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Sample records for density magnetic resonance

  1. Magnetic Resonance Current Density Imaging of Chemical Processes and Reactions

    NASA Astrophysics Data System (ADS)

    Beravs, Katarina; Demš Ar, Alojz; Demsar, Franci

    1999-03-01

    Electric current density imaging was used to image conductivity changes that occur as a chemical process or reaction progresses. Feasibility was assessed in two models representing the dissolving of an ionic solid and the formation of an insoluble precipitate. In both models, temporal and spatial changes in ionic concentrations were obtained on current density images. As expected, the images showed significant signal enhancement along the ionization/dissociation sites.

  2. 3D Mapping of Polymer Crosslink Density with Magnetic Resonance Imaging

    SciTech Connect

    Herberg, J L; Gjersing, E L; Chinn, S C; Maxwell, R S

    2005-03-11

    Magnetic Resonance Imaging (MRI) techniques have been used to detect areas of low crosslink density in damaged silicone parts in an effort to develop a QA/QC protocol to be used in the development of new parts. Model materials of varying crosslink density first demonstrated the applicability of the method. Analysis of damaged pads has been shown to be clearly distinguishable by MRI. It is our belief that both the T{sub 2} weighted SPI NMR and the T{sub 2} weighted water/fat suppression MRI experiments can be used to map out the location of different cross-linking densities, ultimately determining the quality or homogeneity in polymers.

  3. Optically detected magnetic resonance of high-density ensemble of NV‑ centers in diamond

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Y.; Morishita, H.; Shimooka, T.; Tashima, T.; Kakuyanagi, K.; Semba, K.; Munro, W. J.; Yamaguchi, H.; Mizuochi, N.; Saito, S.

    2016-07-01

    Optically detected magnetic resonance (ODMR) is a way to characterize the ensemble of NV‑centers. Recently, a remarkably sharp dip was observed in the ODMR with a high-density ensemble of NV centers. The model (Zhu et al 2014 Nat. Commun. 5 3424) indicated that such a dip was due to the spin-1 properties of the NV‑ centers. Here, we present many more details of the analysis to show how this model can be applied to investigate the properties of the NV‑ centers. By using our model, we have reproduced the ODMR with and without applied external magnetic fields. Additionally, we investigate how the ODMR is affected by the typical parameters of the ensemble NV‑ centers such as strain distributions, inhomogeneous magnetic fields, and homogeneous broadening width. Our model provides a way to characterize the NV‑ center from the ODMR, which would be crucial to realize diamond-based quantum information processing.

  4. Measurement of electrical current density distribution in a simple head phantom with magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Gamba, Humberto R.; Bayford, Richard; Holder, David

    1999-01-01

    Knowledge of the influence of the human skull on the electrical current (d.c.) distribution within the brain tissue could prove useful in measuring impedance changes inside the human head. These changes can be related to physiological functions. The studies presented in this paper examine the current density distribution in a simple phantom consisting of a saline filled tank (to simulate scalp and brain) and a ring made of dental grade plaster of Paris (to simulate the human skull). Images of the distribution of the d.c. density of the phantom with and without the plaster of Paris ring were produced using a magnetic resonance imaging technique. These images indicate that the skull is likely to produce a more uniform d.c. density within the brain.

  5. Combining Nuclear Magnetic Resonance Spectroscopy and Density Functional Theory Calculations to Characterize Carvedilol Polymorphs.

    PubMed

    Rezende, Carlos A; San Gil, Rosane A S; Borré, Leandro B; Pires, José Ricardo; Vaiss, Viviane S; Resende, Jackson A L C; Leitão, Alexandre A; De Alencastro, Ricardo B; Leal, Katia Z

    2016-09-01

    The experiments of carvedilol form II, form III, and hydrate by (13)C and (15)N cross-polarization magic-angle spinning (CP MAS) are reported. The GIPAW (gauge-including projector-augmented wave) method from DFT (density functional theory) calculations was used to simulate (13)C and (15)N chemical shifts. A very good agreement was found for the comparison between the global results of experimental and calculated nuclear magnetic resonance (NMR) chemical shifts for carvedilol polymorphs. This work aims a comprehensive understanding of carvedilol crystalline forms employing solution and solid-state NMR as well as DFT calculations. PMID:26372719

  6. Unraveling multi-spin effects in rotational resonance nuclear magnetic resonance using effective reduced density matrix theory

    SciTech Connect

    SivaRanjan, Uppala; Ramachandran, Ramesh

    2014-02-07

    A quantum-mechanical model integrating the concepts of reduced density matrix and effective Hamiltonians is proposed to explain the multi-spin effects observed in rotational resonance (R{sup 2}) nuclear magnetic resonance (NMR) experiments. Employing this approach, the spin system of interest is described in a reduced subspace inclusive of its coupling to the surroundings. Through suitable model systems, the utility of our theory is demonstrated and verified with simulations emerging from both analytic and numerical methods. The analytic results presented in this article provide an accurate description/interpretation of R{sup 2} experimental results and could serve as a test-bed for distinguishing coherent/incoherent effects in solid-state NMR.

  7. Implementation of propeller, spiral, and variable density spiral methods for dynamic contrast enhanced magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ahunbay, Ergun Emin

    2001-09-01

    Previous studies showed that dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) is a valuable tool for the prognosis and diagnosis of cancer, however it requires a tradeoff between temporal and spatial resolution. The ultimate goal of this dissertation is to compare the temporal performance of three methods (spiral, propeller and variable density spiral), given a certain spatial resolution requirement, for the DCE-MRI. These methods show distinction from the conventional MRI methods in their k-space coverage. Propeller and Variable Density Spiral methods use an approach of oversampling the center of k-space, updating the central 13-20% of the radial k-space more frequently than the peripheries. The reason for this is that most of the image data resides in the central part of k-space. Spiral method, on the other hand approaches the problem by updating the overall k-space as fast as possible, faster than the conventional methods. Comparison is performed mainly by computer simulations, where ground truth is known. In addition to computer simulations, these three methods are compared in- vivo, by tracking the DCE-MRI signal amplitude variation with time for each method on a healthy volunteer's liver. One limitation of the spiral and variable density spiral imaging methods is the effect of off-resonance frequencies on image quality. For these spiral based methods, long readout times are desired to have short overall imaging times and high temporal resolution. However, for long readout times, off resonance frequencies blur the images and reduce the spatial resolution. In this dissertation a new method is proposed which is less complicated than most other methods, and reaches an acceptable level of accuracy with less amount of CPU time compared to previously effective methods.

  8. Magnetic resonance electrical impedance tomography (MREIT): conductivity and current density imaging

    NASA Astrophysics Data System (ADS)

    Seo, Jin Keun; Kwon, Ohin; Woo, Eung Je

    2005-01-01

    This paper reviews the latest impedance imaging technique called Magnetic Resonance Electrical Impedance Tomography (MREIT) providing information on electrical conductivity and current density distributions inside an electrically conducting domain such as the human body. The motivation for this research is explained by discussing conductivity changes related with physiological and pathological events, electromagnetic source imaging and electromagnetic stimulations. We briefly summarize the related technique of Electrical Impedance Tomography (EIT) that deals with cross-sectional image reconstructions of conductivity distributions from boundary measurements of current-voltage data. Noting that EIT suffers from the ill-posed nature of the corresponding inverse problem, we introduce MREIT as a new conductivity imaging modality providing images with better spatial resolution and accuracy. MREIT utilizes internal information on the induced magnetic field in addition to the boundary current-voltage measurements to produce three-dimensional images of conductivity and current density distributions. Mathematical theory, algorithms, and experimental methods of current MREIT research are described. With numerous potential applications in mind, future research directions in MREIT are proposed.

  9. Direct magnetic resonance detection of myelin and prospects for quantitative imaging of myelin density

    PubMed Central

    Wilhelm, Michael J.; Ong, Henry H.; Tsai, Ping-Huei; Hackney, David B.; Wehrli, Felix W.

    2012-01-01

    Magnetic resonance imaging has previously demonstrated its potential for indirectly mapping myelin density, either by relaxometric detection of myelin water or magnetization transfer. Here, we investigated whether myelin can be detected and possibly quantified directly. We identified the spectrum of myelin in the spinal cord in situ as well as in myelin lipids extracted via a sucrose gradient method, and investigated its spectral properties. High-resolution solution NMR spectroscopy showed the extract composition to be in agreement with myelin’s known chemical make-up. The 400-MHz 1H spectrum of the myelin extract, at 20 °C (room temperature) and 37 °C, consists of a narrow water resonance superimposed on a broad envelope shifted ∼3.5 ppm upfield, suggestive of long-chain methylene protons. Superimposed on this signal are narrow components resulting from functional groups matching the chemical shifts of the constituents making up myelin lipids. The spectrum could be modeled as a sum of super-Lorentzians with a T2* distribution covering a wide range of values (0.008–26 ms). Overall, there was a high degree of similarity between the spectral properties of extracted myelin lipids and those found in neural tissue. The normalized difference spectrum had the hallmarks of membrane proteins, not present in the myelin extract. Using 3D radially ramp-sampled proton MRI, with a combination of adiabatic inversion and echo subtraction, the feasibility of direct myelin imaging in situ is demonstrated. Last, the integrated signal from myelin suspensions is shown, both spectroscopically and by imaging, to scale with concentration, suggesting the potential for quantitative determination of myelin density. PMID:22628562

  10. Breast Density Analysis with Automated Whole-Breast Ultrasound: Comparison with 3-D Magnetic Resonance Imaging.

    PubMed

    Chen, Jeon-Hor; Lee, Yan-Wei; Chan, Si-Wa; Yeh, Dah-Cherng; Chang, Ruey-Feng

    2016-05-01

    In this study, a semi-automatic breast segmentation method was proposed on the basis of the rib shadow to extract breast regions from 3-D automated whole-breast ultrasound (ABUS) images. The density results were correlated with breast density values acquired with 3-D magnetic resonance imaging (MRI). MRI images of 46 breasts were collected from 23 women without a history of breast disease. Each subject also underwent ABUS. We used Otsu's thresholding method on ABUS images to obtain local rib shadow information, which was combined with the global rib shadow information (extracted from all slice projections) and integrated with the anatomy's breast tissue structure to determine the chest wall line. The fuzzy C-means classifier was used to extract the fibroglandular tissues from the acquired images. Whole-breast volume (WBV) and breast percentage density (BPD) were calculated in both modalities. Linear regression was used to compute the correlation of density results between the two modalities. The consistency of density measurement was also analyzed on the basis of intra- and inter-operator variation. There was a high correlation of density results between MRI and ABUS (R(2) = 0.798 for WBV, R(2) = 0.825 for PBD). The mean WBV from ABUS images was slightly smaller than the mean WBV from MR images (MRI: 342.24 ± 128.08 cm(3), ABUS: 325.47 ± 136.16 cm(3), p < 0.05). In addition, the BPD calculated from MR images was smaller than the BPD from ABUS images (MRI: 24.71 ± 15.16%, ABUS: 28.90 ± 17.73%, p < 0.05). The intra-operator and inter-operator variant analysis results indicated that there was no statistically significant difference in breast density measurement variation between the two modalities. Our results revealed a high correlation in WBV and BPD between MRI and ABUS. Our study suggests that ABUS provides breast density information useful in the assessment of breast health. PMID:26831342

  11. Structure, spectra and antioxidant action of ascorbic acid studied by density functional theory, Raman spectroscopic and nuclear magnetic resonance techniques

    NASA Astrophysics Data System (ADS)

    Singh, Gurpreet; Mohanty, B. P.; Saini, G. S. S.

    2016-02-01

    Structure, vibrational and nuclear magnetic resonance spectra, and antioxidant action of ascorbic acid towards hydroxyl radicals have been studied computationally and in vitro by ultraviolet-visible, nuclear magnetic resonance and vibrational spectroscopic techniques. Time dependant density functional theory calculations have been employed to specify various electronic transitions in ultraviolet-visible spectra. Observed chemical shifts and vibrational bands in nuclear magnetic resonance and vibrational spectra, respectively have been assigned with the help of calculations. Changes in the structure of ascorbic acid in aqueous phase have been examined computationally and experimentally by recording Raman spectra in aqueous medium. Theoretical calculations of the interaction between ascorbic acid molecule and hydroxyl radical predicted the formation of dehydroascorbic acid as first product, which has been confirmed by comparing its simulated spectra with the corresponding spectra of ascorbic acid in presence of hydrogen peroxide.

  12. Relationship between Bone Mineral Density and Spinal Muscle Area in Magnetic Resonance Imaging

    PubMed Central

    Lee, Dae-Young; Yang, Jae-Ho; Ki, Chul-Hyun; Ko, Min-Seok; Suk, Kyung-Soo; Kim, Hak-Sun; Lee, Hwan-Mo

    2015-01-01

    Background Bone mineral density (BMD) is known to have a positive correlation with lean body mass. Several studies have also reported the positive correlation between muscle power and BMD. From this point of view, we hypothesized BMD of lumbar spine to have a positive correlation with muscle mass. Methods Seventy-nine female patients aged between 60 and 75 years old and who underwent magnetic resonance imaging (MRI) and BMD studies were included. Muscle mass in spine MRI was defined by the sum of the average muscle area of three axial images for each disc level. Lumbosacral muscle is the sum of paraspinal muscle and psoas muscle. Results In correlation analysis, paraspinal muscle mass showed positive correlation with BMD of lumbar spine. Lumbosacral muscle mass showed positive correlation with BMD of trochanteric area of the femur. However, BMD of other area showed no significant correlation with muscle mass. Conclusions Therefore, postmenopausal women older than 60 years with a well developed spine muscle mass, have a high BMD. PMID:26713311

  13. Density functional theory computation of Nuclear Magnetic Resonance parameters in light and heavy nuclei

    NASA Astrophysics Data System (ADS)

    Sutter, Kiplangat

    This thesis illustrates the utilization of Density functional theory (DFT) in calculations of gas and solution phase Nuclear Magnetic Resonance (NMR) properties of light and heavy nuclei. Computing NMR properties is still a challenge and there are many unknown factors that are still being explored. For instance, influence of hydrogen-bonding; thermal motion; vibration; rotation and solvent effects. In one of the theoretical studies of 195Pt NMR chemical shift in cisplatin and its derivatives illustrated in Chapter 2 and 3 of this thesis. The importance of representing explicit solvent molecules explicitly around the Pt center in cisplatin complexes was outlined. In the same complexes, solvent effect contributed about half of the J(Pt-N) coupling constant. Indicating the significance of considering the surrounding solvent molecules in elucidating the NMR measurements of cisplatin binding to DNA. In chapter 4, we explore the Spin-Orbit (SO) effects on the 29Si and 13C chemical shifts induced by surrounding metal and ligands. The unusual Ni, Pd, Pt trends in SO effects to the 29Si in metallasilatrane complexes X-Si-(mu-mt)4-M-Y was interpreted based on electronic and relativistic effects rather than by structural differences between the complexes. In addition, we develop a non-linear model for predicting NMR SO effects in a series of organics bonded to heavy nuclei halides. In chapter 5, we extend the idea of "Chemist's orbitals" LMO analysis to the quantum chemical proton NMR computation of systems with internal resonance-assisted hydrogen bonds. Consequently, we explicitly link the relationship between the NMR parameters related to H-bonded systems and intuitive picture of a chemical bond from quantum calculations. The analysis shows how NMR signatures characteristic of H-bond can be explained by local bonding and electron delocalization concepts. One shortcoming of some of the anti-cancer agents like cisplatin is that they are toxic and researchers are looking for

  14. Resonant X-ray magnetic scattering studies of the TmNi 2B 2C spin density wave

    NASA Astrophysics Data System (ADS)

    Mannix, Danny; Thompson, Paul; Brown, Simon; Bouchenoire, Laurence; Canfield, Paul

    2004-11-01

    We report on polarisation resolved, resonant X-ray magnetic scattering (RXMS) studies of the spin density wave (SDW) formed in the TmNi 2B 2C superconductor. From this high wave-vector resolution investigation, we find the incommensurate magnetic SDW propagation vector to be ( 0±τ0±τ0) with τ=0.096 rlu, slightly larger than the value previously deduced from magnetic neutron studies ( τ=0.093 rlu). The widths of the SDW peaks at 1 K are consistent with long-range magnetic order and we have deduced a magnetic correlation length of ∼1200 Å. When the incident photons are tuned to the Tm L 3 absorption edge, the RXMS energy response consists of a double peak feature, arising from both dipole (E1) transitions, probing the 5d conduction band polarisation, and quadrupole (E2) transitions, probing the Tm 4f magnetic moments. The RXMS wave-vector dependences of the (0± τ 0± τ L) SDW satellites are consistent with the transverse spin-density wave structure, with moments orientated along the crystallographic c-axis, originally proposed from neutron-scattering measurements. Our RXMS data are also in good agreement with the magnetic neutron-scattering response for the thermal evolution of the magnetic moments down to 1 K and in deducing a Nèel temperature of T=1.5 K. However, the RXMS probe reveals a small shift of the magnetic propagation vector of the order 3×10 -3 rlu along the (1 1 0) direction, on decreasing temperature below TN. Using very high-resolution X-ray studies with a conventional Si(1 1 1) analyser, no change in width or position is found below TN or Tc. We have also not observed any charge modulation peaks at 2τ, indicating that the SDW does not couple to the lattice.

  15. Magnetic-field-induced density of states in Mg B2 : Spin susceptibility measured by conduction-electron spin resonance

    NASA Astrophysics Data System (ADS)

    Simon, F.; Jánossy, A.; Fehér, T.; Murányi, F.; Garaj, S.; Forró, L.; Petrovic, C.; Bud'Ko, S.; Ribeiro, R. A.; Canfield, P. C.

    2005-07-01

    The magnetic-field dependence of the electron spin susceptibility χs was measured in the superconducting state of high-purity MgB2 fine powders from the intensity of the conduction-electron spin resonance at 3.8, 9.4, and 35GHz . The measurements confirm that a large part of the density of states is restored at low temperatures at fields below 1T in qualitative agreement with the closing of the π band gaps in the two-band model. However, the increase of χs with field and temperature is larger than expected from current superconductor models of MgB2 .

  16. Cyclotron-resonance transmission through potassium in a perpendicular magnetic field: Effects of the charge-density wave

    NASA Astrophysics Data System (ADS)

    Park, Mi-Ae; Overhauser, A. W.

    1997-01-01

    Microwave transmission through potassium by Dunifer, Sambles, and Mace [J. Phys. Condens. Matter 1, 875 (1989)] in a perpendicular magnetic field shows five signals. They are Gantmakher-Kaner (GK) oscillations, conduction-electron-spin resonance, high-frequency oscillations, cyclotron resonance, and cyclotron-resonance subharmonics. Only the spin resonance has been successfully explained using a free-electron model. However, such a model predicts GK oscillations which are too large by several orders of magnitude. Lacueva and Overhauser [Phys. Rev. B 48, 16t935 (1993)] have shown that charge-density-wave (CDW) energy gaps which cut through the Fermi surface reduce the GK signal. CDW gaps also create a small Fermi-surface cylinder. The high-frequency oscillations were shown to result from Landau-level quantization in the cylinder. Recently we found that the anomalous microwave surface resistance, observed by Grimes and Kip [Phys. Rev. 132, 1991 (1963)], can be explained only if the cylinder axis is tilted ~45° with respect to the [110] crystal direction perpendicular to the surface. (Such a tilt was predicted by Giuliani and Overhauser [Phys. Rev. B 20, 1328 (1979)].) In this study we show that oscillatory motions, parallel to the field, of electrons in the tilted cylinder cause the cyclotron-resonance transmission. This signal and its subharmonics would be completely absent without the tilt. Consequently, four of the five transmission signals require a CDW broken symmetry.

  17. Magnetic Resonance Imaging (MRI)

    MedlinePlus

    ... How Can I Help a Friend Who Cuts? Magnetic Resonance Imaging (MRI) KidsHealth > For Teens > Magnetic Resonance Imaging (MRI) Print A A A Text Size What's ... Exam Safety Getting Your Results What Is MRI? Magnetic resonance imaging (MRI) is a type of safe, painless testing ...

  18. Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Andrew, E. R.

    2009-06-01

    Author's preface; 1. Introduction; 2. Basic theory; 3. Experimental methods; 4. Measurement of nuclear properties and general physical applications; 5. Nuclear magnetic resonance in liquids and gases; 6. Nuclear magnetic resonance in non-metallic solids; 7. Nuclear magnetic resonance in metals; 8. Quadrupole effects; Appendices 1-6; Glossary of symbols; Bibliography and author index; Subject index.

  19. Volumetric breast density evaluation by ultrasound tomography and magnetic resonance imaging: a preliminary comparative study

    NASA Astrophysics Data System (ADS)

    Myc, Lukasz; Duric, Neb; Littrup, Peter; Li, Cuiping; Ranger, Bryan; Lupinacci, Jessica; Schmidt, Steven; Rama, Olsi; Bey-Knight, Lisa

    2010-03-01

    Since a 1976 study by Wolfe, high breast density has gained recognition as a factor strongly correlating with an increased incidence of breast cancer. These observations have led to mammographic density being designated a "risk factor" for breast cancer. Clinically, the exclusive reliance on mammography for breast density measurement has forestalled the inclusion of breast density into statistical risk models. This exclusion has in large part been due to the ionizing radiation associated with the method. Additionally, the use of mammography as valid tool for measuring a three dimensional characteristic (breast density) has been criticized for its prima facie incongruity. These shortfalls have prompted MRI studies of breast density as an alternative three-dimensional method of assessing breast density. Although, MRI is safe and can be used to measure volumetric density, its cost has prohibited its use in screening. Here, we report that sound speed measurements using a prototype ultrasound tomography device have potential for use as surrogates for breast density measurement. Accordingly, we report a strong positive linear correlation between volume-averaged sound speed of the breast and percent glandular tissue volume as assessed by MR.

  20. Current density and state density in diluted magnetic semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Pérez Merchancano, S. T.; Paredes Gutiérrez, H.; Zuñiga, J. A.

    2016-02-01

    We study in this paper the spin-polarized current density components in diluted magnetic semiconductor tunnelling diodes with different sample geometries. We calculate the resonant JxV and the density of states. The differential conductance curves are analyzed as functions of the applied voltage and the magnetic potential strength induced by the magnetic ions.

  1. A multi-nuclear magnetic resonance and density functional theory investigation of epitaxially grown InGaP2.

    PubMed

    Knijn, P J; van Bentum, P J M; Fang, C M; Bauhuis, G J; de Wijs, G A; Kentgens, A P M

    2016-08-01

    In this paper the short and long range order in In0.483Ga0.517P thin films is investigated by solid-state Nuclear Magnetic Resonance (NMR) spectroscopy. To this end two samples were grown on a GaAs substrate by metal-organic vapor phase epitaxy at two different growth-pressures. From band gap energy measurements, CuPt long range order parameters of SCuPt = 0.22 and 0.39 were deduced, respectively. In the (31)P spectrum five resonances are observed corresponding to the five possible P(GanIn4-n), n = 0-4, coordinations whose relative intensities correspond to the order in the material, but the intensity variations for order parameters between 0 and 0.5 are minimal. (69)Ga, (71)Ga and (115)In (MQ)MAS spectra were acquired to analyze the quadrupolar and chemical shift distributions related to the (dis)order in these materials in more detail. All these spectra clearly reflect the disorder in the sample and do not show the presence of highly ordered domains. The difference in the order parameter in the sample is not clearly reflected in the spectra. (31)P chemical shifts were calculated using Density Functional Theory. The experimentally observed shifts are well reproduced with a simple random model of the disorder, thus confirming the assignment of the resonances. The (31)P chemical shifts are very sensitive to changes in the lattice parameter and chemical surroundings. These effects nearly compensate and explain why the (31)P chemical shifts in pure InP and GaP are nearly identical whereas a large difference would be expected based on the observed shift difference for the P[In4] and P[Ga4] coordinations in In0.483Ga0.517P. PMID:27424548

  2. Breast density quantification using magnetic resonance imaging (MRI) with bias field correction: A postmortem study

    SciTech Connect

    Ding, Huanjun; Johnson, Travis; Lin, Muqing; Le, Huy Q.; Ducote, Justin L.; Su, Min-Ying; Molloi, Sabee

    2013-12-15

    Purpose: Quantification of breast density based on three-dimensional breast MRI may provide useful information for the early detection of breast cancer. However, the field inhomogeneity can severely challenge the computerized image segmentation process. In this work, the effect of the bias field in breast density quantification has been investigated with a postmortem study. Methods: T1-weighted images of 20 pairs of postmortem breasts were acquired on a 1.5 T breast MRI scanner. Two computer-assisted algorithms were used to quantify the volumetric breast density. First, standard fuzzy c-means (FCM) clustering was used on raw images with the bias field present. Then, the coherent local intensity clustering (CLIC) method estimated and corrected the bias field during the iterative tissue segmentation process. Finally, FCM clustering was performed on the bias-field-corrected images produced by CLIC method. The left–right correlation for breasts in the same pair was studied for both segmentation algorithms to evaluate the precision of the tissue classification. Finally, the breast densities measured with the three methods were compared to the gold standard tissue compositions obtained from chemical analysis. The linear correlation coefficient, Pearson'sr, was used to evaluate the two image segmentation algorithms and the effect of bias field. Results: The CLIC method successfully corrected the intensity inhomogeneity induced by the bias field. In left–right comparisons, the CLIC method significantly improved the slope and the correlation coefficient of the linear fitting for the glandular volume estimation. The left–right breast density correlation was also increased from 0.93 to 0.98. When compared with the percent fibroglandular volume (%FGV) from chemical analysis, results after bias field correction from both the CLIC the FCM algorithms showed improved linear correlation. As a result, the Pearson'sr increased from 0.86 to 0.92 with the bias field correction

  3. Enhancement of DFT-calculations at petascale: Nuclear Magnetic Resonance, Hybrid Density Functional Theory and Car-Parrinello calculations

    NASA Astrophysics Data System (ADS)

    Varini, Nicola; Ceresoli, Davide; Martin-Samos, Layla; Girotto, Ivan; Cavazzoni, Carlo

    2013-08-01

    One of the most promising techniques used for studying the electronic properties of materials is based on Density Functional Theory (DFT) approach and its extensions. DFT has been widely applied in traditional solid state physics problems where periodicity and symmetry play a crucial role in reducing the computational workload. With growing compute power capability and the development of improved DFT methods, the range of potential applications is now including other scientific areas such as Chemistry and Biology. However, cross disciplinary combinations of traditional Solid-State Physics, Chemistry and Biology drastically improve the system complexity while reducing the degree of periodicity and symmetry. Large simulation cells containing of hundreds or even thousands of atoms are needed to model these kind of physical systems. The treatment of those systems still remains a computational challenge even with modern supercomputers. In this paper we describe our work to improve the scalability of Quantum ESPRESSO (Giannozzi et al., 2009 [3]) for treating very large cells and huge numbers of electrons. To this end we have introduced an extra level of parallelism, over electronic bands, in three kernels for solving computationally expensive problems: the Sternheimer equation solver (Nuclear Magnetic Resonance, package QE-GIPAW), the Fock operator builder (electronic ground-state, package PWscf) and most of the Car-Parrinello routines (Car-Parrinello dynamics, package CP). Final benchmarks show our success in computing the Nuclear Magnetic Response (NMR) chemical shift of a large biological assembly, the electronic structure of defected amorphous silica with hybrid exchange-correlation functionals and the equilibrium atomic structure of height Porphyrins anchored to a Carbon Nanotube, on many thousands of CPU cores.

  4. Magnetic Resonance Q Mapping Reveals a Decrease in Microvessel Density in the arcAβ Mouse Model of Cerebral Amyloidosis

    PubMed Central

    Ielacqua, Giovanna D.; Schlegel, Felix; Füchtemeier, Martina; Xandry, Jael; Rudin, Markus; Klohs, Jan

    2016-01-01

    Alterations in density and morphology of the cerebral microvasculature have been reported to occur in Alzheimer's disease patients and animal models of the disease. In this study we compared magnetic resonance imaging (MRI) techniques for their utility to detect age-dependent changes of the cerebral vasculature in the arcAβ mouse model of cerebral amyloidosis. Dynamic susceptibility contrast (DSC)-MRI was performed by tracking the passage of a superparamagnetic iron oxide nanoparticle in the brain with dynamic gradient echo planar imaging (EPI). From this measurements relative cerebral blood volume [rCBV(DSC)] and relative cerebral blood flow (rCBF) were estimated. For the same animal maps of the relaxation shift index Q were computed from high resolution gradient echo and spin echo data that were acquired before and after superparamagnetic iron oxide (SPIO) nanoparticle injection. Q-values were used to derive estimates of microvessel density. The change in the relaxation rates ΔR2* obtained from pre- and post-contrast gradient echo data was used for the alternative determination of rCBV [rCBV(ΔR2*)]. Linear mixed effects modeling found no significant association between rCBV(DSC), rCBV(ΔR2*), rCBF, and Q with genotype in 13-month old mice [compared to age-matched non-transgenic littermates (NTLs)] for any of the evaluated brain regions. In 24-month old mice there was a significant association for rCBV(DSC) with genotype in the cerebral cortex, and for rCBV(ΔR2*) in the cerebral cortex and cerebellum. For rCBF there was a significant association in the cerebellum but not in other brain regions. Q-values in the olfactory bulb, cerebral cortex, striatum, hippocampus, and cerebellum in 24-month old mice were significantly associated with genotype. In those regions Q-values were reduced between 11 and 26% in arcAβ mice compared to age-matched NTLs. Vessel staining with CD31 immunohistochemistry confirmed a reduction of microvessel density in the old arcAβ mice

  5. Magnetic resonance sees lesions of multiple sclerosis

    SciTech Connect

    Ziporyn, T.

    1985-02-15

    The value of nuclear magnetic resonance imaging in the diagnosis and quantitation of the progression of multiple sclerosis is discussed. Magnetic resonance imaging generates images that reflect differential density and velocity of hydrogen nuclei between cerebral gray and white matter, as well as between white matter and pathological lesions of the disease.

  6. Concentration of metabolites from low-density planktonic communities for environmental metabolomics using nuclear magnetic resonance spectroscopy.

    PubMed

    Everroad, R Craig; Yoshida, Seiji; Tsuboi, Yuuri; Date, Yasuhiro; Kikuchi, Jun; Moriya, Shigeharu

    2012-01-01

    Environmental metabolomics is an emerging field that is promoting new understanding in how organisms respond to and interact with the environment and each other at the biochemical level. Nuclear magnetic resonance (NMR) spectroscopy is one of several technologies, including gas chromatography-mass spectrometry (GC-MS), with considerable promise for such studies. Advantages of NMR are that it is suitable for untargeted analyses, provides structural information and spectra can be queried in quantitative and statistical manners against recently available databases of individual metabolite spectra. In addition, NMR spectral data can be combined with data from other omics levels (e.g. transcriptomics, genomics) to provide a more comprehensive understanding of the physiological responses of taxa to each other and the environment. However, NMR is less sensitive than other metabolomic techniques, making it difficult to apply to natural microbial systems where sample populations can be low-density and metabolite concentrations low compared to metabolites from well-defined and readily extractable sources such as whole tissues, biofluids or cell-cultures. Consequently, the few direct environmental metabolomic studies of microbes performed to date have been limited to culture-based or easily defined high-density ecosystems such as host-symbiont systems, constructed co-cultures or manipulations of the gut environment where stable isotope labeling can be additionally used to enhance NMR signals. Methods that facilitate the concentration and collection of environmental metabolites at concentrations suitable for NMR are lacking. Since recent attention has been given to the environmental metabolomics of organisms within the aquatic environment, where much of the energy and material flow is mediated by the planktonic community, we have developed a method for the concentration and extraction of whole-community metabolites from planktonic microbial systems by filtration. Commercially

  7. Magnetic resonance annual, 1988

    SciTech Connect

    Kressel, H.Y.

    1987-01-01

    This book features reviews of high-resolution MRI of the knee, MRI of the normal and ischmeic hip, MRI of the heart, and temporomandibular joint imaging, as well as thorough discussion on artifacts in magnetic resonance imaging. Contributors consider the clinical applications of gadolinium-DTPA in magnetic resonance imaging and the clinical use of partial saturation and saturation recovery sequences. Timely reports assess the current status of rapid MRI and describe a new rapid gated cine MRI technique. Also included is an analysis of cerebrospinal fluid flow effects during MRI of the central nervous system.

  8. Magnetic resonance imaging

    SciTech Connect

    Stark, D.D.; Bradley, W.G. Jr.

    1988-01-01

    The authors present a review of magnetic resonance imaging. Many topics are explored from instrumentation, spectroscopy, blood flow and sodium imaging to detailed clinical applications such as the differential diagnosis of multiple sclerosis or adrenal adenoma. The emphasis throughout is on descriptions of normal multiplanar anatomy and pathology as displayed by MRI.

  9. Magnetic Resonance Annual, 1985

    SciTech Connect

    Kressel, H.Y.

    1985-01-01

    The inaugural volume of Magnetic Resonance Annual includes reviews of MRI of the posterior fossa, cerebral neoplasms, and the cardiovascular and genitourinary systems. A chapter on contrast materials outlines the mechanisms of paramagnetic contrast enhancement and highlights several promising contrast agents.

  10. Single spin magnetic resonance

    NASA Astrophysics Data System (ADS)

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  11. Single spin magnetic resonance.

    PubMed

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution. PMID:27378060

  12. Functional Magnetic Resonance Imaging

    ERIC Educational Resources Information Center

    Voos, Avery; Pelphrey, Kevin

    2013-01-01

    Functional magnetic resonance imaging (fMRI), with its excellent spatial resolution and ability to visualize networks of neuroanatomical structures involved in complex information processing, has become the dominant technique for the study of brain function and its development. The accessibility of in-vivo pediatric brain-imaging techniques…

  13. [Magnetic resonance, an introduction].

    PubMed

    Cabrera Rueda, D J; Fernández Herrerías, G

    2000-09-01

    What would you explain to a patient if he/she had to undergo a magnetic resonance imagery session? Do you know if a person wearing a pacemaker can undergo an MRI? These and many other questions are answered in the following article since magnetic resonance imagery is a very useful diagnostic medium; however, it is one which not everyone has been able to get to know and use. The authors shed light on this diagnostic technique for nurses starting with its physical foundations; since knowing these aids professionals to correctly plan our treatments and improves the attention provided to patients who undergo this test. The authors also list the specific components in this device, the possible biological effects, the detractions and some basic recommendations. PMID:11111673

  14. Cavity- and waveguide-resonators in electron paramagnetic resonance, nuclear magnetic resonance, and magnetic resonance imaging.

    PubMed

    Webb, Andrew

    2014-11-01

    Cavity resonators are widely used in electron paramagnetic resonance, very high field magnetic resonance microimaging and also in high field human imaging. The basic principles and designs of different forms of cavity resonators including rectangular, cylindrical, re-entrant, cavity magnetrons, toroidal cavities and dielectric resonators are reviewed. Applications in EPR and MRI are summarized, and finally the topic of traveling wave MRI using the magnet bore as a waveguide is discussed. PMID:25456314

  15. Magnetic Resonance Facility (Fact Sheet)

    SciTech Connect

    Not Available

    2012-03-01

    This fact sheet provides information about Magnetic Resonance Facility capabilities and applications at NREL's National Bioenergy Center. Liquid and solid-state analysis capability for a variety of biomass, photovoltaic, and materials characterization applications across NREL. NREL scientists analyze solid and liquid samples on three nuclear magnetic resonance (NMR) spectrometers as well as an electron paramagnetic resonance (EPR) spectrometer.

  16. Rotation dependence of a phase delay between plasma edge electron density and temperature fields due to a fast rotating, resonant magnetic perturbation field

    SciTech Connect

    Stoschus, H.; Schmitz, O.; Frerichs, H.; Unterberg, B.; Abdullaev, S. S.; Clever, M.; Coenen, J. W.; Kruezi, U.; Schega, D.; Samm, U.; Jakubowski, M. W.

    2010-06-15

    Measurements of the plasma edge electron density n{sub e} and temperature T{sub e} fields during application of a fast rotating, resonant magnetic perturbation (RMP) field show a characteristic modulation of both, n{sub e} and T{sub e} coherent to the rotation frequency of the RMP field. A phase delay PHI between the n{sub e}(t) and T{sub e}(t) waveforms is observed and it is demonstrated that this phase delay PHI is a function of the radius with PHI(r) depending on the relative rotation of the RMP field and the toroidal plasma rotation. This provides for the first time direct experimental evidence for a rotation dependent damping of the external RMP field in the edge layer of a resistive high-temperature plasma which breaks down at low rotation and high resonant field amplitudes.

  17. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Larsen, Michael; Griffith, Robert; Bulatowicz, Michael

    2014-03-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation (NGC) has concluded the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This presentation will describe the operational principles, design basics, and demonstrated performance of the NMRG including an overview of the NGC designs developed and demonstrated in the DARPA gyro development program.

  18. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Larsen, Michael; Mirijanian, James

    2012-06-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation is concluding the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This poster will describe the history, operational principles, and design basics of the NMRG including an overview of the NSD designs developed and demonstrated in the DARPA gyro development program. General performance results from phases 3 and 4 will also be presented.

  19. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael; Griffith, Robert; Larsen, Michael

    2014-03-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation (NGC) has concluded the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This poster will describe the history, operational principles, design, and demonstrated performance of the NMRG including an overview of the NGC designs developed and demonstrated in the DARPA gyro development program.

  20. Magnetic resonance of slotted circular cylinder resonators

    NASA Astrophysics Data System (ADS)

    Du, Junjie; Liu, Shiyang; Lin, Zhifang; Chui, S. T.

    2008-07-01

    By a rigorous full-wave approach, a systemic study is made on the magnetic resonance of slotted circular cylinder resonators (SCCRs) made of a perfect conductor for the lossless case. This is a two-dimensional analog of the split-ring resonator and may serve as an alternative type of essential constituent of electromagnetic metamaterials. It is found that the resonance frequency can be modulated by changing the geometrical parameters and the dielectrics filling in the cavity and the slot. An approximate empirical expression is presented for magnetic resonance frequency of SCCRs from the viewpoint of an L-C circuit system. Finally, it is demonstrated that the SCCR structure can be miniaturized to less than 1/150 resonant wavelength in size with the dielectrics available currently.

  1. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Larsen, Michael

    2011-05-01

    The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation is currently in phase 4 of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. The micro-NMRG technology is pushing the boundaries of size, weight, power, and performance allowing new small platform applications of navigation grade Inertial Navigation System (INS) technology. Information on the historical development of the technology, basics of operation, task performance goals, application opportunities, and a phase 2 sample of earth rate measurement data will be presented. Funding Provided by the Defense Advanced Research Projects Agency (DARPA)

  2. Cranial magnetic resonance imaging

    SciTech Connect

    Elster, A.D.

    1988-01-01

    Cranial Magnetic Resonance Imaging is comprehensive, well structured, and well written. The material is current and well referenced. The illustrations are good and complement the text well. The overall quality of publication is above average. The greatest attribute of the book is its readability. The author demonstrates ample skill in making complex subjects, such as MR physics and imaging of cerebral hemorrhage, easy to understand. The book closes with a detailed atlas on the anatomic appearance of the brain on MR images in the axial, coronal, and sagittal planes.

  3. Magnetic Resonance Imaging Duodenoscope.

    PubMed

    Syms, Richard R A; Young, Ian R; Wadsworth, Christopher A; Taylor-Robinson, Simon D; Rea, Marc

    2013-12-01

    A side-viewing duodenoscope capable of both optical and magnetic resonance imaging (MRI) is described. The instrument is constructed from MR-compatible materials and combines a coherent fiber bundle for optical imaging, an irrigation channel and a side-opening biopsy channel for the passage of catheter tools with a tip saddle coil for radio-frequency signal reception. The receiver coil is magnetically coupled to an internal pickup coil to provide intrinsic safety. Impedance matching is achieved using a mechanically variable mutual inductance, and active decoupling by PIN-diode switching. (1)H MRI of phantoms and ex vivo porcine liver specimens was carried out at 1.5 T. An MRI field-of-view appropriate for use during endoscopic retrograde cholangiopancreatography (ERCP) was obtained, with limited artefacts, and a signal-to-noise ratio advantage over a surface array coil was demonstrated. PMID:23807423

  4. Spin Projection of Empty Partial Density of States by Resonant X-ray Scattering (RXS): Application to Materials with Different Magnetic Ordering

    SciTech Connect

    Draeger, Guenter; Machek, Pavel

    2003-01-24

    We report the first experimental spin projections of empty partial density of states in antiferromagnetic NiO and CuO, paramagnetic MnO and in ferrimagnetic Dy3Fe5O12 by means of resonant X-ray scattering (RXS). Resolving resonantly scattered K{alpha}1,2 , K{beta}1,3 , L{alpha}1 and L1 core line spectra into their spin-up and spin-down components the spin character of the dipole- and quadrupole-excited conduction band states can quantitatively be analyzed. Since the method employs spin conservation in the RXS process and local spin references, it needs neither circularly polarized radiation nor sample magnetization for measuring the spectra. Hence, antiferro- and paramagnetic materials can be investigated as well. In the paper, the basic idea of the novel method, its experimental realization and the data treatment are reported including the spectra decomposition into the spin-up and spin-down components by using Principal Component Analysis (PCA). New and unambiguous results will be presented providing the opportunity to verify experimentally the results of spin-dependent (LSDA+U) calculations. So we argue the new spectroscopy complements X-ray magnetic dichroism, which is silent for antiferro- and paramagnetic materials. In fact, the novel method gives insight into the spin polarization of conduction band states in correlated materials, independently on their magnetic ordering.

  5. Assessing the Relationship between Lung Density and Function with Oxygen-Enhanced Magnetic Resonance Imaging in a Mouse Model of Emphysema

    PubMed Central

    Zurek, Magdalena; Sladen, Louise; Johansson, Edvin; Olsson, Marita; Jackson, Sonya; Zhang, Hui; Mayer, Gaell; Hockings, Paul D.

    2016-01-01

    Purpose A magnetic resonance imaging method is presented that allows for the simultaneous assessment of oxygen delivery, oxygen uptake, and parenchymal density. The technique is applied to a mouse model of porcine pancreatic elastase (PPE) induced lung emphysema in order to investigate how structural changes affect lung function. Method Nine-week-old female C57BL6 mice were instilled with saline or PPE at days 0 and 7. At day 19, oxygen delivery, oxygen uptake, and lung density were quantified from T1 and proton-density measurements obtained via oxygen-enhanced magnetic resonance imaging (OE-MRI) using an ultrashort echo-time imaging sequence. Subsequently, the lungs were sectioned for histological observation. Blood-gas analyses and pulmonary functional tests via FlexiVent were performed in separate cohorts. Principal Findings PPE-challenged mice had reduced density when assessed via MRI, consistent with the parenchyma loss observed in the histology sections, and an increased lung compliance was detected via FlexiVent. The oxygenation levels, as assessed via the blood-gas analysis, showed no difference between PPE-challenged animals and control. This finding was mirrored in the global MRI assessments of oxygen delivery and uptake, where the changes in relaxation time indices were matched between the groups. The heterogeneity of the same parameters however, were increased in PPE-challenged animals. When the oxygenation status was investigated in regions of varying density, a reduced oxygen-uptake was found in low-density regions of PPE-challenged mice. In high-density regions the uptake was higher than that of regions of corresponding density in control animals. The oxygen delivery was proportional to the oxygen uptake in both groups. Conclusions The proposed method allowed for the regional assessment of the relationship between lung density and two aspects of lung function, the oxygen delivery and uptake. When compared to global indices of lung function, an

  6. Magnetic Resonance Elastography

    PubMed Central

    Litwiller, Daniel V.; Mariappan, Yogesh K.; Ehman, Richard L.

    2015-01-01

    Often compared to the practice of manual palpation, magnetic resonance elastography is an emerging technology for quantitatively assessing the mechanical properties of tissue as a basis for characterizing disease. The potential of MRE as a diagnostic tool is rooted in the fact that normal and diseased tissues often differ significantly in terms of their intrinsic mechanical properties. MRE uses magnetic resonance imaging (MRI) in conjunction with the application of mechanical shear waves to probe tissue mechanics. This process can be broken down into three essential steps: inducing shear waves in the tissue,imaging the propagating shear waves with MRI, andanalyzing the wave data to generate quantitative images of tissue stiffness MRE has emerged as a safe, reliable and noninvasive method for staging hepatic liver fibrosis, and is now used in some locations as an alternative to biopsy. MRE is also being used in the ongoing investigations of numerous other organs and tissues, including, for example, the spleen, kidney, pancreas, brain, heart, breast, skeletal muscle, prostate, vasculature, lung, spinal cord, eye, bone, and cartilage. In the article that follows, some fundamental techniques and applications of MRE are summarized. PMID:26361467

  7. Introduction to Nuclear Magnetic Resonance

    NASA Technical Reports Server (NTRS)

    Manatt, Stanley L.

    1985-01-01

    The purpose of this paper is to try to give a short overview of what the status is on nuclear magnetic resonance (NMR). It's a subject where one really has to spend some time to look at the physics in detail to develop a proper working understanding. I feel it's not appropriate to present to you density matrices, Hamiltonians of all sorts, and differential equations representing the motion of spins. I'm really going to present some history and status, and show a few very simple concepts involved in NMR. It is a form of radio frequency spectroscopy and there are a great number of nuclei that can be studied very usefully with the technique. NMR requires a magnet, a r.f. transmitter/receiver system, and a data acquisition system.

  8. Accessible magnetic resonance imaging.

    PubMed

    Kaufman, L; Arakawa, M; Hale, J; Rothschild, P; Carlson, J; Hake, K; Kramer, D; Lu, W; Van Heteren, J

    1989-10-01

    The cost of magnetic resonance imaging (MRI) is driven by magnetic field strength. Misperceptions as to the impact of field strength on performance have led to systems that are more expensive than they need to be. Careful analysis of all the factors that affect diagnostic quality lead to the conclusion that field strength per se is not a strong determinant of system performance. Freed from the constraints imposed by high-field operation, it is possible to exploit a varied set of opportunities afforded by low-field operation. In addition to lower costs and easier siting, we can take advantage of shortened T1 times, higher contrast, reduced sensitivity to motion, and reduced radiofrequency power deposition. These conceptual advantages can be made to coalesce onto practical imaging systems. We describe a low-cost MRI system that utilizes a permanent magnet of open design. Careful optimization of receiving antennas and acquisition sequences permit performance levels consistent with those needed for an effective diagnostic unit. Ancillary advantages include easy access to the patient, reduced claustrophobia, quiet and comfortable operation, and absence of a missile effect. The system can be sited in 350 sq ft and consumes a modest amount of electricity. MRI equipment of this kind can widen the population base than can access this powerful and beneficial diagnostic modality. PMID:2640910

  9. Virtual magnetic resonance colonography

    PubMed Central

    Debatin, J; Lauenstein, T

    2003-01-01

    Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques. PMID:12746264

  10. Nuclear Magnetic Resonance Gyroscope

    NASA Astrophysics Data System (ADS)

    Larsen, Michael; Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Mirijanian, James; Pavell, James

    2015-05-01

    The Nuclear Magnetic Resonance Gyroscope (NMRG) is being developed by the Northrop Grumman Corporation (NGC). Cold and hot atom interferometer based gyroscopes have suffered from Size, Weight, and Power (SWaP) challenges and limits in bandwidth, scale factor stability, dead time, high rotation rate, vibration, and acceleration. NMRG utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as a reference for determining rotation, providing continuous measurement, high bandwidth, stable scale factor, high rotation rate measurement, and low sensitivity to vibration and acceleration in a low SWaP package. The sensitivity to vibration has been partially tested and demonstrates no measured sensitivity within error bars. Real time closed loop implementation of the sensor significantly decreases environmental and systematic sensitivities and supports a compact and low power digital signal processing and control system. Therefore, the NMRG technology holds great promise for navigation grade performance in a low cost SWaP package. The poster will describe the history, operation, and design of the NMRG. General performance results will also be presented along with recent vibration test results.

  11. Reducing Field Distortion in Magnetic Resonance Imaging

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  12. Superconducting Magnets for Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Feenan, Peter

    2000-03-01

    MRI is now a well established diagnostic technique in medicine. The richness of information provided by magnetic resonance gives rise to a variety of techniques which in turn leads to a variety of magnet designs. Magnet designers must consider suitable superconduting materials for the magnet, but need also to consider the overall fomat of the magnet to maximise patient comfort, access for clinicians and convenience of use - in some examples magnets are destined for use within the operating theatre and special considerations are required for this. Magnet types include; (1) low-field general purpose imagers, (2) extremity imaging, (3) open magnets with exellent all-round access often employing iron or permanent magnetic materials, (4) high-field magnets, and (5) very high-field (7 Tesla and more) magnets for spectroscopy and functional imaging research. Examples of these magnet varieties will be shown and some of the design challenges discussed.

  13. Low field magnetic resonance imaging

    DOEpatents

    Pines, Alexander; Sakellariou, Dimitrios; Meriles, Carlos A.; Trabesinger, Andreas H.

    2010-07-13

    A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

  14. Nuclear magnetic resonance contrast agents

    DOEpatents

    Smith, Paul H.; Brainard, James R.; Jarvinen, Gordon D.; Ryan, Robert R.

    1997-01-01

    A family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC.sub.16 H.sub.14 N.sub.6. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques.

  15. Nuclear magnetic resonance contrast agents

    DOEpatents

    Smith, P.H.; Brainard, J.R.; Jarvinen, G.D.; Ryan, R.R.

    1997-12-30

    A family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC{sub 16}H{sub 14}N{sub 6}. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques. 10 figs.

  16. Magnetic Resonance Imaging of Electrolysis.

    PubMed Central

    Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris

    2015-01-01

    This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research. PMID:25659942

  17. Magnetic Resonance Imaging of Electrolysis.

    NASA Astrophysics Data System (ADS)

    Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris

    2015-02-01

    This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research.

  18. Functional magnetic resonance imaging.

    PubMed

    Buchbinder, Bradley R

    2016-01-01

    Functional magnetic resonance imaging (fMRI) maps the spatiotemporal distribution of neural activity in the brain under varying cognitive conditions. Since its inception in 1991, blood oxygen level-dependent (BOLD) fMRI has rapidly become a vital methodology in basic and applied neuroscience research. In the clinical realm, it has become an established tool for presurgical functional brain mapping. This chapter has three principal aims. First, we review key physiologic, biophysical, and methodologic principles that underlie BOLD fMRI, regardless of its particular area of application. These principles inform a nuanced interpretation of the BOLD fMRI signal, along with its neurophysiologic significance and pitfalls. Second, we illustrate the clinical application of task-based fMRI to presurgical motor, language, and memory mapping in patients with lesions near eloquent brain areas. Integration of BOLD fMRI and diffusion tensor white-matter tractography provides a road map for presurgical planning and intraoperative navigation that helps to maximize the extent of lesion resection while minimizing the risk of postoperative neurologic deficits. Finally, we highlight several basic principles of resting-state fMRI and its emerging translational clinical applications. Resting-state fMRI represents an important paradigm shift, focusing attention on functional connectivity within intrinsic cognitive networks. PMID:27432660

  19. Magnetic resonance energy and topological resonance energy.

    PubMed

    Aihara, Jun-Ichi

    2016-04-28

    Ring-current diamagnetism of a polycyclic π-system is closely associated with thermodynamic stability due to the individual circuits. Magnetic resonance energy (MRE), derived from the ring-current diamagnetic susceptibility, was explored in conjunction with graph-theoretically defined topological resonance energy (TRE). For many aromatic molecules, MRE is highly correlative with TRE with a correlation coefficient of 0.996. For all π-systems studied, MRE has the same sign as TRE. The only trouble with MRE may be that some antiaromatic and non-alternant species exhibit unusually large MRE-to-TRE ratios. This kind of difficulty can in principle be overcome by prior geometry-optimisation or by changing spin multiplicity. Apart from the semi-empirical resonance-theory resonance energy, MRE is considered as the first aromatic stabilisation energy (ASE) defined without referring to any hypothetical polyene reference. PMID:26878709

  20. Simple and Inexpensive Classroom Demonstrations of Nuclear Magnetic Resonance and Magnetic Resonance Imaging.

    ERIC Educational Resources Information Center

    Olson, Joel A.; Nordell, Karen J.; Chesnik, Marla A.; Landis, Clark R.; Ellis, Arthur B.; Rzchowski, M. S.; Condren, S. Michael; Lisensky, George C.

    2000-01-01

    Describes a set of simple, inexpensive, classical demonstrations of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) principles that illustrate the resonance condition associated with magnetic dipoles and the dependence of the resonance frequency on environment. (WRM)

  1. Nuclear magnetic resonance chemical shifts with the statistical average of orbital-dependent model potentials in Kohn-Sham density functional theory

    NASA Astrophysics Data System (ADS)

    Poater, Jordi; van Lenthe, Erik; Baerends, Evert Jan

    2003-05-01

    In this paper, an orbital-dependent Kohn-Sham exchange-correlation potential, the so-called statistical average of (model) orbital potentials, is applied to the calculation of nuclear magnetic resonance chemical shifts of a series of simple molecules containing H, C, N, O, and F. It is shown that the use of this model potential leads to isotropic chemical shifts which are substantially improved over both local and gradient-corrected functionals, especially for nitrogen and oxygen atoms. This improvement in the chemical shift calculations can be attributed to the increase in the gap between highest occupied and lowest unoccupied orbitals, thus correcting the excessively large paramagnetic contributions, which have been identified to give deficient chemical shifts with both the local-density approximation and with gradient-corrected functionals. This is in keeping with the improvement by the statitical average of orbital model potentials for response properties in general and for excitation energies in particular. The present results are comparable in accuracy to those previously reported with self-interaction corrected functionals by Patchovskii et al., but still inferior to those obtained with accurate Kohn-Sham potentials by Wilson and Tozer. However, the present approach is computationally expedient and routinely applicable to all systems, requiring virtually the same computational effort as local-density and generalized-gradient calculations.

  2. Magnetic Resonance Cholangiopancreatography (MRCP)

    MedlinePlus

    ... a powerful magnetic field, radio waves and a computer to evaluate the liver, gallbladder, bile ducts, pancreas ... powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, ...

  3. Noble gas magnetic resonator

    DOEpatents

    Walker, Thad Gilbert; Lancor, Brian Robert; Wyllie, Robert

    2014-04-15

    Precise measurements of a precessional rate of noble gas in a magnetic field is obtained by constraining the time averaged direction of the spins of a stimulating alkali gas to lie in a plane transverse to the magnetic field. In this way, the magnetic field of the alkali gas does not provide a net contribution to the precessional rate of the noble gas.

  4. Basics of magnetic resonance imaging

    SciTech Connect

    Oldendorf, W.; Oldendorf, W. Jr.

    1988-01-01

    Beginning with the behavior of a compass needle in a magnetic field, this text uses analogies from everyday experience to explain the phenomenon of nuclear magnetic resonance and how it is used for imaging. Using a minimum of scientific abbreviations and symbols, the basics of tissue visualization and characterization are presented. A description of the various types of magnets and scanners is followed by the practical advantages and limitations of MRI relative to x-ray CT scanning.

