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Sample records for saturation mri theory

  1. Theory of graphene saturable absorption

    Science.gov (United States)

    Marini, A.; Cox, J. D.; García de Abajo, F. J.

    2017-03-01

    Saturable absorption is a nonperturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses. Here we show that this effect emerges in graphene at unprecedentedly low light intensities, thus opening avenues to new nonlinear physics and applications in optical technology. Specifically, we theoretically investigate saturable absorption in extended graphene by developing a semianalytical nonperturbative single-particle approach, describing electron dynamics in the atomically-thin material using the two-dimensional Dirac equation for massless Dirac fermions, which is recast in the form of generalized Bloch equations. By solving the electron dynamics nonperturbatively, we account for both interband and intraband contributions to the intensity-dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material. We obtain results in qualitative agreement with atomistic quantum-mechanical simulations of graphene nanoribbons including electron-electron interactions, finite-size, and higher-band effects. Remarkably, such effects are found to affect mainly the linear absorption, while the predicted saturation intensities are in good quantitative agreement in the limit of extended graphene. Additionally, we find that the modulation depth of saturable absorption in graphene can be electrically manipulated through an externally applied gate voltage. Our results are relevant for the development of graphene-based optoelectronic devices, as well as for applications in mode-locking and random lasers.

  2. Saturated Dispersive Extinction Theory of Red Shift

    Science.gov (United States)

    Wang, Ling Jun

    2012-03-01

    The Dispersive Extinction Theory (DET) proposed by WangfootnotetextWang, Ling Jun, Physics Essays, 18, No. 2, (2005). offers an alternative to the Big Bang. According to DET, the cosmic red shift is caused by the dispersive extinction of the star light during the propagation from the stars to the earth, instead of being caused by the Doppler shift due to the expansion of the universe.footnotetextHubble, E., Astrophys. J. 64, 321 (1926).^,footnotetextHubble, E., The Realm of the Nebulae, (Yale University Press, New Haven, 1936). DET allows an infinite, stable, non expanding universe, and is immune of the fundamental problems inherent to the Big Bang such as the horizon problem, the extreme violation of the conservation of mass, energy and charge, and the geocentric nature which violates the principle of relativity.footnotetextWang, Ling Jun, Physics Essays, 20, No. 2, (2007). The scenario dealt with in Reference (1) is a one in which the extinction by the space medium is not saturated. This work deals with a different scenario when the extinction is saturated. The saturated extinction causes limited energy loss, and the star light can travel a much greater distance than in the unsaturated scenario.

  3. Rigid aleph_epsilon-saturated models of superstable theories

    OpenAIRE

    Shami, Ziv; Shelah, Saharon

    1999-01-01

    In a countable superstable NDOP theory, the existence of a rigid aleph_epsilon-saturated model implies the existence of 2^lambda rigid aleph_epsilon-saturated models of power lambda for every lambda>2^{aleph_0}.

  4. A saturating chiral field theory of nuclear matter

    Directory of Open Access Journals (Sweden)

    J. Boguta

    1983-01-01

    Full Text Available Catastrophe Theory analysis is used to construct a chiral theory of pions which leads to a saturating nuclear matter equation of state. This is achieved by introducing a vector meson field via the Higgs mechanism. The equation of state and the nuclear optical potential are computed. A metamorphosis of the nuclear force is suggested.

  5. Design and optimization of pulsed Chemical Exchange Saturation Transfer MRI using a multiobjective genetic algorithm.

    Science.gov (United States)

    Yoshimaru, Eriko S; Randtke, Edward A; Pagel, Mark D; Cárdenas-Rodríguez, Julio

    2016-02-01

    Pulsed Chemical Exchange Saturation Transfer (CEST) MRI experimental parameters and RF saturation pulse shapes were optimized using a multiobjective genetic algorithm. The optimization was carried out for RF saturation duty cycles of 50% and 90%, and results were compared to continuous wave saturation and Gaussian waveform. In both simulation and phantom experiments, continuous wave saturation performed the best, followed by parameters and shapes optimized by the genetic algorithm and then followed by Gaussian waveform. We have successfully demonstrated that the genetic algorithm is able to optimize pulse CEST parameters and that the results are translatable to clinical scanners. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Application of chemical exchange saturation transfer (CEST) MRI for endogenous contrast at 7 Tesla.

    Science.gov (United States)

    Dula, Adrienne N; Smith, Seth A; Gore, John C

    2013-10-01

    Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) indirectly images exchangeable solute protons resonating at frequencies different than bulk water. These solute protons are selectively saturated using low bandwidth RF irradiation and saturation is transferred to bulk water protons via chemical exchange, resulting in an attenuation of the measured water proton signal. CEST MRI is an advanced MRI technique with wide application potential due to the ability to examine complex molecular contributions. CEST MRI at high field (7 Tesla [7 T]) will improve the overall results due to increase in signal, T1 relaxation time, and chemical shift dispersion. Increased field strength translates to enhanced quantification of the metabolite of interest, allowing more fundamental studies on underlying pathophysiology. CEST contrast is affected by several tissue properties, such as the concentrations of exchange partners and their rate of proton exchange, whose effects have been examined and explored in this review. We have highlighted the background of CEST MRI, typical implementation strategy, and complications at 7 T. Copyright © 2013 by the American Society of Neuroimaging.

  7. Diffusion MRI noise mapping using random matrix theory

    National Research Council Canada - National Science Library

    Veraart, Jelle; Fieremans, Els; Novikov, Dmitry S

    2016-01-01

    .... Methods We exploit redundancy in non-Gaussian distributed multidirectional diffusion MRI data by identifying its noise-only principal components, based on the theory of noisy covariance matrices...

  8. A Partially Saturated Constitutive Theory for Compacted Fills

    Science.gov (United States)

    2004-06-01

    excellent example of this is the work by Brackley (1975) who envisioned the grain structure of a partially saturated soil and therefore a means to explain...Josa, A., (1988). "Un modelo elastoplastico para suelos no saturados," Tesis Doctorae, Universitat Politecnica de Catalunya, Barcelons, Spain. Lawton...smech + icode IF(hflag(r)) hmech=bmnech + icode IF(tflag(r)) trnech=tmech + icode icode = 10*icode end do Print data for an Excel file Added for

  9. Fuzzy Saturated Output Feedback Tracking Control for Robot Manipulators: A Singular Perturbation Theory Based Approach

    National Research Council Canada - National Science Library

    Liu, Huashan; Hao, Kuangrong; Lai, Xiaobo

    2011-01-01

    To deal with the problem of the output feedback tracking (OFT) control with bounded torque inputs of robot manipulators, we propose a generalized fuzzy saturated OFT controller based on singular perturbation theory...

  10. Fuzzy Saturated Output Feedback Tracking Control for Robot Manipulators: A Singular Perturbation Theory Based Approach

    OpenAIRE

    Huashan Liu; Kuangrong Hao; Xiaobo Lai

    2011-01-01

    To deal with the problem of the output feedback tracking (OFT) control with bounded torque inputs of robot manipulators, we propose a generalized fuzzy saturated OFT controller based on singular perturbation theory. First, considering the fact that the output toque of joint actuators is limited, a general expression for a class of saturation functions is given to be applied in the control law. Second, to carry out the whole closed‐loop control with only position measurements, linear and...

  11. Theory of turbulent saturation in stellarators: identifying mechanisms to reduce turbulent transport

    Science.gov (United States)

    Hegna, C. C.; Terry, P. W.; Faber, B. J.

    2017-10-01

    A theory for ion temperature gradient (ITG) turbulent saturation in stellarators is developed using a three field fluid model that allows for general 3D geometry. The model relies on the paradigm of nonlinear energy transfer from unstable to damped eigenmodes at comparable wavelength as the dominant saturation process. This mechanism is enabled by a three-wave interaction where the third mode primarily regulates the nonlinear energy transfer rate and depends upon the properties of the magnetic geometry. In particular, this work suggests that quasi-helically symmetric configurations may have an intrinsic advantage with regard to turbulent saturation physics relative to other configurations as multiple energy transfer channels can be exploited. Nonlinear energy transfer physics is quantified by the product of a turbulent correlation lifetime as computed from a three-wave frequency mismatch and a geometric coupling coefficient with larger turbulent correlation times denoting larger levels of nonlinear energy transfer and hence smaller turbulent transport. The theory provides an analytic prediction for how 3D shaping can be tuned to lower turbulent transport through saturation processes that can by used in optimization schemes for improved stellarator design. Research supported by U. S. DoE Grants DE-FG02-99ER54546, DE-FG02-93ER54222 and DE-FG02-89ER53291.

  12. Fuzzy Saturated Output Feedback Tracking Control for Robot Manipulators: A Singular Perturbation Theory Based Approach

    Directory of Open Access Journals (Sweden)

    Huashan Liu

    2011-09-01

    Full Text Available To deal with the problem of the output feedback tracking (OFT control with bounded torque inputs of robot manipulators, we propose a generalized fuzzy saturated OFT controller based on singular perturbation theory. First, considering the fact that the output toque of joint actuators is limited, a general expression for a class of saturation functions is given to be applied in the control law. Second, to carry out the whole closed-loop control with only position measurements, linear and nonlinear filters are optionally involved to generate a pseudo signal to surrogate the actual velocity tracking error. As a third contribution, a fuzzy regulator is added to obtain a self-tuning performance in tackling the disturbances. Moreover, an explicit but strict stability proof of the system based on the stability theory of singularly perturbed systems is presented. Finally, numerical simulations on several sample controllers are implemented to verify the effectiveness of the proposed approach.

  13. Fuzzy Saturated Output Feedback Tracking Control for Robot Manipulators: A Singular Perturbation Theory Based Approach

    Directory of Open Access Journals (Sweden)

    Huashan Liu

    2011-09-01

    Full Text Available To deal with the problem of the output feedback tracking (OFT control with bounded torque inputs of robot manipulators, we propose a generalized fuzzy saturated OFT controller based on singular perturbation theory. First, considering the fact that the output toque of joint actuators is limited, a general expression for a class of saturation functions is given to be applied in the control law. Second, to carry out the whole closed‐loop control with only position measurements, linear and nonlinear filters are optionally involved to generate a pseudo signal to surrogate the actual velocity tracking error. As a third contribution, a fuzzy regulator is added to obtain a self‐tuning performance in tackling the disturbances. Moreover, an explicit but strict stability proof of the system based on the stability theory of singularly perturbed systems is presented. Finally, numerical simulations on several sample controllers are implemented to verify the effectiveness of the proposed approach.

  14. Synthesis of a probe for monitoring HSV1-tk reporter gene expression using chemical exchange saturation transfer MRI.

    Science.gov (United States)

    Bar-Shir, Amnon; Liu, Guanshu; Greenberg, Marc M; Bulte, Jeff W M; Gilad, Assaf A

    2013-12-01

    In experiments involving transgenic animals or animals treated with transgenic cells, it is important to have a method to monitor the expression of the relevant genes longitudinally and noninvasively. An MRI-based reporter gene enables monitoring of gene expression in the deep tissues of living subjects. This information can be co-registered with detailed high-resolution anatomical and functional information. We describe here the synthesis of the reporter probe, 5-methyl-5,6-dihydrothymidine (5-MDHT), which can be used for imaging of the herpes simplex virus type 1 thymidine kinase (HSV1-tk) reporter gene expression in rodents by MRI. The protocol also includes data acquisition and data processing routines customized for chemical exchange saturation transfer (CEST) contrast mechanisms. The dihydropyrimidine 5-MDHT is synthesized through a catalytic hydrogenation of the 5,6-double bond of thymidine to yield 5,6-dihydrothymidine, which is methylated on the C-5 position of the resulting saturated pyrimidine ring. The synthesis of 5-MDHT can be completed within 5 d, and the compound is stable for more than 1 year.

  15. Effects of variable blast pressures on blood flow and oxygen saturation in rat brain as evidenced using MRI.

    Science.gov (United States)

    Bir, Cynthia; Vandevord, Pamela; Shen, Yimin; Raza, Waqar; Haacke, E Mark

    2012-05-01

    It has been recognized that primary blast waves may result in neurotrauma in soldiers in theater. A new type of contrast used in magnetic resonance imaging (MRI), susceptibility-weighted imaging (SWI), has been developed that is based on the different susceptibility levels in diverse tissues and can detect decreases in cerebral blood flow (CBF) using inferred oxygen saturation changes in tissue. In addition, a continuous arterial spin-labeled (ASL) MRI sequence was used as a direct measure of regional CBF within the brain tissue. Animals were subjected to whole-body blast exposures of various overpressures within a gas-driven shock tube. When exposed to low levels of overpressure, most rats demonstrated no obvious changes between pre- and postexposure in the conventional MR images. CBF changes measured by SWI and ASL were significantly higher for the overpressure exposed groups as compared to the sham group and tended to increase with pressure increases at the highest two pressures. In the hippocampus, all blast animals had a reduction in the CBF consistently in the range of 0-27%. In summary, low levels of primary blast pressure exposure demonstrated a significant physiologic effect to the brain up to 72 h postexposure. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Diffusion MRI noise mapping using random matrix theory

    Science.gov (United States)

    Veraart, Jelle; Fieremans, Els; Novikov, Dmitry S.

    2016-01-01

    Purpose To estimate the spatially varying noise map using a redundant magnitude MR series. Methods We exploit redundancy in non-Gaussian multi-directional diffusion MRI data by identifying its noise-only principal components, based on the theory of noisy covariance matrices. The bulk of PCA eigenvalues, arising due to noise, is described by the universal Marchenko-Pastur distribution, parameterized by the noise level. This allows us to estimate noise level in a local neighborhood based on the singular value decomposition of a matrix combining neighborhood voxels and diffusion directions. Results We present a model-independent local noise mapping method capable of estimating noise level down to about 1% error. In contrast to current state-of-the art techniques, the resultant noise maps do not show artifactual anatomical features that often reflect physiological noise, the presence of sharp edges, or a lack of adequate a priori knowledge of the expected form of MR signal. Conclusions Simulations and experiments show that typical diffusion MRI data exhibit sufficient redundancy that enables accurate, precise, and robust estimation of the local noise level by interpreting the PCA eigenspectrum in terms of the Marchenko-Pastur distribution. PMID:26599599

  17. Saturated fat consumption and the Theory of Planned Behaviour: exploring additive and interactive effects of habit strength

    NARCIS (Netherlands)

    de Bruijn, G.J.; Kroeze, W.; Oenema, O.; Brug, J.

    2008-01-01

    The additive and interactive effects of habit strength in the explanation of saturated fat intake were explored within the framework of the Theory of Planned Behaviour (TPB). Cross-sectional data were gathered in a Dutch adult sample (n = 764) using self-administered questionnaires and analyzed

  18. Fat suppression techniques for breast MRI: Dixon versus spectral fat saturation for 3D T1-weighted at 3 T.

    Science.gov (United States)

    Kalovidouri, Anastasia; Firmenich, Natacha; Delattre, Benedicte M A; Picarra, Marlise; Becker, Christoph D; Montet, Xavier; Botsikas, Diomidis

    2017-10-01

    To compare two fat suppression techniques used for 3D T1-weighted sequence in breast MRI (magnetic resonance imaging), namely Dixon versus spectral fat saturation (fat sat). All breast MRI examinations performed in a Philips 3 T unit between March 2013 and October 2015 including either a Dixon or a fat sat sequence were retrospectively analyzed. The examinations were subjectively evaluated by two independent experienced readers in a scale of 5 for overall quality of fat suppression, homogeneity of fat suppression, definition of anatomic structures and focal lesions, diagnostic confidence for axillary and internal mammary regions and the presence of artifacts, 1 corresponding to excellent and 5 to non-diagnostic quality. Contrast-to-noise-ratio (CNR) measurements for muscle and focal lesions were also performed. Overall 161 women (mean age 51.6 ± 12.0 years) underwent 189 MR examinations, 113 with the fat saturation and 76 with the Dixon sequence. Interobserver variability was good (kappa = 0.757). In all subjectively evaluated parameters, the Dixon sequence was superior to the fat sat (p fat sat and 18.3 (±10.4) and 29.3 (±14.1) for the Dixon sequence, respectively (p fat sat for dedicated breast MRI at 3 T, in terms of efficiency of fat suppression and image quality with the added advantage of optimal exploration of the axillary areas.

  19. MRI

    DEFF Research Database (Denmark)

    Schroeter, Aileen; Rudin, Markus; Gianolio, Eliana

    2017-01-01

    This chapter discusses principles of nuclear magnetic resonance (NMR) and MRI followed by a survey on the major classes of MRI contrast agents (CA), their modes of action, and some of the most significative applications. The two more established classes of MRI-CA are represented by paramagnetic...

  20. Research progress of multimodal MRI and complex network analysis based on graph theory in Parkinson's disease

    Directory of Open Access Journals (Sweden)

    Ming-jin MEI

    2017-01-01

    Full Text Available Parkinson's disease (PD is a common progressive neurodegenerative disease and is mainly caused by dopamine neuron degeneration in the substantia nigra pars compacta of the human brain. It has become "the third killer" after tumor and cardio-cerebrovascular disease in middle-aged and elderly people at present. In recent years, the development of multimodal MRI [including structural MRI (sMRI, functional MRI (fMRI, diffusion tension imaging (DTI, etc.] and the introduction of complex network analysis based on graph theory provide a new and effective method for researchers to explore the changes of brain structure and function in PD patients. The article mainly reviews the research progress of structural and functional brain networks in PD patients that are established based on multimodal MRI and complex network analysis based on graph theory, so as to provide new imaging markers for the early diagnosis of PD. DOI: 10.3969/j.issn.1672-6731.2017.01.004

  1. Athletic injuries of the extensor carpi ulnaris subsheath: MRI findings and utility of gadolinium-enhanced fat-saturated T1-weighted sequences with wrist pronation and supination

    Energy Technology Data Exchange (ETDEWEB)

    Jeantroux, Jeremy; Guerini, Henri; Drape, Jean-Luc [Universite Paris Descartes, Department of Radiology B, Hopital Cochin, AP-HP, Paris (France); Becce, Fabio [Universite Paris Descartes, Department of Radiology B, Hopital Cochin, AP-HP, Paris (France); University of Lausanne, Department of Diagnostic and Interventional Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne (Switzerland); Montalvan, Bernard [French Tennis Federation, Paris (France); Viet, Dominique Le [Hand Institute, Clinique Jouvenet, Paris (France)

    2011-01-15

    To report the magnetic resonance imaging (MRI) findings in athletic injuries of the extensor carpi ulnaris (ECU) subsheath, assessing the utility of gadolinium-enhanced (Gd) fat-saturated (FS) T1-weighted sequences with wrist pronation and supination. Sixteen patients (13 male, three female; mean age 30.3 years) with athletic injuries of the ECU subsheath sustained between January 2003 and June 2009 were included in this retrospective study. Initial and follow-up 1.5-T wrist MRIs were performed with transverse T1-weighted and STIR sequences in pronation, and Gd FS T1-weighted sequences with wrist pronation and supination. Two radiologists assessed the type of injury (A to C), ECU tendon stability, associated lesions and rated pulse sequences using a three-point scale: 1 = poor, 2 = good and 3 = excellent. Gd-enhanced FS T1-weighted transverse sequences in supination (2.63) and pronation (2.56) were most valuable, compared with STIR (2.19) and T1-weighted (1.94). Nine type A, one type B and six type C injuries were found. There were trends towards diminution in size, signal intensity and enhancement of associated pouches on follow-up MRI and tendon stabilisation within the ulnar groove. Gd-enhanced FS T1-weighted sequences with wrist pronation and supination are most valuable in assessing and follow-up athletic injuries of the ECU subsheath on 1.5-T MRI. (orig.)

  2. Denoising of diffusion MRI using random matrix theory

    Science.gov (United States)

    Veraart, Jelle; Novikov, Dmitry S.; Christiaens, Daan; Ades-aron, Benjamin; Sijbers, Jan; Fieremans, Els

    2016-01-01

    We introduce and evaluate a post-processing technique for fast denoising diffusion-weighted MR images. By exploiting the intrinsic redundancy in diffusion MRI using universal properties of the eigenspectrum of random covariance matrices, we remove noise-only principal components, thereby enabling signal-to-noise ratio enhancements, yielding parameter maps of improved quality for visual, quantitative, and statistical interpretation. By studying statistics of residuals, we demonstrate that the technique suppresses local signal fluctuations that solely originate from thermal noise rather than from other sources such as anatomical detail. Furthermore, we achieve improved precision in the estimation of diffusion parameters and fiber orientations in the human brain without compromising the accuracy and/or spatial resolution. PMID:27523449

  3. Partially-saturated transient groundwater flow model theory and numerical implementation

    Energy Technology Data Exchange (ETDEWEB)

    Reisenauer, A.E.; Cearlock, D.B.; Bryan, C.A.

    1975-01-01

    A description is presented of the mathematical development of a computer model, the Partially-Saturated Transient Flow Model (PST), used to test the formulation for simulating isothermal, unsaturated, liquid flow in heterogeneous porous media. The fundamental equations and assumptions applying to the model are discussed. Problems encountered in modeling the flow in soils with water contents less than saturation are also delineated. Because of the nonlinearities of the descriptive equations, finite difference approximation and an iterative technique were used to obtain solutions. The model, when tested, was computationally slow and impractical as a management tool but did demonstrate that the equation could be solved for flow entering relatively dry soils. Several methods of dealing with the sediment hydraulic characteristics were tested.

  4. Determination of an optimally sensitive and specific chemical exchange saturation transfer MRI quantification metric in relevant biological phantoms.

    Science.gov (United States)

    Ray, Kevin J; Larkin, James R; Tee, Yee K; Khrapitchev, Alexandre A; Karunanithy, Gogulan; Barber, Michael; Baldwin, Andrew J; Chappell, Michael A; Sibson, Nicola R

    2016-11-01

    The purpose of this study was to develop realistic phantom models of the intracellular environment of metastatic breast tumour and naïve brain, and using these models determine an analysis metric for quantification of CEST MRI data that is sensitive to only labile proton exchange rate and concentration. The ability of the optimal metric to quantify pH differences in the phantoms was also evaluated. Novel phantom models were produced, by adding perchloric acid extracts of either metastatic mouse breast carcinoma cells or healthy mouse brain to bovine serum albumin. The phantom model was validated using 1 H NMR spectroscopy, then utilized to determine the sensitivity of CEST MRI to changes in pH, labile proton concentration, T1 time and T2 time; six different CEST MRI analysis metrics (MTRasym , APT*, MTRRex , AREX and CESTR* with and without T1 /T2 compensation) were compared. The new phantom models were highly representative of the in vivo intracellular environment of both tumour and brain tissue. Of the analysis methods compared, CESTR* with T1 and T2 time compensation was optimally specific to changes in the CEST effect (i.e. minimal contamination from T1 or T2 variation). In phantoms with identical protein concentrations, pH differences between phantoms could be quantified with a mean accuracy of 0.6 pH units. We propose that CESTR* with T1 and T2 time compensation is the optimal analysis method for these phantoms. Analysis of CEST MRI data with T1 /T2 time compensated CESTR* is reproducible between phantoms, and its application in vivo may resolve the intracellular alkalosis associated with breast cancer brain metastases without the need for exogenous contrast agents. © 2016 The Authors NMR in Biomedicine Published by John Wiley & Sons Ltd.

  5. Spin-locking vs. chemical exchange saturation transfer MRI for investigating chemical exchange process between water and labile metabolite protons

    Science.gov (United States)

    Jin, Tao; Autio, Joonas; Obata, Takayuki; Kim, Seong-Gi

    2010-01-01

    Chemical exchange saturation transfer (CEST) and spin-locking (SL) experiments were both able to probe the exchange process between protons of non-equivalent chemical environments. To compare the characteristics of the CEST and SL approaches in the study of chemical exchange effects, we performed CEST and SL experiments at varied pH and concentrated metabolites with exchangeable amide, amine, and hydroxyl protons at 9.4 T. Our results show that: i) On-resonance SL is most sensitive to chemical exchanges in the intermediate exchange regime and is able to detect hydroxyl and amine protons on a millimolar concentration scale. Off-resonance SL and CEST approaches are sensitive to slow-exchanging protons when an optimal SL or saturation pulse power matches the exchanging rate, respectively. ii) Offset frequency-dependent SL and CEST spectra are very similar, and can be explained well with an SL model recently developed by Trott and Palmer. iii) The exchange rate and population of metabolite protons can be determined from offset-dependent SL or CEST spectra or from on-resonance SL relaxation dispersion measurements. iv) The asymmetry of the magnetization transfer ratio (MTRasym) is highly dependent on the choice of saturation pulse power. In the intermediate exchange regime, MTRasym becomes complicated and should be interpreted with care. PMID:21500270

  6. Spin-locking versus chemical exchange saturation transfer MRI for investigating chemical exchange process between water and labile metabolite protons.

    Science.gov (United States)

    Jin, Tao; Autio, Joonas; Obata, Takayuki; Kim, Seong-Gi

    2011-05-01

    Chemical exchange saturation transfer (CEST) and spin-locking (SL) experiments were both able to probe the exchange process between protons of nonequivalent chemical environments. To compare the characteristics of the CEST and SL approaches in the study of chemical exchange effects, we performed CEST and SL experiments at varied pH and concentrated metabolite phantoms with exchangeable amide, amine, and hydroxyl protons at 9.4 T. Our results show that: (i) on-resonance SL is most sensitive to chemical exchanges in the intermediate-exchange regime and is able to detect hydroxyl and amine protons on a millimolar concentration scale. Off-resonance SL and CEST approaches are sensitive to slow-exchanging protons when an optimal SL or saturation pulse power matches the exchanging rate, respectively. (ii) Offset frequency-dependent SL and CEST spectra are very similar and can be explained well with an SL model recently developed by Trott and Palmer (J Magn Reson 2002;154:157-160). (iii) The exchange rate and population of metabolite protons can be determined from offset-dependent SL or CEST spectra or from on-resonance SL relaxation dispersion measurements. (iv) The asymmetry of the magnetization transfer ratio (MTR(asym)) is highly dependent on the choice of saturation pulse power. In the intermediate-exchange regime, MTR(asym) becomes complicated and should be interpreted with care. Copyright © 2010 Wiley-Liss, Inc.

  7. Does nitrogen saturation theory apply to unpolluted temperate forests? A test along a forest soil nitrogen gradient in Oregon

    Science.gov (United States)

    Perakis, S. S.; Sinkhorn, E. R.

    2011-12-01

    Natural gradients of soil nitrogen (N) can be used to evaluate the consequences of long-term ecosystem N enrichment, and to test the applicability of N saturation theory as a general framework for understanding ecosystem N dynamics. Temperate forest soils of the Oregon Coast Range experience low rates of atmospheric N deposition, yet display among the highest soil N accumulations ever reported worldwide. We measured plant and soil (0-1m) N stocks and natural abundance delta15N, plant production, N uptake and return in litterfall, soil gross and net N mineralization rates, and hydrologic N losses of nine Douglas-fir forests growing across an exceptionally wide soil N gradient in the Oregon Coast Range. Ecosystem N content ranged from 8,788 to 22,667 kg N/ha across sites, with highest N accumulations near the coast, and 96-98% of total ecosystem N residing in mineral soil. Ecosystem delta15N displayed a curvilinear relationship with ecosystem N content that reflected competing influences of N input from biological fixation at low-N sites and fractionating N losses at high-N sites. Simulation modeling of ecosystem N and delta15N mass balance suggest that cycles of wildfire can promote unusually high natural N accumulation by fostering early successional biological nitrogen fixation. Surface mineral soil (0 - 10 cm) N concentrations were tightly correlated to total soil N stocks to 1 m depth, and in contrast to predictions of N saturation theory, were linearly related to 10-fold variation in net N mineralization from 8 - 82 kg N/ha-yr. Net N mineralization was unrelated to soil C:N, soil texture, precipitation and temperature differences among sites. Net nitrification accounted for pH decline from 5.8 to 4.1 across sites. The ratio of net:gross N mineralization and nitrification increased along the gradient, indicating progressive saturation of microbial N demands at high soil N. Aboveground N uptake by plants increased asymptotically with net N mineralization to a

  8. MRI

    Science.gov (United States)

    ... and radio waves to create pictures of the body. It does not use radiation (x-rays). Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of ...

  9. Angular Momentum Transport in Protoplanetary and Black Hole Accretion Disks: The Role of Parasitic Modes in the Saturation of MHD Turbulence

    DEFF Research Database (Denmark)

    Pessah, Martin Elias

    2010-01-01

    The magnetorotational instability (MRI) is considered a key process for driving efficient angular momentum transport in astrophysical disks. Understanding its nonlinear saturation constitutes a fundamental problem in modern accretion disk theory. The large dynamical range in physical conditions i...

  10. Is Bonferroni correction more sensitive than Random Field Theory for most fMRI studies?

    CERN Document Server

    Tierney, Tim M; Carmichael, David W

    2016-01-01

    Random Field Theory has been used in the fMRI literature to address the multiple comparisons problem. The method provides an analytical solution for the computation of precise p-values when its assumptions are met. When its assumptions are not met the thresholds generated by Random Field Theory can be more conservative than Bonferroni corrections, which are arguably too stringent for use in fMRI. As this has been well documented theoretically it is surprising that a majority of current studies (~80%) would not meet the assumptions of Random Field Theory and therefore would have reduced sensitivity. Specifically most data is not smooth enough to meet the good lattice assumption. Current studies smooth data on average by twice the voxel size which is rarely sufficient to meet the good lattice assumption. The amount of smoothing required for Random Field Theory to produce accurate p-values increases with image resolution and decreases with degrees of freedom. There is no rule of thumb that is valid for all study...

  11. Testing simulation theory with cross-modal multivariate classification of fMRI data.

    Directory of Open Access Journals (Sweden)

    Joset A Etzel

    Full Text Available The discovery of mirror neurons has suggested a potential neural basis for simulation and common coding theories of action perception, theories which propose that we understand other people's actions because perceiving their actions activates some of our neurons in much the same way as when we perform the actions. We propose testing this model directly in humans with functional magnetic resonance imaging (fMRI by means of cross-modal classification. Cross-modal classification evaluates whether a classifier that has learned to separate stimuli in the sensory domain can also separate the stimuli in the motor domain. Successful classification provides support for simulation theories because it means that the fMRI signal, and presumably brain activity, is similar when perceiving and performing actions. In this paper we demonstrate the feasibility of the technique by showing that classifiers which have learned to discriminate whether a participant heard a hand or a mouth action, based on the activity patterns in the premotor cortex, can also determine, without additional training, whether the participant executed a hand or mouth action. This provides direct evidence that, while perceiving others' actions, (1 the pattern of activity in premotor voxels with sensory properties is a significant source of information regarding the nature of these actions, and (2 that this information shares a common code with motor execution.

  12. Testing simulation theory with cross-modal multivariate classification of fMRI data.

    Science.gov (United States)

    Etzel, Joset A; Gazzola, Valeria; Keysers, Christian

    2008-01-01

    The discovery of mirror neurons has suggested a potential neural basis for simulation and common coding theories of action perception, theories which propose that we understand other people's actions because perceiving their actions activates some of our neurons in much the same way as when we perform the actions. We propose testing this model directly in humans with functional magnetic resonance imaging (fMRI) by means of cross-modal classification. Cross-modal classification evaluates whether a classifier that has learned to separate stimuli in the sensory domain can also separate the stimuli in the motor domain. Successful classification provides support for simulation theories because it means that the fMRI signal, and presumably brain activity, is similar when perceiving and performing actions. In this paper we demonstrate the feasibility of the technique by showing that classifiers which have learned to discriminate whether a participant heard a hand or a mouth action, based on the activity patterns in the premotor cortex, can also determine, without additional training, whether the participant executed a hand or mouth action. This provides direct evidence that, while perceiving others' actions, (1) the pattern of activity in premotor voxels with sensory properties is a significant source of information regarding the nature of these actions, and (2) that this information shares a common code with motor execution.

  13. Active control of the spatial MRI phase distribution with optimal control theory

    Science.gov (United States)

    Lefebvre, Pauline M.; Van Reeth, Eric; Ratiney, Hélène; Beuf, Olivier; Brusseau, Elisabeth; Lambert, Simon A.; Glaser, Steffen J.; Sugny, Dominique; Grenier, Denis; Tse Ve Koon, Kevin

    2017-08-01

    This paper investigates the use of Optimal Control (OC) theory to design Radio-Frequency (RF) pulses that actively control the spatial distribution of the MRI magnetization phase. The RF pulses are generated through the application of the Pontryagin Maximum Principle and optimized so that the resulting transverse magnetization reproduces various non-trivial and spatial phase patterns. Two different phase patterns are defined and the resulting optimal pulses are tested both numerically with the ODIN MRI simulator and experimentally with an agar gel phantom on a 4.7 T small-animal MR scanner. Phase images obtained in simulations and experiments are both consistent with the defined phase patterns. A practical application of phase control with OC-designed pulses is also presented, with the generation of RF pulses adapted for a Magnetic Resonance Elastography experiment. This study demonstrates the possibility to use OC-designed RF pulses to encode information in the magnetization phase and could have applications in MRI sequences using phase images.

  14. Incidental Memory Encoding Assessed with Signal Detection Theory and Functional Magnetic Resonance Imaging (fMRI).

    Science.gov (United States)

    Clemens, Benjamin; Regenbogen, Christina; Koch, Kathrin; Backes, Volker; Romanczuk-Seiferth, Nina; Pauly, Katharina; Shah, N Jon; Schneider, Frank; Habel, Ute; Kellermann, Thilo

    2015-01-01

    In functional magnetic resonance imaging (fMRI) studies that apply a "subsequent memory" approach, successful encoding is indicated by increased fMRI activity during the encoding phase for hits vs. misses, in areas underlying memory encoding such as the hippocampal formation. Signal-detection theory (SDT) can be used to analyze memory-related fMRI activity as a function of the participant's memory trace strength (d(')). The goal of the present study was to use SDT to examine the relationship between fMRI activity during incidental encoding and participants' recognition performance. To implement a new approach, post-experimental group assignment into High- or Low Performers (HP or LP) was based on 29 healthy participants' recognition performance, assessed with SDT. The analyses focused on the interaction between the factors group (HP vs. LP) and recognition performance (hits vs. misses). A whole-brain analysis revealed increased activation for HP vs. LP during incidental encoding for remembered vs. forgotten items (hits > misses) in the insula/temporo-parietal junction (TPJ) and the fusiform gyrus (FFG). Parameter estimates in these regions exhibited a significant positive correlation with d('). As these brain regions are highly relevant for salience detection (insula), stimulus-driven attention (TPJ), and content-specific processing of mnemonic stimuli (FFG), we suggest that HPs' elevated memory performance was associated with enhanced attentional and content-specific sensory processing during the encoding phase. We provide first correlative evidence that encoding-related activity in content-specific sensory areas and content-independent attention and salience detection areas influences memory performance in a task with incidental encoding of facial stimuli. Based on our findings, we discuss whether the aforementioned group differences in brain activity during incidental encoding might constitute the basis of general differences in memory performance between HP and

  15. Identifying patients with Alzheimer's disease using resting-state fMRI and graph theory.

    Science.gov (United States)

    Khazaee, Ali; Ebrahimzadeh, Ata; Babajani-Feremi, Abbas

    2015-11-01

    Study of brain network on the basis of resting-state functional magnetic resonance imaging (fMRI) has provided promising results to investigate changes in connectivity among different brain regions because of diseases. Graph theory can efficiently characterize different aspects of the brain network by calculating measures of integration and segregation. In this study, we combine graph theoretical approaches with advanced machine learning methods to study functional brain network alteration in patients with Alzheimer's disease (AD). Support vector machine (SVM) was used to explore the ability of graph measures in diagnosis of AD. We applied our method on the resting-state fMRI data of twenty patients with AD and twenty age and gender matched healthy subjects. The data were preprocessed and each subject's graph was constructed by parcellation of the whole brain into 90 distinct regions using the automated anatomical labeling (AAL) atlas. The graph measures were then calculated and used as the discriminating features. Extracted network-based features were fed to different feature selection algorithms to choose most significant features. In addition to the machine learning approach, statistical analysis was performed on connectivity matrices to find altered connectivity patterns in patients with AD. Using the selected features, we were able to accurately classify patients with AD from healthy subjects with accuracy of 100%. Results of this study show that pattern recognition and graph of brain network, on the basis of the resting state fMRI data, can efficiently assist in the diagnosis of AD. Classification based on the resting-state fMRI can be used as a non-invasive and automatic tool to diagnosis of Alzheimer's disease. Copyright © 2015 International Federation of Clinical Neurophysiology. All rights reserved.

  16. Breast MRI at Very Short TE (minTE): Image Analysis of minTE Sequences on Non-Fat-Saturated, Subtracted T1-Weighted Images.

    Science.gov (United States)

    Wenkel, Evelyn; Janka, Rolf; Geppert, Christian; Kaemmerer, Nadine; Hartmann, Arndt; Uder, Michael; Hammon, Matthias; Brand, Michael

    2017-02-01

    Purpose The aim was to evaluate a minimum echo time (minTE) protocol for breast magnetic resonance imaging (MRI) in patients with breast lesions compared to a standard TE (nTE) time protocol. Methods Breasts of 144 women were examined with a 1.5 Tesla MRI scanner. Additionally to the standard gradient-echo sequence with nTE (4.8 ms), a variant with minimum TE (1.2 ms) was used in an interleaved fashion which leads to a better temporal resolution and should reduce the scan time by approximately 50 %. Lesion sizes were measured and the signal-to-noise ratio (SNR) as well as the contrast-to-noise ratio (CNR) were calculated. Subjective confidence was evaluated using a 3-point scale before looking at the nTE sequences (1 = very sure that I can identify a lesion and classify it, 2 = quite sure that I can identify a lesion and classify it, 3 = definitely want to see nTE for final assessment) and the subjective image quality of all examinations was evaluated using a four-grade scale (1 = sharp, 2 = slight blur, 3 = moderate blur and 4 = severe blur/not evaluable) for lesion and skin sharpness. Lesion morphology and contrast enhancement were also evaluated. Results With minTE sequences, no lesion was rated with "definitely want to see nTE sequences for final assessment". The difference of the longitudinal and transverse diameter did not differ significantly (p > 0.05). With minTE, lesions and skin were rated to be significantly more blurry (p Image Analysis of minTE Sequences on Non-Fat-Saturated, Subtracted T1-Weighted Images. Fortschr Röntgenstr 2017; 189: 137 - 145. © Georg Thieme Verlag KG Stuttgart · New York.

  17. Causality Analysis of fMRI Data Based on the Directed Information Theory Framework.

    Science.gov (United States)

    Wang, Zhe; Alahmadi, Ahmed; Zhu, David C; Li, Tongtong

    2016-05-01

    This paper aims to conduct fMRI-based causality analysis in brain connectivity by exploiting the directed information (DI) theory framework. Unlike the well-known Granger causality (GC) analysis, which relies on the linear prediction technique, the DI theory framework does not have any modeling constraints on the sequences to be evaluated and ensures estimation convergence. Moreover, it can be used to generate the GC graphs. In this paper, first, we introduce the core concepts in the DI framework. Second, we present how to conduct causality analysis using DI measures between two time series. We provide the detailed procedure on how to calculate the DI for two finite-time series. The two major steps involved here are optimal bin size selection for data digitization and probability estimation. Finally, we demonstrate the applicability of DI-based causality analysis using both the simulated data and experimental fMRI data, and compare the results with that of the GC analysis. Our analysis indicates that GC analysis is effective in detecting linear or nearly linear causal relationship, but may have difficulty in capturing nonlinear causal relationships. On the other hand, DI-based causality analysis is more effective in capturing both linear and nonlinear causal relationships. Moreover, it is observed that brain connectivity among different regions generally involves dynamic two-way information transmissions between them. Our results show that when bidirectional information flow is present, DI is more effective than GC to quantify the overall causal relationship.

