of the Earth’s dynamical flattening, ΔJ 2, and the precession rates (i.e. the constants of integration used in deriving the precession). The combined uncertainties limit the accuracy in the precession theory to approximately 2 mas cent-2.

  14. Coherent spin-transfer precession switching in orthogonal spin-torque devices

    NASA Astrophysics Data System (ADS)

    Ryan, Colm; Rowlands, Graham; Pinna, Daniele; Ye, Li; Rehm, Laura; Sluka, Volker; Kent, Andy; Ohki, Thomas

    We present experimental results in concert with macrospin simulations of the switching characteristics of orthogonal spin-transfer devices incorporating an out-of-plane magnetized polarizing layer and an in-plane magnetized spin valve device at cryogenic temperatures. Switching at 3.4K between parallel and anti-parallel spin-valve states is investigated for current pulses with varying durations from 0.1 to 1.4ns to observe the averaged response of the time dependent dynamics of the spin-transfer induced precession of the magnetization. We demonstrate high speed switching at short pulse lengths, down to 100ps, and also observe ensemble decoherence effects with longer pulses. The results show that even at cryogenic temperatures finite temperature noise is still important in the dynamics of precessional switching.

  15. High spatial and temporal resolution retrospective cine cardiovascular magnetic resonance from shortened free breathing real-time acquisitions

    PubMed Central

    2013-01-01

    Background Cine cardiovascular magnetic resonance (CMR) is challenging in patients who cannot perform repeated breath holds. Real-time, free-breathing acquisition is an alternative, but image quality is typically inferior. There is a clinical need for techniques that achieve similar image quality to the segmented cine using a free breathing acquisition. Previously, high quality retrospectively gated cine images have been reconstructed from real-time acquisitions using parallel imaging and motion correction. These methods had limited clinical applicability due to lengthy acquisitions and volumetric measurements obtained with such methods have not previously been evaluated systematically. Methods This study introduces a new retrospective reconstruction scheme for real-time cine imaging which aims to shorten the required acquisition. A real-time acquisition of 16-20s per acquired slice was inputted into a retrospective cine reconstruction algorithm, which employed non-rigid registration to remove respiratory motion and SPIRiT non-linear reconstruction with temporal regularization to fill in missing data. The algorithm was used to reconstruct cine loops with high spatial (1.3-1.8 × 1.8-2.1 mm2) and temporal resolution (retrospectively gated, 30 cardiac phases, temporal resolution 34.3 ± 9.1 ms). Validation was performed in 15 healthy volunteers using two different acquisition resolutions (256 × 144/192 × 128 matrix sizes). For each subject, 9 to 12 short axis and 3 long axis slices were imaged with both segmented and real-time acquisitions. The retrospectively reconstructed real-time cine images were compared to a traditional segmented breath-held acquisition in terms of image quality scores. Image quality scoring was performed by two experts using a scale between 1 and 5 (poor to good). For every subject, LAX and three SAX slices were selected and reviewed in the random order. The reviewers were blinded to the reconstruction approach and

  16. Rotation of rigid Venus: a complete precession-nutation model

    NASA Astrophysics Data System (ADS)

    Cottereau, L.; Souchay, J.

    2009-12-01

    Context: With the increasing knowledge of the terrestrial planets due to recent space probes it is possible to model their rotation with increasing accuracy. Despite that fact, an accurate determination of Venus precession and nutation is lacking Aims: Although Venus rotation has been studied in several aspects, a full and precise analytical model of its precession-nutation motion remains to be constructed. We propose to determine this motion with up-to-date physical parameters of the planet Methods: We adopt a theoritical framework already used for a precise precession-nutation model of the Earth, based on a Hamiltonian formulation, canonical equations and an accurate development of the perturbing function due to the Sun. Results: After integrating the disturbing function and applying the canonical equations, we can evaluate the precession constant dot{Psi} and the coefficients of nutation, both in longitude and in obliquity. We get dot{Psi} = 4474farcs35/Jcy ± 66.5 , corresponding to a precession period of 28 965.10±437 years. This result, based on recent estimations of the Venus moment of inertia is significantly different from previous estimations. The largest nutation coefficient in longitude with an argument 2 LS (where LS is the longitude of the Sun) has a 2''19 amplitude and a 112.35 d period. We show that the coefficients of nutation of Venus due to its triaxiality are of the same order of amplitude as these values due to its dynamical flattening, unlike of the Earth, for which they are negligible. Conclusions: We have constucted a complete theory of the rotation of a rigid body applied to Venus, with up-to-date determinations of its physical and rotational parameters. This allowed us to set up a new and better constrained value of the Venus precession constant and to calculate its nutation coefficients for the first time.