  5. Breast Density in Mammography and Magnetic Resonance Imaging in High Risk Women and Women with Breast Cancer

    PubMed Central

    Albert, Marissa; Schnabel, Freya; Chun, Jennifer; Schwartz, Shira; Lee, Jiyon; Leite, Ana Paula Klautau; Moy, Linda

    2015-01-01

    Structured Abstract Purpose To evaluate the relationship between mammographic breast density (MBD), background parenchymal enhancement (BPE), and fibroglandular tissue (FGT) in women with breast cancer (BC) and at high risk for developing BC. Methods Our institutional database was queried for patients who underwent mammography and MRI. Results 403 (85%) had BC and 72 (15%) were at high risk. MBD (p=0.0005), BPE (p<0.0001), and FGT (p=0.02) were all higher in high risk women compared to the BC group. Conclusions Higher levels of MBD, BPE and FGT are seen in women at higher risk for developing BC when compared to women with BC. PMID:26351036

  6. Optically detected magnetic resonance imaging

    SciTech Connect

    Blank, Aharon; Shapiro, Guy; Fischer, Ran; London, Paz; Gershoni, David

    2015-01-19

    Optically detected magnetic resonance provides ultrasensitive means to detect and image a small number of electron and nuclear spins, down to the single spin level with nanoscale resolution. Despite the significant recent progress in this field, it has never been combined with the power of pulsed magnetic resonance imaging techniques. Here, we demonstrate how these two methodologies can be integrated using short pulsed magnetic field gradients to spatially encode the sample. This result in what we denote as an 'optically detected magnetic resonance imaging' technique. It offers the advantage that the image is acquired in parallel from all parts of the sample, with well-defined three-dimensional point-spread function, and without any loss of spectroscopic information. In addition, this approach may be used in the future for parallel but yet spatially selective efficient addressing and manipulation of the spins in the sample. Such capabilities are of fundamental importance in the field of quantum spin-based devices and sensors.

  7. An Atlas-Based Electron Density Mapping Method for Magnetic Resonance Imaging (MRI)-Alone Treatment Planning and Adaptive MRI-Based Prostate Radiation Therapy

    SciTech Connect

    Dowling, Jason A.; Lambert, Jonathan; Parker, Joel; Salvado, Olivier; Fripp, Jurgen; Capp, Anne; Wratten, Chris; Denham, James W.; Greer, Peter B.

    2012-05-01

    Purpose: Prostate radiation therapy dose planning directly on magnetic resonance imaging (MRI) scans would reduce costs and uncertainties due to multimodality image registration. Adaptive planning using a combined MRI-linear accelerator approach will also require dose calculations to be performed using MRI data. The aim of this work was to develop an atlas-based method to map realistic electron densities to MRI scans for dose calculations and digitally reconstructed radiograph (DRR) generation. Methods and Materials: Whole-pelvis MRI and CT scan data were collected from 39 prostate patients. Scans from 2 patients showed significantly different anatomy from that of the remaining patient population, and these patients were excluded. A whole-pelvis MRI atlas was generated based on the manually delineated MRI scans. In addition, a conjugate electron-density atlas was generated from the coregistered computed tomography (CT)-MRI scans. Pseudo-CT scans for each patient were automatically generated by global and nonrigid registration of the MRI atlas to the patient MRI scan, followed by application of the same transformations to the electron-density atlas. Comparisons were made between organ segmentations by using the Dice similarity coefficient (DSC) and point dose calculations for 26 patients on planning CT and pseudo-CT scans. Results: The agreement between pseudo-CT and planning CT was quantified by differences in the point dose at isocenter and distance to agreement in corresponding voxels. Dose differences were found to be less than 2%. Chi-squared values indicated that the planning CT and pseudo-CT dose distributions were equivalent. No significant differences (p > 0.9) were found between CT and pseudo-CT Hounsfield units for organs of interest. Mean {+-} standard deviation DSC scores for the atlas-based segmentation of the pelvic bones were 0.79 {+-} 0.12, 0.70 {+-} 0.14 for the prostate, 0.64 {+-} 0.16 for the bladder, and 0.63 {+-} 0.16 for the rectum

  8. Role of plasma response in determining density pump-out with Resonant Magnetic Perturbations (RMPs) in DIII-D

    NASA Astrophysics Data System (ADS)

    Mordijck, S.; Smith, S. P.

    2014-10-01

    We are studying the effect of RMPs on the density pump-out threshold in order to determine whether the transport changes are the result of change in turbulence or rotation. Applying RMPs strongly reduces the core rotation and increases the edge rotation, which reduces the ExB shear thus increasing turbulent transport. The toroidal rotation measurements made at two different toroidal location show no phase lag during rotating n = 2 RMP experiment, which is an indication that there is a strong n = 0 response. This n = 0 response could be the result of MHD effects, or due to changes in turbulence characteristics. New low ν* experiments at lower RMP strength allow us to test, whether this change in the toroidal rotation is the main drive behind the increase in particle transport in low collisionality H-mode plasmas on DIII-D as well as examine what is causing the n = 0 response to the toroidal rotation. Work supported in part by the US DOE under DE-SC0007880 and DE-FC02-04ER54698.

  9. GHz nuclear magnetic resonance

    SciTech Connect

    Cross, T.A.; Drobny, G.; Trewhella, J.

    1994-12-01

    For the past dozen years, 500- and 600-MHz spectrometers have become available in many laboratories. The first 600-MHz NMR spectrometer (at Carnegie Mellon University) was commissioned more than 15 years ago and, until 1994, represented the highest field available for high-resolution NMR. This year, we have witnessed unprecedented progress in the development of very high field magnets for NMR spectroscopy, including the delivery of the first commercial 750-MHz NMR spectrometers. In addition, NMR signals have been obtained from 20-Tesla magnets (850 MHz for {sup 1}H`s) at both Los Alamos National Laboratory and Florida State University in the NHMFL (National High Magnetic Field Laboratory). These preliminary experiments have been performed in magnets with 100-ppm homogeneity, but a 20-Tesla magnet developed for the NHMFL will be brought to field this year with a projected homogeneity of 0.1 ppm over a 1-cm-diam spherical volume.

  10. Spin connection resonance in magnetic motors

    NASA Astrophysics Data System (ADS)

    Evans, Myron W.; Eckardt, H.

    2007-11-01

    A mechanism is proposed for rotation of magnetic assemblies by a torque consisting of the magnetic dipole moment of the assembly and a magnetic field generated from space-time in Einstein-Cartan-Evans (ECE) field theory. It is shown that when the magnetic assembly is stationary, the space-time is described by a Helmholtz wave equation in the tetrad as eigenfunction. This is a balance condition in which the Cartan torsion of the space-time is zero, but in which the tetrad and spin connection are non-zero. This balance may be broken by a driving current density produced by the magnetic assembly. The Helmholtz equation becomes an undamped oscillator equation. At resonance the torque on the magnetic assembly may be amplified sufficiently to cause the whole assembly to rotate, as observed experimentally in a repeatable and reproducible manner.

  11. Magnetic resonance apparatus

    DOEpatents

    Jackson, Jasper A.; Cooper, Richard K.

    1982-01-01

    Means for producing a region of homogeneous magnetic field remote from the source of the field, wherein two equal field sources are arranged axially so their fields oppose, producing a region near the plane perpendicular to the axis midway between the sources where the radial component of the field goes through a maximum. Near the maximum, the field is homogeneous over prescribed regions.

  12. Nuclear magnetic resonance spectroscopy

    SciTech Connect

    Harris, R.K.

    1986-01-01

    NMR is remarkable in the number of innovations that have appeared and become established within the past five years. This thoroughly up-to-date account of the field explains fundamentals and applications of the NMR phenomenon from the viewpoint of a physical chemist. Beginning with descriptions of basic concepts involved in continuous wave operation, the book goes on to cover spectral analysis, relaxation phenomena, the effects of pulses, the Fourier transform model, double resonance and the effects of chemical exchange and quadrupolar interactions. The book also includes the new techniques for work on solids and for complicated pulse sequences, plus abundant figures and illustrative spectra.

  13. Magnetic resonance apparatus

    DOEpatents

    Jackson, J.A.; Cooper, R.K.

    1980-10-10

    The patent consists of means for producing a region of homogeneous magnetic field remote from the source of the field, wherein two equal field sources are arranged axially so their fields oppose, producing a region near the plane perpendicular to the axis midway between the sources where the radial correspondent of the field goes through a maximum. Near the maximum, the field is homogeneous over prescribed regions.

  14. Magnetic resonance imaging with an optical atomicmagnetometer

    SciTech Connect

    Xu, Shoujun; Yashchuk, Valeriy V.; Donaldson, Marcus H.; Rochester, Simon M.; Budker, Dmitry; Pines, Alexander

    2006-05-09

    Magnetic resonance imaging (MRI) is a noninvasive andversatile methodology that has been applied in many disciplines1,2. Thedetection sensitivity of conventional Faraday detection of MRI depends onthe strength of the static magnetic field and the sample "fillingfactor." Under circumstances where only low magnetic fields can be used,and for samples with low spin density or filling factor, the conventionaldetection sensitivity is compromised. Alternative detection methods withhigh sensitivity in low magnetic fields are thus required. Here we showthe first use of a laser-based atomic magnetometer for MRI detection inlow fields. Our technique also employs remote detection which physicallyseparates the encoding and detection steps3-5, to improve the fillingfactor of the sample. Potentially inexpensive and using a compactapparatus, our technique provides a novel alternative for MRI detectionwith substantially enhanced sensitivity and time resolution whileavoiding the need for cryogenics.

  15. Pediatric Body Magnetic Resonance Imaging.

    PubMed

    Kandasamy, Devasenathipathy; Goyal, Ankur; Sharma, Raju; Gupta, Arun Kumar

    2016-09-01

    Magnetic resonance imaging (MRI) is a radiation-free imaging modality with excellent contrast resolution and multiplanar capabilities. Since ionizing radiation is an important concern in the pediatric population, MRI serves as a useful alternative to computed tomography (CT) and also provides additional clues to diagnosis, not discernible on other investigations. Magnetic resonance cholangiopancreatography (MRCP), urography, angiography, enterography, dynamic multiphasic imaging and diffusion-weighted imaging provide wealth of information. The main limitations include, long scan time, need for sedation/anesthesia, cost and lack of widespread availability. With the emergence of newer sequences and variety of contrast agents, MRI has become a robust modality and may serve as a one-stop shop for both anatomical and functional information. PMID:26916887

  16. Quartz resonator fluid density and viscosity monitor

    DOEpatents

    Martin, Stephen J.; Wiczer, James J.; Cernosek, Richard W.; Frye, Gregory C.; Gebert, Charles T.; Casaus, Leonard; Mitchell, Mary A.

    1998-01-01

    A pair of thickness-shear mode resonators, one smooth and one with a textured surface, allows fluid density and viscosity to be independently resolved. A textured surface, either randomly rough or regularly patterned, leads to trapping of liquid at the device surface. The synchronous motion of this trapped liquid with the oscillating device surface allows the device to weigh the liquid; this leads to an additional response that depends on liquid density. This additional response enables a pair of devices, one smooth and one textured, to independently resolve liquid density and viscosity; the difference in responses determines the density while the smooth device determines the density-viscosity product, and thus, the pair determines both density and viscosity.

  17. Wide-range nuclear magnetic resonance detector

    NASA Technical Reports Server (NTRS)

    Sturman, J. C.; Jirberg, R. J.

    1972-01-01

    Compact and easy to use solid state nuclear magnetic resonance detector is designed for measuring field strength to 20 teslas in cryogenically cooled magnets. Extremely low noise and high sensitivity make detector applicable to nearly all types of analytical nuclear magnetic resonance measurements and can be used in high temperature and radiation environments.

  18. Evanescent Waves Nuclear Magnetic Resonance

    PubMed Central

    Halidi, El Mohamed; Nativel, Eric; Akel, Mohamad; Kenouche, Samir; Coillot, Christophe; Alibert, Eric; Jabakhanji, Bilal; Schimpf, Remy; Zanca, Michel; Stein, Paul; Goze-Bac, Christophe

    2016-01-01

    Nuclear Magnetic Resonance spectroscopy and imaging can be classified as inductive techniques working in the near- to far-field regimes. We investigate an alternative capacitive detection with the use of micrometer sized probes positioned at sub wavelength distances of the sample in order to characterize and model evanescent electromagnetic fields originating from NMR phenomenon. We report that in this experimental configuration the available NMR signal is one order of magnitude larger and follows an exponential decay inversely proportional to the size of the emitters. Those investigations open a new road to a better understanding of the evanescent waves component in NMR with the opportunity to perform localized spectroscopy and imaging. PMID:26751800

  19. Magnetic resonance imaging of acquired cardiac disease.

    PubMed Central

    Carrol, C L; Higgins, C B; Caputo, G R

    1996-01-01

    Over the last 15 years, advances in magnetic resonance imaging techniques have increased the accuracy and applicability of cardiovascular magnetic resonance imaging. These advances have improved the utility of magnetic resonance imaging in evaluating cardiac morphology, blood flow, and myocardial contractility, all significant diagnostic features in the evaluation of the patient with acquired heart disease. Utilization of cardiovascular magnetic resonance imaging has been limited, primarily due to clinical reliance upon nuclear scintigraphy and echocardiography. Recent developments in fast and ultrafast imaging should continue to enhance the significance of magnetic resonance imaging in this field. Widespread use of magnetic resonance imaging in the evaluation of the cardiovascular system will ultimately depend upon its maturation into a comprehensive, noninvasive imaging technique for the varying manifestations of acquired heart disease, including cardiomyopathy, ischemic heart disease, and acquired valvular disease. Images PMID:8792545

  20. Element Selective X-ray Detected Magnetic Resonance

    SciTech Connect

    Goulon, J.; Rogalev, A.; Wilhelm, F.; Jaouen, N.; Goulon-Ginet, C.; Goujon, G.; Youssef, J. Ben; Indenbom, M. V.

    2007-01-19

    Element selective X-ray Detected Magnetic Resonance (XDMR) was measured on exciting the Fe K-edge in a high quality YIG thin film. Resonant pumping at high microwave power was achieved in the nonlinear foldover regime and X-ray Magnetic Circular Dichroism (XMCD) was used to probe the time-invariant change of the magnetization {delta}Mz due to the precession of orbital magnetization densities of states (DOS) at the Fe sites. This challenging experiment required us to design a specific instrumentation which is briefly described.

  1. Magnetic resonance imaging of the spine

    SciTech Connect

    Modic, M.

    1988-01-01

    MAGNETIC RESONANCE IMAGING OF THE SPINE thoroughly demonstrates the advantages of this new radiologic modality in diagnosing spinal disorders. The book begins with an introductory chapter on the basic physics and technical considerations of magnetic resonance in general and magnetic resonance imaging of the spine in particular. The second chapter covers normal spinal anatomy, and features color photos of multi-planar sections of spinal anatomy.

  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. Tunable Magnetic Resonance in Microwave Spintronics Devices

    NASA Technical Reports Server (NTRS)

    Chen, Yunpeng; Fan, Xin; Xie, Yungsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

    2015-01-01

    Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe-based tunable microwave spintronics devices, which is 10X higher than conventional methods.

  4. Tunable Magnetic Resonance in Microwave Spintronics Devices

    NASA Technical Reports Server (NTRS)

    Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

    2015-01-01

    Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe based tunable microwave spintronics devices, which is 10X higher than conventional methods.

  5. Apparatus for investigating resonance with application to magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Murphy, Sytil; Jones, Dyan L.; Gross, Josh; Zollman, Dean

    2015-11-01

    Resonance is typically studied in the context of either a pendulum or a mass on a spring. We have developed an apparatus that enables beginning students to investigate resonant behavior of changing magnetic fields, in addition to the properties of the magnetic field due to a wire and the superposition of magnetic fields. In this resonant system, a compass oscillates at a frequency determined by the compass's physical properties and an external magnetic field. While the analysis is mathematically similar to that of the pendulum, this apparatus has an advantage that the magnetic field is easily controlled, while it is difficult to control the strength of gravity. This apparatus has been incorporated into a teaching module on magnetic resonance imaging.

  6. MAGNETIC RESONANCE ELASTOGRAPHY: A REVIEW

    PubMed Central

    Mariappan, Yogesh K; Glaser, Kevin J; Ehman, Richard L

    2011-01-01

    Magnetic Resonance Elastography (MRE) is a rapidly developing technology for quantitatively assessing the mechanical properties of tissue. The technology can be considered to be an imaging-based counterpart to palpation, commonly used by physicians to diagnose and characterize diseases. The success of palpation as a diagnostic method is based on the fact that the mechanical properties of tissues are often dramatically affected by the presence of disease processes such as cancer, inflammation, and fibrosis. MRE obtains information about the stiffness of tissue by assessing the propagation of mechanical waves through the tissue with a special magnetic resonance imaging (MRI) technique. The technique essentially involves three steps: generating shear waves in the tissue,acquiring MR images depicting the propagation of the induced shear waves andprocessing the images of the shear waves to generate quantitative maps of tissue stiffness, called elastograms. MRE is already being used clinically for the assessment of patients with chronic liver diseases and is emerging as a safe, reliable and noninvasive alternative to liver biopsy for staging hepatic fibrosis. MRE is also being investigated for application to pathologies of other organs including the brain, breast, blood vessels, heart, kidneys, lungs and skeletal muscle. The purpose of this review article is to introduce this technology to clinical anatomists and to summarize some of the current clinical applications that are being pursued. PMID:20544947

  7. High density plasma etching of magnetic devices

    NASA Astrophysics Data System (ADS)

    Jung, Kee Bum

    Magnetic materials such as NiFe (permalloy) or NiFeCo are widely used in the data storage industry. Techniques for submicron patterning are required to develop next generation magnetic devices. The relative chemical inertness of most magnetic materials means they are hard to etch using conventional RIE (Reactive Ion Etching). Therefore ion milling has generally been used across the industry, but this has limitations for magnetic structures with submicron dimensions. In this dissertation, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma) for the etching of magnetic materials (NiFe, NiFeCo, CoFeB, CoSm, CoZr) and other related materials (TaN, CrSi, FeMn), which are employed for magnetic devices like magnetoresistive random access memories (MRAM), magnetic read/write heads, magnetic sensors and microactuators. This research examined the fundamental etch mechanisms occurring in high density plasma processing of magnetic materials by measuring etch rate, surface morphology and surface stoichiometry. However, one concern with using Cl2-based plasma chemistry is the effect of residual chlorine or chlorinated etch residues remaining on the sidewalls of etched features, leading to a degradation of the magnetic properties. To avoid this problem, we employed two different processing methods. The first one is applying several different cleaning procedures, including de-ionized water rinsing or in-situ exposure to H2, O2 or SF6 plasmas. Very stable magnetic properties were achieved over a period of ˜6 months except O2 plasma treated structures, with no evidence of corrosion, provided chlorinated etch residues were removed by post-etch cleaning. The second method is using non-corrosive gas chemistries such as CO/NH3 or CO2/NH3. There is a small chemical contribution to the etch mechanism (i.e. formation of metal carbonyls) as determined by a comparison with Ar and N2 physical sputtering. The discharge should be NH3

  8. Advances in mechanical detection of magnetic resonance

    PubMed Central

    Kuehn, Seppe; Hickman, Steven A.; Marohn, John A.

    2008-01-01

    The invention and initial demonstration of magnetic resonance force microscopy (MRFM) in the early 1990s launched a renaissance of mechanical approaches to detecting magnetic resonance. This article reviews progress made in MRFM in the last decade, including the demonstration of scanned probe detection of magnetic resonance (electron spin resonance, ferromagnetic resonance, and nuclear magnetic resonance) and the mechanical detection of electron spin resonance from a single spin. Force and force-gradient approaches to mechanical detection are reviewed and recent related work using attonewton sensitivity cantilevers to probe minute fluctuating electric fields near surfaces is discussed. Given recent progress, pushing MRFM to single proton sensitivity remains an exciting possibility. We will survey some practical and fundamental issues that must be resolved to meet this challenge. PMID:18266413

  9. Torque-mixing magnetic resonance spectroscopy.

    PubMed

    Losby, J E; Fani Sani, F; Grandmont, D T; Diao, Z; Belov, M; Burgess, J A J; Compton, S R; Hiebert, W K; Vick, D; Mohammad, K; Salimi, E; Bridges, G E; Thomson, D J; Freeman, M R

    2015-11-13

    A universal, torque-mixing method for magnetic resonance spectroscopy is presented. In analogy to resonance detection by magnetic induction, the transverse component of a precessing dipole moment can be measured in sensitive broadband spectroscopy, here using a resonant mechanical torque sensor. Unlike induction, the torque amplitude allows equilibrium magnetic properties to be monitored simultaneously with the spin dynamics. Comprehensive electron spin resonance spectra of a single-crystal, mesoscopic yttrium iron garnet disk at room temperature reveal assisted switching between magnetization states and mode-dependent spin resonance interactions with nanoscale surface imperfections. The rich detail allows analysis of even complex three-dimensional spin textures. The flexibility of microelectromechanical and optomechanical devices combined with broad generality and capabilities of torque-mixing magnetic resonance spectroscopy offers great opportunities for development of integrated devices. PMID:26564851

  10. Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance Three Axis Vector Magnetometer

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Larsen, Michael; Mirijanian, James

    2012-06-01

    The Northrop Grumman Corporation is leveraging the technology developed for the Nuclear Magnetic Resonance Gyroscope (NMRG) to build a combined Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance (EPR-NMR) magnetometer. The EPR-NMR approach provides a high bandwidth and high sensitivity simultaneous measurement of all three vector components of the magnetic field averaged over the small volume of the sensor's one vapor cell. This poster will describe the history, operational principles, and design basics of the EPR-NMR magnetometer including an overview of the NSD designs developed and demonstrated to date. General performance results will also be presented.

  11. Functional Magnetic Resonance Imaging Methods

    PubMed Central

    Chen, Jingyuan E.; Glover, Gary H.

    2015-01-01

    Since its inception in 1992, Functional Magnetic Resonance Imaging (fMRI) has become an indispensible tool for studying cognition in both the healthy and dysfunctional brain. FMRI monitors changes in the oxygenation of brain tissue resulting from altered metabolism consequent to a task-based evoked neural response or from spontaneous fluctuations in neural activity in the absence of conscious mentation (the “resting state”). Task-based studies have revealed neural correlates of a large number of important cognitive processes, while fMRI studies performed in the resting state have demonstrated brain-wide networks that result from brain regions with synchronized, apparently spontaneous activity. In this article, we review the methods used to acquire and analyze fMRI signals. PMID:26248581

  12. Magnetic resonance elastography of abdomen.

    PubMed

    Venkatesh, Sudhakar Kundapur; Ehman, Richard L

    2015-04-01

    Many diseases cause substantial changes in the mechanical properties of tissue, and this provides motivation for developing methods to noninvasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate noninvasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed. PMID:25488346

  13. Magnetic Resonance Elastography of Abdomen

    PubMed Central

    Venkatesh, Sudhakar K.; Ehman, Richard L.

    2015-01-01

    Many diseases cause substantial changes in the mechanical properties of tissue and this provides motivation for developing methods to non-invasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate non-invasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed. PMID:25488346

  14. Enhancement of Magnetic Resonance Imaging with Metasurfaces.

    PubMed

    Slobozhanyuk, Alexey P; Poddubny, Alexander N; Raaijmakers, Alexander J E; van den Berg, Cornelis A T; Kozachenko, Alexander V; Dubrovina, Irina A; Melchakova, Irina V; Kivshar, Yuri S; Belov, Pavel A

    2016-03-01

    It is revealed that the unique properties of ultrathin metasurface resonators can improve magnetic resonance imaging dramatically. A metasurface formed when an array of metallic wires is placed inside a scanner under the studied object and a substantial enhancement of the radio-frequency magnetic field is achieved by means of subwavelength manipulation with the metasurface, also allowing improved image resolution. PMID:26754827

  15. Chemical Principles Revisited. Proton Magnetic Resonance Spectroscopy.

    ERIC Educational Resources Information Center

    McQuarrie, Donald A.

    1988-01-01

    Discusses how to interpret nuclear magnetic resonance (NMR) spectra and how to use them to determine molecular structures. This discussion is limited to spectra that are a result of observation of only the protons in a molecule. This type is called proton magnetic resonance (PMR) spectra. (CW)

  16. Magnetic resonance imaging of radiation optic neuropathy

    SciTech Connect

    Zimmerman, C.F.; Schatz, N.J.; Glaser, J.S. )

    1990-10-15

    Three patients with delayed radiation optic neuropathy after radiation therapy for parasellar neoplasms underwent magnetic resonance imaging. The affected optic nerves and chiasms showed enlargement and focal gadopentetate dimeglumine enhancement. The magnetic resonance imaging technique effectively detected and defined anterior visual pathway changes of radionecrosis and excluded the clinical possibility of visual loss because of tumor recurrence.

  17. Functional Magnetic Resonance Imaging and Pediatric Anxiety

    ERIC Educational Resources Information Center

    Pine, Daniel S.; Guyer, Amanda E.; Leibenluft, Ellen; Peterson, Bradley S.; Gerber, Andrew

    2008-01-01

    The use of functional magnetic resonance imaging in investigating pediatric anxiety disorders is studied. Functional magnetic resonance imaging can be utilized in demonstrating parallels between the neural architecture of difference in anxiety of humans and the neural architecture of attention-orienting behavior in nonhuman primates or rodents.…

  18. Magnetic resonance imaging of glioblastoma using aptamer conjugated magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Bongjune; Yang, Jaemoon; Hwang, Myeonghwan; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo

    2012-10-01

    Here we introduce a new class of smart imaging probes hybridizing polysorbate 80 coated-magnetic nanoparticles with vascular endothelial growth factor receptor 2 (VEGFR2)-targetable aptamer for specific magnetic resonance (MR) imaging of angiogenesis from glioblastoma.

  19. Impact of steam explosion on the wheat straw lignin structure studied by solution-state nuclear magnetic resonance and density functional methods.

    PubMed

    Heikkinen, Harri; Elder, Thomas; Maaheimo, Hannu; Rovio, Stella; Rahikainen, Jenni; Kruus, Kristiina; Tamminen, Tarja

    2014-10-29

    Chemical changes of lignin induced by the steam explosion (SE) process were elucidated. Wheat straw was studied as the raw material, and lignins were isolated by the enzymatic mild acidolysis lignin (EMAL) procedure before and after the SE treatment for analyses mainly by two-dimensional (2D) [heteronuclear single-quantum coherence (HSQC) and heteronuclear multiple-bond correlation (HMBC)] and (31)P nuclear magnetic resonance (NMR). The β-O-4 structures were found to be homolytically cleaved, followed by recoupling to β-5 linkages. The homolytic cleavage/recoupling reactions were also studied by computational methods, which verified their thermodynamic feasibility. The presence of the tricin bound to wheat straw lignin was confirmed, and it was shown to participate in lignin reactions during the SE treatment. The preferred homolytic β-O-4 cleavage reaction was calculated to follow bond dissociation energies: G-O-G (guaiacyl) (69.7 kcal/mol) > G-O-S (syringyl) (68.4 kcal/mol) > G-O-T (tricin) (67.0 kcal/mol). PMID:25290760

  20. Fermionic density functional at a Feshbach resonance

    SciTech Connect

    Seidl, Michael; Bhaduri, Rajat K.

    2007-05-15

    We consider a dilute gas of neutral unpolarized fermionic atoms at zero temperature. The atoms interact via a short-range (tunable) attractive interaction. We demonstrate analytically a curious property of the gas at unitarity. Namely, the correlation energy of the gas, evaluated by second-order perturbation theory, has the same density dependence as the first-order exchange energy, and the two almost exactly cancel each other at a Feshbach resonance irrespective of the shape of the potential, provided ({mu}r{sub s})>>1. Here ({mu}){sup -1} is the range of the two-body potential, and r{sub s} is defined through the number density, n=3/(4{pi}r{sub s}{sup 3}). The implications of this result for universality are discussed.

  1. Tunable Magnetic Resonance via Interlayer Exchange Interaction

    NASA Astrophysics Data System (ADS)

    Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Wilson, Jeffrey; Simons, Rainee; Chui, Sui-Tat; Xiao, John

    Magnetic resonance is a critical property of magnetic materials for the applications in microwave devices and novel spintronics devices. The resonance frequency is commonly controlled with an external magnetic field generated by an energy-inefficient and bulky electromagnet. The search for tuning the resonance frequency without electromagnets has attracted tremendous attention. The voltage control of resonance frequency has been demonstrated in multiferroic heterostructures through magnetoelastic effect. However, the frequency tunable range is limited. We propose a paradigm to tune the magnetic resonance frequency by recognizing the huge interlayer exchange field and the existence of the high-frequency modes in coupled oscillators. We demonstrate the optical mode in exchange coupled magnetic layers which occurred at much higher frequencies than coherent ferromagnetic resonance. We further demonstrated a large resonance frequency tunable range from 11GHz to 21 GHz in a spin valve device by in-situ manipulating of the exchange interaction. The technique developed here is far more efficient than the conventional methods of using electromagnets and multiferroics. This new scheme will have an immediate impact on applications based on magnetic resonance.

  2. Artifacts in Magnetic Resonance Imaging

    PubMed Central

    Krupa, Katarzyna; Bekiesińska-Figatowska, Monika

    2015-01-01

    Summary Artifacts in magnetic resonance imaging and foreign bodies within the patient’s body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients’ bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature. PMID:25745524

  3. Stepped Impedance Resonators for High Field Magnetic Resonance Imaging

    PubMed Central

    Akgun, Can E.; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J.; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J. Thomas

    2014-01-01

    Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high field magnetic resonance imaging (MRI). In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) multi-element transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections referred to as stepped impedance resonators (SIRs) is investigated. Single element simulation results in free space and in a phantom at 7 tesla (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 tesla in a phantom and human head illustrate the improvements in transmit magnetic field, as well as, RF efficiency (transmit magnetic field versus SAR) when two different SIR designs are incorporated in 8-element volume coil configurations and compared to a volume coil consisting of microstrip elements. PMID:23508243

  4. Electron density distribution in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides studied by double nuclear magnetic resonance methods

    SciTech Connect

    Piskunov, Yu. V. Ogloblichev, V. V.; Arapova, I. Yu.; Sadykov, A. V.; Gerashchenko, A. P.; Verkhovskii, S. V.

    2011-11-15

    The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of {sup 17}O are measured systematically, and the contributions from {sup 17}O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of {sup 17}O-{sup 207}Pb and {sup 17}O-{sup 121}Sb are measured in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin {sup 17}O-{sup 207}Pb interaction are determined as functions of the local Knight shift {sub 207}Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of {sup 17}O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides.

  5. Electron density distribution in BaPb1 - x Sb x O3 superconducting oxides studied by double nuclear magnetic resonance methods

    NASA Astrophysics Data System (ADS)

    Piskunov, Yu. V.; Ogloblichev, V. V.; Arapova, I. Yu.; Sadykov, A. V.; Gerashchenko, A. P.; Verkhovskii, S. V.

    2011-11-01

    The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb1 - x Sb x O3 superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of 17O are measured systematically, and the contributions from 17O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of 17O-207Pb and 17O-121Sb are measured in the metal phase of BaPb1 - x Sb x O3 oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin 17O-207Pb interaction are determined as functions of the local Knight shift 207 Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of 17O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb1 - x Sb x O3 oxides.

  6. Enhancement of artificial magnetism via resonant bianisotropy.

    PubMed

    Markovich, Dmitry; Baryshnikova, Kseniia; Shalin, Alexander; Samusev, Anton; Krasnok, Alexander; Belov, Pavel; Ginzburg, Pavel

    2016-01-01

    All-dielectric "magnetic light" nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses. PMID:26941126

  7. Enhancement of artificial magnetism via resonant bianisotropy

    NASA Astrophysics Data System (ADS)

    Markovich, Dmitry; Baryshnikova, Kseniia; Shalin, Alexander; Samusev, Anton; Krasnok, Alexander; Belov, Pavel; Ginzburg, Pavel

    2016-03-01

    All-dielectric “magnetic light” nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses.

  8. Drift Resonance in High Density Nonneutral Plasmas

    NASA Astrophysics Data System (ADS)

    Kaup, D. J.

    2005-10-01

    Theoretical studies of the operation of crossed-field electron vacuum devices, such as magnetrons and crossed-field amplifiers (CFA), have usually centered on their initial growth, taking this as an indication of their operating modes. In such an analysis, one solves the equations for the density profile and other features of these devices. However what one actually obtains are only the conditions for the initial operation of the device. Eventually the rf fields will saturate, at which time, an operating device will settle into a stationary operating regime, called the ``saturation stage,'' which is where the device simply delivers rf power. Here there is a different set of physical interactions occuring. The amplitudes have saturated and the ponderomotive forces and nonlinear diffusion of the initiation stage have vanished. In this saturation stage, we now find three new rf modes appearing, in addition to the two modes of the initiation stage. These three new modes have very fast oscillations in the vertical direction: one fast mode corresponds to a plasma drift wave, while the other two fast modes are cyclotron-like modes. In this presentation, we will describe how the fast plasma drift wave interacts with the slow modes at the diocotron resonance. In particular, we will determine the conversion coefficients for the crossing of the drift mode with the slow modes at the diocotron resonance.

  9. The LC resonance probe for determining local plasma density

    NASA Astrophysics Data System (ADS)

    Boris, D. R.; Fernsler, R. F.; Walton, S. G.

    2011-04-01

    We present a novel plasma diagnostic for measuring local plasma density in reactive-gas plasmas, and depositing plasmas. The diagnostic uses a network analyzer to measure the LC resonance (LCR) frequency of a parallel plate capacitor with inductive leads. The location of the LCR (ωR) in frequency space is then used as a measure of the plasma dielectric constant bold varepsilonp between the plates. By properly constructing the LCR probe, ωR can be tuned such that ωR Gt ωce, where ωce is the electron-cyclotron frequency. Thus, the probe can be used in plasmas with varying degrees of magnetization while avoiding complications introduced to bold varepsilonp when ω is comparable to ωce. Density measurements from the LCR probe are compared with Langmuir probe measurements in an electron-beam generated plasma in which density varied from 109 to 1011 cm-3. An axial magnetic field, typically used to confine the electron beam, was varied between 0 to 300 G. The LCR probe showed good agreement with a Langmuir probe across the entire range of magnetic fields.

  10. Pocket atlas of cranial magnetic resonance imaging

    SciTech Connect

    Haughton, V.M.; Daniels, D.L.

    1986-01-01

    This atlas illustrates normal cerebral anatomy in magnetic resonance images. From their studies in cerebral anatomy utilizing cryomicrotome and other techniques, the authors selected more than 100 high-resolution images that represent the most clinically useful scans.

  11. Chronic liver disease: evaluation by magnetic resonance

    SciTech Connect

    Stark, D.D.; Goldberg, H.I.; Moss, A.A.; Bass, N.M.

    1984-01-01

    Magnetic resonance (MR) imaging distinguished hepatitis from fatty liver and cirrhosis in a woman with a history of alcohol abuse. Anatomic and physiologic manifestations of portal hypertension were also demonstrated by MR.

  12. Your Radiologist Explains Magnetic Resonance Angiography (MRA)

    MedlinePlus Videos and Cool Tools

    ... talk with you about magnetic resonance angiography, or as it’s commonly known, MRA. MRA is a noninvasive ... possibility that you’re pregnant tell your doctor as well. On the day of your exam, it’s ...

  13. International Society for Magnetic Resonance in Medicine

    MedlinePlus

    ... Upcoming Workshops & Deadlines Past Workshops Endorsed Meetings & Education International Outreach Event Planning Guides Education MR Safety Resources ... Center E-Library Virtual Meetings Connect With Us International Society for Magnetic Resonance in Medicine 2300 Clayton ...

  14. Coronary Computed Tomography and Magnetic Resonance Imaging

    PubMed Central

    Kantor, Birgit; Nagel, Eike; Schoenhagen, Paul; Barkhausen, Jörg; Gerber, Thomas C.

    2009-01-01

    Cardiac computed tomography and magnetic resonance are relatively new imaging modalities that can exceed the ability of established imaging modalities to detect present pathology or predict patient outcomes. Coronary calcium scoring may be useful in asymptomatic patients at intermediate risk. Computed tomographic coronary angiography is a first-line indication to evaluate congenitally abnormal coronary arteries and, along with stress magnetic resonance myocardial perfusion imaging, is useful in symptomatic patients with nondiagnostic conventional stress tests. Cardiac magnetic resonance is indicated for visualizing cardiac structure and function, and delayed enhancement magnetic resonance is a first-line indication for assessing myocardial viability. Imaging plaque and molecular mechanisms related to plaque rupture holds great promise for the presymptomatic detection of patients at risk for coronary events but is not yet suitable for routine clinical use. PMID:19269527

  15. Magnetic resonance of calcified tissues

    NASA Astrophysics Data System (ADS)

    Wehrli, Felix W.

    2013-04-01

    MRI of the human body is largely made possible by the favorable relaxation properties of protons of water and triacyl glycerides prevalent in soft tissues. Hard tissues - key among them bone - are generally less amenable to measurement with in vivo MR imaging techniques, not so much as a result of the lower proton density but rather due to the extremely short life-times of the proton signal in water bound to solid-like entities, typically collagen, or being trapped in micro-pores. Either mechanism can enhance T2 relaxation by up to three orders of magnitude relative to their soft-tissue counterparts. Detection of these protons requires solid-state techniques that have emerged in recent years and that promise to add a new dimension to the study of hard tissues. Alternative approaches to probe calcified tissues exploit their characteristic magnetic properties. Bone, teeth and extra-osseous calcium-containing biomaterials are unique in that they are more diamagnetic than all other tissues and thus yield information indirectly by virtue of the induced magnetic fields present in their vicinity. Progress has also been made in methods allowing very high-resolution structural imaging of trabecular and cortical bone relying on detection of the surrounding soft-tissues. This brief review, much of it drawn from work conducted in the author's laboratory, seeks to highlight opportunities with focus on early-stage developments for image-based assessment of structure, function, physiology and mechanics of calcified tissues in humans via liquid and solid-state approaches, including proton, deuteron and phosphorus NMR and MRI.

  16. Torque-mixing Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Losby, Joseph; Fani Sani, Fatemeh; Grandmont, Dylan; Diao, Zhu; Belov, Miro; Burgess, Jacob; Compton, Shawn; Hiebert, Wayne; Vick, Doug; Mohammad, Kaveh; Salimi, Elham; Bridges, Gregory; Thomson, Douglas; Freeman, Mark

    A universal, mechanical torque method for magnetic resonance spectroscopy is presented. In analogy to resonance detection by induction, a signal proportional to the transverse component of a precessing dipole moment can be measured as a pure mechanical torque in broadband, frequency-swept spectroscopy. Comprehensive electron spin resonance of a single-crystal, mesoscopic yttrium iron garnet disk at room temperature are presented to demonstrate the method. The rich detail allows analysis of even complex 3D spin textures.

  17. Implementation of NMR pulse sequences for Magnetic Resonance Force Microscopy

    NASA Astrophysics Data System (ADS)

    Moores, Bradley; Eichler, Alexander; Degen, Christian

    2014-03-01

    Magnetic resonance force microscopy (MRFM) is a scanning microscopy technique that allows measuring nuclear spin densities with a resolution of a few nanometers. Ongoing efforts are aiming at improving this resolution, which might ultimately facilitate non-destructive 3D scans of complex molecules or solid state systems with atomic resolution. Here, we review our current efforts to utilize in an MRFM experiment pulsing techniques borrowed from the nuclear magnetic resonance community. The use of advanced pulsing schemes may improve signal-to-noise ratio, imaging resolution, and allow the investigation of novel phenomena.

  18. Selectivity in multiple quantum nuclear magnetic resonance

    SciTech Connect

    Warren, W.S.

    1980-11-01

    The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.

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

    DOEpatents

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

    2016-02-09

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

  20. Magnetic Fluctuations in Pair-Density-Wave Superconductors.

    PubMed

    Christensen, Morten H; Jacobsen, Henrik; Maier, Thomas A; Andersen, Brian M

    2016-04-22

    Pair-density-wave superconductivity constitutes a novel electronic condensate proposed to be realized in certain unconventional superconductors. Establishing its potential existence is important for our fundamental understanding of superconductivity in correlated materials. Here we compute the dynamical magnetic susceptibility in the presence of a pair-density-wave ordered state and study its fingerprints on the spin-wave spectrum including the neutron resonance. In contrast to the standard case of d-wave superconductivity, we show that the pair-density-wave phase exhibits neither a spin gap nor a magnetic resonance peak, in agreement with a recent neutron scattering experiment on underdoped La_{1.905}Ba_{0.095}CuO_{4} [Z. Xu et al., Phys. Rev. Lett. 113, 177002 (2014)]. PMID:27152819

  1. Magnetic Fluctuations in Pair-Density-Wave Superconductors

    NASA Astrophysics Data System (ADS)

    Christensen, Morten H.; Jacobsen, Henrik; Maier, Thomas A.; Andersen, Brian M.

    2016-04-01

    Pair-density-wave superconductivity constitutes a novel electronic condensate proposed to be realized in certain unconventional superconductors. Establishing its potential existence is important for our fundamental understanding of superconductivity in correlated materials. Here we compute the dynamical magnetic susceptibility in the presence of a pair-density-wave ordered state and study its fingerprints on the spin-wave spectrum including the neutron resonance. In contrast to the standard case of d -wave superconductivity, we show that the pair-density-wave phase exhibits neither a spin gap nor a magnetic resonance peak, in agreement with a recent neutron scattering experiment on underdoped La1.905 Ba0.095 CuO4 [Z. Xu et al., Phys. Rev. Lett. 113, 177002 (2014)].

  2. Children's (Pediatric) Magnetic Resonance Imaging

    MedlinePlus

    ... a powerful magnetic field, radio waves and a computer to produce detailed pictures of the inside of ... powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, ...

  3. Magnetic Resonance Imaging (MRI) - Spine

    MedlinePlus

    ... uses radio waves, a magnetic field and a computer to produce detailed pictures of the spine and ... powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, ...

  4. Magnetic Resonance Studies of Energy Storage Materials

    NASA Astrophysics Data System (ADS)

    Vazquez Reina, Rafael

    In today's society there is high demand to have access to energy for portable devices in different forms. Capacitors with high performance in small package to achieve high charge/discharge rates, and batteries with their ability to store electricity and make energy mobile are part of this demand. The types of internal dielectric material strongly affect the characteristics of a capacitor, and its applications. In a battery, the choice of the electrolyte plays an important role in the Solid Electrolyte Interphase (SEI) formation, and the cathode material for high output voltage. Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) spectroscopy are research techniques that exploit the magnetic properties of the electron and certain atomic nuclei to determine physical and chemical properties of the atoms or molecules in which they are contained. Both EPR and NMR spectroscopy technique can yield meaningful structural and dynamic information. Three different projects are discussed in this dissertation. First, High energy density capacitors where EPR measurements described herein provide an insight into structural and chemical differences in the dielectric material of a capacitor. Next, as the second project, Electrolyte solutions where an oxygen-17 NMR study has been employed to assess the degree of preferential solvation of Li+ ions in binary mixtures of EC (ethylene carbonate) and DMC (dimethyl carbonate) containing LiPF6 (lithium hexafluo-rophosphate) which may be ultimately related to the SEI formation mechanism. The third project was to study Bismuth fluoride as cathode material for rechargeable batteries. The objective was to study 19F and 7Li MAS NMR of some nanocomposite cathode materials as a conversion reaction occurring during lithiation and delithation of the BiF3/C nanocomposite.

  5. Trapped Ion Magnetic Resonance: Concepts and Designs

    NASA Astrophysics Data System (ADS)

    Pizarro, Pedro Jose

    A novel spectroscopy of trapped ions is proposed which will bring single-ion detection sensitivity to the observation of magnetic resonance spectra and resolve the apparent incompatibility in existing techniques between high information content and high sensitivity. Methods for studying both electron spin resonance (ESR) and nuclear magnetic resonance (NMR) are designed. They assume established techniques for trapping ions in high magnetic field and observing electrically the trapping frequencies with high resolution (<1 Hz) and sensitivity (single -ion). A magnetic bottle field gradient couples the spin and spatial motions together and leads to the small spin -dependent force on the ion exploited by Dehmelt to observe directly the perturbation of the ground-state electron's axial frequency by its spin magnetic moment. A series of fundamental innovations is described to extend magnetic resonance to molecular ions ( cong 100 amu) and nuclear magnetic moments. It is demonstrated how time-domain trapping frequency observations before and after magnetic resonance can be used to make cooling of the particle to its ground state unnecessary. Adiabatic cycling of the magnetic bottle off between detection periods is shown to be practical and to allow high-resolution magnetic resonance to be encoded pointwise as the presence or absence of trapping frequency shifts. Methods of inducing spin -dependent work on the ion orbits with magnetic field gradients and Larmor frequency irradiation are proposed which greatly amplify the attainable shifts in trapping frequency. The first proposal presented builds on Dehmelt's experiment to reveal ESR spectra. A more powerful technique for ESR is then designed where axially synchronized spin transitions perform spin-dependent work in the presence of a magnetic bottle, which also converts axial amplitude changes into cyclotron frequency shifts. The most general approach presented is a continuous Stern-Gerlach effect in which a magnetic field

  6. Designing dielectric resonators on substrates: combining magnetic and electric resonances.

    PubMed

    van de Groep, J; Polman, A

    2013-11-01

    High-performance integrated optics, solar cells, and sensors require nanoscale optical components at the surface of the device, in order to manipulate, redirect and concentrate light. High-index dielectric resonators provide the possibility to do this efficiently with low absorption losses. The resonances supported by dielectric resonators are both magnetic and electric in nature. Combined scattering from these two can be used for directional scattering. Most applications require strong coupling between the particles and the substrate in order to enhance the absorption in the substrate. However, the coupling with the substrate strongly influences the resonant behavior of the particles. Here, we systematically study the influence of particle geometry and dielectric environment on the resonant behavior of dielectric resonators in the visible to near-IR spectral range. We show the key role of retardation in the excitation of the magnetic dipole (MD) mode, as well as the limit where no MD mode is supported. Furthermore, we study the influence of particle diameter, shape and substrate index on the spectral position, width and overlap of the electric dipole (ED) and MD modes. Also, we show that the ED and MD mode can selectively be enhanced or suppressed using multi-layer substrates. And, by comparing dipole excitation and plane wave excitation, we study the influence of driving field on the scattering properties. Finally, we show that the directional radiation profiles of the ED and MD modes in resonators on a substrate are similar to those of point-dipoles close to a substrate. Altogether, this work is a guideline how to tune magnetic and electric resonances for specific applications. PMID:24216852

  7. Investigation of laser polarized xenon magnetic resonance

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.

    1998-01-01

    Ground-based investigations of a new biomedical diagnostic technology: nuclear magnetic resonance of laser polarized noble gas are addressed. The specific research tasks discussed are: (1) Development of a large-scale noble gas polarization system; (2) biomedical investigations using laser polarized noble gas in conventional (high magnetic field) NMR systems; and (3) the development and application of a low magnetic field system for laser polarized noble gas NMR.

  8. Compression-sensitive magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Hirsch, Sebastian; Beyer, Frauke; Guo, Jing; Papazoglou, Sebastian; Tzschaetzsch, Heiko; Braun, Juergen; Sack, Ingolf

    2013-08-01

    Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary to the shear elastic properties of tissue, the compression modulus may be a clinically useful biomarker because it is sensitive to tissue pressure and poromechanical interactions. In this work, we analyze the capability of MRE to measure volumetric strain and the dynamic bulk modulus (P-wave modulus) at a harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing CO2-filled cavities to establish a compressible effective medium. The dependence of the effective medium's bulk modulus on phantom density was investigated via static compression tests, which confirmed theoretical predictions. The P-wave modulus of three compressible phantoms was calculated from volumetric strain measured by 3D wave-field MRE at 50 Hz drive frequency. The results demonstrate the MRE-derived volumetric strain and P-wave modulus to be sensitive to the compression properties of effective media. Since the reconstruction of the P-wave modulus requires third-order derivatives, noise remains critical, and P-wave moduli are systematically underestimated. Focusing on relative changes in the effective bulk modulus of tissue, compression-sensitive MRE may be useful for the noninvasive detection of diseases involving pathological pressure alterations such as hepatic hypertension or hydrocephalus.

  9. Compression-sensitive magnetic resonance elastography.

    PubMed

    Hirsch, Sebastian; Beyer, Frauke; Guo, Jing; Papazoglou, Sebastian; Tzschaetzsch, Heiko; Braun, Juergen; Sack, Ingolf

    2013-08-01

    Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary to the shear elastic properties of tissue, the compression modulus may be a clinically useful biomarker because it is sensitive to tissue pressure and poromechanical interactions. In this work, we analyze the capability of MRE to measure volumetric strain and the dynamic bulk modulus (P-wave modulus) at a harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing CO2-filled cavities to establish a compressible effective medium. The dependence of the effective medium's bulk modulus on phantom density was investigated via static compression tests, which confirmed theoretical predictions. The P-wave modulus of three compressible phantoms was calculated from volumetric strain measured by 3D wave-field MRE at 50 Hz drive frequency. The results demonstrate the MRE-derived volumetric strain and P-wave modulus to be sensitive to the compression properties of effective media. Since the reconstruction of the P-wave modulus requires third-order derivatives, noise remains critical, and P-wave moduli are systematically underestimated. Focusing on relative changes in the effective bulk modulus of tissue, compression-sensitive MRE may be useful for the noninvasive detection of diseases involving pathological pressure alterations such as hepatic hypertension or hydrocephalus. PMID:23852144

  10. Nuclear Magnetic Resonance Technology for Medical Studies

    NASA Astrophysics Data System (ADS)

    Budinger, Thomas F.; Lauterbur, Paul C.

    1984-10-01

    Nuclear magnetic resonance proton imaging provides anatomical definition of normal and abnormal tissues with a contrast and detection sensitivity superior to those of x-ray computed tomography in the human head and pelvis and parts of the cardiovascular and musculoskeletal systems. Recent improvements in technology should lead to advances in diagnostic imaging of the breast and regions of the abdomen. Selected-region nuclear magnetic resonance spectroscopy of protons, carbon-13, and phosphorus-31 has developed into a basic science tool for in vivo studies on man and a unique tool for clinical diagnoses of metabolic disorders. At present, nuclear magnetic resonance is considered safe if access to the magnet environment is controlled. Technological advances employing field strengths over 2 teslas will require biophysical studies of heating and static field effects.

  11. Low-temperature magnetic resonance force microscopy

    NASA Astrophysics Data System (ADS)

    Wago, Koichi

    Magnetic resonance force microscopy (MRFM) is a technique whose goal is to combine the three-dimensional, chemically specific imaging capability of magnetic resonance imaging with the atomic-scale spatial resolution of scanning force microscopy. MRFM relies on the detection of small oscillatory magnetic forces between spins in the sample and a magnetic tip, using a micromechanical cantilever. The force resolution is a key issue for successfully operating MRFM experiments. Operating at low temperature improves the force resolution because of the reduced thermal energy and increased mechanical Q of the cantilever. The spin polarization is also enhanced at low temperature, leading to the improved magnetic resonance sensitivity for ensemble spin samples. A low-temperature magnetic resonance force detection apparatus was built and used to demonstrate a force resolution of 8×10sp{-17}\\ N/sqrt{Hz} at 6 K with a commercial single-crystal silicon cantilever. Both nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) were detected in micron-size samples. Force-detection technique was also applied to a wide range of magnetic resonance measurements, including inversion recovery, nutation, and spin echoes. Force-detected EPR spectra of phosphorus-doped silicon revealed hyperfine splitting, illustrating the possibility of using the MRFM technique for spectroscopic purposes. An improved low-temperature magnetic resonance force microscope was also built, incorporating a magnetic tip mounted directly on the cantilever. This allows a much wider variety of samples to be investigated and greatly improves the convenience of the technique. Using the improved microscope, three-dimensional EPR imaging of diphenylpicrylhydrazil (DPPH) particles was accomplished by scanning the sample in two dimensions while stepping an external field. The EPR force map showed a broad response reflecting the size and shape of the sample, allowing a three-dimensional real

  12. Resonant excitation of density waves in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny

    1996-06-01

    The dynamics of regions in the Saturnian ring system with rare collisions between particles, that is, Ω 2≫ν c2, where Ω is the orbital angular frequency and νc the collision frequency, is considered. According to observations, such low optical depth regions can be found in the C ring, the inner portions of the B ring and the A ring. Kinetic theory with the Vlasov and Poisson equations is used to obtain the eigen-frequencies of oscillations propagating in the plane of the system. In the considered case of rare collisions the resulting kinetic equation for the perturbed distribution function can be solved by successive approximations, neglecting the effect of binary particle collisions in the zeroth-order approximation. An oscillating instability of the kinetic type is discussed. This instability of a particulate disk is similar to the magneto-drift instability first discovered by Krall and Rosenbluth ( Physics Fluids6, 254-265, 1963) in a nonuniform magnetic plasma, and belongs to the class of microinstabilities of an inhomogeneous plasma. The cause of the oscillating instability in Saturn's rings is a resonant interaction of drifting particles with nonaxisymmetric Jeans-stable waves at the corotation. The waves that may be produced by the corotation-resonance interaction represent non-radial normal modes of the gravitationally stable disk modified by a particle drift. It is shown that density waves are effectively excited at this resonance: the growth rate of the mode of maximum instability is large, Im ω∗˜Ω. The resonant excitation of density waves investigated in the present paper may be proposed as the cause of the irregular, small-scale ˜ 100 m structure in regions of low optical depth in Saturn's rings. It is suggested that Cassini spacecraft high-resolution images of low optical depth regions will show this kind of structure.

  13. Cyclotron resonance in an inhomogeneous magnetic field

    SciTech Connect

    Albert, J.M. )

    1993-08-01

    Relativistic test particles interacting with a small monochromatic electromagnetic wave are studied in the presence of an inhomogeneous background magnetic field. A resonance-averaged Hamiltonian is derived which retains the effects of passage through resonance. Two distinct regimes are found. In the strongly inhomogeneous case, the resonant phase angle at successive resonances is random, and multiple resonant interactions lead to a random walk in phase space. In the other, adiabatic limit, the phase angle is determined by the phase portrait of the Hamiltonian and leads to a systematic change in the appropriate canonical action (and therefore in the energy and pitch angle), so that the cumulative effect increases directly with the number of resonances.

  14. Magnetic material arrangement in oriented termites: a magnetic resonance study

    NASA Astrophysics Data System (ADS)

    Alves, O. C.; Wajnberg, E.; de Oliveira, J. F.; Esquivel, D. M. S.

    2004-06-01

    Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite, the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g=2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite's body (abdomen + thorax). From the temperature dependence of the resonant field and from the spectral linewidths, we estimate the existence of magnetic nanoparticles 18.5 ± 0.3 nm in diameter and an effective magnetic anisotropy constant, Keff between 2.1 and 3.2 × 10 4 erg/cm 3. A sudden change in the double integrated spectra at about 100 K for N.o. with the long body axis oriented perpendicular to the magnetic field can be attributed to the Verwey transition, and suggests an organized film-like particle system.