  18. Partitioning in REE-saturating minerals - Theory, experiment, and modelling of whitlockite, apatite, and evolution of lunar residual magmas

    Science.gov (United States)

    Jolliff, Bradley L.; Haskin, Larry A.; Colson, Russell O.; Wadhwa, Meenakshi

    1993-01-01

    Compositions, including REEs determined by ion microprobe, of apatite and whitlockite in lunar rock assemblages rich in incompatible trace elements, are presented. Concentrations of REEs in lunar whitlockites are high, ranging from about 1.2 to 2.1 REEs (lanthanides + Y) per 56 oxygens. This slightly exceeds the level of two REE atoms per 56 oxygens at which the dominant substitution theoretically becomes saturated. This saturation effect leads to whitlockite REE(3+) D values at typical lunar whitlockite REE concentrations which are 30-40 percent lower than the D values at low concentrations. The halogen-to-phosphorous ratio in lunar melts is a key factor determining the REE distribution with crystalline assemblages. As long as P and REE concentrations of melts are in KREEP-like proportions, one or both of the phosphates will saturate in melts at similar REE concentrations.

  19. Risk of Upgrading from Prostate Biopsy to Radical Prostatectomy Pathology: Does Saturation Biopsy of Index Lesion during mpMRI-TRUS Fusion Biopsy Help?

    Science.gov (United States)

    Calio, Brian P; Sidana, Abhinav; Sugano, Dordaneh; Gaur, Sonia; Maruf, Mahir; Jain, Amit L; Merino, Maria J; Choyke, Peter L; Wood, Bradford J; Pinto, Peter A; Turkbey, Baris

    2018-01-19

    We sought to determine whether saturation of the index lesion during magnetic resonance imaging-transrectal ultrasound fusion guided biopsy would decrease the rate of pathological upgrading from biopsy to radical prostatectomy. We analyzed a prospectively maintained, single institution database for patients who underwent fusion and systematic biopsy followed by radical prostatectomy in 2010 to 2016. Index lesion was defined as the lesion with largest diameter on T2-weighted magnetic resonance imaging. In patients with a saturated index lesion transrectal fusion biopsy targets were obtained at 6 mm intervals along the long axis of the index lesion. In patients with a nonsaturated index lesion only 1 target was obtained from the lesion. Gleason 6, 7 and 8-10 were defined as low, intermediate and high risk, respectively. Included in study were 208 consecutive patients, including 86 with a saturated and 122 with a nonsaturated lesion. Median patient age was 62.0 years (IQR 10.0) and median prostate specific antigen was 7.1 ng/ml (IQR 8.0). The median number of biopsy cores per index lesion was higher in the saturated lesion group (4 vs 2, p lesion group (7 vs 18%, p = 0.021). There was no difference in the upgrade rate based on systematic biopsy between the 2 groups. However, fusion biopsy results were significantly less upgraded in the saturated lesion group (Gleason upgrade 20.9% vs 36.9%, p = 0.014 and risk category upgrade 14% vs 30.3%, p = 0.006). Our results demonstrate that saturation of the index lesion significantly decreases the risk of upgrading on radical prostatectomy by minimizing the impact of tumor heterogeneity. Copyright © 2018 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

  20. Rain-Impact-Entrainment of Chemicals and Soil into Overland Flow in Saturated Areas: Theory and Experiments

    Science.gov (United States)

    Walter, M.; Gao, B.; Parlange, J.; Steenhuis, T. S.

    2004-12-01

    Overland flow from riparian and other frequently saturated areas is a potentially important transport pathway between the landscape and aquatic ecosystems. Both raindrop driven processes and diffusion play important roles in the transfer of chemicals from soil to surface runoff, however, current transport models either do not consider the two processes together, or use "effective" parameters with uncertain physical definitions. We developed a physically based, solute transport model that couples both mechanisms and tested it with experimental data. One unique aspect of this study is that all the parameters needed to apply the model to our experiments were either directly measured or previously published, that is, there was no model "calibration" or "fitting." Our model assumes that chemicals near the surface of the soil are ejected into runoff by raindrop impact and chemicals deeper in the soil diffuse into a surface layer, or "exchange layer," via diffusion. The exchange layer depth and transfer processes are derived from the "shield" concept in the Rose soil erosion model (e.g., Rose, 1985, Adv. Soil Sci. 2,1-63.). The model's governing equations were solved numerically and the results agreed well with experimental data (R2 > 0.90). The model was also successfully tested against previously published experimental data by Leman and Ahuja (1983, J. Environ. Qual. 12(1), 34-40); these data were unique because they provided chemical concentrations in the soil profile as well as in the overland flow. This model provides insights into important processes relevant to landscape-river interactions and water quality protection.

  1. The value of fat saturation sequences and contrast medium administration in MRI of degenerative disease of the posterior/perispinal elements of the lumbosacral spine

    Energy Technology Data Exchange (ETDEWEB)

    D' Aprile, P. [San Paolo Hospital, Department of Neuroradiology, Bari (Italy); U.O. Radiologia, Sezione di Neuroradiologia, Ospedale ' ' S. Paolo' ' , Via Caposcardicchio, Bari (Italy); Tarantino, A. [San Paolo Hospital, Department of Neuroradiology, Bari (Italy); Jinkins, J.R. [State University of New York, Department of Radiology, Downstate Medical Center, Brooklyn, NY (United States); Brindicci, D. [San Paolo Hospital, Department of Radiology, Bari (Italy)

    2007-02-15

    Degenerative-inflammatory lumbar spinal pathology is one of the most common reasons why individuals seek medical care, and low back pain is the main symptom among those most commonly associated with this pathologic condition. Pain is commonly attributed to degenerative disc disease, particularly herniated discs, but many different spinal and perispinal structures may undergo degenerative-inflammatory phenomena and produce pain: discs, bone, facet joints, ligaments and muscles. In particular, in patients with non-radicular low back pain, this syndrome may arise from changes of the posterior elements/perispinal tissues of the lumbar spine (i.e., the ''posterior vertebral compartment''). They include: facet joint pathology (e.g., osteoarthritis, joint effusion, synovitis and synovial cysts), spondylolysis, spinal/perispinal ligamentous degenerative-inflammatory changes and perispinal muscular changes. It is well known that magnetic resonance is the most sensitive imaging method for the evaluation of spinal degenerative pathology, even in the initial stages of the disease. T2-weighted sequences with fat saturation, and when indicated the use of contrast-enhanced T1-weighted images with fat saturation, permit the visualization of degenerative-inflammatory changes of the posterior elements of the lumbar spine that in most cases would have been overlooked with conventional non-fat suppressed imaging. (orig.)

  2. Breast MRI at very short TE (minTE). Image analysis of minTE sequences on non-fat-saturated, subtracted T1-weighted images

    Energy Technology Data Exchange (ETDEWEB)

    Wenkel, Evelyn; Janka, Rolf; Kaemmerer, Nadine; Uder, Michael; Hammon, Matthias; Brand, Michael [Univ. Hospital Erlangen (Germany). Dept. of Radiology; Geppert, Christian [Siemens Healthcare GmbH, Erlangen (Germany); Hartmann, Arndt [Univ. Hospital Erlangen (Germany). Dept. of Pathology

    2017-02-15

    The aim was to evaluate a minimum echo time (minTE) protocol for breast magnetic resonance imaging (MRI) in patients with breast lesions compared to a standard TE (nTE) time protocol. Breasts of 144 women were examined with a 1.5 Tesla MRI scanner. Additionally to the standard gradient-echo sequence with nTE (4.8 ms), a variant with minimum TE (1.2 ms) was used in an interleaved fashion which leads to a better temporal resolution and should reduce the scan time by approximately 50%. Lesion sizes were measured and the signal-to-noise ratio (SNR) as well as the contrast-to-noise ratio (CNR) were calculated. Subjective confidence was evaluated using a 3-point scale before looking at the nTE sequences (1 = very sure that I can identify a lesion and classify it, 2 = quite sure that I can identify a lesion and classify it, 3 = definitely want to see nTE for final assessment) and the subjective image quality of all examinations was evaluated using a four-grade scale (1 = sharp, 2 = slight blur, 3 = moderate blur and 4 = severe blur/not evaluable) for lesion and skin sharpness. Lesion morphology and contrast enhancement were also evaluated. With minTE sequences, no lesion was rated with ''definitely want to see nTE sequences for final assessment''. The difference of the longitudinal and transverse diameter did not differ significantly (p>0.05). With minTE, lesions and skin were rated to be significantly more blurry (p<0.01 for lesions and p<0.05 for skin). There was no difference between both sequences with respect to SNR, CNR, lesion morphology, contrast enhancement and detection of multifocal disease. Dynamic breast MRI with a minTE protocol is feasible without a major loss of information (SNR, CNR, lesion morphology, contrast enhancement and lesion sizes) and the temporal resolution can be increased by a factor of 2 using minTE sequences.

  3. Intradiurnal fluctuations of off-resonance saturation effects in healthy human achilles tendons assessed with a 3D ultrashort echo time MRI sequence at 3 tesla

    Energy Technology Data Exchange (ETDEWEB)

    Grosse, U.; Syha, R.; Kessler, D.E.; Bongers, M.; Seith, F.; Nikolaou, K.; Springer, F. [University Hospital Tuebingen (Germany). Dept. of Diagnostic and Interventional Radiology; Partovi, S.; Robbin, M. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Radiology; Schick, F. [University Hospital Tuebingen (Germany). Section on Experimental Radiology

    2015-11-15

    The purpose of this study was to evaluate whether gravitational interstitial fluid accumulation in healthy subjects has an impact on off-resonance saturation ratios (OSR) or the volume of the Achilles tendon after a prolonged time of reduced levels of physical activity. 7 healthy volunteers were repeatedly investigated on 3 consecutive days on a 3 T whole body MR scanner using an ultrashort echo time (UTE) imaging sequence with a Gaussian off-resonance saturation pulse at a frequency offset of 2000 Hz to calculate OSR values. For accurate volumetric quantification of the Achilles tendon, a newly developed contour detection snake algorithm was applied on high-resolution isotropic T2-weighted SPACE sequence datasets. Single-measure intraclass correlation coefficients (ICC) were calculated to estimate test-retest reliability. For OSR and tendon volume measurements on three consecutive days, excellent reproducibility could be achieved with ICC values above 0.96 and 0.97, respectively. Comparing the results of all three days, a statistically significant mean individual percentage decrease (-4.1 ± 1.5 %; p=0.001) of calculated tendon OSR values was found for the evening measurements. No statistically significant difference between tendon volumes in the morning and the evening could be detected (p=0.589). The results of this in-vivo study demonstrate a significant influence of gravitational interstitial fluid accumulation after reduced physical activity on OSR values in the Achilles tendon, but not on tendon volume. Taken together with the demonstrated excellent reproducibility, these findings are important for future studies investigating temporal changes of the Achilles tendon microstructure.

  4. Testing Simulation Theory with Cross-Modal Multivariate Classification of fMRI Data

    NARCIS (Netherlands)

    Etzel, Joset A.; Gazzola, Valeria; Keysers, Christian

    2008-01-01

    The discovery of mirror neurons has suggested a potential neural basis for simulation and common coding theories of action perception, theories which propose that we understand other people's actions because perceiving their actions activates some of our neurons in much the same way as when we

  5. Abnormal functional resting-state networks in ADHD: graph theory and pattern recognition analysis of fMRI data.

    Science.gov (United States)

    dos Santos Siqueira, Anderson; Biazoli Junior, Claudinei Eduardo; Comfort, William Edgar; Rohde, Luis Augusto; Sato, João Ricardo

    2014-01-01

    The framework of graph theory provides useful tools for investigating the neural substrates of neuropsychiatric disorders. Graph description measures may be useful as predictor variables in classification procedures. Here, we consider several centrality measures as predictor features in a classification algorithm to identify nodes of resting-state networks containing predictive information that can discriminate between typical developing children and patients with attention-deficit/hyperactivity disorder (ADHD). The prediction was based on a support vector machines classifier. The analyses were performed in a multisite and publicly available resting-state fMRI dataset of healthy children and ADHD patients: the ADHD-200 database. Network centrality measures contained little predictive information for the discrimination between ADHD patients and healthy subjects. However, the classification between inattentive and combined ADHD subtypes was more promising, achieving accuracies higher than 65% (balance between sensitivity and specificity) in some sites. Finally, brain regions were ranked according to the amount of discriminant information and the most relevant were mapped. As hypothesized, we found that brain regions in motor, frontoparietal, and default mode networks contained the most predictive information. We concluded that the functional connectivity estimations are strongly dependent on the sample characteristics. Thus different acquisition protocols and clinical heterogeneity decrease the predictive values of the graph descriptors.

  6. Heart MRI

    Science.gov (United States)

    Magnetic resonance imaging - cardiac; Magnetic resonance imaging - heart; Nuclear magnetic resonance - cardiac; NMR - cardiac; MRI of the heart; Cardiomyopathy - MRI; Heart failure - MRI; Congenital heart disease - MRI

  7. [From Descartes to fMRI. Pain theories and pain concepts].

    Science.gov (United States)

    Handwerker, H O

    2007-08-01

    In the seventeenth century the philosopher Rene Descartes was the forerunner by establishing a scientific hypothesis on the origin of pain. Much later, in the nineteenth century, pain hypotheses emerged which explained the pain sensation either on the basis of intense stimulation of any kind of nerve fibers (intensity hypothesis) or on the basis of specific nociceptors (specificity hypothesis). The "gate control theory" established by Melzack and Wall (1964) offered an explanation of modulations of pain sensation by the interaction between nociceptive and non-nociceptive nerve fibers and by descending control in the central nervous system. Though this hypothesis is outdated in its original form, it had - in a more common formulation - a great influence on our understanding of pain. For building a bridge to our present knowledge, the molecular structure of the nociceptor membrane is of particular importance. On this basis also new pain therapies have been developed. On the other hand, the methods of functional imaging allow the identification of brain regions related to pain processing at a macroscopic level. This new technology opened up new ways of understanding chronic pain processes and new possibilities for the control of therapeutic effects.

  8. Increased segregation of brain networks in focal epilepsy: An fMRI graph theory finding.

    Science.gov (United States)

    Pedersen, Mangor; Omidvarnia, Amir H; Walz, Jennifer M; Jackson, Graeme D

    2015-01-01

    Focal epilepsy is conceived of as activating local areas of the brain as well as engaging regional brain networks. Graph theory represents a powerful quantitative framework for investigation of brain networks. Here we investigate whether functional network changes are present in extratemporal focal epilepsy. Task-free functional magnetic resonance imaging data from 15 subjects with extratemporal epilepsy and 26 age and gender matched healthy controls were used for analysis. Local network properties were calculated using local efficiency, clustering coefficient and modularity metrics. Global network properties were assessed with global efficiency and betweenness centrality metrics. Cost-efficiency of the networks at both local and global levels was evaluated by estimating the physical distance between functionally connected nodes, in addition to the overall numbers of connections in the network. Clustering coefficient, local efficiency and modularity were significantly higher in individuals with focal epilepsy than healthy control subjects, while global efficiency and betweenness centrality were not significantly different between the two groups. Local network properties were also highly efficient, at low cost, in focal epilepsy subjects compared to healthy controls. Our results show that functional networks in focal epilepsy are altered in a way that the nodes of the network are more isolated. We postulate that network regularity, or segregation of the nodes of the networks, may be an adaptation that inhibits the conversion of the interictal state to seizures. It remains possible that this may be part of the epileptogenic process or an effect of medications.

  9. Facts about saturated fats

    Science.gov (United States)

    ... fat diary with low-fat or nonfat milk, yogurt, and cheese. Eat more fruits, vegetables, whole grains, and other foods with low or no saturated fat. Alternative Names Cholesterol - saturated fat; Atherosclerosis - saturated fat; Hardening of the ...

  10. Saturated fat (image)

    Science.gov (United States)

    Saturated fat can raise blood cholesterol and can put you at risk for heart disease and stroke. You should ... limit any foods that are high in saturated fat. Sources of saturated fat include whole-milk dairy ...

  11. Shoulder MRI

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Shoulder Magnetic resonance imaging (MRI) of the shoulder ... limitations of MRI of the shoulder? What is MRI of the shoulder? MRI of the shoulder provides ...

  12. Knee MRI

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Knee Magnetic resonance imaging (MRI) of the knee ... of a knee MRI? What is a Knee MRI? MRI of the knee provides detailed images of ...

  13. Slow light in saturable absorbers

    OpenAIRE

    Macke, Bruno; Ségard, Bernard

    2008-01-01

    International audience; In connection with the experiments recently achieved on doped crystals, biological samples, doped optical fibers and semiconductor heterostructures, we revisit the theory of the propagation of a pulse-modulated light in a saturable absorber. Explicit analytical expressions of the transmitted pulse are obtained, enabling us to determine the parameters optimizing the time-delay of the transmitted pulse with respect to the incident pulse. We finally compare the maximum fr...

  14. Saturation of Van Allen's belts

    CERN Document Server

    Le Bel, E

    2002-01-01

    The maximum number of electrons that can be trapped in van Allen's belts has been evaluated at CEA-DAM more precisely than that commonly used in the space community. The modelization that we have developed allows to understand the disagreement (factor 50) observed between the measured and predicted electrons flux by US satellites and theory. This saturation level allows sizing-up of the protection on a satellite in case of energetic events. (authors)

  15. Saturated Switching Systems

    CERN Document Server

    Benzaouia, Abdellah

    2012-01-01

    Saturated Switching Systems treats the problem of actuator saturation, inherent in all dynamical systems by using two approaches: positive invariance in which the controller is designed to work within a region of non-saturating linear behaviour; and saturation technique which allows saturation but guarantees asymptotic stability. The results obtained are extended from the linear systems in which they were first developed to switching systems with uncertainties, 2D switching systems, switching systems with Markovian jumping and switching systems of the Takagi-Sugeno type. The text represents a thoroughly referenced distillation of results obtained in this field during the last decade. The selected tool for analysis and design of stabilizing controllers is based on multiple Lyapunov functions and linear matrix inequalities. All the results are illustrated with numerical examples and figures many of them being modelled using MATLAB®. Saturated Switching Systems will be of interest to academic researchers in con...

  16. Social network theory applied to resting-state fMRI connectivity data in the identification of epilepsy networks with iterative feature selection.

    Science.gov (United States)

    Zhang, Xiaohui; Tokoglu, Fuyuze; Negishi, Michiro; Arora, Jagriti; Winstanley, Scott; Spencer, Dennis D; Constable, R Todd

    2011-07-15

    Epilepsy is a brain disorder usually associated with abnormal cortical and/or subcortical functional networks. Exploration of the abnormal network properties and localization of the brain regions involved in human epilepsy networks are critical for both the understanding of the epilepsy networks and planning therapeutic strategies. Currently, most localization of seizure networks come from ictal EEG observations. Functional MRI provides high spatial resolution together with more complete anatomical coverage compared with EEG and may have advantages if it can be used to identify the network(s) associated with seizure onset and propagation. Epilepsy networks are believed to be present with detectable abnormal signatures even during the interictal state. In this study, epilepsy networks were investigated using resting-state fMRI acquired with the subjects in the interictal state. We tested the hypothesis that social network theory applied to resting-state fMRI data could reveal abnormal network properties at the group level. Using network data as input to a classification algorithm allowed separation of medial temporal lobe epilepsy (MTLE) patients from normal control subjects indicating the potential value of such network analyses in epilepsy. Five local network properties obtained from 36 anatomically defined ROIs were input as features to the classifier. An iterative feature selection strategy based on the classification efficiency that can avoid 'over-fitting' is proposed to further improve the classification accuracy. An average sensitivity of 77.2% and specificity of 83.86% were achieved via 'leave one out' cross validation. This finding of significantly abnormal network properties in group level data confirmed our initial hypothesis and provides motivation for further investigation of the epilepsy process at the network level. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Integrating MRI brain imaging studies of pre-reading children with current theories of developmental dyslexia: A review and quantitative meta-analysis.

    Science.gov (United States)

    Vandermosten, Maaike; Hoeft, Fumiko; Norton, Elizabeth S

    2016-08-01

    The neurobiological substrates that cause people with dyslexia to experience difficulty in acquiring accurate and fluent reading skills are still largely unknown. Although structural and functional brain anomalies associated with dyslexia have been reported in adults and school-age children, these anomalies may represent differences in reading experience rather than the etiology of dyslexia. Conducting MRI studies of pre-readers at risk for dyslexia is one approach that enables us to identify brain alterations that exist before differences in reading experience emerge. The current review summarizes MRI studies that examine brain differences associated with risk for dyslexia in children before reading instruction and meta-analyzes these studies. In order to link these findings with current etiological theories of dyslexia, we focus on studies that take a modular perspective rather than a network approach. Although some of the observed differences in pre-readers at risk for dyslexia may still be shaped by language experiences during the first years of life, such studies underscore the existence of reading-related brain anomalies prior to reading onset and could eventually lead to earlier and more precise diagnosis and treatment of dyslexia.

  18. Chest MRI

    Science.gov (United States)

    Nuclear magnetic resonance - chest; Magnetic resonance imaging - chest; NMR - chest; MRI of the thorax; Thoracic MRI ... healthy enough to filter the contrast. During the MRI, the person who operates the machine will watch ...

  19. Wave propagation in thermoelastic saturated porous medium

    Indian Academy of Sciences (India)

    Biot 's theory for wave propagation in saturated porous solid is modified to study the propagation of thermoelastic waves in poroelastic medium. Propagation of plane harmonic waves is considered in isotropic poroelastic medium. Relations are derived among the wave-induced temperature in the medium and the ...

  20. MRI Scans

    Science.gov (United States)

    Magnetic resonance imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from ...

  1. Venous oxygen saturation.

    Science.gov (United States)

    Hartog, Christiane; Bloos, Frank

    2014-12-01

    Early detection and rapid treatment of tissue hypoxia are important goals. Venous oxygen saturation is an indirect index of global oxygen supply-to-demand ratio. Central venous oxygen saturation (ScvO2) measurement has become a surrogate for mixed venous oxygen saturation (SvO2). ScvO2 is measured by a catheter placed in the superior vena cava. After results from a single-center study suggested that maintaining ScvO2 values >70% might improve survival rates in septic patients, international practice guidelines included this target in a bundle strategy to treat early sepsis. However, a recent multicenter study with >1500 patients found that the use of central hemodynamic and ScvO2 monitoring did not improve long-term survival when compared to the clinical assessment of the adequacy of circulation. It seems that if sepsis is recognized early, a rapid initiation of antibiotics and adequate fluid resuscitation are more important than measuring venous oxygen saturation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Metamaterial saturable absorber mirror.

    Science.gov (United States)

    Dayal, Govind; Ramakrishna, S Anantha

    2013-02-01

    We propose a metamaterial saturable absorber mirror at midinfrared wavelengths that can show a saturation of absorption with intensity of incident light and switch to a reflecting state. The design consists of an array of circular metallic disks separated by a thin film of vanadium dioxide (VO(2)) from a continuous metallic film. The heating due to the absorption in the absorptive state causes the VO(2) to transit to a metallic phase from the low temperature insulating phase. The metamaterial switches from an absorptive state (R≃0.1%) to a reflective state (R>95%) for a specific threshold intensity of the incident radiation corresponding to the phase transition of VO(2), resulting in the saturation of absorption in the metamaterial. The computer simulations show over 99.9% peak absorbance, a resonant bandwidth of about 0.8 μm at 10.22 μm wavelengths, and saturation intensity of 140 mW cm(-2) for undoped VO(2) at room temperature. We also carried out numerical simulations to investigate the effects of localized heating and temperature distribution by solving the heat diffusion problem.

  3. Saturated and trans fats

    National Research Council Canada - National Science Library

    Shader, Richard I

    2014-01-01

    ... Original Pancake Mix plus ingredients suggested by the recipe: 2 g saturated fat (SF) and no trans fatty acids or trans fat (TFA); bacon, Oscar Mayer Lower Sodium Bacon: 2.5 g SF and no TFA; sausages, Jimmy Dean Original Pork Sausage Links: 8 g SF and no TFA; potatoes, Ore-Ida Mini Tater Tots: 2 g SF and no TFA; and nondairy creamer, Nestlé Coffee-...

  4. Perturbative Saturation and the Soft Pomeron

    CERN Document Server

    Kovner, A; Kovner, Alex; Wiedemann, Urs Achim

    2002-01-01

    We show that perturbation theory provides two distinct mechanisms for the power like growth of hadronic cross sections at high energy. One, the leading BFKL effect is due to the growth of the parton density, and is characterized by the leading BFKL exponent. The other mechanism is due to the infrared diffusion, or the long range nature of the Coulomb field of perturbatively massless gluons. When perturbative saturation effects are taken into account, the first mechanism is rendered ineffective but the second one persists. We suggest that these two distinct mechanisms are responsible for the appearance of two pomerons. The density growth effects are responsible for the hard pomeron and manifest themselves in small systems (e.g. gamma^* or small size fluctuations in the proton wave function) where saturation effects are not important. The soft pomeron is the manifestation of the exponential growth of the black saturated regions which appear in typical hadronic systems. We point out that the nonlinear generaliza...

  5. Disconnection mechanism and regional cortical atrophy contribute to impaired processing of facial expressions and theory of mind in multiple sclerosis: a structural MRI study.

    Science.gov (United States)

    Mike, Andrea; Strammer, Erzsebet; Aradi, Mihaly; Orsi, Gergely; Perlaki, Gabor; Hajnal, Andras; Sandor, Janos; Banati, Miklos; Illes, Eniko; Zaitsev, Alexander; Herold, Robert; Guttmann, Charles R G; Illes, Zsolt

    2013-01-01

    Successful socialization requires the ability of understanding of others' mental states. This ability called as mentalization (Theory of Mind) may become deficient and contribute to everyday life difficulties in multiple sclerosis. We aimed to explore the impact of brain pathology on mentalization performance in multiple sclerosis. Mentalization performance of 49 patients with multiple sclerosis was compared to 24 age- and gender matched healthy controls. T1- and T2-weighted three-dimensional brain MRI images were acquired at 3Tesla from patients with multiple sclerosis and 18 gender- and age matched healthy controls. We assessed overall brain cortical thickness in patients with multiple sclerosis and the scanned healthy controls, and measured the total and regional T1 and T2 white matter lesion volumes in patients with multiple sclerosis. Performances in tests of recognition of mental states and emotions from facial expressions and eye gazes correlated with both total T1-lesion load and regional T1-lesion load of association fiber tracts interconnecting cortical regions related to visual and emotion processing (genu and splenium of corpus callosum, right inferior longitudinal fasciculus, right inferior fronto-occipital fasciculus, uncinate fasciculus). Both of these tests showed correlations with specific cortical areas involved in emotion recognition from facial expressions (right and left fusiform face area, frontal eye filed), processing of emotions (right entorhinal cortex) and socially relevant information (left temporal pole). Thus, both disconnection mechanism due to white matter lesions and cortical thinning of specific brain areas may result in cognitive deficit in multiple sclerosis affecting emotion and mental state processing from facial expressions and contributing to everyday and social life difficulties of these patients.

  6. Disconnection mechanism and regional cortical atrophy contribute to impaired processing of facial expressions and theory of mind in multiple sclerosis: a structural MRI study.

    Directory of Open Access Journals (Sweden)

    Andrea Mike

    Full Text Available Successful socialization requires the ability of understanding of others' mental states. This ability called as mentalization (Theory of Mind may become deficient and contribute to everyday life difficulties in multiple sclerosis. We aimed to explore the impact of brain pathology on mentalization performance in multiple sclerosis. Mentalization performance of 49 patients with multiple sclerosis was compared to 24 age- and gender matched healthy controls. T1- and T2-weighted three-dimensional brain MRI images were acquired at 3Tesla from patients with multiple sclerosis and 18 gender- and age matched healthy controls. We assessed overall brain cortical thickness in patients with multiple sclerosis and the scanned healthy controls, and measured the total and regional T1 and T2 white matter lesion volumes in patients with multiple sclerosis. Performances in tests of recognition of mental states and emotions from facial expressions and eye gazes correlated with both total T1-lesion load and regional T1-lesion load of association fiber tracts interconnecting cortical regions related to visual and emotion processing (genu and splenium of corpus callosum, right inferior longitudinal fasciculus, right inferior fronto-occipital fasciculus, uncinate fasciculus. Both of these tests showed correlations with specific cortical areas involved in emotion recognition from facial expressions (right and left fusiform face area, frontal eye filed, processing of emotions (right entorhinal cortex and socially relevant information (left temporal pole. Thus, both disconnection mechanism due to white matter lesions and cortical thinning of specific brain areas may result in cognitive deficit in multiple sclerosis affecting emotion and mental state processing from facial expressions and contributing to everyday and social life difficulties of these patients.

  7. Saturation in nuclei

    CERN Document Server

    Lappi, T

    2010-01-01

    This talk discusses some recent studies of gluon saturation in nuclei. We stress the connection between the initial condition in heavy ion collisions and observables in deep inelastic scattering (DIS). The dominant degree of freedom in the small x nuclear wavefunction is a nonperturbatively strong classical gluon field, which determines the initial condition for the glasma fields in the initial stages of a heavy ion collision. A correlator of Wilson lines from the same classical fields, known as the dipole cross section, can be used to compute many inclusive and exclusive observables in DIS.

  8. MRI of the Chest

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Chest Magnetic resonance imaging (MRI) of the chest ... limitations of MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging (MRI) is ...

  9. MRI of the Prostate

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Prostate Magnetic resonance imaging (MRI) of the prostate ... limitations of MRI of the Prostate? What is MRI of the Prostate? Magnetic resonance imaging (MRI) is ...

  10. MRI of the Breast

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Breast Magnetic resonance imaging (MRI) of the breast ... limitations of MRI of the Breast? What is MRI of the Breast? Magnetic resonance imaging (MRI) is ...

  11. MRI of the Chest

    Medline Plus

    Full Text Available ... This detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has ... Magnetic Resonance Imaging (MRI) Safety MRI Safety During Pregnancy Images related to Magnetic Resonance Imaging (MRI) - Chest ...

  12. Poole-Frenkel (PF) effect high field saturation

    OpenAIRE

    Ongaro, R.; Pillonnet, A.

    1989-01-01

    An improved Poole Frenkel (PF) effect, based upon a rigorous methodological approach, is proposed. The chosen model is stated precisely, emphasis being made explicitly on the subtending hypotheses. A systematic reference to Fermi-Dirac function, allows to establish quantitatively the concept of PF saturation. The resulting general theory integrates, as particular applications, the previous one-dimensional PF theories.

  13. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

  14. MRI zoo

    DEFF Research Database (Denmark)

    Laustsen, Christoffer

    The basic idea was to use MRI to produce a sequence of 3D gray scale image slices of various animals, subsequentlyimaged with a clinical CT system. For this purpose, these animals were used: toad, lungfish, python snake and a horseshoe crab. Each animal was sacrificed according to standard....... MRI was done using a Philips Achieva 1.5 T system and CT was performed using a Siemens Somatom system. Axial and sagittal slices were acquired using standard T1w and T2w MRI sequences, and visualization was made using the Mistar software (Apollo Imaging Technology, Melbourne, Australia). Images were...

  15. Pediatric MRI

    Data.gov (United States)

    U.S. Department of Health & Human Services — The NIH Study of Normal Brain Development is a longitudinal study using anatomical MRI, diffusion tensor imaging (DTI), and MR spectroscopy (MRS) to map pediatric...

  16. Cardiac MRI

    Science.gov (United States)

    ... Activities Obesity, Nutrition, and Physical Activity Population and Epidemiology Studies Women’s Health All Science A-Z Grants & ... interfere with the MRI machine or cause skin burns. Tattoos may cause a problem because older tattoo ...

  17. Chest MRI

    Science.gov (United States)

    ... Activities Obesity, Nutrition, and Physical Activity Population and Epidemiology Studies Women’s Health All Science A-Z Grants & ... interfere with the MRI machine or cause skin burns. Tattoos may cause a problem because older tattoo ...

  18. Head MRI

    Science.gov (United States)

    ... metal zippers, and similar metallic items Removable dental work ... test. The strong magnetic fields created during an MRI can make heart pacemakers and other implants not work as well. It can also cause a piece ...

  19. Brine Distribution after Vacuum Saturation

    DEFF Research Database (Denmark)

    Hedegaard, Kathrine; Andersen, Bertel Lohmann

    1999-01-01

    Experiments with the vacuum saturation method for brine in plugs of chalk showed that a homogeneous distribution of brine cannot be ensured at saturations below 20% volume. Instead of a homogeneous volume distribution the brine becomes concentrated close to the surfaces of the plugs...

  20. Misconceptions in Reporting Oxygen Saturation

    NARCIS (Netherlands)

    Toffaletti, John; Zijlstra, Willem G.

    2007-01-01

    BACKGROUND: We describe some misconceptions that have become common practice in reporting blood gas and cooximetry results. In 1980, oxygen saturation was incorrectly redefined in a report of a new instrument for analysis of hemoglobin (Hb) derivatives. Oxygen saturation (sO(2)) was redefined as the

  1. The potential of multiparametric MRI of the breast

    Science.gov (United States)

    Pinker, Katja; Helbich, Thomas H

    2017-01-01

    MRI is an essential tool in breast imaging, with multiple established indications. Dynamic contrast-enhanced MRI (DCE-MRI) is the backbone of any breast MRI protocol and has an excellent sensitivity and good specificity for breast cancer diagnosis. DCE-MRI provides high-resolution morphological information, as well as some functional information about neoangiogenesis as a tumour-specific feature. To overcome limitations in specificity, several other functional MRI parameters have been investigated and the application of these combined parameters is defined as multiparametric MRI (mpMRI) of the breast. MpMRI of the breast can be performed at different field strengths (1.5–7 T) and includes both established (diffusion-weighted imaging, MR spectroscopic imaging) and novel MRI parameters (sodium imaging, chemical exchange saturation transfer imaging, blood oxygen level-dependent MRI), as well as hybrid imaging with positron emission tomography (PET)/MRI and different radiotracers. Available data suggest that multiparametric imaging using different functional MRI and PET parameters can provide detailed information about the underlying oncogenic processes of cancer development and progression and can provide additional specificity. This article will review the current and emerging functional parameters for mpMRI of the breast for improved diagnostic accuracy in breast cancer. PMID:27805423

  2. Saturation of Van Allen's belts; Saturation des ceintures de Van Allen

    Energy Technology Data Exchange (ETDEWEB)

    Le Bel, E.; Simonet, F. [CEA Bruyeres-le-Chatel, 91 (France)

    2002-12-01

    The maximum number of electrons that can be trapped in van Allen's belts has been evaluated at CEA-DAM more precisely than that commonly used in the space community. The modelization that we have developed allows to understand the disagreement (factor 50) observed between the measured and predicted electrons flux by US satellites and theory. This saturation level allows sizing-up of the protection on a satellite in case of energetic events. (authors)

  3. Portable MRI

    Energy Technology Data Exchange (ETDEWEB)

    Espy, Michelle A. [Los Alamos National Laboratory

    2012-06-29

    This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2) Billions don't have access due to cost or safety issues; (3) metal will heat/move in high magnetic fields; (4) Millions of cases of traumatic brain injury in US alone; (5) even more of non-traumatic brain injury; (6) (e.g. stroke, infection, chemical exposure); (7) Need for early diagnostic; (8) 'Signature' wound of recent conflicts; (9) 22% of injuries; (10) Implications for post-traumatic stress disorder; and (11) chronic traumatic encephalopathy.

  4. Chloride diffusion in partially saturated cementitious material

    DEFF Research Database (Denmark)

    Nielsen, Erik Pram; Geiker, Mette Rica

    2003-01-01

    The paper proposes a combined application of composite theory and Powers' model for microstructural development for the estimation of the diffusion coefficient as a function of the moisture content of a defect-free cementitious material. Measurements of chloride diffusion in mortar samples (440 kg....../m(3) rapid-hardening Portland cement, w/c = 0.5, maturity minimum 6 months) stored at 65% and 85% RH, as well as in vacuum-saturated mortar samples, illustrate the applicability of the method. (C) 2003 Elsevier Science Ltd. All rights reserved....

  5. Saturation current spikes eliminated in saturable core transformers

    Science.gov (United States)

    Schwarz, F. C.

    1971-01-01

    Unsaturating composite magnetic core transformer, consisting of two separate parallel cores designed so impending core saturation causes signal generation, terminates high current spike in converter primary circuit. Simplified waveform, demonstrates transformer effectiveness in eliminating current spikes.

  6. MRI Safety during Pregnancy

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z MRI Safety During Pregnancy Magnetic resonance imaging (MRI) Illness ... during the exam? Contrast material MRI during pregnancy Magnetic resonance imaging (MRI) If you are pregnant and your doctor ...

  7. Breast MRI scan

    Science.gov (United States)

    MRI - breast; Magnetic resonance imaging - breast; Breast cancer - MRI; Breast cancer screening - MRI ... radiologist) see some areas more clearly. During the MRI, the person who operates the machine will watch ...

  8. MRI (Magnetic Resonance Imaging)

    Science.gov (United States)

    ... and Procedures Medical Imaging MRI (Magnetic Resonance Imaging) MRI (Magnetic Resonance Imaging) Share Tweet Linkedin Pin it More sharing options ... usually given through an IV in the arm. MRI Research Programs at FDA Magnetic Resonance Imaging (MRI) ...

  9. Elastic velocities of partially gas-saturated unconsolidated sediments

    Science.gov (United States)

    Lee, M.W.

    2004-01-01

    Fluid in sediments significantly affects elastic properties of sediments and gas in the pore space can be identified by a marked reduction of P-wave velocity or a decrease of Poisson's ratio. The elastic properties of gas-saturated sediments can be predicted by the classical Biot-Gassmann theory (BGT). However, parameters for the BGT such as the Biot coefficient or moduli of dry frame of unconsolidated and high porosity sediments are not readily available. Dependence of velocities on differential pressure or porosity for partially gas-saturated sediments is formulated using properties derived from velocities of water-saturated sediments. Laboratory samples for unconsolidated and consolidated sediments and well log data acquired for unconsolidated marine sediments agree well with the predictions. However, because the P-wave velocity depends highly on how the gas is saturated in the pore space such as uniform or patch, the amounts of gas estimated from the P-wave velocity contains high uncertainty. The modeled Vp/Vs ratio of partially gas-saturated sediment using the patch distribution is usually greater than 1.6, whereas the ratio modeled assuming a uniform distribution is about 1.6. Thus, Poisson's ratio or Vp/Vs ratio may be used to differentiate patch from uniform saturation, but differences between various models of patch saturation cannot be easily identified. ?? 2004 Elsevier Ltd. All rights reserved.

  10. Investigation of paramagnetic saturation in lanthanum manganese nitrate

    NARCIS (Netherlands)

    Flokstra, Jakob; Meijer, H.C.; Bots, G.J.C.; Verheij, W.A.; van der Marel, L.C.

    1973-01-01

    Paramagnetic saturation of lanthanum manganese nitrate, La2Mn3(NO3)12·24H2O, has been investigated at liquid He temperatures in a static as well as a dynamical way. With the aid of the molecular-field theory the Casimir and Du Pré dispersion and absorption curves are adapted explicitly to the

  11. Experimental Validation of the Invariance of Electrowetting Contact Angle Saturation

    NARCIS (Netherlands)

    Chevalliot, S.; Dhindsa, M.; Kuiper, S.; Heikenfeld, J.

    2011-01-01

    Basic electrowetting theory predicts that a continued increase in applied voltage will allow contact angle modulation to zero degrees. In practice, the effect of contact angle saturation has always been observed to limit the contact angle modulation, often only down to a contact angle of 60 to 70°.

  12. Surface waves in a cylindrical borehole through partially-saturated ...

    Indian Academy of Sciences (India)

    M D Sharma

    2018-02-14

    Feb 14, 2018 ... Keywords. Cylindrical waves; phase velocity; dispersion; porous solid; partial saturation; multiphase pore-fluid. Nomenclature t. Time ... on Biot's theory of poroelasticity (Biot 1956), was observed. In a later study, Chao et al. ... model and used it to obtain the analytical solution for wave propagation in a 1-D ...