  17. Precessive sand ripples in intense steady shear flows.

    PubMed

    Restrepo, Juan M; Moulton, Derek E; Uys, Hermann

    2011-03-01

    We describe experimental observations of fully developed, large-amplitude bars under the action of a shearing fluid. The experiments were performed in an annular tank filled with water and sheared above by a steady motor source. The same steady shearing flow can produce a variety of different erodible bed manifestations: advective or precessive bars, which refer to bar structures with global regularity and a near-steady precession velocity; interactive bars, the structure of which depends on local rearrangements, which are in turn a response to complex background topography; and dispersive bars, which are created when an initially isolated mound of sand evolves into a train of sand ripples. Of these, the most amenable to analysis are the precessive bars. For precession bars, we find that the skin depth, which is the nondimensionalized mean-field transport rate, grows exponentially as a function of the shear velocity. From this, we arrive at an analytical expression that approximates the precession speed of the bars as a function of shear velocity. We use this to obtain a formula for sediment transport rate. However, in intense flows, the bars can get large engendering boundary layer separation, leading to a different dynamic for bar formation and evolution. Numerical flow calculations over an experimentally obtained set of precessive bars are presented and show that classical parametrizations of mass flux in terms of bottom gradients have shortcomings. Within the range of shear rates considered, a quantity that does not change appreciably in time is the aspect ratio, which is defined as the ratio of the average bar amplitude, with respect to a mean depth, to the average bar length. PMID:21517492

  18. Precessive sand ripples in intense steady shear flows

    NASA Astrophysics Data System (ADS)

    Restrepo, Juan M.; Moulton, Derek E.; Uys, Hermann

    2011-03-01

    We describe experimental observations of fully developed, large-amplitude bars under the action of a shearing fluid. The experiments were performed in an annular tank filled with water and sheared above by a steady motor source. The same steady shearing flow can produce a variety of different erodible bed manifestations: advective or precessive bars, which refer to bar structures with global regularity and a near-steady precession velocity; interactive bars, the structure of which depends on local rearrangements, which are in turn a response to complex background topography; and dispersive bars, which are created when an initially isolated mound of sand evolves into a train of sand ripples. Of these, the most amenable to analysis are the precessive bars. For precession bars, we find that the skin depth, which is the nondimensionalized mean-field transport rate, grows exponentially as a function of the shear velocity. From this, we arrive at an analytical expression that approximates the precession speed of the bars as a function of shear velocity. We use this to obtain a formula for sediment transport rate. However, in intense flows, the bars can get large engendering boundary layer separation, leading to a different dynamic for bar formation and evolution. Numerical flow calculations over an experimentally obtained set of precessive bars are presented and show that classical parametrizations of mass flux in terms of bottom gradients have shortcomings. Within the range of shear rates considered, a quantity that does not change appreciably in time is the aspect ratio, which is defined as the ratio of the average bar amplitude, with respect to a mean depth, to the average bar length.

  19. Bounce Precession Fishbones in the National Spherical Tokamak Experiment

    SciTech Connect

    Eric Fredrickson; Liu Chen; Roscoe White Eric Fredrickson; Roscoe White

    2003-06-27

    Bursting modes are observed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40 (2000) 557], which are identified as bounce-precession-frequency fishbone modes. They are predicted to be important in high-current, low-shear discharges with a significant population of trapped particles with a large mean-bounce angle, such as produced by near-tangential beam injection into a large aspect-ratio device. Such a distribution is often stable to the usual precession-resonance fishbone mode. These modes could be important in ignited plasmas, driven by the trapped-alpha-particle population.

  20. A precessing relativistic jet model for 3C 449

    NASA Technical Reports Server (NTRS)

    Gower, A. C.; Hutchings, J. B.

    1982-01-01

    It is shown that the radio structure of 3C 449 can be matched with a model in which the jets are precessing and have relativistic (beta greater-than or equal to 0.4) velocities. The best-fit model implies a precession period of about 100,000 yr and a cone angle which increases with time. A similar model may be relevant for the radio structure of 3C 31. A brief discussion of the implications for 3C 449 is given.

  1. Why currently used diagnostic techniques for heart failure in rheumatoid arthritis are not enough: the challenge of cardiovascular magnetic resonance imaging.