  15. Magnetic resonance imaging by using nano-magnetic particles

    NASA Astrophysics Data System (ADS)

    Shokrollahi, H.; Khorramdin, A.; Isapour, Gh.

    2014-11-01

    Magnetism and magnetic materials play a major role in various biological applications, such as magnetic bioseparation, magnetic resonance imaging (MRI), hyperthermia treatment of cancer and drug delivery. Among these techniques, MRI is a powerful method not only for diagnostic radiology but also for therapeutic medicine that utilizes a magnetic field and radio waves. Recently, this technique has contributed greatly to the promotion of the human quality life. Thus, this paper presents a short review of the physical principles and recent advances of MRI, as well as providing a summary of the synthesis methods and properties of contrast agents, like different core materials and surfactants.

  16. Magnetic plasmonic Fano resonance at optical frequency.

    PubMed

    Bao, Yanjun; Hu, Zhijian; Li, Ziwei; Zhu, Xing; Fang, Zheyu

    2015-05-13

    Plasmonic Fano resonances are typically understood and investigated assuming electrical mode hybridization. Here we demonstrate that a purely magnetic plasmon Fano resonance can be realized at optical frequency with Au split ring hexamer nanostructure excited by an azimuthally polarized incident light. Collective magnetic plasmon modes induced by the circular electric field within the hexamer and each of the split ring can be controlled and effectively hybridized by designing the size and orientation of each ring unit. With simulated results reproducing the experiment, our suggested configuration with narrow line-shape magnetic Fano resonance has significant potential applications in low-loss sensing and may serves as suitable elementary building blocks for optical metamaterials. PMID:25594885

  17. Magnetic resonance imaging of the body

    SciTech Connect

    Higgins, C.B.; Hricak, H.

    1987-01-01

    This text provides reference to magnetic resonance imaging (MRI) of the body. Beginning with explanatory chapters on the physics, instrumentation, and interpretation of MRI, it proceeds to the normal anatomy of the neck, thorax, abdomen, and pelvis. Other chapters cover magnetic resonance imaging of blood flow, the larynx, the lymph nodes, and the spine, as well as MRI in obstetrics. The text features detailed coverage of magnetic resonance imaging of numerous disorders and disease states, including neck disease, thoracic disease; breast disease; congenital and acquired heart disease; vascular disease; diseases of the liver, pancreas, and spleen; diseases of the kidney, adrenals, and retroperitoneum; diseases of the male and female pelvis; and musculoskeletal diseases. Chapters on the biological and environmental hazards of MRI, the current clinical status of MRI in comparison to other imaging modalities, and economic considerations are also included.

  18. The Diversity of Nuclear Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Corey W.; Alekseyev, Viktor Y.; Allwardt, Jeffrey R.; Bankovich, Alexander J.; Cade-Menun, Barbara J.; Davis, Ronald W.; Du, Lin-Shu; Garcia, K. Christopher; Herschlag, Daniel; Khosla, Chaitan; Kraut, Daniel A.; Li, Qing; Null, Brian; Puglisi, Joseph D.; Sigala, Paul A.; Stebbins, Jonathan F.; Varani, Luca

    The discovery of the physical phenomenon of Nuclear Magnetic Resonance (NMR) in 1946 gave rise to the spectroscopic technique that has become a remarkably versatile research tool. One could oversimplify NMR spectros-copy by categorizing it into the two broad applications of structure elucidation of molecules (associated with chemistry and biology) and imaging (associated with medicine). But, this certainly does not do NMR spectroscopy justice in demonstrating its general acceptance and utilization across the sciences. This manuscript is not an effort to present an exhaustive, or even partial review of NMR spectroscopy applications, but rather to provide a glimpse at the wide-ranging uses of NMR spectroscopy found within the confines of a single magnetic resonance research facility, the Stanford Magnetic Resonance Laboratory. Included here are summaries of projects involving protein structure determination, mapping of intermolecular interactions, exploring fundamental biological mechanisms, following compound cycling in the environmental, analysis of synthetic solid compounds, and microimaging of a model organism.

  19. Tutte polynomial in functional magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    García-Castillón, Marlly V.

    2015-09-01

    Methods of graph theory are applied to the processing of functional magnetic resonance images. Specifically the Tutte polynomial is used to analyze such kind of images. Functional Magnetic Resonance Imaging provide us connectivity networks in the brain which are represented by graphs and the Tutte polynomial will be applied. The problem of computing the Tutte polynomial for a given graph is #P-hard even for planar graphs. For a practical application the maple packages "GraphTheory" and "SpecialGraphs" will be used. We will consider certain diagram which is depicting functional connectivity, specifically between frontal and posterior areas, in autism during an inferential text comprehension task. The Tutte polynomial for the resulting neural networks will be computed and some numerical invariants for such network will be obtained. Our results show that the Tutte polynomial is a powerful tool to analyze and characterize the networks obtained from functional magnetic resonance imaging.

  20. Magnetic resonance of magnetic fluid and magnetoliposome preparations

    NASA Astrophysics Data System (ADS)

    Morais, Paulo C.; Santos, Judes G.; Skeff Neto, K.; Pelegrini, Fernando; De Cuyper, Marcel

    2005-05-01

    In this study, magnetic resonance was used to investigate lauric acid-coated magnetite-based magnetic fluid particles and particles which are surrounded by a double layer of phospholipid molecules (magnetoliposomes). The data reveal the presence of monomers and dimers in both samples. Whereas evidence for a thermally induced disruption of dimers is found in the magnetic fluid, apparently, the bilayer phospholipid envelop prevents the dissociation in the magnetoliposome samples.

  1. Magnetic resonance signal moment determination using the Earth's magnetic field.

    PubMed

    Fridjonsson, E O; Creber, S A; Vrouwenvelder, J S; Johns, M L

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system. PMID:25700116

  2. Magnetic resonance signal moment determination using the Earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Fridjonsson, E. O.; Creber, S. A.; Vrouwenvelder, J. S.; Johns, M. L.

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system.

  3. Nanomagnetic planar magnetic resonance microscopy "lens".

    PubMed

    Barbic, Mladen; Scherer, Axel

    2005-04-01

    The achievement of three-dimensional atomic resolution magnetic resonance microscopy remains one of the main challenges in the visualization of biological molecules. The prospects for single spin microscopy have come tantalizingly close due to the recent developments in sensitive instrumentation. Despite the single spin detection capability in systems of spatially well-isolated spins, the challenge that remains is the creation of conditions in space where only a single spin is resonant and detected in the presence of other spins in its natural dense spin environment. We present a nanomagnetic planar design where a localized Angstrom-scale point in three-dimensional space is created above the nanostructure with a nonzero minimum of the magnetic field magnitude. The design thereby represents a magnetic resonance microscopy "lens" where potentially only a single spin located in the "focus" spot of the structure is resonant. Despite the presence of other spins in the Angstrom-scale vicinity of the resonant spin, the high gradient magnetic field of the "lens" renders those spins inactive in the detection process. PMID:15826129

  4. Magnetic resonance neurography of the brachial plexus

    PubMed Central

    Upadhyaya, Vaishali; Upadhyaya, Divya Narain; Kumar, Adarsh; Pandey, Ashok Kumar; Gujral, Ratni; Singh, Arun Kumar

    2015-01-01

    Magnetic Resonance Imaging (MRI) is being increasingly recognised all over the world as the imaging modality of choice for brachial plexus and peripheral nerve lesions. Recent refinements in MRI protocols have helped in imaging nerve tissue with greater clarity thereby helping in the identification, localisation and classification of nerve lesions with greater confidence than was possible till now. This article on Magnetic Resonance Neurography (MRN) is based on the authors’ experience of imaging the brachial plexus and peripheral nerves using these protocols over the last several years. PMID:26424974

  5. Granular convection observed by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ehrichs, E. E.; Jaeger, H. M.; Karczmar, Greg S.; Knight, James B.; Kuperman, Vadim Yu.; Nagel, Sidney R.

    1995-03-01

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.

  6. Granular convection observed by magnetic resonance imaging

    SciTech Connect

    Ehrichs, E.E.; Jaeger, H.M.; Knight, J.B.; Nagel, S.R.; Karczmar, G.S.; Kuperman, V.Yu.

    1995-03-17

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here. 31 refs., 4 figs.

  7. Artifacts in Breast Magnetic Resonance Imaging.

    PubMed

    Anthony, Marina-Portia; Nguyen, Dustin; Friedlander, Lauren; Mango, Victoria; Wynn, Ralph; Ha, Richard

    2016-01-01

    As breast magnetic resonance imaging has evolved to become a routine part of clinical practice, so too has the need for radiologists to be aware of its potential pitfalls and limitations. Unique challenges arise in the identification and remedy of artifacts in breast magnetic resonance imaging, and it is important that radiologists and technicians work together to optimize protocols and monitor examinations such that these may be minimized or avoided entirely. This article presents patient-related and technical artifacts that may give rise to reduced image quality and ways to recognize and reduce them. PMID:26343534

  8. Magnetic force microscopy using tip magnetization modulated by ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Arima, Eiji; Naitoh, Yoshitaka; Li, Yan Jun; Yoshimura, Satoru; Saito, Hitoshi; Nomura, Hikaru; Nakatani, Ryoichi; Sugawara, Yasuhiro

    2015-03-01

    In magnetic force microscopy (MFM), the tip-sample distance should be reduced to analyze the microscopic magnetic domain structure with high spatial resolution. However, achieving a small tip-sample distance has been difficult because of superimposition of interaction forces such as van der Waals and electrostatic forces induced by the sample surface. In this study, we propose a new method of MFM using ferromagnetic resonance (FMR) to extract only the magnetic field near the sample surface. In this method, the magnetization of a magnetic cantilever is modulated by FMR to separate the magnetic field and topographic structure. We demonstrate the modulation of the magnetization of the cantilever and the identification of the polarities of a perpendicular magnetic medium.

  9. Magnetic force microscopy using tip magnetization modulated by ferromagnetic resonance.

    PubMed

    Arima, Eiji; Naitoh, Yoshitaka; Li, Yan Jun; Yoshimura, Satoru; Saito, Hitoshi; Nomura, Hikaru; Nakatani, Ryoichi; Sugawara, Yasuhiro

    2015-03-27

    In magnetic force microscopy (MFM), the tip-sample distance should be reduced to analyze the microscopic magnetic domain structure with high spatial resolution. However, achieving a small tip-sample distance has been difficult because of superimposition of interaction forces such as van der Waals and electrostatic forces induced by the sample surface. In this study, we propose a new method of MFM using ferromagnetic resonance (FMR) to extract only the magnetic field near the sample surface. In this method, the magnetization of a magnetic cantilever is modulated by FMR to separate the magnetic field and topographic structure. We demonstrate the modulation of the magnetization of the cantilever and the identification of the polarities of a perpendicular magnetic medium. PMID:25736463

  10. Magnetic elliptical polarization of Schumann resonances

    SciTech Connect

    Sentman, D.D.

    1987-08-01

    Measurements of orthogonal, horizontal components of the magnetic field in the ELF range obtained during September 1985 show that the Schumann resonance eigenfrequencies determined separately for the north-south and east-west magnetic components differ by as much as 0.5 Hz, suggesting that the underlying magnetic signal is not linearly polarized at such times. The high degree of magnetic ellipticity found suggests that the side multiplets of the Schumann resonances corresponding to azimuthally inhomogeneous normal modes are strongly excited in the highly asymmetric earth-ionosphere cavity. The dominant sense of polarization over the measurement passband is found to be right-handed during local daylight hours, and to be left-handed during local nighttime hours. 16 references.

  11. Magnetic elliptical polarization of Schumann resonances

    NASA Technical Reports Server (NTRS)

    Sentman, D. D.

    1987-01-01

    Measurements of orthogonal, horizontal components of the magnetic field in the ELF range obtained during September 1985 show that the Schumann resonance eigenfrequencies determined separately for the north-south and east-west magnetic components differ by as much as 0.5 Hz, suggesting that the underlying magnetic signal is not linearly polarized at such times. The high degree of magnetic ellipticity found suggests that the side multiplets of the Schumann resonances corresponding to azimuthally inhomogeneous normal modes are strongly excited in the highly asymmetric earth-ionosphere cavity. The dominant sense of polarization over the measurement passband is found to be right-handed during local daylight hours, and to be left-handed during local nighttime hours.

  12. Magnetic Resonance Imaging by Synergistic Diffusion-Diffraction Patterns

    NASA Astrophysics Data System (ADS)

    Shemesh, Noam; Westin, Carl-Fredrik; Cohen, Yoram

    2012-02-01

    Inferring on the geometry of an object from its frequency spectrum is highly appealing since the object could then be imaged noninvasively or from a distance (as famously put by Kac, “can one hear the shape of a drum?”). In nuclear magnetic resonance of porous systems, the shape of the drum is represented by the pore density function that bears all the information on the collective pore microstructure. So far, conventional magnetic resonance imaging (MRI) could only detect the pore autocorrelation function, which inherently obscures fine details on the pore structure. Here, for the first time, we report on a unique imaging mechanism arising from synergistic diffusion-diffractions that directly yields the pore density function. This mechanism offers substantially higher spatial resolution compared to conventional MRI while retaining all fine details on the collective pore morphology. Thus, using these unique synergistic diffusion-diffractions, the “shape of the drum” can be inferred.

  13. Enhancement of artificial magnetism via resonant bianisotropy

    PubMed Central

    Markovich, Dmitry; Baryshnikova, Kseniia; Shalin, Alexander; Samusev, Anton; Krasnok, Alexander; Belov, Pavel; Ginzburg, Pavel

    2016-01-01

    All-dielectric “magnetic light” nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses. PMID:26941126

  14. Magnetic fields and density functional theory

    SciTech Connect

    Salsbury Jr., Freddie

    1999-02-01

    A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.

  15. Brain Morphometry Using Anatomical Magnetic Resonance Imaging

    ERIC Educational Resources Information Center

    Bansal, Ravi; Gerber, Andrew J.; Peterson, Bradley S.

    2008-01-01

    The efficacy of anatomical magnetic resonance imaging (MRI) in studying the morphological features of various regions of the brain is described, also providing the steps used in the processing and studying of the images. The ability to correlate these features with several clinical and psychological measures can help in using anatomical MRI to…

  16. Sports Health Magnetic Resonance Imaging Challenge

    PubMed Central

    Howell, Gary A.; Stadnick, Michael E.; Awh, Mark H.

    2010-01-01

    Injuries to the Lisfranc ligament complex are often suspected, particularly in the setting of midfoot pain without radiographic abnormality. Knowledge of the anatomy and magnetic resonance imaging findings of injuries to this region is helpful for the diagnosing and treating physicians. PMID:23015984

  17. An improved nuclear magnetic resonance spectrometer

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.; Manatt, S. L.

    1967-01-01

    Cylindrical sample container provides a high degree of nuclear stabilization to a nuclear magnetic resonance /nmr/ spectrometer. It is placed coaxially about the nmr insert and contains reference sample that gives a signal suitable for locking the field and frequency of an nmr spectrometer with a simple audio modulation system.

  18. Nuclear Magnetic Resonance Technology for Medical Studies.

    ERIC Educational Resources Information Center

    Budinger, Thomas F.; Lauterbur, Paul C.

    1984-01-01

    Reports on the status of nuclear magnetic resonance (NMR) from theoretical and clinical perspectives, reviewing NMR theory and relaxation parameters relevant to NMR imaging. Also reviews literature related to modern imaging strategies, signal-to-noise ratio, contrast agents, in vivo spectroscopy, spectroscopic imaging, clinical applications, and…

  19. Imaging Intelligence with Proton Magnetic Resonance Spectroscopy

    ERIC Educational Resources Information Center

    Jung, Rex E.; Gasparovic, Charles; Chavez, Robert S.; Caprihan, Arvind; Barrow, Ranee; Yeo, Ronald A.

    2009-01-01

    Proton magnetic resonance spectroscopy ([to the first power]H-MRS) is a technique for the assay of brain neurochemistry "in vivo." N-acetylaspartate (NAA), the most prominent metabolite visible within the [to the first power]H-MRS spectrum, is found primarily within neurons. The current study was designed to further elucidate NAA-cognition…

  20. Use of Magnetic Resonance in Pancreaticobiliary Emergencies.

    PubMed

    Bates, David D B; LeBedis, Christina A; Soto, Jorge A; Gupta, Avneesh

    2016-05-01

    This article presents the magnetic resonance protocols, imaging features, diagnostic criteria, and complications of commonly encountered emergencies in pancreaticobiliary imaging. Pancreatic trauma, bile leak, acute cholecystitis, biliary obstruction, and pancreatitis are discussed. Various classifications and complications that can arise with these conditions, as well as artifacts that may mimic pathology, are also included. PMID:27150328

  1. Magnetic resonance investigation of magnetic-labeled baker's yeast cells

    NASA Astrophysics Data System (ADS)

    Godoy Morais, J. P. M.; Azevedo, R. B.; Silva, L. P.; Lacava, Z. G. M.; Báo, S. N.; Silva, O.; Pelegrini, F.; Gansau, C.; Buske, N.; Safarik, I.; Safarikova, M.; Morais, P. C.

    2004-05-01

    In this study, the interaction of DMSA-coated magnetite nanoparticles (5 and 10 nm core-size) with Saccharomyces cerevisae was investigated using magnetic resonance (MR) and transmission electron microscopy (TEM). The TEM micrographs revealed magnetite nanoparticles attached externally to the cell wall. The MR data support the strong interaction among the nanoparticles supported by the cells. A remarkable shift in the resonance field was used as signature of particle attachment to the cell wall.

  2. Probing the Oxygen Environment in UO22+ by Solid-State O-17 Nuclear Magnetic Resonance Spectroscopy and Relativistic Density Functional Calculations

    SciTech Connect

    Cho, Herman M.; De Jong, Wibe A.; Soderquist, Chuck Z.

    2010-02-28

    A combined theoretical and solid-state O-17 NMR study of the electronic structure of the uranyl ion UO22+ in (NH4)4UO2(CO3)3 and rutherfordine UO2CO3 is presented, the former representing a system with a hydrogen-bonding environment around the uranyl oxygens, and the latter exemplifying a uranyl environment without hydrogens. A fully relativistic ab initio treatment reveals unique features of the U-O covalent bond, including the finding of O-17 chemical shift anisotropies that are among the largest ever reported (>1200 ppm). Computational results for the oxygen electric field gradient tensor are found to be consistently larger in magnitude than experimental solid-state O-17 NMR measurements in a 7.05 T magnetic field indicate. A modified version of the Solomon theory of the two-spin echo amplitude for a spin-5/2 nucleus is developed and applied to the analysis of the O-17 echo signal of UO22+. The William R. Wiley environmental Molecular Sciences Laboratory is a US Department of Energy national scientific user facility located at Pacific Northwest National Laboratory (PNNL) in Richland, Washington. PNNL is operated by Battelle for the US Department of Energy.

  3. Nuclear magnetic resonance properties of lunar samples.

    NASA Technical Reports Server (NTRS)

    Kline, D.; Weeks, R. A.

    1972-01-01

    Nuclear magnetic resonance spectra of Na-23, Al-27, and P-31 in fines samples 10084,60 and 14163,168 and in crystalline rock samples 12021,55 and 14321,166, have been recorded over a range of frequencies up to 20 MHz. A shift in the field at which maximum absorption occurs for all of the spectra relative to the field at which maximum absorption occurs for terrestrial analogues is attributed to a sample-dependent magnetic field at the Na, Al, and P sites opposing the laboratory field. The magnitude of these fields internal to the samples is sample dependent and varies from 5 to 10 G. These fields do not correlate with the iron content of the samples. However, the presence of single-domain particles of iron distributed throughout the plagioclase fraction that contains the principal fraction of Na and Al is inferred from electron magnetic resonance spectra shapes.

  4. Magnetic Earth Ionosphere Resonant Frequencies

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1994-01-01

    The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.

  5. Volume coil based on hybridized resonators for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Jouvaud, C.; Abdeddaim, R.; Larrat, B.; de Rosny, J.

    2016-01-01

    We present an electromagnetic device based on hybridization of four half-wavelength dipoles which increases the uniformity and the strength of the radio-frequency (RF) field of a Magnetic Resonant Imaging (MRI) apparatus. Numerical results show that this Hybridized Coil (HC) excited with a classical loop coil takes advantage of the magnetic hybrid modes. The distribution of the RF magnetic field is experimentally confirmed on a 7-T MRI with a gelatin phantom. Finally, the HC is validated in vivo by imaging the head of an anesthetized rat. We measure an overall increase of the signal to noise ratio with up to 2.4 fold increase in regions of interest far from the active loop coil.

  6. A hybrid, inverse approach to the design of magnetic resonance imaging magnets.

    PubMed

    Zhao, H; Crozier, S; Doddrell, D M

    2000-03-01

    This paper describes a hybrid numerical method of an inverse approach to the design of compact magnetic resonance imaging magnets. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to the desired current density. The field calculations are performed using a semi-analytical method. The emphasis of this work is on the optimal design of short MRI magnets. Details of the hybrid numerical model are presented, and the model is used to investigate compact, symmetric MRI magnets as well as asymmetric magnets. The results highlight that the method can be used to obtain a compact MRI magnet structure and a very homogeneous magnetic field over the central imaging volume in clinical systems of approximately 1 m in length, significantly shorter than current designs. Viable asymmetric magnet designs, in which the edge of the homogeneous region is very close to one end of the magnet system are also presented. Unshielded designs are the focus of this work. This method is flexible and may be applied to magnets of other geometries. PMID:10757611

  7. A hyperpolarized equilibrium for magnetic resonance

    NASA Astrophysics Data System (ADS)

    Hövener, Jan-Bernd; Schwaderlapp, Niels; Lickert, Thomas; Duckett, Simon B.; Mewis, Ryan E.; Highton, Louise A. R.; Kenny, Stephen M.; Green, Gary G. R.; Leibfritz, Dieter; Korvink, Jan G.; Hennig, Jürgen; von Elverfeldt, Dominik

    2013-12-01

    Nuclear magnetic resonance spectroscopy and imaging (MRI) play an indispensable role in science and healthcare but use only a tiny fraction of their potential. No more than ≈10 p.p.m. of all 1H nuclei are effectively detected in a 3-Tesla clinical MRI system. Thus, a vast array of new applications lays dormant, awaiting improved sensitivity. Here we demonstrate the continuous polarization of small molecules in solution to a level that cannot be achieved in a viable magnet. The magnetization does not decay and is effectively reinitialized within seconds after being measured. This effect depends on the long-lived, entangled spin-order of parahydrogen and an exchange reaction in a low magnetic field of 10-3 Tesla. We demonstrate the potential of this method by fast MRI and envision the catalysis of new applications such as cancer screening or indeed low-field MRI for routine use and remote application.

  8. A hyperpolarized equilibrium for magnetic resonance.

    PubMed

    Hövener, Jan-Bernd; Schwaderlapp, Niels; Lickert, Thomas; Duckett, Simon B; Mewis, Ryan E; Highton, Louise A R; Kenny, Stephen M; Green, Gary G R; Leibfritz, Dieter; Korvink, Jan G; Hennig, Jürgen; von Elverfeldt, Dominik

    2013-01-01

    Nuclear magnetic resonance spectroscopy and imaging (MRI) play an indispensable role in science and healthcare but use only a tiny fraction of their potential. No more than ≈10 p.p.m. of all ¹H nuclei are effectively detected in a 3-Tesla clinical MRI system. Thus, a vast array of new applications lays dormant, awaiting improved sensitivity. Here we demonstrate the continuous polarization of small molecules in solution to a level that cannot be achieved in a viable magnet. The magnetization does not decay and is effectively reinitialized within seconds after being measured. This effect depends on the long-lived, entangled spin-order of parahydrogen and an exchange reaction in a low magnetic field of 10⁻³ Tesla. We demonstrate the potential of this method by fast MRI and envision the catalysis of new applications such as cancer screening or indeed low-field MRI for routine use and remote application. PMID:24336292

  9. A hyperpolarized equilibrium for magnetic resonance

    PubMed Central

    Hövener, Jan-Bernd; Schwaderlapp, Niels; Lickert, Thomas; Duckett, Simon B.; Mewis, Ryan E.; Highton, Louise A. R.; Kenny, Stephen M.; Green, Gary G. R.; Leibfritz, Dieter; Korvink, Jan G.; Hennig, Jürgen; von Elverfeldt, Dominik

    2013-01-01

    Nuclear magnetic resonance spectroscopy and imaging (MRI) play an indispensable role in science and healthcare but use only a tiny fraction of their potential. No more than ≈10 p.p.m. of all 1H nuclei are effectively detected in a 3-Tesla clinical MRI system. Thus, a vast array of new applications lays dormant, awaiting improved sensitivity. Here we demonstrate the continuous polarization of small molecules in solution to a level that cannot be achieved in a viable magnet. The magnetization does not decay and is effectively reinitialized within seconds after being measured. This effect depends on the long-lived, entangled spin-order of parahydrogen and an exchange reaction in a low magnetic field of 10−3 Tesla. We demonstrate the potential of this method by fast MRI and envision the catalysis of new applications such as cancer screening or indeed low-field MRI for routine use and remote application. PMID:24336292

  10. Resonant Absorption of Axisymmetric Modes in Twisted Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Giagkiozis, I.; Goossens, M.; Verth, G.; Fedun, V.; Van Doorsselaere, T.

    2016-06-01

    It has been shown recently that magnetic twist and axisymmetric MHD modes are ubiquitous in the solar atmosphere, and therefore the study of resonant absorption for these modes has become a pressing issue because it can have important consequences for heating magnetic flux tubes in the solar atmosphere and the observed damping. In this investigation, for the first time, we calculate the damping rate for axisymmetric MHD waves in weakly twisted magnetic flux tubes. Our aim is to investigate the impact of resonant damping of these modes for solar atmospheric conditions. This analytical study is based on an idealized configuration of a straight magnetic flux tube with a weak magnetic twist inside as well as outside the tube. By implementing the conservation laws derived by Sakurai et al. and the analytic solutions for weakly twisted flux tubes obtained recently by Giagkiozis et al. we derive a dispersion relation for resonantly damped axisymmetric modes in the spectrum of the Alfvén continuum. We also obtain an insightful analytical expression for the damping rate in the long wavelength limit. Furthermore, it is shown that both the longitudinal magnetic field and the density, which are allowed to vary continuously in the inhomogeneous layer, have a significant impact on the damping time. Given the conditions in the solar atmosphere, resonantly damped axisymmetric modes are highly likely to be ubiquitous and play an important role in energy dissipation. We also suggest that, given the character of these waves, it is likely that they have already been observed in the guise of Alfvén waves.

  11. Foundations of Advanced Magnetic Resonance Imaging

    PubMed Central

    Bammer, Roland; Skare, Stefan; Newbould, Rexford; Liu, Chunlei; Thijs, Vincent; Ropele, Stefan; Clayton, David B.; Krueger, Gunnar; Moseley, Michael E.; Glover, Gary H.

    2005-01-01

    Summary: During the past decade, major breakthroughs in magnetic resonance imaging (MRI) quality were made by means of quantum leaps in scanner hardware and pulse sequences. Some advanced MRI techniques have truly revolutionized the detection of disease states and MRI can now—within a few minutes—acquire important quantitative information noninvasively from an individual in any plane or volume at comparatively high resolution. This article provides an overview of the most common advanced MRI methods including diffusion MRI, perfusion MRI, functional MRI, and the strengths and weaknesses of MRI at high magnetic field strengths. PMID:15897944

  12. Magnetic resonances in nano-scale metamaterials

    NASA Astrophysics Data System (ADS)

    Hao, Zhao; Liddle, Alex; Martin, Michael

    2006-03-01

    We have designed, fabricated, and optically measured several different kinds of nano-scale metamaterials. We make use e-beam nano-lithography technology at LBNL's Center for X-Ray Optics for fabricating these structures on extremely thin SiN substrates so that they are close to free-standing. Optical properties were measured as a function of incidence angle and polarization. We directly observe a strong magnetic resonance consistent with a negative magnetic permeability in our samples at mid- and near-IR optical frequencies. We will discuss the results in comparison with detailed simulations, and will discuss the electric dipole or quadrupole resonances observed in the samples. Finally, we will report on our progress towards constructing a fully negative index of refraction meta-material.

  13. Proton magnetic resonance spectroscopy in multiple sclerosis

    SciTech Connect

    Wolinsky, J.S.; Narayana, P.A.; Fenstermacher, M.J. )

    1990-11-01

    Regional in vivo proton magnetic resonance spectroscopy provides quantitative data on selected chemical constituents of brain. We imaged 16 volunteers with clinically definite multiple sclerosis on a 1.5 tesla magnetic resonance scanner to define plaque-containing volumes of interest, and obtained localized water-suppressed proton spectra using a stimulated echo sequence. Twenty-five of 40 plaque-containing regions provided spectra of adequate quality. Of these, 8 spectra from 6 subjects were consistent with the presence of cholesterol or fatty acids; the remainder were similar to those obtained from white matter of normal volunteers. This early experience with regional proton spectroscopy suggests that individual plaques are distinct. These differences likely reflect dynamic stages of the evolution of the demyelinative process not previously accessible to in vivo investigation.

  14. Magnetic Resonance Characterization of Ischemic Tissue Metabolism

    PubMed Central

    Cheung, Jerry S; Wang, Xiaoying; Zhe Sun, Phillip

    2011-01-01

    Magnetic resonance imaging (MRI) and spectroscopy (MRS) are versatile diagnostic techniques capable of characterizing the complex stroke pathophysiology, and hold great promise for guiding stroke treatment. Particularly, tissue viability and salvageability are closely associated with its metabolic status. Upon ischemia, ischemic tissue metabolism is disrupted including altered metabolism of glucose and oxygen, elevated lactate production/accumulation, tissue acidification and eventually, adenosine triphosphate (ATP) depletion and energy failure. Whereas metabolism impairment during ischemic stroke is complex, it may be monitored non-invasively with magnetic resonance (MR)-based techniques. Our current article provides a concise overview of stroke pathology, conventional and emerging imaging and spectroscopy techniques, and data analysis tools for characterizing ischemic tissue damage. PMID:22216079

  15. Magnetic resonance angiography: physical principles and applications.

    PubMed

    Kiruluta, Andrew J M; González, R Gilberto

    2016-01-01

    Magnetic resonance angiography (MRA) is the visualization of hemodynamic flow using imaging techniques that discriminate flowing spins in blood from those in stationary tissue. There are two classes of MRA methods based on whether the magnetic resonance imaging signal in flowing blood is derived from the amplitude of the moving spins, the time-of-flight methods, or is based on the phase accumulated by these flowing spins, as in phase contrast methods. Each method has particular advantages and limitations as an angiographic imaging technique, as evidenced in their application space. Here we discuss the physics of MRA for both classes of imaging techniques, including contrast-enhanced approaches and the recent rapid expansion of the techniques to fast acquisition and processing techniques using parallel imaging coils as well as their application in high-field MR systems such as 3T and 7T. PMID:27432663

  16. Combined Confocal and Magnetic Resonance Microscopy

    SciTech Connect

    Wind, Robert A.; Majors, Paul D.; Minard, Kevin R.; Ackerman, Eric J.; Daly, Don S.; Holtom, Gary R.; Thrall, Brian D.; Weber, Thomas J.

    2002-05-12

    Confocal and magnetic resonance microscopy are both used to study live cells in a minimally invasive way. Both techniques provide complementary information. Therefore, by examining cells simultaneously with both methodologies, more detailed information is obtained than is possible with each of the microscopes individually. In this paper two configurations of a combined confocal and magnetic resonance microscope described. In both cases the sample compartment is part of a temperature regulated perfusion system. The first configuration is capable of studying large single cells or three-dimensional cell agglomerates, whereas with the second configuration monolayers of mammalian cells can be investigated . Combined images are shown of Xenopus laevis frog oocytes, model JB6 tumor spheroids, and a single layer of Chinese hamster ovary cells. Finally, potential applications of the combined microscope are discussed.

  17. [Indications for magnetic resonance imaging in pneumology].

    PubMed

    Arrivé, L

    1997-04-19

    Tissue mobilization caused by respiration and heart beat and lower spacial resolution than with computed tomography has limited use of magnetic resonance imaging (MRI) in pneumology. Nevertheless, because of the high-quality of spontaneous contrast and the non irradiation nature of the examination, there are selected indications. For bronchogenic cancer, MRI is reserved for selected cases to evaluate tumor extension. For tumors of the mediastinum, MRI is particularly useful for evaluating extension of neurogenic tumors. MRI also gives a better visualization of processes involving the diaphragm than computed tomography. The development of magnetic resonance angiography is a major progress for exploration of pulmonary embolism as repeated acquisitions can be obtained without injection of a contrast medium. Several studies have shown that MRI visualizes well solitary lung nodules, clearly distinguishing fat content from vascularized nodules. For the pulmonary parenchyma, further advances are necessary before MRI can become a routine exploration technique. PMID:9180867

  18. Thermal field fluctuations in a magnetic tip / implications for magnetic resonance force microscopy

    NASA Astrophysics Data System (ADS)

    Hannay, J. D.; Chantrell, R. W.; Rugar, D.

    2000-05-01

    Thermally excited magnetic fluctuations are fundamental to the behavior of small ferromagnetic particles and have practical consequences for the proposed detection of individual spins by magnetic resonance force microscopy (MRFM). In particular, fluctuating fields from a nearby magnetic tip can increase the relaxation rate of spins in a sample if there is significant spectral density of field fluctuation at the Larmor frequency of the target spin. As an initial step toward understanding this issue, magnetic field fluctuations have been simulated which emanate from a magnetic tip with dimensions 60 nm×60 nm×2 μm. It was found that the fluctuations in a cobalt magnetic tip were too strong for MRFM experiments aimed at detecting individual electron spins. However, the results obtained for a PrFeB tip fell within the tolerance required.

  19. Antiferromagnetic resonance excitation by terahertz magnetic field resonantly enhanced with split ring resonator

    SciTech Connect

    Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

    2014-07-14

    Excitation of antiferromagnetic resonance (AFMR) in a HoFeO{sub 3} crystal combined with a split ring resonator (SRR) is studied using terahertz (THz) electromagnetic pulses. The magnetic field in the vicinity of the SRR is induced by the incident THz electric field component and excites spin oscillations that correspond to the AFMR, which are directly probed by the Faraday rotation of the polarization of a near-infrared probe pulse. The good agreement of the temperature-dependent magnetization dynamics with the calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms that the AFMR is excited by the THz magnetic field, which is enhanced at the SRR resonance frequency by a factor of 20 compared to the incident magnetic field.

  20. Fundamental physics of magnetic resonance imaging.

    PubMed

    Villafana, T

    1988-07-01

    Although similar to computerized tomography, in that cross-sectional images are produced, the physical principles underlying magnetic resonance are entirely different. The MRI process, as commonly implemented, involves the excitation of hydrogen nuclei and the analysis of how these nuclei recover to the original equilibrium steady states that they had prior to excitation. This article discusses that process, that is, preparatory alignment, RF excitation, relaxation and signal measurement, and spatial localization. PMID:3380941

  1. Nuclear magnetic resonance in Kondo lattice systems

    NASA Astrophysics Data System (ADS)

    Curro, Nicholas J.

    2016-06-01

    Nuclear magnetic resonance has emerged as a vital tool to explore the fundamental physics of Kondo lattice systems. Because nuclear spins experience two different hyperfine couplings to the itinerant conduction electrons and to the local f moments, the Knight shift can probe multiple types of spin correlations that are not accessible via other techniques. The Knight shift provides direct information about the onset of heavy electron coherence and the emergence of the heavy electron fluid.

  2. Neurosurgical uses for intraprocedural magnetic resonance imaging.

    PubMed

    Mutchnick, Ian S; Moriarty, Thomas M

    2005-10-01

    Neurosurgical procedures demand precision, and efforts to create accurate neurosurgical navigation have been central to the profession through its history. Magnetic resonance image (MRI)-guided navigation offers the possibility of real-time, image-based stereotactic information for the neurosurgeon, which makes possible a number of diagnostic and therapeutic procedures. This article will review both current options for intraoperative MRI operative suite arrangements and the current therapeutic/diagnostic uses of intraoperative MRI. PMID:16924171

  3. Magnetic resonance imaging: Principles and applications

    SciTech Connect

    Kean, D.; Smith, M.

    1986-01-01

    This text covers the physics underlying magnetic resonance (MR) imaging; pulse sequences; image production; equipment; aspects of clinical imaging; and the imaging of the head and neck, thorax, abdomen and pelvis, and musculoskeletal system; and MR imaging. The book provides about 150 examples of MR images that give an overview of the pathologic conditions imaged. There is a discussion of the physics of MR imaging and also on the spin echo.

  4. Magnetic resonance imaging of diabetic foot complications

    PubMed Central

    Low, Keynes TA; Peh, Wilfred CG

    2015-01-01

    This pictorial review aims to illustrate the various manifestations of the diabetic foot on magnetic resonance (MR) imaging. The utility of MR imaging and its imaging features in the diagnosis of pedal osteomyelitis are illustrated. There is often difficulty encountered in distinguishing osteomyelitis from neuroarthropathy, both clinically and on imaging. By providing an accurate diagnosis based on imaging, the radiologist plays a significant role in the management of patients with complications of diabetic foot. PMID:25640096

  5. Magnetic resonance imaging of diabetic foot complications.

    PubMed

    Low, Keynes T A; Peh, Wilfred C G

    2015-01-01

    This pictorial review aims to illustrate the various manifestations of the diabetic foot on magnetic resonance (MR) imaging. The utility of MR imaging and its imaging features in the diagnosis of pedal osteomyelitis are illustrated. There is often difficulty encountered in distinguishing osteomyelitis from neuroarthropathy, both clinically and on imaging. By providing an accurate diagnosis based on imaging, the radiologist plays a significant role in the management of patients with complications of diabetic foot. PMID:25640096

  6. Fluctuating magnetic field induced resonant activation

    SciTech Connect

    Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

    2014-12-14

    In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (τ) increases under the fixed field strength then the mean first passage time rapidly grows at low τ and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers’ turn over phenomenon may occur in the presence of a fluctuating magnetic field.

  7. Asymmetric zonal shim coils for magnetic resonance applications.

    PubMed

    Forbes, L K; Crozier, S

    2001-08-01

    A method is presented for the systematic design of asymmetric zonal shim coils for magnetic resonance applications. Fourier-series methods are used to represent the magnetic field inside and outside a circular cylinder of length 2L and radius a. The current density on the cylinder is also represented using Fourier series. Any desired field can be specified in advance on the cylinder's radius, over some nonsymmetric portion pLdensity on the coil and the magnetic field components then follow automatically. The method is illustrated by applying it to three sample zonal coil designs, namely, linear, quadratic, and cubic fields located asymmetrically in the coil. Current densities and corresponding coil winding patterns are shown for these three illustrative cases. Field calculations directly from the coil patterns and spherical harmonic deconvolutions of these fields indicate that the example designs match the theory well. Asymmetric shim coils can be used in conventional symmetric MRI magnets, particularly those architected for "head-only" studies. One of their major applications is expected to be in the newly developed asymmetric magnet systems. PMID:11548933

  8. Interpreting the behavior of a quarter-wave transmission line resonator in a magnetized plasma

    NASA Astrophysics Data System (ADS)

    Gogna, G. S.; Karkari, S. K.; Turner, M. M.

    2014-12-01

    The quarter wave resonator immersed in a strongly magnetized plasma displays two possible resonances occurring either below or above its resonance frequency in vacuum, fo. This fact was demonstrated in our recent articles [G. S. Gogna and S. K. Karkari, Appl. Phys. Lett. 96, 151503 (2010); S. K. Karkari, G. S. Gogna, D. Boilson, M. M. Turner, and A. Simonin, Contrib. Plasma Phys. 50(9), 903 (2010)], where the experiments were carried out over a limited range of magnetic fields at a constant electron density, ne. In this paper, we present the observation of dual resonances occurring over the frequency scan and find that ne calculated by considering the lower resonance frequency is 25%-30% smaller than that calculated using the upper resonance frequency with respect to fo. At a given magnetic field strength, the resonances tend to shift away from fo as the background density is increased. The lower resonance tends to saturate when its value approaches electron cyclotron frequency, fce. Interpretation of these resonance conditions are revisited by examining the behavior of the resonance frequency response as a function of ne. A qualitative discussion is presented which highlights the practical application of the hairpin resonator for interpreting ne in a strongly magnetized plasma.

  9. Interpreting the behavior of a quarter-wave transmission line resonator in a magnetized plasma

    SciTech Connect

    Gogna, G. S. Turner, M. M.; Karkari, S. K.

    2014-12-15

    The quarter wave resonator immersed in a strongly magnetized plasma displays two possible resonances occurring either below or above its resonance frequency in vacuum, f{sub o}. This fact was demonstrated in our recent articles [G. S. Gogna and S. K. Karkari, Appl. Phys. Lett. 96, 151503 (2010); S. K. Karkari, G. S. Gogna, D. Boilson, M. M. Turner, and A. Simonin, Contrib. Plasma Phys. 50(9), 903 (2010)], where the experiments were carried out over a limited range of magnetic fields at a constant electron density, n{sub e}. In this paper, we present the observation of dual resonances occurring over the frequency scan and find that n{sub e} calculated by considering the lower resonance frequency is 25%–30% smaller than that calculated using the upper resonance frequency with respect to f{sub o}. At a given magnetic field strength, the resonances tend to shift away from f{sub o} as the background density is increased. The lower resonance tends to saturate when its value approaches electron cyclotron frequency, f{sub ce}. Interpretation of these resonance conditions are revisited by examining the behavior of the resonance frequency response as a function of n{sub e}. A qualitative discussion is presented which highlights the practical application of the hairpin resonator for interpreting n{sub e} in a strongly magnetized plasma.

  10. Magnetic Resonance Microscopy of Collagen Mineralization

    PubMed Central

    Chesnick, Ingrid E.; Mason, Jeffrey T.; Giuseppetti, Anthony A.; Eidelman, Naomi; Potter, Kimberlee

    2008-01-01

    A model mineralizing system was subjected to magnetic resonance microscopy to investigate how water proton transverse (T2) relaxation times and magnetization transfer ratios can be applied to monitor collagen mineralization. In our model system, a collagen sponge was mineralized with polymer-stabilized amorphous calcium carbonate. The lower hydration and water proton T2 values of collagen sponges during the initial mineralization phase were attributed to the replacement of the water within the collagen fibrils by amorphous calcium carbonate. The significant reduction in T2 values by day 6 (p < 0.001) was attributed to the appearance of mineral crystallites, which were also detected by x-ray diffraction and scanning electron microscopy. In the second phase, between days 6 and 13, magnetic resonance microscopy properties appear to plateau as amorphous calcium carbonate droplets began to coalesce within the intrafibrillar space of collagen. In the third phase, after day 15, the amorphous mineral phase crystallized, resulting in a reduction in the absolute intensity of the collagen diffraction pattern. We speculate that magnetization transfer ratio values for collagen sponges, with similar collagen contents, increased from 0.25 ± 0.02 for control strips to a maximum value of 0.31 ± 0.04 at day 15 (p = 0.03) because mineral crystals greatly reduce the mobility of the collagen fibrils. PMID:18487295

  11. Comparison of nuclear magnetic resonance spectroscopy with dual-photon absorptiometry and dual-energy X-ray absorptiometry in the measurement of thoracic vertebral bone mineral density: compressive force versus bone mineral.

    PubMed

    Myers, T J; Battocletti, J H; Mahesh, M; Gulati, M; Wilson, C R; Pintar, F; Reinartz, J

    1994-05-01

    31P nuclear magnetic resonance spectroscopy (NMRS) measurements were made on human T2 and T3 vertebral bodies. The bone mineral content (BMC) of isolated vertebral bodies minus the posterior elements and disks was measured using (1) NMRS on a 3.5 T, 85 mm bore GE Medical Systems NT-150 superconducting spectrometer, (2) a Lunar Corporation DPX-L dual-energy X-ray absorptiometry (DXA) scanner in an anterior-posterior (AP) orientation, (3) a Norland Corporation XR26 DXA scanner, also in an AP direction, and (4) a Norland Corporation model 2600 dual-photon absorptiometry (DPA) densitometer in both the AP and superior-inferior (SI) directions. Vertebral body volumes were measured using a water displacement technique to determine volume bone mineral densities (VBMD). They were then compressed to failure using an electrohydraulic testing device, followed by ashing in a muffle furnace at 700 degrees C for 18 h. Correlations of BMC between NMRS and DPA, DXA and ashing were excellent (0.96 < or = r < or = 0.99); in a one-way analysis of variance (ANOVA) test, means were not statistically different at a p level of 0.757. The correlations of VBMD between NMRS and the other methods were not as good (0.83 < or = r < or = 0.95); in a one-way ANOVA test, means were not statistically different at a p level of 0.089. BMC was a better predictor of ultimate compressive failure than VBMD for all six methods. For NMRS, the regression coefficient for BMC was r2 = 0.806, compared with r2 = 0.505 for VBMD. NMRS may prove an alternative to present methods of determining bone mineral. PMID:8069051

  12. Continuum resonance induced electromagnetic torque by a rotating plasma response to static resonant magnetic perturbation field

    SciTech Connect

    Liu Yueqiang; Connor, J. W.; Cowley, S. C.; Ham, C. J.; Hastie, R. J.; Hender, T. C.

    2012-10-15

    A numerical study is carried out, based on a simple toroidal tokamak equilibrium, to demonstrate the radial re-distribution of the electromagnetic torque density, as a result of a rotating resistive plasma (linear) response to a static resonant magnetic perturbation field. The computed electromagnetic torque peaks at several radial locations even in the presence of a single rational surface, due to resonances between the rotating response, in the plasma frame, and both Alfven and sound continuum waves. These peaks tend to merge together to form a rather global torque distribution, when the plasma resistivity is large. The continuum resonance induced net electromagnetic torque remains finite even in the limit of an ideal plasma.

  13. Developing hyperpolarized krypton-83 for nuclear magnetic resonance spectroscopy and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Cleveland, Zackary I.

    This dissertation discusses the production of highly nonequilibrium nuclear spin polarization, referred to as hyperpolarization or hp, in the nuclear spin I = 9/2 noble gas isotope krypton-83 using spin exchange optical pumping (SEOP). This nonequilibrium polarization yields nuclear magnetic resonance (NMR) signals that are enhanced three or more orders of magnitude above those of thermally polarized krypton and enables experiments that would otherwise be impossible. Krypton-83 possesses a nuclear electric quadrupole moment that dominates the longitudinal (T1) relaxation due to coupling of the quadrupole moment to fluctuating electric field gradients generated by distortions to the spherical symmetry of the electronic environment. Relaxation slows polarization buildup and limits the maximum signal intensity but makes krypton-83 a sensitive probe of its environment. The gas-phase krypton-83 longitudinal relaxation rate increases linearly with total gas density due to binary collisions. Density independent relaxation, caused by the formation of krypton-krypton van der Waals molecules and surface adsorption, also contributes to the observed rate. Buffer gases suppress van der Waals molecule mediated relaxation by breaking apart the weakly bound krypton dimers. Surface relaxation is gas composition independent and therefore more difficult to suppress. However, this relaxation mechanism makes hp krypton-83 sensitive to important surface properties including surface-to-volume ratio, surface chemistry, and surface temperature. The presence of surfaces with high krypton adsorption affinities (i.e. hydrophobic surfaces) accelerates the relaxation times and can produce T1 contrast in hp krypton-83 magnetic resonance imaging (MRI). Tobacco smoke deposited on surfaces generates strong T1 contrast allowing the observation of smoke deposition with spatial resolution. Conversely, water adsorption on surfaces significantly lengths the T1 times due competitive surface adsorption

  14. Electron series resonance plasma discharges: Unmagnetized and magnetized

    NASA Astrophysics Data System (ADS)

    Qiu, Weiguang

    2001-08-01

    This thesis explores high frequency electron series resonance in unmagnetized and magnetized bounded plasmas. Special interest is focused on low temperature plasmas in planar systems as such are useful for material processing and fusion devices. Chapter 1, Chapter 2 and Chapter 3 describe simulation studies of unmagnetized electron series resonance (ESR) sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics. The input resistance is small and the drive voltage and current are in phase. The drive voltage is small (˜Te) and the time average plasma potential is low (˜10Te). A strong kinetic phase space bunching process is shown to provide electrons of sufficient energy for ionization, which allows discharge operation at low neutral pressure and low electron temperatures. At low pressure, the ion flux to the wall has a narrow angular spread about the normal and the ion bombarding energy distribution has a sharp peak at the plasma potential. Scaling laws at fixed pressure nr∝w3RF ,s¯∝w -1RF are shown to hold when RF frequency is varied smoothly ("chirping") demonstrating continuous density control. Research on magnetized electron series resonance (MESR) discharges is described in Chapter 4, Chapter 5 and Chapter 6. The resonant frequency is derived from cold plasma theory and shows two resonant modes. Simulations verify these modes to be the natural oscillatory frequencies of weakly magnetized plasmas in a planar plasma diode. A global model is established for magnetized resonant discharges. The interrelations among the plasma parameters and the drive terms are formulated for both resonant modes. The initiation of a MESR discharge and its steady state properties are discussed and compared to the unmagnetized case. Weak lock-on of MESR frequency to the drive frequency is observed in simulation. Similar V - I characteristics as those in ESR are found both in theory and in simulation. Different from the ESR

  15. Magnetic resonance spectroscopy of the human brain

    NASA Astrophysics Data System (ADS)

    Strózik-Kotlorz, D.

    2014-01-01

    I give a brief description of the magnetic resonance spectroscopy (MRS) in the human brain examinations. MRS allows a noninvasive chemical analysis of the brain using a standard high field MR system. Nowadays, the dominant form of MR brain spectroscopy is proton spectroscopy. Two main techniques of MRS, which utilize the chemical shift of metabolites in the external magnetic field, are SVS (single voxel) and CSI (single slice). The major peaks in the spectrum of a normal brain include NAA, Cr, Cho and m-Ins, which are neuronal, energetic, membrane turnover and glial markers, respectively. In disease, two pathological metabolites can be found in the brain spectra: Lac, which is end product of anaerobic glycolysis and Lip, which is a marker of membrane breakdown, occurring in necrosis. The common way to analyze clinical spectra is to determine metabolite ratios, e.g. NAA/Cr, Cho/Cr, Cho/NAA. This analysis permits a safe and noninvasive examination of the brain tissue as each disease state has its own characteristic spectroscopic image. MRS is a valuable diagnostic tool in such clinical applications as detecting brain tumors and differentiating tumors from inflammatory and infectious processes. Proton MRS is also very helpful in diagnostic of ischemic lesions, Alzheimer's disease and hepatic encephalopathy. The MRS brain spectra should always be correlated with the Magnetic Resonance Imaging (MRI) results and alone cannot make neurological diagnosis.

  16. Magnetic resonance at the quantum limit

    NASA Astrophysics Data System (ADS)

    Bertet, Patrice

    The detection and characterization of paramagnetic species by electron-spin resonance (ESR) spectroscopy has numerous applications in chemistry, biology, and materials science. Most ESR spectrometers rely on the inductive detection of the small microwave signals emitted by the spins during their Larmor precession into a microwave resonator in which they are embedded. Using the tools offered by circuit Quantum Electrodynamics (QED), namely high quality factor superconducting micro-resonators and Josephson parametric amplifiers that operate at the quantum limit when cooled at 20mK, we report an increase of the sensitivity of inductively detected ESR by 4 orders of magnitude over the state-of-the-art, enabling the detection of 1700 Bismuth donor spins in silicon with a signal-to-noise ratio of 1 in a single echo. We also demonstrate that the energy relaxation time of the spins is limited by spontaneous emission of microwave photons into the measurement line via the resonator, which opens the way to on-demand spin initialization via the Purcell effect. These results constitute a first step towards circuit QED experiments with magnetically coupled individual spins.

  17. Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: Off-resonant and resonant cases

    NASA Astrophysics Data System (ADS)

    Cortázar, O. D.; Megía-Macías, A.; Vizcaíno-de-Julián, A.

    2013-09-01

    Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

  18. Magnetic resonance force detection using a membrane resonator

    NASA Astrophysics Data System (ADS)

    Scozzaro, Nicolas; Ruchotzke, William; Belding, Amanda; Cardellino, Jeremy; Blomberg, Erick; McCullian, Brendan; Bhallamudi, Vidya; Pelekhov, Denis; Hammel, P. Chris

    Silicon nitride (Si3N4) membranes are commercially-available, versatile structures that have a variety of applications. Although most commonly used as the support structure for transmission electron microscopy (TEM) studies, membranes are also ultrasensitive high-frequency mechanical oscillators. The sensitivity stems from the high quality factor Q 106 , which has led to applications in sensitive quantum optomechanical experiments. The high sensitivity also opens the door to ultrasensitive force detection applications. We report force detection of electron spin magnetic resonance at 300 K using a Si3N4 membrane with a force sensitivity of 4 fN/√{ Hz}, and a potential low temperature sensitivity of 25 aN/√{ Hz}. Given membranes' sensitivity, robust construction, large surface area and low cost, SiN membranes can potentially serve as the central component of a compact room-temperature ESR and NMR instrument that has superior spatial resolution to conventional NMR.

  19. Magnetic resonance acoustic radiation force imaging

    PubMed Central

    McDannold, Nathan; Maier, Stephan E.

    2008-01-01

    Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery. PMID:18777934

  20. Molecular structure and motion in zero field magnetic resonance

    SciTech Connect

    Jarvie, T.P.

    1989-10-01

    Zero field magnetic resonance is well suited for the determination of molecular structure and the study of motion in disordered materials. Experiments performed in zero applied magnetic field avoid the anisotropic broadening in high field nuclear magnetic resonance (NMR) experiments. As a result, molecular structure and subtle effects of motion are more readily observed.