  13. MRI of the Chest

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Chest Magnetic resonance imaging (MRI) of the chest ... limitations of MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging (MRI) is ...

  14. MRI of the Chest

    Medline Plus

    Full Text Available ... as chest x-ray or CT. A special form of MRI called magnetic resonance angiography (MRA) is ... not to have an MRI exam during the first trimester unless medically necessary. MRI may not always ...

  15. MRI of the Chest

    Medline Plus

    Full Text Available ... or patients with claustrophobia. Other MRI machines are open on the sides (open MRI). Open units are especially helpful for examining larger patients or those with claustrophobia. Newer open MRI units provide very high quality images for ...

  16. MRI of the Chest

    Medline Plus

    Full Text Available ... the limitations of MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging (MRI) is a noninvasive ... top of page What are some common uses of the procedure? MR imaging of the chest is ...

  17. MRI of the Chest

    Medline Plus

    Full Text Available ... in the first three to four months of pregnancy unless the potential benefit from the MRI exam ... the MRI Safety page for more information about pregnancy and MRI. If you have claustrophobia (fear of ...

  18. MRI of the Chest

    Medline Plus

    Full Text Available ... MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging (MRI) is a noninvasive ... of page What are some common uses of the procedure? MR imaging of the chest is performed ...

  19. Glycosaminoglycan chemical exchange saturation transfer in human lumbar intervertebral discs: Effect of saturation pulse and relationship with low back pain.

    Science.gov (United States)

    Wada, Tatsuhiro; Togao, Osamu; Tokunaga, Chiaki; Funatsu, Ryohei; Yamashita, Yasuo; Kobayashi, Kouji; Nakamura, Yasuhiko; Honda, Hiroshi

    2017-03-01

    To evaluate the dependence of saturation pulse power and duration on glycosaminoglycan chemical exchange saturation transfer (gagCEST) imaging and assess the degeneration of human lumbar intervertebral discs (IVDs) using this method. All images were acquired on a 3T magnetic resonance imaging (MRI) scanner. The CEST effects were measured in the glycosaminoglycan (GAG) phantoms with different concentrations. In the human study, CEST effects were measured in the nucleus pulposus of IVD. We compared the CEST effects among the different saturation pulse powers (0.4, 0.8, and 1.6 μT) or durations (0.5, 1.0, and 2.0 sec) at each Pfirrmann grade (I-V). The relationship between the CEST effects and low back pain was also evaluated. The phantom study showed high correlations between the CEST effects and GAG concentration (R 2  = 0.863, P low back pain were significantly lower than those in the groups without pain (P pain (P = 0.0216). The contrast of gagCEST imaging in the lumbar IVDs varied with saturation pulse power and duration. GagCEST imaging may serve as a tool for evaluating IVD degeneration in the lumbar spine. 2 J. Magn. Reson. Imaging 2017;45:863-871. © 2016 International Society for Magnetic Resonance in Medicine.

  20. The activation of theory of mind network differentiates between point-to-self and point-to-other verbal jokes: an fMRI study.

    Science.gov (United States)

    Feng, Shengchuang; Ye, Xiang; Mao, Lihua; Yue, Xiaodong

    2014-04-03

    The mind-reading hypothesis of humor and the inner eye theory of laughter both claim that readers' mentalizing about characters in jokes is essential for perceiving humor. On the basis of this notion, we hypothesized that point-to-other verbal jokes (in which one character said funny things about the other character) induced more theory of mind (ToM) processing than point-to-self verbal jokes (in which one character said funny things about him/herself to the other character). Our hypothesis was tested by comparing percent signal changes of these two conditions in six core components of the ToM neural network. A whole-brain analysis was also conducted. Results from both the region of interest (ROI) analysis and the whole-brain analysis show that theory of mind network is more activated when subjects read point-to-other jokes than when they read point-to-self jokes. Moreover, the whole-brain results provide support for the viewpoint that the right hemisphere, especially the right frontal lobe, is important in ToM and humor processing. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. From QCD to nuclear matter saturation

    Energy Technology Data Exchange (ETDEWEB)

    Ericson, Magda [Universite de Lyon, Univ. Lyon 1, CNRS/IN2P3, IPN Lyon, F-69622 Villeurbanne Cedex (France)]|[Theory division, CERN, CH-12111 Geneva (Switzerland); Chanfray, Guy [Universite de Lyon, Univ. Lyon 1, CNRS/IN2P3, IPN Lyon, F-69622 Villeurbanne Cedex (France)

    2007-03-15

    We discuss a relativistic chiral theory of nuclear matter with {sigma} and {omega} exchange using a formulation of the {sigma} model in which all the chiral constraints are automatically fulfilled. We establish a relation between the nuclear response to the scalar field and the QCD one which includes the nucleonic parts. It allows a comparison between nuclear and QCD information. Going beyond the mean field approach we introduce the effects of the pion loops supplemented by the short-range interaction. The corresponding Landau-Migdal parameters are taken from spin-isospin physics results. The parameters linked to the scalar meson exchange are extracted from lattice QCD results. These inputs lead to a reasonable description of the saturation properties, illustrating the link between QCD and nuclear physics. We also derive from the corresponding equation of state the density dependence of the quark condensate and of the QCD susceptibilities. (authors)

  2. Animal MRI Core

    Data.gov (United States)

    Federal Laboratory Consortium — The Animal Magnetic Resonance Imaging (MRI) Core develops and optimizes MRI methods for cardiovascular imaging of mice and rats. The Core provides imaging expertise,...

  3. Saturation of the turbulent dynamo.

    Science.gov (United States)

    Schober, J; Schleicher, D R G; Federrath, C; Bovino, S; Klessen, R S

    2015-08-01

    The origin of strong magnetic fields in the Universe can be explained by amplifying weak seed fields via turbulent motions on small spatial scales and subsequently transporting the magnetic energy to larger scales. This process is known as the turbulent dynamo and depends on the properties of turbulence, i.e., on the hydrodynamical Reynolds number and the compressibility of the gas, and on the magnetic diffusivity. While we know the growth rate of the magnetic energy in the linear regime, the saturation level, i.e., the ratio of magnetic energy to turbulent kinetic energy that can be reached, is not known from analytical calculations. In this paper we present a scale-dependent saturation model based on an effective turbulent resistivity which is determined by the turnover time scale of turbulent eddies and the magnetic energy density. The magnetic resistivity increases compared to the Spitzer value and the effective scale on which the magnetic energy spectrum is at its maximum moves to larger spatial scales. This process ends when the peak reaches a characteristic wave number k☆ which is determined by the critical magnetic Reynolds number. The saturation level of the dynamo also depends on the type of turbulence and differs for the limits of large and small magnetic Prandtl numbers Pm. With our model we find saturation levels between 43.8% and 1.3% for Pm≫1 and between 2.43% and 0.135% for Pm≪1, where the higher values refer to incompressible turbulence and the lower ones to highly compressible turbulence.

  4. Magnetic Resonance Imaging (MRI) Safety

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) Safety What is MRI and how does it ... and MRI Breast-feeding and MRI What is MRI and how does it work? Magnetic resonance imaging, ...

  5. Magnetic Resonance Imaging (MRI) -- Head

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Head Magnetic resonance imaging (MRI) of the head ... limitations of MRI of the Head? What is MRI of the Head? Magnetic resonance imaging (MRI) is ...

  6. MRI of the Musculoskeletal System

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Musculoskeletal Magnetic resonance imaging (MRI) uses a powerful ... the limitations of a Musculoskeletal MRI? What is MRI of the Musculoskeletal System? Magnetic resonance imaging (MRI) ...

  7. Magnetic Resonance Imaging (MRI) - Spine

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Spine Magnetic resonance imaging (MRI) of the spine ... limitations of MRI of the Spine? What is MRI of the Spine? Magnetic resonance imaging (MRI) is ...

  8. Transition to Turbulent Dynamo Saturation

    Science.gov (United States)

    Seshasayanan, Kannabiran; Gallet, Basile; Alexakis, Alexandros

    2017-11-01

    While the saturated magnetic energy is independent of viscosity in dynamo experiments, it remains viscosity dependent in state-of-the-art 3D direct numerical simulations (DNS). Extrapolating such viscous scaling laws to realistic parameter values leads to an underestimation of the magnetic energy by several orders of magnitude. The origin of this discrepancy is that fully 3D DNS cannot reach low enough values of the magnetic Prandtl number Pm. To bypass this limitation and investigate dynamo saturation at very low Pm, we focus on the vicinity of the dynamo threshold in a rapidly rotating flow: the velocity field then depends on two spatial coordinates only, while the magnetic field consists of a single Fourier mode in the third direction. We perform numerical simulations of the resulting set of reduced equations for Pm down to 2 ×10-5. This parameter regime is currently out of reach to fully 3D DNS. We show that the magnetic energy transitions from a high-Pm viscous scaling regime to a low-Pm turbulent scaling regime, the latter being independent of viscosity. The transition to the turbulent saturation regime occurs at a low value of the magnetic Prandtl number, Pm ≃10-3 , which explains why it has been overlooked by numerical studies so far.

  9. SATURATED PICRIC ACID PREVENTS AUTOPHAGIA

    Directory of Open Access Journals (Sweden)

    V Rahimi-Movaghar

    2008-08-01

    Full Text Available "nThe dysesthesia and paresthesia that occurs in laboratory rats after spinal cord injury (SCI results in autophagia. This self-destructive behavior interferes with functional assessments in designed studies and jeopardizes the health of the injured rat. In this study, we evaluated role of saturated picric acid in the prevention of autophagia and self-mutilation. All rats were anesthetized with an intraperitoneal injection of a mixture of ketamine (100 mg/kg and xylazine (10 mg/kg for the SCI procedures. In the first 39 rats, no solution applied to the hind limbs, but in the next 26 cases, we smeared the saturated picric acid on the tail, lower extremities, pelvic, and abdomen of the rats immediately after SCI. In the rats without picric acid, 23 rats died following autophagia, but in the 26 rats with picric acid, there was no autophagia (P < 0.001. Picric acid side effects in skin and gastrointestinal signs such as irritation, redness and diarrhea were not seen in any rat. Saturated picric acid is a topical solution that if used appropriately and carefully, might be safe and effectively prevents autophagia and self-mutilation. When the solution is applied to the lower abdomen and limbs, we presume that its bitterness effectively prevents the rat from licking and biting the limb.

  10. Europium(III) Macrocyclic Complexes with Alcohol Pendant Groups as Chemical Exchange Saturation Transfer Agents

    Science.gov (United States)

    Woods, Mark; Woessner, Donald E.; Zhao, Piyu; Pasha, Azhar; Yang, Meng-Yin; Huang, Ching-Hui; Vasalitiy, Olga; Morrow, Janet R.; Sherry, A. Dean

    2009-01-01

    Paramagnetic lanthanide(III) complexes that contain hyperfine-shifted exchangeable protons offer considerable advantages over diamagnetic molecules as chemical exchange saturation transfer (CEST) agents for MRI. As part of a program to investigate avenues to improve the sensitivity of such agents, the CEST characteristics of europium(III) macrocyclic complexes having appended hydroxyethyl groups were investigated. The CEST spectrum of the asymmetrical complex, EuCNPHC3+, shows five distinct peaks for each magnetically nonequivalent exchangeable proton in the molecule. The CEST spectra of this complex were fitted to NMR Bloch theory to yield exchange rates between each of six exchanging proton pools (five on the agent plus bulk water). Exchange between the Eu3+-bound hydroxyl protons and bulk water protons was slow in dry acetonitrile but accelerated incrementally upon stepwise addition of water. In pure water, exchange was too fast to observe a CEST effect. The utility of this class of europium(III) complex for CEST imaging applications is ultimately limited by the small chemical shifts induced by the hydroxyl-appended ligands of this type and the resulting small Δω values for the exchangeable hydroxyl protons. PMID:16881645

  11. MRI of the Chest

    Medline Plus

    Full Text Available ... Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Chest Magnetic resonance imaging (MRI) of the chest uses a powerful ... Chest? What is MRI of the Chest? Magnetic resonance imaging (MRI) is a noninvasive medical test that ...

  12. Magnetic resonance imaging on CO(2) miscible and immiscible displacement in oil-saturated glass beads pack.

    Science.gov (United States)

    Liu, Yu; Zhao, Yuechao; Zhao, Jiafei; Song, Yongchen

    2011-10-01

    In this study, the displacement processes were observed as gaseous or supercritical CO(2) was injected into n-decane-saturated glass beads packs using a 400-MHz magnetic resonance imaging (MRI) system. Two-dimensional images of oil distribution in the vertical median section were obtained using a spin-echo pulse sequence. Gas channeling and viscous fingering appeared obviously in immiscible gaseous CO(2) displacement. A piston-like displacement front was detected in miscible supercritical CO(2) displacement that provided high sweep efficiency. MRI images were processed with image intensity analysis methods to obtain the saturation profiles. Final oil residual saturations and displacement coefficients were also estimated using this imaging intensity analysis. It was proved that miscible displacement can enhance the efficiency of CO(2) displacement notably. Finally, a special coreflood analysis method was applied to estimate the effects of capillary, viscosity and buoyancy based on the obtained saturation data. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. Promoter analysis by saturation mutagenesis

    Directory of Open Access Journals (Sweden)

    Baliga Nitin

    2001-01-01

    Full Text Available Gene expression and regulation are mediated by DNA sequences, in most instances, directly upstream to the coding sequences by recruiting transcription factors, regulators, and a RNA polymerase in a spatially defined fashion. Few nucleotides within a promoter make contact with the bound proteins. The minimal set of nucleotides that can recruit a protein factor is called a cis-acting element. This article addresses a powerful mutagenesis strategy that can be employed to define cis-acting elements at a molecular level. Technical details including primer design, saturation mutagenesis, construction of promoter libraries, phenotypic analysis, data analysis, and interpretation are discussed.

  14. Semiconductor saturable absorbers for ultrafast terahertz signals

    OpenAIRE

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductors GaAs, GaP, and Ge in the terahertz THz frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum states, due to conduction band onparabolicity and scattering into satellite valleys in strong THz fields. Saturable absorber parameters, such as linear and nonsaturable transmission, and saturation fluen...

  15. Semiconductor saturable absorbers for ultrafast terahertz signals

    OpenAIRE

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductorsGaAs,GaP, and Ge in the terahertz (THz) frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum states, due to conduction band nonparabolicity and scattering into satellite valleys in strong THz fields. Saturable absorber parameters, such as linear and nonsaturable transmission, and saturation flue...

  16. Temporo-parietal and fronto-parietal lobe contributions to theory of mind and executive control: an fMRI study of verbal jokes

    Science.gov (United States)

    Chan, Yu-Chen; Lavallee, Joseph P.

    2015-01-01

    ‘Getting a joke’ always requires resolving an apparent incongruity, but the particular cognitive operations called upon vary depending on the nature of the joke itself. Previous research has identified the primary neural correlates of the cognitive and affective processes called upon to respond to humor generally, but little work has been done on the substrates underlying the distinct cognitive operations required to comprehend particular joke types. This study explored the neural correlates of the cognitive processes required to successfully comprehend three joke types: bridging-inference jokes (BJs), exaggeration jokes (EJs), and ambiguity jokes (AJs). For all joke types, the left dlPFC appeared to support common cognitive mechanisms, such as script-shifting, while the vACC was associated with affective appreciation. The temporo-parietal lobe (TPJ and MTG) was associated with BJs, suggesting involvement of these regions with ‘theory of mind’ processing. The fronto-parietal lobe (IPL and IFG) was associated with both EJs and AJs, suggesting that it supports executive control processes such as retrieval from episodic memory, self-awareness, and language-based decoding. The social-affective appreciation of verbal jokes was associated with activity in the orbitofrontal cortex, amygdala, and parahippocampal gyrus. These results allow a more precise account of the neural processes required to support the particular cognitive operations required for the understanding of different types of humor. PMID:26388803

  17. Synthetic MRI for visualization of quantitative MRI

    OpenAIRE

    Peterson, Erika

    2013-01-01

    Magnetic resonance imaging (MRI) is an imaging technique that is used in hospitals worldwide. The images are acquired through the use of an MRI scanner and the clinical information is provided through the image contrast, which is based on the magnetic properties in biological tissue. By altering the scanner settings, images with different contrast properties can be obtained. Conventional MRI is a qualitative imaging technique and no absolute measurements are performed. At Center for Medical I...

  18. The use of saturation in qualitative research.

    Science.gov (United States)

    Walker, Janiece L

    2012-01-01

    Understanding qualitative research is an important component of cardiovascular nurses' practice and allows them to understand the experiences, stories, and perceptions of patients with cardiovascular conditions. In understanding qualitative research methods, it is essential that the cardiovascular nurse understands the process of saturation within qualitative methods. Saturation is a tool used for ensuring that adequate and quality data are collected to support the study. Saturation is frequently reported in qualitative research and may be the gold standard. However, the use of saturation within methods has varied. Hence, the purpose of this column is to provide insight for the cardiovascular nurse regarding the use of saturation by reviewing the recommendations for which qualitative research methods it is appropriate to use and how to know when saturation is achieved. In understanding saturation, the cardiovascular nurse can be a better consumer of qualitative research.

  19. Comparison of the effectiveness of saturation pulses in the heart at 3T.

    Science.gov (United States)

    Kim, Daniel; Gonen, Oded; Oesingmann, Niels; Axel, Leon

    2008-01-01

    Cardiac MRI at 3T provides a means to increase the contrast-to-noise ratio (CNR) for first-pass perfusion MRI. However, both the static magnetic field (B(0)) and radio frequency (RF) field (B(1)) variations within the heart are comparatively higher at 3T than at 1.5T. The increased field variations can degrade the performance of a single rectangular saturation pulse that is conventionally used for magnetization preparation. The accuracy of T(1)-weighted signal measurement depends on the uniformity of the magnetization saturation. The purpose of this study was to assess the relative effectiveness of the rectangular, pulse train, and adiabatic composite (BIR-4) saturation pulses in the human heart at 3T. In volunteers, after nominal saturation, the mean residual magnetization within the left ventricle (LV) was different between all three pulses (0.13 +/- 0.06 vs. 0.03 +/- 0.02 vs. 0.03 +/- 0.01, respectively; P < 0.001). Within paired groups, the mean residual magnetization was significantly higher for the rectangular pulse than for either the pulse train and BIR-4 pulses (P < 0.001), but not different between the pulse train and BIR-4 pulses. The performances of all three saturation pulses were comparatively poorer in the right ventricle (RV) than in the LV, respectively. 2007 Wiley-Liss, Inc

  20. Current MRI techniques for the assessment of renal disease.

    Science.gov (United States)

    Takahashi, Takamune; Wang, Feng; Quarles, Christopher C

    2015-05-01

    Over the past decade, a variety of MRI methods have been developed and applied to many kidney diseases. These MRI techniques show great promise, enabling the noninvasive assessment of renal structure, function and injury in individuals. This review will highlight the current applications of functional MRI techniques for the assessment of renal disease and discuss future directions. Many pathological (functional and structural) changes or factors in renal disease can be assessed by advanced MRI techniques. These include renal vascular structure and function (contrast-enhanced MRI, arterial spin labelling), tissue oxygenation (blood oxygen level dependent MRI), renal tissue injury and fibrosis (diffusion or magnetization transfer imaging, magnetic resonance elastography), renal metabolism (chemical exchange saturation transfer, spectroscopic imaging), nephron endowment (cationic-contrast imaging), sodium concentration (23Na-MRI) and molecular events (targeted-contrast imaging). Current advances in MRI techniques have enabled the noninvasive investigation of renal disease. Further development, evaluation and application of the MRI techniques should facilitate better understanding and assessment of renal disease, and the development of new imaging biomarkers, enabling the intensified treatment of high-risk populations and a more rapid interrogation of novel therapeutic agents and protocols.

  1. Neurovascular uncoupling under mild hypoxic hypoxia: an EEG–fMRI study in rats

    Science.gov (United States)

    Sumiyoshi, Akira; Suzuki, Hideaki; Shimokawa, Hiroaki; Kawashima, Ryuta

    2012-01-01

    The effects of oxygen availability on neurovascular coupling were investigated using simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), in addition to the monitoring of physiological parameters, in 16 α-chloralose-anesthetized rats. Mild hypoxic hypoxia (oxygen saturation=83.6±12.1%) induced significant reductions in fMRI responses (PEEG responses remained unchanged. In addition, the changes in oxygen saturation were linearly correlated with the changes in the fMRI responses. These data further emphasize the importance of oxygen availability, which may regulate neurovascular coupling via the oxygen-dependent enzymatic synthesis of messenger molecules. PMID:22828997

  2. Canalis basilaris medianus: MRI

    Energy Technology Data Exchange (ETDEWEB)

    Jacquemin, C. [Dept. of Radiology, King Khaled Eye Specialist Hospital, Riyadh (Saudi Arabia); Bosley, T.M.; Al Saleh, M. [Div. of Neuro-ophthalmology, King Khaled Eye Specialist Hospital, Riyadh (Saudi Arabia); Mullaney, P. [Division of Pediatrics, King Khaled Eye Specialist Hospital, Riyadh (Saudi Arabia)

    2000-02-01

    We report the MRI appearances of an developmental anatomical variant of the basiocciput, with neuroimaging findings (CT and MRI). Such variants are commonly asymptomatic, but may be associated with episodes of meningitis. (orig.)

  3. MRI of the Chest

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Chest Magnetic resonance imaging (MRI) of the chest uses a powerful magnetic field, radio waves and a computer to produce ...

  4. Abdominal MRI scan

    Science.gov (United States)

    Nuclear magnetic resonance - abdomen; NMR - abdomen; Magnetic resonance imaging - abdomen; MRI of the abdomen ... radiologist see certain areas more clearly. During the MRI, the person who operates the machine will watch ...

  5. MRI of the Chest

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... may not fit into the opening of certain types of MRI machines. The presence of an implant ...

  6. MRI of the Chest

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    Full Text Available ... treatment. See the MRI Safety page for more information about pregnancy and MRI. If you have claustrophobia (fear of enclosed spaces) or anxiety, you may want to ask your physician for ...

  7. MRI of the Chest

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    Full Text Available ... a very small chance of irritation of your skin at the site of the IV tube insertion. ... detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has proven ...

  8. MRI of the Chest

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    Full Text Available ... to a CD or uploaded to a digital cloud server. MRI of the chest gives detailed pictures ... as chest x-ray or CT. A special form of MRI called magnetic resonance angiography (MRA) is ...

  9. MRI of the Chest

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    Full Text Available ... MRI scan. Because they can interfere with the magnetic field of the MRI unit, metal and electronic items ... and braces usually are not affected by the magnetic field, but they may distort images of the facial ...

  10. MRI of the Chest

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    Full Text Available ... eyes or other reactions. If you experience allergic symptoms, notify the technologist. A radiologist or other physician ... detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has proven ...

  11. MRI of the Chest

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    Full Text Available ... interfere with the magnetic field of the MRI unit, metal and electronic items are not allowed in ... does the equipment look like? The traditional MRI unit is a large cylinder-shaped tube surrounded by ...

  12. MRI of the Chest

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    Full Text Available ... top of page What are the benefits vs. risks? Benefits MRI is a noninvasive imaging technique that ... risking the side effects of conventional (catheter) angiography . Risks The MRI examination poses almost no risk to ...

  13. MRI of the Chest

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    Full Text Available ... detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has proven ... the technologist or nurse will monitor your vital signs to minimize this risk. Although the strong magnetic ...

  14. MRI of the Chest

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    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam is safe for patients with metal implants, except for a few types. ...

  15. MRI of the Chest

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    Full Text Available ... other internal body structures. MRI does not use ionizing radiation (x-rays). Detailed MR images allow physicians ... computed tomography (CT) scans, MRI does not utilize ionizing radiation. Instead, radiofrequency pulses re-align hydrogen atoms ...

  16. MRI of the Chest

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    Full Text Available ... are the limitations of MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging ( ... heart, valves, great vessels, etc.). top of page What are some common uses of the procedure? MR ...

  17. MRI of the Chest

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    Full Text Available ... examination poses almost no risk to the average patient when appropriate safety guidelines are followed. If sedation is used, there ... patient story here Images × ... Resonance Imaging (MRI) Safety MRI Safety During Pregnancy Images related to Magnetic ...

  18. MRI of the Chest

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    Full Text Available ... women should not have this exam in the first three to four months of pregnancy unless the ... not to have an MRI exam during the first trimester unless medically necessary. MRI may not always ...

  19. MRI of the Chest

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    Full Text Available ... is done because a potential abnormality needs further evaluation with additional views or a special imaging technique. ... MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has proven valuable in ...

  20. MRI of the Chest

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    Full Text Available ... clearer and more detailed than with other imaging methods. This detail makes MRI an invaluable tool in ... might be obscured by bone with other imaging methods. The contrast material used in MRI exams is ...

  1. MRI of the Chest

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    Full Text Available ... devices require a short period of time after placement (usually six weeks) before being safe for MRI ... devices that contain metal may malfunction or cause problems during an MRI exam. Nephrogenic systemic fibrosis is ...

  2. MRI of the Chest

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    Full Text Available ... or headphones during the exam. MRI scanners are air-conditioned and well-lit. Music may be played ... the limitations of MRI of the Chest? High-quality images are assured only if you are able ...

  3. MRI of the Chest

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    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will ... MRI. For more information, consult your radiologist. The computer workstation that processes the imaging information is located ...

  4. MRI of the Chest

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    Full Text Available ... internal body structures. MRI does not use ionizing radiation (x-rays). Detailed MR images allow physicians to ... tomography (CT) scans, MRI does not utilize ionizing radiation. Instead, radiofrequency pulses re-align hydrogen atoms that ...

  5. MRI of the Chest

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    Full Text Available ... conditions. MRI uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures ... does not completely surround you. Some newer MRI machines have a larger diameter bore which can be ...

  6. MRI of the Chest

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    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will ... information on the chemicals present in the body's cells, may also be performed during the MRI exam ...

  7. fMRI Neuroinformatics

    DEFF Research Database (Denmark)

    Nielsen, Finn Årup; Christensen, Mark Schram; Madsen, Kristoffer M.

    2006-01-01

    Functional magnetic resonance imaging (fMRI) generates vast amounts of data. The handling, processing, and analysis of fMRI data would be inconceivable without computer-based methods. fMRI neuroinformatics is concerned with research, development, and operation of these methods. Reconstruction...

  8. MRI of the Chest

    Medline Plus

    Full Text Available ... or CT. A special form of MRI called magnetic resonance angiography (MRA) is helpful to assess the vessels of ... child-specific content. Related Articles and Media MR Angiography (MRA) Magnetic Resonance Imaging (MRI) Safety MRI Safety During Pregnancy Images ...

  9. MRI of Cerebellar Infarction

    NARCIS (Netherlands)

    De Cocker, Laurens J L; Lövblad, Karl-Olof; Hendrikse, Jeroen

    2017-01-01

    BACKGROUND: MRI is the imaging modality of choice for diagnosing brain infarction. Because of few or atypical clinical symptoms and a relatively low sensitivity of CT scans, many cerebellar infarctions may be detected only with MRI. With adequate recognition of cerebellar infarction on MRI and

  10. MRI of the Chest

    Medline Plus

    Full Text Available ... MRI exam is assumed to outweigh the potential risks. Pregnant women should not receive injections of gadolinium contrast material except when absolutely necessary for medical treatment. See the MRI Safety page for more information about pregnancy and MRI. If you have claustrophobia ( ...

  11. MRI of the Chest

    Medline Plus

    Full Text Available ... are the limitations of MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging (MRI) is a noninvasive ... heart, valves, great vessels, etc.). top of page What are some common uses of the procedure? MR ...

  12. MRI in acute poliomyelitis

    Energy Technology Data Exchange (ETDEWEB)

    Kornreich, L. [Imaging Department, The Schneider Children`s Medical Centre of Israel, Kaplan Street, Petah Tiqva 49202 (Israel)]|[Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (Israel); Dagan, O. [The Intensive Care Unit, The Schneider Children`s Medical Centre of Israel, Beilinson Medical Campus, Petah Tiqva (Israel)]|[Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (Israel); Grunebaum, M. [Imaging Department, The Schneider Children`s Medical Centre of Israel, Kaplan Street, Petah Tiqva 49202 (Israel)]|[Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (Israel)

    1996-05-01

    MRI can be used in the diagnosis of anterior horn infection and for assessing the extent of disease. There are no specific MRI signs to differentiate between the various possible pathogens. This is demonstrated in the present case of poliomyelitis, in which MRI of the spine played an important role in establishing the diagnosis. (orig.). With 1 fig.

  13. MRI of the Chest

    Medline Plus

    Full Text Available ... tumors. MRI can help physicians evaluate both the structure of an organ and how it is working. MRI enables the discovery of abnormalities that might be obscured by bone with other imaging methods. The contrast material used in MRI exams is less likely to ...

  14. Power flow control using distributed saturable reactors

    Science.gov (United States)

    Dimitrovski, Aleksandar D.

    2016-02-13

    A magnetic amplifier includes a saturable core having a plurality of legs. Control windings wound around separate legs are spaced apart from each other and connected in series in an anti-symmetric relation. The control windings are configured in such a way that a biasing magnetic flux arising from a control current flowing through one of the plurality of control windings is substantially equal to the biasing magnetic flux flowing into a second of the plurality of control windings. The flow of the control current through each of the plurality of control windings changes the reactance of the saturable core reactor by driving those portions of the saturable core that convey the biasing magnetic flux in the saturable core into saturation. The phasing of the control winding limits a voltage induced in the plurality of control windings caused by a magnetic flux passing around a portion of the saturable core.

  15. Saturated versus unsaturated hydrocarbon interactions with carbon nanostructures

    Directory of Open Access Journals (Sweden)

    Deivasigamani eUmadevi

    2014-09-01

    Full Text Available The interactions of various acyclic and cyclic hydrocarbons in both saturated and unsaturated forms with the carbon nanostructures (CNSs have been explored by using density functional theory (DFT calculations. Model systems representing armchair and zigzag carbon nanotubes (CNTs and graphene have been considered to investigate the effect of chirality and curvature of the CNSs towards these interactions. Results of this study reveal contrasting binding nature of the acyclic and cyclic hydrocarbons towards CNSs. While the saturated molecules show stronger binding affinity in acyclic hydrocarbons; the unsaturated molecules exhibit higher binding affinity in cyclic hydrocarbons. In addition, acyclic hydrocarbons exhibit stronger binding affinity towards the CNSs when compared to their corresponding cyclic counterparts. The computed results excellently corroborate the experimental observations. The interaction of hydrocarbons with graphene is more favourable when compared with CNTs. Bader’s theory of atoms in molecules has been invoked to characterize the noncovalent interactions of saturated and unsaturated hydrocarbons. Our results are expected to provide useful insights towards the development of rational strategies for designing complexes with desired noncovalent interaction involving CNSs.

  16. Cognitive zonal fusion biopsy of the prostate: Original technique between target and saturation

    Directory of Open Access Journals (Sweden)

    Andrea B. Galosi

    2016-12-01

    Full Text Available We describe our experience in prostate biopsy using a new standardized cognitive fusion techniques, that we call “cognitive zonal fusion biopsy”. This new technique is based on two operative options: the first based on target biopsies, the Cognitive Target Biopsy (CTB if the same target was detected with transrectal ultrasound (TRUS and multiparametric magnetic resonance (mpMRI; the second based on saturation biopsies, the Zonal Saturation Biopsy (ZSB on anatomical zone/s containing the region of interest if the same target was not evident with TRUS and MRI. We evaluated results of our technique compared to standard biopsy in order to identify clinically relevant prostate cancer. Methods: This is a single-center prospective study conducted in 58 pts: 25 biopsy-naïve, 25 with previous negative biopsy and in 8 with cancer in active surveillance. Based on mpMRI and transrectal ultrasonography (TRUS, all patients were scheduled for standard 12-core TRUS-guided biopsy. If mpMRI was suggestive or positive (PI-RADS 3, 4 or 5: patients underwent additional targeted 2 to 6 cores using cognitive zonal fusion technique. Results: 31/58 (53.4% patients had a cancer. Our technique detected 80.6% (25 of 31 with clinically significant prostate cancer, leading to detection of insignificant cancer in 20%. Using standard mapping in MR negative areas we found 5 clinically significant cancer and 4 not significant cancers. MRI cancer detection rate was 18/31 (58.1%, and 9/18 (50% in high grade tumors. Therefore MRI missed 50% of high grade cancers. The mean number of cores taken with cognitive zonal fusion biopsy was 6.1 (2-17, in addition biopsy sampling was done outside the ROI areas. Overall 15.4 cores (12-22 were taken. Cancer amount in Zonal Biopsy was larger than 7.3 mm (1-54.5 in comparison with 5.2 mm (1-23.5 in standard mapping. Largest percentage of cancer involvement with cognitive zonal fusion technique was detected in 19.4% vs 15.9%. Conclusions

  17. Using X-ray computed tomography to evaluate the initial saturation resulting from different saturation procedures

    DEFF Research Database (Denmark)

    Christensen, Britt Stenhøj Baun; Wildenschild, D; Jensen, K.H.

    2006-01-01

    for saturation. Evaluation of the different enhanced saturation techniques was done with Xray computed tomography (CT) and gravimetrically. The use of CT scanning makes it possible to observe the spatial distribution of wetting and non-wetting phases in the porous medium in a non-destructive way. In this case...... with pressurized nitrogen between each saturation and allowed to saturate for the same length of time for all the different procedures. Both gravimetric measurements and CT attenuation levels showed that venting the sample with carbon dioxide prior to saturation clearly improved initial saturation whereas the use...

  18. [MRI enterography in the assessment of paediatric Crohn's disease].

    Science.gov (United States)

    Alvarez Beltran, M; Barber Martinez de la Torre, I; Segarra Cantón, O; Redecillas Ferreiro, S; Castellote Alonso, A; Infante Pina, D

    2013-05-01

    To determine the usefulness of MRI enterography for assessing the extension and activity of paediatric Crohn's disease. MRI findings were compared with clinical, biological, endoscopic and other imaging data. Studies of MRI enterography use in patients younger than 18 years of age were reviewed. Patients received 500-1000mL of polyethylene glycol one hour before examination (1.5-TMR). T2 HASTE sequences with or without fat saturation, T2 true-FISP, T1 with fat saturation, pre- and post gadolinium-enhanced VIBE sequences, and dynamic and diffusion HASTE were acquired. Thickening of the bowel wall, mucosal enhancement, and extra-luminal complications were evaluated. Five MRI patterns (normal, fibrosis, mild, moderate, and severe transmural activity) were defined. Findings were compared with PCDAI scores, inflammatory parameters, and endoscopic and histological results. Twenty-two studies were reviewed. Optimal intestinal distension was present in 82% of the cases. Mild side effects were observed in 12% of patients. There was a significant relationship between MRI patterns and PCDAI scores (P=.002), sedimentation rate (P=.006) and serum PCR levels (P=.047) and a non-significant relationship with the histology (P=.571). MRI enterography correctly assessed the ileal (80%) and colonic (66%) extension. Extra-luminal complications unrelated to MRI classification (P=.274) were reported in 86.4% of studies. There was a significant relationship between MRI patterns and PCR, sedimentation rate, and PCDAI scores. MRI enterography showed excellent agreement with ileoscopies, and allowed endoscopically non-accessible areas to be assessed, as well as the diagnosis of extra-luminal complications without irradiation. Copyright © 2012 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.

  19. MRI features of epidural extramedullary hematopoiesis

    Energy Technology Data Exchange (ETDEWEB)

    Alorainy, Ibrahim A. E-mail: alorainy@ksu.edu.sa; Al-Asmi, Abdullah R.; Carpio, Raquel del

    2000-07-01

    A case of {beta}-thalassemia intermedia with spinal cord compression due to extramedullary hematopoiesis, which was successfully treated by blood transfusion, is presented. Emphasis was made on the MRI appearance of extramedullary hematopoiesis on different pulse sequences. The theories that aimed to explain the involvement of the epidural space by extramedullary hematopoiesis are discussed.

  20. Avalanche effect and gain saturation in high harmonic generation

    CERN Document Server

    Serrat, Carles; Budesca, Josep M; Seres, Jozsef; Seres, Enikoe; Aurand, Bastian; Hoffmann, Andreas; Namba, Shinichi; Kuehl, Thomas; Spielmann, Christian

    2015-01-01

    Optical amplifiers in all ranges of the electromagnetic spectrum exhibit two essential characteristics: i) the input signal during the propagation in the medium is multiplied by the avalanche effect of the stimulated emission to produce exponential growth and ii) the amplification saturates at increasing input signal. We demonstrate that the strong-field theory in the frame of high harmonic generation fully supports the appearance of both the avalanche and saturation effects in the amplification of extreme ultraviolet attosecond pulse trains. We confirm that the amplification takes place only if the seed pulses are perfectly synchronized with the driving strong field in the amplifier. We performed an experimental study and subsequent model calculation on He gas driven by intense 30-fs-long laser pulses, which was seeded with an attosecond pulse train at 110 eV generated in a separated Ne gas jet. The comparison of the performed calculations with the measurements clearly demonstrates that the pumped He gas med...

  1. Structure in the nonlinear saturation spectrum of parametric instabilities.

    Science.gov (United States)

    Fejer, J. A.; Kuo, Y.-Y.

    1973-01-01

    The nonlinear saturation spectrum of the decay instability is obtained in the limit of small spontaneous emission, for comparable ion and electron temperatures, from numerical solutions of a kinetic equation based on an accurate expression for the nonlinearity. The spectral energy occupies several pairs of isolated saucer-shaped regions in wave-vector space. The regions increase in thickness, angular diameter, and number as the pump power is increased. The theory thus predicts the generation of waves propagating in directions which can differ substantially from the direction of the pump field. Ionospheric observations confirm this prediction; they were difficult to reconcile with the predictions of previous theories based on an approximated expression for the nonlinearity. The present work also corrects the results of previous one-dimensional theories that used an accurate expression for the nonlinearity and predicted 'spectral lines' in the limit of vanishing spontaneous emission.

  2. Synthesis and characterization of saturated polyester and ...

    Indian Academy of Sciences (India)

    and nanocomposites derived from glycolyzed PET waste with varied compositions. SUNAIN KATOCH. ∗ ... Water vapour transmission (WVT) was determined for saturated polyester nanocomposite sheets according to ... ing the synthesis of saturated polyester (from GPET waste). This has been done for the estimation of the ...

  3. Ultrafast THz Saturable Absorption in Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hoffmann, Matthias C.

    2011-01-01

    We demonstrate THz saturable absorption in n-doped semiconductors GaAs, GaP, and Ge in a nonlinear THz time-domain spectroscopy experiment. Saturable absorption is caused by sample conductivity modulation due to electron heating and satellite valley scattering in the field of a strong THz pulse....

  4. Fault tolerant control of systems with saturations

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik

    2013-01-01

    This paper presents framework for fault tolerant controllers (FTC) that includes input saturation. The controller architecture known from FTC is based on the Youla-Jabr-Bongiorno-Kucera (YJBK) parameterization is extended to handle input saturation. Applying this controller architecture in connec...

  5. Semiconductor saturable absorbers for ultrafast terahertz signals

    DEFF Research Database (Denmark)

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    2010-01-01

    We demonstrate saturable absorber behavior of n-type semiconductors GaAs, GaP, and Ge in the terahertz THz frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum...

  6. Strength and Biot's coefficient for high-porosity oil- or water-saturated chalk

    DEFF Research Database (Denmark)

    Andreassen, Katrine Alling

    considerations for the size of the drilling window and the magnitude of the lateral stress involve the Biot coefficient. Additionally, the fluid effect of oil-saturated chalk behaving much stronger than water-saturated chalk affects geomechanical considerations related to e.g. water injection into a reservoir...... during hydrostatic loading. The hypothesis is that the Biot coefficient and the theory of poroelasticity may cover the fluid effect by including the increased fluid bulk modulus from oil to water. A high number of test results for both oil- and water-saturated high-porosity outcrop chalk show correlation...