    PubMed

    Mavrogeni, Sophie; Dimitroulas, Theodoros; Gabriel, Sherine; Sfikakis, Petros P; Pohost, Gerald M; Kitas, George D

    2014-01-01

    Rheumatoid arthritis (RA) is a multiorgan inflammatory disorder affecting approximately 1% of the population that leads to progressive joint destruction and disability. Patients with RA exhibit a high risk of cardiovascular disease, which results in premature morbidity and mortality and reduced life expectancy, when compared with the general population. Among various guises of myocardial involvement, heart failure (HF) has been recently recognized as an important contributory factor to the excess cardiovascular mortality associated with RA. HF in RA typically presents with occult clinical symptomatology and is mainly associated with structural and functional left ventricular abnormalities leading to diastolic dysfunction, while systolic myocardial performance remains well preserved. As isolated diastolic dysfunction is a predictor of high mortality, the evaluation of patients in early asymptomatic stages, when treatment targeting the heart is more likely to be effective, is of great importance. Although patient history and physical examination remain the cornerstones of HF evaluation, noninvasive imaging of cardiac chambers, coronary arteries, and great vessels may be necessary. Echocardiography, nuclear techniques, and invasive coronary angiography are already established in the routine assessment of HF; however, many aspects of HF pathophysiology in RA remain obscure, due to the limitations of currently used techniques. The capability of cardiovascular magnetic resonance (CMR) to capture early tissue changes allows timely detection of pathophysiologic phenomena of HF in RA, such as myocardial inflammation and myocardial perfusion defects, due to either macrovascular (coronary artery disease) or microvascular (vasculitis) disease. Therefore, CMR may be a useful tool for early, accurate diagnosis and research in patients with RA. PMID:25662926

  2. Triadic resonances in nonlinear simulations of a fluid flow in a precessing cylinder

    NASA Astrophysics Data System (ADS)

    Giesecke, André; Albrecht, Thomas; Gundrum, Thomas; Herault, Johann; Stefani, Frank

    2015-11-01

    We present results from three-dimensional nonlinear hydrodynamic simulations of a precession driven flow in cylindrical geometry. The simulations are motivated by a dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf in which the possibility of generating a magnetohydrodynamic dynamo will be investigated in a cylinder filled with liquid sodium and simultaneously rotating around two axes. In this study, we focus on the emergence of non-axisymmetric time-dependent flow structures in terms of inertial waves which—in cylindrical geometry—form so-called Kelvin modes. For a precession ratio (Poincaré number) {{Po}}={{{Ω }}}{{p}}/{{{Ω }}}{{c}}=0.014 considered by us, the amplitude of the forced Kelvin mode reaches up to one fourth of the rotation velocity of the cylindrical container confirming that precession provides a rather efficient flow driving mechanism even at moderate values of Po. More relevant for dynamo action might be free Kelvin modes with higher azimuthal wave number. These free Kelvin modes are triggered by nonlinear interactions and may constitute a triadic resonance with the fundamental forced mode when the height of the container matches their axial wave lengths. Our simulations reveal triadic resonances at aspect ratios close to those predicted by the linear theory except around the primary resonance of the forced mode. In that regime we still identify various free Kelvin modes, however, all of them exhibit a retrograde drift around the symmetry axis of the cylinder and none of them can be assigned to a triadic resonance. The amplitudes of the free Kelvin modes always remain below the forced mode but may reach up to 6% of the of the container’s angular velocity. The properties of the free Kelvin modes, namely their amplitude and their frequency, will be used in future simulations of the magnetic induction equation to investigate their ability to provide for dynamo action.

  3. Cardiovascular Deconditioning

    NASA Technical Reports Server (NTRS)

    Charles, John B.; Fritsch-Yelle, Janice M.; Whitson, Peggy A.; Wood, Margie L.; Brown, Troy E.; Fortner, G. William

    1999-01-01

    Spaceflight causes adaptive changes in cardiovascular function that may deleteriously affect crew health and safety. Over the last three decades, symptoms of cardiovascular changes have ranged from postflight orthostatic tachycardia and decreased exercise capacity to serious cardiac rhythm disturbances during extravehicular activities (EVA). The most documented symptom of cardiovascular dysfunction, postflight orthostatic intolerance, has affected a significant percentage of U.S. Space Shuttle astronauts. Problems of cardiovascular dysfunction associated with spaceflight are a concern to NASA. This has been particularly true during Shuttle flights where the primary concern is the crew's physical health, including the pilot's ability to land the Orbiter, and the crew's ability to quickly egress and move to safety should a dangerous condition arise. The study of astronauts during Shuttle activities is inherently more difficult than most human research. Consequently, sample sizes have been small and results have lacked consistency. Before the Extended Duration Orbiter Medical Project (EDOMP), there was a lack of normative data on changes in cardiovascular parameters during and after spaceflight. The EDOMP for the first time allowed studies on a large enough number of subjects to overcome some of these problems. There were three primary goals of the Cardiovascular EDOMP studies. The first was to establish, through descriptive studies, a normative data base of cardiovascular changes attributable to spaceflight. The second goal was to determine mechanisms of cardiovascular changes resulting from spaceflight (particularly orthostatic hypotension and cardiac rhythm disturbances). The third was to evaluate possible countermeasures. The Cardiovascular EDOMP studies involved parallel descriptive, mechanistic, and countermeasure evaluations.