  1. Magnetic resonance imaging in central pontine myelinolysis.

    PubMed Central

    Thompson, P D; Miller, D; Gledhill, R F; Rossor, M N

    1989-01-01

    Magnetic resonance imaging (MRI) was performed in two patients in whom a clinical diagnosis of central pontine myelinolysis (CPM) had been made. MRI showed lesions in the pons in both cases about 2 years after the illness, at a time when the spastic quadriparesis and pseudobulbar palsy had recovered. The persisting abnormal signals in CPM are likely to be due to fibrillary gliosis. Persistence of lesions on MRI means that the diagnosis of CPM may be electively, after the acute illness has resolved. Images PMID:2732743

  2. Multiparametric magnetic resonance imaging of prostate cancer.

    PubMed

    Hedgire, Sandeep S; Oei, Tamara N; McDermott, Shaunagh; Cao, Kai; Patel M, Zena; Harisinghani, Mukesh G

    2012-07-01

    In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up. PMID:23599562

  3. Insight into protein nuclear magnetic resonance research.

    PubMed

    Stoven, V; Lallemand, J Y; Abergel, D; Bouaziz, S; Delsuc, M A; Ekondzi, A; Guittet, E; Laplante, S; Le Goas, R; Malliavin, T

    1990-08-01

    Nuclear magnetic resonance (NMR) is one of the most powerful techniques to investigate the geometry of molecules in solution. It has been widely applied, in recent years, to the study of protein conformation. However, full reconstruction of the 3-D structure of such macro-molecules, still constitutes a real challenge for the spectroscopist. Skills as diverse as biology, spectroscopy, signal processing, or computer sciences, are required. This paper presents various aspects of the research in that domain, and our contribution to it. PMID:2126458

  4. Magnetic resonance imaging findings of intramammary metastases.

    PubMed

    Wienbeck, Susanne; Herzog, Aimee; Kinner, Sonja; Surov, Alexey

    2016-01-01

    The purpose of this study was to identify magnetic resonance imaging (MRI) findings of intramammary metastases (IM). We identified 8 cases with IM, which were investigated by breast MRI (1.5T). In every case, the diagnosis of IM was proven histopathologically on breast biopsy specimens. Overall, 187 IM were identified. IM had inconsistent MRI features, which cannot be clearly classify as benign or malignant. IM should be taken into consideration in the differential diagnosis of breast lesions to avoid possible misinterpretations. PMID:27133668

  5. Magnetic Resonance Imaging of Acute Stroke.

    PubMed

    Nael, Kambiz; Kubal, Wayne

    2016-05-01

    Neuroimaging plays a critical role in the management of patients with acute stroke syndrome, with diagnostic, therapeutic, and prognostic implications. A multiparametric magnetic resonance (MR) imaging protocol in the emergency setting can address both primary goals of neuroimaging (ie, detection of infarction and exclusion of hemorrhage) and secondary goals of neuroimaging (ie, identifying the site of arterial occlusion, tissue characterization for defining infarct core and penumbra, and determining stroke cause/mechanism). MR imaging provides accurate diagnosis of acute ischemic stroke (AIS) and can differentiate AIS from other potential differential diagnoses. PMID:27150320

  6. Magnetic Resonance of Pelvic and Gastrointestinal Emergencies.

    PubMed

    Wongwaisayawan, Sirote; Kaewlai, Rathachai; Dattwyler, Matthew; Abujudeh, Hani H; Singh, Ajay K

    2016-05-01

    Magnetic resonance (MR) imaging is gaining increased acceptance in the emergency setting despite the continued dominance of computed tomography. MR has the advantages of more precise tissue characterization, superior soft tissue contrast, and a lack of ionizing radiation. Traditional barriers to emergent MR are being overcome by streamlined imaging protocols and newer rapid-acquisition sequences. As the utilization of MR imaging in the emergency department increases, a strong working knowledge of the MR appearance of the most commonly encountered abdominopelvic pathologies is essential. In this article, MR imaging protocols and findings of acute pelvic, scrotal, and gastrointestinal pathologies are discussed. PMID:27150327

  7. New magnetic resonance imaging methods in nephrology

    PubMed Central

    Zhang, Jeff L.; Morrell, Glen; Rusinek, Henry; Sigmund, Eric; Chandarana, Hersh; Lerman, Lilach O.; Prasad, Pottumarthi Vara; Niles, David; Artz, Nathan; Fain, Sean; Vivier, Pierre H.; Cheung, Alfred K.; Lee, Vivian S.

    2013-01-01

    Established as a method to study anatomic changes, such as renal tumors or atherosclerotic vascular disease, magnetic resonance imaging (MRI) to interrogate renal function has only recently begun to come of age. In this review, we briefly introduce some of the most important MRI techniques for renal functional imaging, and then review current findings on their use for diagnosis and monitoring of major kidney diseases. Specific applications include renovascular disease, diabetic nephropathy, renal transplants, renal masses, acute kidney injury and pediatric anomalies. With this review, we hope to encourage more collaboration between nephrologists and radiologists to accelerate the development and application of modern MRI tools in nephrology clinics. PMID:24067433

  8. Developments in boron magnetic resonance imaging (MRI)

    SciTech Connect

    Schweizer, M.

    1995-11-01

    This report summarizes progress during the past year on maturing Boron-11 magnetic resonance imaging (MRI) methodology for noninvasive determination of BNCT agents (BSH) spatially in time. Three major areas are excerpted: (1) Boron-11 MRI of BSH distributions in a canine intracranial tumor model and the first human glioblastoma patient, (2) whole body Boron-11 MRI of BSH pharmacokinetics in a rat flank tumor model, and (3) penetration of gadolinium salts through the BBB as a function of tumor growth in the canine brain.

  9. Review: Magnetic resonance imaging techniques in ophthalmology

    PubMed Central

    Fagan, Andrew J.

    2012-01-01

    Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye’s propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology. PMID:23112569

  10. Pelvic applications of diffusion magnetic resonance images.

    PubMed

    Coutinho, Antonio C; Krishnaraj, Arun; Pires, Cintia E; Bittencourt, Leonardo K; Guimarães, Alexander R

    2011-02-01

    Diffusion-weighted imaging (DWI) is a powerful imaging technique in neuroimaging; its value in abdominal and pelvic imaging has only recently been appreciated as a result of improvements in magnetic resonance imaging technology. There is growing interest in the use of DWI for evaluating pathology in the pelvis. Its ability to noninvasively characterize tissues and to depict changes at a cellular level allows DWI to be an effective complement to conventional sequences of pelvic imaging, especially in oncologic patients. The addition of DWI may obviate contrast material in those with renal insufficiency or contrast material allergy. PMID:21129639

  11. Emergency Magnetic Resonance Imaging of Musculoskeletal Trauma.

    PubMed

    Kumaravel, Manickam; Weathers, William M

    2016-05-01

    Musculoskeletal (MSK) trauma is commonly encountered in the emergency department. Computed tomography and radiography are the main forms of imaging assessment, but the use of magnetic resonance (MR) imaging has become more common in the emergency room (ER) setting for evaluation of low-velocity/sports-related injury and high-velocity injury. The superior soft tissue contrast and detail provided by MR imaging gives clinicians a powerful tool in the management of acute MSK injury in the ER. This article provides an overview of techniques and considerations when using MR imaging in the evaluation of some of the common injuries seen in the ER setting. PMID:27150325

  12. Approach to breast magnetic resonance imaging interpretation.

    PubMed

    Palestrant, Sarah; Comstock, Christopher E; Moy, Linda

    2014-05-01

    With the increasing use of breast magnetic resonance (MR) imaging comes the expectation that the breast radiologist is as fluent in its interpretation as in that of mammography and breast ultrasonography. Knowledge of who should be included for imaging and how to perform the imaging are as essential as interpreting the images. When reading the examination, the radiologist should approach the images from both a global and focused perspective, synthesizing findings into a report that includes a management plan. This article reviews a systematic and organized approach to breast MR imaging interpretation. PMID:24792657

  13. 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

  14. Magnetic Field Gradient Calibration as an Experiment to Illustrate Magnetic Resonance Imaging

    ERIC Educational Resources Information Center

    Seedhouse, Steven J.; Hoffmann, Markus M.

    2008-01-01

    A nuclear magnetic resonance (NMR) spectroscopy experiment for the undergraduate physical chemistry laboratory is described that encompasses both qualitative and quantitative pedagogical goals. Qualitatively, the experiment illustrates how images are obtained in magnetic resonance imaging (MRI). Quantitatively, students experience the…

  15. Metabolite specific proton magnetic resonance imaging

    SciTech Connect

    Hurd, R.E.; Freeman, D.M.

    1989-06-01

    An imaging method is described that makes use of proton double quantum nuclear magnetic resonance (NMR) to construct images based on selected metabolites such as lactic acid. The optimization of the method is illustrated in vitro, followed by in vivo determination of lactic acid distribution in a solid tumor model. Water suppression and editing of lipid signals are such that two-dimensional spectra of lactic acid may be obtained from a radiation-induced fibrosarcoma (RIF-1) tumor in under 1 min and lactic acid images from the same tumor in under 1 hr at 2.0 T. This technique provides a fast and reproducible method at moderate magnetic field strength for mapping biologically relevant metabolites.

  16. In vivo nuclear magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Leblanc, A.

    1986-05-01

    During the past year the Woodlands Baylor Magnetic Resonance Imaging (MRI) facility became fully operational. A detailed description of this facility is given. One significant instrument addition this year was the 100 MHz, 40cm bore superconducting imaging spectrometer. This instrument gives researchers the capability to acquire high energy phosphate spectra. This will be used to investigate ATP, phosphocreatinine and inorganic phosphate changes in normal and atrophied muscle before, during and after exercise. An exercise device for use within the bore of the imaging magnet is under design/construction. The results of a study of T sub 1 and T sub 2 changes in atrophied muscle in animals and human subjects are given. The imaging and analysis of the lower leg of 15 research subjects before and after 5 weeks of complete bedrest was completed. A compilation of these results are attached.

  17. In vivo nuclear magnetic resonance imaging

    NASA Technical Reports Server (NTRS)

    Leblanc, A.

    1986-01-01

    During the past year the Woodlands Baylor Magnetic Resonance Imaging (MRI) facility became fully operational. A detailed description of this facility is given. One significant instrument addition this year was the 100 MHz, 40cm bore superconducting imaging spectrometer. This instrument gives researchers the capability to acquire high energy phosphate spectra. This will be used to investigate ATP, phosphocreatinine and inorganic phosphate changes in normal and atrophied muscle before, during and after exercise. An exercise device for use within the bore of the imaging magnet is under design/construction. The results of a study of T sub 1 and T sub 2 changes in atrophied muscle in animals and human subjects are given. The imaging and analysis of the lower leg of 15 research subjects before and after 5 weeks of complete bedrest was completed. A compilation of these results are attached.

  18. A new resonance based method for the measurement of magnetic field intensity

    NASA Astrophysics Data System (ADS)

    Kaluvan, Suresh; Park, Jinhyuk; Zhang, Haifeng; Umapathy, Mangalanathan; Choi, Seung-Bok

    2016-04-01

    A new magnetic field intensity measurement method using resonance principle is proposed in this paper. The proposed magnetic field sensor consists of magneto rheological (MR) fluid placed between two collocated, piezo-bounded, metallic, circular disc mounted face to face in the z-axis. The resonant frequency of the disc is changed by the magnetic field dependent viscosity of the MR fluid. The key enabling concept in this work is stiffening the circular metal disc using the rheological effect of MR fluid i.e. resonant frequency varies with respect to magnetic field strength. The change in resonant frequency is measured using simple closed loop electronics connected between the two piezo crystals. The analytical model of the vibrating circular discs with MR fluid placed at the center is derived and the results are validated with experimentation. The proposed magnetic flux density measurement concept is novel and it is found to have better sensitivity and linearity.

  19. Multiparametric magnetic resonance imaging: Current role in prostate cancer management.

    PubMed

    Ueno, Yoshiko; Tamada, Tsutomu; Bist, Vipul; Reinhold, Caroline; Miyake, Hideaki; Tanaka, Utaru; Kitajima, Kazuhiro; Sugimura, Kazuro; Takahashi, Satoru

    2016-07-01

    Digital rectal examination, serum prostate-specific antigen screening and transrectal ultrasound-guided biopsy are conventionally used as screening, diagnostic and surveillance tools for prostate cancer. However, they have limited sensitivity and specificity. In recent years, the role of multiparametric magnetic resonance imaging has steadily grown, and is now part of the standard clinical management in many institutions. In multiparametric magnetic resonance imaging, the morphological assessment of T2-weighted imaging is correlated with diffusion-weighted imaging, dynamic contrast-enhanced imaging perfusion and/or magnetic resonance spectroscopic imaging. Multiparametric magnetic resonance imaging is currently regarded as the most sensitive and specific imaging technique for the evaluation of prostate cancer, including detection, staging, localization and aggressiveness evaluation. This article presents an overview of multiparametric magnetic resonance imaging, and discusses the current role of multiparametric magnetic resonance imaging in the different fields of prostate cancer management. PMID:27184019

  20. Plasmon coupling of magnetic resonances in an asymmetric gold semishell

    NASA Astrophysics Data System (ADS)

    Ye, Jian; Kong, Yan; Liu, Cheng

    2016-05-01

    The generation of magnetic dipole resonances in metallic nanostructures is of great importance for constructing near-zero or even negative refractive index metamaterials. Commonly, planar two-dimensional (2D) split-ring resonators or relevant structures are basic elements of metamaterials. In this work, we introduce a three-dimensional (3D) asymmetric Au semishell composed of two nanocups with a face-to-face geometry and demonstrate two distinct magnetic resonances spontaneously in the visible–near infrared optical wavelength regime. These two magnetic resonances are from constructive and destructive hybridization of magnetic dipoles of individual nanocups in the asymmetric semishell. In contrast, complete cancellation of magnetic dipoles in the symmetric semishell leads to only a pronounced electric mode with near-zero magnetic dipole moment. These 3D asymmetric resonators provide new ways for engineering hybrid resonant modes and ultra-high near-field enhancement for the design of 3D metamaterials.

  1. Fano resonance generated by magnetic scatterer in micro metal slit

    NASA Astrophysics Data System (ADS)

    Zhou, Yun-Song; Wang, Pei-Jie; Wang, Hai; Feng, Sheng-Fei

    2014-09-01

    A micro metal slit/magnetic scatterer structure is proposed to generate electromagnetic Fano resonance. The magnetic scatterer is formed by infinite long split cylinder resonator array. The analytical transmissivity formulas are deduced from Maxwell electromagnetic theory and the Fano resonance transmission is achieved by the theoretical calculations. The enhancement of environment refractive index leads to an ultrasensitive and linear red shift of resonance peak in the THz range.

  2. Modelling of Resonantly Forced Density Waves in Dense Planetary Rings

    NASA Astrophysics Data System (ADS)

    Lehmann, M.; Schmidt, J.; Salo, H.

    2014-04-01

    Density wave theory, originally proposed to explain the spiral structure of galactic disks, has been applied to explain parts of the complex sub-structure in Saturn's rings, such as the wavetrains excited at the inner Lindblad resonances (ILR) of various satellites. The linear theory for the excitation and damping of density waves in Saturn's rings is fairly well developed (e.g. Goldreich & Tremaine [1979]; Shu [1984]). However, it fails to describe certain aspects of the observed waves. The non-applicability of the linear theory is already indicated by the "cusplike" shape of many of the observed wave profiles. This is a typical nonlinear feature which is also present in overstability wavetrains (Schmidt & Salo [2003]; Latter & Ogilvie [2010]). In particular, it turns out that the detailed damping mechanism, as well as the role of different nonlinear effects on the propagation of density waves remain intransparent. First attemps are being made to investigate the excitation and propagation of nonlinear density waves within a hydrodynamical formalism, which is also the natural formalism for describing linear density waves. A simple weakly nonlinear model, derived from a multiple-scale expansion of the hydrodynamic equations, is presented. This model describes the damping of "free" spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients, where the effects of the hydrodynamic nonlinearities are included. The model predicts that density waves are linearly unstable in a ring region where the conditions for viscous overstability are met, which translates to a steep dependence of the shear viscosity with respect to the disk's surface density. The possibility that this dependence could lead to a growth of density waves with increasing distance from the resonance, was already mentioned in Goldreich & Tremaine [1978]. Sufficiently far away from the ILR, the surface density perturbation caused by the wave, is predicted to

  3. Density Limits in Toroidal Magnetic Confinement Experiments

    NASA Astrophysics Data System (ADS)

    Greenwald, Martin

    2001-10-01

    The density limit represents one of the fundamental operating boundaries for magnetic confinement devices - one with practical importance to the goal of fusion power. With fusion reactivity maximized at a plasma temperature on the order of 10 keV and a reaction rate scaling as n^2, an optimum density can be calculated which is not guaranteed to be achievable in any given device. Unlike operational limits for plasma current or pressure, the density limit cannot be explained by magneto-hydrodynamics alone. There is general agreement that the proximate cause for the disruptive limit in the tokamak is cooling of the plasma edge and subsequent current profile shrinkage. The edge cooling may be dominated by atomic physics processes or as suggested in recent experiments, by anomalous transport. A similar picture is emerging for the reversed field pinch (RFP), while the limit in stellarators is apparently due to loss of thermal equilibrium from radiation. Empirical scaling laws in which the maximum plasma density is proportional to the average current density have been fairly successful in predicting the limit for subsequent experiments. Surprisingly, the density limits found in tokamaks and RFPs are virtually identical. Currentless stellarators reach similar density limits, though the expression needs to be recast in terms of the rotational transform. While scaling laws have done a reasonable job in describing data from many recent experiments, they can only give hints at the underlying physics. Understanding the mechanism for the density limit is crucial for extrapolating machine performance into untested regimes and so far, a completely satisfactory theory has not emerged. It seems likely that robust, reliable predictions will only come from the development of a first-principles theory backed up by detailed experimental observations. The extensive work already accomplished and reviewed here should provide a solid basis for such development.

  4. Magnetic resonance imaging of the central nervous system

    SciTech Connect

    Brant-Zawadzki, M.; Norman, D.

    1987-01-01

    This book presents the papers on technological advancement and diagnostic uses g magnetic resonance imaging. A comparative evaluation with computerized tomography is presented. Topics covered are imaging principles g magnetic resonance;instrumentation of magnetic resonance (MR);pathophysiology;quality and limitations g images;NMR imaging of brain and spinal cord;MR spectroscopy and its applications;neuroanatomy;Congenital malformations of brain and MR imaging;planning g MR imaging of spine and head and neck imaging.

  5. Science Drivers and Technical Challenges for Advanced Magnetic Resonance

    SciTech Connect

    Mueller, Karl T.; Pruski, Marek; Washton, Nancy M.; Lipton, Andrew S.

    2013-03-07

    This report recaps the "Science Drivers and Technical Challenges for Advanced Magnetic Resonance" workshop, held in late 2011. This exploratory workshop's goal was to discuss and address challenges for the next generation of magnetic resonance experimentation. During the workshop, participants from throughout the world outlined the science drivers and instrumentation demands for high-field dynamic nuclear polarization (DNP) and associated magnetic resonance techniques, discussed barriers to their advancement, and deliberated the path forward for significant and impactful advances in the field.

  6. Massive subchorionic thrombosis followed by magnetic resonance imaging.

    PubMed

    Himoto, Yuki; Okumura, Ryosuke; Tsuji, Natsuki; Nagano, Tadayoshi; Fujimoto, Masakazu; Yamaoka, Toshihide; Kohno, Shigene

    2012-01-01

    Massive subchorionic thrombosis is a rare condition, defined as a large thrombus confined to the subchorionic space. It is associated with poor perinatal prognosis. However, prenatal diagnosis by ultrasonography is often difficult. We report a case of massive subchorionic thrombosis developing dermatomyositis after the delivery, followed by magnetic resonance imaging. Moreover, we review other 4 cases assessed with magnetic resonance imaging. Magnetic resonance imaging is very useful for confirmation of diagnosis and follow-up in combination with ultrasonography. PMID:22592619

  7. Magnetic resonance force microscopy combined with surface topography

    NASA Astrophysics Data System (ADS)

    Tsuji, S.; Yoshinari, Y.; Kawai, E.; Nakajima, K.; Park, H. S.; Shindo, D.

    2007-10-01

    A new method of surface microscopy is proposed, which combines three-dimensional electron spin resonance imaging by magnetic resonance force microscopy (MRFM) and topographic imaging of the sample surface by scanning force microscopy (SFM). In order to demonstrate its potential for the identification of microscale objects, the individual and combined images are used to provide the locations, shapes and spin density distributions of target phantom objects. We report spatial resolution in MRFM of 2.8 × 2.8 × 2.0μm 3. This could be improved to the theoretical limit of 0.08 × 0.08 × 0.04μm 3 through reduction of the thermal noise by cooling to cryogenic temperatures ˜0.5 K. We believe that this type of microscopy will become a very useful tool for the investigation of anomalies induced in surfaces by materials buried below the surface.

  8. General review of magnetic resonance elastography

    PubMed Central

    Low, Gavin; Kruse, Scott A; Lomas, David J

    2016-01-01

    Magnetic resonance elastography (MRE) is an innovative imaging technique for the non-invasive quantification of the biomechanical properties of soft tissues via the direct visualization of propagating shear waves in vivo using a modified phase-contrast magnetic resonance imaging (MRI) sequence. Fundamentally, MRE employs the same physical property that physicians utilize when performing manual palpation - that healthy and diseased tissues can be differentiated on the basis of widely differing mechanical stiffness. By performing “virtual palpation”, MRE is able to provide information that is beyond the capabilities of conventional morphologic imaging modalities. In an era of increasing adoption of multi-parametric imaging approaches for solving complex problems, MRE can be seamlessly incorporated into a standard MRI examination to provide a rapid, reliable and comprehensive imaging evaluation at a single patient appointment. Originally described by the Mayo Clinic in 1995, the technique represents the most accurate non-invasive method for the detection and staging of liver fibrosis and is currently performed in more than 100 centers worldwide. In this general review, the mechanical properties of soft tissues, principles of MRE, clinical applications of MRE in the liver and beyond, and limitations and future directions of this discipline -are discussed. Selected diagrams and images are provided for illustration. PMID:26834944

  9. Magnetic Resonance Imaging in Pediatric Pulmonary Hypertension

    PubMed Central

    Olgunturk, Rana; Cevik, Ayhan; Terlemez, Semiha; Kacar, Emre; Oner, Yusuf Ali

    2015-01-01

    The present study aims to determine the efficacy and reliability of cardiovascular magnetic resonance imaging in establishing the diagnosis and prognosis of pulmonary hypertension in children. This is a retrospective comparison of 25 children with pulmonary hypertension and a control group comprising 19 healthy children. The diagnosis of pulmonary hypertension was made when the mean pulmonary artery pressure was ≥25 mmHg by catheter angiography. The children with pulmonary hypertension had significantly lower body mass indices than did the healthy children (P=0.048). In addition, the children with pulmonary hypertension had significantly larger main pulmonary artery diameters and ascending aortic diameters (both P=0.001) but statistically similar ratios of main pulmonary artery diameter-to-ascending aortic diameter. If the main pulmonary artery diameter was ≥25 mm, pediatric pulmonary hypertension was diagnosed with 72% sensitivity and 84% specificity. In the event that the ratio of main pulmonary artery diameter-to-ascending aorta diameter was ≥1, pediatric pulmonary hypertension was diagnosed with 60% sensitivity and 53% specificity. When compared with children who had New York Heart Association functional class II pulmonary hypertension, the children with functional class III pulmonary hypertension had significantly larger main (P=0.046), right (P=0.036), and left (P=0.003) pulmonary arteries. Cardiovascular magnetic resonance imaging is useful in the diagnosis of children with pulmonary hypertension. Pediatric pulmonary hypertension can be diagnosed with high sensitivity and specificity when the main pulmonary artery diameter measures ≥25 mm. PMID:26175631

  10. General review of magnetic resonance elastography.

    PubMed

    Low, Gavin; Kruse, Scott A; Lomas, David J

    2016-01-28

    Magnetic resonance elastography (MRE) is an innovative imaging technique for the non-invasive quantification of the biomechanical properties of soft tissues via the direct visualization of propagating shear waves in vivo using a modified phase-contrast magnetic resonance imaging (MRI) sequence. Fundamentally, MRE employs the same physical property that physicians utilize when performing manual palpation - that healthy and diseased tissues can be differentiated on the basis of widely differing mechanical stiffness. By performing "virtual palpation", MRE is able to provide information that is beyond the capabilities of conventional morphologic imaging modalities. In an era of increasing adoption of multi-parametric imaging approaches for solving complex problems, MRE can be seamlessly incorporated into a standard MRI examination to provide a rapid, reliable and comprehensive imaging evaluation at a single patient appointment. Originally described by the Mayo Clinic in 1995, the technique represents the most accurate non-invasive method for the detection and staging of liver fibrosis and is currently performed in more than 100 centers worldwide. In this general review, the mechanical properties of soft tissues, principles of MRE, clinical applications of MRE in the liver and beyond, and limitations and future directions of this discipline -are discussed. Selected diagrams and images are provided for illustration. PMID:26834944

  11. PLANTAR THROMBOPHLEBITIS: MAGNETIC RESONANCE IMAGING FINDINGS

    PubMed Central

    Miranda, Frederico Celestino; Carneiro, Renato Duarte; Longo, Carlos Henrique; Fernandes, Túlio Diniz; Rosemberg, Laércio Alberto; de Gusmão Funari, Marcelo Buarque

    2015-01-01

    Objective: Demonstrate the magnetic resonance imaging (MRI) findings in plantar thrombophlebitis. Methods: Retrospective review of twenty patients with pain in the plantar region of the foot, in which the MRI findings indicated plantar thrombophlebitis. Results: A total of fourteen men and six women, mean age 46.7 years were evaluated. Eight of these patients also underwent Doppler ultrasonography, which confirmed the thrombophlebitis. The magnetic resonance images were evaluated in consensus by two radiologists with experience in musculoskeletal radiology (more than 10 years each), showing perivascular edema in all twenty patients (100%) and muscle edema in nineteen of the twenty patients (95%). All twenty patients had intraluminal intermediate signal intensity on T2-weighted (100%) and venous ectasia was present in seventeen of the twenty cases (85%). Collateral veins were visualized in one of the twenty patients (5%). All fourteen cases (100%), in which intravenous contrast was administered, showed perivenular tissues enhancement and intraluminal filling defect. Venous ectasia, loss of compressibility and no flow on Doppler ultrasound were also observed in all eight cases examined by the method. Conclusion: MRI is a sensitive in the evaluation of plant thrombophlebitis in patients with plantar foot pain. PMID:27047898

  12. Magnetic resonance elastography hardware design: a survey.

    PubMed

    Tse, Z T H; Janssen, H; Hamed, A; Ristic, M; Young, I; Lamperth, M

    2009-05-01

    Magnetic resonance elastography (MRE) is an emerging technique capable of measuring the shear modulus of tissue. A suspected tumour can be identified by comparing its properties with those of tissues surrounding it; this can be achieved even in deep-lying areas as long as mechanical excitation is possible. This would allow non-invasive methods for cancer-related diagnosis in areas not accessible with conventional palpation. An actuating mechanism is required to generate the necessary tissue displacements directly on the patient in the scanner and three different approaches, in terms of actuator action and position, exist to derive stiffness measurements. However, the magnetic resonance (MR) environment places considerable constraints on the design of such devices, such as the possibility of mutual interference between electrical components, the scanner field, and radio frequency pulses, and the physical space restrictions of the scanner bore. This paper presents a review of the current solutions that have been developed for MRE devices giving particular consideration to the design criteria including the required vibration frequency and amplitude in different applications, the issue of MR compatibility, actuation principles, design complexity, and scanner synchronization issues. The future challenges in this field are also described. PMID:19499839

  13. Magnetic resonance imaging. Application to family practice.

    PubMed Central

    Goh, R. H.; Somers, S.; Jurriaans, E.; Yu, J.

    1999-01-01

    OBJECTIVE: To review indications, contraindications, and risks of using magnetic resonance imaging (MRI) in order to help primary care physicians refer patients appropriately for MRI, screen for contraindications to using MRI, and educate patients about MRI. QUALITY OF EVIDENCE: Recommendations are based on classic textbooks, the policies of our MRI group, and a literature search using MEDLINE with the MeSH headings magnetic resonance imaging, brain, musculoskeletal, and spine. The search was limited to human, English-language, and review articles. Evidence in favour of using MRI for imaging the head, spine, and joints is well established. For cardiac, abdominal, and pelvic conditions, MRI has been shown useful for certain indications, usually to complement other modalities. MAIN MESSAGE: For demonstrating soft tissue conditions, MRI is better than computed tomography (CT), but CT shows bone and acute bleeding better. Therefore, patients with trauma or suspected intracranial bleeding should have CT. Tumours, congenital abnormalities, vascular structures, and the cervical or thoracic spine show better on MRI. Either modality can be used for lower back pain. Cardiac, abdominal, and pelvic abnormalities should be imaged with ultrasound or CT before MRI. Contraindications for MRI are mainly metallic implants or shrapnel, severe claustrophobia, or obesity. CONCLUSIONS: With the increasing availability of MRI scanners in Canada, better understanding of the indications, contraindications, and risks will be helpful for family physicians and their patients. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 PMID:10509224

  14. Magnetic resonance-guided thermal surgery.

    PubMed

    Cline, H E; Schenck, J F; Watkins, R D; Hynynen, K; Jolesz, F A

    1993-07-01

    A demonstration of MR guided thermal surgery involved experiments with imaging of focused ultrasound in an MRI system, measurements of the thermal transients and a thermal analysis of the resulting images. Both the heat distribution and the creation of focused ultrasound lesions in gel phantoms, in vitro bovine muscle and in vivo rabbit muscle were monitored with magnetic resonance imaging. Thermal surgical procedures were modeled by an elongated gaussian heat source where heat flow is controlled by tissue thermal properties and tissue perfusion. Temperature profiles were measured with thermocouples or calculated from magnetic resonance imaging in agreement with the model. A 2-s T1-weighted gradient-refocused acquisition provided thermal profiles needed to localize the heat distribution produced by a 4-s focused ultrasound pulse. Thermal analysis of the images give an effective thermal diffusion coefficient of 0.0015 cm2/s in gel and 0.0033 cm2/s in muscle. The lesions were detected using a T2-weighted spin-echo or fast spin-echo pulse sequence in agreement with muscle tissue sections. Potential thermal surgery applications are in the prostate, liver, kidney, bladder, breast, eye and brain. PMID:8371680

  15. Magnetic resonance imaging in pediatric pulmonary hypertension.

    PubMed

    Pektas, Ayhan; Olgunturk, Rana; Cevik, Ayhan; Terlemez, Semiha; Kacar, Emre; Oner, Yusuf Ali

    2015-06-01

    The present study aims to determine the efficacy and reliability of cardiovascular magnetic resonance imaging in establishing the diagnosis and prognosis of pulmonary hypertension in children. This is a retrospective comparison of 25 children with pulmonary hypertension and a control group comprising 19 healthy children. The diagnosis of pulmonary hypertension was made when the mean pulmonary artery pressure was ≥25 mmHg by catheter angiography. The children with pulmonary hypertension had significantly lower body mass indices than did the healthy children (P=0.048). In addition, the children with pulmonary hypertension had significantly larger main pulmonary artery diameters and ascending aortic diameters (both P=0.001) but statistically similar ratios of main pulmonary artery diameter-to-ascending aortic diameter. If the main pulmonary artery diameter was ≥25 mm, pediatric pulmonary hypertension was diagnosed with 72% sensitivity and 84% specificity. In the event that the ratio of main pulmonary artery diameter-to-ascending aorta diameter was ≥1, pediatric pulmonary hypertension was diagnosed with 60% sensitivity and 53% specificity. When compared with children who had New York Heart Association functional class II pulmonary hypertension, the children with functional class III pulmonary hypertension had significantly larger main (P=0.046), right (P=0.036), and left (P=0.003) pulmonary arteries. Cardiovascular magnetic resonance imaging is useful in the diagnosis of children with pulmonary hypertension. Pediatric pulmonary hypertension can be diagnosed with high sensitivity and specificity when the main pulmonary artery diameter measures ≥25 mm. PMID:26175631

  16. Magnetic resonance imaging of spinal injury.

    PubMed

    Tracy, P T; Wright, R M; Hanigan, W C

    1989-03-01

    Magnetic resonance imaging (MRI) was performed on 30 patients following spinal injury (SI). Spin-echo sequences and surface coils were used for all patients. Plain radiographs, high-resolution computed tomography (CT), and MRI were compared for the delineation of bone, disc, and ligament injury, measurement of sagittal spinal canal diameter and subluxation, epidural hematoma, and spinal cord structure. Myelography or intrathecal contrast-enhanced CT were not performed on any of these patients. Magnetic resonance imaging accurately delineated intraspinal pathology in two of four patients with acute penetrating SI, and was normal in the other two patients. In 16 patients with acute nonpenetrating SI, MRI was superior to CT for visualizing injuries to discs, ligaments, and the spinal cord, while CT was superior to MRI in characterizing bony injury. Computed tomography and MRI provided similar measurements of subluxation in six of six patients and of sagittal spinal canal diameter in three of four patients. In ten patients with chronic SI, MRI demonstrated post-traumatic cysts, myelomalacia, spinal cord edema, and the presence or absence of spinal cord compression. In patients with acute penetrating SI and chronic SI, MRI provided comprehensive clinical information. In patients with acute nonpenetrating SI, the information obtained by MRI complemented the data given by plain radiographs and CT, allowing clinical decisions to be made without the need of invasive imaging modalities. PMID:2711244

  17. The Feasibility of Magnetic Resonance Imaging for Quantification of Liver, Pancreas, Spleen, Vertebral Bone Marrow, and Renal Cortex R2* and Proton Density Fat Fraction in Transfusion-Related Iron Overload

    PubMed Central

    İdilman, İlkay S.; Gümrük, Fatma; Haliloğlu, Mithat; Karçaaltıncaba, Muşturay

    2016-01-01

    Objective: We aimed to evaluate the feasibility of quantification of liver, pancreas, spleen, vertebral bone marrow, and renal cortex R2* and magnetic resonance imaging-proton density fat fraction (MRI-PDFF) and to evaluate the correlations among them in patients with transfusion-related iron overload. Materials and Methods: A total of 9 patients (5 boys, 4 girls) who were referred to our clinic with suspicion of hepatic iron overload were included in this study. All patients underwent T1-independent volumetric multi-echo gradient-echo imaging with T2* correction and spectral fat modeling. MRI examinations were performed on a 1.5 T MRI system. Results: All patients had hepatic iron overload. Severe hepatic iron overload was recorded in 5/9 patients (56%), and when we evaluated the PDFF maps of these patients, we observed an extensive patchy artifact in the liver in 4 of 5 patients (R2* greater than 671 Hz). When we performed MRI-PDFF measurements despite these artifacts, we observed artifactual high MRI-PDFF values. There was a close correlation between average pancreas R2* and average pancreas MRI-PDFF (p=0.003, r=0.860). There was a significant correlation between liver R2* and average pancreas R2* (p=0.021, r=0.747), liver R2* and renal cortex R2* (p=0.020, r=0.750), and average pancreas R2* and renal cortex R2* (p=0.003, r=0.858). There was a significant negative correlation between vertebral bone marrow R2* and age (p=0.018, r=-0.759). Conclusion: High iron content of the liver, especially with a T2* value shorter than the first echo time can spoil the efficacy of PDFF calculation. Fat deposition in the pancreas is accompanied by pancreatic iron overload. There is a significant correlation between hepatic siderosis and pancreatic siderosis. Renal cortical and pancreatic siderosis are correlated, too. PMID:26376710

  18. The {sup 57}Fe nuclear magnetic resonance shielding in ferrocene revisited. A density-functional study of orbital energies, shielding mechanisms, and the influence of the exchange-correlation functional

    SciTech Connect

    Schreckenbach, G.

    1999-06-01

    The {sup 57}Fe nuclear magnetic resonance (NMR) shielding and chemical shift in ferrocene, Fe(C{sub 5}H{sub 5}){sub 2}, are studied using density functional theory (DFT) and gauge-including atomic orbitals (GIAO). Electronic factors contributing to the chemical shift are discussed in detail. It is shown that the chemical shift is entirely determined by paramagnetic contributions which in turn are dominated by metal based occupied-virtual d{r_arrow}d couplings. In particular, the HOMO-1(a{sub 1}{sup {prime}}) and the HOMO (e{sub 2}{sup {prime}}) couple with the LUMO (e{sub 1}{sup {double_prime}}). It is argued that the {sup 57}Fe nucleus in ferrocene is less shielded than in the reference compound (iron pentacarbonyl) due to a smaller HOMO-LUMO gap, resulting in stronger interactions between occupied and virtual orbitals. The influence of the XC functional on the calculated molecular orbital (MO) energies of frontier orbitals is discussed. Different generalized gradient approximations (GGA) give similar results whereas hybrid functionals that incorporate part of the Hartree{endash}Fock exchange stabilize occupied MOs strongly and destabilize virtual MOs. HOMO-LUMO gaps are nearly doubled as a result. The previously noted {open_quotes}dramatic influence{close_quotes} of different exchange-correlation (XC) functionals on the calculated chemical shifts is analyzed. The influence of the XC functional is realized through the paramagnetic part of the shielding; hybrid functionals increase it in absolute terms as compared to pure DFT (GGA). It is argued that three factors are responsible. These are (i) the increased occupied-virtual gaps, (ii) the more diffuse nature of virtual orbitals, and (iii) the coupling due to the Hartree{endash}Fock exchange in hybrid functionals. The last two factors increase the paramagnetic part of the shielding, and this effect is only partly reversed by the increased occupied-virtual gaps that result in reduced interactions. It is suggested

  19. Phosphorus 31 nuclear magnetic resonance examination of female reproductive tissues

    SciTech Connect

    Noyszewski, E.A.; Raman, J.; Trupin, S.R.; McFarlin, B.L.; Dawson, M.J. )

    1989-08-01

    Nuclear magnetic resonance spectroscopy is a powerful method of investigating the relationship between metabolism and function in living tissues. We present evidence that the phosphorus 31 spectra of myometrium and placenta are functions of physiologic state and gestational age. Specific spectroscopic abnormalities are observed in association with disorders of pregnancy and gynecologic diseases. Our results suggest that noninvasive nuclear magnetic resonance spectroscopy examinations may sometimes be a useful addition to magnetic resonance imaging examinations, and that nuclear magnetic resonance spectroscopy of biopsy specimens could become a cost-effective method of evaluating certain biochemical abnormalities.

  20. Textured-surface quartz resonator fluid density and viscosity monitor

    DOEpatents

    Martin, Stephen J.; Wiczer, James J.; Cernosek, Richard W.; Frye, Gregory C.; Gebert, Charles T.; Casaus, Leonard; Mitchell, Mary A.

    1998-08-25

    A pair of thickness-shear mode resonators, one smooth and one with a textured surface, allows fluid density and viscosity to be independently resolved. A textured surface, either randomly rough or regularly patterned, leads to trapping of liquid at the device surface. The synchronous motion of this trapped liquid with the oscillating device surface allows the device to weigh the liquid; this leads to an additional response that depends on liquid density. This additional response enables a pair of devices, one smooth and one textured, to independently resolve liquid density and viscosity; the difference in responses determines the density while the smooth device determines the density-viscosity product, and thus, the pair determines both density and viscosity.

  1. Reciprocity and gyrotropism in magnetic resonance transduction

    SciTech Connect

    Tropp, James

    2006-12-15

    We give formulas for transduction in magnetic resonance - i.e., the appearance of an emf due to Larmor precession of spins - based upon the modified Lorentz reciprocity principle for gyrotropic (also called 'nonreciprocal') media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e. (H{sub 1x}{+-}iH{sub 1y}), where, e.g., for a single transceive antenna, the H's are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are

  2. Nuclear magnetic resonance in magnets with a helicoidal magnetic structure in an external magnetic field

    NASA Astrophysics Data System (ADS)

    Tankeyev, A. P.; Borich, M. A.; Smagin, V. V.

    2014-11-01

    In this review, the static and dynamic properties of a magnet with a helicoidal magnetic structure placed in an external magnetic field are discussed. The results of the investigation of its ground state and spectra, as well as the amplitudes of the spin excitations are presented. The temperature and field dependences of the basic thermodynamic characteristics (heat capacity, magnetization, and magnetic susceptibility) have been calculated in the spin-wave approximation. The results of calculating the local and integral dynamic magnetic susceptibility are given. This set of data represents a methodical basis for constructing a consistent (in the framework of unified approximations) picture of the NMR absorption in the magnet under consideration. Both local NMR characteristics (resonance frequency, line broadening, enhancement coefficient) and integral characteristics (resultant shape of the absorption line with its specific features) have been calculated. The effective Hamiltonian of the Suhl-Nakamura interaction of nuclear spins through spin waves has been constructed. The second moment and the local broadening of the line of the NMR absorption caused by this interaction have been calculated. The role of the basic local inhomogeneities in the formation of the integral line of the NMR absorption has been analyzed. The opportunities for the experimental NMR investigations in magnets with a chiral spin structure are discussed.

  3. Secondary resonance magnetic force microscopy using an external magnetic field for characterization of magnetic thin films

    NASA Astrophysics Data System (ADS)

    Liu, Dongzi; Mo, Kangxin; Ding, Xidong; Zhao, Liangbing; Lin, Guocong; Zhang, Yueli; Chen, Dihu

    2015-09-01

    A bimodal magnetic force microscopy (MFM) that uses an external magnetic field for the detection and imaging of magnetic thin films is developed. By applying the external modulation magnetic field, the vibration of a cantilever probe is excited by its magnetic tip at its higher eigenmode. Using magnetic nanoparticle samples, the capacity of the technique which allows single-pass imaging of topography and magnetic forces is demonstrated. For the detection of magnetic properties of thin film materials, its signal-to-noise ratio and sensitivity are demonstrated to be superior to conventional MFM in lift mode. The secondary resonance MFM technique provides a promising tool for the characterization of nanoscale magnetic properties of various materials, especially of magnetic thin films with weak magnetism.

  4. BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE

    SciTech Connect

    Tycko, R.

    1984-10-01

    Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. The fixed points of the function and the stability of the fixed points are shown to determine the essential behavior of the scheme. Iterative schemes for broadband population inversion are treated in detail. Algebraic and numerical methods for performing the mathematical analysis are presented. Two additional topics are treated. The first is the construction of sequences for uniform excitation of double-quantum coherence and for uniform polarization transfer over a range of spin couplings. Double-quantum excitation sequences are demonstrated in a liquid crystal system. The

  5. Acoustic noise during functional magnetic resonance imaginga)

    PubMed Central

    Ravicz, Michael E.; Melcher, Jennifer R.; Kiang, Nelson Y.-S.

    2007-01-01

    Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For studies of the auditory system, acoustic noise generated during fMRI can interfere with assessments of this activation by introducing uncontrolled extraneous sounds. As a first step toward reducing the noise during fMRI, this paper describes the temporal and spectral characteristics of the noise present under typical fMRI study conditions for two imagers with different static magnetic field strengths. Peak noise levels were 123 and 138 dB re 20 μPa in a 1.5-tesla (T) and a 3-T imager, respectively. The noise spectrum (calculated over a 10-ms window coinciding with the highest-amplitude noise) showed a prominent maximum at 1 kHz for the 1.5-T imager (115 dB SPL) and at 1.4 kHz for the 3-T imager (131 dB SPL). The frequency content and timing of the most intense noise components indicated that the noise was primarily attributable to the readout gradients in the imaging pulse sequence. The noise persisted above background levels for 300-500 ms after gradient activity ceased, indicating that resonating structures in the imager or noise reverberating in the imager room were also factors. The gradient noise waveform was highly repeatable. In addition, the coolant pump for the imager’s permanent magnet and the room air handling system were sources of ongoing noise lower in both level and frequency than gradient coil noise. Knowledge of the sources and characteristics of the noise enabled the examination of general approaches to noise control that could be applied to reduce the unwanted noise during fMRI sessions. PMID:11051496

  6. Nuclear magnetic and quadrupole resonance studies of the stripes materials

    NASA Astrophysics Data System (ADS)

    Grafe, H.-J.

    2012-11-01

    Nuclear Magnetic and Quadrupole Resonance (NMR/NQR) is a powerful tool to probe electronic inhomogeneities in correlated electron systems. Its local character allows for probing different environments due to spin density modulations or inhomogeneous doping distributions emerging from the correlations in these systems. In fact, NMR/NQR is not only sensitive to magnetic properties through interaction of the nuclear spin, but also allows to probe the symmetry of the charge distribution and its homogeneity, as well as structural modulations, through sensitivity to the electric field gradient (EFG). We review the results of NMR and NQR in the cuprates from intrinsic spatial variations of the hole concentration in the normal state to stripe order at low temperatures, thereby keeping in mind the influence of doping induced disorder and inhomogeneities. Finally, we briefly discuss NQR evidence for local electronic inhomogeneities in the recently discovered iron pnictides, suggesting that electronic inhomogeneities are a common feature of correlated electron systems.

  7. Tuning Mie scattering resonances in soft materials with magnetic fields.

    PubMed

    Brunet, Thomas; Zimny, Kevin; Mascaro, Benoit; Sandre, Olivier; Poncelet, Olivier; Aristégui, Christophe; Mondain-Monval, Olivier

    2013-12-27

    An original approach is proposed here to reversibly tune Mie scattering resonances occurring in random media by means of external low induction magnetic fields. This approach is valid for both electromagnetic and acoustic waves. The experimental demonstration is supported by ultrasound experiments performed on emulsions made of fluorinated ferrofluid spherical droplets dispersed in a Bingham fluid. We show that the electromagnet-induced change of droplet shape into prolate spheroids, with a moderate aspect ratio of 2.5, drastically affects the effective properties of the disordered medium. Its effective acoustic attenuation coefficient is shown to vary by a factor of 5, by controlling both the flux density and orientation of the applied magnetic field. PMID:24483797

  8. Reciprocity and gyrotropism in magnetic resonance transduction

    NASA Astrophysics Data System (ADS)

    Tropp, James

    2006-12-01

    We give formulas for transduction in magnetic resonance—i.e., the appearance of an emf due to Larmor precession of spins—based upon the modified Lorentz reciprocity principle for gyrotropic (also called “nonreciprocal”) media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e., (H1x±iH1y) , where, e.g., for a single transceive antenna, the H ’s are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped

  9. Matched dipole probe for precise electron density measurements in magnetized and non-magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-09-01

    We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).

  10. Magnetic Resonance Force Microscopy Combined with Surface Topography

    NASA Astrophysics Data System (ADS)

    Tsuji, Shigenori; Yoshinari, Yohsuke

    2007-03-01

    In this presentation, we will show magnetic resonance force microscopy imaging combined with surface topography. The individual and combined images taken in the same coordinate are presented for extraction of the position, shapes and spin density distribution of target phantoms. This imaging technique is useful applied when the surface needs to be investigated in relation to the influence of a material buried below the surface. In our method, the surface topography was observed by the AFM with tapping mode. The spin density distribution was measured by the MRFM with the cyclic saturation technique. The AFM and MRFM experiments were made one after another by using the same experimental set-up, and their images were merged together afterwards. The sample consists of two kind of materials, one is DPPH containing unpaird spins and the other is a glass bead. DPPH particles with the size of 5˜8 micrometer and a 8.8 micrometer single bead were glued on a commercial cantilever.

  11. Effect of pulse slippage on beat wave THz generation in a rippled density magnetized plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Rajouria, Satish Kumar; K, Magesh Kumar K.

    2013-10-01

    Beat wave excitation of terahertz radiation by nonlinear mixing of two laser pulses in a ripple density magnetized plasma is investigated allowing for the effect of pulse slippage. The lasers' ponderomotive-force-induced electron drift couples with the density ripple to produce a nonlinear current that resonantly drives the terahertz at the beat frequency. Density ripple provides the phase matching while the magnetic field, transverse to the direction of laser propagation, provides a transverse component to current density. However, the group velocity mismatch between the lasers and the terahertz radiation leads to slippage of the latter behind the laser pulses leading to saturation of the terahertz amplitude.

  12. Nuclear magnetic resonance studies of lens transparency

    SciTech Connect

    Beaulieu, C.F.

    1989-01-01

    Transparency of normal lens cytoplasm and loss of transparency in cataract were studied by nuclear magnetic resonance (NMR) methods. Phosphorus ({sup 31}P) NMR spectroscopy was used to measure the {sup 31}P constituents and pH of calf lens cortical and nuclear homogenates and intact lenses as a function of time after lens enucleation and in opacification produced by calcium. Transparency was measured with laser spectroscopy. Despite complete loss of adenosine triphosphate (ATP) within 18 hrs of enucleation, the homogenates and lenses remained 100% transparent. Additions of calcium to ATP-depleted cortical homogenates produced opacification as well as concentration-dependent changes in inorganic phosphate, sugar phosphates, glycerol phosphorylcholine and pH. {sup 1}H relaxation measurements of lens water at 200 MHz proton Larmor frequency studied temperature-dependent phase separation of lens nuclear homogenates. Preliminary measurements of T{sub 1} and T{sub 2} with non-equilibrium temperature changes showed a change in the slope of the temperature dependence of T{sub 1} and T{sub 2} at the phase separation temperature. Subsequent studies with equilibrium temperature changes showed no effect of phase separation on T{sub 1} or T{sub 2}, consistent with the phase separation being a low-energy process. {sup 1}H nuclear magnetic relaxation dispersion (NMRD) studies (measurements of the magnetic field dependence of the water proton 1/T{sub 1} relaxation rates) were performed on (1) calf lens nuclear and cortical homogenates (2) chicken lens homogenates, (3) native and heat-denatured egg white and (4) pure proteins including bovine {gamma}-II crystallin bovine serum albumin (BSA) and myoglobin. The NMRD profiles of all samples exhibited decreases in 1/T{sub 1} with increasing magnetic field.

  13. [Clinical applications of magnetic resonance cholangiopancreatography].

    PubMed

    Soto, J A; Castrillón, G A

    2007-01-01

    Magnetic resonance cholangiopancreatography (MRCP) is the most important diagnostic alternative that has been developed in recent years for the evaluation of the biliary and pancreatic ducts. The advantages of this technique are: it does not use contrast media or ionizing radiation; it is noninvasive and complication free; and, the examination is relatively short (approximately 20 to 30 minutes). MRCP has high sensitivity and specificity for diagnosing biliary dilatation and for determining the site and cause of stenosis. Its diagnostic precision for biliary and pancreatic stones is similar to that of endoscopic retrograde cholangiopancreatography (ERCP). MRCP has replaced ERCP in biliary and pancreatic anatomic variants. In unsuccessful ERCP, MRCP is nearly the only diagnostic modality for the evaluation of the biliary tract. Other applications include primary sclerosing cholangitis, stenosis after liver transplantation, and the evaluation of bilioenteric anastomoses. This article reviews the clinical applications of MRCP in the evaluation of biliopancreatic diseases. PMID:18021667

  14. Magnetic resonance imaging in Leber's optic neuropathy.

    PubMed Central

    Kermode, A G; Moseley, I F; Kendall, B E; Miller, D H; MacManus, D G; McDonald, W I

    1989-01-01

    Thirteen males with Leber's optic neuropathy had magnetic resonance imaging (MRI) of the brain, and in eight the optic nerves were imaged using STIR (Short Time Inversion Recovery) sequences. All optic nerve scans were abnormal. In seven with bilateral visual loss four showed bilateral increased optic nerve signal and three unilateral increase. The involvement was of the mid and posterior intra-orbital sections over three 5 mm slices or more with sparing of the anterior portion. One patient with unilateral visual loss had increased signal only on the affected side. Brain MRI was normal, in marked contrast to the findings in clinically isolated optic neuritis in which multiple white matter lesions are seen in the majority. Images PMID:2732742

  15. Magnetic resonance imaging of optic nerve

    PubMed Central

    Gala, Foram

    2015-01-01

    Optic nerves are the second pair of cranial nerves and are unique as they represent an extension of the central nervous system. Apart from clinical and ophthalmoscopic evaluation, imaging, especially magnetic resonance imaging (MRI), plays an important role in the complete evaluation of optic nerve and the entire visual pathway. In this pictorial essay, the authors describe segmental anatomy of the optic nerve and review the imaging findings of various conditions affecting the optic nerves. MRI allows excellent depiction of the intricate anatomy of optic nerves due to its excellent soft tissue contrast without exposure to ionizing radiation, better delineation of the entire visual pathway, and accurate evaluation of associated intracranial pathologies. PMID:26752822

  16. Chest magnetic resonance imaging: a protocol suggestion*

    PubMed Central

    Hochhegger, Bruno; de Souza, Vinícius Valério Silveira; Marchiori, Edson; Irion, Klaus Loureiro; Souza Jr., Arthur Soares; Elias Junior, Jorge; Rodrigues, Rosana Souza; Barreto, Miriam Menna; Escuissato, Dante Luiz; Mançano, Alexandre Dias; Araujo Neto, César Augusto; Guimarães, Marcos Duarte; Nin, Carlos Schuler; Santos, Marcel Koenigkam; Silva, Jorge Luiz Pereira e

    2015-01-01

    In the recent years, with the development of ultrafast sequences, magnetic resonance imaging (MRI) has been established as a valuable diagnostic modality in body imaging. Because of improvements in speed and image quality, MRI is now ready for routine clinical use also in the study of pulmonary diseases. The main advantage of MRI of the lungs is its unique combination of morphological and functional assessment in a single imaging session. In this article, the authors review most technical aspects and suggest a protocol for performing chest MRI. The authors also describe the three major clinical indications for MRI of the lungs: staging of lung tumors; evaluation of pulmonary vascular diseases; and investigation of pulmonary abnormalities in patients who should not be exposed to radiation. PMID:26811555

  17. Magnetic resonance imaging of prostate cancer.

    PubMed

    Guneyli, Serkan; Erdem, Cemile Zuhal; Erdem, Lutfi Oktay

    2016-01-01

    Prostate cancer is one of the causes of cancer-related deaths. Multiparametric magnetic resonance imaging (MRI) provides the best soft tissue resolution and plays an important role in the management of prostate cancer patients. It is the recommended imaging modality for patients with prostate cancer, and it is clinically indicated for diagnosis, staging, tumor localization, detection of tumor aggressiveness, follow-up, and MRI-guided interventions. Multiparametric MRI includes T1- and high-resolution T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast-enhanced MRI. We evaluated MR images of patients with prostate cancer who underwent multiparametric endorectal MRI on a 3.0-T scanner and presented demonstrative images. PMID:27317204

  18. Magnetic resonance imaging of experimental cerebral oedema.

    PubMed Central

    Barnes, D; McDonald, W I; Tofts, P S; Johnson, G; Landon, D N

    1986-01-01

    Triethyl tin(TET)-induced cerebral oedema has been studied in cats by magnetic resonance imaging (MRI), and the findings correlated with the histology and fine structure of the cerebrum following perfusion-fixation. MRI is a sensitive technique for detecting cerebral oedema, and the distribution and severity of the changes correlate closely with the morphological abnormalities. The relaxation times, T1 and T2 increase progressively as the oedema develops, and the proportional increase in T2 is approximately twice that in T1. Analysis of the magnetisation decay curves reveals slowly-relaxing and rapidly-relaxing components which probably correspond to oedema fluid and intracellular water respectively. The image appearances taken in conjunction with relaxation data provide a basis for determining the nature of the oedema in vivo. Images PMID:3806109

  19. Magnetic resonance imaging of heterotaxis syndrome.

    PubMed

    Stoeckelhuber, Beate M; Eckey, Thomas; Buchholz, Michael; Kapsimalakou, Smaragda; Stoeckelhuber, Mechthild

    2008-12-20

    Failure to establish normal left-right body axis (LRA) formation during embryogenesis results in heterotaxis, a multi-malformation syndrome. We report on a 20-year-old young woman who presented to the emergency room with upper abdominal pain. On chest X-ray, dextrocardia was noted. Ultrasound was inconclusive. Barium studies demonstrated non-rotation of the intestine. Magnetic resonance imaging (MRI) of the abdomen confirmed heterotaxis with abnormal arrangement of abdominal organs and vasculature. This is the first radiographic description of LRA in MRI. It provides a unique contribution to the wide morphological variety of lateralization defects in a single examination within 15 min and without the risks of ionizing radiation. In addition, a literature overview over the genetic aspects, broad morphological spectrum, and possible therapeutic consequences is given. PMID:18835766

  20. Magnetic resonance imaging of pancreatitis: An update

    PubMed Central

    Manikkavasakar, Sriluxayini; AlObaidy, Mamdoh; Busireddy, Kiran K; Ramalho, Miguel; Nilmini, Viragi; Alagiyawanna, Madhavi; Semelka, Richard C

    2014-01-01

    Magnetic resonance (MR) imaging plays an important role in the diagnosis and staging of acute and chronic pancreatitis and may represent the best imaging technique in the setting of pancreatitis due to its unmatched soft tissue contrast resolution as well as non-ionizing nature and higher safety profile of intravascular contrast media, making it particularly valuable in radiosensitive populations such as pregnant patients, and patients with recurrent pancreatitis requiring multiple follow-up examinations. Additional advantages include the ability to detect early forms of chronic pancreatitis and to better differentiate adenocarcinoma from focal chronic pancreatitis. This review addresses new trends in clinical pancreatic MR imaging emphasizing its role in imaging all types of acute and chronic pancreatitis, pancreatitis complications and other important differential diagnoses that mimic pancreatitis. PMID:25356038

  1. Safety of magnetic resonance contrast media.

    PubMed

    Runge, V M

    2001-08-01

    Intravenous contrast media, specifically the gadolinium chelates, are well accepted for use in the clinical practice of magnetic resonance imaging. The gadolinium chelates are considered to be very safe and lack (in intravenous use) the nephrotoxicity found with iodinated contrast media. Minor adverse reactions, including nausea and hives, occur in a low percentage of cases. The four agents currently available in the United States cannot be differentiated on the basis of these adverse reactions. Severe anaphylactoid reactions are also known to occur with all agents, although these are uncommon. This review discusses the safety issues involved with intravenous administration of the gadolinium chelates and off-label use. The latter is common in clinical practice and permits broader application of these agents. PMID:11687717

  2. Molecular magnetic resonance imaging in cancer.

    PubMed

    Haris, Mohammad; Yadav, Santosh K; Rizwan, Arshi; Singh, Anup; Wang, Ena; Hariharan, Hari; Reddy, Ravinder; Marincola, Francesco M

    2015-01-01

    The ability to identify key biomolecules and molecular changes associated with cancer malignancy and the capacity to monitor the therapeutic outcome against these targets is critically important for cancer treatment. Recent developments in molecular imaging based on magnetic resonance (MR) techniques have provided researchers and clinicians with new tools to improve most facets of cancer care. Molecular imaging is broadly described as imaging techniques used to detect molecular signature at the cellular and gene expression levels. This article reviews both established and emerging molecular MR techniques in oncology and discusses the potential of these techniques in improving the clinical cancer care. It also discusses how molecular MR, in conjunction with other structural and functional MR imaging techniques, paves the way for developing tailored treatment strategies to enhance cancer care. PMID:26394751

  3. Fetal Cerebral Magnetic Resonance Imaging Beyond Morphology.

    PubMed

    Jakab, András; Pogledic, Ivana; Schwartz, Ernst; Gruber, Gerlinde; Mitter, Christian; Brugger, Peter C; Langs, Georg; Schöpf, Veronika; Kasprian, Gregor; Prayer, Daniela

    2015-12-01

    The recent technological advancement of fast magnetic resonance imaging (MRI) sequences allowed the inclusion of diffusion tensor imaging, functional MRI, and proton MR spectroscopy in prenatal imaging protocols. These methods provide information beyond morphology and hold the key to improving several fields of human neuroscience and clinical diagnostics. Our review introduces the fundamental works that enabled these imaging techniques, and also highlights the most recent contributions to this emerging field of prenatal diagnostics, such as the structural and functional connectomic approach. We introduce the advanced image processing approaches that are extensively used to tackle fetal or maternal movement-related image artifacts, and which are necessary for the optimal interpretation of such imaging data. PMID:26614130

  4. [Prostate biopsy under magnetic resonance imaging guidance].