  7. Determination of saturation functions and wettability for chalk based on measured fluid saturations

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, D.; Bech, N.; Moeller Nielsen, C.

    1998-08-01

    The end effect of displacement experiments on low permeable porous media is used for determination of relative permeability functions and capillary pressure functions. Saturation functions for a drainage process are determined from a primary drainage experiment. A reversal of the flooding direction creates an intrinsic imbibition process in the sample, which enables determination if imbibition saturation functions. The saturation functions are determined by a parameter estimation technique. Scanning effects are modelled by the method of Killough. Saturation profiles are determined by NMR. (au)

  8. Biomolecular MRI reporters: Evolution of new mechanisms.

    Science.gov (United States)

    Mukherjee, Arnab; Davis, Hunter C; Ramesh, Pradeep; Lu, George J; Shapiro, Mikhail G

    2017-11-01

    Magnetic resonance imaging (MRI) is a powerful technique for observing the function of specific cells and molecules inside living organisms. However, compared to optical microscopy, in which fluorescent protein reporters are available to visualize hundreds of cellular functions ranging from gene expression and chemical signaling to biomechanics, to date relatively few such reporters are available for MRI. Efforts to develop MRI-detectable biomolecules have mainly focused on proteins transporting paramagnetic metals for T1 and T2 relaxation enhancement or containing large numbers of exchangeable protons for chemical exchange saturation transfer. While these pioneering developments established several key uses of biomolecular MRI, such as imaging of gene expression and functional biosensing, they also revealed that low molecular sensitivity poses a major challenge for broader adoption in biology and medicine. Recently, new classes of biomolecular reporters have been developed based on alternative contrast mechanisms, including enhancement of spin diffusivity, interactions with hyperpolarized nuclei, and modulation of blood flow. These novel reporters promise to improve sensitivity and enable new forms of multiplexed and functional imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Postinterventional MRI findings following MRI-guided laser ablation of osteoid osteoma

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, S., E-mail: simon.fuchs@charite.de [Department of Radiology, Charité, Humboldt University, Berlin (Germany); Gebauer, B.; Stelter, L.; Schäfer, M.L.; Renz, D.M. [Department of Radiology, Charité, Humboldt University, Berlin (Germany); Melcher, I.; Schaser, K. [Center for Musculoskeletal Surgery, Charité, Humboldt University, Berlin (Germany); Hamm, B.; Streitparth, F. [Department of Radiology, Charité, Humboldt University, Berlin (Germany)

    2014-04-15

    Objective: To evaluate postinterventional magnetic resonance imaging (MRI) characteristics following MRI-guided laser ablation of osteoid osteoma (OO). Materials and methods: 35 patients treated with MRI-guided laser ablation underwent follow-up MRI immediately after the procedure, after 3, 6, 12, 24, 36, and up to 48 months. The imaging protocol included multiplanar fat-saturated T2w TSE, unenhanced and contrast-enhanced T1w SE, and subtraction images. MR images were reviewed regarding the appearance and size of treated areas, and presence of periablation bone and soft tissue changes. Imaging was correlated with clinical status. Results: Mean follow-up time was 13.6 months. 28/35 patients (80%) showed a postinterventional “target-sign” appearance consisting of a fibrovascular rim zone and a necrotic core area. After an initial increase in total lesion diameter after 3 months, a subsequent progressive inward remodeling process of the zonal compartments was observed for up to 24 months. Periablation bone and soft tissue changes showed a constant decrease over time. MR findings correlated well with the clinical status. Clinical success was achieved in 32/35 (91%). Conclusions: Evaluation of long-term follow-up MRI after laser ablation of OO identified typical postinterventional changes and thus may contribute to the interpretation of therapeutic success and residual or recurrent OO in suspected cases.

  10. MRI in psychiatry

    Energy Technology Data Exchange (ETDEWEB)

    Mulert, Christoph [UKE, Hamburg (Germany). Psychiatry Neuroimaging Branch; Shenton, Martha E. (ed.) [Harvard Medical School, Boston, MA (United States). Dept. of Psychiatry and Radiology

    2014-07-01

    This is the first comprehensive textbook on the use of MRI in psychiatry covering imaging techniques, brain systems and a review of findings in different psychiatric disorders. The book is divided into three sections, the first of which covers in detail all the major MRI-based methodological approaches available today, including fMRI, EEG-fMRI, DTI, and MR spectroscopy. In addition, the role of MRI in imaging genetics and combined brain stimulation and imaging is carefully explained. The second section provides an overview of the different brain systems that are relevant for psychiatric disorders, including the systems for perception, emotion, cognition, and reward. The final part of the book presents the MRI findings that are obtained in all the major psychiatric disorders using the previously discussed techniques. Numerous carefully chosen images support the informative text, making this an ideal reference work for all practitioners and trainees with an interest in this flourishing field.

  11. Transformer ratio saturation in a beam-driven wakefield accelerator

    Science.gov (United States)

    Farmer, J. P.; Martorelli, R.; Pukhov, A.

    2015-12-01

    We show that for beam-driven wakefield acceleration, the linearly ramped, equally spaced train of bunches typically considered to optimise the transformer ratio only works for flat-top bunches. Through theory and simulation, we explain that this behaviour is due to the unique properties of the plasma response to a flat-top density profile. Calculations of the optimal scaling for a train of Gaussian bunches show diminishing returns with increasing bunch number, tending towards saturation. For a periodic bunch train, a transformer ratio of 23 was achieved for 50 bunches, rising to 40 for a fully optimised beam.

  12. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Head Magnetic resonance imaging (MRI) of the head ... limitations of MRI of the Head? What is MRI of the Head? Magnetic resonance imaging (MRI) is ...

  13. Turbulence Closure for Mixing Length Theories

    Science.gov (United States)

    Jermyn, Adam S.; Lesaffre, Pierre; Tout, Christopher A.; Chitre, Shashikumar M.

    2018-01-01

    We present an approach to turbulence closure based on mixing length theory with three-dimensional fluctuations against a two-dimensional background. This model is intended to be rapidly computable for implementation in stellar evolution software and to capture a wide range of relevant phenomena with just a single free parameter, namely the mixing length. We incorporate magnetic, rotational, baroclinic and buoyancy effects exactly within the formalism of linear growth theories with nonlinear decay. We treat differential rotation effects perturbatively in the corotating frame using a novel controlled approximation which matches the time evolution of the reference frame to arbitrary order. We then implement this model in an efficient open source code and discuss the resulting turbulent stresses and transport coefficients. We demonstrate that this model exhibits convective, baroclinic and shear instabilities as well as the magnetorotational instability (MRI). It also exhibits non-linear saturation behaviour, and we use this to extract the asymptotic scaling of various transport coefficients in physically interesting limits.

  14. Combinatorics of saturated secondary structures of RNA.

    Science.gov (United States)

    Clote, P

    2006-11-01

    Following Zuker (1986), a saturated secondary structure for a given RNA sequence is a secondary structure such that no base pair can be added without violating the definition of secondary structure, e.g., without introducing a pseudoknot. In the Nussinov-Jacobson energy model (Nussinov and Jacobson, 1980), where the energy of a secondary structure is -1 times the number of base pairs, saturated secondary structures are local minima in the energy landscape, hence form kinetic traps during the folding process. Here we present recurrence relations and closed form asymptotic limits for combinatorial problems related to the number of saturated secondary structures. In addition, Python source code to compute the number of saturated secondary structures having k base pairs can be found at the web servers link of bioinformatics.bc.edu/clotelab/.

  15. Saturated fat, carbohydrate, and cardiovascular disease

    National Research Council Canada - National Science Library

    Siri-Tarino, Patty W; Sun, Qi; Hu, Frank B; Krauss, Ronald M

    2010-01-01

    A focus of dietary recommendations for cardiovascular disease (CVD) prevention and treatment has been a reduction in saturated fat intake, primarily as a means of lowering LDL-cholesterol concentrations...

  16. Saturated thickness, High Plains aquifer, 2009

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This raster data set represents the saturated thickness of the High Plains aquifer of the United States, 2009, in feet. The High Plains aquifer underlies...

  17. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... about pregnancy and MRI. If you have claustrophobia (fear of enclosed spaces) or anxiety, you may want ... medically necessary. MRI may not always distinguish between cancer tissue and fluid, known as edema . MRI typically ...

  18. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... or patients with claustrophobia. Other MRI machines are open on the sides (open MRI). Open units are especially helpful for examining larger patients or those with claustrophobia. Newer open MRI units provide very high quality images for ...

  19. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... the limitations of MRI of the Head? What is MRI of the Head? Magnetic resonance imaging (MRI) is a noninvasive ... top of page What are some common uses of the procedure? MR imaging of the head is ...

  20. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... in the first three to four months of pregnancy unless the potential benefit from the MRI exam ... the MRI Safety page for more information about pregnancy and MRI. If you have claustrophobia (fear of ...

  1. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... MRI of the Head? What is MRI of the Head? Magnetic resonance imaging (MRI) is a noninvasive ... of page What are some common uses of the procedure? MR imaging of the head is performed ...

  2. Semiconductor saturable absorbers for ultrafast THz signals

    DEFF Research Database (Denmark)

    Hoffmann, Matthias C.; Turchinovich, Dmitry

    We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths.......We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths....

  3. Phase field modeling of partially saturated deformable porous media

    Science.gov (United States)

    Sciarra, Giulio

    2016-09-01

    A poromechanical model of partially saturated deformable porous media is proposed based on a phase field approach at modeling the behavior of the mixture of liquid water and wet air, which saturates the pore space, the phase field being the saturation (ratio). While the standard retention curve is expected still^ to provide the intrinsic retention properties of the porous skeleton, depending on the porous texture, an enhanced description of surface tension between the wetting (liquid water) and the non-wetting (wet air) fluid, occupying the pore space, is stated considering a regularization of the phase field model based on an additional contribution to the overall free energy depending on the saturation gradient. The aim is to provide a more refined description of surface tension interactions. An enhanced constitutive relation for the capillary pressure is established together with a suitable generalization of Darcy's law, in which the gradient of the capillary pressure is replaced by the gradient of the so-called generalized chemical potential, which also accounts for the "force", associated to the local free energy of the phase field model. A micro-scale heuristic interpretation of the novel constitutive law of capillary pressure is proposed, in order to compare the envisaged model with that one endowed with the concept of average interfacial area. The considered poromechanical model is formulated within the framework of strain gradient theory in order to account for possible effects, at laboratory scale, of the micro-scale hydro-mechanical couplings between highly localized flows (fingering) and localized deformations of the skeleton (fracturing).

  4. The effect of fluid saturation on the dynamic shear modulus of tight sandstones

    Science.gov (United States)

    Li, Dongqing; Wei, Jianxin; Di, Bangrang; Ding, Pinbo; Shuai, Da

    2017-10-01

    Tight sandstones have become important targets in the exploration of unconventional oil and gas reservoirs. However, due to low porosity, low permeability, complex pore structure and other petrophysical properties of tight sandstones, the applicability of Gassmann’s fluid substitution procedure becomes debatable. Aiming at this problem, this paper attempts to explore the applicability of Gassmann’s theory in tight sandstones. Our focus is to investigate the sensitivity of dynamic shear modulus to fluid saturation and the possible mechanism. Ultrasonic velocity in dry and saturated tight sandstone samples was measured in the laboratory under an effective pressure within the range of 1-60 MPa. This study shows that the shear modulus of the water-saturated samples appears to either increase or decrease, and the soft porosity model (SPM) can be used to quantitatively estimate the variation of shear modulus. Under the condition of in situ pressure, samples dominated by secondary pores and microcracks are prone to show shear strengthening with saturation, which is possibly attributed to the local flow dispersion. Samples that mainly have primary pores are more likely to show shear weakening with saturation, which can be explained by the surface energy mechanism. We also find good correlation between changes in shear modulus and inaccurate Gassmann-predicted saturated velocity. Therefore, understanding the variation of shear modulus is helpful to improving the applicability of Gassmann’s theory in tight sandstones.

  5. Advance MRI for pediatric brain tumors with emphasis on clinical benefits

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Hyun Woo; Ra, Young Shin [Asan Medical Center, University of Ulsan College of Medicine, Seoul(Korea, Republic of)

    2017-01-15

    Conventional anatomic brain MRI is often limited in evaluating pediatric brain tumors, the most common solid tumors and a leading cause of death in children. Advanced brain MRI techniques have great potential to improve diagnostic performance in children with brain tumors and overcome diagnostic pitfalls resulting from diverse tumor pathologies as well as nonspecific or overlapped imaging findings. Advanced MRI techniques used for evaluating pediatric brain tumors include diffusion-weighted imaging, diffusion tensor imaging, functional MRI, perfusion imaging, spectroscopy, susceptibility-weighted imaging, and chemical exchange saturation transfer imaging. Because pediatric brain tumors differ from adult counterparts in various aspects, MRI protocols should be designed to achieve maximal clinical benefits in pediatric brain tumors. In this study, we review advanced MRI techniques and interpretation algorithms for pediatric brain tumors.

  6. MRI of the Chest

    Medline Plus

    Full Text Available Toggle navigation Test/Treatment Patient Type Screening/Wellness Disease/Condition Safety En Español More Info Images/Videos About Us News Physician ... Magnetic resonance imaging (MRI) is a noninvasive medical test that physicians use to diagnose medical conditions. MRI ...

  7. MRI of the Chest

    Medline Plus

    Full Text Available ... detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has proven ... in diagnosing a broad range of conditions, including cancer, heart and ... tissues, except for lung abnormalities where Chest CT is a preferred imaging ...

  8. MRI of the Chest

    Medline Plus

    Full Text Available ... pediatric facilities have child life personnel who can work with younger children to help avoid the need for sedation or anesthesia. They prepare the children for MRI by showing them a dummy scanner, play the noises that the child might hear during the MRI ...

  9. MRI of the Chest

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    Full Text Available ... body structures. MRI does not use ionizing radiation (x-rays). Detailed MR images allow physicians to evaluate various ... seen by other imaging modalities, such as chest x-ray or CT. A special form of MRI called ...

  10. MRI of the Chest

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    Full Text Available ... lesions seen by other imaging modalities, such as chest x-ray or CT. A special form of MRI called ... perform than other imaging modalities. MRI of the chest takes more time than an x-ray or CT exam. Because of the length of ...

  11. MRI of the Chest

    Medline Plus

    Full Text Available ... zippers and similar metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In ... scanner. top of page How does the procedure work? Unlike ... (CT) scans, MRI does not utilize ionizing radiation. Instead, radiofrequency pulses ...

  12. Cervical MRI scan

    Science.gov (United States)

    ... cancer in the spine Arthritis in the spine MRI works better than CT scan in diagnosing these problems ... test. The strong magnetic fields created during an MRI can cause heart pacemakers and other implants to not work as well. It can also cause a piece ...

  13. MRI of the Chest

    Medline Plus

    Full Text Available ... Test/Treatment Patient Type Screening/Wellness Disease/Condition Safety En Español More Info Images/Videos About Us ... absolutely necessary for medical treatment. See the MRI Safety page for more information about pregnancy and MRI. ...

  14. MRI of the Chest

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    Full Text Available ... Whether a child requires sedation depends on the child's age, intellectual development and the type of exam. Moderate and conscious ... for MRI by showing them a dummy scanner, play the noises that the child might hear during the MRI exam, answer any ...

  15. MRI of the Chest

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    Full Text Available ... if a finding is stable or changed over time. top of page What are the benefits vs. risks? Benefits MRI is a ... resonance imaging harms the fetus, pregnant women usually are advised not to have ... may take more time to perform than other imaging modalities. MRI of ...

  16. MRI of the Chest

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    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam is safe for patients with metal implants, except for a few types. People with the ...

  17. SATURATED ZONE IN-SITU TESTING

    Energy Technology Data Exchange (ETDEWEB)

    P.W. REIMUS

    2004-11-08

    The purpose of this scientific analysis is to document the results and interpretations of field experiments that test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain, Nevada. The test interpretations provide estimates of flow and transport parameters used in the development of parameter distributions for total system performance assessment (TSPA) calculations. These parameter distributions are documented in ''Site-Scale Saturated Zone Flow Model (BSC 2004 [DIRS 170037]), Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]), Saturated Zone Colloid Transport (BSC 2004 [DIRS 170006]), and ''Saturated Zone Flow and Transport Model Abstraction'' (BSC 2004 [DIRS 170042]). Specifically, this scientific analysis contributes the following to the assessment of the capability of the SZ to serve as part of a natural barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvial Testing Complex (ATC) located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass

  18. Fat-saturated post gadolinium T1 imaging of the brain in multiple sclerosis

    Energy Technology Data Exchange (ETDEWEB)

    Al-Saeed, Osama; Sheikh, Mehraj (Dept. of Radiology, Kuwait Univ. (Kuwait)), email: osamas@hsc.edu.kw; Ismail, Mohammed (Ibn Sina Hospital (Kuwait)); Athyal, Reji (Amiri Hospital (Kuwait))

    2011-06-15

    Background Magnetic resonance imaging (MRI) is of vital importance in the diagnosis and follow-up of patients with multiple sclerosis (MS). Imaging sequences better demonstrating enhancing lesions can help in detecting active MS plaques. Purpose To evaluate the role of fat-saturated gadolinium-enhanced T1-weighted (T1W) images of the brain in MS and to assess the benefit of performing this additional sequence in the detection of enhancing lesions. Material and Methods In a prospective study over a six-month period, 70 consecutive patients with clinically diagnosed MS were enrolled. These constituted 14 male and 56 female patients between the ages of 21 and 44 years. All the patients underwent brain MRIs on a 1.5 Tesla Magnet. Gadolinium-enhanced T1 images with and without fat saturation were compared and results were recorded and analyzed using a conspicuity score and McNemar test. Results There were a total of 157 lesions detected in 70 patients on post-contrast T1W fat-saturated images compared with 139 lesions seen on the post-contrast T1W fast spin-echo (FSE) images. This was because 18 of the lesions (11.5%) were only seen on the fat-saturated images. In addition, 15 lesions were more conspicuous on the fat saturation sequence (9.5%). The total conspicuity score obtained, including all the lesions, was 2.24 +/-0.60 (SD). Using the two-tailed McNemar test for quantitative analysis, the P value obtained was <0.0001. Conclusion T1W fat-saturated gadolinium-enhanced images show better lesion enhancement than T1W images without fat saturation

  19. The monitoring of venous saturations of oxygen in children with congenitally malformed hearts.

    Science.gov (United States)

    Martin, Jeff; Shekerdemian, Lara S

    2009-02-01

    Mixed venous saturation of oxygen has for some time been used as a tool to assess the adequacy of systemic delivery of oxygen in intensive care. In the post-operative child with cardiac disease, it is increasingly being used to assess adequacy of cardiac output. In many of these patients, true sampling of mixed venous saturation of oxygen is not possible due to the infrequent use of pulmonary arterial catheters, or the presence of intra-cardiac left to right shunting leading to mixing of systemic and pulmonary venous blood. The use of saturation of oxygen in the central venous blood as a surrogate for mixed venous saturation of oxygen has been widely investigated in adults, but its use remains controversial. In this review, we discuss the theory behind the use of mixed venous saturation of oxygen in evaluating cardiac output, the problems pertinent to those patients with congenitally malformed hearts, and explore the evidence for central venous saturation of oxygen as a surrogate for mixed venous saturation of oxygen, and its use as a therapeutic target to improve outcomes in this population of patients.

  20. Global Asymptotic Stability of the Classical PID Controller by Considering Saturation Effects in Industrial Robots

    Directory of Open Access Journals (Sweden)

    Antonio Yarza

    2011-09-01

    Full Text Available An unsolved ancient problem in position control of robot manipulators is to find a stability analysis that proves global asymptotic stability of the classical PID control in closed loop with robot manipulators. The practical evidence suggests that in fact the classical PID in industrial robots is a global regulator. The main goal of the present paper is theoretically to show why in the practice such a fact is achieved. We show that considering the natural saturations of every control stage in practical robots, the classical PID becomes a type of saturated nonlinear PID controller. In this work such a nonlinear PID controller with bounded torques for robot manipulators is proposed. This controller, unlike other saturated nonlinear PID controllers previously proposed, uses a single saturation for the three terms of the controller. Global asymptotical stability is proved via Lyapunov stability theory. Experimental results are presented in order to observe the performance of the proposed controller.

  1. Ultrasound- and MRI-Guided Prostate Biopsy

    Science.gov (United States)

    ... Resources Professions Site Index A-Z Ultrasound- and MRI-Guided Prostate Biopsy Ultrasound- and MRI-guided prostate ... MRI-guided Prostate Biopsy? What is Ultrasound- and MRI-guided Prostate Biopsy? Ultrasound- and MRI-guided prostate ...

  2. MRI of the Body (Chest, Abdomen, Pelvis)

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Body Magnetic resonance imaging (MRI) of the body ... limitations of MRI of the Body? What is MRI of the Body? Magnetic resonance imaging (MRI) is ...

  3. Saturated fats and cardiovascular disease risk: A review

    OpenAIRE

    Ishi Khosla; Gayatri C Khosla1

    2017-01-01

    Saturated fats have been in the line of fire for more than three decades. The major mistake in understanding fats was to equate all saturated fatty acids as one. The oversimplification of the relationship of saturated fats with cardiovascular disease (CVD) led to unwarranted removal of some valuable fats from our diets. Recently, the relationship of dietary saturated fats and that of individual saturated fatty acids (SFAs) to CVD risk has been reevaluated. All saturated fats are not equal and...

  4. MRI/linac integration.

    Science.gov (United States)

    Lagendijk, Jan J W; Raaymakers, Bas W; Raaijmakers, Alexander J E; Overweg, Johan; Brown, Kevin J; Kerkhof, Ellen M; van der Put, Richard W; Hårdemark, Björn; van Vulpen, Marco; van der Heide, Uulke A

    2008-01-01

    In radiotherapy the healthy tissue involvement still poses serious dose limitations. This results in sub-optimal tumour dose and complications. Daily image guided radiotherapy (IGRT) is the key development in radiation oncology to solve this problem. MRI yields superb soft-tissue visualization and provides several imaging modalities for identification of movements, function and physiology. Integrating MRI functionality with an accelerator can make these capacities available for high precision, real time IGRT. The system being built at the University Medical Center Utrecht is a 1.5T MRI scanner, with diagnostic imaging functionality and quality, integrated with a 6MV radiotherapy accelerator. The realization of a prototype of this hybrid system is a joint effort between the Radiotherapy Department of the University of Utrecht, the Netherlands, Elekta, Crawley, U.K., and Philips Research, Hamburg, Germany. Basically, the design is a 1.5 T Philips Achieva MRI scanner with a Magnex closed bore magnet surrounded by a single energy (6 MV) Elekta accelerator. Monte Carlo simulations are used to investigate the radiation beam properties of the hybrid system, dosimetry equipment and for the construction of patient specific dose deposition kernels in the presence of a magnetic field. The latter are used to evaluate the IMRT capability of the integrated MRI linac. A prototype hybrid MRI/linac for on-line MRI guidance of radiotherapy (MRIgRT) is under construction. The aim of the system is to deliver the radiation dose with mm precision based on diagnostic quality MR images.

  5. Current and Noise Saturation in Graphene Superlattice

    Science.gov (United States)

    Yang, Wei; Lu, Xiaobo; Berthou, Simon; Wilmart, Quentin; Boukhicha, Mohamed; Voisin, Christophe; Zhang, Guangyu; Placais, Bernard

    One of the merits of graphene is that the Fermi level can be easily tuned by electrical gating, which render charge carriers n type or p type, or even insulating around the Dirac point (DP). By aligning graphene on top of Boron Nitride (BN), the presence of graphene superlattice makes transport properties even more versatile owning to the emergence of secondary Dirac points (SDPs). Here we present a study of high electric field performance of graphene superlattice obtained from epitaxial approach. By using microwave cavity, noise produced from graphene by joule heating is recorded up to 5GHz. Current and noise saturation are observed and investigated. Depending on Fermi energy, saturation can be attributed to intrinsic optical or remote surface polar phonon scattering at a doping far away from DP, while no saturation are found around DP. Moreover, noise saturation is identified around Fermi energy between DP and SDP, which can be attributed to the influence of van Hove singularity arising from the superlattice. Lastly, saturation due to the bias induced shift of DP, or so called Dirac fermion pinch-off, is well observed by local top gate technique. EU Graphene flagship project (Contract No. 604391).

  6. Lipid order, saturation and surface property relationships: a study of human meibum saturation.

    Science.gov (United States)

    Mudgil, Poonam; Borchman, Douglas; Yappert, Marta C; Duran, Diana; Cox, Gregory W; Smith, Ryan J; Bhola, Rahul; Dennis, Gary R; Whitehall, John S

    2013-11-01

    Tear film stability decreases with age however the cause(s) of the instability are speculative. Perhaps the more saturated meibum from infants may contribute to tear film stability. The meibum lipid phase transition temperature and lipid hydrocarbon chain order at physiological temperature (33 °C) decrease with increasing age. It is reasonable that stronger lipid-lipid interactions could stabilize the tear film since these interactions must be broken for tear break up to occur. In this study, meibum from a pool of adult donors was saturated catalytically. The influence of saturation on meibum hydrocarbon chain order was determined by infrared spectroscopy. Meibum is in an anhydrous state in the meibomian glands and on the surface of the eyelid. The influence of saturation on the surface properties of meibum was determined using Langmuir trough technology. Saturation of native human meibum did not change the minimum or maximum values of hydrocarbon chain order so at temperatures far above or below the phase transition of human meibum, saturation does not play a role in ordering or disordering the lipid hydrocarbon chains. Saturation did increase the phase transition temperature in human meibum by over 20 °C, a relatively high amount. Surface pressure-area studies showing the late take off and higher maximum surface pressure of saturated meibum compared to native meibum suggest that the saturated meibum film is quite molecularly ordered (stiff molecular arrangement) and elastic (molecules are able to rearrange during compression and expansion) compared with native meibum films which are more fluid agreeing with the infrared spectroscopic results of this study. In saturated meibum, the formation of compacted ordered islands of lipids above the surfactant layer would be expected to decrease the rate of evaporation compared to fluid and more loosely packed native meibum. Higher surface pressure observed with films of saturated meibum compared to native meibum

  7. MRI in sarcoglycanopathies

    DEFF Research Database (Denmark)

    Tasca, Giorgio; Monforte, Mauro; Díaz-Manera, Jordi

    2018-01-01

    OBJECTIVES: To characterise the pattern and spectrum of involvement on muscle MRI in a large cohort of patients with sarcoglycanopathies, which are limb-girdle muscular dystrophies (LGMD2C-2F) caused by mutations in one of the four genes coding for muscle sarcoglycans. METHODS: Lower limb MRI scans......, while lower leg muscles were relatively spared even in advanced disease. A proximodistal gradient of involvement of vasti muscles was a consistent finding in these patients, including the most severe ones. CONCLUSIONS: Muscle involvement on MRI is consistent in patients with LGMD2C-F and can be helpful...

  8. CGC/saturation approach for soft interactions at high energy: Inclusive production

    Directory of Open Access Journals (Sweden)

    E. Gotsman

    2015-06-01

    Full Text Available In this letter we demonstrate that our dipole model is successful in describing inclusive production within the same framework as diffractive physics. We believe that this achievement stems from the fact that our approach incorporates the positive features of the Reggeon approach and CGC/saturation effective theory, for high energy QCD.

  9. Acoustic Velocity Log Numerical Simulation and Saturation Estimation of Gas Hydrate Reservoir in Shenhu Area, South China Sea

    Directory of Open Access Journals (Sweden)

    Kun Xiao

    2013-01-01

    Full Text Available Gas hydrate model and free gas model are established, and two-phase theory (TPT for numerical simulation of elastic wave velocity is adopted to investigate the unconsolidated deep-water sedimentary strata in Shenhu area, South China Sea. The relationships between compression wave (P wave velocity and gas hydrate saturation, free gas saturation, and sediment porosity at site SH2 are studied, respectively, and gas hydrate saturation of research area is estimated by gas hydrate model. In depth of 50 to 245 m below seafloor (mbsf, as sediment porosity decreases, P wave velocity increases gradually; as gas hydrate saturation increases, P wave velocity increases gradually; as free gas saturation increases, P wave velocity decreases. This rule is almost consistent with the previous research result. In depth of 195 to 220 mbsf, the actual measurement of P wave velocity increases significantly relative to the P wave velocity of saturated water modeling, and this layer is determined to be rich in gas hydrate. The average value of gas hydrate saturation estimated from the TPT model is 23.2%, and the maximum saturation is 31.5%, which is basically in accordance with simplified three-phase equation (STPE, effective medium theory (EMT, resistivity log (Rt, and chloride anomaly method.

  10. Acoustic velocity log numerical simulation and saturation estimation of gas hydrate reservoir in Shenhu area, South China Sea.

    Science.gov (United States)

    Xiao, Kun; Zou, Changchun; Xiang, Biao; Liu, Jieqiong

    2013-01-01

    Gas hydrate model and free gas model are established, and two-phase theory (TPT) for numerical simulation of elastic wave velocity is adopted to investigate the unconsolidated deep-water sedimentary strata in Shenhu area, South China Sea. The relationships between compression wave (P wave) velocity and gas hydrate saturation, free gas saturation, and sediment porosity at site SH2 are studied, respectively, and gas hydrate saturation of research area is estimated by gas hydrate model. In depth of 50 to 245 m below seafloor (mbsf), as sediment porosity decreases, P wave velocity increases gradually; as gas hydrate saturation increases, P wave velocity increases gradually; as free gas saturation increases, P wave velocity decreases. This rule is almost consistent with the previous research result. In depth of 195 to 220 mbsf, the actual measurement of P wave velocity increases significantly relative to the P wave velocity of saturated water modeling, and this layer is determined to be rich in gas hydrate. The average value of gas hydrate saturation estimated from the TPT model is 23.2%, and the maximum saturation is 31.5%, which is basically in accordance with simplified three-phase equation (STPE), effective medium theory (EMT), resistivity log (Rt), and chloride anomaly method.

  11. Soil Structure and Saturated Hydraulic Conductivity

    Science.gov (United States)

    Houskova, B.; Nagy, V.

    The role of soil structure on saturated hydraulic conductivity changes is studied in plough layers of texturally different soils. Three localities in western part of Slovakia in Zitny ostrov (Corn Island) were under investigation: locality Kalinkovo with light Calcaric Fluvisol (FAO 1970), Macov with medium heavy Calcari-mollic Fluvisol and Jurova with heavy Calcari-mollic Fluvisol. Soil structure was determined in dry as well as wet state and in size of macro and micro aggregates. Saturated hydraulic conductivity was measured by the help of double ring method. During the period of ring filling the soil surface was protected against aggregates damage by falling water drops. Spatial and temporal variability of studied parameters was evaluated. Cultivated crops were ensilage maize at medium heavy and heavy soil and colza at light soil. Textural composition of soil and actual water content at the beginning of measurement are one of major factor affecting aggregate stability and consequently also saturated hydraulic conductivity.

  12. Interger multiplication with overflow detection or saturation

    Energy Technology Data Exchange (ETDEWEB)

    Schulte, M.J.; Balzola, P.I.; Akkas, A.; Brocato, R.W.

    2000-01-11

    High-speed multiplication is frequently used in general-purpose and application-specific computer systems. These systems often support integer multiplication, where two n-bit integers are multiplied to produce a 2n-bit product. To prevent growth in word length, processors typically return the n least significant bits of the product and a flag that indicates whether or not overflow has occurred. Alternatively, some processors saturate results that overflow to the most positive or most negative representable number. This paper presents efficient methods for performing unsigned or two's complement integer multiplication with overflow detection or saturation. These methods have significantly less area and delay than conventional methods for integer multiplication with overflow detection and saturation.

  13. The Danish tax on saturated fat

    DEFF Research Database (Denmark)

    Vallgårda, Signild; Holm, Lotte; Jensen, Jørgen Dejgård

    2015-01-01

    BACKGROUND/OBJECTIVES: Health promoters have repeatedly proposed using economic policy tools, taxes and subsidies, as a means of changing consumer behaviour. As the first country in the world, Denmark introduced a tax on saturated fat in 2011. It was repealed in 2012. In this paper, we present...... on saturated fat had been suggested by two expert committees and was introduced with a majority in parliament, as a part of a larger economic reform package. Many actors, including representatives from the food industry and nutrition researchers, opposed the tax both before and after its introduction, claiming......, research was published showing that consumption of saturated fat had declined in Denmark. CONCLUSIONS: The analysis indicates that the Danish tax on fat was introduced mainly to increase public revenue. As the tax had no strong proponents and many influential adversaries, it was repealed. New research...

  14. Brain MRI in Parkinson's disease

    NARCIS (Netherlands)

    Meijer, F.J.A.; Goraj, B.M.

    2014-01-01

    In this review article, conventional brain MRI and advanced MRI techniques in Parkinson`s disease (PD) are discussed, with emphasis on clinical relevance. Conventional brain MRI sequences generally demonstrate limited abnormalities specific for PD and in clinical practice brain MRI is mainly used to

  15. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Head Magnetic resonance imaging (MRI) of the head uses a powerful ... Head? What is MRI of the Head? Magnetic resonance imaging (MRI) is a noninvasive medical test that ...

  16. Value of Perineural Edema/Inflammation Detected by Fat Saturation Sequences in Lumbar Magnetic Resonance Imaging of Patients with Unilateral Sciatica

    Energy Technology Data Exchange (ETDEWEB)

    Sirvanci, M.; Duran, C. (Dept. of Radiology, Faculty of Medicine, Istanbul Bilim Univ., Istanbul (Turkey)); Kara, B.; Onat, L.; Ulusoy, O.L.; Mutlu, A. (Dept. of Radiology of Florence Nightingale Hospital, Istanbul (Turkey)); Ozturk, E. (Dept. of Radiology, GATA Haydarpasa Teaching Hospital, Istanbul (Turkey)); Karatoprak, O. (Dept. of Orthopeadic Surgery, Kadikoy Florence Nightingale Hospital, Istanbul (Turkey))

    2009-02-15

    Background: Routine lumbar spine magnetic resonance imaging (MRI) may not show any evidence of the cause of sciatica in some cases. The relationship between nerve root compression detected on lumbar MRI and sciatica is also sometimes uncertain. Purpose: To ascertain whether axial (and, when necessary, sagittal and coronal) short-tau inversion recovery or fat-saturated T2-weighted MRI findings can be used to study the level of sciatica in patients with a non-yielding routine MRI examination. Material and Methods: A total of 215 patients with unilateral sciatica underwent MRI. All patients were asked to complete pain drawing forms describing their pain dermatomal distributions. Perineural edema/inflammation corresponding to the pain location indicated by the pain drawings was sought on short-tau inversion recovery or fat-saturated T2-weighted images. Results: Routine MRI findings revealed that 110 of the 215 patients had nerve root compromise related to the patients' symptoms. Routine MRI could not ascertain the cause of these symptoms in the remaining 105 patients. In 31 (29.5%) of these 105 patients, short-tau inversion recovery or fat-saturated T2-weighted magnetic resonance images revealed perineural edema/inflammation surrounding the nerve roots related to the pain locations indicated in the pain drawings. Conclusion: Axial (and, when required, sagittal and coronal) short-tau inversion recovery or fat-saturated T2-weighted magnetic resonance images may be helpful for revealing additional findings in cases of unexplained sciatica in standard magnetic resonance imaging. However, the value of this imaging may be not great enough to justify routine use of these additional sequences to study the level of sciatica

  17. Tracking Controller for Intrinsic Output Saturated Systems in Presence of Amplitude and Rate Input Saturations

    DEFF Research Database (Denmark)

    Chater, E.; Giri, F.; Guerrero, Josep M.

    2014-01-01

    We consider the problem of controlling plants that are subject to multiple saturation constraints. Especially, we are interested in linear systems whose input is subject to amplitude and rate constraints of saturation type. Furthermore, the considered systems output is also subject to an intrinsi...

  18. Femoral venous oxygen saturation is no surrogate for central venous oxygen saturation

    NARCIS (Netherlands)

    van Beest, Paul A.; van der Schors, Alice; Liefers, Henriette; Coenen, Ludo G. J.; Braam, Richard L.; Habib, Najib; Braber, Annemarije; Scheeren, Thomas W. L.; Kuiper, Michael A.; Spronk, Peter E.

    2012-01-01

    Objective:  The purpose of our study was to determine if central venous oxygen saturation and femoral venous oxygen saturation can be used interchangeably during surgery and in critically ill patients. Design:  Prospective observational controlled study. Setting:  Nonacademic university-affiliated

  19. M theory as a holographic field theory

    Science.gov (United States)

    Hořava, Petr

    1999-02-01

    We suggest that M theory could be nonperturbatively equivalent to a local quantum field theory. More precisely, we present a ``renormalizable'' gauge theory in eleven dimensions, and show that it exhibits various properties expected of quantum M theory, most notably the holographic principle of 't Hooft and Susskind. The theory also satisfies Mach's principle: A macroscopically large space-time (and the inertia of low-energy excitations) is generated by a large number of ``partons'' in the microscopic theory. We argue that at low energies in large eleven dimensions, the theory should be effectively described by eleven-dimensional supergravity. This effective description breaks down at much lower energies than naively expected, precisely when the system saturates the Bekenstein bound on energy density. We show that the number of partons scales like the area of the surface surrounding the system, and discuss how this holographic reduction of degrees of freedom affects the cosmological constant problem. We propose the holographic field theory as a candidate for a covariant, nonperturbative formulation of quantum M theory.

  20. Saturated poroelastic actuators generated by topology optimization

    DEFF Research Database (Denmark)

    Andreasen, Casper Schousboe; Sigmund, Ole

    2011-01-01

    In this paper the fluid-structure interaction problem of a saturated porous media is considered. The pressure coupling properties of porous saturated materials change with the microstructure and this is utilized in the design of an actuator using a topology optimized porous material. By maximizing...... the coupling of internal fluid pressure and elastic shear stresses a slab of the optimized porous material deflects/deforms when a pressure is imposed and an actuator is created. Several phenomenologically based constraints are imposed in order to get a stable force transmitting actuator....

  1. On the saturation of astrophysical dynamos

    DEFF Research Database (Denmark)

    Dorch, Bertil; Archontis, Vasilis

    2004-01-01

    In the context of astrophysical dynamos we illustrate that the no-cosines flow, with zero mean helicity, can drive fast dynamo action and we study the dynamo's mode of operation during both the linear and non-linear saturation regimes. It turns out that in addition to a high growth rate in the li......In the context of astrophysical dynamos we illustrate that the no-cosines flow, with zero mean helicity, can drive fast dynamo action and we study the dynamo's mode of operation during both the linear and non-linear saturation regimes. It turns out that in addition to a high growth rate...

  2. Site-Scale Saturated Zone Flow Model

    Energy Technology Data Exchange (ETDEWEB)

    G. Zyvoloski

    2003-12-17

    The purpose of this model report is to document the components of the site-scale saturated-zone flow model at Yucca Mountain, Nevada, in accordance with administrative procedure (AP)-SIII.lOQ, ''Models''. This report provides validation and confidence in the flow model that was developed for site recommendation (SR) and will be used to provide flow fields in support of the Total Systems Performance Assessment (TSPA) for the License Application. The output from this report provides the flow model used in the ''Site-Scale Saturated Zone Transport'', MDL-NBS-HS-000010 Rev 01 (BSC 2003 [162419]). The Site-Scale Saturated Zone Transport model then provides output to the SZ Transport Abstraction Model (BSC 2003 [164870]). In particular, the output from the SZ site-scale flow model is used to simulate the groundwater flow pathways and radionuclide transport to the accessible environment for use in the TSPA calculations. Since the development and calibration of the saturated-zone flow model, more data have been gathered for use in model validation and confidence building, including new water-level data from Nye County wells, single- and multiple-well hydraulic testing data, and new hydrochemistry data. In addition, a new hydrogeologic framework model (HFM), which incorporates Nye County wells lithology, also provides geologic data for corroboration and confidence in the flow model. The intended use of this work is to provide a flow model that generates flow fields to simulate radionuclide transport in saturated porous rock and alluvium under natural or forced gradient flow conditions. The flow model simulations are completed using the three-dimensional (3-D), finite-element, flow, heat, and transport computer code, FEHM Version (V) 2.20 (software tracking number (STN): 10086-2.20-00; LANL 2003 [161725]). Concurrently, process-level transport model and methodology for calculating radionuclide transport in the saturated zone at Yucca

  3. MRI of the Chest

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    Full Text Available ... patient to have an allergy to a gadolinium-based contrast agent used for MRI than the iodine- ... For more information on adverse reactions to gadolinium-based contrast agents, please consult the ACR Manual on ...