  4. Cardiovascular response to physical exercise in adult patients after atrial correction for transposition of the great arteries assessed with magnetic resonance imaging

    PubMed Central

    Roest, A A W; Lamb, H J; van der Wall, E E; Vliegen, H W; van den Aardweg, J G; Kunz, P; de Roos, A; Helbing, W A

    2004-01-01

    Objective: To assess with magnetic resonance imaging (MRI) cardiovascular function in response to exercise in patients after atrial correction of transposition of the great arteries (TGA). Methods: Cardiac function at rest and during submaximal exercise was assessed with MRI in 27 patients with TGA (mean (SD) age 26 (5) years) late (23 (2) years) after atrial correction and in 14 control participants (25 (5) years old). Results: At rest, only right ventricular ejection fraction was significantly lower in patients than in controls (56 (7)% v 65 (7)%, p < 0.05). In response to exercise, increases in right ventricular end diastolic (155 (55) ml to 163 (57) ml, p < 0.05) and right ventricular end systolic volumes (70 (34) ml to 75 (36) ml, p < 0.05) were observed in patients. Furthermore, right and left ventricular stroke volumes and ejection fraction did not increase significantly in patients. Changes in right ventricular ejection fraction with exercise correlated with diminished exercise capacity (r  =  0.43, p < 0.05). Conclusions: In patients with atrially corrected TGA, MRI showed an abnormal response to exercise of both systemic right and left ventricles. Exercise MRI provides a tool for close monitoring of cardiovascular function in these patients, who are at risk for late death. PMID:15145879

  5. Precession of the Earth as the Cause of Geomagnetism: Experiments lend support to the proposal that precessional torques drive the earth's dynamo.

    PubMed

    Malkus, W V

    1968-04-19

    I have proposed that the precessional torques acting on the earth can sustain a turbulent hydromagnetic flow in the molten core. A gross balance of the Coriolis force, the Lorentz force, and the precessional force in the core fluid provided estimates of the fluid velocity and the interior magnetic field characteristic of such flow. Then these numbers and a balance of the processes responsible for the decay and regeneration of the magnetic field provided an estimate of the magnetic field external to the core. This external field is in keeping with the observations, but its value is dependent upon the speculative value for the electrical conductivity of core material. The proposal that turbulent flow due to precession can occur in the core was tested in a study of nonmagnetic laboratory flows induced by the steady precession of fluid-filled rotating spheroids. It was found that these flows exhibit both small wavelike instabilities and violent finite-amplitude instability to turbulent motion above critical values of the precession rate. The observed critical parameters indicate that a laminar flow in the core, due to the earth's precession, would have weak hydrodynamic instabilities at most, but that finite-amplitude hydromagnetic instability could lead to fully turbulent flow. PMID:17788230

  6. Magnetism of outdoor and indoor settled dust and its utilization as a tool for revealing the effect of elevated particulate air pollution on cardiovascular mortality

    NASA Astrophysics Data System (ADS)

    Jordanova, Diana; Jordanova, Neli; Lanos, Philippe; Petrov, Petar; Tsacheva, Tsenka

    2012-08-01

    Settled indoor and outdoor dusts in urban environment represent an important source of secondary pollution. Magnetic characteristics of the settled dust from six cities in Bulgaria are explored, allowing comparison on a national (country) scale. Monthly variations of the mass-specific magnetic susceptibilities (χindoor) and (χoutdoor) and calculated dust loading rates for a period of 17 months do not show seasonal variability, probably due to the dominant role of traffic-related emissions and soil-derived particles in the settled dust. The main magnetic mineral is magnetite, present as spherules and irregular particles of pseudo-single-domain grain sizes. Systematically lower remanence coercivities are obtained for outdoor dusts when compared with the corresponding indoor samples, implying that penetration of smaller particles of ambient origin indoors is the main source of the indoor dust. Mean yearly values of the ratio (χindoor/χoutdoor) for each city show statistically significant correlation with mortality due to cardiovascular diseases. This ratio reveals the source- and site-specific importance of the anthropogenically derived toxicogenic fraction. Heavy metal content of the settled dust is related to the contribution from several pollution sources (soil-derived, combustion and industrial), discriminated through analysis of principal components. SEM/EDX analyses reveal abundant presence of anthopogenic Fe-containing spherules, irregular particles and diesel exhaust conglomerates. High molecular weight polyaromatic hydrocarbons (PAH) dominate the total PAH content of the outdoor dust samples. The observed linear correlation between total PAH content, coercivity of remanence and the ratio Mrs/χ suggest either adsorption of PAHs on iron oxide particles and especially magnetite, or emission related increase in total PAH concentration along with a decrease of effective magnetic grain size of the accompanying magnetic fraction.