    PubMed

    Kuplevatskiy, V I; CherkashiN, M A; Roshchin, D A; Berezina, N A; Vorob'ev, N A

    2016-01-01

    Prostate cancer (PC) is one of the most important problems in modern oncology. According to statistical data, PC ranks second in the cancer morbidity structure in the Russian Federation and developed countries and its prevalence has been progressively increasing over the past decade. A need for early diagnosis and maximally accurate morphological verification of the diagnosis in difficult clinical cases (inconvenient tumor location for standard transrectal biopsy; gland scarring changes concurrent with prostatitis and hemorrhage; threshold values of prostate-specific antigen with unclear changes in its doubling per unit time; suspicion of biochemical recurrence or clinical tumor progression after special treatment) leads to revised diagnostic algorithms and clinically introduced new high-tech invasive diagnostic methods. This paper gives the first analysis of literature data on Russian practice using one of the new methods to verify prostate cancer (transrectal prostate cancer under magnetic resonance imaging (MRI) guidance). The have sought the 1995-2015 data in the MEDLINE and Pubmed. PMID:27192773

  5. Magnetic Resonance Imaging for Perianal Fistula.

    PubMed

    Tolan, Damian J M

    2016-08-01

    Perianal fistulas and other inflammatory diseases of the anus and perianal soft tissues are a cause of substantial morbidity, and are a major part of the practice of any colorectal surgeon. Magnetic resonance imaging (MRI) has a key role in the assessment of patients for the extent of fistulizing Crohn disease, complications related to fistulas, and to assist in confirming the diagnosis or proposing an alternative. Technique is critical and in particular, the selection of sequences for diagnosis and characterization of abnormalities with the main choices being between standard anatomical sequences (T1 or T2), assessing for edema (FS T2 or STIR), assessing abnormal contrast enhancement (FS T1), and assessing for abnormal diffusion or a combination of these. Guidance on MRI sequence selection, classification of fistulas, the current guidance on the role of MRI in assessing patients, and advice on how to provide useful structured reports, as well as how to detect complications of perianal sepsis are included. PMID:27342895

  6. Two-dimensional nuclear magnetic resonance petrophysics.

    PubMed

    Sun, Boqin; Dunn, Keh-Jim

    2005-02-01

    Two-dimensional nuclear magnetic resonance (2D NMR) opens a wide area for exploration in petrophysics and has significant impact to petroleum logging technology. When there are multiple fluids with different diffusion coefficients saturated in a porous medium, this information can be extracted and clearly delineated from CPMG measurements of such a system either using regular pulsing sequences or modified two window sequences. The 2D NMR plot with independent variables of T2 relaxation time and diffusion coefficient allows clear separation of oil and water signals in the rocks. This 2D concept can be extended to general studies of fluid-saturated porous media involving other combinations of two or more independent variables, such as chemical shift and T1/T2 relaxation time (reflecting pore size), proton population and diffusion contrast, etc. PMID:15833623

  7. Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1993-01-01

    The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of the research activity at the Sir Isaac Newton Conference in St. Petersburg, Russia, and the second Day of Discovery Conference, focusing on economic recovery in West Virginia. An active antenna concept utilizing a signal feedback principle similar to regenerative receivers used in early radio was studied. The device has potential for ELF research and other commercial applications for improved signal reception. Finally, work continues to progress on the development of a prototype monitoring station. Signal monitoring, data display, and data storage are major areas of activity. In addition, we plan to continue our dissemination of research activity through presentations at seminars and other universities.

  8. The magnetic resonance imaging-linac system.

    PubMed

    Lagendijk, Jan J W; Raaymakers, Bas W; van Vulpen, Marco

    2014-07-01

    The current image-guided radiotherapy systems are suboptimal in the esophagus, pancreas, kidney, rectum, lymph node, etc. These locations in the body are not easily accessible for fiducials and cannot be visualized sufficiently on cone-beam computed tomographies, making daily patient set-up prone to geometrical uncertainties and hinder dose optimization. Additional interfraction and intrafraction uncertainties for those locations arise from motion with breathing and organ filling. To allow real-time imaging of all patient tumor locations at the actual treatment position a fully integrated 1.5-T, diagnostic quality, magnetic resonance imaging with a 6-MV linear accelerator is presented. This system must enable detailed dose painting at all body locations. PMID:24931095

  9. In vivo nuclear magnetic resonance imaging

    NASA Technical Reports Server (NTRS)

    Leblanc, A.; Evans, H.; Bryan, R. N.; Johnson, P.; Schonfeld, E.; Jhingran, S. G.

    1984-01-01

    A number of physiological changes have been demonstrated in bone, muscle and blood after exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long duration space missions is an important NASA goal. The advent of tomographic nuclear magnetic resonance imaging (NMR or MRI) gives NASA a way to greatly extend early studies of this phenomena in ways not previously possible; NMR is also noninvasive and safe. NMR provides both superb anatomical images for volume assessments of individual organs and quantification of chemical/physical changes induced in the examined tissues. The feasibility of NMR as a tool for human physiological research as it is affected by microgravity is demonstrated. The animal studies employed the rear limb suspended rat as a model of mucle atrophy that results from microgravity. And bedrest of normal male subjects was used to simulate the effects of microgravity on bone and muscle.

  10. Nuclear magnetic resonance imaging in medicine

    PubMed Central

    McKinstry, C S

    1986-01-01

    Using the technique of nuclear magnetic resonance (NMR, MR, MRI), the first images displaying pathology in humans were published in 1980.1 Since then, there has been a rapid extension in the use of the technique, with an estimated 225 machines in use in the USA at the end of 1985.2 Considerable enthusiasm has been expressed for this new imaging technique,3 although awareness of its high cost in the present economic climate has led to reservations being expressed in other quarters.2 The aim of this article is to give an outline of the present state of NMR, and indicate some possible future developments. ImagesFig 1Fig 2Fig 3(a)Fig 3 (b)Fig 4Fig 5Fig 6Fig 7 (a)Fig 7 (b)Fig 8Fig 9Fig 10 PMID:3811023

  11. [Nuclear magnetic resonance in ischemic cardiopathy].

    PubMed

    Meave, Aloha

    2007-01-01

    Nuclear magnetic resonance is the "gold standard" technique to quantify the ventricular volume, the ejection fraction, and the myocardial mass. In patients suffering from ischemic cardiopathy, the ejection fraction is the most important prognostic parameter, even above from lessoned arteries index. An adequate diagnose between a non-viable and a viable myocardium is of great importance in the therapeutic approach for ischemic cardiopathy. By administrating a paramagnetic contrast media named gadolinium, fist pass and late-reinforcement techniques, are applied. With these, it is possible to evaluate the perfusion as well as necrotic areas. In order to identify sub-endocardium ischemia, drugs such as adenosine and dipiridamol, are employed as vasodilators. This technique allows the definition of reinforcement extension, being sub-endocardiac, which is an ailment which affects 50% of the myocardium depth, or even, transmural compromise. PMID:18938717

  12. Stem cell labeling for magnetic resonance imaging.

    PubMed

    Himmelreich, Uwe; Hoehn, Mathias

    2008-01-01

    In vivo applications of cells for the monitoring of their cell dynamics increasingly use non-invasive magnetic resonance imaging. This imaging modality allows in particular to follow the migrational activity of stem cells intended for cell therapy strategies. All these approaches require the prior labeling of the cells under investigation for excellent contrast against the host tissue background in the imaging modality. The present review discusses the various routes of cell labeling and describes the potential to observe both cell localization and their cell-specific function in vivo. Possibilities for labeling strategies, pros and cons of various contrast agents are pointed out while potential ambiguities or problems of labeling strategies are emphasized. PMID:18465447

  13. Nuclear magnetic resonance imaging of the spine

    SciTech Connect

    Modic, M.T.; Weinstein, M.A.; Pavlicek, W.; Starnes, D.L.; Duchesneau, P.M.; Boumphrey, F.; Hardy, R.J. Jr.

    1984-01-01

    Forty subjects were examined to determine the accuracy and clinical usefulness of nuclear magnetic resonance (NMR) examination of the spine. The NMR images were compared with plain radiographs, high-resolution computed tomograms, and myelograms. The study included 15 patients with normal spinal cord anatomy and 25 patients whose pathological conditions included canal stenosis, herniated discs, metastatic tumors, primary cord tumor, trauma, Chiari malformations, syringomyelia, and developmental disorders. Saturation recovery images were best in differentiating between soft tissue and cerebrospinal fluid. NMR was excellent for the evaluation of the foramen magnum region and is presently the modality of choice for the diagnosis of syringomyelia and Chiari malformation. NMR was accurate in diagnosing spinal cord trauma and spinal canal block.

  14. Chronic subdural hematoma: demonstration by magnetic resonance

    SciTech Connect

    Sipponen, J.T.; Sepponen, R.E.; Sivula, A.

    1984-01-01

    The ability of magnetic resonance (MR) to identify intracranial hematomas was tested in five patients with clinical and computed tomographic signs of chronic subdural hematoma. The extracerebral collections were displayed as a zone of bright intensity using the T1-weighted inversion recovery (IR 1500/400) sequence, reflecting the lesions' short T1 relaxation times. The collections also showed high intensity using the spin echo (SE) sequence, with a longer delay of 100ms and 160ms, reflecting the long T2 relaxation time. The spin echo sequence with a repetition time of 500ms and an echo delay of 160ms (SE 500/160) almost effaced other structures in the image, thus increasing the specificity of this pulse scheme for detection of chronic blood collections. Although in two of the five patients the subdural hematomas were in the isodense CT phase, all were easily visualized with MR.

  15. Magnetic Resonance Imaging of the Knee

    PubMed Central

    Hash, Thomas W.

    2013-01-01

    Context: Magnetic resonance imaging (MRI) affords high-resolution visualization of the soft tissue structures (menisci, ligaments, cartilage, etc) and bone marrow of the knee. Evidence Acquisition: Pertinent clinical and research articles in the orthopaedic and radiology literature over the past 30 years using PubMed. Results: Ligament tears can be accurately assessed with MRI, but distinguishing partial tears from ruptures of the anterior cruciate ligament (ACL) can be challenging. Determining the extent of a partial tear is often extremely difficult to accurately assess. The status of the posterolateral corner structures, menisci, and cartilage can be accurately evaluated, although limitations in the evaluation of certain structures exist. Patellofemoral joint, marrow, tibiofibular joint, and synovial pathology can supplement physical examination findings and provide definitive diagnosis. Conclusions: MRI provides an accurate noninvasive assessment of knee pathology. PMID:24381701

  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. Magnetic resonance imaging of pancreatitis: an update.

    PubMed

    Manikkavasakar, Sriluxayini; AlObaidy, Mamdoh; Busireddy, Kiran K; Ramalho, Miguel; Nilmini, Viragi; Alagiyawanna, Madhavi; Semelka, Richard C

    2014-10-28

    Magnetic resonance (MR) imaging plays an important role in the diagnosis and staging of acute and chronic pancreatitis and may represent the best imaging technique in the setting of pancreatitis due to its unmatched soft tissue contrast resolution as well as non-ionizing nature and higher safety profile of intravascular contrast media, making it particularly valuable in radiosensitive populations such as pregnant patients, and patients with recurrent pancreatitis requiring multiple follow-up examinations. Additional advantages include the ability to detect early forms of chronic pancreatitis and to better differentiate adenocarcinoma from focal chronic pancreatitis. This review addresses new trends in clinical pancreatic MR imaging emphasizing its role in imaging all types of acute and chronic pancreatitis, pancreatitis complications and other important differential diagnoses that mimic pancreatitis. PMID:25356038

  18. Magnetic resonance imaging after exposure to microgravity

    NASA Technical Reports Server (NTRS)

    Leblanc, Adrian

    1993-01-01

    A number of physiological changes were demonstrated in bone, muscle, and blood from exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long-duration space missions is an important NASA goal. Historically, NASA has had to rely on tape measures, x-ray, and metabolic balance studies with collection of excreta and blood specimens to obtain this information. The development of magnetic resonance imaging (MRI) offers the possibility of greatly extending these early studies in ways not previously possible; MRI is also non-invasive and safe; i.e., no radiation exposure. MRI provides both superb anatomical images for volume measurements of individual structures and quantification of chemical/physical changes induced in the examined tissues. This investigation will apply MRI technology to measure muscle, intervertebral disc, and bone marrow changes resulting from exposure to microgravity.

  19. Geochemical Controls on Nuclear Magnetic Resonance Measurements

    SciTech Connect

    Knight, Rosemary; Prasad, Manika; Keating, Kristina

    2003-11-11

    OAK-B135 Our research objectives are to determine, through an extensive set of laboratory experiments, the effect of the specific mineralogic form of iron and the effect of the distribution of iron on proton nuclear magnetic resonance (NMR) relaxation mechanisms. In the first nine months of this project, we have refined the experimental procedures to be used in the acquisition of the laboratory NMR data; have ordered, and conducted preliminary measurements on, the sand samples to be used in the experimental work; and have revised and completed the theoretical model to use in this project. Over the next year, our focus will be on completing the first phase of the experimental work where the form and distribution of the iron in the sands in varied.

  20. Could magnetic resonance provide in vivo histology?

    PubMed Central

    Dominietto, Marco; Rudin, Markus

    2014-01-01

    The diagnosis of a suspected tumor lesion faces two basic problems: detection and identification of the specific type of tumor. Radiological techniques are commonly used for the detection and localization of solid tumors. Prerequisite is a high intrinsic or enhanced contrast between normal and neoplastic tissue. Identification of the tumor type is still based on histological analysis. The result depends critically on the sampling sites, which given the inherent heterogeneity of tumors, constitutes a major limitation. Non-invasive in vivo imaging might overcome this limitation providing comprehensive three-dimensional morphological, physiological, and metabolic information as well as the possibility for longitudinal studies. In this context, magnetic resonance based techniques are quite attractive since offer at the same time high spatial resolution, unique soft tissue contrast, good temporal resolution to study dynamic processes and high chemical specificity. The goal of this paper is to review the role of magnetic resonance techniques in characterizing tumor tissue in vivo both at morphological and physiological levels. The first part of this review covers methods, which provide information on specific aspects of tumor phenotypes, considered as indicators of malignancy. These comprise measurements of the inflammatory status, neo-vascular physiology, acidosis, tumor oxygenation, and metabolism together with tissue morphology. Even if the spatial resolution is not sufficient to characterize the tumor phenotype at a cellular level, this multiparametric information might potentially be used for classification of tumors. The second part discusses mathematical tools, which allow characterizing tissue based on the acquired three-dimensional data set. In particular, methods addressing tumor heterogeneity will be highlighted. Finally, we address the potential and limitation of using MRI as a tool to provide in vivo tissue characterization. PMID:24454320

  1. Serial Magnetic Resonance Imaging in Active Surveillance of Prostate Cancer: Incremental Value

    PubMed Central

    Felker, Ely R.; Wu, Jason; Natarajan, Shyam; Margolis, Daniel J.; Raman, Steven S.; Huang, Jiaoti; Dorey, Fred; Marks, Leonard S.

    2016-01-01

    Purpose We assessed whether changes in serial multiparametric magnetic resonance imaging can help predict the pathological progression of prostate cancer in men on active surveillance. Materials and Methods A retrospective cohort study was conducted of 49 consecutive men with Gleason 6 prostate cancer who underwent multi-parametric magnetic resonance imaging at baseline and again more than 6 months later, each followed by a targeted prostate biopsy, between January 2011 and May 2015. We evaluated whether progression on multiparametric magnetic resonance imaging (an increase in index lesion suspicion score, increase in index lesion volume or decrease in index lesion apparent diffusion coefficient) could predict pathological progression (Gleason 3 + 4 or greater on subsequent biopsy, in systematic or targeted cores). Diagnostic performance of multiparametric magnetic resonance imaging was determined with and without clinical data using a binary logistic regression model. Results The mean interval between baseline and followup multiparametric magnetic resonance imaging was 28.3 months (range 11 to 43). Pathological progression occurred in 19 patients (39%). The sensitivity, specificity, positive predictive value and negative predictive value of multiparametric magnetic resonance imaging was 37%, 90%, 69% and 70%, respectively. Area under the receiver operating characteristic curve was 0.63. A logistic regression model using clinical information (maximum cancer core length greater than 3 mm on baseline biopsy or a prostate specific antigen density greater than 0.15 ng/ml2 at followup biopsy) had an AUC of 0.87 for predicting pathological progression. The addition of serial multiparametric magnetic resonance imaging data significantly improved the AUC to 0.91 (p = 0.044). Conclusions Serial multiparametric magnetic resonance imaging adds incremental value to prostate specific antigen density and baseline cancer core length for predicting Gleason 6 upgrading in men on

  2. Computed tomography and magnetic resonance findings in lipoid pneumonia.

    PubMed Central

    Bréchot, J M; Buy, J N; Laaban, J P; Rochemaure, J

    1991-01-01

    A case of exogenous lipoid pneumonia was documented by computed tomography and magnetic resonance imaging. Although strongly suggesting the presence of fat on T1 weighted images, magnetic resonance does not produce images specific for this condition. Computed tomography is the best imaging modality for its diagnosis. Images PMID:1750024

  3. 21 CFR 892.1000 - Magnetic resonance diagnostic device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Magnetic resonance diagnostic device. 892.1000 Section 892.1000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance...

  4. 21 CFR 892.1000 - Magnetic resonance diagnostic device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Magnetic resonance diagnostic device. 892.1000 Section 892.1000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance...

  5. Two density peaks in low magnetic field helicon plasma

    SciTech Connect

    Wang, Y.; Zhao, G.; Ouyang, J. T. E-mail: lppmchenqiang@hotmail.com; Liu, Z. W.; Chen, Q. E-mail: lppmchenqiang@hotmail.com

    2015-09-15

    In this paper, we report two density peaks in argon helicon plasma under an axial magnetic field from 0 G to 250 G with Boswell-type antenna driven by radio frequency (RF) power of 13.56 MHz. The first peak locates at 40–55 G and the second one at 110–165 G, as the RF power is sustainably increased from 100 W to 250 W at Ar pressure of 0.35 Pa. The absorbed power of two peaks shows a linear relationship with the magnetic field. End views of the discharge taken by intensified charge coupled device reveal that, when the first peak appeared, the discharge luminance moves to the edge of the tube as the magnetic field increases. For the second peak, the strong discharge area is centered at the two antenna legs after the magnetic field reaches a threshold value. Comparing with the simulation, we suggest that the efficient power absorption of two peaks at which the efficient power absorption mainly appears in the near-antenna region is due to the mode conversion in bounded non-uniform helicon plasma. The two low-field peaks are caused, to some extent, by the excitation of Trivelpiece-Gould wave through non-resonance conversion.

  6. Compact electrically detected magnetic resonance setup

    SciTech Connect

    Eckardt, Michael Harneit, Wolfgang; Behrends, Jan; Münter, Detlef

    2015-04-15

    Electrically detected magnetic resonance (EDMR) is a commonly used technique for the study of spin-dependent transport processes in semiconductor materials and electro-optical devices. Here, we present the design and implementation of a compact setup to measure EDMR, which is based on a commercially available benchtop electron paramagnetic resonance (EPR) spectrometer. The electrical detection part uses mostly off-the-shelf electrical components and is thus highly customizable. We present a characterization and calibration procedure for the instrument that allowed us to quantitatively reproduce results obtained on a silicon-based reference sample with a “large-scale” state-of-the-art instrument. This shows that EDMR can be used in novel contexts relevant for semiconductor device fabrication like clean room environments and even glove boxes. As an application example, we present data on a class of environment-sensitive objects new to EDMR, semiconducting organic microcrystals, and discuss similarities and differences to data obtained for thin-film devices of the same molecule.

  7. Magnetic resonance characterization of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Fanciulli, Marco; Belli, Matteo; Vellei, Antonio; Canevali, Carmen; Rotta, Davide; Paleari, Stefano; Basini, Martina

    2012-02-01

    Silicon nanowires (SiNWs) have been extensively investigated in the last decades. The interest in these nanostructures stems from both fundamental and applied research motivations. The functional properties of one- and zero-dimensional silicon structures are significantly different, at least below a certain critical dimension, from those well known in the bulk. The key and peculiar functional properties of SiNWs find applications in nanoelectronics, classical and quantum information processing and storage, optoelectronics, photovoltaics, thermoelectric, battery technology, nano-biotechnology, and neuroelectronics. We report our work on the characterization by continuous wave (CW) and pulse electron spin resonance (CW, FT-EPR) and electrically detected magnetic resonance (EDMR) measurements of silicon nanowires (SiNWs) produced by different top-down processes. SiNWs were fabricated starting from SOI wafers using standard e-beam lithography and anisotropic wet etching or by metal-assisted chemical etching. Further oxidation was used to reduce the wire cross section. Different EDMR implementations were used to address the electronic wave function of donors (P, As) and to characterize point defects at the SiNWs/SiO2 interface.

  8. Compact electrically detected magnetic resonance setup

    NASA Astrophysics Data System (ADS)

    Eckardt, Michael; Behrends, Jan; Münter, Detlef; Harneit, Wolfgang

    2015-04-01

    Electrically detected magnetic resonance (EDMR) is a commonly used technique for the study of spin-dependent transport processes in semiconductor materials and electro-optical devices. Here, we present the design and implementation of a compact setup to measure EDMR, which is based on a commercially available benchtop electron paramagnetic resonance (EPR) spectrometer. The electrical detection part uses mostly off-the-shelf electrical components and is thus highly customizable. We present a characterization and calibration procedure for the instrument that allowed us to quantitatively reproduce results obtained on a silicon-based reference sample with a "large-scale" state-of-the-art instrument. This shows that EDMR can be used in novel contexts relevant for semiconductor device fabrication like clean room environments and even glove boxes. As an application example, we present data on a class of environment-sensitive objects new to EDMR, semiconducting organic microcrystals, and discuss similarities and differences to data obtained for thin-film devices of the same molecule.

  9. Rotating-frame gradient fields for magnetic resonance imaging and nuclear magnetic resonance in low fields

    DOEpatents

    Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki

    2014-01-21

    A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.

  10. The future of magnetic resonance-based techniques in neurology.

    PubMed

    2001-01-01

    Magnetic resonance techniques have become increasingly important in neurology for defining: 1. brain, spinal cord and peripheral nerve or muscle structure; 2. pathological changes in tissue structures and properties; and 3. dynamic patterns of functional activation of the brain. New applications have been driven in part by advances in hardware, particularly improvements in magnet and gradient coil design. New imaging strategies allow novel approaches to contrast with, for example, diffusion imaging, magnetization transfer imaging, perfusion imaging and functional magnetic resonance imaging. In parallel with developments in hardware and image acquisition have been new approaches to image analysis. These have allowed quantitative descriptions of the image changes to be used for a precise, non-invasive definition of pathology. With the increasing capabilities and specificity of magnetic resonance techniques it is becoming more important that the neurologist is intimately involved in both the selection of magnetic resonance studies for patients and their interpretation. There is a need for considerably improved access to magnetic resonance technology, particularly in the acute or intensive care ward and in the neurosurgical theatre. This report illustrates several key developments. The task force concludes that magnetic resonance imaging is a major clinical tool of growing significance and offers recommendations for maximizing the potential future for magnetic resonance techniques in neurology. PMID:11509077

  11. Plasma-induced magnetic responses during nonlinear dynamics of magnetic islands due to resonant magnetic perturbations

    SciTech Connect

    Nishimura, Seiya

    2014-12-15

    Resonant magnetic perturbations (RMPs) produce magnetic islands in toroidal plasmas. Self-healing (annihilation) of RMP-induced magnetic islands has been observed in helical systems, where a possible mechanism of the self-healing is shielding of RMP penetration by plasma flows, which is well known in tokamaks. Thus, fundamental physics of RMP shielding is commonly investigated in both tokamaks and helical systems. In order to check this mechanism, detailed informations of magnetic island phases are necessary. In experiments, measurement of radial magnetic responses is relatively easy. In this study, based on a theoretical model of rotating magnetic islands, behavior of radial magnetic fields during the self-healing is investigated. It is confirmed that flips of radial magnetic fields are typically observed during the self-healing. Such behavior of radial magnetic responses is also observed in LHD experiments.

  12. Cardiac imaging using gated magnetic resonance

    SciTech Connect

    Lanzer, P.; Botvinick, E.H.; Schiller, N.B.

    1984-01-01

    To overcome the limitations of magnetic resonance (MR) cardiac imaging using nongated data acquisition, three methods for acquiring a gating signal, which could be applied in the presence of a magnetic field, were tested; an air-filled plethysmograph, a laser-Doppler capillary perfusion flowmeter, and an electrocardiographic gating device. The gating signal was used for timing of MR imaging sequences (IS). Application of each gating method yielded significant improvements in structural MR image resolution of the beating heart, although with both plethysmography and laser-Doppler velocimetry it was difficult to obtain cardiac images from the early portion of the cardiac cycle due to an intrinsic delay between the ECG R wave and peripheral detection of the gating signal. Variations in the temporal relationship between the R wave and plethysmographic and laser-Doppler signals produced inconsistencies in the timing of IS. Since the ECG signal is virtually free of these problems, the preferable gating technique is IS synchronization with an electrocardiogram. The gated images acquired with this method provide sharp definition of internal cardiac morphology and can be temporarily referenced to end diastole and end systole or intermediate points.

  13. Multi-dimensionally encoded magnetic resonance imaging

    PubMed Central

    Lin, Fa-Hsuan

    2013-01-01

    Magnetic resonance imaging typically achieves spatial encoding by measuring the projection of a q-dimensional object over q-dimensional spatial bases created by linear spatial encoding magnetic fields (SEMs). Recently, imaging strategies using nonlinear SEMs have demonstrated potential advantages for reconstructing images with higher spatiotemporal resolution and reducing peripheral nerve stimulation. In practice, nonlinear SEMs and linear SEMs can be used jointly to further improve the image reconstruction performance. Here we propose the multi-dimensionally encoded (MDE) MRI to map a q-dimensional object onto a p-dimensional encoding space where p > q. MDE MRI is a theoretical framework linking imaging strategies using linear and nonlinear SEMs. Using a system of eight surface SEM coils with an eight-channel RF coil array, we demonstrate the five-dimensional MDE MRI for a two-dimensional object as a further generalization of PatLoc imaging and O-space imaging. We also present a method of optimizing spatial bases in MDE MRI. Results show that MDE MRI with a higher dimensional encoding space can reconstruct images more efficiently and with a smaller reconstruction error when the k-space sampling distribution and the number of samples are controlled. PMID:22926830

  14. 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

  15. Microrobotic navigable entities for Magnetic Resonance Targeting.

    PubMed

    Martel, Sylvain

    2010-01-01

    Magnetic Resonance Targeting (MRT) uses MRI for gathering tracking data to determine the position of microscale entities with the goal of guiding them towards a specific target in the body accessible through the vascular network. At full capabilities, a MRT platform designed to treat a human would consist of a clinical MRI scanner running special algorithms and upgraded to provide propulsion gradient up to approximately 400mT/m to enable entities as small as a few tens of micrometers in diameter and containing magnetic nanoparticles (MNP) to be steered at vessel bifurcations based on tracking information. Indeed, using a clinical MRI system, we showed that such single entity with a diameter as small as 15microm is detectable in gradient-echo scans. Among many potential interventions, targeted cancer therapy is a good initial application for such new microrobotic approach since secondary toxicity for the patient could be reduced while increasing therapeutic efficacy using lower dosages. Although many types of such entities are needed to provide a larger set of tools, here, only three initial types designed with different functionalities and for different types of cancer are briefly described. Initially designed for targeted chemo-embolization of liver tumors, the first type known as Therapeutic Magnetic Micro-Carriers (TMMC) consists in its present form of approximately 50 microm PLGA microparticles containing therapeutics and approximately 180 nm FeCo MNP. For the second type, MNP are not only used for propulsion and tracking, but also actuation based on a local elevation of the temperature. In its simplest form, it consists of approxiamtely 20 nm MNP embedded in a thermo-sensitive hydrogel known as PNIPA, allowing additional functionalities such as computer triggered drug release and targeted hyperthermia. The third type initially considered to target colorectal tumors, consists of 1-2 microm MR-trackable and controllable MC-1 Magnetotactic Bacteria (MTB) with

  16. Overhauser-enhanced magnetic resonance elastography.

    PubMed

    Salameh, Najat; Sarracanie, Mathieu; Armstrong, Brandon D; Rosen, Matthew S; Comment, Arnaud

    2016-05-01

    Magnetic resonance elastography (MRE) is a powerful technique to assess the mechanical properties of living tissue. However, it suffers from reduced sensitivity in regions with short T2 and T2 * such as in tissue with high concentrations of paramagnetic iron, or in regions surrounding implanted devices. In this work, we exploit the longer T2 * attainable at ultra-low magnetic fields in combination with Overhauser dynamic nuclear polarization (DNP) to enable rapid MRE at 0.0065 T. A 3D balanced steady-state free precession based MRE sequence with undersampling and fractional encoding was implemented on a 0.0065 T MRI scanner. A custom-built RF coil for DNP and a programmable vibration system for elastography were developed. Displacement fields and stiffness maps were reconstructed from data recorded in a polyvinyl alcohol gel phantom loaded with stable nitroxide radicals. A DNP enhancement of 25 was achieved during the MRE sequence, allowing the acquisition of 3D Overhauser-enhanced MRE (OMRE) images with (1.5 × 2.7 × 9) mm(3) resolution over eight temporal steps and 11 slices in 6 minutes. In conclusion, OMRE at ultra-low magnetic field can be used to detect mechanical waves over short acquisition times. This new modality shows promise to broaden the scope of conventional MRE applications, and may extend the utility of low-cost, portable MRI systems to detect elasticity changes in patients with implanted devices or iron overload. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26915977

  17. Effects of Finite Density Fluctuations and of the Upper Hybrid Resonance on O-X Correlation Reflectometry

    SciTech Connect

    Kramer, G.J.; Nazikian, R.; Valeo, E.

    2001-02-10

    The correlation between O-mode and X-mode reflectometer signals is studied with a 1-D reflectometer model taking into account the influence of finite density fluctuation levels and the upper hybrid resonance. It is found that a high level of O-X correlation can only be achieved for sufficiently small density fluctuation levels (typically much less than 1%) or very low magnetic field strengths. The influence of the upper hybrid resonance on the O-X correlation was found to also degrade the correlation between the O and X mode signals for very low magnetic field strengths or for very short density scale lengths. The extrapolation of these results to reactor-scale parameters indicates that the magnetic field strength can reliably be measured in the core plasma provided the density fluctuation level is typically much less than 1%.

  18. Unconventional nuclear magnetic resonance techniques using nanostructured diamond surfaces

    NASA Astrophysics Data System (ADS)

    Acosta, Victor; Jarmola, Andrey; Budker, Dmitry; Santori, Charles; Huang, Zhihong; Beausoleil, Raymond

    2014-03-01

    Nuclear magnetic resonance (NMR) technologies rely on obtaining high nuclear magnetization, motivating low operating temperatures and high magnetic fields. Dynamic nuclear polarization (DNP) techniques traditionally require another superconducting magnet and THz optics. We seek to use chip-scale devices to polarize nuclei in liquids at room temperature. The technique relies on optical pumping of nitrogen-vacancy (NV) centers and subsequent transfer of polarization to nuclei via hyperfine interaction, spin diffusion, and heteronuclear polarization transfer. We expect efficient polarization transfer will be realized by maximizing the diamond surface area. We have fabricated densely-packed (50 % packing fraction), high-aspect-ratio (10+) nanopillars over mm2 regions of the diamond surface. Pillars designed to have a few-hundred-nanometer diameter act as optical antennas, reducing saturation intensity. We also report progress in using nanopillar arrays as sensitive optical detectors of nano-scale NMR by measuring NV center Zeeman shifts produced by nearby external nuclei. The enhanced surface area increases the effective density of NV centers which couple to external nuclei. Combining these techniques may enable, e.g., identification of trace analytes and molecular imaging.

  19. Control of Transport-Barrier Relaxations by Resonant Magnetic Perturbations

    SciTech Connect

    Leconte, M.; Beyer, P.; Benkadda, S.

    2009-01-30

    Transport-barrier relaxation oscillations in the presence of resonant magnetic perturbations are investigated using three-dimensional global fluid turbulence simulations from first principles at the edge of a tokamak. It is shown that resonant magnetic perturbations have a stabilizing effect on these relaxation oscillations and that this effect is due mainly to a modification of the pressure profile linked to the presence of both residual magnetic island chains and a stochastic layer.

  20. Linear constraint minimum variance beamformer functional magnetic resonance inverse imaging

    PubMed Central

    Lin, Fa-Hsuan; Witzel, Thomas; Zeffiro, Thomas A.; Belliveau, John W.

    2011-01-01

    Accurate estimation of the timing of neural activity is required to fully model the information flow among functionally specialized regions whose joint activity underlies perception, cognition and action. Attempts to detect the fine temporal structure of task-related activity would benefit from functional imaging methods allowing higher sampling rates. Spatial filtering techniques have been used in magnetoencephalography source imaging applications. In this work, we use the linear constraint minimal variance (LCMV) beamformer localization method to reconstruct single-shot volumetric functional magnetic resonance imaging (fMRI) data using signals acquired simultaneously from all channels of a high density radio-frequency (RF) coil array. The LCMV beamformer method generalizes the existing volumetric magnetic resonance inverse imaging (InI) technique, achieving higher detection sensitivity while maintaining whole-brain spatial coverage and 100 ms temporal resolution. In this paper, we begin by introducing the LCMV reconstruction formulation and then quantitatively assess its performance using both simulated and empirical data. To demonstrate the sensitivity and inter-subject reliability of volumetric LCMV InI, we employ an event-related design to probe the spatial and temporal properties of task-related hemodynamic signal modulations in primary visual cortex. Compared to minimum-norm estimate (MNE) reconstructions, LCMV offers better localization accuracy and superior detection sensitivity. Robust results from both single subject and group analyses demonstrate the excellent sensitivity and specificity of volumetric InI in detecting the spatial and temporal structure of task-related brain activity. PMID:18672071

  1. Comparative mouse brain tractography of diffusion magnetic resonance imaging

    PubMed Central

    Moldrich, Randal X.; Pannek, Kerstin; Hoch, Renee; Rubenstein, John L.; Kurniawan, Nyoman D.; Richards, Linda J.

    2010-01-01

    Diffusion magnetic resonance imaging (dMRI) tractography can be employed to simultaneously analyse three-dimensional white matter tracts in the brain. Numerous methods have been proposed to model diffusion-weighted magnetic resonance data for tractography, and we have explored the functionality of some of these for studying white and grey matter pathways in ex vivo mouse brain. Using various deterministic and probabilistic algorithms across a range of regions of interest we found that probabilistic tractography provides a more robust means of visualizing both white and grey matter pathways than deterministic tractography. Importantly, we demonstrate the sensitivity of probabilistic tractography profiles to streamline number, step size, curvature, fiber orientation distribution, and whole-brain versus region of interest seeding. Using anatomically well-defined cortico-thalamic pathways, we show how density maps can permit the topographical assessment of probabilistic tractography. Finally, we show how different tractography approaches can impact on dMRI assessment of tract changes in a mouse deficient for the frontal cortex morphogen, fibroblast growth factor 17. In conclusion, probabilistic tractography can elucidate the phenotypes of mice with neurodegenerative or neurodevelopmental disorders in a quantitative manner. PMID:20303410

  2. Quantifying mixing using magnetic resonance imaging.

    PubMed

    Tozzi, Emilio J; McCarthy, Kathryn L; Bacca, Lori A; Hartt, William H; McCarthy, Michael J

    2012-01-01

    Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media (1, 2). The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile (1)H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for

  3. Quantifying Mixing using Magnetic Resonance Imaging

    PubMed Central

    Tozzi, Emilio J.; McCarthy, Kathryn L.; Bacca, Lori A.; Hartt, William H.; McCarthy, Michael J.

    2012-01-01

    Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media 1, 2. The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile 1H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for

  4. Magnetic Field Gradient Waveform Monitoring for Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Han, Hui

    Linear magnetic field gradients have played a central role in Magnetic Resonance Imaging (MRI) since Fourier Transform MRI was proposed three decades ago. Their primary function is to encode spatial information into MR signals. Magnetic field gradients are also used to sensitize the image contrast to coherent and/or incoherent motion, to selectively enhance an MR signal, and to minimize image artifacts. Modern MR imaging techniques increasingly rely on the implementation of complex gradient waveforms for the manipulation of spin dynamics. However, gradient system infidelities caused by eddy currents, gradient amplifier imperfections and group delays, often result in image artifacts and other errors (e.g., phase and intensity errors). This remains a critical problem for a wide range of MRI techniques on modern commercial systems, but is of particular concern for advanced MRI pulse sequences. Measuring the real magnetic field gradients, i.e., characterizing eddy currents, is critical to addressing and remedying this problem. Gradient measurement and eddy current calibration are therefore a general topic of importance to the science of MRI. The Magnetic Field Gradient Monitor (MFGM) idea was proposed and developed specifically to meet these challenges. The MFGM method is the heart of this thesis. MFGM methods permit a variety of magnetic field gradient problems to be investigated and systematically remedied. Eddy current effects associated with MR compatible metallic pressure vessels were analyzed, simulated, measured and corrected. The appropriate correction of eddy currents may enable most MR/MRI applications with metallic pressure vessels. Quantitative imaging (1D/2D) with model pressure vessels was successfully achieved by combining image reconstruction with MFGM determined gradient waveform behaviour. Other categories of MR applications with metallic vessels, including diffusion measurement and spin echo SPI T2 mapping, cannot be realized solely by MFGM guided

  5. Density separation of solids in ferrofluids with magnetic grids

    SciTech Connect

    Fay, H.; Quets, J.M.

    1980-04-01

    Nonmagnetic solids in a superparamagnetic ferrofluid are subjected to body forces proportional to the intensity of magnetization of the fluid and the gradient of the magnetic field. An apparent density of the fluid can be defined from the force equations, and since the apparent density can be much larger than the true density, it is possible to levitate or float dense objects. Mixtures of solids with a density greater than the apparent density sink while lower density solids float. In practice it is difficult to create a uniform gradient over a large volume and single gap magnetic separators require very large magnets or have a limited throughput. To overcome that problem, multiple gap magnetic grids have been designed. Such grids consist of planar arrays of parallel bars of alternating polarity, driven by permanent magnets. When immersed in ferrofluid, magnetic grids create nonuniform field gradients and apparent densities in the fluid. However, both analysis and experimental measurements show that the grid acts as a barrier to particles below a critical density, while permitting more dense particles to fall through the grid. Thus, a magnetic grid filter can be used as a high throughput binary separator of solids according to their densities. Such filters can be cascaded for more complex separations. Several magnetic grid filters have been designed, built, and tested. Magnetic measurements qualitatively agree with the theoretical predictions. Experiments with synthetic mixtures have demonstrated that good binary separations can be made.

  6. Tuning Coler Magnetic Current Apparatus with Magneto-Acoustic Resonance

    NASA Astrophysics Data System (ADS)

    Ludwig, Thorsten

    An attempt was made to tune the Coler magnetic current apparatus with the magneto acoustic resonance of the magnetic rods. Measurements with a replica of the famous Coler "Magnetstromapparat" were conducted. In order to tune the acoustic, magnetic and electric resonance circuits of the Coler device the magneto-acoustic resonance was measured with a frequency scan through a function generator and a lock-in amplifier. The frequency generator was powering a driving coil, while the lock-in was connected to a pickup coil. Both coils were placed on a magnetic rod. Resonances were observed up to the 17th harmonic. The quality Q of the observed resonances was 270. To study the magneto-acoustic resonance in the time domain a pair of Permendur rods were employed. The magneto-acoustic resonances of the Permendur rods were observed with an oscilloscope. Spectra of the magneto acoustic resonance were measured for the Permendur rods and for a Coler replica magnet in the frequency range from 25 kHz to 380 kHz. The next step was to bring the resonances of the Permendur rods close together so that they overlap. The 10thharmonic was chosen because it was close to the 180 kHz that Hans Coler related to ferromagnetism. Further more magneto-acoustic coupling between the Permendur rods was studied. Finally the question was explored if Hans Coler converted vacuum fluctuations via magnetic and acoustic resonance into electricity. There is a strong connection between magnetism and quantum field zero point energy (ZPE). An outlook is given on next steps in the experiments to unveil the working mechanism of the Coler magnetic current apparatus.

  7. Ferromagnetic Resonance Studies of Magnetic Recording Media

    NASA Astrophysics Data System (ADS)

    Yu, Yuwu

    1995-01-01

    Angular dependence of maximum remanence (ADMR) and/or x-ray diffraction (XRD) techniques have been used to determine particle orientation distributions for various recording media, including gamma -rm Fe_2O_3, Co- gamma-rm Fe_2O_3, CrO_2, Ba-ferrite, and MP tapes. A distribution of column directions for metal evaporated (ME) tape has been determined from transmission electron microscopy (TEM) pictures. However, the ferromagnetic resonance (FMR) results suggest a much more narrow distribution of magnetic anisotropy directions. For Ba-ferrite tapes, the distribution functions measured by ADMR are consistent with those by XRD if interparticle interactions are accounted for. The predetermined distribution function has been used to fit FMR spectra for the above tapes. Landau-Lifshitz damping constants have been measured with high accuracy for particulate recording media. An excellent correlation has been found between the damping constants and the switching constants for these media. The results suggest that the FMR technique may be useful in predicting the switching speed of particulate recording media. The FMR technique is also useful in looking for methods of increasing the damping constant of recording media. Possible methods of increasing the switching speed of Ba-ferrite media have been studied. The reduction of Ba-ferrite particles in a hydrogen atmosphere increases the damping constant significantly. It is predicted that reduced Ba-ferrite probably switches faster than ordinary Ba-ferrite. Qualitative discussions on the origin of damping for various recording media have been presented within the framework of magnon relaxation theory. The dependence of the damping constant on magnetic properties, such as particle orientation, media coercivity, and particle interactions are also discussed.

  8. Magnetic resonance imaging in cardiac amyloidosis

    SciTech Connect

    O'Donnell, J.K.; Go, R.T.; Bott-Silverman, C.; Feiglin, D.H.; Salcedo, E.; MacIntyre, W.J.

    1984-01-01

    Primary amyloidosis (AL) involves the myocardium in 90% of cases and may present as apparent ischemia, vascular disease, or congestive heart failure. Two-dimensional echocardiography (echo) has proven useful in the diagnosis, particularly in differentiating AL from constrictive pericarditis. The findings of thickened RV and LV myocardium, normal LV cavity dimension, and a diffuse hyperrefractile ''granular sparkling'' appearance are virtually diagnostic. Magnetic resonance (MR) imaging may improve the resolution of anatomic changes seen in cardiac AL and has the potential to provide more specific information based on biochemical tissue alterations. In this preliminary study, the authors obtained both MR and echo images in six patients with AL and biopsy-proven myocardial involvement. 5/6 patients also had Tc-99 PYP myocardial studies including emission tomography (SPECT). MR studies utilized a 0.6 Tesla superconductive magnet. End diastolic gated images were obtained with TE=30msec and TR=R-R interval on the ECG. 6/6 pts. showed LV wall thickening which was concentric and included the septum. Papillary muscles were identified in all and were enlarged in 3/6. 4/6 pts. showed RV wall thickening but to a lesser degree than LV. Pericardial effusions were present in 4 cases. These findings correlated well with the results of echo although MR gave better RV free wall resolution. PYP scans were positive in 3 pts. but there was no correlation with degree of LV thickening. The authors conclude that there are no identifiable MR findings in patients with cardiac AL which encourage further attempts to characterize myocardial involvement by measurement of MR relaxation times in vivo.

  9. Magnetic resonance spectroscopy in congenital heart disease.

    PubMed Central

    Miall-Allen, V. M.; Kemp, G. J.; Rajagopalan, B.; Taylor, D. J.; Radda, G. K.; Haworth, S. G.

    1996-01-01

    OBJECTIVE: To determine the feasibility of studying myocardial and skeletal muscle bioenergetics using 31P magnetic resonance spectroscopy (MRS) in babies and young children with congenital heart disease. SUBJECTS: 16 control subjects aged 5 months to 24 years and 18 patients with CHD, aged 7 months to 23 years, of whom 11 had cyanotic CHD, five had cardiac failure, and two had had a Senning procedure. DESIGN: 31P MRS was carried out using a 1.9 Tesla horizontal 65 cm bore whole body magnet to study the myocardium in 10 patients and skeletal muscle (gastrocnemius) in 14 patients, eight of whom were exercised, together with appropriate controls. RESULTS: In hypoxaemic patients, in skeletal muscle at rest intracellular pH (pHi) was abnormally high [7.06 (SEM 0.04) v 7.04 (0.05), P < 0.01] and showed a positive correlation with haemoglobin (P < 0.03). On exercise, hypoxaemic patients fatigued more quickly but end-exercise pHi and phosphocreatine recovery were normal, implying that an equivalent but smaller amount of work had been performed. End-exercise ADP concentration was lower. On recovery, the initial rate of phosphocreatine resynthesis was low. Skeletal muscle bioenergetics were within normal limits in those in heart failure. In the myocardium, the phosphocreatine/ATP ratio was similar in controls and hypoxaemic subjects, but low in those in heart failure. CONCLUSIONS: In heart failure, the myocardial phosphocreatine/ATP ratio was reduced, as in adults, while resting skeletal muscle studies were normal. By contrast, hypoxaemic children had normal myocardial bioenergetics, but showed skeletal muscle alkalinity, and energy reserves were more readily depleted on exercise. On recovery, the initially slow phosphocreatine resynthesis rate reflects a low rate of mitochondrial ATP synthesis, probably due to an inadequate oxygen supply. 31P MRS offers a safe, non-invasive method of studying myocardial and skeletal muscle bioenergetics in children as young as 5 months

  10. Real-time magnetic resonance imaging investigation of resonance tuning in soprano singing.

    PubMed

    Bresch, Erik; Narayanan, Shrikanth

    2010-11-01

    This article investigates using real-time magnetic resonance imaging the vocal tract shaping of 5 soprano singers during the production of two-octave scales of sung vowels. A systematic shift of the first vocal tract resonance frequency with respect to the fundamental is shown to exist for high vowels across all subjects. No consistent systematic effect on the vocal tract resonance could be shown across all of the subjects for other vowels or for the second vocal tract resonance. PMID:21110548

  11. Properties of the resonant tunneling diode in external magnetic field with inclusion of the Rashba effect

    NASA Astrophysics Data System (ADS)

    Niketić, Nemanja; Milanović, Vitomir; Radovanović, Jelena

    2014-07-01

    Influence of the Rashba effect on electronic properties of resonant tunneling diode in an external magnetic field is analyzed in this paper. Wave functions and energies, as well as expressions for currents densities, are determined for electrons of both spins. Appearances of many modes due to the external magnetic field induce irregularities in the current-voltage characteristics, which are observable in case when the thermal energy is lower than, or comparable to, the energy difference of two consecutive Landau levels. Current density through the heterostructure is investigated with emphasis on the degree of spin polarization; further, spin transfer is shown to depend on the direction of external magnetic field.

  12. Size Dependence of Ferromagnetic Resonance Frequency in Submicron Patterned Magnet

    NASA Astrophysics Data System (ADS)

    Manago, Takashi; Yamanoi, Kazuto; Yakata, Satoshi; Kimura, Takashi

    2013-05-01

    We investigated the size effect on ferromagnetic resonance (FMR) in a submicron-wide single permalloy bar. The resonant frequency markedly increased with decreasing bar width to less than 1 µm, since the demagnetizing field is effectively modified by changing the bar width even in thin films. The resonant frequency difference between 100- and 1000-nm-wide bars was over 4 GHz in the absence of a magnetic field. This characteristic is promising for practical microwave devices because the desired resonant frequency can be obtained simply by varying the width of narrow ferromagnetic bars so that it is not necessary to change the material or magnetic field.

  13. Nuclear magnetic resonance spectrometric assay of beta-lactamase.

    PubMed Central

    Kono, M; O'Hara, K; Shiomi, Y

    1980-01-01

    Beta-Lactam antibiotics and the crude enzyme were mixed in deuterium oxide and placed in a nuclear magnetic resonance tube. The change of the nuclear magnetic resonance spectrum during the enzymatic reaction was then analyzed to determine beta-lactamase activity. By using beta-lactam antibiotics such as penicillins, cephalosporins, and cephamycins as substrates, a comparison of the beta-lactamase activities was made between the nuclear magnetic resonance spectrometric assay and the iodometric assay. There was a close correlation between these two methods. PMID:6986114

  14. Advances in cardiac magnetic resonance imaging of congenital heart disease.

    PubMed

    Driessen, Mieke M P; Breur, Johannes M P J; Budde, Ricardo P J; van Oorschot, Joep W M; van Kimmenade, Roland R J; Sieswerda, Gertjan Tj; Meijboom, Folkert J; Leiner, Tim

    2015-01-01

    Due to advances in cardiac surgery, survival of patients with congenital heart disease has increased considerably during the past decades. Many of these patients require repeated cardiovascular magnetic resonance imaging to assess cardiac anatomy and function. In the past decade, technological advances have enabled faster and more robust cardiovascular magnetic resonance with improved image quality and spatial as well as temporal resolution. This review aims to provide an overview of advances in cardiovascular magnetic resonance hardware and acquisition techniques relevant to both pediatric and adult patients with congenital heart disease and discusses the techniques used to assess function, anatomy, flow and tissue characterization. PMID:25552386

  15. Circular polarization in a non-magnetic resonant tunneling device.

    PubMed

    Dos Santos, Lara F; Gobato, Yara Galvão; Teodoro, Márcio D; Lopez-Richard, Victor; Marques, Gilmar E; Brasil, Maria Jsp; Orlita, Milan; Kunc, Jan; Maude, Duncan K; Henini, Mohamed; Airey, Robert J

    2011-01-01

    We have investigated the polarization-resolved photoluminescence (PL) in an asymmetric n-type GaAs/AlAs/GaAlAs resonant tunneling diode under magnetic field parallel to the tunnel current. The quantum well (QW) PL presents strong circular polarization (values up to -70% at 19 T). The optical emission from GaAs contact layers shows evidence of highly spin-polarized two-dimensional electron and hole gases which affects the spin polarization of carriers in the QW. However, the circular polarization degree in the QW also depends on various other parameters, including the g-factors of the different layers, the density of carriers along the structure, and the Zeeman and Rashba effects. PMID:21711613

  16. Nuclear magnetic resonance evaluation of stroke: a preliminary report

    SciTech Connect

    Bryan, R.N.; Willcott, M.R.; Schneiders, N.J.; Ford, J.J.; Derman, H.S.

    1983-10-01

    Nine patients who had acute and subacute stroke were examined by nuclear magnetic resonance (NMR) using a 6-MHz Bruker Instruments proton scanner. A modified Carr-Purcell-Meiboom-Gill pulse sequence was used for signal detection. The resultant string of spin-echoes was Fourier transformed into projections that were subsequently back-projected to a series of spin-echo images. From these images, spin density and T/sub 2/ were calculated for each pixel. The NMR scans revealed stroke in each of the patients, while CT demonstrated only eight of the lesions. T/sub 2/ was prolonged in all of the ischemic regions and is the most sensitive NMR parameter in detecting stroke. These preliminary results suggest that NMR scanning of patients who have acute stroke may be cliniclly useful, and that the T/sub 2/ component of the NRM signal is most important.