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    Full Text Available ... be removed. MRI exams generally include multiple runs (sequences), some of which may last several minutes. The ... You may be able to relax between imaging sequences, but will be asked to maintain your position ...

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  14. MRI of the Chest

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... very rare occasions, a few patients experience side effects from the contrast material, including nausea, headache and ...

  15. MRI of the Chest

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    Full Text Available ... tissue and fluid, known as edema . MRI typically costs more and may take more time to perform ... accredited facilities database . This website does not provide cost information. The costs for specific medical imaging tests, ...

  16. MRI of the Chest

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    Full Text Available ... period is necessary. You may resume your usual activities and normal diet immediately after the exam. On ... that time the imaging based on the electrical activity of the heart, such as electrocardiography (EKG). MRI ...

  17. MRI of the Chest

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    Full Text Available ... to detect and identify any metal objects. In general, metal objects used in orthopedic surgery pose no ... units provide very high quality images for many types of exams. Older open MRI units may not ...

  18. Constrained MRI Impedance Imaging

    National Research Council Canada - National Science Library

    Plewes, Donald

    2002-01-01

    An approach for imaging electric tissue properties in vivo is proposed. The technique relies upon the integration of MRI data with electrical potential measurements made over the surface of the patient...

  19. MRI of the Chest

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    Full Text Available ... you have any devices or metal in your body. Guidelines about eating and drinking before your exam ... soft tissues, bone and virtually all other internal body structures. MRI does not use ionizing radiation (x- ...

  20. MRI of the Chest

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    Full Text Available ... devices or metal in your body. Guidelines about eating and drinking before your exam vary between facilities. ... fitting and has no metal fasteners. Guidelines about eating and drinking before an MRI exam vary with ...

  1. MRI of the Chest

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    Full Text Available ... blood flow to the heart) and myocardial infarct (scar in the heart muscle due to prior obstruction ... contrast material except when absolutely necessary for medical treatment. See the MRI Safety page for more information ...

  2. MRI of the Chest

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    Full Text Available ... MRI examinations may require you to receive an injection of contrast material into the bloodstream. The radiologist , ... the potential risks. Pregnant women should not receive injections of gadolinium contrast material except when absolutely necessary ...

  3. MRI of the Chest

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    Full Text Available ... in the first three to four months of pregnancy unless the potential benefit from the MRI exam is assumed to outweigh the potential risks. Pregnant women should not receive injections of gadolinium ...

  4. MRI of the Chest

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    Full Text Available ... for more information. top of page How should I prepare? You may be asked to wear a ... total exam time. top of page What will I experience during and after the procedure? Most MRI ...

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    Full Text Available ... surgery pose no risk during MRI. However, a recently placed artificial joint may require the use of ... maintain your position without movement as much as possible. You will usually be alone in the exam ...

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    Full Text Available ... activated. Some centers provide earplugs, while others use headphones to reduce the intensity of the sounds made ... Children will be given appropriately sized earplugs or headphones during the exam. MRI scanners are air-conditioned ...

  7. MRI of the Chest

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    Full Text Available ... MRI) of the chest uses a powerful magnetic field, radio waves and a computer to produce detailed ... there’s a possibility you are pregnant. The magnetic field is not harmful, but it may cause some ...

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    Full Text Available ... by showing them a dummy scanner, play the noises that the child might hear during the MRI ... being imaged, send and receive radio waves, producing signals that are detected by the coils. The electric ...

  9. MRI of the Chest

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    Full Text Available ... any recent surgeries. Some conditions, such as severe kidney disease, may prevent you from being given gadolinium contrast ... an MRI. If you have a history of kidney disease or liver transplant, it will be necessary to ...

  10. MRI of the Chest

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    Full Text Available ... be examined on a computer monitor, transmitted electronically, printed or copied to a CD or uploaded to ... MRI exam, a physician, nurse or technologist will insert an intravenous (IV) catheter, also known as an ...

  11. MRI of the Chest

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  12. MRI of the Chest

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    Full Text Available ... magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... tell the technologist if you have medical or electronic devices in your body. These objects may interfere ...

  13. MRI of the Chest

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    Full Text Available ... may cause some medical devices to malfunction. Most orthopedic implants pose no risk, but you should always ... metal objects. In general, metal objects used in orthopedic surgery pose no risk during MRI. However, a ...

  14. MRI of the Chest

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    Full Text Available ... the eyes are particularly important because they may move during the scan, possibly causing blindness. Dyes used in tattoos may contain iron and could heat up during an MRI scan, but this is rare. ...

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... radiation. MR images of the heart and vascular structures are often clearer and more detailed than with ...

  16. MRI of the Chest

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    Full Text Available ... scanner. top of page How does the procedure work? Unlike conventional x-ray examinations and computed tomography ( ... that magnetic resonance imaging harms the fetus, pregnant women usually are advised not to have an MRI ...

  17. MRI of the Chest

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    Full Text Available ... wall, pleura, heart and vessels, from almost any angle. MRI also provides movie-like sequential imaging of ... The images can then be studied from different angles by the interpreting radiologist. Frequently, the differentiation of ...

  18. MRI of the Chest

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    Full Text Available ... provides movie-like sequential imaging of the cardiovascular system that is important to assess the health and ... the magnet. Some MRI units, called short-bore systems , are designed so that the magnet does not ...

  19. MRI of the Chest

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    Full Text Available ... is not harmful, but it may cause some medical devices to malfunction. Most orthopedic implants pose no ... Chest? Magnetic resonance imaging (MRI) is a noninvasive medical test that physicians use to diagnose medical conditions. ...

  20. MRI of the Chest

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    Full Text Available ... by showing them a dummy scanner, play the noises that the child might hear during the MRI exam, answer any questions and explain the procedure to relieve their anxiety. Some pediatric facilities also provide goggles or headsets ...

  1. MRI of the Chest

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  2. MRI of the Chest

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  3. MRI of the Chest

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  4. MRI of the Chest

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    Full Text Available ... asked to wear a gown. If you have claustrophobia or anxiety, you may want to ask your ... information about pregnancy and MRI. If you have claustrophobia (fear of enclosed spaces) or anxiety, you may ...

  5. MRI of the Chest

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    Full Text Available ... vary between facilities. Unless you are told otherwise, take your regular medications as usual. Leave jewelry at ... you may follow your regular daily routine and take food and medications as usual. Some MRI examinations ...

  6. MRI of the Chest

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    Full Text Available ... Infants and young children usually require sedation or anesthesia to complete an MRI exam without moving. Whether ... A physician or nurse specializing in sedation or anesthesia for children should be available during the exam ...

  7. MRI of the Chest

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  8. MRI of the Chest

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  9. MRI of the Chest

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    Full Text Available ... in tattoos may contain iron and could heat up during an MRI scan, but this is rare. ... who will share the results with you. Follow-up examinations may be necessary. Your doctor will explain ...

  10. MRI of the Chest

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  11. MRI of the Chest

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    Full Text Available ... will hear and feel loud tapping or thumping sounds when the coils that generate the radiofrequency pulses ... use headphones to reduce the intensity of the sounds made by the MRI machine. You may be ...

  12. MRI of the Chest

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    Full Text Available ... their nature and the strength of the MRI magnet. Many implanted devices will have a pamphlet explaining ... large cylinder-shaped tube surrounded by a circular magnet. You will lie on a moveable examination table ...

  13. MRI of the Chest

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    Full Text Available ... The magnetic field is produced by passing an electric current through wire coils in most MRI units. Other coils, located in the machine and in some cases, placed around the part ...

  14. Sinus MRI scan

    Science.gov (United States)

    ... tissues surrounding the eye (orbital cellulitis) Nasal polyps Sinusitis -- acute Sinusitis -- chronic Talk to your provider if you have ... therefore is not typically used for suspected acute sinusitis. Alternative Names MRI of the sinuses; Magnetic resonance ...

  15. MRI of the Chest

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    Full Text Available ... traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. You will lie ... your skin at the site of the IV tube insertion. Some patients may sense a temporary metallic ...

  16. MRI of the Chest

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    Full Text Available ... imaging (MRI) exam. View full size with caption Pediatric Content Some imaging tests and treatments have special pediatric considerations. The teddy bear denotes child-specific content. ...

  17. MRI of the Chest

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    Full Text Available ... The magnetic field is produced by passing an electric current through wire coils in most MRI units. ... signals that are detected by the coils. The electric current does not come in contact with the ...

  18. MRI of the Chest

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    Full Text Available ... with claustrophobia. Newer open MRI units provide very high quality images for many types of exams. Older ... believed to be caused by the injection of high doses of gadolinium-based contrast material in patients ...

  19. Combined PET/MRI

    DEFF Research Database (Denmark)

    Bailey, D. L.; Pichler, B. J.; Gückel, B.

    2015-01-01

    This paper summarises key themes and discussions from the 4th international workshop dedicated to the advancement of the technical, scientific and clinical applications of combined positron emission tomography (PET)/magnetic resonance imaging (MRI) systems that was held in Tübingen, Germany, from...... February 23 to 27, 2015. Specifically, we summarise the three days of invited presentations from active researchers in this and associated fields augmented by round table discussions and dialogue boards with specific topics. These include the use of PET/MRI in cardiovascular disease, paediatrics, oncology......, neurology and multi-parametric imaging, the latter of which was suggested as a key promoting factor for the wider adoption of integrated PET/MRI. Discussions throughout the workshop and a poll taken on the final day demonstrated that attendees felt more strongly that PET/MRI has further advanced in both...

  20. MRI of the Chest

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    Full Text Available ... body. Guidelines about eating and drinking before your exam vary between facilities. Unless you are told otherwise, ... doctor for a mild sedative prior to the exam. What is MRI of the Chest? What are ...

  1. MRI of the Chest

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    Full Text Available ... that the child might hear during the MRI exam, answer any questions and explain the procedure to relieve their anxiety. Some pediatric facilities also provide goggles or headsets ...

  2. MRI of the Chest

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    Full Text Available ... by showing them a dummy scanner, play the noises that the child might hear during the MRI ... a noninvasive imaging technique that does not involve exposure to ionizing radiation. MR images of the heart ...

  3. MRI of the Chest

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    Full Text Available ... images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam ... Foreign bodies near and especially lodged in the eyes are particularly important because they may move during ...

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    Full Text Available ... copied to a CD or uploaded to a digital cloud server. MRI of the chest gives detailed ... type your comment or suggestion into the following text box: Comment: E-mail: Area code: Phone no: ...

  5. MRI of the Chest

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    Full Text Available ... high quality images for many types of exams. Older open MRI units may not provide this same ... You may resume your usual activities and normal diet immediately after the exam. On very rare occasions, ...

  6. MRI of the Chest

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    Full Text Available ... ports artificial limbs or metallic joint prostheses implanted nerve stimulators metal pins, screws, plates, stents or surgical ... the magnet. Some MRI units, called short-bore systems , are designed so that the magnet does not ...

  7. MRI of the Chest

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    Full Text Available ... patient story here Images × Image Gallery Radiologist preparing patient for magnetic resonance imaging (MRI) exam. View full size with caption Pediatric Content Some imaging tests and treatments have special ...

  8. MRI of the Chest

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    Full Text Available ... prior to your scheduled examination. Infants and young children usually require sedation or anesthesia to complete an MRI exam without moving. Whether a child requires sedation depends on the child's age, intellectual ...

  9. MRI of the Chest

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    Full Text Available ... over time. top of page What are the benefits vs. risks? Benefits MRI is a noninvasive imaging technique that does ... data suggest that it is safe to continue breastfeeding after receiving intravenous contrast. For further information please ...

  10. MRI of the Chest

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    Full Text Available ... the same effect. A very irregular heartbeat may affect the quality of images obtained using techniques that ... time an MRI takes to complete, many young children and infants require sedation to hold still for ...

  11. MRI of the Chest

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    Full Text Available ... used in tattoos may contain iron and could heat up during an MRI scan, but this is ... special pediatric considerations. The teddy bear denotes child-specific content. Related Articles and Media MR Angiography (MRA) ...

  12. MRI of the Chest

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    Full Text Available ... MRI exams is less likely to produce an allergic reaction than the iodine-based contrast materials used for ... There is a very slight risk of an allergic reaction if contrast material is injected. Such reactions are ...

  13. MRI of the Chest

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  14. MRI of the Chest

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    Full Text Available ... your regular medications as usual. Leave jewelry at home and wear loose, comfortable clothing. You may be ... Jewelry and other accessories should be left at home, if possible, or removed prior to the MRI ...

  15. MRI of the Chest

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    Full Text Available ... internal body structures. MRI does not use ionizing radiation (x-rays). Detailed MR images allow physicians to ... x-ray contrast material, drugs, food, or the environment, or if you have asthma. The contrast material ...

  16. MRI of the Chest

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    Full Text Available ... Older open MRI units may not provide this same image quality. Certain types of exams cannot be ... the metallic objects. Patient movement can have the same effect. A very irregular heartbeat may affect the ...

  17. MRI of the Chest

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    Full Text Available ... may follow your regular daily routine and take food and medications as usual. Some MRI examinations may ... to iodine or x-ray contrast material, drugs, food, or the environment, or if you have asthma. ...

  18. MRI of the Chest

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    Full Text Available ... may have. top of page What does the equipment look like? The traditional MRI unit is a ... traction devices and many types of life support equipment may distort the MR images and as a ...

  19. MRI of the Chest

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    Full Text Available ... evaluation with additional views or a special imaging technique. A follow-up examination may also be necessary ... vs. risks? Benefits MRI is a noninvasive imaging technique that does not involve exposure to ionizing radiation. ...

  20. MRI of the Chest

    Medline Plus

    Full Text Available ... systemic fibrosis is currently a recognized, but rare, complication of MRI believed to be caused by the ... injection minimizes the risk of this very rare complication. There is a very slight risk of an ...

  1. MRI of the Chest

    Medline Plus

    Full Text Available ... devices they may have. top of page What does the equipment look like? The traditional MRI unit ... room from the scanner. top of page How does the procedure work? Unlike conventional x-ray examinations ...

  2. MRI of the Chest

    Medline Plus

    Full Text Available ... implanted drug infusion ports artificial limbs or metallic joint prostheses implanted nerve stimulators metal pins, screws, plates, ... risk during MRI. However, a recently placed artificial joint may require the use of another imaging procedure. ...

  3. MRI of the Chest

    Medline Plus

    Full Text Available ... metal in your body. Guidelines about eating and drinking before your exam vary between facilities. Unless you ... has no metal fasteners. Guidelines about eating and drinking before an MRI exam vary with the specific ...

  4. MRI of the Chest

    Medline Plus

    Full Text Available ... of the chest uses a powerful magnetic field, radio waves and a computer to produce detailed pictures ... medical conditions. MRI uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed ...

  5. MRI of the Chest

    Medline Plus

    Full Text Available ... Thus, the child remains motionless allowing for good quality images. Jewelry and other accessories should be left ... claustrophobia. Newer open MRI units provide very high quality images for many types of exams. Older open ...

  6. MRI of the Chest

    Medline Plus

    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will ... are not limited to: artificial heart valves implanted drug infusion ports artificial limbs or metallic joint prostheses ...

  7. MRI of the Chest

    Medline Plus

    Full Text Available ... before an MRI exam vary with the specific exam and with the imaging facility. Unless you are told otherwise, you may follow your regular daily routine and take food and medications as usual. ...

  8. MRI of the Chest

    Medline Plus

    Full Text Available ... have an allergy to a gadolinium-based contrast agent used for MRI than the iodine-containing contrast ... information on adverse reactions to gadolinium-based contrast agents, please consult the ACR Manual on Contrast Media . ...

  9. MRI of the Chest

    Medline Plus

    Full Text Available ... unborn baby will be in a strong magnetic field, pregnant women should not have this exam in the first three to four months of pregnancy unless the potential benefit from the MRI exam is assumed to ...

  10. MRI of the Chest

    Medline Plus

    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... from the contrast material, including nausea, headache and pain at the site of injection. Similarly, patients are ...

  11. MRI of the Chest

    Medline Plus

    Full Text Available ... take food and medications as usual. Some MRI examinations may require you to receive an injection of ... for a mild sedative prior to your scheduled examination. Infants and young children usually require sedation or ...

  12. MRI of the Chest

    Medline Plus

    Full Text Available ... information on the chemicals present in the body's cells, may also be performed during the MRI exam ... in diagnosing a broad range of conditions, including cancer, heart and vascular disease, heart valve abnormalities, bone ...

  13. MRI of the Chest

    Medline Plus

    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... the same effect. A very irregular heartbeat may affect the quality of images obtained using techniques that ...

  14. MRI of the Chest

    Medline Plus

    Full Text Available ... the radiofrequency pulses are activated. Some centers provide earplugs, while others use headphones to reduce the intensity ... magnetic environment. Children will be given appropriately sized earplugs or headphones during the exam. MRI scanners are ...

  15. MRI of the Chest

    Medline Plus

    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... American College of Radiology (ACR) and the European Society of Urogenital Radiology note that the available data ...

  16. MRI of the Chest

    Medline Plus

    Full Text Available ... These items include: jewelry, watches, credit cards and hearing aids, all of which can be damaged pins, ... devices that contain metal may malfunction or cause problems during an MRI exam. Nephrogenic systemic fibrosis is ...

  17. [MRI features of neurosyphilis].

    Science.gov (United States)

    Brisset, M; Chadenat, M L; Cordoliani, Y; Kamga-Tallom, R; D'Anglejean, J; Pico, F

    2011-04-01

    Neurosyphilis is rare today. It arises on average 20 years after poorly treated or untreated primary syphilis. Considering the decline in the incidence of syphilitic meningo encephalitis and the little known MRI aspects, we report the case of a patient affected by neurosyphilis occurring after primary syphilis untreated for 25 years. A 65-year-old man presented typical clinical features including general paresis with psychiatric disorders, maniac access, and frontal syndrome as well as tabes dorsalis and Argyll-Robertson pupil. Brain MRI showed bilateral high intensity signals on the T2 weighted sequence located in mesiotemporal, insular, frontal regions. Very few cases of neurosyphilis with detailed brain MRI aspects have been reported. The interest of this case report is first to recall the importance of syphilitic serology in patients with subacute psychiatric disorders and secondly to present rarely reported aspects of the brain MRI. Copyright © 2011. Published by Elsevier Masson SAS.

  18. MRI of the Chest

    Medline Plus

    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings ... there is any question of their presence, an x-ray may be taken to detect and identify any ...

  19. MRI of the Chest

    Medline Plus

    Full Text Available ... your regular daily routine and take food and medications as usual. Some MRI examinations may require you to receive an injection of contrast material into the bloodstream. The radiologist , ...

  20. MRI of the Chest

    Medline Plus

    Full Text Available ... and may add approximately 15 minutes to the total exam time. top of page What will I ... the limitations of MRI of the Chest? High-quality images are assured only if you are able ...

  1. MRI of the Chest

    Medline Plus

    Full Text Available ... be examined on a computer monitor, transmitted electronically, printed or copied to a CD or uploaded to a digital cloud server. MRI of the chest gives detailed pictures of structures within ...

  2. MRI of intracranial calcifications

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jin Wha; Chang, Kee Hyun; Park, Jung Mi; Han, Moon Hee; Han, Man Chung; Kim, Chu Wan [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    1988-12-15

    Recently computed tomography(CT) has been rapidly replaced by magnetic resonance imaging (MRI) in diagnosis of majority of intracranial diseases. But MRI still has some limitation, one of which is its inferiority in detecting calcification. MRI of intracranial calcification has been known to be variable in signal intensity. We retrospectively analyzed the MRI of 26 patients with intracranial calcified lesions in order to evaluate the MR intensity of calcification and to assess the capability of MRI in detecting calcification in various intracranial lesions. All the MRI were obtained using routine T1-and T2-weighted spin eco pulse sequences on 2.0T superconducting system. The 26 patients consisted of 13 brain tumors (4 oligodendrogliomas, 2 craniopharyngiomas, 2 astrocytomas, 1 gem cell tumor, 1 medulloblastoma, 1 ependympma, and pathologically unconfirmed 2 cases), 11 infectious diseases (1 paragonimiasis, 1 sparganosis, 2 cysticercosis, 3 tuberculosis, and 4 unknown cases), and 2 undetermined pathologies. Eighty-two percent (9/11) of infections disease, and 50% (1/2) of undetermined group showed signal diminution or signal void on both T1-and T2-weighted image (T1W1, T2W1). Twenty-four percent (3/13) of brain tumors showed signal diminution on both T1W1 and T2W1. In 46% (6/13) and 61% (8/13) of brain tumors the signal intensities were isointense on T1W1 and T1W1, respectively. Unexpectedly, 3 oligodendrogliomas showed high signal intensity on T1W1, two of which showed com plexed signal intensity mixed with high, iso, and low signal intensities on T2W1. In remained cases (18% (2/11) of infectious diseases and 50% (1/2) of undetermined group) the signal intensities were mixed. With simultaneous review of CT and MRI in each case, the calcification (at least one in cases showing multiple ones) was identifiable on MRI in 62% (8/13) of rumors, 82% (9/11) of infectious diseases, and 100% (2/2) in undetermined group. In 36% (4/11) of infectious diseases, fewer number of

  3. Combined PET/MRI

    DEFF Research Database (Denmark)

    Bailey, D L; Pichler, B J; Gückel, B

    2018-01-01

    The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants c...... of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care....

  4. MRI Physics Workshop:

    OpenAIRE

    Daryoush Saedi

    2009-01-01

    Accurate knowledge of the basic principle of imaging physics helps better understanding of normal anatomy and pathological imaging findings of the diseases."n"n This is more necessary in advanced imaging techniques like MRI because of the complexity of the basic physics of the technique. In basic MRI physics workshop, we discuss about this technique from the primary concepts. The content is very simplified and is showed by slides, animation and easy pictures for better understanding...

  5. MRI of plantar fasciitis

    Energy Technology Data Exchange (ETDEWEB)

    Roger, B.; Grenier, P. [Service de Radiologie Polyvalente Diagnostique et Interventionelle, Hopital de la Pitie, 83, boulevard de l`Hopital, F-75651 Paris Cedex 13 (France)

    1997-12-01

    At present, MRI is the only imaging method that can precisely visualize lesions of the superficial plantar aponeurosis, whether they be musculoaponeurositides, enthesopathies or tears, and whether they be acute or chronic, with or without complications. By its direct visualization of the lesion, MRI enables an accurate assessment of the injury to be made and thereby better orients the therapeutic strategy. (orig.) With 11 figs., 15 refs.

  6. MRI-guided brachytherapy

    Science.gov (United States)

    Tanderup, Kari; Viswanathan, Akila; Kirisits, Christian; Frank, Steven J.

    2014-01-01

    The application of MRI-guided brachytherapy has demonstrated significant growth during the last two decades. Clinical improvements in cervix cancer outcomes have been linked to the application of repeated MRI for identification of residual tumor volumes during radiotherapy. This has changed clinical practice in the direction of individualized dose administration, and mounting evidence of improved clinical outcome with regard to local control, overall survival as well as morbidity. MRI-guided prostate HDR and LDR brachytherapy has improved the accuracy of target and organs-at-risk (OAR) delineation, and the potential exists for improved dose prescription and reporting for the prostate gland and organs at risk. Furthermore, MRI-guided prostate brachytherapy has significant potential to identify prostate subvolumes and dominant lesions to allow for dose administration reflecting the differential risk of recurrence. MRI-guided brachytherapy involves advanced imaging, target concepts, and dose planning. The key issue for safe dissemination and implementation of high quality MRI-guided brachytherapy is establishment of qualified multidisciplinary teams and strategies for training and education. PMID:24931089

  7. Fullerene Transport in Saturated Porous Media

    Science.gov (United States)

    We investigated the effects of background solution chemistry and residence time within the soil column on the transport of aqu/C60 through saturated ultrapure quartz sand columns. Aqu/C60 breakthrough curves were obtained under different pore water velocities, solution pHs, and i...

  8. Oxygenation of saturated and unsaturated hydrocarbons with ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 118; Issue 5. Oxygenation of saturated and unsaturated hydrocarbons with sodium periodate catalyzed by manganese(III) tetra-arylporphyrins, to study the axial ligation of imidazole. Reza Tayebee. Volume 118 Issue 5 September 2006 pp 429-433 ...

  9. Nasal pulse oximetry overestimates oxygen saturation

    DEFF Research Database (Denmark)

    Rosenberg, J; Pedersen, M H

    1990-01-01

    Ten surgical patients were monitored with nasal and finger pulse oximetry (Nellcor N-200) for five study periods with alternating mouth and nasal breathing and switching of cables and sensors. Nasal pulse oximetry was found to overestimate arterial oxygen saturation by 4.7 (SD 1.4%) (bias...

  10. Determination of saturated and unsaturated hydraulic conductivity ...

    African Journals Online (AJOL)

    The estimation of hydraulic conductivity indicates how fluids flow through a substance and thus determine the water balance in the soil profile. In determining the saturated and unsaturated hydraulic conductivity of soil, five plots of 5.0 x 4.0 m were prepared with a PVC access tube installed in each plot. The plots were ...

  11. Understanding 'saturation' of radar signals over forests.

    Science.gov (United States)

    Joshi, Neha; Mitchard, Edward T A; Brolly, Matthew; Schumacher, Johannes; Fernández-Landa, Alfredo; Johannsen, Vivian Kvist; Marchamalo, Miguel; Fensholt, Rasmus

    2017-06-14

    There is an urgent need to quantify anthropogenic influence on forest carbon stocks. Using satellite-based radar imagery for such purposes has been challenged by the apparent loss of signal sensitivity to changes in forest aboveground volume (AGV) above a certain 'saturation' point. The causes of saturation are debated and often inadequately addressed, posing a major limitation to mapping AGV with the latest radar satellites. Using ground- and lidar-measurements across La Rioja province (Spain) and Denmark, we investigate how various properties of forest structure (average stem height, size and number density; proportion of canopy and understory cover) simultaneously influence radar backscatter. It is found that increases in backscatter due to changes in some properties (e.g. increasing stem sizes) are often compensated by equal magnitude decreases caused by other properties (e.g. decreasing stem numbers and increasing heights), contributing to the apparent saturation of the AGV-backscatter trend. Thus, knowledge of the impact of management practices and disturbances on forest structure may allow the use of radar imagery for forest biomass estimates beyond commonly reported saturation points.

  12. Spontaneous emission from saturated parametric amplifiers

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Ott, Johan Raunkjær; Steffensen, Henrik

    2009-01-01

    Noise performance of parametric amplifiers is typically calculated assuming un-depleted operation. However, in many applications especially when applied as regenerative amplifiers in systems based on phase shift keyed modulation schemes, this assumption is not valid. Here we show the impact...... on accumulated spontaneous emission for a parametric amplifier operated in saturation....

  13. Elevated transferrin saturation and risk of diabetes

    DEFF Research Database (Denmark)

    Ellervik, Christina; Mandrup-Poulsen, Thomas; Andersen, Henrik Ullits

    2011-01-01

    OBJECTIVE We tested the hypothesis that elevated transferrin saturation is associated with an increased risk of any form of diabetes, as well as type 1 or type 2 diabetes separately. RESEARCH DESIGN AND METHODS We used two general population studies, The Copenhagen City Heart Study (CCHS, N = 9...

  14. Saturated fat, carbohydrates and cardiovascular disease

    NARCIS (Netherlands)

    Kuipers, R. S.; de Graaf, D. J.; Luxwolda, M. F.; Muskiet, M. H. A.; Dijck-Brouwer, D. A. J.; Muskiet, F. A. J.

    The dietary intake of saturated fatty acids (SAFA) is associated with a modest increase in serum total cholesterol, but not with cardiovascular disease (CVD). Replacing dietary SAFA with carbohydrates (CHO), notably those with a high glycaemic index, is associated with an increase in CVD risk in

  15. Two-beam interaction in saturable media

    DEFF Research Database (Denmark)

    Schjødt-Eriksen, Jens; Schmidt, Michel R.; Juul Rasmussen, Jens

    1998-01-01

    The dynamics of two coupled soliton solutions of the nonlinear Schrodinger equation with a saturable nonlinearity is investigated It is shown by means of a variational method and by direct numerical calculations that two well-separated solitons can orbit around each other, if their initial velocity...

  16. Synthesis and characterization of saturated polyester and ...

    Indian Academy of Sciences (India)

    Saturated polyester resin, derived from the glycolysis of polyethyleneterephthalate (PET) was examined as an effective way for PET recycling. The glycolyzed PET (GPET) was reacted with the mixture of phthalic anhydride and ethylene glycol (EG) with varied compositions and their reaction kinetic were studied. During ...

  17. Multi-spectral imaging of oxygen saturation

    Science.gov (United States)

    Savelieva, Tatiana A.; Stratonnikov, Aleksander A.; Loschenov, Victor B.

    2008-06-01

    The system of multi-spectral imaging of oxygen saturation is an instrument that can record both spectral and spatial information about a sample. In this project, the spectral imaging technique is used for monitoring of oxygen saturation of hemoglobin in human tissues. This system can be used for monitoring spatial distribution of oxygen saturation in photodynamic therapy, surgery or sports medicine. Diffuse reflectance spectroscopy in the visible range is an effective and extensively used technique for the non-invasive study and characterization of various biological tissues. In this article, a short review of modeling techniques being currently in use for diffuse reflection from semi-infinite turbid media is presented. A simple and practical model for use with a real-time imaging system is proposed. This model is based on linear approximation of the dependence of the diffuse reflectance coefficient on relation between absorbance and reduced scattering coefficient. This dependence was obtained with the Monte Carlo simulation of photon propagation in turbid media. Spectra of the oxygenated and deoxygenated forms of hemoglobin differ mostly in the red area (520 - 600 nm) and have several characteristic points there. Thus four band-pass filters were used for multi-spectral imaging. After having measured the reflectance, the data obtained are used for fitting the concentration of oxygenated and free hemoglobin, and hemoglobin oxygen saturation.

  18. Microscopic analysis of saturable absorbers: Semiconductor saturable absorber mirrors versus graphene

    Energy Technology Data Exchange (ETDEWEB)

    Hader, J.; Moloney, J. V. [Nonlinear Control Strategies, Inc., 3542 N. Geronimo Ave., Tucson, Arizona 85705 (United States); College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Yang, H.-J.; Scheller, M. [College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Koch, S. W. [Department of Physics and Materials Sciences Center, Philipps Universität Marburg, Renthof 5, 35032 Marburg (Germany)

    2016-02-07

    Fully microscopic many-body calculations are used to study the influence of strong sub-picosecond pulses on the carrier distributions and corresponding optical response in saturable absorbers used for mode-locking—semiconductor (quantum well) saturable absorber mirrors (SESAMs) and single layer graphene based saturable absorber mirrors (GSAMs). Unlike in GSAMs, the saturation fluence and recovery time in SESAMs show a strong spectral dependence. While the saturation fluence in the SESAM is minimal at the excitonic bandgap, the optimal recovery time and least pulse distortion due to group delay dispersion are found for excitation higher in the first subband. For excitation near the SESAM bandgap, the saturation fluence is about one tenth of that in the GSAM. At energies above the bandgap, the fluences in both systems become similar. A strong dependence of the saturation fluence on the pulse width in both systems is caused by carrier relaxation during the pulse. The recovery time in graphene is found to be about two to four times faster than that in the SESAMs. The occurrence of negative differential transmission in graphene is shown to be caused by dopant related carriers. In SESAMs, a negative differential transmission is found when exciting below the excitonic resonance where excitation induced dephasing leads to an enhancement of the absorption. Comparisons of the simulation data to the experiment show a very good quantitative agreement.

  19. Microscopic analysis of saturable absorbers: Semiconductor saturable absorber mirrors versus graphene

    Science.gov (United States)

    Hader, J.; Yang, H.-J.; Scheller, M.; Moloney, J. V.; Koch, S. W.

    2016-02-01

    Fully microscopic many-body calculations are used to study the influence of strong sub-picosecond pulses on the carrier distributions and corresponding optical response in saturable absorbers used for mode-locking—semiconductor (quantum well) saturable absorber mirrors (SESAMs) and single layer graphene based saturable absorber mirrors (GSAMs). Unlike in GSAMs, the saturation fluence and recovery time in SESAMs show a strong spectral dependence. While the saturation fluence in the SESAM is minimal at the excitonic bandgap, the optimal recovery time and least pulse distortion due to group delay dispersion are found for excitation higher in the first subband. For excitation near the SESAM bandgap, the saturation fluence is about one tenth of that in the GSAM. At energies above the bandgap, the fluences in both systems become similar. A strong dependence of the saturation fluence on the pulse width in both systems is caused by carrier relaxation during the pulse. The recovery time in graphene is found to be about two to four times faster than that in the SESAMs. The occurrence of negative differential transmission in graphene is shown to be caused by dopant related carriers. In SESAMs, a negative differential transmission is found when exciting below the excitonic resonance where excitation induced dephasing leads to an enhancement of the absorption. Comparisons of the simulation data to the experiment show a very good quantitative agreement.

  20. FLASH: A finite element computer code for variably saturated flow

    Energy Technology Data Exchange (ETDEWEB)

    Baca, R.G.; Magnuson, S.O.

    1992-05-01

    A numerical model was developed for use in performance assessment studies at the INEL. The numerical model, referred to as the FLASH computer code, is designed to simulate two-dimensional fluid flow in fractured-porous media. The code is specifically designed to model variably saturated flow in an arid site vadose zone and saturated flow in an unconfined aquifer. In addition, the code also has the capability to simulate heat conduction in the vadose zone. This report presents the following: description of the conceptual frame-work and mathematical theory; derivations of the finite element techniques and algorithms; computational examples that illustrate the capability of the code; and input instructions for the general use of the code. The FLASH computer code is aimed at providing environmental scientists at the INEL with a predictive tool for the subsurface water pathway. This numerical model is expected to be widely used in performance assessments for: (1) the Remedial Investigation/Feasibility Study process and (2) compliance studies required by the US Department of Energy Order 5820.2A.

  1. Quasilinear saturation of the aperiodic ordinary mode streaming instability

    Energy Technology Data Exchange (ETDEWEB)

    Stockem Novo, A., E-mail: anne@tp4.rub.de; Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Yoon, P. H. [Institute for Physical Science & Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Lazar, M. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Centre for Mathematical Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium); Poedts, S. [Centre for Mathematical Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium); Seough, J. [Faculty of Human Development, University of Toyama, 3190, Gofuku, Toyama City, Toyama 930-8555 (Japan); International Research Fellow of the Japan Society for the Promotion of Science, Tokyo (Japan)

    2015-09-15

    In collisionless plasmas, only kinetic instabilities and fluctuations are effective in reducing the free energy and scatter plasma particles, preventing an increase of their anisotropy. Solar energetic outflows into the interplanetary plasma give rise to important thermal anisotropies and counterstreaming motions of plasma shells, and the resulting instabilities are expected to regulate the expansion of the solar wind. The present paper combines quasilinear theory and kinetic particle-in-cell simulations in order to study the weakly nonlinear saturation of the ordinary mode in hot counter-streaming plasmas with a temperature anisotropy as a follow-up of the paper by Seough et al. [Phys. Plasmas 22, 082122 (2015)]. This instability provides a plausible mechanism for the origin of dominating, two-dimensional spectrum of transverse magnetic fluctuations observed in the solar wind. Stimulated by the differential motion of electron counterstreams the O mode instability may convert their free large-scale energy by nonlinear collisionless dissipation on plasma particles.

  2. Standing torsional waves in a fully saturated, porous, circular cylinder

    CERN Document Server

    Solorza, S; 10.1111/j.1365-246X.2004.02198.x

    2004-01-01

    For dynamic measurement of the elastic moduli of a porous material saturated with viscous fluid using the resonance-bar technique, one also observes attenuation. In this article we have carried out the solution of the boundary-value problem associated with standing torsional oscillations of a finite, poroelastic, circular cylinder cast in the framework of volume-averaged theory of poroelasticity. Analysing this solution by eigenvalue perturbation approach we are able to develop expressions for torsional resonance and temporal attenuation frequencies in which the dependence upon the material properties are transparent. It shows how the attenuation is controlled by the permeability and the fluid properties, and how the resonance frequency drops over its value for the dry solid-frame due to the drag effect of fluid mass. Based upon this work we have a firm basis to determine solid-frame shear modulus, permeability, and tortuosity factor from torsional oscillation experiments.

  3. Replacing foods high in saturated fat by low-saturated fat alternatives: a computer simulation of the potential effects on reduction of saturated fat consumption

    NARCIS (Netherlands)

    Schickenberg, B.; Assema, P.; Brug, J.; Verkaik-Kloosterman, J.; Ocke, M.C.; Vries, de N.

    2009-01-01

    10 en%) increased from 23.3 % to 86.0 %. We conclude that the replacement of relatively few important high-saturated fat products by available lower-saturated fat alternatives can significantly reduce saturated fat intake and increase the proportion of individuals complying with recommended intake

  4. Saturated Zone In-Situ Testing

    Energy Technology Data Exchange (ETDEWEB)

    P. W. Reimus; M. J. Umari

    2003-12-23

    The purpose of this scientific analysis is to document the results and interpretations of field experiments that have been conducted to test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain. The test interpretations provide estimates of flow and transport parameters that are used in the development of parameter distributions for Total System Performance Assessment (TSPA) calculations. These parameter distributions are documented in the revisions to the SZ flow model report (BSC 2003 [ 162649]), the SZ transport model report (BSC 2003 [ 162419]), the SZ colloid transport report (BSC 2003 [162729]), and the SZ transport model abstraction report (BSC 2003 [1648701]). Specifically, this scientific analysis report provides the following information that contributes to the assessment of the capability of the SZ to serve as a barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvium Testing Complex (ATC), which is located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, and

  5. MRI of the lung

    Energy Technology Data Exchange (ETDEWEB)

    Kauczor, Hans-Ulrich (ed.) [University Clinic Heidelberg (Germany). Diagnostic and Interventional Radiology

    2009-07-01

    For a long time, only chest X-ray and CT were used to image lung structure, while nuclear medicine was employed to assess lung function. During the past decade significant developments have been achieved in the field of magnetic resonance imaging (MRI), enabling MRI to enter the clinical arena of chest imaging. Standard protocols can now be implemented on up-to-date scanners, allowing MRI to be used as a first-line imaging modality for various lung diseases, including cystic fibrosis, pulmonary hypertension and even lung cancer. The diagnostic benefits stem from the ability of MRI to visualize changes in lung structure while simultaneously imaging different aspects of lung function, such as perfusion, respiratory motion, ventilation and gas exchange. On this basis, novel quantitative surrogates for lung function can be obtained. This book provides a comprehensive overview of how to use MRI for imaging of lung disease. Special emphasis is placed on benign diseases requiring regular monitoring, given that it is patients with these diseases who derive the greatest benefit from the avoidance of ionizing radiation. (orig.)