  7. Wigner-Thomas spin precession in polarized coincidence electronuclear scattering

    SciTech Connect

    Dmitrasinovic, V. )

    1993-05-01

    The role of the Wigner-Thomas precession in nucleon recoil polarization measurements in coincidence electron scattering processes is examined. The necessary formalism is developed within the framework of the Jacob-Wick method, and then applied to two processes: the pseudoscalar electroproduction off a nucleon and the deuteron two-body electrodisintegration.

  8. Existence of Exotic Torus Isomer States and Their Precession Motions

    NASA Astrophysics Data System (ADS)

    Ichikawa, Takatoshi; Matsuyanagi, Kenichi; Maruhn, Joachim A.; Itagaki, Naoyuki

    We systematically investigate the existence of exotic high-spin torus isomers and their precession motions for a series of N = Z even-even nuclei from 28Si to 56Ni. For this purpose, we use the cranked three-dimensional Hatree-Fock (HF) method in a systematic search for high-spin torus isomers and the three-dimensional time-dependent Hatree-Fock (TDHF) method for describing the precession motion of the torus isomer. We obtain high-spin torus isomers in 36Ar, 40Ca, 44Ti, 48Cr, and 52Fe. The emergence of the torus isomers is associated with the alignments of single-particle angular momenta, which is the same mechanism as found in 40Ca. We find that all the obtained torus isomers execute the precession motion at least two rotational periods. The moment of inertia about a perpendicular axis, which characterizes the precession motion, is found to be close to the classical rigid-body value.

  9. Variations of a Constant -- On the History of Precession

    NASA Astrophysics Data System (ADS)

    Kokott, W.

    The precession of the equinoxes, the phenomenon which defines one of the fundamental constants of astronomy, has been with us for more than two millennia. Discovered by Hipparchos who did notice a systematic difference of his star positions as compared with older observations, subsequently adopted by Ptolemaios, its correct value became the object of prolonged controversy. The apparent variability of the precession led to the superimposition of a so-called ''trepidation``, an oscillation of typically +/- 9 deg amplitude and 7000 years period, over a linear precession of only 26 arcsec per annum. This construction, finalized in the Alfonsine Tables (ca. 1280), did work for less than two centuries. The motion of the vernal equinox, at 39 arcsec p.a. too small from the outset, decreases according to this theory to 34 arcsec in the year 1475, the first year covered by the printed version of Johannes Regiomontanus' Ephemerides. Regiomontanus had to re-adjust his longitudes to the real situation, but the difficulties caused by the apparent nonlinearity did persist, leading to a prolonged debate which was finally put to rest by Tycho Brahe. Subsequent to Edmond Halley's successful derivation of a modern value of the precessional constant, again by comparing contemporary star positions with the Almagest catalogue, and Bradley's discovery of the nutation, the last long-term comparison of modern with Ptolemaic coordinates was published by Bode (1795). Shortly after, the analytical theory of precession was established by Bessel in his Fundamenta Astronomiae (1818).

  10. Do Jets Precess... or Even Move at All?

    NASA Astrophysics Data System (ADS)

    Nixon, Chris; King, Andrew

    2013-03-01

    Observations of accreting black holes often provoke suggestions that their jets precess. The precession is usually supposed to result from a combination of the Lense-Thirring effect and accretion disk viscosity. We show that this is unlikely for any type of black hole system, as the disk generally has too little angular momentum compared with a spinning hole to cause any significant movement of the jet direction across the sky on short timescales. Uncorrelated accretion events, as in the chaotic accretion picture of active galactic nuclei (AGNs), change AGN jet directions only on timescales >~ 107 yr. In this picture AGN jet directions are stable on shorter timescales, but uncorrelated with any structure of the host galaxy, as observed. We argue that observations of black hole jets precessing on timescales short compared to the accretion time would be a strong indication that the accretion disk, and not the standard Blandford-Znajek mechanism, is responsible for driving the jet. This would be particularly convincing in a tidal disruption event. We suggest that additional disk physics is needed to explain any jet precession on timescales short compared with the accretion time. Possibilities include the radiation warping instability, or disk tearing.