  17. Fetal magnetic resonance imaging and ultrasound.

    PubMed

    Wataganara, Tuangsit; Ebrashy, Alaa; Aliyu, Labaran Dayyabu; Moreira de Sa, Renato Augusto; Pooh, Ritsuko; Kurjak, Asim; Sen, Cihat; Adra, Abdallah; Stanojevic, Milan

    2016-07-01

    Magnetic resonance imaging (MRI) has been increasingly adopted in obstetrics practice in the past three decades. MRI aids prenatal ultrasound and improves diagnostic accuracy for selected maternal and fetal conditions. However, it should be considered only when high-quality ultrasound cannot provide certain information that affects the counseling, prenatal intervention, pregnancy course, and delivery plan. Major indications of fetal MRI include, but are not restricted to, morbidly adherent placenta, selected cases of fetal brain anomalies, thoracic lesions (especially in severe congenital diaphragmatic hernia), and soft tissue tumors at head and neck regions of the fetus. For fetal anatomy assessment, a 1.5-Tesla machine with a fast T2-weighted single-shot technique is recommended for image requisition of common fetal abnormalities. Individual judgment needs to be applied when considering usage of a 3-Tesla machine. Gadolinium MRI contrast is not recommended during pregnancy. MRI should be avoided in the first half of pregnancy due to small fetal structures and motion artifacts. Assessment of fetal cerebral cortex can be achieved with MRI in the third trimester. MRI is a viable research tool for noninvasive interrogation of the fetus and the placenta. PMID:27092644

  18. Magnetic resonance imaging structured reporting in infertility.

    PubMed

    Montoliu-Fornas, Guillermina; Martí-Bonmatí, Luis

    2016-06-01

    Our objective was to define and propose a standardized magnetic resonance (MR) imaging structured report in patients with infertility to have clinical completeness on possible diagnosis and severity. Patients should be studied preferable on 3T equipment with a surface coil. Standard MR protocol should include high-resolution fast spin-echo T2-weighted, diffusion-weighted images and gradient-echo T1-weighted fat suppression images. The report should include ovaries (polycystic, endometrioma, tumor), oviduct (hydrosalpinx, hematosalpinx, pyosalpinx, peritubal anomalies), uterus (agenesia, hypoplasia, unicornuate, uterus didelphys, bicornuate, septate uterus), myometrium (leiomyomas, adenomyosis), endometrium (polyps, synechia, atrophy, neoplasia), cervix and vagina (isthmoceles, mucosal-parietal irregularity, stenosis, neoplasia), peritoneum (deep endometriosis), and urinary system-associated abnormalities. To be clinically useful, radiology reports must be structured, use standardized terminology, and convey actionable information. The structured report must comprise complete, comprehensive, and accurate information, allowing radiologists to continuously interact with patients and referring physicians to confirm that the information is used properly to affect the decision making process. PMID:27105717

  19. Vibration safety limits for magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Ehman, E. C.; Rossman, P. J.; Kruse, S. A.; Sahakian, A. V.; Glaser, K. J.

    2008-02-01

    Magnetic resonance elastography (MRE) has been demonstrated to have potential as a clinical tool for assessing the stiffness of tissue in vivo. An essential step in MRE is the generation of acoustic mechanical waves within a tissue via a coupled mechanical driver. Motivated by an increasing volume of human imaging trials using MRE, the objectives of this study were to audit the vibration amplitude of exposure for our IRB-approved human MRE studies, to compare these values to a conservative regulatory standard for vibrational exposure and to evaluate the applicability and implications of this standard for MRE. MRE displacement data were examined from 29 MRE exams, including the liver, brain, kidney, breast and skeletal muscle. Vibrational acceleration limits from a European Union directive limiting occupational exposure to whole-body and extremity vibrations (EU 2002/44/EC) were adjusted for time and frequency of exposure, converted to maximum displacement values and compared to the measured in vivo displacements. The results indicate that the vibrational amplitudes used in MRE studies are below the EU whole-body vibration limit, and the EU guidelines represent a useful standard that could be readily accepted by Institutional Review Boards to define standards for vibrational exposures for MRE studies in humans.

  20. Segmentation of neuroanatomy in magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Simmons, Andrew; Arridge, Simon R.; Barker, G. J.; Tofts, Paul S.

    1992-06-01

    Segmentation in neurological magnetic resonance imaging (MRI) is necessary for feature extraction, volume measurement and for the three-dimensional display of neuroanatomy. Automated and semi-automated methods offer considerable advantages over manual methods because of their lack of subjectivity, their data reduction capabilities, and the time savings they give. We have used dual echo multi-slice spin-echo data sets which take advantage of the intrinsically multispectral nature of MRI. As a pre-processing step, a rf non-uniformity correction is applied and if the data is noisy the images are smoothed using a non-isotropic blurring method. Edge-based processing is used to identify the skin (the major outer contour) and the eyes. Edge-focusing has been used to significantly simplify edge images and thus allow simple postprocessing to pick out the brain contour in each slice of the data set. Edge- focusing is a technique which locates significant edges using a high degree of smoothing at a coarse level and tracks these edges to a fine level where the edges can be determined with high positional accuracy. Both 2-D and 3-D edge-detection methods have been compared. Once isolated, the brain is further processed to identify CSF, and, depending upon the MR pulse sequence used, the brain itself may be sub-divided into gray matter and white matter using semi-automatic contrast enhancement and clustering methods.

  1. Progesterone-Targeted Magnetic Resonance Imaging Probes

    PubMed Central

    2015-01-01

    Determination of progesterone receptor (PR) status in hormone-dependent diseases is essential in ascertaining disease prognosis and monitoring treatment response. The development of a noninvasive means of monitoring these processes would have significant impact on early detection, cost, repeated measurements, and personalized treatment options. Magnetic resonance imaging (MRI) is widely recognized as a technique that can produce longitudinal studies, and PR-targeted MR probes may address a clinical problem by providing contrast enhancement that reports on PR status without biopsy. Commercially available MR contrast agents are typically delivered via intravenous injection, whereas steroids are administered subcutaneously. Whether the route of delivery is important for tissue accumulation of steroid-modified MRI contrast agents to PR-rich tissues is not known. To address this question, modification of the chemistry linking progesterone with the gadolinium chelate led to MR probes with increased water solubility and lower cellular toxicity and enabled administration through the blood. This attribute came at a cost through lower affinity for PR and decreased ability to cross the cell membrane, and ultimately it did not improve delivery of the PR-targeted MR probe to PR-rich tissues or tumors in vivo. Overall, these studies are important, as they demonstrate that targeted contrast agents require optimization of delivery and receptor binding of the steroid and the gadolinium chelate for optimal translation in vivo. PMID:25019183

  2. Magnetic resonance imaging of the kidneys

    SciTech Connect

    Leung, A.W.L.; Bydder, G.M.; Steinter, R.E.; Bryant, D.J.; Young, I.R.

    1984-12-01

    A study of the magnetic resonance imaging (MRI) appearance of the kidneys in six normal volunteers and 52 patients is reported. Corticomedullary differentiation was seen with the inversion-recovery (IR 1400/400) sequence in the normal volunteers and in patients with functioning transplanted kidneys and acute tubular necrosis. Partial or total loss of corticomedullary differentiation was seen in glomerulonephritis, acute and chronic renal failure, renal artery stenosis, and transplant rejection. The T1 of the kidneys was increased in glomerulonephritis with neuphrotic syndrome, but the T1 was within the normal range for renal medulla in glomerulonephritis without nephrotic syndrome, renal artery stenosis, and chronic renal failure. A large staghorn calculus was demonstrated with MRI, but small calculi were not seen. Fluid within the hydonephrosis, simple renal cysts, and polycystic kidneys displayed very low signal intensity and long T1 values. Tumors displayed varied appearances. Hypernephromas were shown to be hypo- or hyperintense with the renal medulla on the IR 1400/400 sequence. After intravenous injection of gadolinium-DTPA, there was marked decrease in the tumor T1.

  3. TOPICAL REVIEW: Endovascular interventional magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Bartels, L. W.; Bakker, C. J. G.

    2003-07-01

    Minimally invasive interventional radiological procedures, such as balloon angioplasty, stent placement or coiling of aneurysms, play an increasingly important role in the treatment of patients suffering from vascular disease. The non-destructive nature of magnetic resonance imaging (MRI), its ability to combine the acquisition of high quality anatomical images and functional information, such as blood flow velocities, perfusion and diffusion, together with its inherent three dimensionality and tomographic imaging capacities, have been advocated as advantages of using the MRI technique for guidance of endovascular radiological interventions. Within this light, endovascular interventional MRI has emerged as an interesting and promising new branch of interventional radiology. In this review article, the authors will give an overview of the most important issues related to this field. In this context, we will focus on the prerequisites for endovascular interventional MRI to come to maturity. In particular, the various approaches for device tracking that were proposed will be discussed and categorized. Furthermore, dedicated MRI systems, safety and compatibility issues and promising applications that could become clinical practice in the future will be discussed.

  4. Nuclear magnetic resonance imaging of the kidney

    SciTech Connect

    Hricak, H.; Crooks, L.; Sheldon, P.; Kaufman, L.

    1983-02-01

    The role of nuclear magnetic resonance (NMR) imaging of the kidney was analyzed in 18 persons (6 normal volunteers, 3 patients with pelvocaliectasis, 2 with peripelvic cysts, 1 with renal sinus lipomatosis, 3 with renal failure, 1 with glycogen storage disease, and 2 with polycystic kidney disease). Ultrasound and/or computed tomography (CT) studies were available for comparison in every case. In the normal kidney distinct anatomical structures were clearly differentiated by NMR. The best anatomical detail ws obtained with spin echo (SE) imaging, using a pulse sequence interval of 1,000 msec and an echo delay time of 28 msec. However, in the evaluation of normal and pathological conditions, all four intensity images (SE 500/28, SE 500/56, SE 1,000/28, and SE 1,000/56) have to be analyzed. No definite advantage was found in using SE imaging with a pulse sequence interval of 1,500 msec. Inversion recovery imaging enhanced the differences between the cortex and medulla, but it had a low signal-to-noise level and, therefore, a suboptimal overall resolution. The advantages of NMR compared with CT and ultrasound are discussed, and it is concluded that NMR imaging will prove to be a useful modality in the evaluation of renal disease.

  5. Stereotactic localization using magnetic resonance imaging.

    PubMed

    Walton, L; Hampshire, A; Forster, D M; Kemeny, A A

    1995-01-01

    A phantom study has been carried out to assess the accuracy of stereotactic localisation, using magnetic resonance imaging. The stereotactic coordinates of an array of Perspex rods within the phantom were determined and compared with measured values, in a series of transverse, coronal and sagittal images. In the transverse plane, the maximum errors experienced were X = 2.3 mm and Y = 10.7 mm. If the third fiducial plate, at the front of the frame, were not used in the scaling of the images, there was considerable improvement in the Y direction (maximum error Y = 2.1 mm). However, some deterioration in the accuracy in the X direction resulted, particularly at the extremes of Z (maximum error X = 3.5 mm). In the coronal plane, the maximum errors were X = 1.8 mm and Z = 8.0 mm. With the third plate off, the errors decreased to X = 1.9 mm and Z = 3.3 mm. In the sagittal plane, the maximum errors recorded were Y = 1.1 mm and Z = 7.5 mm. It is not possible to calibrate in this plane without the third plate. PMID:8584823

  6. Magnetic resonance--guided musculoskeletal interventional radiology.

    PubMed

    Carrino, John A; Blanco, Roberto

    2006-06-01

    As an imaging modality, magnetic resonance (MR) guidance has great potential to direct diagnostic and therapeutic procedures performed in the musculoskeletal region and influence patient management. MR-guided interventional procedures involving bone, soft tissue, intervertebral discs, and joints are safe and sufficiently effective for use in clinical practice. This article discusses and illustrates the procedural characteristics and techniques when performing MR-guided musculoskeletal interventions. Biopsy procedures are similar to other modalities for bone and soft tissue lesions. MR guidance is advantageous if the lesion is not visible by other modalities and for regions adjacent to hardware and implants, subselective targeting, intra-articular locations, and periarticular cyst aspiration. MR guidance has also been used for a host of spine injections and pain management procedures such as sacroiliac joint injections, discography, transforaminal epidural injection, selective nerve block, sympathetic block, celiac plexus block, and facet joint cryotherapy neurotomies. Future directions of clinical applications include tumor ablation and multimodality procedure suites. MR-guided musculoskeletal procedures will continue to be a growth area particularly for the diagnosis and treatment of bone and soft tissue neoplasia. PMID:16586322

  7. Magnetic resonance imaging: present and future applications

    PubMed Central

    Johnston, Donald L.; Liu, Peter; Wismer, Gary L.; Rosen, Bruce R.; Stark, David D.; New, Paul F.J.; Okada, Robert D.; Brady, Thomas J.

    1985-01-01

    Magnetic resonance (MR) imaging has created considerable excitement in the medical community, largely because of its great potential to diagnose and characterize many different disease processes. However, it is becoming increasingly evident that, because MR imaging is similar to computed tomography (CT) scanning in identifying structural disorders and because it is more costly and difficult to use, this highly useful technique must be judged against CT before it can become an accepted investigative tool. At present MR imaging has demonstrated diagnostic superiority over CT in a limited number of important, mostly neurologic, disorders and is complementary to CT in the diagnosis of certain other disorders. For most of the remaining organ systems its usefulness is not clear, but the lack of ionizing radiation and MR's ability to produce images in any tomographic plane may eventually prove to be advantageous. The potential of MR imaging to display in-vivo spectra, multinuclear images and blood-flow data makes it an exciting investigative technique. At present, however, MR imaging units should be installed only in medical centres equipped with the clinical and basic research facilities that are essential to evaluate the ultimate role of this technique in the care of patients. ImagesFig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14 PMID:3884120

  8. [Magnetic resonance angiography of the renal arteries].

    PubMed

    Matos, C; Metens, T; Nicaise, N; Golzarian, J; Dussaussois, L; Struyven, J

    1999-09-01

    Initially, the clinical use of magnetic resonance angiography (MRA) in the abdomen has been restricted because of motion and flow related artifacts. The advent of high performance gradient systems made possible the development of 3D gadolinium-enhanced MRA techniques and expanded the clinical applications of MRA into the abdominal area, particularly for the investigation of renal arteries. This technique is safe, because the administered contrast agent (gadolinium) is free of clinically detectable nephrotoxicity and has a low incidence of allergic reactions. Moreover, contrast MRA also eliminates the risks of ionizing radiation which allows repeating the examination without the accumulation of radiation exposure. The main disadvantages of the technique are its low availability and the fact that the use of contrast agents for this procedure is still not reimbursed by the social security. Many studies demonstrated that contrast MRA allows for the reliable assessment of renal artery morphology and pathologic states. Furthermore, within a single MR examination a comprehensive approach including renal artery morphology, hemodynamic significance of any stenosis and kidney perfusion is available. In this paper, we provide a review of the literature concerning the clinical performance of contrast MRA for the renal arteries and suggest its rationale for the investigation of patients suspected of renovascular disease in our specific environment. PMID:10523920

  9. Scatter-based magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Papazoglou, Sebastian; Xu, Chao; Hamhaber, Uwe; Siebert, Eberhard; Bohner, Georg; Klingebiel, Randolf; Braun, Jürgen; Sack, Ingolf

    2009-04-01

    Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems. Therefore, an MRE method is introduced that avoids inversion and instead exploits shear wave scattering at elastic interfaces between anatomical regions of different shear compliance. This compliance-weighted imaging (CWI) method can be used to evaluate the mechanical consistency of cerebral lesions or to measure relative stiffness differences between anatomical subregions of the brain. It is demonstrated that CWI-MRE is sensitive enough to reveal significant elasticity variations within inner brain parenchyma: the caudate nucleus (head) was stiffer than the lentiform nucleus and the thalamus by factors of 1.3 ± 0.1 and 1.7 ± 0.2, respectively (P < 0.001). CWI-MRE provides a unique method for characterizing brain tissue by identifying local stiffness variations.

  10. Magnetic Resonance Angiography of the Aorta

    PubMed Central

    Takehara, Yasuo; Yamashita, Shuhei; Sakahara, Harumi; Masui, Takayuki; Isoda, Haruo

    2011-01-01

    Magnetic resonance angiography (MRA) is capable of imaging arteries in the half to whole body by a single acquisition without a nephrotoxic contrast medium, and acquired images can be reconstructed into a specific cross-sectional view in an arbitrary directions. MRA is applicable for vessels non-reachable by a catheter approach, and collateral vessels can be fully visualized. Since MRA is minimally-invasive with no exposure to ionized radiation, it can be repeatedly applied for follow-up. However, there are also disadvantages: the temporal and spatial resolutions are inferior to those of X-ray angiography, and, at present, it cannot be used as a guide for intervention. Moreover, gadolinium administrations may cause NSF in patients who have lost renal function, as a new risk. Accordingly, strict consideration is required for an indication of its application. Development of non-contrast MRA and evaluation of the wall itself may draw more attention in the future. Plaque imaging is being routinely performed nowadays, and the measurement of vascular wall shear stress, which has a close association with arteriosclerosis, may become possible by utilizing the time-resolved phase-contrast method capable of measuring the time-resolved velocity vectors of blood flow throughout the body. (*English Translation of J Jpn Coll Angiol, 2009, 49: 503-516.) PMID:23555465

  11. Magnetic Resonance Elastography: Inversions in Bounded Media

    PubMed Central

    Kolipaka, Arunark; McGee, Kiaran P.; Manduca, Armando; Romano, Anthony J.; Glaser, Kevin J.; Araoz, Philip A.; Ehman, Richard L.

    2009-01-01

    Magnetic resonance elastography (MRE) is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, MRE inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates and spherical shells using geometry-specific equations of motion. MRE and finite element modeling (FEM) of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from FEM and MRE data and a linear correlation of r2 ≥ 0.99 was observed between the stiffness values obtained using MRE and FEM data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media. PMID:19780146

  12. Magnetic Resonance Imaging at Ultrahigh Fields

    PubMed Central

    Uğurbil, Kamil

    2014-01-01

    Since the introduction of 4 T human systems in three academic laboratories circa 1990, rapid progress in imaging and spectroscopy studies in humans at 4 T and animal model systems at 9.4 T have led to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has demonstrated the existence of significant advantages in SNR and biological information content at these ultrahigh fields, as well as the presence of numerous challenges. Primary difference from lower fields is the deviation from the near field regime; at the frequencies corresponding to hydrogen resonance conditions at ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image nonuniformities for a given sample-coil configuration because of interferences. These nonuniformities were considered detrimental to the progress of imaging at high field strengths. However, they are advantageous for parallel imaging for signal reception and parallel transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies, and improvements in instrumentation and imaging methods, ultra-high fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques. PMID:24686229

  13. Magnetic resonance imaging in brachial plexus injury.

    PubMed

    Caranci, F; Briganti, F; La Porta, M; Antinolfi, G; Cesarano, E; Fonio, P; Brunese, L; Coppolino, F

    2013-08-01

    Brachial plexus injury represents the most severe nerve injury of the extremities. While obstetric brachial plexus injury has showed a reduction in the number of cases due to the improvements in obstetric care, brachial plexus injury in the adult is an increasingly common clinical problem. The therapeutic measures depend on the pathologic condition and the location of the injury: Preganglionic avulsions are usually not amenable to surgical repair; function of some denervated muscles can be restored with nerve transfers from intercostals or accessory nerves and contralateral C7 transfer. Postganglionic avulsions are repaired with excision of the damaged segment and nerve autograft between nerve ends or followed up conservatively. Magnetic resonance imaging is the modality of choice for depicting the anatomy and pathology of the brachial plexus: It demonstrates the location of the nerve damage (crucial for optimal treatment planning), depicts the nerve continuity (with or without neuroma formation), or may show a completely disrupted/avulsed nerve, thereby aiding in nerve-injury grading for preoperative planning. Computed tomography myelography has the advantage of a higher spatial resolution in demonstration of nerve roots compared with MR myelography; however, it is invasive and shows some difficulties in the depiction of some pseudomeningoceles with little or no communication with the dural sac. PMID:23949940

  14. Magnetic Resonance Imaging of Pituitary Tumors.

    PubMed

    Bonneville, Jean-François

    2016-01-01

    Magnetic Resonance Imaging (MRI) is currently considered a major keystone of the diagnosis of diseases of the hypothalamic-hypophyseal region. However, the relatively small size of the pituitary gland, its location deep at the skull base and the numerous physiological variants present in this area impede the precise assessment of the anatomical structures and, particularly, of the pituitary gland itself. The diagnosis of the often tiny lesions of this region--such as pituitary microadenomas--is then difficult if the MRI technology is not optimized and if potential artifacts and traps are not recognized. Advanced MRI technology can not only depict small lesions with greater reliability, but also help in the differential diagnosis of large tumors. In these, defining the presence or absence of invasion is a particularly important task. This review describes and illustrates the radiological diagnosis of the different tumors of the sellar region, from the common prolactinomas, nonfunctioning adenomas and Rathke's cleft cysts, to the less frequent and more difficult to detect corticotroph pituitary adenomas in Cushing's disease, and other neoplastic and nonneoplastic entities. Finally, some hints are given to facilitate the differential diagnosis of sellar lesions. PMID:27003878

  15. Magnetic Resonance Imaging of Cartilage Repair

    PubMed Central

    Trattnig, Siegfried; Winalski, Carl S.; Marlovits, Stephan; Jurvelin, Jukka S.; Welsch, Goetz H.; Potter, Hollis G.

    2011-01-01

    Articular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression. Cartilage repair surgery, no matter the technique, requires a noninvasive, standardized, and high-quality longitudinal method to assess the structure of the repair tissue. This goal is best fulfilled by magnetic resonance imaging (MRI). The present article provides an overview of the current state of the art of MRI of cartilage repair. In the first 2 sections, preclinical and clinical MRI of cartilage repair tissue are described with a focus on morphological depiction of cartilage and the use of functional (biochemical) MR methodologies for the visualization of the ultrastructure of cartilage repair. In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries. PMID:26069565

  16. Magnetic resonance imaging of benign prostatic hyperplasia

    PubMed Central

    Guneyli, Serkan; Ward, Emily; Thomas, Stephen; Yousuf, Ambereen Nehal; Trilisky, Igor; Peng, Yahui; Antic, Tatjana; Oto, Aytekin

    2016-01-01

    Benign prostatic hyperplasia (BPH) is a common condition in middle-aged and older men and negatively affects the quality of life. An ultrasound classification for BPH based on a previous pathologic classification was reported, and the types of BPH were classified according to different enlargement locations in the prostate. Afterwards, this classification was demonstrated using magnetic resonance imaging (MRI). The classification of BPH is important, as patients with different types of BPH can have different symptoms and treatment options. BPH types on MRI are as follows: type 0, an equal to or less than 25 cm3 prostate showing little or no zonal enlargements; type 1, bilateral transition zone (TZ) enlargement; type 2, retrourethral enlargement; type 3, bilateral TZ and retrourethral enlargement; type 4, pedunculated enlargement; type 5, pedunculated with bilateral TZ and/or retrourethral enlargement; type 6, subtrigonal or ectopic enlargement; type 7, other combinations of enlargements. We retrospectively evaluated MRI images of BPH patients who were histologically diagnosed and presented the different types of BPH on MRI. MRI, with its advantage of multiplanar imaging and superior soft tissue contrast resolution, can be used in BPH patients for differentiation of BPH from prostate cancer, estimation of zonal and entire prostatic volumes, determination of the stromal/glandular ratio, detection of the enlargement locations, and classification of BPH types which may be potentially helpful in choosing the optimal treatment. PMID:27015442

  17. Resonant microwave cavity for 8.5-12 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Colton, J. S.; Wienkes, L. R.

    2009-03-01

    We present a newly developed microwave resonant cavity for use in optically detected magnetic resonance (ODMR) experiments. The cylindrical quasi-TE011 mode cavity is designed to fit in a 1 in. magnet bore to allow the sample to be optically accessed and to have an adjustable resonant frequency between 8.5 and 12 GHz. The cavity uses cylinders of high dielectric material, so-called "dielectric resonators," in a double-stacked configuration to determine the resonant frequency. Wires in a pseudo-Helmholtz configuration are incorporated into the cavity to provide frequencies for simultaneous nuclear magnetic resonance (NMR). The system was tested by measuring cavity absorption as microwave frequencies were swept, by performing ODMR on a zinc-doped InP sample, and by performing optically detected NMR on a GaAs sample. The results confirm the suitability of the cavity for ODMR with simultaneous NMR.

  18. Determination of the line shapes of atomic nitrogen resonance lines by magnetic scans

    NASA Technical Reports Server (NTRS)

    Lawrence, G. M.; Stone, E. J.; Kley, D.

    1976-01-01

    A technique is given for calibrating an atomic nitrogen resonance lamp for use in determining column densities of atoms in specific states. A discharge lamp emitting the NI multiplets at 1200 A and 1493 A is studied by obtaining absorption by atoms in a magnetic field (0-2.5 T). This magnetic scanning technique enables the determination of the absorbing atom column density, and an empirical curve of growth is obtained because the atomic f-value is known. Thus, the calibrated lamp can be used in the determination of atomic column densities.

  19. Magnetic resonance force microscopy with a permanent magnet on the cantilever

    SciTech Connect

    Zhang, Z.; Hammel, P.C.

    1997-02-01

    The magnetic resonance force microscope (MRFM) is a microscopic 3-D imaging instrument based on a recent proposal to detect magnetic resonance signals mechanically using a micro-mechanical resonator. MRFM has been successfully demonstrated in various magnetic resonance experiments including electron spin resonance, ferromagnetic resonances and nuclear magnetic resonance. In order to apply this ultra-high, 3-D spatial resolution technique to samples of arbitrary size and shape, the magnetic particle which generates the field gradient {del}{bold B}, (and, therefore, the force {bold F = (m {center_dot} {del}B)} between itself and the spin magnetization {bold m} of the sample) will need to be mounted on the mechanical resonator. Up to the present, all experiments have been performed with the sample mounted on the resonator. This is done, in part, to avoid the spurious response of the mechanical resonator which is generated by the variation of the magnetization of the magnetic particle as the external field is varied.

  20. Sensitive magnetic force detection with a carbon nanotube resonator

    SciTech Connect

    Willick, Kyle; Haapamaki, Chris; Baugh, Jonathan

    2014-03-21

    We propose a technique for sensitive magnetic point force detection using a suspended carbon nanotube (CNT) mechanical resonator combined with a magnetic field gradient generated by a ferromagnetic gate electrode. Numerical calculations of the mechanical resonance frequency show that single Bohr magneton changes in the magnetic state of an individual magnetic molecule grafted to the CNT can translate to detectable frequency shifts, on the order of a few kHz. The dependences of the resonator response to device parameters such as length, tension, CNT diameter, and gate voltage are explored and optimal operating conditions are identified. A signal-to-noise analysis shows that, in principle, magnetic switching at the level of a single Bohr magneton can be read out in a single shot on timescales as short as 10 μs. This force sensor should enable new studies of spin dynamics in isolated single molecule magnets, free from the crystalline or ensemble settings typically studied.

  1. Resonantly driven nonlinear density waves in protostellar disks

    NASA Technical Reports Server (NTRS)

    Yuan, Chi; Cassen, Pat

    1994-01-01

    Recent observations of binary, pre-main-sequence, solar-type stars provide evidence that such systems may coexist with circumstellar disks. The binary disk systems, besides being of general interest for the study of star formation, potentially provide useful tests of companion-disk interaction theories prominent in current hypotheses of planet formation. In this paper, we apply an asymptotic analysis of the nonlinear, resonant interaction of a stellar companion with a disk to understand the dependence of such interactions on the properties of the system: the binary mass ratio, the physical properties of the disk, and the effective dissipation (treated herein as viscosity). The method is based on a WKBJ approximation and exploits the conditions that the disk is thin and much less massive than the primary, but does not require that the companion-induced disturbance be small. Both isothermal and adiabatic responses are treated. Only circular orbit resonances are considered in this paper. It is demonstrated that the temperature of the disk as well as the relative mass of the companion affects the degree of nonlinearity, and that nonlinearity promotes high wave compression ratios, long wavelengths, and increased propagation distances. Nevertheless, the total torque exerted between the companion and the disk is well represented by linear theory. The amplitudes of density disturbances are reduced by viscosity and nonisothermality. Because resonant interactions are generally strong and capable of driving rapid evolution, one might expect observations of systems undergoing strong, resonant-driven evolution to be rare. In this connection, it is pointed out that the m = 1 resonance is distinguished by being anomalously weaker than the others and is therefore of observational interest. It is speculated that, in conditions of intrinsically small dissipation, the propagation of resonant-driven density waves is limited by the tendency of their wavelength to diminish with distance

  2. Dynamic nuclear polarization in a magnetic resonance force microscope experiment.

    PubMed

    Issac, Corinne E; Gleave, Christine M; Nasr, Paméla T; Nguyen, Hoang L; Curley, Elizabeth A; Yoder, Jonilyn L; Moore, Eric W; Chen, Lei; Marohn, John A

    2016-04-01

    We report achieving enhanced nuclear magnetization in a magnetic resonance force microscope experiment at 0.6 tesla and 4.2 kelvin using the dynamic nuclear polarization (DNP) effect. In our experiments a microwire coplanar waveguide delivered radiowaves to excite nuclear spins and microwaves to excite electron spins in a 250 nm thick nitroxide-doped polystyrene sample. Both electron and proton spin resonance were observed as a change in the mechanical resonance frequency of a nearby cantilever having a micron-scale nickel tip. NMR signal, not observable from Curie-law magnetization at 0.6 T, became observable when microwave irradiation was applied to saturate the electron spins. The resulting NMR signal's size, buildup time, dependence on microwave power, and dependence on irradiation frequency was consistent with a transfer of magnetization from electron spins to nuclear spins. Due to the presence of an inhomogeneous magnetic field introduced by the cantilever's magnetic tip, the electron spins in the sample were saturated in a microwave-resonant slice 10's of nm thick. The spatial distribution of the nuclear polarization enhancement factor ε was mapped by varying the frequency of the applied radiowaves. The observed enhancement factor was zero for spins in the center of the resonant slice, was ε = +10 to +20 for spins proximal to the magnet, and was ε = -10 to -20 for spins distal to the magnet. We show that this bipolar nuclear magnetization profile is consistent with cross-effect DNP in a ∼10(5) T m(-1) magnetic field gradient. Potential challenges associated with generating and using DNP-enhanced nuclear magnetization in a nanometer-resolution magnetic resonance imaging experiment are elucidated and discussed. PMID:26964007

  3. Beam induced electron cloud resonances in dipole magnetic fields

    NASA Astrophysics Data System (ADS)

    Calvey, J. R.; Hartung, W.; Makita, J.; Venturini, M.

    2016-07-01

    The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple of bunch spacing. Both resonances have been studied directly in dipole fields using retarding field analyzers installed in the Cornell Electron Storage Ring. These measurements are supported by both analytical models and computer simulations.

  4. 29Si nuclear magnetic resonance study of URu2Si2 under pressure

    NASA Astrophysics Data System (ADS)

    Shirer, K. R.; Dioguardi, A. P.; Bush, B. T.; Crocker, J.; Lin, C. H.; Klavins, P.; Cooley, J. C.; Maple, M. B.; Chang, K. B.; Poeppelmeier, K. R.; Curro, N. J.

    2016-01-01

    We report 29Si nuclear magnetic resonance measurements of single crystals and aligned powders of URu2Si2 under pressure in the hidden order and paramagnetic phases. We find that the Knight shift decreases with applied pressure, consistent with previous measurements of the static magnetic susceptibility. Previous measurements of the spin lattice relaxation time revealed a partial suppression of the density of states below 30 K. This suppression persists under pressure, and the onset temperature is mildly enhanced.

  5. Single-pulse resonant magnetic scattering using a soft x-ray free-electron laser

    SciTech Connect

    Gutt, C.; Streit-Nierobisch, S.; Stadler, L.-M.; Faeustlin, R. R.; Treusch, R.; Feldhaus, J.; Weckert, E.; Vartanyants, I. A.; Gruebel, G.; Pfau, B.; Guenther, C. M.; Koennecke, R.; Eisebitt, S.; Froemter, R.; Kobs, A.; Stickler, D.; Oepen, H. P.; Grunze, M.; Rosenhahn, A.; Wilhein, T.

    2010-03-01

    We report on single-pulse resonant magnetic scattering experiments using soft x-ray pulses generated by the free-electron laser FLASH at DESY. We could record a magnetic diffraction pattern from a Co/Pt multilayer sample at the Co M{sub 2,3} edge with a single 30-fs-long FEL pulse. The analysis of the magnetic small-angle scattering signal for subsequent pulses indicates a threshold energy density below which there is no indication that the magnetic properties of the sample might be altered.

  6. Broadband electrically detected magnetic resonance using adiabatic pulses.

    PubMed

    Hrubesch, F M; Braunbeck, G; Voss, A; Stutzmann, M; Brandt, M S

    2015-05-01

    We present a broadband microwave setup for electrically detected magnetic resonance (EDMR) based on microwave antennae with the ability to apply arbitrarily shaped pulses for the excitation of electron spin resonance (ESR) and nuclear magnetic resonance (NMR) of spin ensembles. This setup uses non-resonant stripline structures for on-chip microwave delivery and is demonstrated to work in the frequency range from 4 MHz to 18 GHz. π pulse times of 50 ns and 70 μs for ESR and NMR transitions, respectively, are achieved with as little as 100 mW of microwave or radiofrequency power. The use of adiabatic pulses fully compensates for the microwave magnetic field inhomogeneity of the stripline antennae, as demonstrated with the help of BIR4 unitary rotation pulses driving the ESR transition of neutral phosphorus donors in silicon and the NMR transitions of ionized phosphorus donors as detected by electron nuclear double resonance (ENDOR). PMID:25828243

  7. Resonant Raman scattering from silicon nanoparticles enhanced by magnetic response.

    PubMed

    Dmitriev, Pavel A; Baranov, Denis G; Milichko, Valentin A; Makarov, Sergey V; Mukhin, Ivan S; Samusev, Anton K; Krasnok, Alexander E; Belov, Pavel A; Kivshar, Yuri S

    2016-05-01

    Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions. PMID:27113352

  8. Magnetic Resonance in an Atomic Vapor Excited by a Mechanical Resonator

    NASA Astrophysics Data System (ADS)

    Wang, Ying-Ju; Eardley, Matthew; Knappe, Svenja; Moreland, John; Hollberg, Leo; Kitching, John

    2006-12-01

    We demonstrate a direct resonant interaction between the mechanical motion of a mesoscopic resonator and the spin degrees of freedom of a sample of neutral atoms in the gas phase. This coupling, mediated by a magnetic particle attached to the tip of the miniature mechanical resonator, excites a coherent precession of the atomic spins about a static magnetic field. The novel coupled atom-resonator system may enable development of low-power, high-performance sensors, and enhance research efforts connected with the manipulation of cold atoms, quantum control, and high-resolution microscopy.

  9. Magnetic Resonance Fiber Tracking in a Neonate with Hemimegalencephaly

    PubMed Central

    Re, Thomas J; Scarciolla, Laura; Takahashi, Emi; Specchio, Nicola; Bernardi, Bruno; Longo, Daniela

    2015-01-01

    A magnetic resonance diffusion fiber tracking study in neonate diagnosed with left hemisphere hemimegalencephaly is presented. Despite diffuse morphologic deformities identified in conventional imaging, all major pathways were identifiable bilaterally with minor aberrations in vicinity of morphologic lesions. PMID:25655045

  10. Nuclear magnetic resonance imaging in patients with cardiac pacing devices.

    PubMed

    Buendía, Francisco; Sánchez-Gómez, Juan M; Sancho-Tello, María J; Olagüe, José; Osca, Joaquín; Cano, Oscar; Arnau, Miguel A; Igual, Begoña

    2010-06-01

    Currently, nuclear magnetic resonance imaging is contraindicated in patients with a pacemaker or implantable cardioverter-defibrillator. This study was carried out because the potential risks in this situation need to be clearly defined. This prospective study evaluated clinical and electrical parameters before and after magnetic resonance imaging was performed in 33 patients (five with implantable cardioverter-defibrillators and 28 with pacemakers). In these patients, magnetic resonance imaging was considered clinically essential. There were no clinical complications. There was a temporary communication failure in two cases, sensing errors during imaging in two cases, and a safety signal was generated in one pacemaker at the maximum magnetic resonance frequency and output level. There were no technical restrictions on imaging nor were there any permanent changes in the performance of the cardiac pacing device. PMID:20515632

  11. Imaging agents for in vivo magnetic resonance and scintigraphic imaging

    DOEpatents

    Engelstad, B.L.; Raymond, K.N.; Huberty, J.P.; White, D.L.

    1991-04-23

    Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided. No Drawings

  12. Nuclear Magnetic Double Resonance Using Weak Perturbing RF Fields

    ERIC Educational Resources Information Center

    Reynolds, G. Fredric

    1977-01-01

    Describes a nuclear magnetic resonance experimental example of spin tickling; also discusses a direct approach for verifying the relative signs of coupling constants in three-spin cyclopropyl systems. (SL)

  13. Imaging agents for in vivo magnetic resonance and scintigraphic imaging

    DOEpatents

    Engelstad, Barry L.; Raymond, Kenneth N.; Huberty, John P.; White, David L.

    1991-01-01

    Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided.

  14. 76 FR 58281 - Magnetic Resonance Imaging Safety; Public Workshop

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-20

    ... the safe use of magnetic resonance imaging (MRI) and approaches to mitigate risks. The overall goal is... overview of the Connect Pro program, visit: http://www.adobe.com/go/connectpro_overview . (FDA has...

  15. Diagnosis of hematogenous pyogenic vertebral osteomyelitis by magnetic resonance imaging

    SciTech Connect

    Meyers, S.P.; Wiener, S.N. )

    1991-04-01

    The clinical information and imaging data from 27 patients with hematogenous pyogenic vertebral osteomyelitis were reviewed. All patients had roentgenographic and magnetic resonance imaging examinations. Seventeen patients had computed tomograms; 17 had technetium Tc 99m medronate bone scans; and seven had gallium citrate Ga 67 scans. Magnetic resonance imaging, when used as a part of the initial radiologic evaluation, detected abnormalities consistent with osteomyelitis in all 27 patients. Magnetic resonance imaging also demonstrated paravertebral and/or epidural extension of infection in 14 patients, including seven patients who had neurologic signs of lower-extremity weakness. Roentgenograms, computed tomograms, technetium bone scans, and gallium scans had findings suggestive of the diagnosis in 48%, 65%, 71%, and 86% of the patients, respectively. We recommend magnetic resonance imaging as an important and perhaps critical imaging modality for detection of pyogenic vertebral osteomyelitis.

  16. [Magnetic resonance tomography in injuries of the cervical spine].

    PubMed

    Meydam, K; Sehlen, S; Schlenkhoff, D; Kiricuta, J C; Beyer, H K

    1986-12-01

    Twenty patients who had suffered spinal trauma were examined by magnetic resonance tomography. Fifteen patients with first degree trauma in Erdmann's classification showed no abnormality. Magnetic resonance tomography of the cervical spine appears to be a suitable method for investigating patients with whiplash injuries. It is indicated following severe flexion injuries with subluxations and neurological symptoms, since it is the only method that can demonstrate the spinal cord directly and completely and show the extent of cord compression. For patients with thoracic trauma and rapidly developing neurological symptoms, magnetic resonance tomography is ideal for showing post-traumatic syringomyelia. Magnetic resonance tomography following whiplash injuries is recommended if plain films of the cervical spine show any abnormalities, as well as for the investigation of acute or sub-acute neurological abnormalities. The various findings are discussed. PMID:3025951

  17. Inhalant-Abuse Myocarditis Diagnosed by Cardiac Magnetic Resonance

    PubMed Central

    Rao, Krishnasree; Matulevicius, Susan

    2016-01-01

    Multiple reports of toxic myocarditis from inhalant abuse have been reported. We now report the case of a 23-year-old man found to have toxic myocarditis from inhalation of a hydrocarbon. The diagnosis was made by means of cardiac magnetic resonance imaging with delayed enhancement. The use of cardiac magnetic resonance to diagnose myocarditis has become increasingly common in clinical medicine, although there is not a universally accepted criterion for diagnosis. We appear to be the first to document a case of toxic myocarditis diagnosed by cardiac magnetic resonance. In patients with a history of drug abuse who present with clinical findings that suggest myocarditis or pericarditis, cardiac magnetic resonance can be considered to support the diagnosis. PMID:27303242

  18. Nonlinear magnetization dynamics of antiferromagnetic spin resonance induced by intense terahertz magnetic field

    NASA Astrophysics Data System (ADS)

    Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

    2016-01-01

    We report on the nonlinear magnetization dynamics of a HoFeO3 crystal induced by a strong terahertz magnetic field resonantly enhanced with a split ring resonator and measured with magneto-optical Kerr effect microscopy. The terahertz magnetic field induces a large change (˜40%) in the spontaneous magnetization. The frequency of the antiferromagnetic resonance decreases in proportion to the square of the magnetization change. A modified Landau-Lifshitz-Gilbert equation with a phenomenological nonlinear damping term quantitatively reproduced the nonlinear dynamics.

  19. Use of Magnetic Resonance in the Evaluation of Cranial Trauma.

    PubMed

    Altmeyer, Wilson; Steven, Andrew; Gutierrez, Juan

    2016-05-01

    MR imaging is an extremely useful tool in the evaluation of traumatic brain injury in the emergency department. Although CT still plays the dominant role in urgent patient triage, MR imaging's impact on traumatic brain injury imaging continues to expand. MR imaging has shown superiority to CT for certain traumatic processes, such as diffuse axonal injury, cerebral contusion, and infarction. Magnetic resonance angiography and magnetic resonance venography allow emergent vascular imaging for patients that should avoid ionizing radiation or intravenous contrast. PMID:27150321

  20. Recent advances in cardiac magnetic resonance

    PubMed Central

    Greulich, Simon; Arai, Andrew E.; Sechtem, Udo; Mahrholdt, Heiko

    2016-01-01

    Cardiac magnetic resonance (CMR) is a non-invasive imaging modality that has rapidly emerged during the last few years and has become a valuable, well-established clinical tool. Beside the evaluation of anatomy and function, CMR has its strengths in providing detailed non-invasive myocardial tissue characterization, for which it is considered the current diagnostic gold standard. Late gadolinium enhancement (LGE), with its capability to detect necrosis and to separate ischemic from non-ischemic cardiomyopathies by distinct LGE patterns, offers unique clinical possibilities. The presence of LGE has also proven to be a good predictor of an adverse outcome in various studies. T2-weighted (T2w) images, which are supposed to identify areas of edema and inflammation, are another CMR approach to tissue characterization. However, T2w images have not held their promise owing to several technical limitations and potential physiological concerns. Newer mapping techniques may overcome some of these limitations: they assess quantitatively myocardial tissue properties in absolute terms and show promising results in studies for characterization of diffuse fibrosis (T1 mapping) and/or inflammatory processes (T2 mapping). However, these techniques are still research tools and are not part of the clinical routine yet. T2* CMR has had significant impact in the management of thalassemia because it is possible to image the amount of iron in the heart and the liver, improving both diagnostic imaging and the management of patients with thalassemia. CMR findings frequently have clinical impact on further patient management, and CMR seems to be cost effective in the clinical routine.

  1. Wide-range dynamic magnetic resonance elastography.

    PubMed

    Riek, Kerstin; Klatt, Dieter; Nuzha, Hassan; Mueller, Susanne; Neumann, Ulf; Sack, Ingolf; Braun, Jürgen

    2011-04-29

    Tissue mechanical parameters have been shown to be highly sensitive to disease by elastography. Magnetic resonance elastography (MRE) in the human body relies on the low-dynamic range of tissue mechanics <100 Hz. In contrast, MRE suited for investigations of mice or small tissue samples requires vibration frequencies 10-20 times higher than those used in human MRE. The dispersion of the complex shear modulus (G(⁎)) prevents direct comparison of elastography data at different frequency bands and, consequently, frequency-independent viscoelastic models that fit to G(*) over a wide dynamic range have to be employed. This study presents data of G(*) of samples of agarose gel, liver, brain, and muscle measured by high-resolution MRE in a 7T-animal scanner at 200-800 Hz vibration frequency. Material constants μ and α according to the springpot model and related to shear elasticity and slope of the G(*)-dispersion were determined. Both μ and α of calf brain and bovine liver were found to be similar, while a sample of fibrotic human liver (METAVIR score of 3) displayed about fifteen times higher shear elasticity, similar to μ of bovine muscle measured in muscle fiber direction. α was the highest in fibrotic liver, followed by normal brain and liver, while muscle had the lowest α-values of all biological samples investigated in this study. As expected, the least G(*)-dispersion was seen in soft gel. The proposed technique of wide-range dynamic MRE can provide baseline data for both human MRE and high-dynamic MRE for better understanding tissue mechanics of different tissue structures. PMID:21295305

  2. Fetal magnetic resonance imaging in obstetric practice

    PubMed Central

    Köşüş, Aydın; Köşüş, Nermin; Usluoğulları, Betül; Duran, Müzeyyen; Turhan, Nilgün Öztürk; Tekşam, Mehmet

    2011-01-01

    Ultrasonography (USG) is the primary imaging method for prenatal diagnosis of fetal abnormalities since its discovery. Although it is the primary method of fetal imaging, it cannot provide sufficient information about the fetus in some conditions such as maternal obesity, oligohydramnios and engagement of the fetal head. At this stage, magnetic resonance imaging (MRI) facilitates examination by providing more specific information. The need and importance of fetal MRI applications further increased by the intrauterine surgery which is currently gaining popularity. Some advantages of fetal MRI over USG are the good texture of contrast, a greater study area and visualization of the lesion and neighbourhood relations, independence of the operators. Also it is not affected by maternal obesity and severe oligohydramnios. However, MRI is inadequate in detecting fetal limb and cardiac abnormalities when compared to USG. MRI is not used routinely in pregnancy. It is used in situations where nonionizing imaging methods are inadequate or ionizing radiation is required in pregnant women. It is not recommended during the first trimester. Contrast agent (Godalinium) is not used during pregnancy. It is believed that MRI is not harmful to the fetus, although the biological risk of MRI application is not known. MRI technique is superior to USG in the detection of corpus callosum dysgenesis, third-trimester evaluation of posterior fossa malformations, bilateral renal agenesis, diaphragmatic hernia and assessment of lung maturation. Especially, it is the method of choice for evaluation of central nervous system (CNS) abnormalities. Fetal MRI has a complementary role with USG. It provides important information for prenatal diagnosis, increases diagnostic accuracy, and in turn affects the prenatal treatment, prenatal interventions and birth plan. PMID:24591956

  3. Functional magnetic resonance imaging of the lung.

    PubMed

    Biederer, J; Heussel, C P; Puderbach, M; Wielpuetz, M O

    2014-02-01

    Beyond being a substitute for X-ray, computed tomography, and scintigraphy, magnetic resonance imaging (MRI) inherently combines morphologic and functional information more than any other technology. Lung perfusion: The most established method is first-pass contrast-enhanced imaging with bolus injection of gadolinium chelates and time-resolved gradient-echo (GRE) sequences covering the whole lung (1 volume/s). Images are evaluated visually or semiquantitatively, while absolute quantification remains challenging due to the nonlinear relation of T1-shortening and contrast material concentration. Noncontrast-enhanced perfusion imaging is still experimental, either based on arterial spin labeling or Fourier decomposition. The latter is used to separate high- and low-frequency oscillations of lung signal related to the effects of pulsatile blood flow. Lung ventilation: Using contrast-enhanced first-pass perfusion, lung ventilation deficits are indirectly identified by hypoxic vasoconstriction. More direct but still experimental approaches use either inhalation of pure oxygen, an aerosolized contrast agent, or hyperpolarized noble gases. Fourier decomposition MRI based on the low-frequency lung signal oscillation allows for visualization of ventilation without any contrast agent. Respiratory mechanics: Time-resolved series with high background signal such as GRE or steady-state free precession visualize the movement of chest wall, diaphragm, mediastinum, lung tissue, tracheal wall, and tumor. The assessment of volume changes allows drawing conclusions on regional ventilation. With this arsenal of functional imaging capabilities at high spatial and temporal resolution but without radiation burden, MRI will find its role in regional functional lung analysis and will therefore overcome the sensitivity of global lung function analysis for repeated short-term treatment monitoring. PMID:24481761

  4. Magnetic Resonance Imaging in Postprostatectomy Radiotherapy Planning

    SciTech Connect

    Sefrova, Jana; Odrazka, Karel; Paluska, Petr; Belobradek, Zdenek; Brodak, Milos; Dolezel, Martin; Prosvic, Petr; Macingova, Zuzana; Vosmik, Milan; Hoffmann, Petr; Louda, Miroslav; Nejedla, Anna

    2012-02-01

    Purpose: To investigate whether the use of magnetic resonance imaging (MRI) in prostate bed treatment planning could influence definition of the clinical target volume (CTV) and organs at risk. Methods and Materials: A total of 21 consecutive patients referred for prostate bed radiotherapy were included in the present retrospective study. The CTV was delineated according to the European Organization for Research and Treatment of Cancer recommendations on computed tomography (CT) and T{sub 1}-weighted (T{sub 1}w) and T{sub 2}-weighted (T{sub 2}w) MRI. The CTV magnitude, agreement, and spatial differences were evaluated on the planning CT scan after registration with the MRI scans. Results: The CTV was significantly reduced on the T{sub 1}w and T{sub 2}w MRI scans (13% and 9%, respectively) compared with the CT scans. The urinary bladder was drawn smaller on the CT scans and the rectum was smaller on the MRI scans. On T{sub 1}w MRI, the rectum and urinary bladder were delineated larger than on T{sub 2}w MRI. Minimal agreement was observed between the CT and T{sub 2}w images. The main spatial differences were measured in the superior and superolateral directions in which the CTV on the MRI scans was 1.8-2.9 mm smaller. In the posterior and inferior border, no difference was seen between the CT and T{sub 1}w MRI scans. On the T{sub 2}w MRI scans, the CTV was larger in these directions (by 1.3 and 1.7 mm, respectively). Conclusions: The use of MRI in postprostatectomy radiotherapy planning resulted in a reduction of the CTV. The main differences were found in the superior part of the prostate bed. We believe T{sub 2}w MRI enables more precise definition of prostate bed CTV than conventional planning CT.

  5. 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

  6. Fetal magnetic resonance imaging in obstetric practice.

    PubMed

    Köşüş, Aydın; Köşüş, Nermin; Usluoğulları, Betül; Duran, Müzeyyen; Turhan, Nilgün Öztürk; Tekşam, Mehmet

    2011-01-01

    Ultrasonography (USG) is the primary imaging method for prenatal diagnosis of fetal abnormalities since its discovery. Although it is the primary method of fetal imaging, it cannot provide sufficient information about the fetus in some conditions such as maternal obesity, oligohydramnios and engagement of the fetal head. At this stage, magnetic resonance imaging (MRI) facilitates examination by providing more specific information. The need and importance of fetal MRI applications further increased by the intrauterine surgery which is currently gaining popularity. Some advantages of fetal MRI over USG are the good texture of contrast, a greater study area and visualization of the lesion and neighbourhood relations, independence of the operators. Also it is not affected by maternal obesity and severe oligohydramnios. However, MRI is inadequate in detecting fetal limb and cardiac abnormalities when compared to USG. MRI is not used routinely in pregnancy. It is used in situations where nonionizing imaging methods are inadequate or ionizing radiation is required in pregnant women. It is not recommended during the first trimester. Contrast agent (Godalinium) is not used during pregnancy. It is believed that MRI is not harmful to the fetus, although the biological risk of MRI application is not known. MRI technique is superior to USG in the detection of corpus callosum dysgenesis, third-trimester evaluation of posterior fossa malformations, bilateral renal agenesis, diaphragmatic hernia and assessment of lung maturation. Especially, it is the method of choice for evaluation of central nervous system (CNS) abnormalities. Fetal MRI has a complementary role with USG. It provides important information for prenatal diagnosis, increases diagnostic accuracy, and in turn affects the prenatal treatment, prenatal interventions and birth plan. PMID:24591956

  7. Magnetic Resonance Imaging–guided Vascular Interventions

    PubMed Central

    Ozturk, Cengizhan; Guttman, Michael; McVeigh, Elliot R.; Lederman, Robert J.

    2007-01-01

    Magnetic resonance imaging (MRI), which provides superior soft-tissue imaging and no known harmful effects, has the potential as an alternative modality to guide various medical interventions. This review will focus on MR-guided endovascular interventions and present its current state and future outlook. In the first technical part, enabling technologies such as developments in fast imaging, catheter devices, and visualization techniques are examined. This is followed by a clinical survey that includes proof-of-concept procedures in animals and initial experience in human subjects. In preclinical experiments, MRI has already proven to be valuable. For example, MRI has been used to guide and track targeted cell delivery into or around myocardial infarctions, to guide atrial septal puncture, and to guide the connection of portal and systemic venous circulations. Several investigational MR-guided procedures have already been reported in patients, such as MR-guided cardiac catheterization, invasive imaging of peripheral artery atheromata, selective intraarterial MR angiography, and preliminary angioplasty and stent placement. In addition, MR-assisted transjugular intrahepatic portosystemic shunt procedures in patients have been shown in a novel hybrid double-doughnut x-ray/MRI system. Numerous additional investigational human MR-guided endovascular procedures are now underway in several medical centers around the world. There are also significant hurdles: availability of clinical-grade devices, device-related safety issues, challenges to patient monitoring, and acoustic noise during imaging. The potential of endovascular interventional MRI is great because as a single modality, it combines 3-dimensional anatomic imaging, device localization, hemodynamics, tissue composition, and function. PMID:16924170

  8. Small Animal Imaging with Magnetic Resonance Microscopy

    PubMed Central

    Driehuys, Bastiaan; Nouls, John; Badea, Alexandra; Bucholz, Elizabeth; Ghaghada, Ketan; Petiet, Alexandra; Hedlund, Laurence W.

    2009-01-01

    Small animal magnetic resonance microscopy (MRM) has evolved significantly from testing the boundaries of imaging physics to its expanding use today as a tool in non-invasive biomedical investigations. This review is intended to capture the state-of-the-art in MRM for scientists who may be unfamiliar with this modality, but who want to apply its capabilities to their research. We therefore include a brief review of MR concepts and methods of animal handling and support before covering a range of MRM applications including the heart, lung, brain, and the emerging field of MR histology. High-resolution anatomical imaging reveals increasingly exquisite detail in healthy animals and subtle architectural aberrations that occur in genetically altered models. Resolution of 100 µm in all dimensions is now routinely attained in living animals, and 10 µm3 is feasible in fixed specimens. Such images almost rival conventional histology while allowing the object to be viewed interactively in any plane. MRM is now increasingly used to provide functional information in living animals. Images of the beating heart, breathing lung, and functioning brain can be recorded. While clinical MRI focuses on diagnosis, MRM is used to reveal fundamental biology or to non-invasively measure subtle changes in the structure or function of organs during disease progression or in response to experimental therapies. The ability of MRM to provide a detailed functional and anatomical picture in rats and mice, and to track this picture over time, makes it a promising platform with broad applications in biomedical research. PMID:18172332

  9. Pressure-driven amplification and penetration of resonant magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Loizu, J.; Hudson, S. R.; Helander, P.; Lazerson, S. A.; Bhattacharjee, A.