  6. MRI in Japanese encephalitis

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. [Sanjay Gandhi Post Graduate Inst. of Medical Sciences, Lucknow (India). Dept. of Radiology; Misra, U.K. [Sanjay Gandhi Post Graduate Inst. of Medical Sciences, Lucknow (India). Dept. of Neurology; Kalita, J. [Sanjay Gandhi Post Graduate Inst. of Medical Sciences, Lucknow (India). Dept. of Neurology; Salwani, V. [Sanjay Gandhi Post Graduate Inst. of Medical Sciences, Lucknow (India). Dept. of Radiology; Gupta, R.K. [Sanjay Gandhi Post Graduate Inst. of Medical Sciences, Lucknow (India). Dept. of Radiology; Gujral, R. [Sanjay Gandhi Post Graduate Inst. of Medical Sciences, Lucknow (India). Dept. of Radiology

    1997-03-01

    We document the MRI features in seven patients with Japanese encephalitis. MRI was carried out on a 1.5 T system within 10-60 days of onset. In all the patients MRI revealed bilateral thalamic lesions, haemorrhagic in five. Signal changes were present in the cerebrum in four patients, the midbrain and cerebellum in three each, the pons in two and the basal ganglia in one. The lesions were haemorrhagic in three of the four patients with lesions in the cortex, two of the three with lesions in the midbrain and cerebellum, but the pontine lesions were haemorrhagic in both patients. Spinal cord involvement was seen in one of the three patients who underwent MRI. In two patients MRI was repeated 3 years after the onset, showing marked reduction in abnormal signal; and all the lesions gave low signal on both T1- and T2-weighted images. Bilateral thalamic involvement, especially haemorrhagic, may be considered characteristic of Japanese encephalitis, especially in endemic areas. (orig.)

  7. Comparison of pulseoximetry oxygen saturation and arterial oxygen saturation in open heart intensive care unit

    Directory of Open Access Journals (Sweden)

    Alireza Mahoori

    2013-08-01

    Full Text Available Background: Pulseoximetry is widely used in the critical care setting, currently used to guide therapeutic interventions. Few studies have evaluated the accuracy of SPO2 (puls-eoximetry oxygen saturation in intensive care unit after cardiac surgery. Our objective was to compare pulseoximetry with arterial oxygen saturation (SaO2 during clinical routine in such patients, and to examine the effect of mild acidosis on this relationship.Methods: In an observational prospective study 80 patients were evaluated in intensive care unit after cardiac surgery. SPO2 was recorded and compared with SaO2 obtained by blood gas analysis. One or serial arterial blood gas analyses (ABGs were performed via a radial artery line while a reliable pulseoximeter signal was present. One hundred thirty seven samples were collected and for each blood gas analyses, SaO2 and SPO2 we recorded.Results: O2 saturation as a marker of peripheral perfusion was measured by Pulseoxim-etry (SPO2. The mean difference between arterial oxygen saturation and pulseoximetry oxygen saturation was 0.12%±1.6%. A total of 137 paired readings demonstrated good correlation (r=0.754; P<0.0001 between changes in SPO2 and those in SaO2 in samples with normal hemoglobin. Also in forty seven samples with mild acidosis, paired readings demonstrated good correlation (r=0.799; P<0.0001 and the mean difference between SaO2 and SPO2 was 0.05%±1.5%.Conclusion: Data showed that in patients with stable hemodynamic and good signal quality, changes in pulseoximetry oxygen saturation reliably predict equivalent changes in arterial oxygen saturation. Mild acidosis doesn’t alter the relation between SPO2 and SaO2 to any clinically important extent. In conclusion, the pulse oximeter is useful to monitor oxygen saturation in patients with stable hemodynamic.

  8. [Monitoring of jugular venous oxygen saturation].

    Science.gov (United States)

    Nakamura, Shunsuke

    2011-04-01

    The continuous monitoring of jugular venous oxygen saturation(SjO2) has become a practical method for monitoring global cerebral oxygenation and metabolism. SjO2 reflects the balance between the cerebral blood flow and the cerebral metabolic rate for oxygen (CMRO2), if arterial oxyhemoglobin saturation, hemoglobin concentration remain constant. Normal SjO2 values range between 55% and 75%. Low SjO2 indicates cerebral hypoperfusion or ischemia. Conversely, an increased SjO2 indicates either cerebral hyperemia or a disorder that decreases CMRO2. In minimizing secondary brain damage following resuscitation from cardiopulmonary arrest, SjO2 monitoring is thus considered to be an integral part of multimodality monitoring and can provide important information for the management of patients in neurointensive care.

  9. The danish tax on saturated fat

    DEFF Research Database (Denmark)

    Jensen, Jørgen Dejgård; Smed, Sinne

    Denmark introduced a new tax on saturated fat in food products with effect from October 2011. The objective of this paper is to make an effect assessment of this tax for some of the product categories most significantly affected by the new tax, namely fats such as butter, butter-blends, margarine...... on saturated fat in food products has had some effects on the market for the considered products, in that the level of consumption of fats dropped by 10 – 20%. Furthermore, the analysis points at shifts in demand from high-price supermarkets towards low-price discount stores – a shift that seems to have been...... – and broaden – the analysis at a later stage, when data are available for a longer period after the introduction of the fat tax....

  10. Nonlinear saturation of Weibel-type instabilities

    Science.gov (United States)

    Srinivasan, Bhuvana; Cagas, Petr; Hakim, Ammar

    2017-10-01

    Weibel-type instabilities, which grow in plasmas with anisotropic velocity distribution, have been studied for many years and drawn recent interest due to their broad applicability spanning from laboratory laser plasmas to origins of intergalactic magnetic fields in astrophysical plasmas. Magnetic particle trapping has been considered as the main mechanism of the nonlinear saturation of these instabilities. However, novel continuum kinetic and two-fluid five moment simulations show that there are additional effects - the transverse flow introduced by the magnetic field creates a secondary electrostatic two-stream instability which alters the saturation and is responsible for a quasi-periodic behavior in the nonlinear phase. This research was supported by the Air Force Office of Scientific Research under Grant Number FA9550-15-1-0193.

  11. WAter Saturation Shift Referencing (WASSR) for chemical exchange saturation transfer experiments

    Science.gov (United States)

    Kim, Mina; Gillen, Joseph; Landman, Bennett. A.; Zhou, Jinyuan; van Zijl, Peter C.M.

    2010-01-01

    Chemical exchange saturation transfer (CEST) is a contrast mechanism exploiting exchange-based magnetization transfer (MT) between solute and water protons. CEST effects compete with direct water saturation and conventional MT processes and generally can only be quantified through an asymmetry analysis of the water saturation spectrum (Z-spectrum) with respect to the water frequency, a process that is exquisitely sensitive to magnetic field inhomogeneities. Here, it is shown that direct water saturation imaging allows measurement of the absolute water frequency in each voxel, allowing proper centering of Z-spectra on a voxel-by-voxel basis independent of spatial B0 field variations. Optimal acquisition parameters for this “water saturation shift referencing” or “WASSR” approach were estimated using Monte Carlo simulations and later confirmed experimentally. The optimal ratio of the WASSR sweep width to the linewidth of the direct saturation curve was found to be 3.3–4.0, requiring a sampling of 16–32 points. The frequency error was smaller than 1 Hz at signal to noise ratios of 40 or higher. The WASSR method was applied to study glycogen, where the chemical shift difference between the hydroxyl (OH) protons and bulk water protons at 3T is so small (0.75–1.25 ppm) that the CEST spectrum is inconclusive without proper referencing. PMID:19358232

  12. Water saturation shift referencing (WASSR) for chemical exchange saturation transfer (CEST) experiments.

    Science.gov (United States)

    Kim, Mina; Gillen, Joseph; Landman, Bennett A; Zhou, Jinyuan; van Zijl, Peter C M

    2009-06-01

    Chemical exchange saturation transfer (CEST) is a contrast mechanism that exploits exchange-based magnetization transfer (MT) between solute and water protons. CEST effects compete with direct water saturation and conventional MT processes, and generally can only be quantified through an asymmetry analysis of the water saturation spectrum (Z-spectrum) with respect to the water frequency, a process that is exquisitely sensitive to magnetic field inhomogeneities. Here it is shown that direct water saturation imaging allows measurement of the absolute water frequency in each voxel, allowing proper centering of Z-spectra on a voxel-by-voxel basis independently of spatial B(0) field variations. Optimal acquisition parameters for this "water saturation shift referencing" (WASSR) approach were estimated using Monte Carlo simulations and later confirmed experimentally. The optimal ratio of the WASSR sweep width to the linewidth of the direct saturation curve was found to be 3.3-4.0, requiring a sampling of 16-32 points. The frequency error was smaller than 1 Hz at signal-to-noise ratios of 40 or higher. The WASSR method was applied to study glycogen, where the chemical shift difference between the hydroxyl (OH) protons and bulk water protons at 3T is so small (0.75-1.25 ppm) that the CEST spectrum is inconclusive without proper referencing.

  13. [MRI for myocarditis].

    Science.gov (United States)

    Gutberlet, M; Lücke, C; Krieghoff, C; Hildebrand, L; Lurz, P; Steiner, J; Adam, J; Eitel, I; Thiele, H; Grothoff, M; Grotthoff, M; Lehmkuhl, L

    2013-01-01

    Cardiovascular magnetic resonance imaging (CMRI) has become the primary tool for the non-invasive assessment in patients with suspected myocarditis, especially after exclusion of acute coronary syndrome (ACS) for the differential diagnosis. Various MRI parameters are available which have different accuracies. Volumetric and functional ventricular assessment and the occurrence of pericardial effusion alone demonstrate only a poor sensitivity and specificity. The calculation of the T2-ratio (edema assessment), the early or global relative myocardial enhancement (gRE) and the late gadolinium enhancement (LGE), which represents irreversibly injured myocardium, are more specific parameters. All MRI parameters demonstrate the best accuracy in infarct-like acute myocarditis, whereas in chronic myocarditis sensitivity and specificity are less accurate. Therefore, a multisequential (at least two out of three parameters are positive) approach is recommended. The assessment of the value of newer, more quantitative MRI sequences, such as T1 and T2-mapping is still under investigation.

  14. MRI Conditional Pacemakers

    Directory of Open Access Journals (Sweden)

    Johnson Francis

    2014-10-01

    Full Text Available Conventionally, magnetic resonance [MR] imaging is an absolute contraindication for those with an implanted pacemaker.This represents a significant clinical problem as several studies have shown approximately 75% of patients with pacemakers will have an indication for an MRI scan. Patients over the age of 65 are twice as likely to require an MRI and 80% of pacemaker patients are over the age of 65. MR imaging is an important source of information for neurological disorders and several soft tissue abnormalities. Hence denying this important diagnostic modality for those with an implanted pacemaker and other cardiac implantable electronic devices [CIED] is a tremendous clinical problem both because of concerns about MRI signals interfering with the function of the pacemaker and the pacemaker in turn interfering with the MR images.

  15. MRI of oriental cholangiohepatitis

    Energy Technology Data Exchange (ETDEWEB)

    Wani, N.A., E-mail: ahmad77chinar@gmail.co [Department of Radiodiagnosis and Imaging, Sher-I-Kashmir Institute of Medical Sciences (SKIMS), Srinagar (India); Robbani, I.; Kosar, T. [Department of Radiodiagnosis and Imaging, Sher-I-Kashmir Institute of Medical Sciences (SKIMS), Srinagar (India)

    2011-02-15

    Oriental cholangiohepatitis (OCH) also called recurrent pyogenic cholangitis is characterized by intrahepatic duct calculi, strictures, and recurrent infections. In turn cholangitis can result in multiple hepatic abscesses, further biliary strictures, and in severe cases, progressive hepatic parenchymal destruction, cirrhosis, and portal hypertension. Magnetic resonance cholangiopancreatography (MRCP) and conventional T1-weighted (T1 W) and T2-weighted (T2 W) magnetic resonance imaging (MRI) findings have been described in patients with OCH. MRCP findings include duct dilation, strictures, and calculi. MRCP can help to localize the diseased ducts and determine the severity of involvement. T1 and T2 W sequences reveal the parenchymal changes of atrophy, abscess formation, and portal hypertension in addition to calculi. Post-treatment changes are also well depicted using MRI. Comprehensive, non-invasive assessment is achieved by using conventional MRI and MRCP in OCH providing a roadmap for endoscopic or surgical management.

  16. Gluon saturation beyond (naive) leading logs

    Energy Technology Data Exchange (ETDEWEB)

    Beuf, Guillaume

    2014-12-15

    An improved version of the Balitsky–Kovchegov equation is presented, with a consistent treatment of kinematics. That improvement allows to resum the most severe of the large higher order corrections which plague the conventional versions of high-energy evolution equations, with approximate kinematics. This result represents a further step towards having high-energy QCD scattering processes under control beyond strict Leading Logarithmic accuracy and with gluon saturation effects.

  17. 2D Saturable Absorbers for Fibre Lasers

    Directory of Open Access Journals (Sweden)

    Robert I. Woodward

    2015-11-01

    Full Text Available Two-dimensional (2D nanomaterials are an emergent and promising platform for future photonic and optoelectronic applications. Here, we review recent progress demonstrating the application of 2D nanomaterials as versatile, wideband saturable absorbers for Q-switching and mode-locking fibre lasers. We focus specifically on the family of few-layer transition metal dichalcogenides, including MoS2, MoSe2 and WS2.

  18. Stabilization of Neutral Systems with Saturating Actuators

    Directory of Open Access Journals (Sweden)

    F. El Haoussi

    2012-01-01

    to determine stabilizing state-feedback controllers with large domain of attraction, expressed as linear matrix inequalities, readily implementable using available numerical tools and with tuning parameters that make possible to select the most adequate solution. These conditions are derived by using a Lyapunov-Krasovskii functional on the vertices of the polytopic description of the actuator saturations. Numerical examples demonstrate the effectiveness of the proposed technique.

  19. Optimal oxygen saturation in premature infants

    Directory of Open Access Journals (Sweden)

    Meayoung Chang

    2011-09-01

    Full Text Available There is a delicate balance between too little and too much supplemental oxygen exposure in premature infants. Since underuse and overuse of supplemental oxygen can harm premature infants, oxygen saturation levels must be monitored and kept at less than 95% to prevent reactive oxygen species-related diseases, such as retinopathy of prematurity and bronchopulmonary dysplasia. At the same time, desaturation below 80 to 85% must be avoided to prevent adverse consequences, such as cerebral palsy. It is still unclear what range of oxygen saturation is appropriate for premature infants; however, until the results of further studies are available, a reasonable target for pulse oxygen saturation (SpO2 is 90 to 93% with an intermittent review of the correlation between SpO2 and the partial pressure of arterial oxygen tension (PaO2. Because optimal oxygenation depends on individuals at the bedside making ongoing adjustments, each unit must define an optimal target range and set alarm limits according to their own equipment or conditions. All staff must be aware of these values and adjust the concentration of supplemental oxygen frequently.

  20. MRI-based liver iron content determination at 3 T in regularly transfused patients by signal intensity ratio using an alternative analysis approach based on R{sub 2}* theory

    Energy Technology Data Exchange (ETDEWEB)

    Wunderlich, A.P. [Universitaetsklinikum Ulm (Germany). Section for Experimental Radiology; Cario, H. [Universitaetsklinik Ulm (Germany). Children' s Hospital; Bommer, M. [Alb-Fils-Clinics, Goeppingen (Germany). Hematology and Oncology Dept.; Beer, M.; Schmidt, S.A. [Universitaetsklinikum Ulm (Germany). Dept. for Diagnostic and Interventional Radiology; Juchems, M.S. [Klinikum Konstanz (Germany). Diagnostic and Interventional Radiology

    2016-09-15

    To evaluate the feasibility of addressing liver iron content (LIC) in regularly transfused patients by MR imaging at 3 T based on the signal intensity ratio (SIR). An innovative data analysis approach was developed for this purpose. 47 consecutive examinations of regularly transfused patients were included. In all cases, we expected high LIC levels. Patients were scanned with MRI at 3 T with multi-echo gradient echo sequences (GRE) at four different flip angles between 20 and 90 with echo times (TE) ranging from 0.9 to 9.8 ms. Spin-echo protocols were acquired to determine the LIC with a reference MRI method working at 1.5 T. 3 T GRE data were analyzed using the liver-to-muscle SIR. Since the method known for 1.5 T was not expected to be applicable for analyzing 3 T data, theoretic dependence of the SIR on the LIC was derived from the equation describing R{sub 2}* signal decay. Obtained SIR values were correlated to reference LIC to get a relation for calculating LIC from SIR quantities. LIC values and their uncertainties were determined from GRE data and correlated to LIC reference values. For two LIC thresholds, the diagnostic accuracy was determined. LIC was reliably determined from SIR in our patient cohort even for large LIC values. Median of LIC uncertainties was 10%, and the diagnostic accuracy was 0.92 and 0.91, respectively. Determination of even high LIC, resulting in small SIR values, is feasible at 3 T using appropriate SIR analysis.

  1. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... medically necessary. MRI may not always distinguish between cancer tissue and fluid, known as edema . MRI typically ... Brain Tumors Radiation Therapy for Head and Neck Cancer Others : American Stroke Association National Stroke Association top ...

  2. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... You may resume your usual activities and normal diet immediately after the exam. On very rare occasions, ... medically necessary. MRI may not always distinguish between cancer tissue and fluid, known as edema . MRI typically ...

  3. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... information on the chemicals present in the body's cells, may also be performed during the MRI exam ... can help physicians evaluate the structures of the brain and can also provide functional information (fMRI) in ...

  4. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Head Magnetic resonance imaging (MRI) of the head uses a powerful magnetic field, radio waves and a computer to produce ...

  5. Quality assurance in functional MRI

    DEFF Research Database (Denmark)

    Liu, Thomas T; Glover, Gary H; Mueller, Bryon A

    2015-01-01

    Over the past 20 years, functional magnetic resonance imaging (fMRI) has ben- efited greatly from improvements in MRI hardware and software. At the same time, fMRI researchers have pushed the technical limits of MRI systems and greatly in- fluenced the development of state-of-the-art systems....... Minimizing image noise and maximizing system stability is critical in fMRI because the blood oxygenation level- dependent (BOLD) signal changes that are used for most fMRI studies represent only a small fraction of the total MR signal. In addition, multiple imaging volumes must be acquired over time to track...... cognitive processes. As a result, MRI scanners must have excellent time-series stability to accurately measure BOLD signal changes over the course of a long time series (typically on the order of 10 min per scan). fMRI studies are particularly demanding on the scanner hardware because they utilize fast...

  6. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... may not fit into the opening of certain types of MRI machines. The presence of an implant ...

  7. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... affecting the MRI images, these objects can become projectiles within the MRI scanner room and may cause ... at a very early stage by mapping the motion of water molecules in the tissue. This water ...

  8. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... treatment. See the MRI Safety page for more information about pregnancy and MRI. If you have claustrophobia (fear of enclosed spaces) or anxiety, you may want to ask your physician for ...

  9. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... have a personal story about radiology? Share your patient story here Images ... (fMRI) - Brain Head and Neck Cancer Treatment Brain Tumor Treatment Magnetic Resonance Imaging (MRI) ...

  10. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... a very small chance of irritation of your skin at the site of the IV tube insertion. ... detail makes MRI an invaluable tool in early diagnosis and evaluation of many conditions, including tumors. MRI ...

  11. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... ionizing radiation. MRI can help physicians evaluate the structures of the brain and can also provide functional ...

  12. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... content. Related Articles and Media MR Angiography (MRA) Magnetic Resonance, Functional (fMRI) - Brain Head and Neck Cancer Treatment Brain Tumor Treatment Magnetic Resonance Imaging (MRI) Safety Alzheimer's Disease Head Injury Brain ...

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    Full Text Available ... a CD or uploaded to a digital cloud server. Currently, MRI is the most sensitive imaging test ... Brain Tumor Treatment Magnetic Resonance Imaging (MRI) Safety Alzheimer's Disease Head Injury Brain Tumors Images related to Magnetic ...

  14. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... Articles and Media MR Angiography (MRA) Magnetic Resonance, Functional (fMRI) - Brain Head and Neck Cancer Treatment Brain Tumor Treatment Magnetic Resonance Imaging (MRI) Safety Alzheimer's Disease Head Injury Brain Tumors Images related to ...

  15. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... interfere with the magnetic field of the MRI unit, metal and electronic items are not allowed in ... does the equipment look like? The traditional MRI unit is a large cylinder-shaped tube surrounded by ...

  16. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... top of page What are the benefits vs. risks? Benefits MRI is a noninvasive imaging technique that ... than 30 minutes from the onset of symptoms. Risks The MRI examination poses almost no risk to ...

  17. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... detail makes MRI an invaluable tool in early diagnosis and evaluation of many conditions, including tumors. MRI ... the technologist or nurse will monitor your vital signs to minimize this risk. Although the strong magnetic ...

  18. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam is safe for patients with metal implants, except for a few types. ...

  19. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... are the limitations of MRI of the Head? What is MRI of the Head? Magnetic resonance imaging ( ... brain) in routine clinical practice. top of page What are some common uses of the procedure? MR ...

  20. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... women should not have this exam in the first three to four months of pregnancy unless the ... not to have an MRI exam during the first trimester unless medically necessary. MRI may not always ...

  1. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... is done because a potential abnormality needs further evaluation with additional views or a special imaging technique. ... MRI an invaluable tool in early diagnosis and evaluation of many conditions, including tumors. MRI enables the ...

  2. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... copied to a CD or uploaded to a digital cloud server. Currently, MRI is the most sensitive ... Brain Tumor Treatment Magnetic Resonance Imaging (MRI) Safety Alzheimer's Disease Head Injury Brain Tumors Images related to Magnetic ...

  3. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... claustrophobia. Newer open MRI units provide very high quality images for many types of exams. Older open MRI units may not provide this same image quality. Certain types of exams cannot be performed using ...

  4. Getting an MRI (For Kids)

    Science.gov (United States)

    ... Weight for Me? What Is an Intellectual Disability? Movie: Endocrine System Getting an MRI ... MRI (magnetic resonance imaging) scan creates detailed pictures of the inside of the body. The test is painless. All you'll need ...

  5. Getting an MRI (For Kids)

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    Full Text Available ... Weight for Me? What Is an Intellectual Disability? Movie: Endocrine System Getting an MRI ... MRI (magnetic resonance imaging) scan creates detailed pictures of the inside of the body. The test is painless. All you'll need ...

  6. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... devices require a short period of time after placement (usually six weeks) before being safe for MRI ... devices that contain metal may malfunction or cause problems during an MRI exam. Nephrogenic systemic fibrosis is ...

  7. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... This detail makes MRI an invaluable tool in early diagnosis and evaluation of many conditions, including tumors. ... information. MRI can detect stroke at a very early stage by mapping the motion of water molecules ...

  8. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... or headphones during the exam. MRI scanners are air-conditioned and well-lit. Music may be played ... the limitations of MRI of the Head? High-quality images are assured only if you are able ...

  9. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will ... MRI. For more information, consult your radiologist. The computer workstation that processes the imaging information is located ...

  10. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... information on the chemicals present in the body's cells, may also be performed during the MRI exam ... early diagnosis and evaluation of many conditions, including tumors. MRI enables the discovery of abnormalities that might ...

  11. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... conditions. MRI uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures ... does not completely surround you. Some newer MRI machines have a larger diameter bore which can be ...

  12. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will ... information on the chemicals present in the body's cells, may also be performed during the MRI exam ...

  13. Propagation des ondes acoustiques dans les milieux poreux saturés Propagation of Acoustic Waves in Saturated Porous Media

    Directory of Open Access Journals (Sweden)

    Coussy O.

    2006-11-01

    Full Text Available Ce travail comporte deux parties. La première partie concerne la théorie de la propagation des ondes acoustiques dans les milieux poreux saturés. Une revue des différentes méthodes existantes est faite et un développement critique de la théorie de Biot est exposé en détail. On examine en particulier les différents résultats auxquels cette théorie conduit et on regarde, dans quelles conditions et sur quels problèmes géophysiques, les phénomènes physiques mis en évidence peuvent jouer de manière notable. Dans la deuxième partie, on présente une vérification expérimentale due à Plona (1980 de la théorie de Biot. Après une introduction qualitative de l'expérience mise en place, on expose les résultats obtenus pour un grand nombre de matériaux de porosités différentes. La notion de tortuosité d'un milieu poreux est introduite théoriquement et discutée expérimentalement. This article is in two parts. The first part has to do with the theory of acoustic wave propagation in saturated porous media. Different existing methods are reviewed, and Biot's theory is critically developed in detail. In particular, the different results to which this theory leads are examined, and the conditions and geophysical problems on which the physical phenomena involved may have an appreciable effect are considered. The second part is devoted to the experimental check made by Plona (1980 of Biot's theory. After a qualitative introduction of the experimental procedure, the results obtained for many materials of different porosities are described. The concept of the tortuosity of a porous medium is introduced theoretically and discussed experimentally.

  14. The fMRI signal, slow cortical potential and consciousness.

    Science.gov (United States)

    He, Biyu J; Raichle, Marcus E

    2009-07-01

    As functional magnetic resonance imaging (fMRI) has become a driving force in cognitive neuroscience, it is crucial to understand the neural basis of the fMRI signal. Here, we discuss a novel neurophysiological correlate of the fMRI signal, the slow cortical potential (SCP), which also seems to modulate the power of higher-frequency activity, the more established neurophysiological correlate of the fMRI signal. We further propose a hypothesis for the involvement of the SCP in the emergence of consciousness, and review existing data that lend support to our proposal. This hypothesis, unlike several previous theories of consciousness, is firmly rooted in physiology and as such is entirely amenable to empirical testing.

  15. MRI studies in late-life mood disorders.

    Science.gov (United States)

    Andreescu, Carmen; Aizenstein, Howard

    2012-01-01

    There are well-established patterns of structural brain changes associated with aging. The change in brain volume with age and with the diseases of aging presents a particular challenge for MRI studies in the elderly. Structural MRI is important for studies in normal aging, late-life depression, dementia, Alzheimer disease and other cognitive disorders to examine how age-associated changes in neuroanatomy are associated with specific age-related changes in brain function. Functional MRI has been a major advance for the fields of cognitive and affective neuroscience by allowing investigators to test theories of the underlying neural pathways controlling cognitive and emotional processes. In this chapter, we will review the contribution of MRI studies to late-life mood and anxiety disorders: major depression, bipolar disorder and anxiety disorders in late-life.

  16. MRI for clinically suspected pediatric appendicitis: an implemented program

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Michael M.; Gustas, Cristy N.; Choudhary, Arabinda K.; Methratta, Sosamma T.; Hulse, Michael A.; Eggli, Kathleen D.; Boal, Danielle K.B. [Penn State Milton S. Hershey Medical Center, Department of Radiology, Mail Code H066, 500 University Drive, P.O. Box 850, Hershey, PA (United States); Geeting, Glenn [Penn State Milton S. Hershey Medical Center, Department of Emergency Medicine, Hershey, PA (United States)

    2012-09-15

    Emergent MRI is now a viable alternative to CT for evaluating appendicitis while avoiding the detrimental effects of ionizing radiation. However, primary employment of MRI in the setting of clinically suspected pediatric appendicitis has remained significantly underutilized. To describe our institution's development and the results of a fully implemented clinical program using MRI as the primary imaging evaluation for children with suspected appendicitis. A four-sequence MRI protocol consisting of coronal and axial single-shot turbo spin-echo (SS-TSE) T2, coronal spectral adiabatic inversion recovery (SPAIR), and axial SS-TSE T2 with fat saturation was performed on 208 children, ages 3 to 17 years, with clinically suspected appendicitis. No intravenous or oral contrast material was administered. No sedation was administered. Data collection includes two separate areas: time parameter analysis and MRI diagnostic results. Diagnostic accuracy of MRI for pediatric appendicitis indicated a sensitivity of 97.6% (CI: 87.1-99.9%), specificity 97.0% (CI: 93.2-99.0%), positive predictive value 88.9% (CI: 76.0-96.3%), and negative predictive value 99.4% (CI: 96.6-99.9%). Time parameter analysis indicated clinical feasibility, with time requested to first sequence obtained mean of 78.7 +/- 52.5 min, median 65 min; first-to-last sequence time stamp mean 14.2 +/- 8.8 min, median 12 min; last sequence to report mean 57.4 +/- 35.2 min, median 46 min. Mean age was 11.2 +/- 3.6 years old. Girls represented 57% of patients. MRI is an effective and efficient method of imaging children with clinically suspected appendicitis. Using an expedited four-sequence protocol, sensitivity and specificity are comparable to CT while avoiding the detrimental effects of ionizing radiation. (orig.)

  17. Long-Term MRI Findings in Operated Rotator Cuff Tear

    Energy Technology Data Exchange (ETDEWEB)

    Kyroelae, K.; Niemitukia, L.; Jaroma, H.; Vaeaetaeinen, U. [Kuopio Univ. Hospital (Finland). Dept. of Orthopaedics and Traumatology

    2004-08-01

    Purpose: To describe magnetic resonance imaging (MRI) findings at long-term follow-up after rotator cuff (RC) tear using standard MRI sequences without fat saturation. Material and Methods: Twenty-eight patients aged 55.8{+-}7.6 underwent MRI examination 4.6{+-}2.1 years after surgery for RC tear. Standard sequences in oblique coronal, oblique sagittal, and axial planes were obtained. The RC, including re-tears and tendon degeneration, was independently evaluated by two observers. Thickness of the supraspinatus tendon and narrowing of the subacromial space were measured. The clinical outcome was evaluated with the Constant score and compared with the MRI findings. Results: The RC tear was traumatic in 18 (64%) patients and degenerative in 10 (36%). At follow-up, 11 (39%) had normal RC tendons with good clinical outcome. Four (14%) patients had painful tendinosis without RC tear. A full-thickness RC tear was found in 7 (25%) patients and a partial tear in 6 (21%). In one patient with a full-thickness tear, and in two with partial tear, tendinosis was found in another of the RC tendons. The subacromial space was narrowed in 13 (46%) of the patients. A narrowing of the subacromial space correlated with re-tear (P<0.05). Conclusions: The RC may be evaluated with standard MRI sequences without fat saturation at long-term follow-up. A normal appearance of the RC is correlated with good clinical outcome, while re-tear and tendinosis are associated with pain.

  18. Getting an MRI (For Kids)

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    Full Text Available ... Cliques Make Kids Feel Left Out Getting an MRI (Video) KidsHealth > For Kids > Getting an MRI (Video) Print A A A en español Obtención de una resonancia magnética, RM (video) An MRI (magnetic resonance imaging) scan creates detailed pictures of ...

  19. Magnetic Resonance Imaging (MRI) -- Head

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    Full Text Available ... top of page What are the benefits vs. risks? Benefits MRI is a noninvasive imaging technique that does not involve exposure to ionizing radiation. MRI can help physicians evaluate the structures of the brain and can also provide functional information (fMRI) in selected cases. MR images of the ...

  20. Getting an MRI (For Kids)

    Medline Plus

    Full Text Available ... Go to School? Breast Cancer Getting an MRI (Video) KidsHealth > For Kids > Getting an MRI (Video) Print A A A en español Obtención de una resonancia magnética, RM (video) An MRI (magnetic resonance imaging) scan creates detailed ...

  1. MRI of the Chest

    Medline Plus

    Full Text Available ... have allergies of any kind, such as an allergy to iodine or x-ray contrast material, drugs, food, or the environment, or if you have asthma. The contrast material most commonly used for an MRI exam contains a ... patients with iodine contrast allergy. It is far less common for a patient ...

  2. MRI of the Chest

    Medline Plus

    Full Text Available ... come. The MR scanner captures this energy and creates a picture of the tissues scanned based on this information. The magnetic field is produced by passing an electric current through wire coils in most MRI units. Other coils, located in the machine and in some cases, placed around the part ...

  3. MRI in suspected appendicitis

    NARCIS (Netherlands)

    Leeuwenburgh, M.M.N.

    2014-01-01

    Dit proefschrift richt zich op de optimalisatie van beeldvormende diagnostiek bij patiënten met een klinische verdenking op appendicitis, waarbij het gebruik van ‘magnetic resonance imaging’ (MRI) wordt verkend. Het proefschrift omvat de resultaten van de OPTIMAP-studie (OPTimisation of IMaging

  4. MRI of the Chest

    Medline Plus

    Full Text Available ... MRI. If you have a history of kidney disease or liver transplant, it will be necessary to perform a blood test to determine whether the kidneys are functioning ... and vascular disease, heart valve abnormalities, bone and other soft tissue ...

  5. MRI of the Chest

    Medline Plus

    Full Text Available ... with the magnetic field of the MRI unit, metal and electronic items are not allowed in the exam room. ... into the scanning room also need to remove metal objects and notify the technologist of any medical or electronic devices they may have. top of page What ...

  6. MRI of the Chest

    Medline Plus

    Full Text Available ... exam time. top of page What will I experience during and after the procedure? Most MRI exams ... areas. Outside links: For the convenience of our users, RadiologyInfo .org provides links to relevant websites. RadiologyInfo. ...

  7. MRI in decompression illness

    Energy Technology Data Exchange (ETDEWEB)

    Hierholzer, J.; Stroszczynski, C.; Hosten, N.; Felix, R. [Dept. of Radiology, Charite Campus Virchow-Klinikum, Humboldt Univ. Berlin (Germany); Tempka, A. [Dept. of Traumatology, Charite Campus Virchow-Klinikum, Humboldt Univ. Berlin (Germany); Amodio, F. [Dept. of Radiology, Univ. Federico II di Napoli, Naples (Italy); Haas, J. [Dept. of Neurology, Juedisches Krankenhaus Berlin, Berlin (Germany)

    2000-05-01

    We report a case of decompression illness in which the patient developed paraparesis during scuba diving after rapid ascent. MRI of the spine revealed a focal intramedullary lesion consistent with the symptoms. The pathophysiological and radiological aspects of spinal decompression illness are discussed. (orig.)

  8. MRI of the Chest

    Medline Plus

    Full Text Available ... data suggest that it is safe to continue breastfeeding after receiving intravenous contrast. For further information please consult the ACR Manual on Contrast Media and its references. top of page What are the limitations of MRI of the Chest? High-quality images are assured only if you are able ...

  9. MRI of the Chest

    Medline Plus

    Full Text Available ... sedation or anesthesia. Alternatively, certain pediatric facilities have child life personnel who can work with younger children to help avoid the need for sedation or anesthesia. They prepare the children ... play the noises that the child might hear during the MRI exam, answer any ...

  10. MRI of the Chest

    Medline Plus

    Full Text Available ... it difficult to lie still during imaging. A person who is very large may not fit into the opening of certain types of MRI machines. The presence of an implant or other metallic object sometimes makes it difficult to obtain clear images due to ...

  11. MRI of the Chest

    Medline Plus

    Full Text Available ... devices or metal in your body. Guidelines about eating and drinking before your exam vary between facilities. Unless you ... fitting and has no metal fasteners. Guidelines about eating and drinking before an MRI exam vary with the specific ...

  12. MRI of the Chest

    Medline Plus

    Full Text Available ... patients with iodine contrast allergy. It is far less common for a patient to have an allergy to ... The contrast material used in MRI exams is less likely to produce an allergic reaction than the iodine-based contrast materials used for ...

  13. MRI and Anesthesia & Sedation

    Directory of Open Access Journals (Sweden)

    Asim Esen

    2017-08-01

    Full Text Available In 1945 Broch & Purcell described as Nuclear Magnetic Resonance. It wasused for chemical and biochemical analyses for long years. It was widelyused in medical applications after Lauterbur et al. ‘s study in 1973 (1.The primary screening method for breast cancer is mammography asknown. It is the only method that positively affects survival. But itssensitivity and specificity is not 100% and it can be an inadequate methodat some ages. Studies showed that: MRI imaging added mammographyincreased success rates but increased false positivity rates can cause someunnecessary invasive procedures. Although these breast MRI is widely usedfor screening, diagnosis and staging (2.More than 80 million MRI is worldwide applied yearly. Claustrophobia ratesare between 1-15% and more than 2 million breast MRI application isinterrupted for the necessitation of sedation (3. Melendez et al. noticedthat rate around 30%. Also 3-5% of these cases were interrupted due tothe sedation necessitation. Anxiety and claustrophobia can cause sequencerepeating, procedure cancellation and important time and labor loss.

  14. MRI of the Chest

    Medline Plus

    Full Text Available ... complete an MRI exam without moving. Whether a child requires sedation depends on the child's age, intellectual development and the type of exam. ... should be available during the exam for your child's safety. You will be given special instructions for ...

  15. MRI of the Chest

    Medline Plus

    Full Text Available ... of which shows a thin slice of the body. The images can then be studied from different angles by ... bear denotes child-specific content. Related Articles and Media MR ... Images related to Magnetic Resonance Imaging (MRI) - Chest Sponsored ...

  16. MRI of the Chest

    Medline Plus

    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will be necessary to perform a blood test to determine whether the kidneys are ... including cancer, heart and vascular disease, heart valve abnormalities, bone ...

  17. MRI of the Chest

    Medline Plus

    Full Text Available ... imaging (MRI) of the chest uses a powerful magnetic field, radio waves and a computer to produce detailed ... whether there’s a possibility you are pregnant. The magnetic field is not harmful, but it may cause some ...

  18. A new experimental method to determine the saturation voltage of a small-geometry MOSFET

    Science.gov (United States)

    Jang, Wen-Yueh; Wu, Chung-Yu; Wu, Hong-Jen

    1988-09-01

    A new extraction method which determines the saturation voltage of a small-geometry MOSFET directly from the measured data is proposed and investigated. In this method, a special function G is formed and the drain-source saturation voltage is identified as the voltage of the peak point in a plot of G vs the drain-source voltage. Since the method is based on a general device theory, it is virtually independent of any device model and quite versatile and applicable for all MOSFETs. In addition, no given device parameters or iterations are required in the method. To verify the new method, SPICE MOS models are used as a calculation example. Moreover, the method is also applied to various fabricated MOSFETs to determine the saturation voltage. It is found that the saturation voltage can be definitely determined without ambiguity and the determined saturation voltage is quite close to that from the optimal extractions. Thus the method can be incorporated into the parameter extraction and the device modeling for small-geometry MOSFETs.

  19. MRI of the cardiomyopathies

    Energy Technology Data Exchange (ETDEWEB)

    Di Cesare, Ernesto E-mail: ernesto.dicesare@cc.univaq.it

    2001-06-01

    We examined the potentialities of Magnetic resonance imaging (MRI) in the evaluation of the main cardiomyopathies: hypertrophic, dilated, restrictive and arrhythmogenic right ventricular. The hypertrophic cardiomyopathy is generally adequately investigated by echocardiography, that well defines the myocardial thickening and the obstruction of the left ventricular output. However, by echocardiography we still have difficulties in the evaluation of the apex of the left ventricle and the right ventricle involvement. MRI provides a complete evaluation of the heart with a clear evidence also of the echocardiographic dark zones by means of a clear evidence of the apex of the right ventricle. The dilated form is also well investigated by MRI that provides a clear evaluation of the volumes, mass and ejection fraction by means of the 3D analysis including conditions of the ventricular remodelling. Moreover, this technique helps in the differential diagnosis of acute myocarditis. In the acute phase of myocarditis (first 2 weeks), in fact, the myocardium produces high signal intensity on the T2 weighted sequences due to the presence of oedema. The third form of cardiomyopathy is the restrictive one, characterised by reduced diastolic filling and diastolic volume, normality of the systolic function and parietal thickness, interstitial fibrosis and enlargement of both atria. The mean potentiality of MRI is related to the differential diagnosis with constrictive pericarditis. Only in the former, the pericardium appears irregularly thickened with areas exceeding 4 mm of pericardial thickness. Finally, the right ventricular arrhythmogenic cardiomyopathy represents the main indication to MRI evaluation. With this imaging modality we are can obtain a clear morpho-functional evaluation of the right ventricle and distinguish the intramyocardial adipose substitution characterised by areas of high signal in the myocardium.