    2016-05-01

    We show that a resonant magnetic perturbation applied to the boundary of an ideal plasma screw-pinch equilibrium with nested surfaces can penetrate inside the resonant surface and into the core. The response is significantly amplified with increasing plasma pressure. We present a rigorous verification of nonlinear equilibrium codes against linear theory, showing excellent agreement.

  10. Single-spin measurements for quantum computation using magnetic resonance force microscopy

    SciTech Connect

    Berman, G. P.; Borgonovi, F.; Rinkevicius, Z.; Tsifrinovich, V. I.

    2004-01-01

    The quantum theory of a singlespin measurements using a magnetic resonance force microscopy is presented. We use an oscillating cantilever-driven adiabatic reversals technique. The frequency shift of the cantilever vibrations is estimated. We show that the frequency shift causes the formation of the Schroedinger cat state for the cantilever. The interaction between the cantilever and the environment quickly destroys the coherence between the two cantilever trajectories. It is shown that using partial adiabatic reversals one can obtain a significant increase in the frequency shift. We discuss the possibility of sub-magneton spin density detection in molecules using magnetic resonance force microscopy.

  11. Patellar tendinitis: the significance of magnetic resonance imaging findings.

    PubMed

    Shalaby, M; Almekinders, L C

    1999-01-01

    We evaluated the significance of magnetic resonance imaging findings in patients with patellar tendinitis. Midline sagittal magnetic resonance images were taken of 12 knees from 10 patients and of 17 knees from 15 age- and activity-matched subjects who underwent imaging for reasons other than patellar tendinitis. Of the 12 magnetic resonance imaging scans of knees with clinical patellar tendinitis, 3 (25%) exhibited no defect and only 7 (58%) had unequivocal intratendinous lesions. Among the 17 scans of subjects without clinical patellar tendinitis, 5 (34%) showed no defect and 4 (24%) had unequivocal intratendinous lesions. Proximal tendon width was significantly larger for the tendinitis patient group (5.0 +/- 1.7 mm versus 3.9 +/- 1.0 mm), although considerable overlap was present. All subjects with unequivocal intratendinous signal changes had a significantly longer nonarticular inferior patellar pole and were significantly older (38.1 years versus 26.8 years). Only Blazina stage III lesions were associated with abnormal findings on magnetic resonance imaging. As a whole, the sensitivity and specificity of magnetic resonance imaging was 75% and 29%, respectively. In younger patients with relatively mild symptoms, magnetic resonance imaging did not show significant changes; in older, active patients changes may be present in asymptomatic knees. PMID:10352771

  12. Probe-Sample Coupling in the Magnetic Resonance Force Microscope

    NASA Astrophysics Data System (ADS)

    Suter, A.; Pelekhov, D. V.; Roukes, M. L.; Hammel, P. C.

    2002-02-01

    The magnetic resonance force microscope (MRFM) provides a route to achieving scanned probe magnetic resonance imaging with extremely high spatial resolution. Achieving this capability will require understanding the force exerted on a microscopic magnetic probe by a spatially extended sample over which the probe is scanned. Here we present a detailed analysis of this interaction between probe and sample. We focus on understanding the situation where the micromagnet mounted on the mechanical resonator generates a very inhomogeneous magnetic field and is scanned over a sample with at least one spatial dimension much larger than that of the micromagnet. This situation differs quite significantly from the conditions under which most MRFM experiments have been carried out where the sample is mounted on the mechanical resonator and placed in a rather weak magnetic field gradient. In addition to the concept of a sensitive slice (the spatial region where the magnetic resonance condition is met) it is valuable to map the forces exerted on the probe by spins at various locations; this leads to the concept of the force slice (the region in which spins exert force on the resonator). Results of this analysis, obtained both analytically and numerically, will be qualitatively compared with an initial experimental finding from an EPR-MRFM experiment carried out on DPPH at 4 K.

  13. Probe--sample coupling in the magnetic resonance force microscope.

    PubMed

    Suter, A; Pelekhov, D V; Roukes, M L; Hammel, P C

    2002-02-01

    The magnetic resonance force microscope (MRFM) provides a route to achieving scanned probe magnetic resonance imaging with extremely high spatial resolution. Achieving this capability will require understanding the force exerted on a microscopic magnetic probe by a spatially extended sample over which the probe is scanned. Here we present a detailed analysis of this interaction between probe and sample. We focus on understanding the situation where the micromagnet mounted on the mechanical resonator generates a very inhomogeneous magnetic field and is scanned over a sample with at least one spatial dimension much larger than that of the micromagnet. This situation differs quite significantly from the conditions under which most MRFM experiments have been carried out where the sample is mounted on the mechanical resonator and placed in a rather weak magnetic field gradient. In addition to the concept of a sensitive slice (the spatial region where the magnetic resonance condition is met) it is valuable to map the forces exerted on the probe by spins at various locations; this leads to the concept of the force slice (the region in which spins exert force on the resonator). Results of this analysis, obtained both analytically and numerically, will be qualitatively compared with an initial experimental finding from an EPR-MRFM experiment carried out on DPPH at 4 K. PMID:11846579

  14. Single Molecule Magnetic Force Detection with a Carbon Nanotube Resonator

    NASA Astrophysics Data System (ADS)

    Willick, Kyle; Walker, Sean; Baugh, Jonathan

    2015-03-01

    Single molecule magnets (SMMs) sit at the boundary between macroscopic magnetic behaviour and quantum phenomena. Detecting the magnetic moment of an individual SMM would allow exploration of this boundary, and could enable technological applications based on SMMs such as quantum information processing. Detection of these magnetic moments remains an experimental challenge, particularly at the time scales of relaxation and decoherence. We present a technique for sensitive magnetic force detection that should permit such measurements. A suspended carbon nanotube (CNT) mechanical resonator is combined with a magnetic field gradient generated by a ferromagnetic gate electrode, which couples the magnetic moment of a nanomagnet to the resonant motion of the CNT. Numerical calculations of the mechanical resonance show that resonant frequency shifts on the order of a few kHz arise due to single Bohr magneton changes in magnetic moment. A signal-to-noise analysis based on thermomechanical noise shows that magnetic switching at the level of a Bohr magneton can be measured in a single shot on timescales as short as 10 μs. This sensitivity should enable studies of the spin dynamics of an isolated SMM, within the spin relaxation timescales for many available SMMs. Supported by NSERC.

  15. Ferromagnetic resonance in ϵ-Co magnetic composites.

    PubMed

    Chalapat, Khattiya; Timonen, Jaakko V I; Huuppola, Maija; Koponen, Lari; Johans, Christoffer; Ras, Robin H A; Ikkala, Olli; Oksanen, Markku A; Seppälä, Eira; Paraoanu, G S

    2014-12-01

    We investigate the electromagnetic properties of assemblies of nanoscale ϵ-cobalt crystals with size range between 5 to 35 nm, embedded in a polystyrene matrix, at microwave (1-12 GHz) frequencies. We investigate the samples by transmission electron microscopy imaging, demonstrating that the particles aggregate and form chains and clusters. By using a broadband coaxial-line method, we extract the magnetic permeability in the frequency range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance (FMR) with respect to an externally applied magnetic field. We find that the zero-magnetic field ferromagnetic resonant peak shifts towards higher frequencies at finite magnetic fields, and the magnitude of complex permeability is reduced. At fields larger than 2.5 kOe the resonant frequency changes linearly with the applied magnetic field, demonstrating the transition to a state in which the nanoparticles become dynamically decoupled. In this regime, the particles inside clusters can be treated as non-interacting, and the peak position can be predicted from Kittel's FMR theory for non-interacting uniaxial spherical particles combined with the Landau-Lifshitz-Gilbert equation. In contrast, at low magnetic fields this magnetic order breaks down and the resonant frequency in zero magnetic field reaches a saturation value reflecting the interparticle interactions as resulting from aggregation. Our results show that the electromagnetic properties of these composite materials can be tuned by external magnetic fields and by changes in the aggregation structure. PMID:25397945

  16. Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion

    NASA Astrophysics Data System (ADS)

    Elkins, Christopher J.; Alley, Marcus T.

    2007-12-01

    Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for clinical imaging. Velocities can be measured along single lines, in planes, or in full 3D volumes with sub-millimeter resolution. No optical access or flow markers are required so measurements can be obtained in clear or opaque MR compatible flow models and fluids. Because of its versatility and the widespread availability of MRI scanners, MRV is seeing increasing application in both biological and engineering flows. MRV measurements typically image the hydrogen protons in liquid flows due to the relatively high intrinsic signal-to-noise ratio (SNR). Nonetheless, lower SNR applications such as fluorine gas flows are beginning to appear in the literature. MRV can be used in laminar and turbulent flows, single and multiphase flows, and even non-isothermal flows. In addition to measuring mean velocity, MRI techniques can measure turbulent velocities, diffusion coefficients and tensors, and temperature. This review surveys recent developments in MRI measurement techniques primarily in turbulent liquid and gas flows. A general description of MRV provides background for a discussion of its accuracy and limitations. Techniques for decreasing scan time such as parallel imaging and partial k-space sampling are discussed. MRV applications are reviewed in the areas of physiology, biology, and engineering. Included are measurements of arterial blood flow and gas flow in human lungs. Featured engineering applications include the scanning of turbulent flows in complex geometries for CFD validation, the rapid iterative design of complex internal flow passages, velocity and phase composition measurements in

  17. Magnetically-controlled Fano resonance in wavefunction-coupled QPCs

    NASA Astrophysics Data System (ADS)

    Kang, Myoung-Gu

    In this thesis, we describe the observation of a resonant interaction between coupled quantum point contacts (QPCs) that we attribute to a Fano resonance, caused by the self-consistent formation of a bound-state (BS) in one of the QPCs. The presence of this BS (in the "swept QPC") is detected by making measurements of the conductance of the other QPC, which therefore serves as a detector. A key feature of our work is the demonstration of a strong modulation of the detector resonance by applying a perpendicular magnetic field (B⊥). This induces a distinct asymmetry (with respect to magnetic-field reversal) in the magneto-conductance of the detector, which is shown to be due to the influence magnetic electron focusing. In this effect, the electron trajectories correspond to classical skipping orbits, which undergo complete motion due to the high mobility of the two-dimensional electron gas. At even higher B⊥, the detector resonance, which at zero magnetic field is only weakly asymmetric, evolves into the classic, highly asymmetric, Fano form. Such asymmetry indicates that the nonresonant contribution to detector resonance becomes comparable to the resonant one at high fields. We explain these results in terms of two key properties of quantum-dot eigenstates in a magnetic field, namely: the tendency for their wavefunctions to be compressed towards the center of the quantum-dot potential, and; that for their eigenenergies to increase due to the associated enhancement in the effective degree of confinement. In this thesis, we confirm these ideas by performing a Fock-Darwin analysis to account for the evolution of the detector Fano resonance in the magnetic field. The strong modulations of the Fano resonance that we observe as a function of B⊥ are shown to represent a new manifestation of this ubiquitous resonance.

  18. Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design

    SciTech Connect

    Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki; Bouchard, Louis-S.

    2008-03-27

    Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

  19. Electron paramagnetic resonance of nitroxide-doped magnetic fluids

    NASA Astrophysics Data System (ADS)

    Morais, P. C.; Alonso, A.; Silva, O.; Buske, N.

    2002-11-01

    Electron paramagnetic resonance was used to investigate surface-coated magnetite-based magnetic fluids doped with TEMPOL. Two magnetic fluid samples, having magnetite nanoparticles with average diameter of 94 Å and coated with different coating layers (lauric acid plus ethoxylated polyalcohol in one case and oleoylsarcosine in the other case), were doped with TEMPOL (6 mM and pH 7.4) and investigated as a function of the nanoparticle concentration. The resonance field and the resonance linewidth both scale linearly with the nanoparticle concentration.

  20. Magnetic Resonance Imaging (MRI): Dynamic Pelvic Floor

    MedlinePlus

    ... a powerful magnetic field, radio waves and a computer to produce detailed pictures of the pelvic floor, ... powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, ...

  1. Resonant Raman scattering from silicon nanoparticles enhanced by magnetic response

    NASA Astrophysics Data System (ADS)

    Dmitriev, Pavel A.; Baranov, Denis G.; Milichko, Valentin A.; Makarov, Sergey V.; Mukhin, Ivan S.; Samusev, Anton K.; Krasnok, Alexander E.; Belov, Pavel A.; Kivshar, Yuri S.

    2016-05-01

    Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions.Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07965a

  2. High-Resolution Nuclear Magnetic Resonance of Solids.

    ERIC Educational Resources Information Center

    Maciel, Gary E.

    1984-01-01

    Examines recent developments in techniques for obtaining high-resolution nuclear magnetic resonance (NMR) spectra on solid samples, discussing the kinds of applications for which these techniques are well suited. Also discusses the characteristics of NMR of solids and generating magnetization for NMR in solids. (JN)

  3. The Nobel Prize in Medicine for Magnetic Resonance Imaging

    ERIC Educational Resources Information Center

    Fry, Charles G.

    2004-01-01

    Nobel Prize in Medicine awarded in December 2003 to chemist Paul C. Lauterbur and physicist Peter Mansfield for the development of magnetic resonance imaging (MRI), a long overdue recognition of the huge impact MRI has had in medical diagnostics and research is mentioned. MRI was derived, and remains an extension of nuclear magnetic resonance…

  4. Parametric resonance induced chaos in magnetic damped driven pendulum

    NASA Astrophysics Data System (ADS)

    Khomeriki, Giorgi

    2016-07-01

    A damped driven pendulum with a magnetic driving force, appearing from a solenoid, where ac current flows is considered. The solenoid acts on the magnet, which is located at a free end of the pendulum. In this system the existence and interrelation of chaos and parametric resonance is theoretically examined. Derived analytical results are supported by numerical simulations and conducted experiments.

  5. Terahertz Magnetic Mirror Realized with Dielectric Resonator Antennas.

    PubMed

    Headland, Daniel; Nirantar, Shruti; Withayachumnankul, Withawat; Gutruf, Philipp; Abbott, Derek; Bhaskaran, Madhu; Fumeaux, Christophe; Sriram, Sharath

    2015-11-25

    Single-crystal silicon is bonded to a metal-coated substrate and etched in order to form an array of microcylinder passive terahertz dielectric resonator antennas (DRAs). The DRAs exhibit a magnetic response, and hence the array behaves as an efficient artificial magnetic conductor (AMC), with potential for terahertz antenna and sensing applications. PMID:26450363

  6. Nuclear Magnetic Resonance Study of High Temperature Superconductivity

    NASA Astrophysics Data System (ADS)

    Mounce, Andrew M.

    The high temperature superconductors HgBa2CuO 4+delta (Hg1201) and Bi2SrCa2Cu2O 8+delta (Bi2212) have been treated with 17O for both nuclear magnetic resonance (NMR) sensitivity and various electronic properties. Subsequently, NMR experiments were performed on Hg1201 and Bi2212 to reveal the nature of the pseudogap, in the normal state, and vortex phases, in the superconducting state. NMR has been performed on 17O in an underdoped Hg1201 crystal with a superconducting transition transition temperature of 74 K to look for circulating orbital currents proposed theoretically and inferred from neutron scattering. The measurements reveal narrow spectra which preclude static local fields in the pseudogap phase at the apical site, suggesting that the moments observed with neutrons are fluctuating or the orbital current ordering is not the correct model for the neutron scattering observation. The fine detail of the NMR frequency shifts at the apical oxygen site are consistent with a dipolar field from the Cu+2 site and diamagnetism below the superconducting transition. It has been predicted that superconducting vortices should be electrically charged and that this effect is particularly enhanced for high temperature superconductors. Here it is shown that the Abrikosov vortex lattice, characteristic of the mixed state of superconductors, will become unstable at sufficiently high magnetic field if there is charge trapped on the vortex core for highly anisotropic superconductors. NMR measurements of the magnetic fields generated by vortices in Bi2212 single crystals provide evidence for an electro-statically driven vortex lattice reconstruction with the magnitude of charge on each vortex pancake of 2x10-3e, depending on doping, in line with theoretical estimates. Competition with magnetism is at the heart of high temperature superconductivity, most intensely felt near a vortex core. To investigate vortex magnetism spatially resolved NMR has been used, finding a strongly non

  7. Structure of magnetic resonance in 87Rb atoms

    NASA Astrophysics Data System (ADS)

    Kozlov, A. N.; Zibrov, S. A.; Zibrov, A. A.; Yudin, V. I.; Taichenachev, A. V.; Yakovlev, V. P.; Tsygankov, E. A.; Zibrov, A. S.; Vassiliev, V. V.; Velichansky, V. L.

    2016-05-01

    Magnetic resonance at the F g = 1 rightleftarrows F e = 1 transition of the D 1 line in 87Rb has been studied with pumping and detection by linearly polarized radiation and detection at the double frequency of the radiofrequency field. The intervals of allowed values of the static and alternating magnetic fields in which magnetic resonance has a single maximum have been found. The structure appearing beyond these intervals has been explained. It has been shown that the quadratic Zeeman shift is responsible for the three-peak structure of resonance; the radiofrequency shift results in the appearance of additional extrema in resonance, which can be used to determine the relaxation constant Γ2. The possibility of application in magnetometry has been discussed.

  8. Tunable resonant transmission of electromagnetic waves through a magnetized plasma.

    PubMed

    Kee, Chul-Sik; Li, Shou-Zhe; Kim, Kihong; Lim, H

    2003-03-01

    We theoretically investigate the resonant transmission of circularly polarized electromagnetic waves in the electromagnetic stop band of a magnetized plasma slab using the invariant embedding method. The frequency and quality factor of the resonant mode for the right-handed (left-handed) circularly polarized wave created by inserting a dielectric layer into the plasma increase (decrease) as the magnitude of the external magnetic field increases. These phenomena are compared with the characteristics of resonant modes in metallic and dielectric Fabry-Perot resonators to show that they are due to the change of plasma reflectivity. We also discuss the damping effect due to the collisions of the constituent particles of the plasma on the resonant transmission of circularly polarized waves. PMID:12689184

  9. Aggregation of magnetic microparticles in the context of targeted therapies actuated by a magnetic resonance imaging system

    NASA Astrophysics Data System (ADS)

    Mathieu, Jean-Baptiste; Martel, Sylvain

    2009-08-01

    A study of magnetic aggregation in the context of magnetic resonance imaging (MRI) based actuated targeting is proposed. MRI systems can induce displacement forces on magnetized particles as they flow through the blood vessels. Magnetic aggregation of the particles happens when they are placed within the magnetic field of the MRI system and can greatly influence the MRI steering dynamics of magnetic particles. In this paper, a review of the different parameters that can be used to tailor the size, geometry, stiffness, and density of magnetic aggregates is proposed. Then, magnetic aggregation experiments on a suspension of Fe3O4 microparticles ranging from 0.1 to 100 μm in diameter are described. The effects of particle concentration, flow rate, and magnetic field amplitude were evaluated. Field amplitudes of 1.5 mT, 0.4 T, and 1.5 T fields were applied without any magnetic steering gradients and caused aggregates that could sometimes exceed 1 mm in length. Since magnetic aggregates can reach higher magnetophoretic velocities than individual particles, large aggregates could be exploited in larger arteries with important blood flows. A few strategies are discussed to assist in the design of MRI steering experiments by enhancing the positive effects of magnetic aggregation over its negative effects.

  10. Accelerated nanoscale magnetic resonance imaging through phase multiplexing

    SciTech Connect

    Moores, B. A.; Eichler, A. Takahashi, H.; Navaretti, P.; Degen, C. L.; Tao, Y.

    2015-05-25

    We report a method for accelerated nanoscale nuclear magnetic resonance imaging by detecting several signals in parallel. Our technique relies on phase multiplexing, where the signals from different nuclear spin ensembles are encoded in the phase of an ultrasensitive magnetic detector. We demonstrate this technique by simultaneously acquiring statistically polarized spin signals from two different nuclear species ({sup 1}H, {sup 19}F) and from up to six spatial locations in a nanowire test sample using a magnetic resonance force microscope. We obtain one-dimensional imaging resolution better than 5 nm, and subnanometer positional accuracy.

  11. Accelerated nanoscale magnetic resonance imaging through phase multiplexing

    NASA Astrophysics Data System (ADS)

    Moores, B. A.; Eichler, A.; Tao, Y.; Takahashi, H.; Navaretti, P.; Degen, C. L.

    2015-05-01

    We report a method for accelerated nanoscale nuclear magnetic resonance imaging by detecting several signals in parallel. Our technique relies on phase multiplexing, where the signals from different nuclear spin ensembles are encoded in the phase of an ultrasensitive magnetic detector. We demonstrate this technique by simultaneously acquiring statistically polarized spin signals from two different nuclear species (1H, 19F) and from up to six spatial locations in a nanowire test sample using a magnetic resonance force microscope. We obtain one-dimensional imaging resolution better than 5 nm, and subnanometer positional accuracy.

  12. Spin wave resonance detection using magnetic tunnel junction structure

    NASA Astrophysics Data System (ADS)

    Bi, Chong; Fan, Xin; Pan, Liqing; Kou, Xiaoming; Wu, Jun; Yang, Qinghui; Zhang, Huaiwu; Xiao, John Q.

    2011-11-01

    We have demonstrated that spin wave resonance in a permalloy microstrip can be detected by an electrical method based on magnetic tunnel junction structures. The detection method promises high spatial resolution and sensitivity. Both even and odd spin wave resonance modes can be clearly observed in a permalloy microstrip. The spin wave induced voltage is proportional to the input microwave power at each resonance mode. Data analysis using the model of quantized dipole-exchange spin wave resonance suggests the edge pinning of spin wave sensitively depends on the order of the spin wave mode, as well as on the excitation frequency for modes of the higher order.

  13. Nuclear magnetic resonance studies of macroscopic morphology and dynamics

    SciTech Connect

    Barrall, G A

    1995-09-01

    Nuclear magnetic resonance techniques are traditionally used to study molecular level structure and dynamics with a noted exception in medically applied NMR imaging (MRI). In this work, new experimental methods and theory are presented relevant to the study of macroscopic morphology and dynamics using NMR field gradient techniques and solid state two-dimensional exchange NMR. The goal in this work is not to take some particular system and study it in great detail, rather it is to show the utility of a number of new and novel techniques using ideal systems primarily as a proof of principle. By taking advantage of the analogy between NMR imaging and diffraction, one may simplify the experiments necessary for characterizing the statistical properties of the sample morphology. For a sample composed of many small features, e.g. a porous medium, the NMR diffraction techniques take advantage of both the narrow spatial range and spatial isotropy of the sample`s density autocorrelation function to obtain high resolution structural information in considerably less time than that required by conventional NMR imaging approaches. The time savings of the technique indicates that NMR diffraction is capable of finer spatial resolution than conventional NMR imaging techniques. Radio frequency NMR imaging with a coaxial resonator represents the first use of cylindrically symmetric field gradients in imaging. The apparatus as built has achieved resolution at the micron level for water samples, and has the potential to be very useful in the imaging of circularly symmetric systems. The study of displacement probability densities in flow through a random porous medium has revealed the presence of features related to the interconnectedness of the void volumes. The pulsed gradient techniques used have proven successful at measuring flow properties for time and length scales considerably shorter than those studied by more conventional techniques.

  14. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-11-10

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  15. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2010-06-29

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  16. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2010-07-13

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  17. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-10-27

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  18. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2007-12-11

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  19. Catheter steering using a Magnetic Resonance Imaging system.

    PubMed

    Lalande, Viviane; Gosselin, Frederick P; Martel, Sylvain

    2010-01-01

    A catheter is successfully bent and steered by applying magnetic gradients inside a Magnetic Resonance Imaging system (MRI). One to three soft ferromagnetic spheres are attached at the distal tip of the catheter with different spacing between the spheres. Depending on the interactions between the spheres, progressive or discontinuous/jumping displacement was observed for increasing magnetic load. This phenomenon is accurately predicted by a simple theoretical dipole interaction model. PMID:21096567

  20. Quantum transport in coupled resonators enclosed synthetic magnetic flux

    NASA Astrophysics Data System (ADS)

    Jin, L.

    2016-07-01

    Quantum transport properties are instrumental to understanding quantum coherent transport processes. Potential applications of quantum transport are widespread, in areas ranging from quantum information science to quantum engineering, and not restricted to quantum state transfer, control and manipulation. Here, we study light transport in a ring array of coupled resonators enclosed synthetic magnetic flux. The ring configuration, with an arbitrary number of resonators embedded, forms a two-arm Aharonov-Bohm interferometer. The influence of magnetic flux on light transport is investigated. Tuning the magnetic flux can lead to resonant transmission, while half-integer magnetic flux quantum leads to completely destructive interference and transmission zeros in an interferometer with two equal arms.

  1. Nuclear magnetic resonance spectroscopy with single spin sensitivity

    PubMed Central

    Müller, C.; Kong, X.; Cai, J.-M.; Melentijević, K.; Stacey, A.; Markham, M.; Twitchen, D.; Isoya, J.; Pezzagna, S.; Meijer, J.; Du, J. F.; Plenio, M. B.; Naydenov, B.; McGuinness, L. P.; Jelezko, F.

    2014-01-01

    Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen–vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four 29Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503

  2. Nuclear magnetic resonance spectroscopy with single spin sensitivity.

    PubMed

    Müller, C; Kong, X; Cai, J-M; Melentijević, K; Stacey, A; Markham, M; Twitchen, D; Isoya, J; Pezzagna, S; Meijer, J; Du, J F; Plenio, M B; Naydenov, B; McGuinness, L P; Jelezko, F

    2014-01-01

    Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen-vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four (29)Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503

  3. Magnetic field amplification in nonlinear diffusive shock acceleration including resonant and non-resonant cosmic-ray driven instabilities

    SciTech Connect

    Bykov, Andrei M.; Osipov, Sergei M.; Ellison, Donald C.; Vladimirov, Andrey E. E-mail: osm2004@mail.ru E-mail: avenovo@gmail.com

    2014-07-10

    We present a nonlinear Monte Carlo model of efficient diffusive shock acceleration where the magnetic turbulence responsible for particle diffusion is calculated self-consistently from the resonant cosmic-ray (CR) streaming instability, together with non-resonant short- and long-wavelength CR-current-driven instabilities. We include the backpressure from CRs interacting with the strongly amplified magnetic turbulence which decelerates and heats the super-Alfvénic flow in the extended shock precursor. Uniquely, in our plane-parallel, steady-state, multi-scale model, the full range of particles, from thermal (∼eV) injected at the viscous subshock to the escape of the highest energy CRs (∼PeV) from the shock precursor, are calculated consistently with the shock structure, precursor heating, magnetic field amplification, and scattering center drift relative to the background plasma. In addition, we show how the cascade of turbulence to shorter wavelengths influences the total shock compression, the downstream proton temperature, the magnetic fluctuation spectra, and accelerated particle spectra. A parameter survey is included where we vary shock parameters, the mode of magnetic turbulence generation, and turbulence cascading. From our survey results, we obtain scaling relations for the maximum particle momentum and amplified magnetic field as functions of shock speed, ambient density, and shock size.

  4. Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy Characterize a Rodent Model of Covert Stroke

    NASA Astrophysics Data System (ADS)

    Herrera, Sheryl Lyn

    Covert stroke (CS) comprises lesions in the brain often associated by risk factors such as a diet high in fat, salt, cholesterol and sugar (HFSCS). Developing a rodent model for CS incorporating these characteristics is useful for developing and testing interventions. The purpose of this thesis was to determine if magnetic resonance (MR) can detect brain abnormalities to confirm this model will have the desired anatomical effects. Ex vivo MR showed brain abnormalities for rats with the induced lesions and fed the HFSCS diet. Spectra acquired on the fixed livers had an average percent area under the fat peak relative to the water peak of (20+/-4)% for HFSCS and (2+/-2)% for control. In vivo MR images had significant differences between surgeries to induce the lesions (p=0.04). These results show that applying MR identified abnormalities in the rat model and therefore is important in the development of this CS rodent model.

  5. Towards Single Biomolecule Imaging via Optical Nanoscale Magnetic Resonance Imaging.

    PubMed

    Boretti, Alberto; Rosa, Lorenzo; Castelletto, Stefania

    2015-09-01

    Nuclear magnetic resonance (NMR) spectroscopy is a physical marvel in which electromagnetic radiation is charged and discharged by nuclei in a magnetic field. In conventional NMR, the specific nuclei resonance frequency depends on the strength of the magnetic field and the magnetic properties of the isotope of the atoms. NMR is routinely utilized in clinical tests by converting nuclear spectroscopy in magnetic resonance imaging (MRI) and providing 3D, noninvasive biological imaging. While this technique has revolutionized biomedical science, measuring the magnetic resonance spectrum of single biomolecules is still an intangible aspiration, due to MRI resolution being limited to tens of micrometers. MRI and NMR have, however, recently greatly advanced, with many breakthroughs in nano-NMR and nano-MRI spurred by using spin sensors based on an atomic impurities in diamond. These techniques rely on magnetic dipole-dipole interactions rather than inductive detection. Here, novel nano-MRI methods based on nitrogen vacancy centers in diamond are highlighted, that provide a solution to the imaging of single biomolecules with nanoscale resolution in-vivo and in ambient conditions. PMID:26113221

  6. Comparison of nuclear electric resonance and nuclear magnetic resonance in integer and fractional quantum Hall states

    SciTech Connect

    Tomimatsu, Toru Shirai, Shota; Hashimoto, Katsushi Sato, Ken; Hirayama, Yoshiro

    2015-08-15

    Electric-field-induced nuclear resonance (NER: nuclear electric resonance) involving quantum Hall states (QHSs) was studied at various filling factors by exploiting changes in nuclear spins polarized at quantum Hall breakdown. Distinct from the magnetic dipole interaction in nuclear magnetic resonance, the interaction of the electric-field gradient with the electric quadrupole moment plays the dominant role in the NER mechanism. The magnitude of the NER signal strongly depends on whether electronic states are localized or extended. This indicates that NER is sensitive to the screening capability of the electric field associated with QHSs.

  7. Ionospheric Electron Density during Magnetically Active Times over Istanbul

    NASA Astrophysics Data System (ADS)

    Naz Erbaş, Bute; Kaymaz, Zerefsan; Ceren Moral, Aysegul; Emine Ceren Kalafatoglu Eyiguler, R. A..

    2016-07-01

    In this study, we analyze electron density variations over Istanbul using Dynasonde observations during the magnetically active times. In order to perform statistical analyses, we first determined magnetic storms and magnetospheric substorm intervals from October 2012 to October 2015 using Kyoto's magnetic index data. Corresponding ionospheric parameters, such as critical frequency of F2 region (foF2), maximum electron density height (hmF2), total electron density (TEC) etc. were retrieved from Dynasonde data base at Istanbul Technical University's Space Weather Laboratory. To understand the behavior of electron density during the magnetically active times, we remove the background quiet time variations first and then quantify the anomalies. In this presentation, we will report results from our preliminary analyses from the selected cases corresponding to the strong magnetic storms. Initial results show lower electron densities at noon times and higher electron densities in the late afternoon toward sunset times when compared to the electron densities of magnetically quiet times. We also compare the results with IRI and TIEGCM ionospheric models in order to understand the physical and dynamical causes of these variations. During the presentation we will also discuss the role of these changes during the magnetically active times on the GPS communications through ionosphere.

  8. Three-dimensional magnetic recording using ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Suto, Hirofumi; Kudo, Kiwamu; Nagasawa, Tazumi; Kanao, Taro; Mizushima, Koichi; Sato, Rie

    2016-07-01

    To meet the ever-increasing demand for data storage, future magnetic recording devices will need to be made three-dimensional by implementing multilayer recording. In this article, we present methods of detecting and manipulating the magnetization direction of a specific layer selectively in a vertically stacked multilayer magnetic system, which enable layer-selective read and write operations in three-dimensional magnetic recording devices. The principle behind the methods is ferromagnetic resonance excitation in a microwave magnetic field. By designing each magnetic recording layer to have a different ferromagnetic resonance frequency, magnetization excitation can be induced individually in each layer by tuning the frequency of an applied microwave magnetic field, and this selective magnetization excitation can be utilized for the layer-selective operations. Regarding media for three-dimensional recording, when layers of a perpendicular magnetic material are vertically stacked, dipolar interaction between multiple recording layers arises and is expected to cause problems, such as degradation of thermal stability and switching field distribution. To solve these problems, we propose the use of an antiferromagnetically coupled structure consisting of hard and soft magnetic layers. Because the stray fields from these two layers cancel each other, antiferromagnetically coupled media can reduce the dipolar interaction.

  9. Magnetic Resonance Imaging Studies of Postpartum Depression: An Overview

    PubMed Central

    Fiorelli, Marco; Aceti, Franca; Marini, Isabella; Giacchetti, Nicoletta; Macci, Enrica; Tinelli, Emanuele; Calistri, Valentina; Meuti, Valentina; Caramia, Francesca; Biondi, Massimo

    2015-01-01

    Postpartum depression is a frequent and disabling condition whose pathophysiology is still unclear. In recent years, the study of the neural correlates of mental disorders has been increasingly approached using magnetic resonance techniques. In this review we synthesize the results from studies on postpartum depression in the context of structural, functional, and spectroscopic magnetic resonance studies of major depression as a whole. Compared to the relative wealth of data available for major depression, magnetic resonance studies of postpartum depression are limited in number and design. A systematic literature search yielded only eleven studies conducted on about one hundred mothers with postpartum depression overall. Brain magnetic resonance findings in postpartum depression appear to replicate those obtained in major depression, with minor deviations that are not sufficient to delineate a distinct neurobiological profile for this condition, due to the small samples used and the lack of direct comparisons with subjects with major depression. However, it seems reasonable to expect that studies conducted in larger populations, and using a larger variety of brain magnetic resonance techniques than has been done so far, might allow for the identification of neuroimaging signatures for postpartum depression. PMID:26347585

  10. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

    2015-03-01

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

  11. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    SciTech Connect

    Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Woo, Eung Je; Kwon, Oh In

    2015-03-14

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as B{sub z}. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple B{sub z} data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured B{sub z} data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

  12. Hyperpolarized Xenon-129 Magnetic Resonance Imaging of Functional Lung Microstructure

    NASA Astrophysics Data System (ADS)

    Dregely, Isabel

    Hyperpolarized 129Xe (HXe) is a non-invasive contrast agent for lung magnetic resonance imaging (MRI), which upon inhalation follows the functional pathway of oxygen in the lung by dissolving into lung tissue structures and entering the blood stream. HXe MRI therefore provides unique opportunities for functional lung imaging of gas exchange which occurs from alveolar air spaces across the air-blood boundary into parenchymal tissue. However challenges in acquisition speed and signal-to-noise ratio have limited the development of a HXe imaging biomarker to diagnose lung disease. This thesis addresses these challenges by introducing parallel imaging to HXe MRI. Parallel imaging requires dedicated hardware. This work describes design, implementation, and characterization of a 32-channel phased-array chest receive coil with an integrated asymmetric birdcage transmit coil tuned to the HXe resonance on a 3 Tesla MRI system. Using the newly developed human chest coil, a functional HXe imaging method, multiple exchange time xenon magnetization transfer contrast (MXTC) is implemented. MXTC dynamically encodes HXe gas exchange into the image contrast. This permits two parameters to be derived regionally which are related to gas-exchange functionality by characterizing tissue-to-alveolar-volume ratio and alveolar wall thickness in the lung parenchyma. Initial results in healthy subjects demonstrate the sensitivity of MXTC by quantifying the subtle changes in lung microstructure in response to orientation and lung inflation. Our results in subjects with lung disease show that the MXTC-derived functional tissue density parameter exhibits excellent agreement with established imaging techniques. The newly developed dynamic parameter, which characterizes the alveolar wall, was elevated in subjects with lung disease, most likely indicating parenchymal inflammation. In light of these observations we believe that MXTC has potential as a biomarker for the regional quantification of 1

  13. High-Sensitivity Measurement of Density by Magnetic Levitation.

    PubMed

    Nemiroski, Alex; Kumar, A A; Soh, Siowling; Harburg, Daniel V; Yu, Hai-Dong; Whitesides, George M

    2016-03-01

    This paper presents methods that use Magnetic Levitation (MagLev) to measure very small differences in density of solid diamagnetic objects suspended in a paramagnetic medium. Previous work in this field has shown that, while it is a convenient method, standard MagLev (i.e., where the direction of magnetization and gravitational force are parallel) cannot resolve differences in density <10(-4) g/cm(3) for macroscopic objects (>mm) because (i) objects close in density prevent each other from reaching an equilibrium height due to hard contact and excluded volume, and (ii) using weaker magnets or reducing the magnetic susceptibility of the medium destabilizes the magnetic trap. The present work investigates the use of weak magnetic gradients parallel to the faces of the magnets as a means of increasing the sensitivity of MagLev without destabilization. Configuring the MagLev device in a rotated state (i.e., where the direction of magnetization and gravitational force are perpendicular) relative to the standard configuration enables simple measurements along the axes with the highest sensitivity to changes in density. Manipulating the distance of separation between the magnets or the lengths of the magnets (along the axis of measurement) enables the sensitivity to be tuned. These modifications enable an improvement in the resolution up to 100-fold over the standard configuration, and measurements with resolution down to 10(-6) g/cm(3). Three examples of characterizing the small differences in density among samples of materials having ostensibly indistinguishable densities-Nylon spheres, PMMA spheres, and drug spheres-demonstrate the applicability of rotated Maglev to measuring the density of small (0.1-1 mm) objects with high sensitivity. This capability will be useful in materials science, separations, and quality control of manufactured objects. PMID:26815205

  14. Smart-Phone Based Magnetic Levitation for Measuring Densities.

    PubMed

    Knowlton, Stephanie; Yu, Chu Hsiang; Jain, Nupur; Ghiran, Ionita Calin; Tasoglu, Savas

    2015-01-01

    Magnetic levitation, which uses a magnetic field to suspend objects in a fluid, is a powerful and versatile technology. We develop a compact magnetic levitation platform compatible with a smart-phone to separate micro-objects and estimate the density of the sample based on its levitation height. A 3D printed attachment is mechanically installed over the existing camera unit of a smart-phone. Micro-objects, which may be either spherical or irregular in shape, are suspended in a paramagnetic medium and loaded in a microcapillary tube which is then inserted between two permanent magnets. The micro-objects are levitated and confined in the microcapillary at an equilibrium height dependent on their volumetric mass densities (causing a buoyancy force toward the edge of the microcapillary) and magnetic susceptibilities (causing a magnetic force toward the center of the microcapillary) relative to the suspending medium. The smart-phone camera captures magnified images of the levitating micro-objects through an additional lens positioned between the sample and the camera lens cover. A custom-developed Android application then analyzes these images to determine the levitation height and estimate the density. Using this platform, we were able to separate microspheres with varying densities and calibrate their levitation heights to known densities to develop a technique for precise and accurate density estimation. We have also characterized the magnetic field, the optical imaging capabilities, and the thermal state over time of this platform. PMID:26308615

  15. Smart-Phone Based Magnetic Levitation for Measuring Densities

    PubMed Central

    Knowlton, Stephanie; Yu, Chu Hsiang; Jain, Nupur

    2015-01-01

    Magnetic levitation, which uses a magnetic field to suspend objects in a fluid, is a powerful and versatile technology. We develop a compact magnetic levitation platform compatible with a smart-phone to separate micro-objects and estimate the density of the sample based on its levitation height. A 3D printed attachment is mechanically installed over the existing camera unit of a smart-phone. Micro-objects, which may be either spherical or irregular in shape, are suspended in a paramagnetic medium and loaded in a microcapillary tube which is then inserted between two permanent magnets. The micro-objects are levitated and confined in the microcapillary at an equilibrium height dependent on their volumetric mass densities (causing a buoyancy force toward the edge of the microcapillary) and magnetic susceptibilities (causing a magnetic force toward the center of the microcapillary) relative to the suspending medium. The smart-phone camera captures magnified images of the levitating micro-objects through an additional lens positioned between the sample and the camera lens cover. A custom-developed Android application then analyzes these images to determine the levitation height and estimate the density. Using this platform, we were able to separate microspheres with varying densities and calibrate their levitation heights to known densities to develop a technique for precise and accurate density estimation. We have also characterized the magnetic field, the optical imaging capabilities, and the thermal state over time of this platform. PMID:26308615

  16. Magnetic resonance imaging--first human images in Australia.

    PubMed

    Baddeley, H; Doddrell, D M; Brooks, W M; Field, J; Irving, M; Williams, J E

    1986-10-20

    The use of magnetic resonance imaging, in the demonstration of internal human anatomy and in the diagnosis of disease, has the major advantages that the technique is noninvasive, does not require the use of ionizing radiation and that it can demonstrate neurological and cardiovascular lesions that cannot be diagnosed easily by other imaging methods. Magnetic resonance imaging is derived from the principle that certain atomic nuclei in a strong magnetic field will absorb pulses of radiofrequency energy; when the pulse is finished the nuclei will emit radiowaves at the same frequency. These radiowaves are received by specially designed aerials or coils and the information is collected by a computer which reconstructs an image of internal anatomy in a similar way to that of x-ray computed tomography (CT). By changing the strength of the magnetic fields and the frequency of the radiowave pulses, it is possible to examine different sections within the body. The first magnetic resonance images of humans were obtained in Australia in October 1985 on the research instrument of the Queensland Medical Magnetic Resonance Research Centre, which is based at the Mater Hospital in Brisbane, and is part of the University of Queensland's Department of Radiology. PMID:3020385

  17. Edge localized mode control with an edge resonant magnetic perturbation

    SciTech Connect

    Moyer, R.A.; Boedo, J.A.; Rudakov, D.L.; Evans, T.E.; Osborne, T.H.; Gohil, P.; Groebner, R.J.; Jackson, G.L.; La Haye, R.J.; Leonard, A.W.; Schaffer, M.J.; Snyder, P.B.; West, W.P.; Thomas, P.R.; Becoulet, M.; Harris, J.; Finken, K.-H.; Doyle, E.J.; Rhodes, T.L.; Wang, G.

    2005-05-15

    A low amplitude ({delta}b{sub r}/B{sub T}=1 part in 5000) edge resonant magnetic field perturbation with toroidal mode number n=3 and poloidal mode numbers between 8 and 15 has been used to suppress most large type I edge localized modes (ELMs) without degrading core plasma confinement. ELMs have been suppressed for periods of up to 8.6 energy confinement times when the edge safety factor q{sub 95} is between 3.5 and 4. The large ELMs are replaced by packets of events (possibly type II ELMs) with small amplitude, narrow radial extent, and a higher level of magnetic field and density fluctuations, creating a duty cycle with long 'active' intervals of high transport and short 'quiet' intervals of low transport. The increased transport associated with these events is less impulsive and slows the recovery of the pedestal profiles to the values reached just before the large ELMs without the n=3 perturbation. Changing the toroidal phase of the perturbation by 60 deg. with respect to the best ELM suppression case reduces the ELM amplitude and frequency by factors of 2-3 in the divertor, produces a more stochastic response in the H-mode pedestal profiles, and displays similar increases in small scale events, although significant numbers of large ELMs survive. In contrast to the best ELM suppression case where the type I ELMs are also suppressed on the outboard midplane, the midplane recycling increases until individual ELMs are no longer discernable. The ELM response depends on the toroidal phase of the applied perturbation because intrinsic error fields make the target plasma nonaxisymmetric, and suggests that at least some of the variation in ELM behavior in a single device or among different devices is due to differences in the intrinsic error fields in these devices. These results indicate that ELMs can be suppressed by small edge resonant magnetic field perturbations. Extrapolation to next-step burning plasma devices will require extending the regime of operation to

  18. On-wafer magnetic resonance of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Little, Charles A. E.; Russek, Stephen E.; Booth, James C.; Kabos, Pavel; Usselman, Robert J.

    2015-11-01

    Magnetic resonance measurements of ferumoxytol and TEMPO were made using an on-wafer transmission line technique with a vector network analyzer, allowing for broadband measurements of small sample volumes (4 nL) and small numbers of spins (1 nmol). On-wafer resonance measurements were compared with standard single-frequency cavity-based electron paramagnetic resonance (EPR) measurements using a new power conservation approach and the results show similar line shape. On-wafer magnetic resonance measurements using integrated microfluidics and microwave technology can significantly reduce the cost and sample volumes required for EPR spectral analysis and allow for integration of EPR with existing lab-on-a-chip processing and characterization techniques for point-of-care medical diagnostic applications.

  19. Current-induced spin torque resonance of a magnetic insulator

    NASA Astrophysics Data System (ADS)

    Schreier, Michael; Chiba, Takahiro; Niedermayr, Arthur; Lotze, Johannes; Huebl, Hans; Geprägs, Stephan; Takahashi, Saburo; Bauer, Gerrit E. W.; Gross, Rudolf; Goennenwein, Sebastian T. B.

    2015-10-01

    We report the observation of current-induced spin torque resonance in yttrium iron garnet/platinum bilayers. An alternating charge current at GHz frequencies in the platinum gives rise to dc spin pumping and spin Hall magnetoresistance rectification voltages, induced by the Oersted fields of the ac current and the spin Hall effect-mediated spin transfer torque. In ultrathin yttrium iron garnet films, we observe spin transfer torque actuated magnetization dynamics which are significantly larger than those generated by the ac Oersted field. Spin transfer torques thus efficiently couple charge currents and magnetization dynamics also in magnetic insulators, enabling charge current-based interfacing of magnetic insulators with microwave devices.

  20. Resonant Landau-Zener transitions in a helical magnetic field

    NASA Astrophysics Data System (ADS)

    Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

    2015-06-01

    Spin-dependent electron transport has been studied in magnetic semiconductor waveguides (nanowires) in the helical magnetic field. We have shown that—apart from the well-known conductance dip located at the magnetic field equal to the helical-field amplitude Bh—the additional conductance dips (with zero conductance) appear at a magnetic field different from Bh. This effect occurring in the non-adiabatic regime is explained as resulting from the resonant Landau-Zener transitions between the spin-split subbands.

  1. Desktop fast-field cycling nuclear magnetic resonance relaxometer.

    PubMed

    Sousa, Duarte Mesquita; Marques, Gil Domingos; Cascais, José Manuel; Sebastião, Pedro José

    2010-07-01

    In this paper a new type of Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometer with low power consumption (200W) and cycle to cycle field stability better than 10(-4) is described. The new high-permeability magnet was designed to allow for good magnetic field homogeneity and allows for the sample rotation around an axis perpendicular to magnetic field, operating with magnetic fields between 0 and 0.21T. The power supply of the new relaxometer was specially developed in order to have steady state accurate currents and allow for magnetic field switching times less than 3ms. Additional control circuits were developed and included to compensate the Earth magnetic field component parallel to the field axis and to compensate for parasitic currents. The main aspects of the developed circuits together with some calibrating experimental results using the liquid crystal compounds 5CB and 8CB are presented and discussed. PMID:20688489

  2. Anicteric early bile duct carcinoma detection with magnetic resonance cholangiopancreatography.

    PubMed

    Oshikiri, Taro; Morita, Takayuki; Fujita, Miyoshi; Miyasaka, Yuji; Senmaru, Naoto; Yamada, Hidehisa; Kondo, Satoshi; Katoh, Hiroyuki

    2005-01-01

    The poor prognosis of extrahepatic bile duct carcinoma makes early detection and diagnosis essential for positive patient outcomes. We describe 2 cases of jaundice-free early extrahepatic bile duct carcinoma detected by magnetic resonance cholangiopancreatography. Extrahepatic bile duct carcinoma was discovered incidentally in patient 1 by magnetic resonance cholangiopancreatography during evaluation of a gallbladder stone. In patient 2, extrahepatic bile duct carcinoma was found during a routine health maintenance exam. Both patients underwent radical surgical intervention. Both patient 1 and 2 have remained in good health for over one year, 3.5 and one year, respectively, and have not exhibited any signs or symptoms of relapse or cancer recurrence. Based on these cases, it appears that magnetic resonance cholangiopancreatography can play a significant role in the early detection of extrahepatic bile duct carcinoma and improve disease prognosis. PMID:15816438

  3. Renal relevant radiology: renal functional magnetic resonance imaging.

    PubMed

    Ebrahimi, Behzad; Textor, Stephen C; Lerman, Lilach O

    2014-02-01

    Because of its noninvasive nature and provision of quantitative measures of a wide variety of physiologic parameters, functional magnetic resonance imaging (MRI) shows great potential for research and clinical applications. Over the past decade, application of functional MRI extended beyond detection of cerebral activity, and techniques for abdominal functional MRI evolved. Assessment of renal perfusion, glomerular filtration, interstitial diffusion, and parenchymal oxygenation turned this modality into an essential research and potentially diagnostic tool. Variations in many renal physiologic markers can be detected using functional MRI before morphologic changes become evident in anatomic magnetic resonance images. Moreover, the framework of functional MRI opened a window of opportunity to develop novel pathophysiologic markers. This article reviews applications of some well validated functional MRI techniques, including perfusion, diffusion-weighted imaging, and blood oxygen level-dependent MRI, as well as some emerging new techniques such as magnetic resonance elastography, which might evolve into clinically useful tools. PMID:24370767

  4. Magnetic resonance spectroscopy and imaging for the study of fossils.

    PubMed

    Giovannetti, Giulio; Guerrini, Andrea; Salvadori, Piero A

    2016-07-01

    Computed tomography (CT) has long been used for investigating palaeontological specimens, as it is a nondestructive technique which avoids the need to dissolve or ionize the fossil sample. However, magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) have recently gained ground as analytical tools for examination of palaeontological samples, by nondestructively providing information about the structure and composition of fossils. While MRI techniques are able to reveal the three-dimensional geometry of the trace fossil, MRS can provide information on the chemical composition of the samples. The multidimensional nature of MR (magnetic resonance) signals has potential to provide rich three-dimensional data on the palaeontological specimens and also to help in elucidating paleopathological and paleoecological questions. In this work the verified applications and the emerging uses of MRI and MRS in paleontology are reviewed, with particular attention to fossil spores, fossil plants, ambers, fossil invertebrates, and fossil vertebrate studies. PMID:26979538

  5. Magnetic-resonance pore imaging of nonsymmetric microscopic pore shapes

    NASA Astrophysics Data System (ADS)

    Hertel, Stefan Andreas; Wang, Xindi; Hosking, Peter; Simpson, M. Cather; Hunter, Mark; Galvosas, Petrik

    2015-07-01

    Imaging of the microstructure of porous media such as biological tissue or porous solids is of high interest in health science and technology, engineering and material science. Magnetic resonance pore imaging (MRPI) is a recent technique based on nuclear magnetic resonance (NMR) which allows us to acquire images of the average pore shape in a given sample. Here we provide details on the experimental design, challenges, and requirements of MRPI, including its calibration procedures. Utilizing a laser-machined phantom sample, we present images of microscopic pores with a hemiequilateral triangular shape even in the presence of NMR relaxation effects at the pore walls. We therefore show that MRPI is applicable to porous samples without a priori knowledge about their pore shape and symmetry. Furthermore, we introduce "MRPI mapping," which combines MRPI with conventional magnetic resonance imaging (MRI). This enables one to resolve microscopic pore sizes and shapes spatially, thus expanding the application of MRPI to samples with heterogeneous distributions of pores.

  6. Anatomical, functional and molecular biomarker applications of magnetic resonance neuroimaging

    PubMed Central

    Liu, Christina H

    2015-01-01

    MRI and magnetic resonance spectroscopy (MRS) along with computed tomography and PET are the most common imaging modalities used in the clinics to detect structural abnormalities and pathological conditions in the brain. MRI generates superb image resolution/contrast without radiation exposure that is associated with computed tomography and PET; MRS and spectroscopic imaging technologies allow us to measure changes in brain biochemistry. Increasingly, neurobiologists and MRI scientists are collaborating to solve neuroscience problems across sub-cellular through anatomical levels. To achieve successful cross-disciplinary collaborations, neurobiologists must have sufficient knowledge of magnetic resonance principles and applications in order to effectively communicate with their MRI colleagues. This review provides an overview of magnetic resonance techniques and how they can be used to gain insight into the active brain at the anatomical, functional and molecular levels with the goal of encouraging neurobiologists to include MRI/MRS as a research tool in their endeavors. PMID:25774094

  7. Magnetic Resonance, Functional (fMRI) -- Brain

    MedlinePlus

    ... powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, ... The images can then be examined on a computer monitor, transmitted electronically, printed or copied to a ...

  8. Magnetic anisotropy of polycrystalline magnetoferritin investigated by SQUID and electron magnetic resonance

    NASA Astrophysics Data System (ADS)

    Moro, F.; de Miguel, R.; Jenkins, M.; Gómez-Moreno, C.; Sells, D.; Tuna, F.; McInnes, E. J. L.; Lostao, A.; Luis, F.; van Slageren, J.

    2014-06-01

    Magnetoferritin molecules with an average inorganic core diameter of 5.7±1.6 nm and polycrystalline internal structure were investigated by a combination of transmission electron microscopy, magnetic susceptibility, magnetization, and electron magnetic resonance (EMR) experiments. The temperature and frequency dependence of the magnetic susceptibility allowed for the determination of the magnetic anisotropy on an experimental time scale which spans from seconds to nanoseconds. In addition, angle-dependent EMR experiments were carried out for the determination of the nanoparticle symmetry and internal magnetic field. Due to the large surface to volume ratio, the nanoparticles show larger and uniaxial rather than cubic magnetic anisotropies compared to bulk maghemite and magnetite.

  9. Travelling wave magnetic resonance imaging at 3 T

    NASA Astrophysics Data System (ADS)

    Vazquez, F.; Martin, R.; Marrufo, O.; Rodriguez, A. O.

    2013-08-01

    Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore diameter limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies in magnetic resonance imaging and spectroscopy. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transverse electromagnetic modes and it can propagate any frequency. To study the potential benefits of travelling-wave excitation for whole-body imaging at 3 T, we compare numerical simulations of the principal mode propagation for a parallel-plate waveguide filled with a cylindrical phantom and two surface coils for all simulations at 1.5 T, 3 T, 4.7, 7 T, and 9.4 T. The principal mode shows very little variation of the field magnitude along the propagation direction at 3 T when compared to other higher resonant frequencies. Unlike the standard method for travelling-wave magnetic resonance imaging, a parallel-plate waveguide prototype was built and used together with a whole-body birdcage coil for signal transmission and a pair of circular coils for reception. Experimental B1 mapping was computed to investigate the feasibility of this approach and, the point spread function method was used to measure the imager performance. Human leg images were acquired to experimentally validate this approach. The numerical magnetic field and specific absorption rate of a simulated leg were computed and results are within the safety limits. The B1 mapping and point spread function results showed that it is possible to conduct travelling-wave imaging experiments with good imager performance. Human leg images were also obtained with the whole-body birdcage coil for comparison purposes. The simulated and in vivo travelling-wave results of the human leg correspond very well for the signal received. A similar image signal-to-noise ratio was observed for the

  10. Magnetic resonance imaging in entomology: a critical review

    PubMed Central

    Hart, A.G.; Bowtell, R.W.; Köckenberger, W.; Wenseleers, T.; Ratnieks, F.L.W.