  20. PLD-grown thin film saturable absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Tellkamp, Friedjof

    2012-11-01

    The subject of this thesis is the preparation and characterization of thin films made of oxidic dielectrics which may find their application as saturable absorber in passively Q-switched lasers. The solely process applied for fabrication of the thin films was the pulsed laser deposition (PLD) which stands out against other processes by its flexibility considering the composition of the systems to be investigated. Within the scope of this thesis the applied saturable absorbers can be divided into two fundamentally different kinds of functional principles: On the one hand, saturable absorption can be achieved by ions embedded in a host medium. Most commonly applied bulk crystals are certain garnets like YAG (Y{sub 3}Al{sub 5}O{sub 12}) or the spinel forsterite (Mg{sub 2}SiO{sub 4}), in each case with chromium as dopant. Either of these media was investigated in terms of their behavior as PLD-grown saturable absorber. Moreover, experiments with Mg{sub 2}GeO{sub 4}, Ca{sub 2}GeO{sub 4}, Sc{sub 2}O{sub 3}, and further garnets like YSAG or GSGG took place. The absorption coefficients of the grown films of Cr{sup 4+}:YAG were determined by spectroscopic investigations to be one to two orders of magnitude higher compared to commercially available saturable absorbers. For the first time, passive Q-switching of a Nd:YAG laser at 1064 nm with Cr{sup 4+}:YAG thin films could be realized as well as with Cr:Sc{sub 2}O{sub 3} thin films. On the other hand, the desirable effect of saturable absorption can also be generated by quantum well structures. For this purpose, several layer system like YAG/LuAG, Cu{sub 2}O/MgO, and ZnO/corumdum were investigated. It turned out that layer systems with indium oxide (In{sub 2}O{sub 3}) did not only grew in an excellent way but also showed up a behavior regarding their photo luminescence which cannot be explained by classical considerations. The observed luminescence at roughly 3 eV (410 nm) was assumed to be of excitonic nature and its

  1. Trans Fat Now Listed With Saturated Fat and Cholesterol

    Science.gov (United States)

    ... Trans Fat Now Listed With Saturated Fat and Cholesterol Share Tweet Linkedin Pin it More sharing options ... I Do About Saturated Fat, Trans Fat, and Cholesterol? When comparing foods, look at the Nutrition Facts ...

  2. Calcium phosphate saturation in the western Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.; Reddy, C.V.G.

    Temperature, inorganic phosphate concentration and pH seem to be the major factors influencing the degree of saturation of calcium phosphate in sea water. Two water regions can be demarcated in the study area based on the saturation patterns...

  3. Nonmonotone Saturation Profiles for Hydrostatic Equilibrium in Homogeneous Porous Media

    NARCIS (Netherlands)

    Hilfer, R.; Doster, F.; Zegeling, P.A.|info:eu-repo/dai/nl/073634433

    2012-01-01

    Nonmonotonic saturation profiles (saturation overshoot) occur as travelling waves in gravity driven fingering. They seem important for preferential flow mechanisms and have found much attention recently. Here, we predict them even for hydrostatic equilibrium when all velocities vanish. We suggest

  4. Heavy Flavor Production in DGLAP improved Saturation Model

    CERN Document Server

    Sapeta, S

    2007-01-01

    The saturation model with DGLAP evolution is shown to give good description of the production of the charm and beauty quarks in deep inelastic scattering. The modifications of saturation properties caused by the presence of heavy quarks are also discussed.

  5. Silica fractal atomic clusters saturated with OH

    CERN Document Server

    Olivi-Tran, N

    2003-01-01

    We constructed regular fractal SiOH atomic clusters which pending bonds are saturated with OH molecules. We calculated the binding energies of these clusters as well as for sp sup 2 hybridization as for sp sup 3 hybridizations. The result are the following: for the two hybridizations, the total binding energies have a linear dependence on the size of the fractal cluster, which comes directly from the scaling law of the fractal characteristic of the building of the cluster. We related by a scaling law, the number of electronic bonds and the total bonding energy.

  6. Flip-angle based ratiometric approach for pulsed CEST-MRI pH imaging

    Science.gov (United States)

    Arena, Francesca; Irrera, Pietro; Consolino, Lorena; Colombo Serra, Sonia; Zaiss, Moritz; Longo, Dario Livio

    2018-02-01

    Several molecules have been exploited for developing MRI pH sensors based on the chemical exchange saturation transfer (CEST) technique. A ratiometric approach, based on the saturation of two exchanging pools at the same saturation power, or by varying the saturation power levels on the same pool, is usually needed to rule out the concentration term from the pH measurement. However, all these methods have been demonstrated by using a continuous wave saturation scheme that limits its translation to clinical scanners. This study shows a new ratiometric CEST-MRI pH-mapping approach based on a pulsed CEST saturation scheme for a radiographic contrast agent (iodixanol) possessing a single chemical exchange site. This approach is based on the ratio of the CEST contrast effects at two different flip angles combinations (180°/360° and 180°/720°), keeping constant the mean irradiation RF power (Bavg power). The proposed ratiometric approach index is concentration independent and it showed good pH sensitivity and accuracy in the physiological range between 6.0 and 7.4.

  7. Inheritance of reduced saturated fatty acid content in sunflower oil

    OpenAIRE

    Vick Brady A.; Jan C.C.; Miller Jerry F.

    2002-01-01

    In recent years, consumers have become concerned with reducing the saturated fat content of their diet. Studies have indicated that high levels of saturated fat consumption are correlated with increased risk of coronary heart disease. The total saturated fat content of oil from current sunflower hybrids averages about 130 g kg-1. To identify sunflower germplasm with reduced saturated fatty acid composition, a total of 884 cultivated sunflower accessions from the USDA-ARS North Central Regiona...

  8. Brain MRI in Parkinson's disease.

    Science.gov (United States)

    Meijer, Frederick J A; Goraj, Bozena

    2014-06-01

    In this review article, conventional brain MRI and advanced MRI techniques in Parkinson`s disease (PD) are discussed, with emphasis on clinical relevance. Conventional brain MRI sequences generally demonstrate limited abnormalities specific for PD and in clinical practice brain MRI is mainly used to exclude other pathology. Possibly, brain MRI at higher magnetic field strengths could provide new diagnostic markers. In recent years, new imaging techniques such as susceptibility weighted imaging (SWI), diffusion (tensor) MRI, magnetization transfer imaging (MTI), and functional MRI (f-MRI) have been applied to patient cohorts with PD to improve understanding of pathophysiologic changes, including functional connectivity. These advanced MRI techniques hold promise to provide additional diagnostic markers for early stage PD, as demonstrated by diffusional changes in the orbital-frontal region in the pre-motor phase of PD. Whether these advanced MRI techniques provide new diagnostic markers for early stage PD, remains a debate. Standardization of scanning protocols and post-processing methods, and validation of diagnostic criteria is crucial for these advanced MRI techniques. For this, well designed prospective clinical cohort studies are needed.

  9. Low-field MRI can be more sensitive than high-field MRI

    Science.gov (United States)

    Coffey, Aaron M.; Truong, Milton L.; Chekmenev, Eduard Y.

    2013-12-01

    MRI signal-to-noise ratio (SNR) is the key factor for image quality. Conventionally, SNR is proportional to nuclear spin polarization, which scales linearly with magnetic field strength. Yet ever-stronger magnets present numerous technical and financial limitations. Low-field MRI can mitigate these constraints with equivalent SNR from non-equilibrium ‘hyperpolarization' schemes, which increase polarization by orders of magnitude independently of the magnetic field. Here, theory and experimental validation demonstrate that combination of field independent polarization (e.g. hyperpolarization) with frequency optimized MRI detection coils (i.e. multi-turn coils using the maximum allowed conductor length) results in low-field MRI sensitivity approaching and even rivaling that of high-field MRI. Four read-out frequencies were tested using samples with identical numbers of 1H and 13C spins. Experimental SNRs at 0.0475 T were ∼40% of those obtained at 4.7 T. Conservatively, theoretical SNRs at 0.0475 T 1.13-fold higher than those at 4.7 T were possible despite an ∼100-fold lower detection frequency, indicating feasibility of high-sensitivity MRI without technically challenging, expensive high-field magnets. The data at 4.7 T and 0.0475 T was obtained from different spectrometers with different RF probes. The SNR comparison between the two field strengths accounted for many differences in parameters such as system noise figures and variations in the probe detection coils including Q factors and coil diameters.

  10. Test of Scintillometer Saturation Correction Methods Using Field Experimental Data

    NARCIS (Netherlands)

    Kleissl, J.; Hartogensis, O.K.; Gomez, J.D.

    2010-01-01

    Saturation of large aperture scintillometer (LAS) signals can result in sensible heat flux measurements that are biased low. A field study with LASs of different aperture sizes and path lengths was performed to investigate the onset of, and corrections for, signal saturation. Saturation already

  11. A demonstration experiment for studying the properties of saturated vapor

    Science.gov (United States)

    Grebenev, Igor V.; Lebedeva, Olga V.; Polushkina, Svetlana V.

    2017-11-01

    The paper proposes an important demonstration experiment that can be used at secondary schools in physics. The described experiment helps students learn the main concepts of the topic ‘saturated vapor’, namely, evaporation, condensation, dynamic equilibrium, saturation vapor, partial pressure, and the dependence of saturated vapor pressure on temperature.

  12. SITE-SCALE SATURATED ZONE TRANSPORT

    Energy Technology Data Exchange (ETDEWEB)

    S. KELLER

    2004-11-03

    This work provides a site-scale transport model for calculating radionuclide transport in the saturated zone (SZ) at Yucca Mountain, for use in the abstractions model in support of ''Total System Performance Assessment for License Application'' (TSPA-LA). The purpose of this model report is to provide documentation for the components of the site-scale SZ transport model in accordance with administrative procedure AP-SIII.10Q, Models. The initial documentation of this model report was conducted under the ''Technical Work Plan For: Saturated Zone Flow and Transport Modeling and Testing'' (BSC 2003 [DIRS 163965]). The model report has been revised in accordance with the ''Technical Work Plan For: Natural System--Saturated Zone Analysis and Model Report Integration'', Section 2.1.1.4 (BSC 2004 [DIRS 171421]) to incorporate Regulatory Integration Team comments. All activities listed in the technical work plan that are appropriate to the transport model are documented in this report and are described in Section 2.1.1.4 (BSC 2004 [DIRS 171421]). This report documents: (1) the advection-dispersion transport model including matrix diffusion (Sections 6.3 and 6.4); (2) a description and validation of the transport model (Sections 6.3 and 7); (3) the numerical methods for simulating radionuclide transport (Section 6.4); (4) the parameters (sorption coefficient, Kd ) and their uncertainty distributions used for modeling radionuclide sorption (Appendices A and C); (5) the parameters used for modeling colloid-facilitated radionuclide transport (Table 4-1, Section 6.4.2.6, and Appendix B); and (6) alternative conceptual models and their dispositions (Section 6.6). The intended use of this model is to simulate transport in saturated fractured porous rock (double porosity) and alluvium. The particle-tracking method of simulating radionuclide transport is incorporated in the finite-volume heat and mass transfer numerical

  13. A new contrast in MR mammography by means of chemical exchange saturation transfer (CEST) imaging at 3 Tesla: preliminary results.

    Science.gov (United States)

    Schmitt, B; Zamecnik, P; Zaiss, M; Rerich, E; Schuster, L; Bachert, P; Schlemmer, H P

    2011-11-01

    To evaluate the feasibility to detect and delineate malignant breast lesions in human patients by chemical exchange saturation transfer (CEST) as an MR imaging technique without the need for contrast agent administration. Six female patients referred for pre-surgical staging due to histologically confirmed breast cancer were examined with MR at 3 T. The routine breast protocol included T (2w), STIR, T (1w)-DCE and contrast-enhanced T (1w) imaging with SPAIR fat suppression. For CEST imaging, a 3D RF-spoiled gradient echo (GRE) sequence with an optimized saturation pulse train was applied. To assess the diagnostic value of the technique, CEST effects observed between frequency offsets of 1.2 to 1.8 ppm from the bulk water resonance were compared to pharmacokinetic parameter maps (k (ep)) obtained by DCE-MRI. In 3 of 6 patients, regions with high CEST signal intensity correlated well with tumor areas as determined by DCE-MRI. Analysis of signal intensities from ROIs in tumor, fibroglandular, adipose, and muscle tissue revealed significantly higher CEST values in tumor tissue compared to fibroglandular tissue. The detection of lesions was equally well possible with DCE-MRI and CEST-MRI. In the three other patients, the tumor regions could not be delineated based on the CEST image due to artifacts, which were most likely caused by a high content of fat tissue within the ROIs. The results of this initial feasibility study indicate a significant potential of CEST-MRI to discriminate cancer from fibroglandular tissue in the human breast by a CEST contrast generated by endogenous solute molecules. © Georg Thieme Verlag KG Stuttgart · New York.

  14. MRI of the shoulder

    Energy Technology Data Exchange (ETDEWEB)

    Vahlensieck, M.

    2000-02-01

    Shoulder imaging is one of the major applications in musculoskeletal MRI. In order to analyze the images it is important to keep informed about anatomical and pathological findings and publications. In this article MRI technique, anatomy and pathology is reviewed. Technical considerations about MR sequences and examination strategy are only shortly discussed with emphasis on turbo spin echo and short T1 inversion recovery imaging. Basic anatomy as well as recent findings, including macroscopic aspects of the supraspinatus fat pad, composition of the supraspinatus muscle belly, and variability of the glenohumeral ligaments or coracoid ligament, are presented. Basic pathological conditions are described in detail, e. g. instability particularly problems in differentiating the various subtypes of labral pathology. Rotator cuff diseases are elucidated with emphasis on some rarer entities such as subscapularis calcifying tendinitis, coracoid impingement, chronic bursitis producing the double-line sign, prominent coraco-acromial ligament and the impingement due to an inflamed os acromiale. (orig.)

  15. Introduction to MRI Physics.

    Science.gov (United States)

    Martinez, Gary V

    2018-01-01

    Magnetic resonance imaging (MRI) is an imaging technique derived from radiofrequency (RF) signals of proton that are magnetized by a strong magnetic field. These protons typically originate from water, fat, or metabolites. The application of RF pulses is used to excite the magnetization, whereas pulsed magnetic field gradients are used to provide spatial localization. This chapter describes the fundamental principles giving rise to MR images. Furthermore, the connection between relaxation and image contrast is discussed.

  16. Energy dependent saturable and reverse saturable absorption in cube-like polyaniline/polymethyl methacrylate film

    Energy Technology Data Exchange (ETDEWEB)

    Thekkayil, Remyamol [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, C.V. Raman Avenue, Bangalore 560 080 (India); Gopinath, Pramod [Department of Physics, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547 (India); John, Honey, E-mail: honey@iist.ac.in [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547 (India)

    2014-08-01

    Solid films of cube-like polyaniline synthesized by inverse microemulsion polymerization method have been fabricated in a transparent PMMA host by an in situ free radical polymerization technique, and are characterized by spectroscopic and microscopic techniques. The nonlinear optical properties are studied by open aperture Z-scan technique employing 5 ns (532 nm) and 100 fs (800 nm) laser pulses. At the relatively lower laser pulse energy of 5 μJ, the film shows saturable absorption both in the nanosecond and femtosecond excitation domains. An interesting switchover from saturable absorption to reverse saturable absorption is observed at 532 nm when the energy of the nanosecond laser pulses is increased. The nonlinear absorption coefficient increases with increase in polyaniline concentration, with low optical limiting threshold, as required for a good optical limiter. - Highlights: • Synthesized cube-like polyaniline nanostructures. • Fabricated polyaniline/PMMA nanocomposite films. • At 5 μJ energy, saturable absorption is observed both at ns and fs regime. • Switchover from SA to RSA is observed as energy of laser beam increases. • Film (0.1 wt % polyaniline) shows high β{sub eff} (230 cm GW{sup −1}) and low limiting threshold at 150 μJ.

  17. Femoral venous oxygen saturation and central venous oxygen saturation in critically ill patients.

    Science.gov (United States)

    Zhang, Xiaohong; Wang, Jiandong; Dong, Yun; Chen, Youdai

    2015-08-01

    To investigate the relationship between central venous oxygen saturation (ScvO(2)) and femoral venous oxygen saturation (SfvO(2)) in a large group of critically ill patients. Observational study. A group of unselected critically ill patients with central line placed into superior vena cava were included. A 26-bed intensive care unit in a tertiary referral hospital. None. Venous blood samples of superior vena cava and femoral vein were collected within an interval of 5 to 15 minutes and analyzed with blood gas/electrolyte analyzer immediately. Although SfvO(2) was significantly correlated with ScvO(2) (r = 0.493, P 731 pairs of blood samples collected from 357 patients. The fit line of scatter diagram ScvO(2) vs SfvO(2) had a large intercept (48.68%) and a low slope (0.2978); ScvO(2) was still around 50% while SfvO(2) was nearing 0%. The distribution of blood flow, measured with Doppler ultrasound, had a similar trend in 237 patients and 412 measurements. The ratio of femoral artery flow over common carotid artery flow varied widely (from 0 to 7.13). Blood flow was not distributed in a fixed ratio to the superior vena cava-drained organs and tissues. Central venous oxygen saturation was not representative of the whole systemic circulation in critically ill patients. Central venous oxygen saturation alone might be misleading in goal-directed therapy. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Conceptual design of safety injection tanks using saturated water

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hae Min; Jeong, Yong Hoon; Chang, Won Joon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2009-07-01

    Safety Injection Tanks (SITs) which is the one of Safety Injection System (SIS) play an important role in mitigating the Loss of Coolant Accidents (LOCAs) in Pressurized Water Reactor (PWR). APR1400 has the advanced 4 SITs directly connected to a reactor vessel. We expect the capacity of the SITs is getting more important since the coolant from SITs equipped with a FD during LBLOCA can replace the injection from low pressure safety injection pumps (LPSIPs). In designing a larger capacity SIT, we may have three problems; the excessively large volume for pressurized N{sub 2} gas, which is about 1/3 of the total volume, the difficulties controlling injection flowrate and the solubility of the non-condensable N{sub 2} gas in the coolant. In here, there is the contradiction which is 'there must be nitrogen gas for pressurization but there must not be nitrogen gas for more coolant.' For this problem, the axiomatic design (AD) theory enabled us to define or regularize the intrinsic problem which is termed the coupling and the contradiction. TRIZ facilitates creating solutions on the contradiction. This study proposes a conceptual design of SITs which are pressurized by steam from the saturated water as a demonstration of the conceptual design framework, AD theory and TRIZ. The purpose of this conceptual design is to increase coolant volume and to reduce N{sub 2} gas volume in SITs. In order to investigate the feasibility of the proposed design, we derived an analytical model to find the heat loss of saturated water and thermo-hydraulic safety analysis using MARS3.1. To confirm the safety and integrity of core, we conducted LBLOCA simulation to find peak cladding temperature (PCT) of design using the proposed SITs comparing with the conventional SITs. From the analysis results, the benefits of the new SIT design were observed in terms of the PCT, the quenching time and the size. And the new SIT design may enable emergency core cooling water to be injected

  19. Clinical experience with MRI in head trauma cases

    Energy Technology Data Exchange (ETDEWEB)

    Yamagami, Tatsuhito; Goto, Yasunobu; Kinuta, Yuji; Tashiro, Yuzuru; Nishihara, Kiyoshi; Hashimoto, Kenji; Minamikawa, Jun; Kikuchi, Haruhiko; Imataka, Kiyoharu.

    1988-12-01

    The ability to identify lesions after head trauma using magnetic resonance imaging (MRI) was tested in 199 cases. A resistive-type MRI scanner operating at a field of 0.2 Tesla was utilized in inversion-recovery (IR) and saturation-recovery (SR) radiofrequency-pulse sequences. Of the total number of cases, 54 were examined within 4 days after injury. An intracranial hematoma was removed in 47 cases. The MRI findings were normal in the cases of cerebral concussion, even in the presence of skull fracture. High intensity areas were seen in the SR images in 12 cases which were normal on X-ray CT. Both acute and subacute non-hemorrhagic contusion sites were visible as low intensity areas on the T/sub 1/-weighted images and as high intensity areas on the SR images. Acute hemorrhagic contusion sites were visible as isointense and low intensity areas in the T/sub 1/-weighted images and as high intensity areas in the SR images. Subacute sites appeared as high intensity areas in the T/sub 1/-weighted, SR, and T/sub 2/-weighted images. Direct coronal and sagittal views were adequate for the recognition of the three-dimensional brain structure. MRI was useful in the identification of brain contusion, in postoperative follow-ups, and in the detection of complications in the chronic stage. In the follow-up of 48 brain contusion cases, 13 cases showed normalized MRI findings and 9 cases showed improved findings. The recovery of cerebral function in these cases was good. The lesions demonstrated by MRI were considered to be contusional hematoma, petechiae, brain edema, shear injury, and non-hemorrhagic contusion. When they persist, such lesions are thought to change into such conditions as scar, gliosis, porencephaly, and brain atrophy.

  20. A new MRI grading system for chondromalacia patellae.

    Science.gov (United States)

    Özgen, Ali; Taşdelen, Neslihan; Fırat, Zeynep

    2017-04-01

    Background Chondromalacia patellae is a very common disorder. Although magnetic resonance imaging (MRI) is widely used to investigate patellar cartilage lesions, there is no descriptive MRI-based grading system for chondromalacia patellae. Purpose To propose a new MRI grading system for chondromalacia patellae with corresponding high resolution images which might be useful in precisely reporting and comparing knee examinations in routine daily practice and used in predicting natural course and clinical outcome of the patellar cartilage lesions. Material and Methods High resolution fat-saturated proton density (FS PD) images in the axial plane with corresponding T2 mapping images were reviewed. A detailed MRI grading system covering the deficiencies of the existing gradings has been set and presented on these images. Two experienced observers blinded to clinical data examined 44 knee MR images and evaluated patellar cartilage changes according to the proposed grading system. Inter- and intra-rater validity testing using kappa statistics were calculated. Results A descriptive and detailed grading system with corresponding FS PD and T2 mapping images has been presented. Inter-rater agreement was 0.80 (95% confidence interval [CI], 0.71-0.89). Intra-rater agreements were 0.83 (95% CI, 0.74-0.91) for observer A and 0.79 (95% CI, 0.70-0.88) for observer B (k-values). Conclusion We present a new MRI grading system for chondromalacia patellae with corresponding images and good inter- and intra-rater agreement which might be useful in reporting and comparing knee MRI examinations in daily practice and may also have the potential for using more precisely predicting prognosis and clinical outcome of the patients.

  1. Chondrocalcinosis of the hyaline cartilage of the knee: MRI manifestations

    Energy Technology Data Exchange (ETDEWEB)

    Beltran, J.; Marty-Delfaut, E.; Bencardino, J.; Rosenberg, Z.S. [Department of Radiology, Hospital for Joint Diseases, New York, NY (United States); Steiner, G. [Department of Pathology, Hospital for Joint Diseases, New York, NY (United States); Aparisi, F. [Department of Radiology, Residencia Sanitaria ``La Fe``, Valencia (Spain); Padron, M. [Clinica San Camilo, Madrid (Spain)

    1998-07-01

    Purpose. To determine the ability of MRI to detect the presence of crystals of calcium pyrophosphate in the articular cartilage of the knee. Design and patients. The MR studies of 12 knees (11 cases) were reviewed retrospectively and correlated with radiographs (12 cases) and the findings at arthroscopy (2 cases) and surgery (1 case). A total of 72 articular surfaces were evaluated. Radiographic, surgical or arthroscopic demonstration of chondrocalcinosis was used as the gold standard. Additionally, two fragments of the knee of a patient who underwent total knee replacement and demonstrated extensive chondrocalcinosis were studied with radiography and MRI using spin-echo T1-, T2- and proton-density-weighted images as well as two- and three-dimensional fat saturation (2D and 3D Fat Sat) gradient recalled echo (GRE) and STIR sequences. Results. MRI revealed multiple hypointense foci within the articular cartilage in 34 articular surfaces, better shown on 2D and 3D GRE sequences. Radiographs showed 12 articular surfaces with chondrocalcinosis. In three cases with arthroscopic or surgical correlation, MRI demonstrated more diffuse involvement of the articular cartilage than did the radiographs. The 3D Fat Sat GRE sequences were the best for demonstrating articular calcification in vitro. In no case was meniscal calcification identified with MRI. Hyperintense halos around some of the calcifications were seen on the MR images. Conclusion. MRI can depict articular cartilage calcification as hypointense foci using GRE techniques. Differential diagnosis includes loose bodies, post-surgical changes, marginal osteophytes and hemosiderin deposition. (orig.) With 4 figs., 14 refs.

  2. A sulfide-saturated lunar mantle?

    Science.gov (United States)

    Brenan, James M.; Mungall, James E.

    2017-04-01

    Although much work has been done to understand the controls on the sulfur content at sulfide saturation (SCSS) for terrestrial melt compositions, little information exists to evaluate the SCSS for the high FeO compositions typical of lunar magmas, and at the reduced conditions of the Moon's interior. Experiments were done to measure the SCSS for a model low Ti mare basalt with 20 wt% FeO at 1400oC as a function of fO2 and pressure. Synthetic lunar basalt was encapsulated along with stoichiometric FeS in capsules made from Fe-Ir alloy. The fO2 of the experiment can be estimated by the heterogeneous equilibrium: Femetal + 1 /2 O2 = FeOsilicate Variation in the metal composition, by addition of Ir, serves to change the fO2 of the experiment. Capsule compositions spanning the range Fe25Ir75 to Fe96Ir4 (at%) were synthesized by sintering of pressed powders under reducing conditions. Fe100 capsules were fabricated from pure Fe rod. For a melt with 20 wt% FeO, this range in capsule composition spans the fO2 interval of ˜IW-1 (Fe100, Fe96Ir4) to IW+2.2 (Fe25Ir75). Experiments were done over the pressure interval of 0.1 MPa to 2 GPa. Results for experiments involving Fe100capsules indicate that the SCSS decreases from ˜2000 ppm (0.1 MPa) to 700 ppm (2 GPa). Experiments done thus far at 1 GPa, involving the range of capsule compositions indicated, show a marked decrease in SCSS as the Fe content of the capsule increases (fO2 decreases). Complementary to the decrease in SCSS is a drop in the sulfur content of the coexisting sulfide melt, from ˜50 at% at ΔIW = +2.2 to ˜20 at% at ΔIW-1. In fact, both the composition of the sulfide melt and the SCSS are essentially indistinguishable for Fe96Ir4 and Fe100 compositions. Results thus far indicate that at reduced conditions and high pressure, the SCSS for high FeO lunar compositions is low, and overlaps with Apollo 11 melt inclusion data. Importantly, such low SCSS does not require Fe metal saturation, and suggests that some

  3. The Danish tax on saturated fat

    DEFF Research Database (Denmark)

    Jensen, Jørgen Dejgård; Smed, Sinne

    2013-01-01

    Denmark introduced a new tax on saturated fat in food products with effect from October 2011. The objective of this paper is to make an effect assessment of this tax for some of the product categories most significantly affected by the new tax, namely fats such as butter, butter-blends, margarine...... fat in food products has had some effects on the market for the considered products, in that the level of consumption of fats dropped by 10 – 20%. Furthermore, the analysis points at shifts in demand from high-price supermarkets towards low-price discount stores – at least for some types of oils...... and fats, a shift that seems to have been utilized by discount chains to raise the prices of butter and margarine by more than the pure tax increase. Due to the relatively short data period with the tax being active, interpretation of these findings from a long-run perspective should be done...

  4. Waltz's Theory of Theory

    DEFF Research Database (Denmark)

    Wæver, Ole

    2009-01-01

    Kenneth N. Waltz's 1979 book, Theory of International Politics, is the most influential in the history of the discipline. It worked its effects to a large extent through raising the bar for what counted as theoretical work, in effect reshaping not only realism but rivals like liberalism and refle......Kenneth N. Waltz's 1979 book, Theory of International Politics, is the most influential in the history of the discipline. It worked its effects to a large extent through raising the bar for what counted as theoretical work, in effect reshaping not only realism but rivals like liberalism...... and reflectivism. Yet, ironically, there has been little attention to Waltz's very explicit and original arguments about the nature of theory. This article explores and explicates Waltz's theory of theory. Central attention is paid to his definition of theory as ‘a picture, mentally formed' and to the radical anti......-empiricism and anti-positivism of his position. Followers and critics alike have treated Waltzian neorealism as if it was at bottom a formal proposition about cause-effect relations. The extreme case of Waltz being so victorious in the discipline, and yet being consistently mis-interpreted on the question of theory...

  5. Diffusion-weighted MRI, dynamic susceptibility contrast MRI and ultrasound perfusion quantification of denervated muscle in rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Goyault, G.; Beregi, J.P. [University Hospital, Department of Cardiovascular imaging, Cardiologic Hospital, Lille (France); Bierry, G.; Holl, N.; Dietemann, J.L.; Kremer, S. [University Hospital, Department of Neuroradiology, Strasbourg (France); Lhermitte, B. [University Hospital, Department of Pathology, Strasbourg (France)

    2012-01-15

    The purpose of this study was to assess denervated muscle perfusion using dynamic susceptibility contrast MRI (DSCMRI) and contrast-enhanced ultrasound (CEUS), and to measure denervated muscle apparent diffusion coefficient (ADC) on b1000 diffusion-weighted MRI (DWMRI) at 3 T in order to clarify whether muscle denervation leads to an increase in the extracellular extravascular space, or an increase in blood flow - or both. Axotomy of the right sciatic nerve of six white rabbits was performed at day 0. At day 9, hind limb muscles MRI and CEUS were performed to assess the consequences of denervation and both semimembranosus muscles of each rabbit were explanted for histological studies. Signal intensity on T2- and T1-weighted MRI, ADC on DWMRI, maximum signal drop (MSD) on DSCMRI and the area under the curve (AUC) on CEUS were measured over circular regions of interest (ROI), in both semimembranosus muscles. Non-parametric Wilcoxon matched-pairs tests were used to assess the mean differences between denervated and normal muscles. T2 fat-saturated (FS) MRI studies showed a strong signal in the right semimembranosus muscles compared with the left side, and gadolinium enhancement was observed on T1 FS MRI. Denervated muscles show a significant increase in ADC on DWMRI (p < 0.01) and a significant signal enhancement on DSCMR imaging (p < 0.05) and on first-pass CEUS (p < 0.05). The results of this study - based on perfusion- and diffusion-weighted images - suggest that, after denervation, both increased blood flow through muscle tissue and expansion of the extracellular water volume are present. (orig.)

  6. High Spatiotemporal Resolution Prostate MRI

    Science.gov (United States)

    2017-09-01

    AWARD NUMBER: W81XWH-15-1-0341 TITLE: High Spatiotemporal Resolution Prostate MRI PRINCIPAL INVESTIGATOR: Stephen J. Riederer, Ph.D...Resolution Prostate MRI 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-15-1-0341 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Stephen J. Riederer E-Mail...overall purpose of this project is to develop improved means using MRI for detecting prostate cancer with the potential for differentiating disease

  7. Revised conditions for MRI due to isorotation theorem

    Energy Technology Data Exchange (ETDEWEB)

    Cianfrani, Francesco [Institute for Theoretical Physics, University of Wrocław, Pl. Maksa Borna 9, Pl-50-204 Wrocław (Poland); Montani, Giovanni, E-mail: giovanni.montani@enea.it [ENEA, Fusion and Nuclear Safety Department, C.R. Frascati - Via E. Fermi, 45 (00044) Frascati (Roma) (Italy); Physics Department, “Sapienza” University of Rome, P.le Aldo Moro 5, 00185 (Roma) (Italy)

    2017-06-10

    We re-analyze the physical conditions for Magneto-rotational Instability (MRI) within a steady axisymmetric stratified disk of plasma, in order to account for the so-called isorotation theory (the spatial profile of differential angular velocity depends on the magnetic flux surface). We develop the study of linear stability around an astrophysical background configuration, following the original derivation in , but implementing the isorotation condition as the orthogonality between the background magnetic field and the angular velocity gradient. We demonstrate that a dependence on the background magnetic field direction is restored in the dispersion relation and, hence, the emergence of MRI is also influenced by field orientation.

  8. MRI assessment program. Consensus statement on clinical efficacy of MRI

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-05-01

    This consensus statement is largely based on the experience gained at the MRI units at the four hospitals which have operated scanners in the MRI program. It reflects the considered opinion of the radiologists responsible for the MRI services at those hospitals. Account has also been taken of relevant overseas data. This collection of opinion relates particularly to comparison with other imaging modalities. The specific comments will require further consideration as technical developments with MRI become available, additional experience is gained with gadolinium contrast material and additional data are obtained on the influence of MRI on patient management. MRI, at present, is used either to improve diagnostic accuracy when other tests are negative or equivocal, when there is strong clinical suspicion of disease, or to improve surgical or other management planning when the diagnosis known. In some situations (eg syringomyelia, congenital spinal disease, posterior fossa/cerebello-pontine angle tumours) it may entirely replace other tests (eg myelography, air contrast, CT) which are substantially less accurate and/or more invasive. In other situations (eg hemispheric brain tumours, lumbar disc protrusions) when other tests, such as CT, can be as accurate, MRI is not usually or initially indicated because it is currently more expensive and of limited availability. However, balanced against this is the fact that it does not expose the patient to potentially harmful ionising radiation. It is also stressed that MRI images depend on complex, widely variable and, as yet, incompletely understood parameters. There is concern that this may result in false positive diagnoses, especially where MRI is used alone as a screening test, or used as the initial test. For several reasons (availability, cost, medical and diagnostic efficacy), the specific comments on indications for MRI presented are based upon the assumption that MRI is a tertiary and complementary imaging examination

  9. A step-by-step tutorial on using the cognitive architecture ACT-R in combination with fMRI data

    NARCIS (Netherlands)

    Borst, Jelmer P.; Anderson, John R.

    The cognitive architecture ACT-R is at the same time a psychological theory and a modeling framework for constructing cognitive models that adhere to the principles of the theory. ACT-R can be used in combination with fMRI data in two different ways: (1) fMRI data can be used to evaluate and

  10. 2D MRI-induced turbulence in high β PIC simulation

    Science.gov (United States)

    Inchingolo, Giannandrea; Grismayer, Thomas; Loureiro, Nuno F.; Fonseca, Ricardo A.; Silva, Luis O.

    2017-10-01

    The magnetorotational instability (MRI) is a crucial mechanism of angular momentum transport in a variety of astrophysical scenarios, as accretion disks nearness neutron stars and black holes. The MRI has been widely studied using MHD models and simulations, in order to understand the behaviour of astrophysical fluids in a state of differential rotation. When the timescale for electron and ion collisions is longer than the inflow time in the disk, the plasma is macroscopically collisionless and MHD breaks down. This is the case of the limit of weak magnetic field, i.e., as the ratio of the ion cyclotron frequency to orbital frequency becomes small. Leveraging on the recent addition of the shearing co-rotating frames equations of motion and Maxwell's equations modules in our PIC code OSIRIS 3.0, we intend to present our recent results of the analysis of MRI in collisionless plasma. Increasing the scale of our simulations, we will show the first ab-initio PIC simulations of a 2D turbulence induced consistently during the saturation regime of the MRI. We will demonstrate the existence of a minimum scale λkink that determine the comparison of a drift-kink instability in the plasma. This instability will activate the turbulence during the saturation regime of the MRI.

  11. Moderators of the mediated effect of intentions, planning, and saturated-fat intake in obese individuals.

    Science.gov (United States)

    Soureti, Anastasia; Hurling, Robert; van Mechelen, Willem; Cobain, Mark; ChinAPaw, Mai

    2012-05-01

    The present study aimed to advance our understanding of health-related theory, that is, the alleged intention-behavior gap in an obese population. It examined the mediating effects of planning on the intention-behavior relationship and the moderated mediation effects of age, self-efficacy and intentions within this relationship. The study was conducted over a five-week period. Complete data from 571 obese participants were analyzed. The moderated mediation hypothesis was conducted using multiple-regression analysis. To test our theoretical model, intentions (Week 2), action self-efficacy (Week 2), maintenance self-efficacy (Week 5), planning (Week 5), and saturated-fat intake (Weeks 1 and 5) were measured by self-report. As hypothesized, planning mediated the intention-behavior relationship for perceived (two-item scale) and percentage-saturated-fat intake (measured by a food frequency questionnaire). Age, self-efficacy, and intention acted as moderators in the above mediation analysis. In specific, younger individuals, those with stronger intention, and people with higher levels of maintenance self-efficacy at higher levels of planning showed greater reductions in their perceived saturated-fat intake. For successful behavior change, knowledge of its mediators and moderators is needed. Future interventions targeting planning to change saturated-fat intake should be guided by people's intentions, age, and self-efficacy levels.

  12. Synchrotron radiation measurement of multiphase fluid saturations in porous media: Experimental technique and error analysis

    Science.gov (United States)

    Tuck, David M.; Bierck, Barnes R.; Jaffé, Peter R.

    1998-06-01

    Multiphase flow in porous media is an important research topic. In situ, nondestructive experimental methods for studying multiphase flow are important for improving our understanding and the theory. Rapid changes in fluid saturation, characteristic of immiscible displacement, are difficult to measure accurately using gamma rays due to practical restrictions on source strength. Our objective is to describe a synchrotron radiation technique for rapid, nondestructive saturation measurements of multiple fluids in porous media, and to present a precision and accuracy analysis of the technique. Synchrotron radiation provides a high intensity, inherently collimated photon beam of tunable energy which can yield accurate measurements of fluid saturation in just one second. Measurements were obtained with precision of ±0.01 or better for tetrachloroethylene (PCE) in a 2.5 cm thick glass-bead porous medium using a counting time of 1 s. The normal distribution was shown to provide acceptable confidence limits for PCE saturation changes. Sources of error include heat load on the monochromator, periodic movement of the source beam, and errors in stepping-motor positioning system. Hypodermic needles pushed into the medium to inject PCE changed porosity in a region approximately ±1 mm of the injection point. Improved mass balance between the known and measured PCE injection volumes was obtained when appropriate corrections were applied to calibration values near the injection point.

  13. Subcritical saturation of the magnetorotational instability through mean magnetic field generation

    Science.gov (United States)

    Xie, Jin-Han; Julien, Keith; Knobloch, Edgar

    2018-03-01

    The magnetorotational instability is widely believed to be responsible for outward angular momentum transport in astrophysical accretion discs. The efficiency of this transport depends on the amplitude of this instability in the saturated state. We employ an asymptotic expansion based on an explicit, astrophysically motivated time-scale separation between the orbital period, Alfvén crossing time and viscous or resistive dissipation time-scales, originally proposed by Knobloch and Julien, to formulate a semi-analytical description of the saturated state in an incompressible disc. In our approach a Keplerian shear flow is maintained by the central mass but the instability saturates via the generation of a mean vertical magnetic field. The theory assumes that the time-averaged angular momentum flux and the radial magnetic flux are constant and determines both self-consistently. The results predict that, depending on parameters, steady saturation may be supercritical or subcritical, and in the latter case that the upper (lower) solution branch is always stable (unstable). The angular momentum flux is always outward, consistent with the presence of accretion, and for fixed wavenumber peaks in the subcritical regime. The limit of infinite Reynolds number at large but finite magnetic Reynolds number is also discussed.

  14. Reaching saturation in patterned source vertical organic field effect transistors

    Science.gov (United States)

    Greenman, Michael; Sheleg, Gil; Keum, Chang-min; Zucker, Jonathan; Lussem, Bjorn; Tessler, Nir

    2017-05-01

    Like most of the vertical transistors, the Patterned Source Vertical Organic Field Effect Transistor (PS-VOFET) does not exhibit saturation in the output characteristics. The importance of achieving a good saturation is demonstrated in a vertical organic light emitting transistor; however, this is critical for any application requiring the transistor to act as a current source. Thereafter, a 2D simulation tool was used to explain the physical mechanisms that prevent saturation as well as to suggest ways to overcome them. We found that by isolating the source facet from the drain-source electric field, the PS-VOFET architecture exhibits saturation. The process used for fabricating such saturation-enhancing structure is then described. The new device demonstrated close to an ideal saturation with only 1% change in the drain-source current over a 10 V change in the drain-source voltage.

  15. Brain oxygen saturation assessment in neonates using T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy.

    Science.gov (United States)

    Alderliesten, Thomas; De Vis, Jill B; Lemmers, Petra Ma; Hendrikse, Jeroen; Groenendaal, Floris; van Bel, Frank; Benders, Manon Jnl; Petersen, Esben T

    2017-03-01

    Although near-infrared spectroscopy is increasingly being used to monitor cerebral oxygenation in neonates, it has a limited penetration depth. The T2-prepared Blood Imaging of Oxygen Saturation (T2-BIOS) magnetic resonance sequence provides an oxygen saturation estimate on a voxel-by-voxel basis, without needing a respiratory calibration experiment. In 15 neonates, oxygen saturation measured by T2-prepared blood imaging of oxygen saturation and near-infrared spectroscopy were compared. In addition, these measures were compared to cerebral blood flow and venous oxygen saturation in the sagittal sinus. A strong linear relation was found between the oxygen saturation measured by magnetic resonance imaging and the oxygen saturation measured by near-infrared spectroscopy ( R2 = 0.64, p infrared spectroscopy oxygen saturation, and magnetic resonance imaging measures of frontal cerebral blood flow, whole brain cerebral blood flow and venous oxygen saturation in the sagittal sinus ( R2 = 0.71, 0.50, 0.65; p infrared spectroscopy and T2-prepared blood imaging of oxygen saturation, confirming the validity of using of these techniques for determining cerebral oxygenation.

  16. Ovarian cysts on prenatal MRI

    Energy Technology Data Exchange (ETDEWEB)

    Nemec, Ursula [Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Nemec, Stefan F., E-mail: stefan.nemec@meduniwien.ac.at [Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Medical Genetics Institute, Cedars Sinai Medical Center, 8700 Beverly Boulevard, PACT Suite 400, Los Angeles, CA 90048 (United States); Bettelheim, Dieter [Department of Obstetrics and Gynaecology, Division of Prenatal Diagnosis and Therapy, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Brugger, Peter C. [Center of Anatomy and Cell Biology, Integrative Morphology Group, Medical University Vienna, Waehringerstrasse 13, A-1090 Vienna (Austria); Horcher, Ernst [Department of Pediatric Surgery, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Schoepf, Veronika [Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria); Graham, John M.; Rimoin, David L. [Medical Genetics Institute, Cedars Sinai Medical Center, 8700 Beverly Boulevard, PACT Suite 400, Los Angeles, CA 90048 (United States); Weber, Michael; Prayer, Daniela [Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria)

    2012-08-15

    Objective: Ovarian cysts are the most frequently encountered intra-abdominal masses in females in utero. They may, at times, require perinatal intervention. Using magnetic resonance imaging (MRI) as an adjunct to ultrasonography (US) in prenatal diagnosis, we sought to demonstrate the ability to visualize ovarian cysts on prenatal MRI. Materials and methods: This retrospective study included 17 fetal MRI scans from 16 female fetuses (23-37 gestational weeks) with an MRI diagnosis of ovarian cysts after suspicious US findings. A multiplanar MRI protocol was applied to image and to characterize the cysts. The US and MRI findings were compared, and the prenatal findings were compared with postnatal imaging findings or histopathology. Results: Simple ovarian cysts were found in 10/16 cases and complex cysts in 7/16 cases, including one case with both. In 11/16 (69%) cases, US and MRI diagnoses were in agreement, and, in 5/16 (31%) cases, MRI specified or expanded the US diagnosis. In 6/16 cases, postnatal US showed that the cysts spontaneously resolved or decreased in size, and in 1/16 cases, postnatal imaging confirmed a hemorrhagic cyst. In 4/16 cases, the prenatal diagnoses were confirmed by surgery/histopathology, and for the rest, postnatal correlation was not available. Conclusion: Our results illustrate the MRI visualization of ovarian cysts in utero. In most cases, MRI will confirm the US diagnosis. In certain cases, MRI may provide further diagnostic information, additional to US, which is the standard technique for diagnosis, monitoring, and treatment planning.

  17. Quantitative 1D saturation profiles on chalk by NMR

    DEFF Research Database (Denmark)

    Olsen, Dan; Topp, Simon; Stensgaard, Anders

    1996-01-01

    Quantitative one-dimensional saturation profiles showing the distribution of water and oil in chalk core samples are calculated from NMR measurements utilizing a 1D CSI spectroscopy pulse sequence. Saturation profiles may be acquired under conditions of fluid flow through the sample. Results reveal...... that strong saturation gradients exist in chalk core samples after core floods, due to capillary effects. The method is useful in analysis of corefloods, e.g., for determination of capillary pressure functions...

  18. Saturated fat -a never ending story?

    Science.gov (United States)

    Svendsen, Karianne; Arnesen, Erik; Retterstøl, Kjetil

    2017-01-01

    Science has no clear message regarding health effects of saturated fats, it seems. Different RCTs, prospective cohort studies and meta-analysis have led to contrasting conclusions. The aim of the present commentary is to discuss some possible reasons for an apparently never-ending fat controversy. They are of a purely scientific nature, which is important to recognize, but unfortunately hard to overcome. First is the placebo problem. In pharmaceutical science, evidence-based medicine is often synonymous with data on verified medical events from long-lasting double-blind randomized placebo controlled trials. In nutritional science the lack of double-blind design and lack of placebo food generate less conclusive data than those achieved in pharmaceutical science. Some scientists may apply the same type of scientific criteria used to evaluate the effects of drugs for foods. This leaves an impression of insufficient data since in this respect the fundamental criteria for evidence based medicine are not present. The next scientific problem is the energy balance equation. In contrast to pharmaceuticals, nutrients contain energy. An increased intake of one nutrient will lead to a decreased intake of another. The effect of change in only one nutrient is then difficult to isolate. Lastly, in nutritional science, generalizability is difficult compared to pharmaceutical science. Food culture interferes with lifestyle and food habits change over time. In conclusion, all available knowledge, from molecular experiments to population studies, must be taken in to account, to convert scientific data into dietary recommendations.

  19. Assaying Carcinoembryonic Antigens by Normalized Saturation Magnetization

    Science.gov (United States)

    Huang, Kai-Wen; Chieh, Jen-Jie; Shi, Jin-Cheng; Chiang, Ming-Hsien

    2015-07-01

    Biofunctionalized magnetic nanoparticles (BMNs) that provide unique advantages have been extensively used to develop immunoassay methods. However, these developed magnetic methods have been used only for specific immunoassays and not in studies of magnetic characteristics of materials. In this study, a common vibration sample magnetometer (VSM) was used for the measurement of the hysteresis loop for different carcinoembryonic antigens (CEA) concentrations ( Φ CEA) based on the synthesized BMNs with anti-CEA coating. Additionally, magnetic parameters such as magnetization ( M), remanent magnetization ( M R), saturation magnetization ( M S), and normalized parameters (Δ M R/ M R and Δ M S/ M S) were studied. Here, Δ M R and Δ M s were defined as the difference between any ΦCEA and zero Φ CEA. The parameters M, Δ M R, and Δ M S increased with Φ CEA, and Δ M S showed the largest increase. Magnetic clusters produced by the conjugation of the BMNs to CEAs showed a Δ M S greater than that of BMNs. Furthermore, the relationship between Δ M S/ M S and Φ CEA could be described by a characteristic logistic function, which was appropriate for assaying the amount of CEAs. This analytic Δ M S/ M S and the BMNs used in general magnetic immunoassays can be used for upgrading the functions of the VSM and for studying the magnetic characteristics of materials.

  20. Sensorial saturation and neonatal pain: a review.

    Science.gov (United States)

    Locatelli, Chiara; Bellieni, Carlo Valerio

    2017-08-23

    Sensorial saturation (SS) is an analgesic approach to babies' pain that includes three types of stimulations: oral sugar, massage and caregivers' voice. The aim of this review is to assess its efficacy. We performed an analysis of scientific literature from 2001 to 2017, retrieving those clinical trials where SS had been compared with other analgesic treatments during procedural pain in babies. We retrieved 14 studies. Pain sources were heel-prick in nine, eye examination and intramuscular shots in two each, and endotracheal aspiration in one. SS was the most effective treatment in all cases, except in endotracheal suctioning. No drawbacks were reported in any study using SS. SS is a safe and effective approach to neonatal pain due to heel-prick, more effective than oral sucrose or glucose in both term and preterm babies; it seems also effective in other types of acute procedural pain like eye examination or intramuscular injections, but more studies are needed to confirm these preliminary data. More studies are also needed to test SS efficacy for other procedures, and for older infants.

  1. SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION

    Energy Technology Data Exchange (ETDEWEB)

    B.W. ARNOLD

    2004-10-27

    The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ.

  2. MRI in intraspinal tuberculosis

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, R.K. (Dept. of Radiology, Sanjay Gandhi Postgraduate Inst. of Medical Sciences, Lucknow (India)); Gupta, S. (Dept. of Radiology, Sanjay Gandhi Postgraduate Inst. of Medical Sciences, Lucknow (India)); Kumar, S. (Dept. of Radiology, Sanjay Gandhi Postgraduate Inst. of Medical Sciences, Lucknow (India)); Kohli, A. (Dept. of Neurology, Sanjay Gandhi Postgraduate Inst. of Medical Sciences, Lucknow (India)); Misra, U.K. (Dept. of Neurology, Sanjay Gandhi Postgraduate Inst. of Medical Sciences, Lucknow (India)); Gujral, R.B. (Dept. of Radiology, Sanjay Gandhi Postgraduate Inst. of Medical Sciences, Lucknow (India))

    1994-01-01

    We studied 20 patients with intraspinal tuberculosis (TB), to characterise the MRI features of tuberculous meningitis and myelitis. MRI leptomeningitis and intramedullary involvement in 11 patients, intramedullary lesions alone in 5, leptomeningitis alone in 2, and isolated extradural disease in 2. TB leptomeningitis was characterised by loculation of the cerebrospinal fluid (CSF), nerve root thickening and clumping (seen only in the lumbar region) or complete obliteration of the subarachnoid space on unenhanced images. Gd-DTPA-enhanced images proved useful in 6 cases, revealing linear enhancement of the surface of the spinal cord and nerve roots or plaque-like enhancement of the dura-arachnoid mater complex. Intramedullary lesions included tuberculomas (8), cord oedema (5) and cavitation (3). In seven cases of intramedullary tuberculoma multiple lesions with skip areas were seen, without significant cord swelling. One patient had an isolated lesion in the conus medullaris. The lesions were iso- or hypointense on T1-weighted images, iso-, hypo- or hyperintense on T2-weighted images and showed rim or nodular enhancement with contrast medium. (orig.)

  3. Musculoskeletal MRI: dedicated systems

    Energy Technology Data Exchange (ETDEWEB)

    Masciocchi, C.; Barile, A. [Dept. of Radiology, University of L' Aquila (Italy); Satragno, L. [MRI Research Div., Esaote SpA, Genoa (Italy)

    2000-02-01

    The ''dedicated'' MRI units have characteristics of high diagnostic accuracy and lower installation and management costs as compared with whole-body systems. The dedicated MRI units are easy to install. The low weight allows their installation also under unfavorable circumstances. In a dedicated system cost-effectiveness and ease of installation must be accompanied by the capability of providing high-quality images. In our experience, the high number of examinations performed, the most part of which provided with the surgical controls, allowed an accurate evaluation of the diagnostic potentialities of the dedicated magnet. We were not able to perform the examinations in only 3 % of cases due to the physical shape of the patient and the clinical condition of the patient which may hinder the correct positioning of the limb. The overlapping of the diagnostic accuracy of the E-scan and Artoscan units in the study of the lower limbs, compared with whole-body units and surgery, prompted us to exploit the potentialities of the E-Scan in the study of the shoulder. We had a good correlation between E-Scan, whole-body units, and surgical findings, which confirmed the high diagnostic accuracy of the dedicated system. In conclusion, in our experience carried out in the musculoskeletal system, the dedicated magnets showed promising results. Their diagnostic reliability and utility was comparable to that obtained from conventional units operating at higher magnetic fields. (orig.)

  4. Tailgut cysts: MRI findings

    Energy Technology Data Exchange (ETDEWEB)

    Aflalo-Hazan, V.; Rousset, P.; Lewin, M.; Azizi, L. [Hopital Saint Antoine, Department of Radiology, PARIS Cedex 12 (France); Mourra, N. [Hopital Saint Antoine, Department of Pathology, PARIS Cedex 12 (France); Hoeffel, C. [Hopital Robert Debre, Department of Radiology, Reims Cedex (France)

    2008-11-15

    Magnetic resonance imaging (MRI) features of 11 surgically resected pelvic tailgut cysts were analyzed with reference to histopathologic and clinical data. Homogeneity, size, location, signal intensity, appearance and presence of septa and/or nodules and/or peripheral rim and involvement of surrounding structures were studied. Histological examination demonstrated 11 tailgut cysts (TGC), including one infected TGC and one TGC with a component of adenocarcinoma. Lesions (3-8 cm in diameter) were exclusively or partly retrorectal in all cases but one, with an extension down the anal canal in five cases. Lesions were multicystic in all patients but one. On T1-weighted MR images, all cystic lesions contained at least one hyperintense cyst. The peripheral rim of the cystic lesion was regular and non or moderately enhancing in all cases but the two complicated TGC. Nodular peripheral rim and irregular septa were seen in the degenerated TGC. Marked enhancement of the peripheral structures was noted in the two complicated TGC. Pelvic MRI is a valuable tool in the preoperative evaluation of TGC. (orig.)

  5. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available Toggle navigation Test/Treatment Patient Type Screening/Wellness Disease/Condition Safety En Español More Info Images/Videos About Us News Physician ... Magnetic resonance imaging (MRI) is a noninvasive medical test that physicians use to diagnose medical conditions. MRI ...

  6. Postmortem MRI of bladder agenesis

    Energy Technology Data Exchange (ETDEWEB)

    Barber, Brendan R. [St George' s Hospital, Radiology Department, London (United Kingdom); Weber, Martin A. [Great Ormond Street Hospital for Children, Department of Histopathology, London (United Kingdom); Bockenhauer, Detlef [Great Ormond Street Hospital for Children, Department of Nephrology, London (United Kingdom); Hiorns, Melanie P.; McHugh, Kieran [Great Ormond Street Hospital for Children, Radiology Department, London (United Kingdom)

    2011-01-15

    We report a 35-week preterm neonate with bladder agenesis and bilateral dysplastic kidneys. A suprapubic catheter was inadvertently inserted into one of the larger inferior cysts of the left dysplastic kidney. A postmortem MRI scan was performed with the findings being confirmed on autopsy. We are unaware of another postmortem MRI study demonstrating bladder agenesis. (orig.)

  7. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... can help physicians evaluate the structures of the brain and can also provide functional information (fMRI) in ...

  8. Getting an MRI (For Kids)

    Medline Plus

    Full Text Available ... Quizzes Kids' Dictionary of Medical Words En Español What Other Kids Are Reading About Recipes for Kids With Diabetes Can ... Do I Help a Kid Who's Bullied? Getting an MRI (Video) KidsHealth > For Kids > Getting an MRI ( ...

  9. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... zippers and similar metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In ... scanner. top of page How does the procedure work? Unlike ... (CT) scans, MRI does not utilize ionizing radiation. Instead, radiofrequency pulses ...

  10. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... have special pediatric considerations. The teddy bear denotes child-specific content. Related Articles and Media MR Angiography (MRA) Magnetic Resonance, Functional (fMRI) - Brain Head and Neck Cancer Treatment Brain Tumor Treatment Magnetic Resonance Imaging (MRI) ...

  11. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... other internal body structures. MRI does not use ionizing radiation (x-rays). Detailed MR images allow physicians to evaluate various parts of the ... imaging technique that does not involve exposure to ionizing radiation. MRI can ... cases. MR images of the brain and other cranial structures are ...

  12. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... Test/Treatment Patient Type Screening/Wellness Disease/Condition Safety En Español More Info Images/Videos About Us ... absolutely necessary for medical treatment. See the MRI Safety page for more information about pregnancy and MRI. ...

  13. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... contrast for an MRI. If you have a history of kidney disease or liver transplant, it will be necessary to perform a blood test to determine whether the kidneys are ... between cancer tissue and fluid, known as edema . MRI typically ...

  14. MRI Findings In Dengue Encephalitis

    Directory of Open Access Journals (Sweden)

    Ashraf V.V

    2004-01-01

    Full Text Available Neurological manifestations are rare in dengue fever. Two cases with encephalopathy and systemic features of dengue fever with abnormal CSF and MR imaging are reported. Striking MRI finding was bilateral symmetrical thalamic lesions similar to those reported in Japanese encephalitis. This report highlights that MRI findings can be similar in dengue and Japanese encephalitis.

  15. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... structures of the brain and can also provide functional information (fMRI) in selected cases. MR images of ... Articles and Media MR Angiography (MRA) Magnetic Resonance, Functional (fMRI) - Brain Head and Neck Cancer Treatment Brain ...

  16. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam is safe for patients with metal implants, except for a few types. People with the ...

  17. Imaging in Vivo Extracellular pH with a Single Paramagnetic Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agent

    Directory of Open Access Journals (Sweden)

    Guanshu Liu

    2012-01-01

    Full Text Available The measurement of extracellular pH (pHe has potential utility for cancer diagnoses and for assessing the therapeutic effects of pH-dependent therapies. A single magnetic resonance imaging (MRI contrast agent that is detected through paramagnetic chemical exchange saturation transfer (PARACEST was designed to measure tumor pHe throughout the range of physiologic pH and with magnetic resonance saturation powers that are not harmful to a mouse model of cancer. The chemical characterization and modeling of the contrast agent Yb3+-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, 10-o-aminoanilide (Yb-DO3A-oAA suggested that the aryl amine of the agent forms an intramolecular hydrogen bond with a proximal carboxylate ligand, which was essential for generating a practical chemical exchange saturation transfer (CEST effect from an amine. A ratio of CEST effects from the aryl amine and amide was linearly correlated with pH throughout the physiologic pH range. The pH calibration was used to produce a parametric pH map of a subcutaneous flank tumor on a mouse model of MCF-7 mammary carcinoma. Although refinements in the in vivo CEST MRI methodology may improve the accuracy of pHe measurements, this study demonstrated that the PARACEST contrast agent can be used to generate parametric pH maps of in vivo tumors with saturation power levels that are not harmful to a mouse model of cancer.

  18. Is Synthesizing MRI Contrast Useful for Inter-modality Analysis?

    DEFF Research Database (Denmark)

    Iglesias, Juan Eugenio; Konukoglu, Ender; Zikic, Darko

    2013-01-01

    , to what extent they can substitute real acquisitions in the respective analyses is an open question. In this study, we used a synthesis method based on patch matching to test whether synthetic images can be useful in segmentation and inter-modality cross-subject registration of brain MRI. Thirty-nine T1......Availability of multi-modal magnetic resonance imaging (MRI) databases opens up the opportunity to synthesize different MRI contrasts without actually acquiring the images. In theory such synthetic images have the potential to reduce the amount of acquisitions to perform certain analyses. However...... scans with 36 manually labeled structures of interest were used in the registration and segmentation of eight proton density (PD) scans, for which ground truth T1 data were also available. The results show that synthesized T1 contrast can considerably enhance the quality of non-linear registration...

  19. A Technique for Generating Volumetric Cine MRI (VC-MRI)

    Science.gov (United States)

    Harris, Wendy; Ren, Lei; Cai, Jing; Zhang, You; Chang, Zheng; Yin, Fang-Fang

    2016-01-01

    Purpose To develop a technique to generate on-board volumetric-cine MRI (VC-MRI) using patient prior images, motion modeling and on-board 2D-cine MRI. Methods One phase of a 4D-MRI acquired during patient simulation is used as patient prior images. 3 major respiratory deformation patterns of the patient are extracted from 4D-MRI based on principal-component-analysis. The on-board VC-MRI at any instant is considered as a deformation of the prior MRI. The deformation field is represented as a linear combination of the 3 major deformation patterns. The coefficients of the deformation patterns are solved by the data fidelity constraint using the acquired on-board single 2D-cine MRI. The method was evaluated using both XCAT simulation of lung cancer patients and MRI data from four real liver cancer patients. The accuracy of the estimated VC-MRI was quantitatively evaluated using Volume-Percent-Difference(VPD), Center-of-Mass-Shift(COMS), and target tracking errors. Effects of acquisition orientation, region-of-interest(ROI) selection, patient breathing pattern change and noise on the estimation accuracy were also evaluated. Results Image subtraction of ground-truth with estimated on-board VC-MRI shows fewer differences than image subtraction of ground-truth with prior image. Agreement between profiles in the estimated and ground-truth VC-MRI was achieved with less than 6% error for both XCAT and patient data. Among all XCAT scenarios, the VPD between ground-truth and estimated lesion volumes was on average 8.43±1.52% and the COMS was on average 0.93±0.58mm across all time-steps for estimation based on the ROI region in the sagittal cine images. Matching to ROI in the sagittal view achieved better accuracy when there was substantial breathing pattern change. The technique was robust against noise levels up to SNR=20. For patient data, average tracking errors were less than 2 mm in all directions for all patients. Conclusions Preliminary studies demonstrated the

  20. Fast Reference-Based MRI

    CERN Document Server

    Weizman, Lior; Ben-Basaht, Dafna

    2015-01-01

    In many clinical MRI scenarios, existing imaging information can be used to significantly shorten acquisition time or to improve Signal to Noise Ratio (SNR). In some cases, a previously acquired image can serve as a reference image, that may exhibit similarity to the image being acquired. Examples include similarity between adjacent slices in high resolution MRI, similarity between various contrasts in the same scan and similarity between different scans of the same patient. In this paper we present a general framework for utilizing reference images for fast MRI. We take into account that the reference image may exhibit low similarity with the acquired image and develop an iterative weighted approach for reconstruction, which tunes the weights according to the degree of similarity. Experiments demonstrate the performance of the method in three different clinical MRI scenarios: SNR improvement in high resolution brain MRI, utilizing similarity between T2-weighted and fluid-attenuated inversion recovery (FLAIR)...

  1. Visualizing electromagnetic vacuum by MRI

    CERN Document Server

    Chandrashekar, Chandrika S; Chandrashekar, S; Taylor, Erika A; Taylor, Deanne M

    2016-01-01

    Based upon Maxwell's equations, it has long been established that oscillating electromagnetic (EM) fields incident upon a metal surface decay exponentially inside the conductor, leading to a virtual EM vacuum at sufficient depths. Magnetic resonance imaging (MRI) utilizes radiofrequency (r.f.) EM fields to produce images. Here we present the first visualization of an EM vacuum inside a bulk metal strip by MRI, amongst several novel findings. We uncover unexpected MRI intensity patterns arising from two orthogonal pairs of faces of a metal strip, and derive formulae for their intensity ratios. Further, we furnish chemical shift imaging (CSI) results that discriminate different faces (surfaces) of a metal block according to their distinct nuclear magnetic resonance (NMR) chemical shifts, which holds much promise for monitoring surface chemical reactions noninvasively. Bulk metals are ubiquitous, and MRI is a premier noninvasive diagnostic tool. Combining the two, the emerging field of bulk metal MRI can be expe...

  2. On consciousness, resting state fMRI, and neurodynamics.

    Science.gov (United States)

    Lundervold, Arvid

    2010-06-03

    During the last years, functional magnetic resonance imaging (fMRI) of the brain has been introduced as a new tool to measure consciousness, both in a clinical setting and in a basic neurocognitive research. Moreover, advanced mathematical methods and theories have arrived the field of fMRI (e.g. computational neuroimaging), and functional and structural brain connectivity can now be assessed non-invasively. The present work deals with a pluralistic approach to "consciousness'', where we connect theory and tools from three quite different disciplines: (1) philosophy of mind (emergentism and global workspace theory), (2) functional neuroimaging acquisitions, and (3) theory of deterministic and statistical neurodynamics - in particular the Wilson-Cowan model and stochastic resonance. Based on recent experimental and theoretical work, we believe that the study of large-scale neuronal processes (activity fluctuations, state transitions) that goes on in the living human brain while examined with functional MRI during "resting state", can deepen our understanding of graded consciousness in a clinical setting, and clarify the concept of "consiousness" in neurocognitive and neurophilosophy research.

  3. Correlation of MRI T2 mapping sequence with knee pain location in young patients with normal standard MRI.

    Science.gov (United States)

    Dautry, R; Bousson, V; Manelfe, J; Perozziello, A; Boyer, P; Loriaut, Ph; Koch, P; Silvestre, A; Schouman-Claeys, E; Laredo, J D; Dallaudière, B

    2014-01-01

    To assess the correlation of T2 mapping abnormalities to knee pain location, in young adults with normal standard knee MRI at 3.0 Tesla. Twenty-three consecutive patients were included prospectively from September 2011 to April 2012. Inclusion criteria were age under 50 years old, knee pain without surgical history, and normal knee MRI at 3.0 Tesla (sagittal T1-weighted images, and sagittal, axial and coronal proton-density-weighted images with saturation of fat signal). Ten asymptomatic volunteers were also included as a control group. Patients and controls had a cartilage T2 mapping MRI sequence in addition to the standard MRI protocol. Two musculoskeletal radiologists, blinded to the patient/control condition and pain location, independently reviewed the T2 mapping images. T2 values below 40 ms were considered normal. They rated the number of hyaline cartilage lesions and their grade according to an ICRS-like score (inspired by the International Cartilage Research Society score) in each anatomical compartment (medial and lateral femoro-tibial and anterior patello-femoral joints). In addition, the T2 value of the largest lesion was measured. Patient's pain location was classified in the following categories: anterior, lateral, medial and global. T2 mapping findings were compared to pain location, and retrospectively to the initial standard sequences. Sensitivity and specificity were calculated for MRI with T2 mapping according to pain location for each reader. Kappa coefficient was calculated for inter-reader agreement. We used variance analysis in a linear regression to compare T2 values and ICRS-like classification in each compartment. Sensitivity of MRI with T2 mapping, according to the symptomatic compartment, was respectively: 78% and 87% for Reader 1 and Reader 2 and specificity was 70% for both readers. Kappa coefficient for T2 mapping abnormalities location and pain location was good, with a calculated value of 0.64. There was no significant correlation

  4. MRI findings in Hirayama disease

    Directory of Open Access Journals (Sweden)

    Raval Monali

    2010-01-01

    Full Text Available The objective of the study was to study the magnetic resonance imaging (MRI features of Hirayama disease on a 3 Tesla MRI scanner. Nine patients with clinically suspected Hirayama disease were evaluated with neutral position, flexion, contrast-enhanced MRI and fast imaging employing steady-state acquisition (FIESTA sequences. The spectrum of MRI features was evaluated and correlated with the clinical and electromyography findings. MRI findings of localized lower cervical cord atrophy (C5-C7, abnormal curvature, asymmetric cord flattening, loss of attachment of the dorsal dural sac and subjacent laminae in the neutral position, anterior displacement of the dorsal dura on flexion and a prominent epidural space were revealed in all patients on conventional MRI as well as with the dynamic 3D-FIESTA sequence. Intramedullary hyperintensity was seen in four patients on conventional MRI and on the 3D-FIESTA sequence. Flow voids were seen in four patients on conventional MRI sequences and in all patients with the 3D-FIESTA sequence. Contrast enhancement of the epidural component was noted in all the five patients with thoracic extensions. The time taken for conventional and contrast-enhanced MRI was about 30-40 min, while that for the 3D-FIESTA sequence was 6 min. Neutral and flexion position MRI and the 3D-FIESTA sequence compliment each other in displaying the spectrum of findings in Hirayama disease. A flexion study should form an essential part of the screening protocol in patients with suspected Hirayama disease. Newer sequences such as the 3D-FIESTA may help in reducing imaging time and obviating the need for contrast.

  5. Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser.

    Science.gov (United States)

    Milton, S V; Gluskin, E; Arnold, N D; Benson, C; Berg, W; Biedron, S G; Borland, M; Chae, Y C; Dejus, R J; Den Hartog, P K; Deriy, B; Erdmann, M; Eidelman, Y I; Hahne, M W; Huang, Z; Kim, K J; Lewellen, J W; Li, Y; Lumpkin, A H; Makarov, O; Moog, E R; Nassiri, A; Sajaev, V; Soliday, R; Tieman, B J; Trakhtenberg, E M; Travish, G; Vasserman, I B; Vinokurov, N A; Wang, X J; Wiemerslage, G; Yang, B X

    2001-06-15

    Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.

  6. Saturations-based nonlinear controllers with integral term: validation in real-time

    Science.gov (United States)

    Alatorre, A. G.; Castillo, P.; Mondié, S.

    2016-05-01

    Popular saturations-based nonlinear controller usually include proportional and derivative components of the state or output. The fact that in many applications, these components do not suffice to insure the convergence to the desired output values, motivate the addition of an integral term. In this paper, three configurations of nonlinear controllers based on saturation functions are improved with an integral component. The stability of the three algorithms is analysed using the Lyapunov theory. Simulation results validate the proposed control laws when they are applied to nonlinear systems with constant and unknown perturbations. Real-time experiments realised with a quad-rotor aerial vehicle and a hovercraft vehicle show that the proposed scheme can follow autonomously some trajectories, and that it could be robust with respect to delays.

  7. Can Polyphosphate Biochemistry Affect Biological Apatite Saturation?

    Science.gov (United States)

    Omelon, S. J.; Matsuura, N.; Gorelikov, I.; Wynnyckyj, C.; Grynpas, M. D.

    2010-12-01

    Phosphorus (P) is an important and limiting element for life. One strategy for storing ortho phosphates (Pi) is polymerization. Polymerized Pi's (polyphosphates: (PO3-)n: polyPs) serve as a Pi bank, as well as a catiion chelator, energy source, & regulator of responses to stresses in the stationary phase of culture growth and development1. PolyP biochemistry has been investigated in yeasts, bacteria & plants2. Bigeochemical cycling of P includes the condensation of Pi into pyro (P2O7-4), & polyPs, & the release of Pi from these compounds by the hydrolytic degradation of Pi from phosphomonoester bonds. Alkaline phosphatase (ALP) is one of the predominate enzymes for regenerating Pi in aquatic systems3, & it cleaves Pi from polyPs. ALP is also the enzyme associated with apatite biomineralization in vertebrates4. PolyP was proposed to be the ALP substrate in bone mineralization5. Where calcium ions are plentiful in many aquatic environments, there is no requirement for aquatic life to generate Ca-stores. However, terrestrial vertebrates benefit from a bioavailable Ca-store such as apatite. The Pi storage strategy of polymerizing PO4-3 into polyPs dovetails well with Ca-banking, as polyPs sequester Ca, forming a neutral calcium polyphosphate (Ca-polyP: (Ca(PO3)2)n) complex. This neutral complex represents a high total [Ca+2] & [PO4-3], without the threat of inadvertent apatite precipitation, as the free [Ca+2] & [PO4-3], and therefore apatite saturation, are zero. Recent identification of polyP in regions of bone resorption & calcifying cartilage5 suggests that vertebrates may use polyP chemistry to bank Ca+2 and PO4-3. In vitro experiments with nanoparticulate Ca-polyP & ALP were undertaken to determine if carbonated apatite could precipitate from 1M Ca-polyP in Pi-free “physiological fluid” (0.1 M NaCl, 2 mM Ca+2, 0.8 mM Mg+2, pH ~8.0 ±0.5, 37 °C), as this is estimated to generate the [Ca+2] & [PO4-3] required to form the apatite content of bone tissue

  8. Inverse Z-spectrum analysis for spillover-, MT-, and T1 -corrected steady-state pulsed CEST-MRI--application to pH-weighted MRI of acute stroke.

    Science.gov (United States)

    Zaiss, Moritz; Xu, Junzhong; Goerke, Steffen; Khan, Imad S; Singer, Robert J; Gore, John C; Gochberg, Daniel F; Bachert, Peter

    2014-03-01

    Endogenous chemical exchange saturation transfer (CEST) effects are always diluted by competing effects, such as direct water proton saturation (spillover) and semi-solid macromolecular magnetization transfer (MT). This leads to unwanted T2 and MT signal contributions that lessen the CEST signal specificity to the underlying biochemical exchange processes. A spillover correction is of special interest for clinical static field strengths and protons resonating near the water peak. This is the case for all endogenous CEST agents, such as amide proton transfer, -OH-CEST of glycosaminoglycans, glucose or myo-inositol, and amine exchange of creatine or glutamate. All CEST effects also appear to be scaled by the T1 relaxation time of water, as they are mediated by the water pool. This forms the motivation for simple metrics that correct the CEST signal. Based on eigenspace theory, we propose a novel magnetization transfer ratio (MTRRex ), employing the inverse Z-spectrum, which eliminates spillover and semi-solid MT effects. This metric can be simply related to Rex , the exchange-dependent relaxation rate in the rotating frame, and ka , the inherent exchange rate. Furthermore, it can be scaled by the duty cycle, allowing for simple translation to clinical protocols. For verification, the amine proton exchange of creatine in solutions with different agar concentrations was studied experimentally at a clinical field strength of 3 T, where spillover effects are large. We demonstrate that spillover can be properly corrected and that quantitative evaluation of pH and creatine concentration is possible. This proves that MTRRex is a quantitative and biophysically specific CEST-MRI metric. Applied to acute stroke induced in rat brain, the corrected CEST signal shows significantly higher contrast between the stroke area and normal tissue, as well as less B1 dependence, than conventional approaches. Copyright © 2014 John Wiley & Sons, Ltd.

  9. Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

    Science.gov (United States)

    Wang, Xiujuan; Hutchinson, Deborah R.; Wu, Shiguo; Yang, Shengxiong; Guo, Yiqun

    2011-01-01

    Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.

  10. MRI in cerebellar hypoplasia

    Energy Technology Data Exchange (ETDEWEB)

    DeSouza, N. [Guy`s Hospital, London (United Kingdom). Dept. of Magnetic Resonance, Div. of Radiological Sciences; Chaudhuri, R. [Guy`s Hospital, London (United Kingdom). Dept. of Magnetic Resonance, Div. of Radiological Sciences; Bingham, J. [Guy`s Hospital, London (United Kingdom). Dept. of Magnetic Resonance, Div. of Radiological Sciences; Cox, T. [Guy`s Hospital, London (United Kingdom). Dept. of Magnetic Resonance, Div. of Radiological Sciences

    1994-02-01

    Cerebellar hypoplasia may present with a wide variety of neurological and systemic features, ranging from aplasia causing neonatal death to mild hypoplasia in an asymptomatic adult. MRI clearly documents the size of the cerebellum and any associated abnormalities. We describe 7 cases of cerebellar hypoplasia of varying aetiology - 3 inherited, 2 associated with spinal dysraphism, 1 with Joubert`s syndrome and 1 with pontine agenesis, probably as a result of basilar artery infarction in utero. T1- and T2-weighted images were obtained in each case and gadolinium-DTPA was administered in one. Associated features such as a Chiari malformation (2 cases), brain stem hypoplasia (2 cases), Dandy-Walker cyst and pachygyria (3 cases) and spinal dysraphism (2 cases) were clearly identified. Accurate documentation of these appearances assists in genetic counselling. (orig.)

  11. Measuring response saturation in human MT and MST as a function of motion density.

    Science.gov (United States)

    Durant, Szonya; Furlan, Michele

    2014-07-24

    The human brain areas MT and MST have been studied in great detail using fMRI with regards to their motion processing properties; however, to what extent this corresponds with single cell recordings remains to be fully described. Average response over human MT+ has been shown to increase linearly with motion coherence, similar to single cell responses. In response to motion density some single cell data however suggest a rapid saturation. We ask how the combination of these responses is reflected in the population response. We measured the blood oxygen level dependent (BOLD) response function of MT and MST using a motion density signal, comparing with area V1. We used spatially fixed apertures containing motion stimuli to manipulate the area covered by motion. We found that MT and MST responded above baseline to a very minimal amount of motion and showed a rather flat response to motion density, indicative of saturation. We discuss how this may be related to the size of the receptive fields and inhibitory interactions, although necessarily residual attention effects also need to be considered. We then compared different types of motion and found no difference between coherent and random motion at any motion density, suggesting that when combining response over several motion stimuli covering the visual field, a linear relationship of MT and MST population response as a function of motion coherence might not hold. © 2014 ARVO.

  12. Prioritized Control Allocation for Quadrotors Subject to Saturation

    NARCIS (Netherlands)

    Smeur, E.J.J.; de Wagter, C.; J.-M. Moschetta G. Hattenberger, H. de Plinval

    2017-01-01

    This paper deals with the problem of actuator saturation for INDI (Incremental Nonlinear Dynamic Inversion) controlled flying vehicles. The primary problem that arises from actuator saturation for quadrotors, is that of arbitrary control objective realization. We have integrated the weighted least

  13. Polar spots and stellar spindown: is dynamo saturation needed?

    NARCIS (Netherlands)

    Solanki, S. K.; Motamen, S.; Keppens, R.

    1997-01-01

    Dynamo saturation is often invoked when calculating the rotational evolution of cool stars. At rapid rotation rates a saturated dynamo reduces the angular momentum carried away by the stellar wind. This, in turn, may explain the high rotation rates present in the distribution of rotation periods in

  14. Polar spots and stellar spindown: Is dynamo saturation needed?

    NARCIS (Netherlands)

    Solanki, S. K.; Motamen, S.; Keppens, R.

    1997-01-01

    Dynamo saturation is often invoked when calculating the rotational evolution of cool stars. At rapid rotation rates a saturated dynamo reduces the angular momentum carried away by the stellar wind. This, in turn, may explain the high rotation rates present in the distribution of rotation periods in

  15. Gain characteristics of a saturated fiber optic parametric amplifier

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Lorenzen, Michael Rodas; Noordegraaf, Danny

    2008-01-01

    In this work we discuss saturation performance of a fiber optic parametric amplifier. A simple numerical model is described and applied to specific cases. A system experiment using a saturated amplifier illustrates a 4 dB improvement in required signal to noise ratio for a fixed bit error ratio....

  16. Renal vein oxygen saturation in renal artery stenosis

    DEFF Research Database (Denmark)

    Nielsen, K; Rehling, M; Henriksen, Jens Henrik Sahl

    1992-01-01

    Renal vein oxygen-saturation was measured in 56 patients with arterial hypertension and unilateral stenosis or occlusion of the renal artery. Oxygen-saturation in blood from the ischaemic kidney (84.4%, range 73-93%) was significantly higher than that from the 'normal' contralateral kidney (81...

  17. Comparison of empirical models and laboratory saturated hydraulic ...

    African Journals Online (AJOL)

    Numerous methods for estimating soil saturated hydraulic conductivity exist, which range from direct measurement in the laboratory to models that use only basic soil properties. A study was conducted to compare laboratory saturated hydraulic conductivity (Ksat) measurement and that estimated from empirical models.

  18. Stability and stabilization of linear systems with saturating actuators

    CERN Document Server

    Tarbouriech, Sophie; Gomes da Silva Jr, João Manoel; Queinnec, Isabelle

    2011-01-01

    Gives the reader an in-depth understanding of the phenomena caused by the more-or-less ubiquitous problem of actuator saturation. Proposes methods and algorithms designed to avoid, manage or overcome the effects of actuator saturation. Uses a state-space approach to ensure local and global stability of the systems considered. Compilation of fifteen years' worth of research results.

  19. Excitable solitons in a semiconductor laser with a saturable absorber

    Science.gov (United States)

    Turconi, Margherita; Prati, Franco; Barland, Stéphane; Tissoni, Giovanna

    2015-11-01

    Self-pulsing cavity solitons may exist in a semiconductor laser with an intracavity saturable absorber. They show locally the passive Q -switching behavior that is typical of lasers with saturable absorbers in the plane-wave approximation. Here we show that excitable cavity solitons are also possible in a suitable parameter range and characterize their excitable dynamics and properties.

  20. Saturated hydraulic conductivity values of some forest soils of ...

    African Journals Online (AJOL)

    A simple falling-head method is presented for the laboratory determination of saturated hydraulic conductivity of some forest soils of Ghana. Using the procedure, it was found that saturated hydraulic conductivity was positively and negatively correlated with sand content and clay content, respectively, both at P = 0.05 level.