    2003-01-01

    Magnetic resonance imaging (MRI) enables in vivo imaging of organisms. The recent development of the magnetic resonance microscope (MRM) has enabled organisms within the size range of many insects to be imaged. Here, we introduce the principles of MRI and MRM and review their use in entomology. We show that MRM has been successfully applied in studies of parasitology, development, metabolism, biomagnetism and morphology, and the advantages and disadvantages relative to other imaging techniques are discussed. In addition, we illustrate the images that can be obtained using MRM. We conclude that although MRM has significant potential, further improvements to the technique are still desirable if it is to become a mainstream imaging technology in entomology. Abbreviation: CSI chemical shift imaging. The dependence of the resonance frequency of a nucleus on the chemical binding of the atom or molecule in which it is contained. (N)MRI (nuclear) magnetic resonance imaging MRM magnetic resonance microscopy Voxel A contraction for volume element, which is the basic unit of MR reconstruction; represented as a pixel in the display of the MR image. PMID:15841222

  11. Computation of flow pressure fields from magnetic resonance velocity mapping.

    PubMed

    Yang, G Z; Kilner, P J; Wood, N B; Underwood, S R; Firmin, D N

    1996-10-01

    Magnetic resonance phase velocity mapping has unrivalled capacities for acquiring in vivo multi-directional blood flow information. In this study, the authors set out to derive both spatial and temporal components of acceleration, and hence differences of pressure in a flow field using cine magnetic resonance velocity data. An efficient numerical algorithm based on the Navier-Stokes equations for incompressible Newtonian fluid was used. The computational approach was validated with in vitro flow phantoms. This work aims to contribute to a better understanding of cardiovascular dynamics and to serve as a basis for investigating pulsatile pressure/flow relationships associated with normal and impaired cardiovascular function. PMID:8892202

  12. Artifacts and pitfalls in shoulder magnetic resonance imaging*

    PubMed Central

    Marcon, Gustavo Felix; Macedo, Tulio Augusto Alves

    2015-01-01

    Magnetic resonance imaging has revolutionized the diagnosis of shoulder lesions, in many cases becoming the method of choice. However, anatomical variations, artifacts and the particularity of the method may be a source of pitfalls, especially for less experienced radiologists. In order to avoid false-positive and false-negative results, the authors carried out a compilation of imaging findings that may simulate injury. It is the authors’ intention to provide a useful, consistent and comprehensive reference for both beginner residents and skilled radiologists who work with musculoskeletal magnetic resonance imaging, allowing for them to develop more precise reports and helping them to avoid making mistakes. PMID:26379323

  13. Cranial and spinal magnetic resonance imaging: A guide and atlas

    SciTech Connect

    Daniels, D.L.; Haughton, V.M.

    1987-01-01

    This atlas provides a clinical guide to interpreting cranial and spinal magnetic resonance images. The book includes coverage of the cerebrum, temporal bone, and cervical, thoracic, and lumbar spine, with more than 400 scan images depicting both normal anatomy and pathologic findings. Introductory chapters review the practical physics of magnetic resonance (MR) imaging, offer guidelines for interpreting cranial MR scans, and provide coverage of each anatomic region of the cranium and spine. For each region, scans accompanied by captions, show normal anatomic sections matched with MR images. These are followed by MR scans depicting various disease states.

  14. Functional magnetic resonance imaging in medicine and physiology

    SciTech Connect

    Moonen, C.T.W.; van Zijl, P.C.M.; Frank, J.A.; Bihan, D.L.; Becker, E.D. )

    1990-10-05

    Magnetic resonance imaging (MRI) is a well-established diagnostic tool that provides detailed information about macroscopic structure and anatomy. Recent advances in MRI allow the noninvasive spatial evaluation of various biophysical and biochemical processes in living systems. Specifically, the motion of water can be measured in processes such as vascular flow, capillary flow, diffusion, and exchange. In addition, the concentrations of various metabolites can be determined for the assessment of regional regulation of metabolism. Examples are given that demonstrate the use of functional MRI for clinical and research purposes. This development adds a new dimension to the application of magnetic resonance to medicine and physiology.

  15. Malformations of cortical development: 3T magnetic resonance imaging features

    PubMed Central

    Battal, Bilal; Ince, Selami; Akgun, Veysel; Kocaoglu, Murat; Ozcan, Emrah; Tasar, Mustafa

    2015-01-01

    Malformation of cortical development (MCD) is a term representing an inhomogeneous group of central nervous system abnormalities, referring particularly to embriyological aspect as a consequence of any of the three developmental stages, i.e., cell proliferation, cell migration and cortical organization. These include cotical dysgenesis, microcephaly, polymicrogyria, schizencephaly, lissencephaly, hemimegalencephaly, heterotopia and focal cortical dysplasia. Since magnetic resonance imaging is the modality of choice that best identifies the structural anomalies of the brain cortex, we aimed to provide a mini review of MCD by using 3T magnetic resonance scanner images. PMID:26516429

  16. Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface.

    PubMed

    Berggren, P; Fransson, J

    2016-01-01

    We address electron spin resonance of single magnetic moments in a tunnel junction using time-dependent electric fields and spin-polarized current. We show that the tunneling current directly depends on the local magnetic moment and that the frequency of the external electric field mixes with the characteristic Larmor frequency of the local spin. The importance of the spin-polarized current induced anisotropy fields acting on the local spin moment is, moreover, demonstrated. Our proposed model thus explains the absence of an electron spin resonance for a half integer spin, in contrast with the strong signal observed for an integer spin. PMID:27156935

  17. Magnetic Resonance Spectroscopy of siRNA-Based Cancer Therapy

    PubMed Central

    Penet, Marie-France; Chen, Zhihang; Mori, Noriko; Krishnamachary, Balaji; Bhujwalla, Zaver M.

    2016-01-01

    Small interfering RNA (siRNA) is routinely used as a biological tool to silence specific genes, and is under active investigation in cancer treatment strategies. Noninvasive magnetic resonance spectroscopy (MRS) provides the ability to assess the functional effects of siRNA-mediated gene silencing in cultured cancer cells, and following nanoparticle-based delivery in tumors in vivo. Here we describe the use of siRNA to downregulate choline kinase, a critical enzyme in choline phospholipid metabolism of cancer cells and tumors, and the use of 1H MRS of cells and 1H magnetic resonance spectroscopic imaging (MRSI) of tumors to assess the efficacy of the downregulation. PMID:26530913

  18. Magnetic resonance imaging as a tool for extravehicular activity analysis

    NASA Technical Reports Server (NTRS)

    Dickenson, R.; Lorenz, C.; Peterson, S.; Strauss, A.; Main, J.

    1992-01-01

    The purpose of this research is to examine the value of magnetic resonance imaging (MRI) as a means of conducting kinematic studies of the hand for the purpose of EVA capability enhancement. After imaging the subject hand using a magnetic resonance scanner, the resulting 2D slices were reconstructed into a 3D model of the proximal phalanx of the left hand. Using the coordinates of several landmark positions, one is then able to decompose the motion of the rigid body. MRI offers highly accurate measurements due to its tomographic nature without the problems associated with other imaging modalities for in vivo studies.

  19. Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface

    PubMed Central

    Berggren, P.; Fransson, J.

    2016-01-01

    We address electron spin resonance of single magnetic moments in a tunnel junction using time-dependent electric fields and spin-polarized current. We show that the tunneling current directly depends on the local magnetic moment and that the frequency of the external electric field mixes with the characteristic Larmor frequency of the local spin. The importance of the spin-polarized current induced anisotropy fields acting on the local spin moment is, moreover, demonstrated. Our proposed model thus explains the absence of an electron spin resonance for a half integer spin, in contrast with the strong signal observed for an integer spin. PMID:27156935

  20. Magnetic Resonance Imaging: From Spin Physics to Medical Diagnosis

    NASA Astrophysics Data System (ADS)

    Nacher, Pierre-Jean

    Two rather similar historical evolutions are evoked, each one originating in fundamental spin studies by physicists, and ending as magnetic resonance imaging (MRI), a set of invaluable tools for clinical diagnosis in the hands of medical doctors. The first one starts with the early work on nuclear magnetic resonance, the founding stone of the usual proton-based MRI, of which the basic principles are described. The second one starts with the optical pumping developments made to study the effects of spin polarization in various fundamental problems. Its unexpected outcome is a unique imaging modality, also based on MRI, for the study of lung physiology and pathologies.

  1. Algorithmic cooling in liquid-state nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Atia, Yosi; Elias, Yuval; Mor, Tal; Weinstein, Yossi

    2016-01-01

    Algorithmic cooling is a method that employs thermalization to increase qubit purification level; namely, it reduces the qubit system's entropy. We utilized gradient ascent pulse engineering, an optimal control algorithm, to implement algorithmic cooling in liquid-state nuclear magnetic resonance. Various cooling algorithms were applied onto the three qubits of C132-trichloroethylene, cooling the system beyond Shannon's entropy bound in several different ways. In particular, in one experiment a carbon qubit was cooled by a factor of 4.61. This work is a step towards potentially integrating tools of NMR quantum computing into in vivo magnetic-resonance spectroscopy.

  2. Nuclear magnetic resonance in environmental engineering: principles and applications.

    PubMed

    Lens, P N; Hemminga, M A

    1998-01-01

    This paper gives an introduction to nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) in relation to applications in the field of environmental science and engineering. The underlying principles of high resolution solution and solid state NMR, relaxation time measurements and imaging are presented. Then, the use of NMR is illustrated and reviewed in studies of biodegradation and biotransformation of soluble and solid organic matter, removal of nutrients and xenobiotics, fate of heavy metal ions, and transport processes in bioreactor systems. PMID:10335581

  3. Development of magnetic resonance technology for noninvasive boron quantification

    SciTech Connect

    Bradshaw, K.M.

    1990-11-01

    Boron magnetic resonance imaging (MRI) and spectroscopy (MRS) were developed in support of the noninvasive boron quantification task of the Idaho National Engineering Laboratory (INEL) Power Burst Facility/Boron Neutron Capture Therapy (PBF/BNCT) program. The hardware and software described in this report are modifications specific to a GE Signa{trademark} MRI system, release 3.X and are necessary for boron magnetic resonance operation. The technology developed in this task has been applied to obtaining animal pharmacokinetic data of boron compounds (drug time response) and the in-vivo localization of boron in animal tissue noninvasively. 9 refs., 21 figs.

  4. High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

    SciTech Connect

    Adelnia, Fatemeh; Lascialfari, Alessandro; Mariani, Manuel; Ammannato, Luca; Caneschi, Andrea; Rovai, Donella; Winpenny, Richard; Timco, Grigore; Corti, Maurizio Borsa, Ferdinando

    2015-05-07

    We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.

  5. Duffing oscillation-induced reversal of magnetic vortex core by a resonant perpendicular magnetic field

    PubMed Central

    Moon, Kyoung-Woong; Chun, Byong Sun; Kim, Wondong; Qiu, Z. Q.; Hwang, Chanyong

    2014-01-01

    Nonlinear dynamics of the magnetic vortex state in a circular nanodisk was studied under a perpendicular alternating magnetic field that excites the radial modes of the magnetic resonance. Here, we show that as the oscillating frequency is swept down from a frequency higher than the eigenfrequency, the amplitude of the radial mode is almost doubled to the amplitude at the fixed resonance frequency. This amplitude has a hysteresis vs. frequency sweeping direction. Our result showed that this phenomenon was due to a Duffing-type nonlinear resonance. Consequently, the amplitude enhancement reduced the vortex core-switching magnetic field to well below 10 mT. A theoretical model corresponding to the Duffing oscillator was developed from the Landau–Lifshitz–Gilbert equation to explore the physical origin of the simulation result. This work provides a new pathway for the switching of the magnetic vortex core polarity in future magnetic storage devices. PMID:25145837

  6. Duffing oscillation-induced reversal of magnetic vortex core by a resonant perpendicular magnetic field.

    PubMed

    Moon, Kyoung-Woong; Chun, Byong Sun; Kim, Wondong; Qiu, Z Q; Hwang, Chanyong

    2014-01-01

    Nonlinear dynamics of the magnetic vortex state in a circular nanodisk was studied under a perpendicular alternating magnetic field that excites the radial modes of the magnetic resonance. Here, we show that as the oscillating frequency is swept down from a frequency higher than the eigenfrequency, the amplitude of the radial mode is almost doubled to the amplitude at the fixed resonance frequency. This amplitude has a hysteresis vs. frequency sweeping direction. Our result showed that this phenomenon was due to a Duffing-type nonlinear resonance. Consequently, the amplitude enhancement reduced the vortex core-switching magnetic field to well below 10 mT. A theoretical model corresponding to the Duffing oscillator was developed from the Landau-Lifshitz-Gilbert equation to explore the physical origin of the simulation result. This work provides a new pathway for the switching of the magnetic vortex core polarity in future magnetic storage devices. PMID:25145837

  7. Multiple-receptor wireless power transfer for magnetic sensors charging on Mars via magnetic resonant coupling

    NASA Astrophysics Data System (ADS)

    Liu, Chunhua; Chau, K. T.; Zhang, Zhen; Qiu, Chun; Lin, Fei; Ching, T. W.

    2015-05-01

    This paper proposes a new idea for magnetic sensors charging on Mars, which aims to effectively transmit energy from Mars Rover to distributed magnetic sensors. The key is to utilize wireless power transfer (WPT) to enable multiple receptors extracting energy from the source via magnetic resonant coupling. Namely, the energy transmitter is located on the Mars Rover, whereas the energy receptor is installed in the magnetic sensor. In order to effectively transfer the power, a resonator is installed between the transmitter and the receptors. Based on the proposed idea, the system topology, operation principle, and simulation results are developed. By performing finite element magnetic field analysis, the output power and efficiency of the proposed WPT system are evaluated. It confirms that the Mars Rover carrying with the energy transmitter is capable of loitering around the resonator, while the magnetic sensors on the receptors can be simultaneously charged according to energy-on-demand.

  8. Magnetic Resonance Reversals in Optically Pumped Alkali-Metal Vapor

    NASA Astrophysics Data System (ADS)

    Gong, Fei; Jau, Yuan-Yu; Happer, William

    2007-06-01

    We report an unusual new phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the ``zero-dip" resonance (Zeeman resonance at zero field) of optically-pumped, alkali-metal vapors. These anomalies occur when a ``weak" circular polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in simple, semi-quantitative way with reference to this distribution. uantitative computer simulations are in excellent greement with observations.

  9. Magnetic resonance reversals in optically pumped alkali-metal vapor

    NASA Astrophysics Data System (ADS)

    Gong, F.; Jau, Y.-Y.; Happer, W.

    2007-05-01

    We report an unusual phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the zero-dip resonance (Zeeman resonance at zero field) of optically pumped, alkali-metal vapors. These anomalies occur when a weak circularly polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in a simple, semiquantitative way with reference to the spin-temperature distribution. Quantitative computer simulations are in excellent agreement with observations.

  10. Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance

    NASA Astrophysics Data System (ADS)

    Li, Hongyan; Klem, Michael T.; Sebby, Karl B.; Singel, David J.; Young, Mark; Douglas, Trevor; Idzerda, Yves U.

    2009-02-01

    Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles' easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size.

  11. Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.

    2003-01-01

    We pursued advanced technology development of laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This new multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation-as well as studies of tissue perfusion. In addition, laser-polarized noble gases (3He and 129Xe) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We pursued two technology development specific aims: (1) development of low-field (less than 0.01 T) noble gas MRI of humans; and (2) development of functional MRI of the lung using laser-polarized noble gas and related techniques.

  12. Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.

    2001-01-01

    We are developing laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI) (e.g., of lung ventilation) as well as studies of tissue perfusion. In addition, laser-polarized noble gases (He-3 and Xe-129) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We are pursuing two specific aims in this research. The first aim is to develop a low-field (< 0.01 T) instrument for noble gas MRI of humans, and the second aim is to develop functional MRI of the lung using laser-polarized Xe-129 and related techniques.

  13. Magnetization transfer using inversion recovery during off-resonance irradiation

    PubMed Central

    Mangia, Silvia; De Martino, Federico; Liimatainen, Timo; Garwood, Michael; Michaeli, Shalom

    2011-01-01

    Estimation of magnetization transfer (MT) parameters in vivo can be compromised by an inability to drive the magnetization to a steady state using allowable levels of radiofrequency (RF) irradiation, due to safety concerns (tissue heating and specific absorption rate (SAR)). Rather than increasing the RF duration or amplitude, here we propose to circumvent the SAR limitation by sampling the formation of the steady state in separate measurements made with the magnetization initially along the −z and +z axis of the laboratory frame, i.e. with or without an on-resonance inversion pulse prior to the off-resonance irradiation. Results from human brain imaging demonstrate that this choice provides a tremendous benefit in the fitting procedure used to estimate MT parameters. The resulting parametric maps are characterized by notably increased tissue specificity as compared to those obtained with the standard MT acquisition in which magnetization is initially along the +z axis only. PMID:21601405

  14. Magnetization transfer using inversion recovery during off-resonance irradiation.

    PubMed

    Mangia, Silvia; De Martino, Federico; Liimatainen, Timo; Garwood, Michael; Michaeli, Shalom

    2011-12-01

    Estimation of magnetization transfer (MT) parameters in vivo can be compromised by an inability to drive the magnetization to a steady state using allowable levels of radiofrequency (RF) irradiation, due to safety concerns (tissue heating and specific absorption rate (SAR)). Rather than increasing the RF duration or amplitude, here we propose to circumvent the SAR limitation by sampling the formation of the steady state in separate measurements made with the magnetization initially along the -z and +z axis of the laboratory frame, i.e. with or without an on-resonance inversion pulse prior to the off-resonance irradiation. Results from human brain imaging demonstrate that this choice provides a tremendous benefit in the fitting procedure used to estimate MT parameters. The resulting parametric maps are characterized by notably increased tissue specificity as compared to those obtained with the standard MT acquisition in which magnetization is initially along the +z axis only. PMID:21601405

  15. Drift resonance in high density non-neutral plasmas

    NASA Astrophysics Data System (ADS)

    Kaup, D. J.

    2006-05-01

    Theoretical studies of the operation of crossed-field electron vacuum devices such as magnetrons and crossed-field amplifiers (CFA) have usually centered on their initial growth, taking this as an indication of their operating modes. In such an analysis one solves the equations for the density profile, the operating frequency, the growth rate, and other features of these devices. What one really obtains then are only the conditions for the device to turn on. The dominant interaction in this stage is a Rayleigh-type instability which initiates a quasilinear diffusion process whereby the electron density profile redistributes itself into a profile which will be in equilibrium with the ponderomotive-like forces produced by the growing rf fields. Eventually the rf fields will saturate and an operating device will settle into a stationary operating regime. This stage of a device's operation is called the "saturation stage." This latter stage involves a different set of physical interactions from the initiation stage. No longer is there a growth rate; rather the rf amplitudes have saturated and as a result, the ponderomotive-like forces have also vanished along with the quasilinear diffusion. In this saturation stage, we find that new rf modes appear. In fact, there are a total of five rf modes, two of which are the usual slow modes of the initiation stage, and three of which have fast oscillations in the vertical direction. One fast mode corresponds to a drift plasma oscillation while the other two fast modes are drift cyclotron modes. In this paper, we will describe how the drift plasma oscillation interacts and couples with the slow rf modes at the diocotron resonance.

  16. Drift resonance in high density non-neutral plasmas

    SciTech Connect

    Kaup, D.J.

    2006-05-15

    Theoretical studies of the operation of crossed-field electron vacuum devices such as magnetrons and crossed-field amplifiers (CFA) have usually centered on their initial growth, taking this as an indication of their operating modes. In such an analysis one solves the equations for the density profile, the operating frequency, the growth rate, and other features of these devices. What one really obtains then are only the conditions for the device to turn on. The dominant interaction in this stage is a Rayleigh-type instability which initiates a quasilinear diffusion process whereby the electron density profile redistributes itself into a profile which will be in equilibrium with the ponderomotive-like forces produced by the growing rf fields. Eventually the rf fields will saturate and an operating device will settle into a stationary operating regime. This stage of a device's operation is called the ''saturation stage.'' This latter stage involves a different set of physical interactions from the initiation stage. No longer is there a growth rate; rather the rf amplitudes have saturated and as a result, the ponderomotive-like forces have also vanished along with the quasilinear diffusion. In this saturation stage, we find that new rf modes appear. In fact, there are a total of five rf modes, two of which are the usual slow modes of the initiation stage, and three of which have fast oscillations in the vertical direction. One fast mode corresponds to a drift plasma oscillation while the other two fast modes are drift cyclotron modes. In this paper, we will describe how the drift plasma oscillation interacts and couples with the slow rf modes at the diocotron resonance.

  17. A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging

    PubMed Central

    Eguchi, Haruki; Umemura, Masanari; Kurotani, Reiko; Fukumura, Hidenobu; Sato, Itaru; Kim, Jeong-Hwan; Hoshino, Yujiro; Lee, Jin; Amemiya, Naoyuki; Sato, Motohiko; Hirata, Kunio; Singh, David J.; Masuda, Takatsugu; Yamamoto, Masahiro; Urano, Tsutomu; Yoshida, Keiichiro; Tanigaki, Katsumi; Yamamoto, Masaki; Sato, Mamoru; Inoue, Seiichi; Aoki, Ichio; Ishikawa, Yoshihiro

    2015-01-01

    Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies. PMID:25779357

  18. A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging.

    PubMed

    Eguchi, Haruki; Umemura, Masanari; Kurotani, Reiko; Fukumura, Hidenobu; Sato, Itaru; Kim, Jeong-Hwan; Hoshino, Yujiro; Lee, Jin; Amemiya, Naoyuki; Sato, Motohiko; Hirata, Kunio; Singh, David J; Masuda, Takatsugu; Yamamoto, Masahiro; Urano, Tsutomu; Yoshida, Keiichiro; Tanigaki, Katsumi; Yamamoto, Masaki; Sato, Mamoru; Inoue, Seiichi; Aoki, Ichio; Ishikawa, Yoshihiro

    2015-01-01

    Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies. PMID:25779357

  19. A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Eguchi, Haruki; Umemura, Masanari; Kurotani, Reiko; Fukumura, Hidenobu; Sato, Itaru; Kim, Jeong-Hwan; Hoshino, Yujiro; Lee, Jin; Amemiya, Naoyuki; Sato, Motohiko; Hirata, Kunio; Singh, David J.; Masuda, Takatsugu; Yamamoto, Masahiro; Urano, Tsutomu; Yoshida, Keiichiro; Tanigaki, Katsumi; Yamamoto, Masaki; Sato, Mamoru; Inoue, Seiichi; Aoki, Ichio; Ishikawa, Yoshihiro

    2015-03-01

    Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies.

  20. Magnetic resonance imaging and contrast enhancement. Scientific report

    SciTech Connect

    Swenberg, C.E.; Movius, E.G.

    1988-01-01

    Chapters II through VI of this report discuss: Relaxation of Nuclear Spins; Echo Techniques; Basic Imaging Pulse Sequences; Partial Saturation Recovery; Inversion Recovery; Spin Echo; Effects of Pulse Sequence on Image Contrast; Contrast Agents; Theoretical Aspects; Pharmacokinetics and Toxicity; and Physiological Rationale for Agent Selection. One of the major goals in all medical imaging techniques is to maximize one's ability to visualize and differentiate adjacent tissue regions in the body on the basis of differences in anatomy, physiology, or various pathological processes. Magnetic resonance (MR) imaging offers distinct advantages over conventional x-ray imaging because of the possibility of selecting specific pulse sequences that can differentiate adjacent structures on the basis of differences in proton density, T/sub 1/ or T/sub 2/ relaxation rates, or flow. As a result of applying these various pulse sequences, numerous images have been obtained of the brain and other organs that demonstrate considerably more-detailed anatomical structure than had previously been available with computerized tomography, ultrasound, or nuclear medicine techniques. In some situations it is clearly superior, such as in the diagnosis of multiple sclerosis.

  1. Application of Medical Magnetic Resonance Imaging for Particle Concentration Measurement

    NASA Astrophysics Data System (ADS)

    Borup, Daniel; Elkins, Christopher; Eaton, John

    2014-11-01

    Particle transport and deposition in internal flows is important in a range of applications such as dust aggregation in turbine engines and aerosolized medicine deposition in human airways. Unlike optical techniques, Magnetic Resonance Imaging (MRI) is well suited for complex applications in which optical access is not possible. Here we present efforts to measure 3D particle concentration distribution using MRI. Glass particles dispersed in water flow reduce MRI signal from a spin-echo or gradient-echo scanning sequence by decreasing spin density and dephasing the spins present in the fluid. A preliminary experiment was conducted with a particle streak injected at the centerline of a turbulent round pipe flow with a U bend. Measurements confirmed that signal strength was related to particle concentration and showed the effects of gravitational settling and turbulent dispersion. Next, measurements of samples in a mixing chamber were taken. Particle volume fraction was varied and sensitivity to particle/fluid velocity was investigated. These results give a relationship between MRI signal, particle volume fraction, MRI sequence echo time, and spin relaxation parameters that can be used to measure local particle volume fraction in other turbulent flows of interest.

  2. Spherical tensor analysis of nuclear magnetic resonance signals.

    PubMed

    van Beek, Jacco D; Carravetta, Marina; Antonioli, Gian Carlo; Levitt, Malcolm H

    2005-06-22

    In a nuclear magnetic-resonance (NMR) experiment, the spin density operator may be regarded as a superposition of irreducible spherical tensor operators. Each of these spin operators evolves during the NMR experiment and may give rise to an NMR signal at a later time. The NMR signal at the end of a pulse sequence may, therefore, be regarded as a superposition of spherical components, each derived from a different spherical tensor operator. We describe an experimental method, called spherical tensor analysis (STA), which allows the complete resolution of the NMR signal into its individual spherical components. The method is demonstrated on a powder of a (13)C-labeled amino acid, exposed to a pulse sequence generating a double-quantum effective Hamiltonian. The propagation of spin order through the space of spherical tensor operators is revealed by the STA procedure, both in static and rotating solids. Possible applications of STA to the NMR of liquids, liquid crystals, and solids are discussed. PMID:16035785

  3. Ultra-fast parallel magnetic resonance imaging of granular systems

    NASA Astrophysics Data System (ADS)

    Penn, Alexander; Pruessmann, Klaas P.; Müller, Christoph

    2015-03-01

    Several non-intrusive techniques have been applied to probe the dynamics of two-phase granular systems, with the most prominent examples being X-ray tomography, positron emission particle tracking (PEPT), electrical capacitance tomography and magnetic resonance imaging (MRI). MRI comes with the particular advantage that by implementing suitable pulse sequences not only spin densities (i.e. voidage), but also velocity, acceleration, diffusion and chemical reactions can be measured. However, so far the investigation of two-phase granular systems has been performed on relatively small-bore systems (max. diameter 60 mm). Such systems are, however, heavily influenced by wall effects. Furthermore, largely only single-coil detection has been employed, limiting severely the temporal resolution of the data acquisition. Here, we report the acquisition of ultra-fast MRI measurements in large volume vessels using medical MRI scanners. Specifically, parallel MRI, i.e. the simultaneous use of multiple receiver coils, has been exploited to speed up the data acquisition. In combination with advanced pulse sequences, we were able to probe the rapid dynamics (voidage and velocity measurements) of gas-solid systems.

  4. Probing arrays of circular magnetic microdots by ferromagnetic resonance.

    SciTech Connect

    Kakazei, G. N.; Mewes, T.; Wigen, P. E.; Hammel, P. C.; Slavin, A. N.; Pogorelov, Y. G.; Costa, M. D.; Golub, V. O.; Guslienko, K. Y.; Novosad, V.

    2008-06-01

    X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field H(r) was found when the interdot distance a gets comparable to the dot diameter D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patterned magnetic structure. It is well described by an iterative solution of a continuous variation procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account. It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions.

  5. Enhancing Eu(3+) magnetic dipole emission by resonant plasmonic nanostructures.

    PubMed

    Hussain, Rabia; Kruk, Sergey S; Bonner, Carl E; Noginov, Mikhail A; Staude, Isabelle; Kivshar, Yuri S; Noginova, Natalia; Neshev, Dragomir N

    2015-04-15

    We demonstrate the enhancement of magnetic dipole spontaneous emission from Eu3+ ions by an engineered plasmonic nanostructure that controls the electromagnetic environment of the emitter. Using an optical microscope setup, an enhancement in the intensity of the Eu3+ magnetic dipole emission was observed for emitters located in close vicinity to a gold nanohole array designed to support plasmonic resonances overlapping with the emission spectrum of the ions. PMID:25872041

  6. Targeting Apolipoproteins in Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Sriram, Renuka; Lagerstedt, Jens O.; Samardzic, Haris; Kreutzer, Ulrike; Petrolova, Jitka; Xie, Hongtao; Kaysen, George A.; Voss, John C.; Desreux, Jean F.; Jue, Thomas

    Maintaining normal physiological homeostasis depends upon a coordinated metabolism of both water-soluble and -insoluble substrates. In humans the body derives these molecules — such as glucose, amino acids, and fatty acids — from complex food matter. Water-soluble substrates can circulate readily in blood, while water-insoluble molecules — such as fatty acid, triacylglycerol, and cholesterol — require ampiphathic carriers to transport them from the site of biosynthesis (liver and intestine) to the target tissue. For fatty acid, albumin serves as the major transporter. For triacylglycerol and cholesterol, however, macromolecular complexes aggregate the hydrophobic molecules into the core and cover the surface with amphiphatic proteins and phospholipids to solubilize the particles in the lymphatic and circulatory systems. These macromolecules belong to a class of proteins, plasma lipoproteins, with specific functions and cellular targets. In the clinic these lipoproteins prognosticate the risk of cardiovascular disease (CVD). Lipoproteins divide usually into five major types: chylomicron, very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). Each lipoprotein type exhibits characteristic density, size, and composition. As implied in the name, the density varies from the low-density chylomicron (<0.95 g/ml) to the high-density HDL (1.2 g/ml). Size also varies. The chylomicron has the largest diameter (75-1,200 nm), and HDL has the smallest (5-12 nm). The physical property variation arises from each lipoprotein's distinct composition. In a chylomicron, cholesterol, triacylglycerol, and phospholipid predominate and constitute about 90% of the particle. Protein constitutes only about 10%. In contrast, the smaller HDL has less cholesterol, triacylglycerol, and phospholipid (65% of the particle) but more protein (over 30%).

  7. Interaction between magnetic agglomerates and an extended free radicals network studied by magnetic resonance

    NASA Astrophysics Data System (ADS)

    Guskos, Niko; Zolnierkiewicz, Grzegorz; Typek, Janusz; Guskos, Aleksander; Berczynski, Pawel; Petridis, Dimitri

    2012-02-01

    Solids containing an extended network of free radicals have been prepared and studied by magnetic resonance techniques in the 4-290 K temperature range. One solid contained additionally a small amount of magnetic γ-Fe2O3 in the form of nanoparticle agglomerates. The solid without agglomerates displayed only a narrow, single resonance line centered at g eff = 2.0043. The magnetic resonance measurements of the solid with γ-Fe2O3 agglomerates gave a spectrum composed of two lines attributed to two different magnetic centers: a narrow line due to free radicals and a broad line arising from magnetic iron oxide agglomerates. In the high temperature range the integrated intensities of both lines decreased with decreasing temperature. The resonance field of the broad line shifted to lower magnetic fields upon lowering the temperature with the gradient ΔH r/ΔT = 2.3 G/K, while the narrow line shifted towards higher magnetic fields. The linewidth of the broader line increased with decreasing temperature while for the narrow lines in both samples this change was small. The magnetic iron oxide clusters produce a magnetic field which acts on the free radicals network and its strength depends essentially on the concentration of clusters. The reorientation process in the free radicals network is more intense in the sample without magnetic clusters.

  8. Interaction between magnetic agglomerates and an extended free radicals network studied by magnetic resonance

    NASA Astrophysics Data System (ADS)

    Guskos, Niko; Zolnierkiewicz, Grzegorz; Typek, Janusz; Guskos, Aleksander; Berczynski, Pawel; Petridis, Dimitri

    2012-02-01

    Solids containing an extended network of free radicals have been prepared and studied by magnetic resonance techniques in the 4-290 K temperature range. One solid contained additionally a small amount of magnetic γ-Fe2O3 in the form of nanoparticle agglomerates. The solid without agglomerates displayed only a narrow, single resonance line centered at g eff = 2.0043. The magnetic resonance measurements of the solid with γ-Fe2O3 agglomerates gave a spectrum composed of two lines attributed to two different magnetic centers: a narrow line due to free radicals and a broad line arising from magnetic iron oxide agglomerates. In the high temperature range the integrated intensities of both lines decreased with decreasing temperature. The resonance field of the broad line shifted to lower magnetic fields upon lowering the temperature with the gradient Δ H r /Δ T = 2.3 G/K, while the narrow line shifted towards higher magnetic fields. The linewidth of the broader line increased with decreasing temperature while for the narrow lines in both samples this change was small. The magnetic iron oxide clusters produce a magnetic field which acts on the free radicals network and its strength depends essentially on the concentration of clusters. The reorientation process in the free radicals network is more intense in the sample without magnetic clusters.

  9. Electronic and transport properties of noncollinear magnetic monatomic Mn chains: Fano resonances in the superlattice of noncollinear magnetic barriers and magnetic anisotropic bands

    NASA Astrophysics Data System (ADS)

    Dai, C. J.; Yan, X. H.; Xiao, Y.; Guo, Y. D.

    2015-04-01

    By means of the density functional theory combined with non-equilibrium Green's function method, ballistic transport properties of one-dimensional noncollinear magnetic monatomic chains were investigated using the single-atomic Mn chains as a model system. Fano resonances are found to exist in the monatomic Mn chains with spin-spiral structure. Furthermore, in the monatomic Mn chains with magnetic soliton lattice, Fano resonances are enhanced and cause the conductance splitting in the transmission spectra. The Fano resonances in the noncollinear magnetic single-atomic Mn chains are arising from the coupling of the localized d-states and the extended states of the quantum channels. By constructing a theoretical model and calculating its conductance, it is found that the phenomena of Fano resonances and the accompanying conductance splitting exist universally in the superlattice of one-dimensional noncollinear magnetic barriers, due to the interference of the incident waves and reflected waves by the interfaces between the neighboring barriers. Moreover, the band structures of the ferromagnetic and spin-spiral monatomic Mn chains exhibit a strong dependence on the spatial arrangement of the magnetic moments of Mn atoms when spin-orbit coupling is considered.

  10. Paramagnetic ionic liquids for measurements of density using magnetic levitation.

    PubMed

    Bwambok, David K; Thuo, Martin M; Atkinson, Manza B J; Mirica, Katherine A; Shapiro, Nathan D; Whitesides, George M

    2013-09-01

    Paramagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation-anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev. PMID:23972068

  11. Magnetic Resonance Imaging Part I—Physical Principles

    PubMed Central

    Hendee, William R.; Morgan, Christopher J.

    1984-01-01

    Magnetic resonance (MR) imaging is the most complex imaging technology available to clinicians. Whereas most imaging technologies depict differences in one, or occasionally two, tissue characteristics, MR imaging has five tissue variables—spin density, T1 and T2 relaxation times and flow and spectral shifts—from which to construct its images. These variables can be combined in various ways by selecting pulse sequences and pulse times to emphasize any desired combination of tissue characteristics in the image. This selection is determined by the user of the MR system before imaging data are collected. If the selection is not optimal, the imaging process must be repeated at a cost of time and resources. The optimal selection of MR imaging procedures and the proper interpretation of the resultant images require a thorough understanding of the basic principles of MR imaging. Included in this understanding should be at least the rudiments of how an MR imaging signal is produced and why it decays with time; the significance of relaxation constants; the principles of scanning methods such as saturation recovery, inversion recovery and spin echo; how data obtained by these methods are used to form an image, and how the imaging data are complied by multi-slice and volumetric processes. In selecting an MR imaging unit, information about different magnet designs (resistive, superconductive and permanent) is useful. Although no bioeffects are thought to be associated with an MR imaging examination, some knowledge of the attempts to identify bioeffects is helpful in alleviating concern in patients. Images PMID:6506686

  12. Magnetic resonance imaging without field cycling at less than earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-03-01

    A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π / 2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

  13. Magnetic resonance imaging without field cycling at less than earth's magnetic field

    SciTech Connect

    Lee, Seong-Joo Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-03-09

    A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π/2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

  14. Calculation of ferromagnetic resonance spectra for chains of magnetic particles

    NASA Astrophysics Data System (ADS)

    Newell, A. J.

    2010-12-01

    Magnetotactic bacteria are a taxonomically diverse group of bacteria that have chains of ferromagnetic crystals inside. These bacteria mostly live in the oxic-anoxic interface (OAI) of aquatic environments. The magnetic chains orient the bacteria parallel to the Earth's magnetic field and help them to maintain their position near the OAI. These chains show the fingerprint of natural selection acting to optimize the magnetic moment per unit iron. This is achieved in a number of ways: the alignment in chains, a narrow size range, crystallographic perfection and chemical purity. Because of these distinctive characteristics, the particles can still be identified after the bacteria have died. Such magnetofossils are useful both as records of bacterial evolution and environmental markers. They can most reliably be identified by microscopy, but that is very labor-intensive. A number of magnetic measurements have been developed to identify magnetofossils quickly and non-invasively. However, the only test that can specifically identify the chain structure is ferromagnetic resonance (FMR), which measures the response to a magnetic field oscillating at microwave frequencies. Although the experimental side of ferromagnetic resonance is well developed, the theoretical models for interpreting them have been limited. A new method is presented for calculating resonance frequencies as well as complete power spectra for chains of interacting magnetic particles. Spectra are calculated and compared with data for magnetotactic bacteria.

  15. Fetal imaging by nuclear magnetic resonance: a study in goats: work in progress

    SciTech Connect

    Foster, M.A.; Knight, C.H.; Rimmington, J.E.; Mallard, J.R.

    1983-10-01

    Nuclear magnetic resonance proton imaging was used to obtain images of goat fetuses in utero. The long T1 relaxation time of amniotic fluid makes it appear black on proton density images when examined using the Aberdeen imager, and so allows very good discrimination of the position and structure of the fetus. Some fetal internal tissues can be seen on T1 images. These findings suggest that NMR imaging has great potential in pregnancy studies.

  16. Utilizing upper hybrid resonance for high density plasma production and negative ion generation in a downstream region

    SciTech Connect

    Sahu, Debaprasad; Bhattacharjee, Sudeep

    2012-09-15

    Localized wave-induced resonances are created by microwaves launched directly into a multicusp (MC) plasma device in the k Up-Tack B mode, where k is the wave vector and B is the static magnetic field. The resonance zone is identified as upper hybrid resonance (UHR), and lies r = {approx}22 mm away from the MC boundary. Measurement of radial wave electric field intensity confirms the right hand cutoff of the wave (r = 22.5-32.1 mm) located near the UHR zone. A sharp rise in the corresponding electron temperature in the resonance region by {approx}13 eV from its value away from resonance at r = 0, is favorable for the generation of vibrationally excited molecules of hydrogen. A transverse magnetic filter allows cold electrons ({approx}1-2 eV) to pass into the downstream region where they generate negative ions by dissociative attachment. Measurements of electron energy distribution function (EEDF) support the viewpoint. H{sup -} current density of {approx}0.26 mA/cm{sup 2} is obtained at a wave power density of {approx}3 W/cm{sup 2} at 2.0 mTorr pressure, which agrees reasonably well with results obtained from a steady state model using particle balance equations.

  17. Nuclear magnetic resonance study of potassium dihydrophosphate

    NASA Astrophysics Data System (ADS)

    Uskova, N. I.; Podorozhkin, D. Yu.; Charnaya, E. V.; Nefedov, D. Yu.; Baryshnikov, S. V.; Bugaev, A. S.; Lee, M. K.; Chang, L. J.

    2016-04-01

    A powder sample of potassium dihydrophosphate KH2PO4 has been studied by the 31P NMR method in a wide temperature range covering the ferroelectric phase transition. Changes in the position and shape of the resonance line at the transition to the ferroelectric phase have been revealed. The parameters of the chemical shift tensor of 31P (isotropic shift, anisotropy, and asymmetry) in the ferroelectric phase have been calculated from the experimental data. A sharp increase in the anisotropy of the tensor at the phase transition has been demonstrated. Dielectric measurements have also been carried out to verify the transition temperature.

  18. Magnetic Flux Density in the Heliosphere through Several Solar Cycles

    NASA Astrophysics Data System (ADS)

    Erdős, G.; Balogh, A.

    2014-01-01

    We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, BR , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of BR to such an extent that the determination of the unsigned, open solar magnetic flux density from the average lang|BR |rang is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.

  19. Magnetic flux density in the heliosphere through several solar cycles

    SciTech Connect

    Erdős, G.; Balogh, A.

    2014-01-20

    We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, B{sub R} , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of B{sub R} to such an extent that the determination of the unsigned, open solar magnetic flux density from the average (|B{sub R} |) is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.

  20. Magnetically modulated critical current densities of Co/Nb hybrid

    PubMed Central

    Li, Zhigang; Wang, Weike; Zhang, Li; Yang, Zhaorong; Tian, Mingliang; Zhang, Yuheng

    2015-01-01

    By tuning morphology and size of magnetic subsystem, ferromagnet-superconductor (F/S) hybrid system provides an effective way to modulate superconductivity due to the interaction between superconducting and magnetic-order parameters at the mesoscopic length scale. In this work, we report on investigations of critical current density in a large-area Co/Nb hybrid via facile colloidal lithography. Here, Co hexagon shell array as a magnetic template build on Nb film to modulate the critical current density. A novel superconducting transition has been observed in I-V curve with two metastable transition states: double-transition and binary-oscillation-transition states. Importantly, such unusual behavior can be adjusted by temperature, magnetic field and contact area of F/S. Such hybrid film has important implications for understanding the role of magnetic subsystem modulating superconductivity, as well as applied to low-energy electronic devices such as superconducting current fault limiters. PMID:26678595

  1. Magnetically modulated critical current densities of Co/Nb hybrid

    NASA Astrophysics Data System (ADS)

    Li, Zhigang; Wang, Weike; Zhang, Li; Yang, Zhaorong; Tian, Mingliang; Zhang, Yuheng

    2015-12-01

    By tuning morphology and size of magnetic subsystem, ferromagnet-superconductor (F/S) hybrid system provides an effective way to modulate superconductivity due to the interaction between superconducting and magnetic-order parameters at the mesoscopic length scale. In this work, we report on investigations of critical current density in a large-area Co/Nb hybrid via facile colloidal lithography. Here, Co hexagon shell array as a magnetic template build on Nb film to modulate the critical current density. A novel superconducting transition has been observed in I-V curve with two metastable transition states: double-transition and binary-oscillation-transition states. Importantly, such unusual behavior can be adjusted by temperature, magnetic field and contact area of F/S. Such hybrid film has important implications for understanding the role of magnetic subsystem modulating superconductivity, as well as applied to low-energy electronic devices such as superconducting current fault limiters.

  2. Magnetic Resonance Perfusion Imaging in the Study of Language

    ERIC Educational Resources Information Center

    Hillis, Argye E.

    2007-01-01

    This paper provides a brief review of various uses of magnetic resonance perfusion imaging in the investigation of brain/language relationships. The reviewed studies illustrate how perfusion imaging can reveal areas of brain where dysfunction due to low blood flow is associated with specific language deficits, and where restoration of blood flow…

  3. Principles of functional magnetic resonance imaging: application to auditory neuroscience.

    PubMed

    Cacace, A T; Tasciyan, T; Cousins, J P

    2000-05-01

    Functional imaging based on magnetic resonance methods is a new research frontier for exploring a wide range of central nervous system (CNS) functions, including information processing in sensory, motor, cognitive, and linguistic systems. Being able to localize and study human brain function in vivo, in relatively high resolution and in a noninvasive manner, makes this a technique of unparalleled importance. In order to appreciate and fully understand this area of investigation, a tutorial covering basic aspects of this methodology is presented. We introduce functional magnetic resonance imaging (fMRI) by providing an overview of the studies of different sensory systems in response to modality-specific stimuli, followed by an outline of other areas that have potential clinical relevance to the medical, cognitive, and communicative sciences. The discussion then focuses on the basic principles of magnetic resonance methods including magnetic resonance imaging, MR spectroscopy, fMRI, and the potential role that MR technology may play in understanding a wide range of auditory functions within the CNS, including tinnitus-related activity. Because the content of the material found herein might be unfamiliar to some, we provide a broad range of background and review articles to serve as a technical resource. PMID:10821504

  4. Magnetic resonance imaging in obstructive Müllerian anomalies.

    PubMed

    Sen, Kamal Kumar; Balasubramaniam, Dhivya; Kanagaraj, Vikrant

    2013-04-01

    Herlyn-Werner-Wunderlich (HWW) syndrome is a very rare congenital anomaly of the urogenital tract involving Müllerian ducts and Wolffian structures. It is characterized by the triad of didelphys uterus, obstructed hemivagina, and ipsilateral renal agenesis. Magnetic resonance imaging (MRI) is a sensitive, non-invasive diagnostic modality for demonstrating anatomic variation and associated complications. PMID:24082660

  5. Concepts in Biochemistry: Nuclear Magnetic Resonance Spectroscopy in Biochemistry.

    ERIC Educational Resources Information Center

    Cheatham, Steve

    1989-01-01

    Discusses the nature of a nuclear magnetic resonance (NMR) experiment, the techniques used, the types of structural and dynamic information obtained, and how one can view and refine structures using computer graphics techniques in combination with NMR data. Provides several spectra and a computer graphics image from B-form DNA. (MVL)

  6. C-13 nuclear magnetic resonance in organic geochemistry.

    NASA Technical Reports Server (NTRS)

    Balogh, B.; Wilson, D. M.; Burlingame, A. L.

    1972-01-01

    Study of C-13 nuclear magnetic resonance (NMR) spectra of polycyclic fused systems. The fingerprint qualities of the natural abundance in C-13 NMR spectra permitting unequivocal identification of these compounds is discussed. The principle of structural additivity of C-13 NMR information is exemplified on alpha and beta androstanes, alpha and beta cholestanes, ergostanes, sitostanes, and isodecanes.

  7. Using Nuclear Magnetic Resonance Spectroscopy for Measuring Ternary Phase Diagrams

    ERIC Educational Resources Information Center

    Woodworth, Jennifer K.; Terrance, Jacob C.; Hoffmann, Markus M.

    2006-01-01

    A laboratory experiment is presented for the upper-level undergraduate physical chemistry curriculum in which the ternary phase diagram of water, 1-propanol and n-heptane is measured using proton nuclear magnetic resonance (NMR) spectroscopy. The experiment builds upon basic concepts of NMR spectral analysis, typically taught in the undergraduate…

  8. Magnetic resonance segmentation with the bubble wave algorithm

    NASA Astrophysics Data System (ADS)

    Cline, Harvey E.; Ludke, Siegwalt

    2003-05-01

    A new bubble wave algorithm provides automatic segmentation of three-dimensional magnetic resonance images of both the peripheral vasculature and the brain. Simple connectivity algorithms are not reliable in these medical applications because there are unwanted connections through background noise. The bubble wave algorithm restricts connectivity using curvature by testing spherical regions on a propagating active contour to eliminate noise bridges. After the user places seeds in both the selected regions and in the regions that are not desired, the method provides the critical threshold for segmentation using binary search. Today, peripheral vascular disease is diagnosed using magnetic resonance imaging with a timed contrast bolus. A new blood pool contrast agent MS-325 (Epix Medical) binds to albumen in the blood and provides high-resolution three-dimensional images of both arteries and veins. The bubble wave algorithm provides a means to automatically suppress the veins that obscure the arteries in magnetic resonance angiography. Monitoring brain atrophy is needed for trials of drugs that retard the progression of dementia. The brain volume is measured by placing seeds in both the brain and scalp to find the critical threshold that prevents connections between the brain volume and the scalp. Examples from both three-dimensional magnetic resonance brain and contrast enhanced vascular images were segmented with minimal user intervention.

  9. Voriconazole-related periostitis presenting on magnetic resonance imaging.

    PubMed

    Davis, Derik L

    2015-01-01

    Painful periostitis is a complication of long-term antifungal therapy with voriconazole. A high clinical suspicion coupled with imaging and laboratory assessment is useful to establish the diagnosis. Prompt discontinuance of voriconazole typically results in the resolution of symptoms and signs. This report describes the presentation of voriconazole-related periostitis on magnetic resonance imaging. PMID:26136804

  10. Voriconazole-related periostitis presenting on magnetic resonance imaging

    PubMed Central

    Davis, Derik L.

    2015-01-01

    Summary Painful periostitis is a complication of long-term antifungal therapy with voriconazole. A high clinical suspicion coupled with imaging and laboratory assessment is useful to establish the diagnosis. Prompt discontinuance of voriconazole typically results in the resolution of symptoms and signs. This report describes the presentation of voriconazole-related periostitis on magnetic resonance imaging. PMID:26136804

  11. Functional Connectivity Magnetic Resonance Imaging Classification of Autism

    ERIC Educational Resources Information Center

    Anderson, Jeffrey S.; Nielsen, Jared A.; Froehlich, Alyson L.; DuBray, Molly B.; Druzgal, T. Jason; Cariello, Annahir N.; Cooperrider, Jason R.; Zielinski, Brandon A.; Ravichandran, Caitlin; Fletcher, P. Thomas; Alexander, Andrew L.; Bigler, Erin D.; Lange, Nicholas; Lainhart, Janet E.

    2011-01-01

    Group differences in resting state functional magnetic resonance imaging connectivity between individuals with autism and typically developing controls have been widely replicated for a small number of discrete brain regions, yet the whole-brain distribution of connectivity abnormalities in autism is not well characterized. It is also unclear…

  12. Estimating the size of myocardial infarction by magnetic resonance imaging.

    PubMed Central

    Turnbull, L W; Ridgway, J P; Nicoll, J J; Bell, D; Best, J J; Muir, A L

    1991-01-01

    OBJECTIVE--To develop a method to measure myocardial infarct size by magnetic resonance imaging and to compare the results with pyrophosphate scanning by single photon emission computed tomography. DESIGN--All patients underwent magnetic resonance imaging and pyrophosphate scanning 5-7 days after the onset of symptoms. Both measurements of infarct size were compared with the release of creatine kinase MB and with ventricular performance estimated by radionuclide ventriculography. PATIENTS--19 patients (age 40-68 years) who had sustained their first uncomplicated myocardial infarction and who had not been treated with thrombolytic therapy. RESULTS--The site of infarction was clearly shown by both imaging techniques and was identical in each patient. The volume of infarcted tissue measured by magnetic resonance imaging agreed well with the infarct size measured by single photon emission tomography (mean difference 2.7 cm3). Correlations of both imaging techniques with the release of creatine kinase MB were best when total release rather than peak release was used. Both imaging techniques correlated closely with the subsequent ventricular performance. CONCLUSIONS--Magnetic resonance imaging after acute infarction allows measurement of infarct size and this may prove useful in assessing new treatments designed to salvage myocardium. Images PMID:1836135

  13. Sonographic and magnetic resonance imaging findings of neurocutaneous melanosis.

    PubMed

    Chen, Yingming Amy; Woodley-Cook, Joel; Sgro, Michael; Bharatha, Aditya

    2016-03-01

    Neurocutaneous melanosis is a rare nonfamilial phakomatosis characterized by large or multiple congenital melanocytic nevi plus the presence of central nervous system melanosis or melanoma. We report a case of a male infant with a giant posteroaxial nevus and evidence of intracranial melanosis on ultrasound and magnetic resonance imaging. PMID:26973729

  14. Nuclear magnetic resonance implementation of a quantum clock synchronization algorithm

    SciTech Connect

    Zhang Jingfu; Long, G.C; Liu Wenzhang; Deng Zhiwei; Lu Zhiheng

    2004-12-01

    The quantum clock synchronization (QCS) algorithm proposed by Chuang [Phys. Rev. Lett. 85, 2006 (2000)] has been implemented in a three qubit nuclear magnetic resonance quantum system. The time difference between two separated clocks can be determined by measuring the output states. The experimental realization of the QCS algorithm also demonstrates an application of the quantum phase estimation.

  15. Fabrication of vascular replicas from magnetic resonance images.

    PubMed

    Friedman, M H; Kuban, B D; Schmalbrock, P; Smith, K; Altan, T

    1995-08-01

    Image processing and Computer Numerical Controlled (CNC) machining techniques have been used to prepare a large-than-life investment cast of an aortic bifurcation from magnetic resonance images of a replica of the vessel. The technique will facilitate experimental studies of vascular fluid dynamics and permit the in vitro reproduction of flows in living subjects. PMID:8618391

  16. RECONSTRUCTION OF HUMAN LUNG MORPHOLOGY MODELS FROM MAGNETIC RESONANCE IMAGES

    EPA Science Inventory


    Reconstruction of Human Lung Morphology Models from Magnetic Resonance Images
    T. B. Martonen (Experimental Toxicology Division, U.S. EPA, Research Triangle Park, NC 27709) and K. K. Isaacs (School of Public Health, University of North Carolina, Chapel Hill, NC 27514)

  17. Nuclear Magnetic Resonance Coupling Constants and Electronic Structure in Molecules.

    ERIC Educational Resources Information Center

    Venanzi, Thomas J.

    1982-01-01

    Theory of nuclear magnetic resonance spin-spin coupling constants and nature of the three types of coupling mechanisms contributing to the overall spin-spin coupling constant are reviewed, including carbon-carbon coupling (neither containing a lone pair of electrons) and carbon-nitrogen coupling (one containing a lone pair of electrons).…

  18. 5.4 Magnetic Resonance Imaging, Diagnostic Ultrasound

    NASA Astrophysics Data System (ADS)

    Bernhardt, J. H.

    This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '5.4 Magnetic Resonance Imaging, Diagnostic Ultrasound' of the Chapter '5 Medical Radiological Protection' with the contents:

  19. Three-Dimensional Magnetic Resonance Imaging of Velopharyngeal Structures

    ERIC Educational Resources Information Center

    Bae, Youkyung; Kuehn, David P.; Sutton, Bradley P.; Conway, Charles A.; Perry, Jamie L.

    2011-01-01

    Purpose: To report the feasibility of using a 3-dimensional (3D) magnetic resonance imaging (MRI) protocol for examining velopharyngeal structures. Using collected 3D MRI data, the authors investigated the effect of sex on the midsagittal velopharyngeal structures and the levator veli palatini (levator) muscle configurations. Method: Ten Caucasian…

  20. Magnetic resonance imaging in obstructive Müllerian anomalies

    PubMed Central

    Sen, Kamal Kumar; Balasubramaniam, Dhivya; Kanagaraj, Vikrant

    2013-01-01

    Herlyn-Werner-Wunderlich (HWW) syndrome is a very rare congenital anomaly of the urogenital tract involving Müllerian ducts and Wolffian structures. It is characterized by the triad of didelphys uterus, obstructed hemivagina, and ipsilateral renal agenesis. Magnetic resonance imaging (MRI) is a sensitive, non-invasive diagnostic modality for demonstrating anatomic variation and associated complications. PMID:24082660